On 7/19/2017 3:20 PM, Bob F wrote:
On 7/19/2017 11:56 AM, Mad Roger wrote:
On Wed, 19 Jul 2017 11:38:24 -0700 (PDT),
trader_4 wrote:

How many people looking at a stylish SUV think that those wheels look
like they steer better?

Maybe I'm wrong that people try to replicate an image of speed and
handling
(e.g., why do people put M3 badges on a non-M3 bimmer then?).

Anyway, I just want to know what the performance impact is of a larger
diameter change of one inch.

This Car and Driver article tries to answer the question:
Effects of Upsized Wheels and Tires Tested
http://www.caranddriver.com/features...d-tires-tested


"What¢s immediately apparent from the results is that as the
wheel-and-tire
packages get larger and heavier, acceleration and fuel economy suffer.
Neither is a huge surprise, but we measured a 10-percent drop in fuel
economy and a four-percent degradation in 0-to-60-mph acceleration
from the
15s to the 19s"


Without adjusting the gearing? Clearly, they are operating the engine
way out of it's efficiency range. Why would anyone do this?



Given EPA standards the car maufacturer is going to gear properly. Joe
Gearhead will only think of how it looks.

On Wed, 19 Jul 2017 12:45:50 -0700 (PDT),
trader_4 wrote:

You keep saying "our intuition" when it's clear that both Bob F and
I don't agree with your intuition.

That was a mistake on my part to intuit what you intuit.
I can't possibly know what your intuition is.

I just want reliable facts anyway so your or my intuition doesn't matter.

(My intuition, for example, is that women with tattoos and who smoke give
better blow jobs - but that's just not always correct. Ask my wife.)

Anyways, I've gone through the first twenty five pages of multiple google
searches seeking reliable data and there's not a single reference I can
find that says you'll generally get better gas mileage.

All the reliable references already listed in this thread say that "it
depends" on a number of factors, the most important of which is the torque
curve of the vehicle, and the resulting contact patch width but also the
rubber itself matters greatly.

For those who consider Car Talk reliable, here's what they say.
http://www.cartalk.com/blogs/tom-ray...ter-new-pickup

"TOM: You'll get better mileage on the highway [with smaller wheels]."
"RAY: Smaller wheel-tire combinations provide better mileage (city and
highway), better acceleration and a quieter, more comfortable ride."
"TOM: And the extra weight of the larger wheels ... cuts into your
acceleration and fuel economy."

On Wed, 19 Jul 2017 11:22:48 -0700 (PDT),
trader_4 wrote:

That's crazy! Where on earth did that come from. 1" diameter increase
would only cause that change if you started with 4" O.D. tires.

Yeah, that number seems suspect to me too.

I made a mistake in quoting the loss of torque due to a one inch increase
in diameter. The 25% loss in torque was due to four inches in diameter.

That means the loss in torque at the contact patch is less than that for
one inch increase in diameter.

It's still a loss in torque though, which itself isn't doing the fuel
mileage any favors. The reliable reports (Cooper Tire for example) said
that the torque loss is the biggest factor where they said "most cars"
would see a negative impact from tires (unless they had torque to spare).

Here's a summary of the Car and Driver article by someone not me.
http://www.dunntire.com/blog/Does-ti...ct-gas-mileage
"What¢s immediately apparent from the results is that as the wheel-and-tire
packages get larger and heavier, acceleration and fuel economy suffer.
Specifically, [Car and Driver] cited a '10-percent drop in fuel economy'
from the 15s to the 19s."

And I don't believe less torque translates into lower fuel economy either.
Yes, it will accelerate slower with a larger diameter wheel, but that
just means you have less torque applied over a longer period. It's
not torque, it's energy that you need to look at.

Nobody can find a reliable reference which says anything better for larger
diameters other than saying that "most cars" will not find any increase in
gas mileage but that the torque curve is everything so "some cars" may get
better gas mileage if they have torque to spare.

Almost all reliable sources said there are many factors but the one factor
of torque loss is in all the reliable sources.

On Wed, 19 Jul 2017 13:56:02 -0600,
rbowman wrote:

Many manufacturers use low rolling resistance tires as OEM equipment to
improve their CAFE numbers. One of the best is the Bridgestone B381
which has a 65 profile. Low profile is usually considered to be 50 and
under.

The Consumer Reports reference I already quoted said there were a few miles
per gallon to be had from changing the tire and nothing else (not the size
or anything else but the tire).

So it's more complex, but no reliable source yet says that most cars will
benefit in fuel economy from larger diameters alone, and in fact, all the
reliable sources say the opposite.

Here is another source from Dunn Tire.
Does tire size affect gas mileage?
http://www.dunntire.com/blog/Does-ti...ct-gas-mileage

That source talked about truck tires when it said
"It is probably not worth switching to smaller tires, since any gains in
fuel economy would be offset by the added cost of re-gearing to keep your
engine operating in its most efficient rpm range. Remember, power and
economy are affected by transmission, drive axle ratios and tire size
(revolution per mile). Change one, and you throw the equation off. With
today¢s new tires, there is virtually no difference in mpg due to tire
size."

On Wed, 19 Jul 2017 07:36:14 -0400, "dadiOH" wrote:


"Mad Roger" wrote in message
news
What's the *performance* difference between 15 inch, 16 inch and 17 inch
tires (all else being equal)?

Let's say that the stock wheel is 16 inch and let's ignore sheer looks,
and
the fact the speedometer will read differently, and let's ignore obvious
non-performance wheel-well fitment issue since they're obviously not
performance changes.

What *performance* changes will the one inch larger or smaller tire cause?

Basically, I'm wondering why people almost universally want larger wheels,
where all I'm asking about are what the performance tradeoffs are.

Bigger wheel = less gasoline for a given distance and less tire wear.

Not necessarily less gasoline if it makes the engine work harder
(which it will) by enough to counteract those savings (which it often
will, under some cercumstances of speed and driving conditions)

On Wed, 19 Jul 2017 11:45:09 -0700 (PDT),
trader_4 wrote:

I didn't say that either, in fact I said the opposite. You're looking
at torque, not energy expended. If I lift a 100 lb rock with a 2ft
lever or with a 10 ft lever, one involves 5 times the torque, but
the energy used is exactly the same.

I'm not looking to argue what he said and she said so I won't say what you
said. I'll just keep looking for the answer but it seems pretty universal
what the answer turned out to be (which wasn't what I originally thought).

This article "The Drawbacks to Bigger Wheels"
https://www.autotrader.com/car-shopp...-wheels-246039
concludes by saying
"there's undoubtedly a negative correlation between [larger] wheel size and
fuel economy."

On Wed, 19 Jul 2017 15:51:22 -0000 (UTC), Mad Roger
wrote:

On Wed, 19 Jul 2017 07:36:14 -0400,
dadiOH wrote:

Bigger wheel = less gasoline for a given distance and less tire wear.

I would intuitively agree with you but the two referenced articles do not
agree with our intuition.

Combined, the two articles said (for a one-inch difference)...
+ The engine delivers ~25% less driving force to the wheel contact patch
+ Which results in a decrease in acceleration & decrease in fuel economy
+ And there will be a decrease in handling (mostly in cornering)
+ And that unsprung weight goes up appreciably
+ In addition to tire air "cushioning" being reduced
+ While the overall vehicle suspension remains at the same ride height
???
If the tire diameter is increased by one inch to cause the reduction
in tractive force, the suspension hight CAN NOT remain unchainged
If the tire hight /diameter is increased, there is MORE cushioning if
the rim size does not change, and the same if the rim and tire
diameters change.
The unsprung weight can go up or down, depending on the weight of the
tire and the rim.


In other words, you can't take points from 2 different articles
discussing 2 different things and put them together and draw these
kinds of conclusions.

On Wed, 19 Jul 2017 13:42:19 -0600, rbowman
wrote:

On 07/19/2017 11:42 AM, Mad Roger wrote:
Likewise a wing in the rear has a genesis in actual aeordynamic theory so I
understand that people want the look of a fast car (although at 60mph, a
wing is probably just for looks).

I owned a '60 Plymouth which was the bitter end of the fin craze.
Plymouth even referred to them as stabilizers:

http://www.allpar.com/history/plymouth/1960.html

I never managed to get the car up past 110 and didn't notice any more
stabilizing effect than my '65 Dodge which was back to the basic 3 box
model:

https://en.wikipedia.org/wiki/Dodge_...5.E2.80.931967

Style is style. I did go to an outlaw kart race a couple of weeks ago
and found out the real use for the wings -- when they roll the wind up
on their side with the wing preventing them from going over completely.




These guys just use the " wings " for advertising .. :-)

https://www.youtube.com/watch?v=UDqr...ature=youtu.be

I remember the super-modified races at Flamborough S. Ontario
in the early 1970's .. their brakes were glowing red at the end of
the feature ! I don't know how they avoided fires ?
The cars were akin to go-carts - but with big modified V8 engines.

Maybe MadRoger could scientifically analyse the wheels -
- different sizes - IIRC -
- left vs right due to the banked corners ! :-)

John T.

On Wed, 19 Jul 2017 16:53:06 -0000 (UTC), Mad Roger
wrote:

On Wed, 19 Jul 2017 12:17:36 -0400,
Frank wrote:

I found it interesting and first sentence says it, "They look cool."

I agree that people do things for looks alone, but what is strange is that
there doesn't seem to be a single beneficial performance impact of an
overall larger diameter "tire-and-wheel assembly".

I wasn't expecting huge performance gains, but I would have expected at
least one or two benefits - and not all negatives based on the two articles
noted.

If the diameter of the wheel and tire assembly increases by one inch
overall due to the one-inch increase in rim size - and assuming everything
else is kept equal in materials and aspect ratio and tread width - then the
two articles stated...
+ The engine delivers ~25% less driving force to the wheel contact patch
+ Which results in a decrease in acceleration
+ And which decrease in fuel economy (presumably at all times)
+ And unsprung weight goes up by a few pounds

Depends on the rims. The 16 inch torque thrust rims on my ranger weigh
less than either the 14 inch "deerfoot" alloys from the factory OR the
stock steel wheels.Yess, the 235/70 LT tires DO weigh more than the
205/75 passenger tires that came on the truck

The main astounding number is the fact the torque felt at the wheels is
astoundingly less for a single inch in overall diameter change.

Presumably that torque loss happens at all speeds (why would it not?) so
that denies us the one intuitive performance advantage of highway MPG.

That depends ENTIRELY on the particular vehicle (some will get better
mileage, some worse - generally the higher powered cars gain, the
lower powered loose) and how the car is driven (usually an improvement
in "sane" steady speed generally level driving, and generally worse in
city or stop/start driving, or "leadfooting" on the highway)

On Wed, 19 Jul 2017 13:36:23 -0400, wrote:



I agree that people do things for looks alone, but what is strange is that
there doesn't seem to be a single beneficial performance impact of an
overall larger diameter "tire-and-wheel assembly".
I wasn't expecting huge performance gains, but I would have expected at
least one or two benefits - and not all negatives based on the two articles
noted.



I would tend to look at the drivers who over-size their wheels
and conclude that it is _not strange at all_ that the mods
are based solely on image ..
John T.
I'll admit putting the 16 inch torque thrusts on my Ranger was
"mostly" for looks - the 14 inchers didn't look like they belonged in
the large wheel openings, particularly with the higher 4700 gvwr
suspension the truck came with ( it sits about the same as a 4X4), and
the rather rare 16 inchers became available at a good price - - -

On Wed, 19 Jul 2017 18:22:12 +0000 (UTC), Roy Tremblay
wrote:

Bob F actually wrote:

+ The engine delivers ~25% less driving force to the wheel contact patch

That's crazy! Where on earth did that come from. 1" diameter increase
would only cause that change if you started with 4" O.D. tires.

Maybe I read the article wrong that was referenced by Ed Pawlowski?
https://www.carthrottle.com/post/how...t-performance/


Low profile tires compensate for the wheel diameter increase, so no
increase in tire diameter occurs, and no torque loss should occur.

+ Which results in a decrease in acceleration
+ And which decrease in fuel economy (presumably at all times)
It should increase economy. Just like driving in a high gear does.

I understand your intuition, which is the same intuition we all have but if
it's true what that article from Ed says, then 25% less torque at the
contact patch means 25% less torque to combat increased wind resistance at
highway speeds.

That means, in the words of the article, the engine has to 'work harder' to
combat that wind resistance.

You tell me how making the engine work (presumably a lot) harder increases
fuel efficiency.

My understanding is that low profile tires are being used because they
have lower rolling friction - the rubber is flexing less, so there is
less loss to heating the tire.

Neither of the two articles mentioned that factor.

And unsprung weight goes up by a few pounds

The main astounding number is the fact the torque felt at the wheels is
astoundingly less for a single inch in overall diameter change.

Yes, it is astounding. In fact, I would suggest it is unbelievable.

That's a fair assessment since 25% less torque for a one-inch increase in
diameter is astounding.

It CAN be true though at certain speeds, with certain engines, because
you drop the RPM of the engine, and if that drop gets the engine "off
the cam" the torque output of the engine suffers , in some cases a
WHOLE LOT.

Can you take a look at the article to see if I did my math wrong?
https://www.carthrottle.com/post/how...t-performance/

360 Newtons is 78% of 460 Newtons.
460 Newtons is 128% of 360 Newtons.

That's roughly 1/4 if my math is right.
(I never know which direction to quote but both end up being about 1/4.)

I agree that people do things for looks alone, but what is strange is that
there doesn't seem to be a single beneficial performance impact of an
overall larger diameter "tire-and-wheel assembly".
I wasn't expecting huge performance gains, but I would have expected at
least one or two benefits - and not all negatives based on the two articles
noted.



I would tend to look at the drivers who over-size their wheels
and conclude that it is _not strange at all_ that the mods
are based solely on image ..
John T.


I'll admit putting the 16 inch torque thrusts on my Ranger was
"mostly" for looks - the 14 inchers didn't look like they belonged in
the large wheel openings, particularly with the higher 4700 gvwr
suspension the truck came with ( it sits about the same as a 4X4), and
the rather rare 16 inchers became available at a good price - - -


Cheap old motorhead farts notwithstanding ..
When I can't avoid visiting the city - I enjoy watching
the Kids with their lowered cars trying to go
into/out of a driveway ... duh. Really ?
At what point does reality kick in ?
John T.

On Wednesday, July 19, 2017 at 5:07:22 PM UTC-4, Mad Roger wrote:
On Wed, 19 Jul 2017 11:22:48 -0700 (PDT),
trader_4 wrote:

That's crazy! Where on earth did that come from. 1" diameter increase
would only cause that change if you started with 4" O.D. tires.

Yeah, that number seems suspect to me too.

I made a mistake in quoting the loss of torque due to a one inch increase
in diameter. The 25% loss in torque was due to four inches in diameter.

That means the loss in torque at the contact patch is less than that for
one inch increase in diameter.

It's still a loss in torque though, which itself isn't doing the fuel
mileage any favors.

Again, you're still conflating torque with energy.

On Wed, 19 Jul 2017 18:56:18 -0000 (UTC), Mad Roger
wrote:

On Wed, 19 Jul 2017 11:38:24 -0700 (PDT),
trader_4 wrote:

How many people looking at a stylish SUV think that those wheels look
like they steer better?

Maybe I'm wrong that people try to replicate an image of speed and handling
(e.g., why do people put M3 badges on a non-M3 bimmer then?).

Anyway, I just want to know what the performance impact is of a larger
diameter change of one inch.

This Car and Driver article tries to answer the question:
Effects of Upsized Wheels and Tires Tested
http://www.caranddriver.com/features...d-tires-tested

"What¢s immediately apparent from the results is that as the wheel-and-tire
packages get larger and heavier, acceleration and fuel economy suffer.
Neither is a huge surprise, but we measured a 10-percent drop in fuel
economy and a four-percent degradation in 0-to-60-mph acceleration from the
15s to the 19s"
see
http://www.therangerstation.com/foru...dex.php?n=2183 for
what my Ranger looks like with the "big boots" on.
If I drive very conservatively I CAN get a bit better mileage than
with the original small tires, but generally speaking, in normal
driving there is little if any improvement -and around town, it is
slightly worse. The truck works harder every time it starts from a
stop or accellerates at low speed. I'm willing to put up with that on
a 21 year old truck with about 350000km on it, to have the "look" I
wanted. It is not a "performance" look - - -

On Wed, 19 Jul 2017 17:30:15 -0400,
wrote:

If the tire diameter is increased by one inch to cause the reduction
in tractive force, the suspension hight CAN NOT remain unchainged
If the tire hight /diameter is increased, there is MORE cushioning if
the rim size does not change, and the same if the rim and tire
diameters change.
The unsprung weight can go up or down, depending on the weight of the
tire and the rim.


In other words, you can't take points from 2 different articles
discussing 2 different things and put them together and draw these
kinds of conclusions.

I've read basically a dozen seemingly reliable articles where you are
correct that it's hard to impossible to cross reference their claims.

However, almost every article maintained three key concepts, which are the
takewaways.

+ You probably will not get better mileage with larger overall diameters
+ But, there are so many factors involved, that you'd have to take all of
them into account to be sure
+ Where the biggest (but not only) factor is how much spare torque you have
+ and the next biggest is the width of the contact patch
+ but plenty of other factors play a role.

On Wed, 19 Jul 2017 17:48:13 -0400,
wrote:

Depends on the rims. The 16 inch torque thrust rims on my ranger weigh
less than either the 14 inch "deerfoot" alloys from the factory OR the
stock steel wheels.Yess, the 235/70 LT tires DO weigh more than the
205/75 passenger tires that came on the truck

Of course you can put carbon fiber rims on to replace oem steel rims and
then one can argue that the "larger" carbon-fiber rims weigh less - but
apples to apples - if you change the diameter upward using the same
material rims, the weight should always go up.

However, in the articles I read, I wasn't sure if the weight would always
go up if you kept the diameter the same, and only increased the rim
diameter, since you're essentially replacing rubber with steel.

Does anyone know if, apples to apples, you increase a rim by one inch,
whether the decrease in sidewall rubber compensates enough to counteract
the gain in rim weight?

That depends ENTIRELY on the particular vehicle (some will get better
mileage, some worse - generally the higher powered cars gain, the
lower powered loose) and how the car is driven (usually an improvement
in "sane" steady speed generally level driving, and generally worse in
city or stop/start driving, or "leadfooting" on the highway)

Apparently this is an age-old argument sort of like the "what oil" or "blue
or green coolant" arguments that shadetree mechanics always seem to have an
opinion on that isn't based in any science.

It seems from most of the referenced articles that, realistically, there's
no change in gas mileage for an inch change in diameter simply because of
all the other factors involved in the real world.

However, if it was truly an apples to apples comparison, with only the one
inch diameter gain, and the tire not compensated for in overall size, then
the torque factor kicks in as the most important, with only cars with spare
torque faring well - the rest faring poorly.

That's what the references said anyway.

On Wed, 19 Jul 2017 15:27:22 -0700 (PDT),
trader_4 wrote:

It's still a loss in torque though, which itself isn't doing the fuel
mileage any favors.

Again, you're still conflating torque with energy.

Not one reference shows an increase in mileage other than stating that, in
"some cars" the torque curve will be put in a better spot but "most cars"
won't.

The reality is that it seems the variables I tried to keep out of the
original question (for example tire width, tread pattern, rubber material,
inflation pressure, unsprung weight, etc.) can make more of a difference
than does the larger diameter tire.

On Wed, 19 Jul 2017 18:06:55 -0400,
wrote:

It CAN be true though at certain speeds, with certain engines, because
you drop the RPM of the engine, and if that drop gets the engine "off
the cam" the torque output of the engine suffers , in some cases a
WHOLE LOT.

It seems that the torque curve is almost everything when it comes to adding
inches to the diameter of the tire and wheel assembly.

Without knowing the torque curve, there's no way to predict the result, but
most accounts I referenced said that your chances are greater that you'll
lose mileage than you'll gain it.

But, everything depends on the variables, which I tried to remove in the
original question - but - they return with a vengeance because the
variables determine whether or not you gain mileage - not the diameter of
the end result.

On Wed, 19 Jul 2017 19:20:49 -0400,
wrote:

If I drive very conservatively I CAN get a bit better mileage than
with the original small tires, but generally speaking, in normal
driving there is little if any improvement -and around town, it is
slightly worse. The truck works harder every time it starts from a
stop or accellerates at low speed. I'm willing to put up with that on
a 21 year old truck with about 350000km on it, to have the "look" I
wanted. It is not a "performance" look - -

I'm just curious how close do you think you can get to "accurate" gas
mileage calculations using the classic odometer plus fill it up to guess at
the gallons used method?

I've read that nobody can accurately get the sig figs closer than +- 1 mpg,
despite the fact that most people I've seen do it try to calculate it down
to the tenth or even hundredth of a gallon, which, even for computers, is
impossible given there are no controls.

So 20mpg is really from 19mpg to 21mpg, which makes calculation difficult
(when I was looking up the wheel size stuff earlier today, Consumer Reports
said as much so that's why I'm curious how close you think you can get to a
repeatably precise figure (yes, both repeatable, and precise).

On 7/19/2017 2:07 PM, Mad Roger wrote:
On Wed, 19 Jul 2017 11:22:48 -0700 (PDT),
trader_4 wrote:

That's crazy! Where on earth did that come from. 1" diameter increase
would only cause that change if you started with 4" O.D. tires.

Yeah, that number seems suspect to me too.

I made a mistake in quoting the loss of torque due to a one inch increase
in diameter. The 25% loss in torque was due to four inches in diameter.

That means the loss in torque at the contact patch is less than that for
one inch increase in diameter.

It's still a loss in torque though, which itself isn't doing the fuel
mileage any favors. The reliable reports (Cooper Tire for example) said
that the torque loss is the biggest factor where they said "most cars"
would see a negative impact from tires (unless they had torque to spare).

Here's a summary of the Car and Driver article by someone not me.
http://www.dunntire.com/blog/Does-ti...ct-gas-mileage
"What¢s immediately apparent from the results is that as the wheel-and-tire
packages get larger and heavier, acceleration and fuel economy suffer.
Specifically, [Car and Driver] cited a '10-percent drop in fuel economy'
from the 15s to the 19s."

And I don't believe less torque translates into lower fuel economy either.
Yes, it will accelerate slower with a larger diameter wheel, but that
just means you have less torque applied over a longer period. It's
not torque, it's energy that you need to look at.

Nobody can find a reliable reference which says anything better for larger
diameters other than saying that "most cars" will not find any increase in
gas mileage but that the torque curve is everything so "some cars" may get
better gas mileage if they have torque to spare.

Almost all reliable sources said there are many factors but the one factor
of torque loss is in all the reliable sources.


The torque loss is defined by the physics of that change. The mileage
resulting is determined by the characteristics of the vehicle, engine
and gearing.

On Thu, 20 Jul 2017 01:45:15 -0000 (UTC), Mad Roger
wrote:

On Wed, 19 Jul 2017 17:48:13 -0400,
wrote:

Depends on the rims. The 16 inch torque thrust rims on my ranger weigh
less than either the 14 inch "deerfoot" alloys from the factory OR the
stock steel wheels.Yess, the 235/70 LT tires DO weigh more than the
205/75 passenger tires that came on the truck

Of course you can put carbon fiber rims on to replace oem steel rims and
then one can argue that the "larger" carbon-fiber rims weigh less - but
apples to apples - if you change the diameter upward using the same
material rims, the weight should always go up.
Not necessarily - a 10 spoke alloy rim will weigh less than the
typical 5 spoke, because there is less aluminum there. Also, a rim
with more open space wighs less than one with more - to the point my
16 inch torque thrusts weigh less than my 14 inch deerfoots.

However, in the articles I read, I wasn't sure if the weight would always
go up if you kept the diameter the same, and only increased the rim
diameter, since you're essentially replacing rubber with steel.
Usually aluminum -

Does anyone know if, apples to apples, you increase a rim by one inch,
whether the decrease in sidewall rubber compensates enough to counteract
the gain in rim weight?
Depends on the tire. With an LT tire, likely. With a "performance"
passenger car tire, likely not

That depends ENTIRELY on the particular vehicle (some will get better
mileage, some worse - generally the higher powered cars gain, the
lower powered loose) and how the car is driven (usually an improvement
in "sane" steady speed generally level driving, and generally worse in
city or stop/start driving, or "leadfooting" on the highway)

Apparently this is an age-old argument sort of like the "what oil" or "blue
or green coolant" arguments that shadetree mechanics always seem to have an
opinion on that isn't based in any science.

It seems from most of the referenced articles that, realistically, there's
no change in gas mileage for an inch change in diameter simply because of
all the other factors involved in the real world.
With one inch, likely no net loss - with 3 or 4, almost definitely in
city driving.

However, if it was truly an apples to apples comparison, with only the one
inch diameter gain, and the tire not compensated for in overall size, then
the torque factor kicks in as the most important, with only cars with spare
torque faring well - the rest faring poorly.

That's what the references said anyway.

On Thu, 20 Jul 2017 01:45:16 -0000 (UTC), Mad Roger
wrote:

On Wed, 19 Jul 2017 15:27:22 -0700 (PDT),
trader_4 wrote:

It's still a loss in torque though, which itself isn't doing the fuel
mileage any favors.

Again, you're still conflating torque with energy.

Not one reference shows an increase in mileage other than stating that, in
"some cars" the torque curve will be put in a better spot but "most cars"
won't.

The reality is that it seems the variables I tried to keep out of the
original question (for example tire width, tread pattern, rubber material,
inflation pressure, unsprung weight, etc.) can make more of a difference
than does the larger diameter tire.
Don't bother arguing with Trader - he's CLUELESS

On Thu, 20 Jul 2017 01:45:17 -0000 (UTC), Mad Roger
wrote:

On Wed, 19 Jul 2017 18:06:55 -0400,
wrote:

It CAN be true though at certain speeds, with certain engines, because
you drop the RPM of the engine, and if that drop gets the engine "off
the cam" the torque output of the engine suffers , in some cases a
WHOLE LOT.

It seems that the torque curve is almost everything when it comes to adding
inches to the diameter of the tire and wheel assembly.

Without knowing the torque curve, there's no way to predict the result, but
most accounts I referenced said that your chances are greater that you'll
lose mileage than you'll gain it.

But, everything depends on the variables, which I tried to remove in the
original question - but - they return with a vengeance because the
variables determine whether or not you gain mileage - not the diameter of
the end result.
You need to know that vehicles were often available with several
different optional gear ratios. If it had a hign numeric rear end,
like a 4.11 , you could gain milage with bigger tires - get the same
mileage as sat 3.55 gears - or mabee 3.23. Buying 3.23 gears and then
putting big tires on it generally would hurt mileage

On my Ranger, with 3.55 gears from rhe factory and they come as high
as a 3.08 and as low as a 4.56. The bigger wheel is still not as high
(effectively) as a 3.08 with the small wheels (would require a 15%
oversize) I upsized 9% - so 3.25 woth the snows - a little less on the
summer tires - 3.31 equivalent

On Thu, 20 Jul 2017 01:45:19 -0000 (UTC), Mad Roger
wrote:

On Wed, 19 Jul 2017 19:20:49 -0400,
wrote:

If I drive very conservatively I CAN get a bit better mileage than
with the original small tires, but generally speaking, in normal
driving there is little if any improvement -and around town, it is
slightly worse. The truck works harder every time it starts from a
stop or accellerates at low speed. I'm willing to put up with that on
a 21 year old truck with about 350000km on it, to have the "look" I
wanted. It is not a "performance" look - -

I'm just curious how close do you think you can get to "accurate" gas
mileage calculations using the classic odometer plus fill it up to guess at
the gallons used method?
With my scanguage calibrated to my GPS, over a 2 or 3 tank run I can
be accurate to tenths

I've read that nobody can accurately get the sig figs closer than +- 1 mpg,
despite the fact that most people I've seen do it try to calculate it down
to the tenth or even hundredth of a gallon, which, even for computers, is
impossible given there are no controls.

I used to have a gas milage tester that could be accurate to way less
than a tenth - fuel consumption measured to within less than a cc.

So 20mpg is really from 19mpg to 21mpg, which makes calculation difficult
(when I was looking up the wheel size stuff earlier today, Consumer Reports
said as much so that's why I'm curious how close you think you can get to a
repeatably precise figure (yes, both repeatable, and precise).
With the fuel mileage rig I had (for carbureted vehicles) you could
see the differnce made by changing tire pressure by a few PSI if the
wind didn.t change. You could see the difference from winding down a
window.

On 7/19/2017 7:59 PM, wrote:
On Thu, 20 Jul 2017 01:45:19 -0000 (UTC), Mad Roger
wrote:

On Wed, 19 Jul 2017 19:20:49 -0400,
wrote:

If I drive very conservatively I CAN get a bit better mileage than
with the original small tires, but generally speaking, in normal
driving there is little if any improvement -and around town, it is
slightly worse. The truck works harder every time it starts from a
stop or accellerates at low speed. I'm willing to put up with that on
a 21 year old truck with about 350000km on it, to have the "look" I
wanted. It is not a "performance" look - -

I'm just curious how close do you think you can get to "accurate" gas
mileage calculations using the classic odometer plus fill it up to guess at
the gallons used method?
With my scanguage calibrated to my GPS, over a 2 or 3 tank run I can
be accurate to tenths

I've read that nobody can accurately get the sig figs closer than +- 1 mpg,
despite the fact that most people I've seen do it try to calculate it down
to the tenth or even hundredth of a gallon, which, even for computers, is
impossible given there are no controls.

I used to have a gas milage tester that could be accurate to way less
than a tenth - fuel consumption measured to within less than a cc.

So 20mpg is really from 19mpg to 21mpg, which makes calculation difficult
(when I was looking up the wheel size stuff earlier today, Consumer Reports
said as much so that's why I'm curious how close you think you can get to a
repeatably precise figure (yes, both repeatable, and precise).
With the fuel mileage rig I had (for carbureted vehicles) you could
see the differnce made by changing tire pressure by a few PSI if the
wind didn.t change. You could see the difference from winding down a
window.



Maybe you can answer a question I've long wondered about.

Many cars claim in the owners manual that opening the window uses more
gas than turning on the AC. My 1987 Nissan van even claimed this, with
its almost square front and back. However, if I was going up a steep
hill in hot weather with a full load, it would slow down a lot more from
running the AC than from opening the window. Have you ever tested this
with your test rig? On what kinds of vehicles, and what did you find?
Windows or AC better?

On 07/19/2017 01:51 PM, Mad Roger wrote:
This Consumer Reports report says that the OEM tires are designed for fuel
efficiency where the replacement tires can have a few mpg impact, so, that
seems to back up the claim that too many things change even if all you do
is change the tire diameter.
http://www.consumerreports.org/cro/n...nomy/index.htm
"Consumer Reports recently tested a few all-season tire models with low
rolling resistance and found that those tires can improve fuel economy by
an additional one or two mpg."

LRR tires can also significantly reduce tire life. As long as the
manufacturer can boost the CAFE numbers with an OEM LRR tire they are
not concerned with the tire life. Replacement LRR tires tend to be more
expensive than other options. Given the current gasoline prices I'm
willing to give up a couple of mpg for better life and handling
characteristics.

On 07/19/2017 03:47 PM, wrote:
I remember the super-modified races at Flamborough S. Ontario
in the early 1970's .. their brakes were glowing red at the end of
the feature ! I don't know how they avoided fires ?
The cars were akin to go-carts - but with big modified V8 engines.

The outlaw karts are karts -- most of which have side mounted 600cc
Honda two-strokes. As far as weight to horsepower they are right up
there. You can get into it for under $10K too. I'd be seriously
interested but I don't think they have a geriatrics class

The local track is a 1/6 mile dirt oval and they're turning laps under
10 seconds. It's fast even if it doesn't have the earth shaking roar the
dirt track races of my youth did. I took my fiance -- once. She just
about had a panic attack from the noise.

On Wed, 19 Jul 2017 22:33:56 -0400,
wrote:

Not necessarily - a 10 spoke alloy rim will weigh less than the
typical 5 spoke, because there is less aluminum there. Also, a rim
with more open space wighs less than one with more - to the point my
16 inch torque thrusts weigh less than my 14 inch deerfoots.

I am not at all disagreeing with you that different rims weigh different
amounts where size isn't the only determinant of the weight.

I never disagreed. I'm just trying to control the variables in this thought
experiment because I was trying to figure out what the benefit, alone, was
of larger-diameter fitments.

Does anyone know if, apples to apples, you increase a rim by one inch,
whether the decrease in sidewall rubber compensates enough to counteract
the gain in rim weight?
Depends on the tire. With an LT tire, likely. With a "performance"
passenger car tire, likely not

Thanks. I didn't look up the density of the rubber versus the metal, mainly
because the volume matters greatly and I would have no weigh of knowing
that for this thought experiment.

It seems from most of the referenced articles that, realistically, there's
no change in gas mileage for an inch change in diameter simply because of
all the other factors involved in the real world.
With one inch, likely no net loss - with 3 or 4, almost definitely in
city driving.

I have to agree with you that the two reliable articles that referenced
four inches of change all showed (and expected) huge losses in performance.

None of the articles seemed surprised at the losses, although the consumer
reports article discussed that the measurements were such that they were
within their measurement margin of error.

On Wed, 19 Jul 2017 19:30:03 -0700,
Bob F wrote:

The torque loss is defined by the physics of that change. The mileage
resulting is determined by the characteristics of the vehicle, engine
and gearing.

That's a better distinction summary than I could have written.
Thanks.

On Wed, 19 Jul 2017 22:34:44 -0400,
wrote:

The reality is that it seems the variables I tried to keep out of the
original question (for example tire width, tread pattern, rubber material,
inflation pressure, unsprung weight, etc.) can make more of a difference
than does the larger diameter tire.
Don't bother arguing with Trader - he's CLUELESS

I can tell who knows what they're talking about and who doesn't so thanks
for the warning.

Pretty much if someone says something (even me) without backing it up with
a reference, it's just hearsay.

Nothing wrong with hearsay - but it's not believable unless it's
accompanied by some believable reference.

Even what I say isn't believable (even to me) unless I can back it up with
a reliable reference (I don't trust my intuition more than I trust anyone
elses' intuition).

Heck, my intuition tells me that time is invariant, but Einstein's
equations prove my intuition wrong, so I have to accept facts contrary to
my intuition.

My original intuition was that there was some measurable and meaningful
benefit of the larger diameter fitment - but in the end - it appears -
there's no good reason (in most cases) to have larger diameter fitments.

If one were to control all the random variables, then they "might" get
something good out of the larger diameters - but it would take a lot of
control over relatively difficult variables (like the torque curve of the
engine).

On Wed, 19 Jul 2017 22:59:45 -0400,
wrote:

So 20mpg is really from 19mpg to 21mpg, which makes calculation difficult
(when I was looking up the wheel size stuff earlier today, Consumer Reports
said as much so that's why I'm curious how close you think you can get to a
repeatably precise figure (yes, both repeatable, and precise).
With the fuel mileage rig I had (for carbureted vehicles) you could
see the differnce made by changing tire pressure by a few PSI if the
wind didn.t change. You could see the difference from winding down a
window.

Take everything I say with a grain of salt because I'd have to dig up the
references of where I got this idea that even the EPA can't get better than
4% (as I recall), and they don't measure volume (since that's inaccurate).
They measure weight. And they used, as I recall, plastic bags filled with a
known *weight* of fuel.

In addition, they ran on test course, and they repeated the tests.
And even then, they couldn't get better than 4% as I recall.

Unless I dig up the reference, that's all hearsay, but, as I recall, nobody
is going to get accuracies and repeatabilities anywhere near decimal places
at home if they're not repeating the tests under extremely well controlled
circumstances and weighing the fuel consumed.

On 07/19/2017 03:52 PM, wrote:
I'll admit putting the 16 inch torque thrusts on my Ranger was
"mostly" for looks - the 14 inchers didn't look like they belonged in
the large wheel openings, particularly with the higher 4700 gvwr
suspension the truck came with ( it sits about the same as a 4X4), and
the rather rare 16 inchers became available at a good price - - -

I didn't change the wheel size but the OEM tires on my F150 looked
pretty stupid. After they wore out I've always went for meatier tires on
the same rims. The downside is the truck sits higher and working on the
engine isn't quite as convenient.

I ran bias plies until they got to be very hard to find. Rough, noisy,
and with sidewalls you could bounce volcanic rock off of all day.
Radials have gotten better but they used to have very tender sidewalls.

On 07/19/2017 04:10 PM, wrote:
Cheap old motorhead farts notwithstanding ..
When I can't avoid visiting the city - I enjoy watching
the Kids with their lowered cars trying to go
into/out of a driveway ... duh. Really ?
At what point does reality kick in ?
John T.

Nothing changes. Remember the chopped and channeled bathtub Mercs that
high centered on a cigarette butt?

Then there are the hoppers:

https://www.youtube.com/watch?v=UC491a3UFoo

On 07/19/2017 07:45 PM, Mad Roger wrote:
I'm just curious how close do you think you can get to "accurate" gas
mileage calculations using the classic odometer plus fill it up to guess at
the gallons used method?

Who uses the classic odometer method? This is the age of computers.

On 07/19/2017 08:59 PM, wrote:
With my scanguage calibrated to my GPS, over a 2 or 3 tank run I can
be accurate to tenths

Mad Roger lives in the past. What I find cute with the scangauge set for
instantaneous reading is when you get off the throttle, the injectors
shut off, and the reading goes to 99.999 mpg.

On Wed, 19 Jul 2017 23:04:35 -0600,
rbowman wrote:

I'm just curious how close do you think you can get to "accurate" gas
mileage calculations using the classic odometer plus fill it up to guess at
the gallons used method?

Who uses the classic odometer method? This is the age of computers.

From what I read long ago, we're not going to get anywhere near decimal
place accuracy at home, but I need to check this out to be sure of my
figures before I can argue it effectively with you.

Here's a seemingly expensive "fuel economy meter" which shows the
complexity of calibration, heated probes, high-speed sampling, auto zero,
etc. whose specs show a "resolution" of "± 2% reading" and a "repatability"
of "±2 % of reading" with a "span drift" of "±2 % of reading"
http://mustangae.com/products-servic...+Economy+Meter
http://mustangdyne.com/mustangae/upd...09/MAE-FEM.pdf

On Wed, 19 Jul 2017 23:07:03 -0600,
rbowman wrote:

With my scanguage calibrated to my GPS, over a 2 or 3 tank run I can
be accurate to tenths

Mad Roger lives in the past. What I find cute with the scangauge set for
instantaneous reading is when you get off the throttle, the injectors
shut off, and the reading goes to 99.999 mpg.

Remember I said 4% accuracy, so let's see if my statement holds water over
the next few days. If that is correct, then anyone quoting accuracy with a
decimal place in it is ridiculously misled.

Doing a quick search, Car & Driver says the EPA gets to 1% with what
appears to be a 350 million dollars investment in tools.

"Measuring fuel economy during the tests is likewise hugely complex, which
is why the automakers and the EPA both follow precisely the same protocol.
For openers, the chemical composition of fuel varies slightly, so simply
retrieving it from a local gas station won¡¦t produce repeatable results.
The EPA has a specialized company manufacture small batches of consistent
fuel, which is 93 octane ... Before being used, the gas is analyzed to
measure its properties, and fuel economy is then calculated based on the
measured carbon content of the various tailpipe emissions¡Xunburned
hydrocarbons, carbon dioxide (CO2), carbon monoxide (CO), methane (CH4),
and oxides of nitrogen (NOx)¡Xthat are collected in bags made of a special
Kynar plastic. A $350,000 gas-analyzing machine then makes minute
measurements. The one-percent accuracy of this machine from Japanese
company Horiba is amazing considering the minuscule amounts of some of the
exhaust constituents¡Xsome in quantities as low as a half-dozen parts per
million.
http://www.caranddriver.com/features...economy-page-2

So what's 1% to a typical consumer?

Reading the whole article, I can't tell if that 1% is 1% of 20mpg or 1% of
18 gallons.

If it's 1% of, say, 20 mpg, then that could mean it's +/- 0.2 mpg (or 19.8
mpg to 20.2 mpg).
If it's 1% of, say, 20 gallons, then that could mean it's +/- 0.2 gallons
(or 19.8 gallons to 20.2 gallons).

On Wed, 19 Jul 2017 21:19:40 -0700,
Bob F wrote:

Maybe you can answer a question I've long wondered about.

Many cars claim in the owners manual that opening the window uses more
gas than turning on the AC. My 1987 Nissan van even claimed this, with
its almost square front and back. However, if I was going up a steep
hill in hot weather with a full load, it would slow down a lot more from
running the AC than from opening the window. Have you ever tested this
with your test rig? On what kinds of vehicles, and what did you find?
Windows or AC better?

Fuel-Economy Face-Off: Driving With Windows Open or With A/C Running?
http://www.consumerreports.org/fuel-...or-ac-running/
By Consumer Reports, June 18, 2017

Q. Does a car use more gasoline when you drive with the windows rolled down
or the air conditioning turned on?

A. ´We found that on an 85-degree day, running the A/C can reduce fuel
economy by 1 to 4 mpg, depending on the car....[while] the effect of
opening the windows at 65 mph did not measurably reduce fuel economy,¡

On Wed, 19 Jul 2017 21:19:40 -0700, Bob F wrote:

On 7/19/2017 7:59 PM, wrote:
On Thu, 20 Jul 2017 01:45:19 -0000 (UTC), Mad Roger
wrote:

On Wed, 19 Jul 2017 19:20:49 -0400,
wrote:

If I drive very conservatively I CAN get a bit better mileage than
with the original small tires, but generally speaking, in normal
driving there is little if any improvement -and around town, it is
slightly worse. The truck works harder every time it starts from a
stop or accellerates at low speed. I'm willing to put up with that on
a 21 year old truck with about 350000km on it, to have the "look" I
wanted. It is not a "performance" look - -

I'm just curious how close do you think you can get to "accurate" gas
mileage calculations using the classic odometer plus fill it up to guess at
the gallons used method?
With my scanguage calibrated to my GPS, over a 2 or 3 tank run I can
be accurate to tenths

I've read that nobody can accurately get the sig figs closer than +- 1 mpg,
despite the fact that most people I've seen do it try to calculate it down
to the tenth or even hundredth of a gallon, which, even for computers, is
impossible given there are no controls.

I used to have a gas milage tester that could be accurate to way less
than a tenth - fuel consumption measured to within less than a cc.

So 20mpg is really from 19mpg to 21mpg, which makes calculation difficult
(when I was looking up the wheel size stuff earlier today, Consumer Reports
said as much so that's why I'm curious how close you think you can get to a
repeatably precise figure (yes, both repeatable, and precise).
With the fuel mileage rig I had (for carbureted vehicles) you could
see the differnce made by changing tire pressure by a few PSI if the
wind didn.t change. You could see the difference from winding down a
window.



Maybe you can answer a question I've long wondered about.

Many cars claim in the owners manual that opening the window uses more
gas than turning on the AC. My 1987 Nissan van even claimed this, with
its almost square front and back. However, if I was going up a steep
hill in hot weather with a full load, it would slow down a lot more from
running the AC than from opening the window. Have you ever tested this
with your test rig? On what kinds of vehicles, and what did you find?
Windows or AC better?
Back when I had the use of the unit, AC was not as efficient as it is
today, but at low speeds it was more efficient to open the windows,
although a lot less effective here where relative humidity is quite
high. At highway speeds the extra drag from open windows and all the
bufetting inside the car made the AC more efficient. I strongly
suspect the same is still true today with more efficient AC - perhaps
the "transition speed" is lower today.

I know running with the windows open at 60 MPH across Kansas and
Oklahoma back in 1976 did NOTHING to make the cab of my 1957 Fargo
more comfortable, so whatever the mileage hit for AC, IT WAS ON!!!!

On Thu, 20 Jul 2017 04:29:21 -0000 (UTC), Mad Roger
wrote:

On Wed, 19 Jul 2017 22:33:56 -0400,
wrote:

Not necessarily - a 10 spoke alloy rim will weigh less than the
typical 5 spoke, because there is less aluminum there. Also, a rim
with more open space wighs less than one with more - to the point my
16 inch torque thrusts weigh less than my 14 inch deerfoots.

I am not at all disagreeing with you that different rims weigh different
amounts where size isn't the only determinant of the weight.

I never disagreed. I'm just trying to control the variables in this thought
experiment because I was trying to figure out what the benefit, alone, was
of larger-diameter fitments.

Does anyone know if, apples to apples, you increase a rim by one inch,
whether the decrease in sidewall rubber compensates enough to counteract
the gain in rim weight?
Depends on the tire. With an LT tire, likely. With a "performance"
passenger car tire, likely not

Thanks. I didn't look up the density of the rubber versus the metal, mainly
because the volume matters greatly and I would have no weigh of knowing
that for this thought experiment.

It seems from most of the referenced articles that, realistically, there's
no change in gas mileage for an inch change in diameter simply because of
all the other factors involved in the real world.
With one inch, likely no net loss - with 3 or 4, almost definitely in
city driving.

I have to agree with you that the two reliable articles that referenced
four inches of change all showed (and expected) huge losses in performance.

None of the articles seemed surprised at the losses, although the consumer
reports article discussed that the measurements were such that they were
within their measurement margin of error.
Because consumer reports does not do a terribly scientific
comparison.