Been trying to understand tyre markings on my trailer tyres.
It is marked as 205 75 R14

That should mean (I think) rim diam is 14", height of tyre is 75mm and
width is 205mm.

Form this you would assume overall diam of Tyre would be 14" (i.e.
355mm) plus 2 x 75mm so overall width of 505mm
Yest if I measure it the overall width is 635mm significantly
different.

Anybody know why the discrepancy?

The 75 figure is the aspect ratio and dimensionless.
--
DB.

"Osprey" wrote in message
ups.com...
Been trying to understand tyre markings on my trailer tyres.
It is marked as 205 75 R14

That should mean (I think) rim diam is 14", height of tyre is 75mm and
width is 205mm.

Form this you would assume overall diam of Tyre would be 14" (i.e.
355mm) plus 2 x 75mm so overall width of 505mm
Yest if I measure it the overall width is 635mm significantly
different.

Anybody know why the discrepancy?


The 75 refers to the profile and is a measurement of the height of the
sidewall/tyre width given as a percentage.

Adam

On Oct 30, 5:53 pm, Osprey wrote:
Been trying to understand tyre markings on my trailer tyres.
It is marked as 205 75 R14

That should mean (I think) rim diam is 14", height of tyre is 75mm and
width is 205mm.

Form this you would assume overall diam of Tyre would be 14" (i.e.
355mm) plus 2 x 75mm so overall width of 505mm
Yest if I measure it the overall width is 635mm significantly
different.

Anybody know why the discrepancy?

http://www.google.co.uk/search?q=tyre+sidewall+markings

Mathew

In message . com,
Osprey writes
Been trying to understand tyre markings on my trailer tyres. It is
marked as 205 75 R14

That should mean (I think) rim diam is 14", height of tyre is 75mm and
width is 205mm.

Form this you would assume overall diam of Tyre would be 14" (i.e.
355mm) plus 2 x 75mm so overall width of 505mm Yest if I measure it
the overall width is 635mm significantly different.

Anybody know why the discrepancy?

Surprisingly difficult to find good sites with info on tyre wall
markings - KwikFit have a tiny subsection and doesn't address the OPs
query. Dunlop.co.uk also had minimal info.

But, http://www.tyres-online.co.uk/tech.asp (no connection etc.)
provides all the info. you need I think.

--
Si

In an earlier contribution to this discussion,
Osprey wrote:

Been trying to understand tyre markings on my trailer tyres.
It is marked as 205 75 R14

That should mean (I think) rim diam is 14", height of tyre is 75mm and
width is 205mm.

Form this you would assume overall diam of Tyre would be 14" (i.e.
355mm) plus 2 x 75mm so overall width of 505mm
Yest if I measure it the overall width is 635mm significantly
different.

Anybody know why the discrepancy?

As others have said, the 75 refers to the aspect ratio as a percentage. So
the 'height' of the tyre is 75% of 205 = 153.75

So the overall diameter is (14 x 25.4) + (153.75 x 2) = 663 mm

Not quite the 635 which you measured, but a lot closer than 505!

For tyre markings in general, see
http://www.ntta.co.uk/law/trailers/tyres.htm
--
Cheers,
Roger
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monitored.. Messages sent to it may not be read for several weeks.
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Osprey wrote:
Been trying to understand tyre markings on my trailer tyres.
It is marked as 205 75 R14

That should mean (I think) rim diam is 14", height of tyre is 75mm and
width is 205mm.

Form this you would assume overall diam of Tyre would be 14" (i.e.
355mm) plus 2 x 75mm so overall width of 505mm
Yest if I measure it the overall width is 635mm significantly
different.

Anybody know why the discrepancy?

If I might just throw in my own recommendation, take a look at the
following:- http://www.carbibles.com/tyre_bible.html

It is by far the most comprehensive explanation I have found of all tyre
sidewall markings, sizes, wheel configuration, offset, etc.

--
Dave N

N.B. Mail sent to "nospam" will be rejected. The Reply-To address works.

On Oct 30, 9:47 pm, Dave N wrote:

If I might just throw in my own recommendation, take a look at the
following:- http://www.carbibles.com/tyre_bible.html

It is by far the most comprehensive explanation I have found of all tyre
sidewall markings, sizes, wheel configuration, offset,

The whole Car Bible series is well worth a bookmark...

(coupled with http://www.batteryfaq.org/ for car battery info!)

Mathew

Huge (Huge ) gurgled happily, sounding much
like they were saying:

Been trying to understand tyre markings on my trailer tyres. It is
marked as 205 75 R14

That should mean (I think) rim diam is 14", height of tyre is 75mm and
width is 205mm.

Form this you would assume overall diam of Tyre would be 14" (i.e.
355mm) plus 2 x 75mm so overall width of 505mm Yest if I measure it
the overall width is 635mm significantly different.

Anybody know why the discrepancy?

The "75" is the aspect ratio. The lower the number, the lower the
sidewalls.

And is given as a percentage of the nominal tread width.

So, in the OP's example, you've got 355mm + 2x(75% of 205mm) = 355+2x154
= 663mm.

Tyre sizes must drive the metrication fascists bonkers; three numbers,
one metric, one imperial and one dimensionless

Not exactly "dimensionless".

not to mention the speed rating which is an arbitrary index, not in
alphabetical order, to a speed in mph (that's the "R").

No, that's R-for-Radial. There's a piece of information we're not given
in the original post - the load & speed ratings. A decade or more ago,
tyres used to be typically labelled "205/75 HR14" - where the H was the
speed rating. Now they're more typically "205 75 R14 87H" - where the 87
is the load rating and the H the speed rating.

http://www.blackcircles.com/general/sidewall

Huge (Huge ) gurgled happily, sounding much
like they were saying:

Tyre sizes must drive the metrication fascists bonkers; three numbers,
one metric, one imperial and one dimensionless

Not exactly "dimensionless".

So, what are it's dimensions? Acre-feet? Lightyear-barns? Barrels per
kiloparsec? It's a ratio, and therefore dimensionless.

It's one of those "it is and it isn't" numbers, I reckons. No, on it's
own, it is dimensionless, but taken as a whole at least it's easy to turn
into an absolute dimension - unlike the load rating number...

On Nov 1, 10:32 am, Adrian wrote:
Huge (Huge ) gurgled happily, sounding much
like they were saying:

Tyre sizes must drive the metrication fascists bonkers; three numbers,
one metric, one imperial and one dimensionless
Not exactly "dimensionless".
So, what are it's dimensions? Acre-feet? Lightyear-barns? Barrels per
kiloparsec? It's a ratio, and therefore dimensionless.

It's one of those "it is and it isn't" numbers, I reckons. No, on it's
own, it is dimensionless,

And remains so whoever's company it keeps.

but taken as a whole

A whole lot of nonsene, maybe.

at least it's easy to turn
into an absolute dimension

You can use the ratio to calculate one dimensions from another. The
ratio itself remains dimensionless, it does not get turned into
anything.

Maths wasn't your strong point at school, then.

MBQ

" )
gurgled happily, sounding much like they were saying:

Maths wasn't your strong point at school, then.

I've never lied about having failed A-level Maths, 'tis true.

On Nov 1, 12:36 pm, Adrian wrote:
" )
gurgled happily, sounding much like they were saying:

Maths wasn't your strong point at school, then.

I've never lied about having failed A-level Maths, 'tis true.

Nor have I, LOL! OK, I didn't quite fail but got a D due to a bout of
complacency and insufficient revision. I got an A the second time
round!

MBQ

On 31 Oct 2007 22:03:34 GMT, Huge wrote:

Tyre sizes must drive the metrication fascists bonkers;

We forced them to drive the last of those Alfasud Tiis with their 350mm
rims, until they realised that rims ought to be sized in inches, if you
ever wanted to find tyres to fit. That taught 'em.