On 7/7/2020 2:42 PM, Clare Snyder wrote:
On Tue, 7 Jul 2020 09:23:07 -0400, Wade Garrett
wrote:

I love my 2016 Toyota Avalon Limited....except for the rough ride. You
can feel most every bump, expansion joint, pavement crack and manhole
cover on the road. Even shallow potholes slam and are a teeth-jarring
experience! The tires are inflated to the door sticker pressure and
there's nothing wrong with the suspension.

I know Toyota gave this trim model a "sportier" suspension with
225/18/45 skinny tires on 18 inch wheels to improve handling- rather
than go with the fatter 215/17/55 on 17 inch wheels on the lower trim
models.

It's getting to be tire time and I wonder if it might be worth buying a
tire/wheel package in the smaller size.

Would the taller 55 sidewalls absorb road bumps better? Any problems
with transmission shift points, speedo readings, any of the
electronics/gauge stuff, etc.?
Definitely better ride, and NO change to any calibrations. The
215/55/17 will rie better. I would defintely be checking to see if a
16 inch rim will clear the brake calipers and if so go to a 215/ 65 16
or possibly even a 215/70) which will change the speedo calibration by
a small amount but not cause any other issues)or 21

Way back last spring when Micky was obsessing over replacement tires I
built a set of MATLAB functions to compare nominal dimensions from tire
profile data-- those were

fnHSect=@(SW,AR) SW*AR/25.4/100; % Section Ht inches
fnDrim=@(Drim,SW,AR) Drim+2*fnHSect(SW,AR) % Overall diameter (in)

where SW is standard width (mm) and AR the aspect ratio, Drim is nominal
rim diameter (in)

For the above

fnHSect(215,55)/fnHSect(225,45)
ans =
1.1679


there's 17% more section height for the 215/55 over the 225/45 but if
you went with 225,55, that would be 22%--

fnHSect(225,55)/fnHSect(225,45)
ans =
1.2222


Don't have a correlation for effective spring stiffness at hand, but
that would be enough I'd think be noticeable in softness; just how much
it'll affect the handling will depend on whether you really push the
limits or not...

I really liked the stiffer suspension on the Chrysler 300M with the
sport package option until moved back to KS on the dirt roads...then it
was a tooth-rattling experience for sure. Plus, it had so little road
clearance for mud sold it after a couple years. Anyways, back to the
main thread,

fnDrim(17,215,55)/fnDrim(18,225,45)
ans =
1.0130


Is only 1% difference overall diameter/same for circumference for
calibration error...

fnDrim(17,225,55)/fnDrim(18,225,45)
ans =
1.0297

if go back with 225.

Surprisingly, even the 16" w/ 65 ratio is about the same...

fnDrim(16,215,65)/fnDrim(18,225,45)
ans =
1.0397


The section height portion change with the SW ratio compensates even
more than the rim diameter change...

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