17" rims

[amalventano1 at tds.net (Allyn)]

> This brings up a question I've had for a long time: which is more critical in the handling qualities of a tire, assuming two
identical tires (we are talking street stuff, not slicks) one used for 15,000 miles and down, evenly, to the wear bars...the other
just mounted and taken for a 25 mile jaunt, just enough to scrub the treads clean of compound...which would be the preferred tire
for Sunday's autocross??

I've got an example that may answer this one.  Wifes Jetta.  She's a bit, well, 'tough', on her tires.  We got that Jetta last year,
with new rubber all around (nothing racy, but still good rubber).  So, I happen to look at the tread and the fronts are at/near the
bars.  Rears are still nearly new.  So here we have tires of the same age, but differing wear.  Rotating front to rear resulted in a
clear handling shift - it now pushes considerably more in the turns (except on cold, wet enterance ramps - in that case is spins off
the road and scares the crap out of her).

> Would the responsiveness of the "shaved" tread be offset by the increased hardness of many-times-recycled-and-aged rubber?

I see where you're coming from, but I think rubber has to *really* age (i.e. inception of dryrotting), before low tread would
overcome high tread.  Additionally, even 'old' tires, provided they were routinely driven, should be close to new as far as tread
softness goes.  Routinely 'working' the tires (i.e. driving on them), keeps a steady flow of compounds moving to the surface /
sidewall.  These compounds are supposed to last the life of the tire, and keep the tread soft / block UV / prevent dryrotting.

> Would the grip of new, soft rubber be offset by the squirmy-ness of new, tall tread blocks?

There is actually some types of road that works better with some tread.  The really pointy / gritty / rough type.  The down side to
this is that those nice sharp edges of the tread blocks won't stay nice and sharp for long, so any advantage quickly fades away as
the 'bite' looses its 'teeth'.  Once this happens, we're back to the deformation due to the increased leverage of the taller blocks,
which will result in lower grip than shallower tread.
		 
> Would the grip of new rubber be more desireable than the crispness/controllability/accuracy of the stiff tread on the old tires??

I believe the stiffness actually works against you, as the better the rubber conforms to the road, the more contact area there is to
aid in grip.

> I don't know.... it might come down to personal preferrence.  What would be YOUR preferrence?

At the track?  If it's dry, shaved rubber hands down.  The closer to slicks the better.  The only reason for tread is water
channeling / wet drivability.  The only reason treaded tires have tall tread is so they maintain their anti-hydroplaning abilities
for a reasonable mileage.  People just won't buy a street tire they have to replace in 5k miles.
		 
> given series:  (say, aspect ratio of 40)  a 205/40-14 will have the same sidewall height as a 205/40-18, and as you pointed out
elsewhere, sidewall height has a lot more influence on overall lateral stiffness than wheel diameter....so for all intents and
purposes, would they not be equal?

Imagine the length of the contact patches are equal.  In the case of the larger wheel, the cornering forces will act over a larger
arc of the tire bead, as it is occurring at a larger radius as compared to the smaller wheel.

Additionally, in the case you cited, the belt area is a much larger diameter.  With steel belted tires, the tread deflection is
spread around the entire sidewall (i.e. all the way around the tire).  Sure it falls off as you move away from the contact patch,
but it's still felt all the way around.  In the case of the larger wheel + same sidewall height, there is more circumferential belt
area to spread the load, and more sidewall to support it (laterally).
		 
> So... the larger the wheel size, the smaller (more desireable for performance) the aspect-ratio tires that are made to fit it.
So, theories aside, you are right... where it counts.....where the, ahem, rubber meets the road. :)

Well it wasn't a goal to 'win' this one... We both learned something in the process.
		 
$0.06
:)
larry
sandiego16v

I see your $0.06 and raise you... a blown Koni
:)
Al

P.S. - Larry, turn off the HTML in your email client, or just tell it to keep the format of the received email.  It makes in-line
replys damn near impossible after converting back to text format.