[s-cars] Stopping - Tire patch questions

[Sean Douglas]

Rich:

I agree with you, maybe I wasn't explaining myself very well. Yes, the
area of the contact patch is fixed, it's the shape that changes. Now,
I'm not sure if the shape has any relationship to directional motion,
i.e. if the shape is short and wide, does it provide more lateral grip
versus a shape that is long and skinny that provides more longitudal
grip (forward motion). The former would favor cornering power and the
latter would favor acceleration / braking.

Maximum stopping distance is obtained the moment before the tires lose
grip with the road surface (just before lockup). Any braking system is
easily powerful enough the "lock the brakes" with any given tire and I'm
not sure that the friction developed by tires varies significantly
enough to make a difference. I realize that on a track situation bigger
brakes dissapate heat better and provide more pedal feel which would
contribute to shorter stopping distances, but I find it difficult to
believe that the advantages of bigger brakes do not apply in a one time
situation as in normal street use.

Don't get me wrong, I'm not dissagreeing with you, I've seen this type
of question many times before and never really got a straight answer
with a theorectical back-up.

So I guess the bottom line is, Gary should toss the Turanzas and install
the big reds and put a smile on his face :-)

Regards,

Sean



> -----Original Message-----
> From: Richard Tanimura [mailto:richard at tanimuras.com]
> Sent: Thursday, October 02, 2003 3:54 AM
> To: Sean Douglas; 'Lewis, Gary M'; 'S-Car List'
> Subject: RE: [s-cars] Stopping - Tire patch questions
>
>
> Sean,
>
> I am not sure I understand you.
>
> Theoretically atleast, patch size (sq. inches) will not vary
> with tire width. But the patch shape will. This is of course
> assuming the same tire pressures. And I am convinced that
> patch shape must play some kind of a roll in braking and
> acceleration. Otherwise why would F1 cars run such fat
> rubber? To me, that says that tire width matters. Maybe there
> is another reason and I will be glad to get an explanation.
>
> I think stopping distance - in a one time stop situation - is
> more a function of tires not brakes. I.e. tires are the
> limiting factor and not brakes. Now in a track situation
> where heat due to repeated, hard braking reduces braking
> power, then that is another thing. Maybe that is what you
> were talking about.
>
> Rich
>
> -----Original Message-----
> From: s-car-list-admin at audifans.com
> [mailto:s-car-list-admin at audifans.com]On Behalf Of Sean Douglas
> Sent: den 2 oktober 2003 05:58
> To: 'Lewis, Gary M'; 'S-Car List'
> Subject: RE: [s-cars] Stopping - Tire patch questions
>
>
> Your RS2 setup sounds great.
>
> The size (width and diameter) of the tire has little to do
> with stopping distances, it's a function of the tire's
> composition (coefficient of
> friction) and braking power.
>
> Sean Douglas
> 1997 Audi S6 - MTM Stage 1+
> 1990 Audi 90Q20V
>
>
> > -----Original Message-----
> > From: s-car-list-admin at audifans.com
> > [mailto:s-car-list-admin at audifans.com] On Behalf Of Lewis, Gary M
> > Sent: Wednesday, October 01, 2003 11:22 AM
> > To: S-Car List
> > Subject: [s-cars] Stopping - Tire patch questions
> >
> >
> > Now that I have the insane-RS2-setup, I've noticed the car goes so
> > much better than it stops.  I have big reds going on ASAP (RS2
> > brackets are stuck in NYC customs.  Grrrrr..), but I'm currently
> > over-braking the brand new Bridgestone Turanza's the P.O.
> put on the
> > car.
> >
> > Anyway, was wondering if an 17x8 or an 18x8 with attendant
> tires will
> > stop better than the 16x7's I got on there now. Car is scary.
> >
> > Also, do the Highline Faux Avus rims fit our cars??  Are they worth
> > buying??
> >
> http://highlinewheels.wheelize.com/search/srcWheelSearch.asp
>
> Thanks!!!
>
> Gary Lewis
>
> 1995.5 S6 Avant, Green/Ecru, RS2 MAF, RS2 Exhaust Manifold,
> RS2 Injectors, Custom Turbo (K26 Turbine, Factory K26 Cold
> side (Audi Works '999' P/N) with 50mm intake and custom
> Innovative Turbo compressor wheel), Bilsteins, Eibachs, Big
> Reds on the way.
>
> 1990 200TQW, K24 Turbo, 1991 TQ Intercooler, 1.8 bar, Bypass
> Valve, Euro's, Bilsteins, Redline in tranny and diffs, FOR SALE
>
>
>
>
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