Norm Peterson

Understood, although that still does not justify 20's. Or explain from a technical standpoint why the 13.8" rear rotors on the GT500 get the 20's and the 15" front rotors only get 19's.




Norm

TheDivaDanielle

they're also using a taller tire to compensate for any difference.

l00kitzzlilcj

Lmao at "gtfo"

I have 19 all around but if I could do it again, is probably keep the 19s in the front on my 245s and then go 20s in the rear with like 285s. That's how the gt500 comes stock anyways.

X3xMONGOOSEx3X

I'd go with 20's.

Norm Peterson

Strictly visual is all I can make out of that.

There is no obvious need to have 6" wheel to rotor difference for the rear brakes vs only 4" on the much more heavily worked fronts.

285/35-20 is half an inch taller than 265/40-19, and that amount taller of a tire plus the bigger 20" wheel is probably drawing attention away from the fact that the 285/35 has about a quarter inch less sidewall than a 265/40.

The optical games designers play . . .


Norm

audioAl

I vote for 18's as they will accept 285's and this is the proper size for track use. If you only street your car 20's are ok.

POWERMAN_

That's just plain sexy.

Superb stance + nice choice of wheels.

Cruzinaround

Lower profile sidewalls will not flex as much which should provide (depending on the tire) a controlled linear failure when the limits of the tire are reached, which is what many professional test drivers call the FUN factor in driving because the rear will swing out on you but, will allow for the driver to reign it back in and plus sizing will require the proper width to provide more contact with the tarmac on a wider surface area (AKA Drift). On a taller Profile When the limits are reached then at that point of failure with more flex on the sidewall can result in a catastrophic failure of the tire bead separating under repeated extreme loads. This of course applies to a road course type setup or a street setup where the driving can often be spirited and take a path that is far from a straight line. Driving on Twisties with acute Apex's and sweeping curves benefit from a wider cross section and lower sidewall coupled with the proper suspension. However road feel will be amplified...so beware of potholes.

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Norm Peterson

Failure? I suspect you're talking about tire behavior around peak grip, which can be a linear increase in grip up to just before it goes away (IOW, peaky) or a much more gradual transition that starts a lot earlier at lower g's and gives the average driver extra margin against losing it completely.


Any tendency for tailhappiness places a greater demand on driver skill to be able to rein it back in, because it all happens faster and with less warning. (and once you "catch" it, you have to be ready for an equally if not more sudden spin in the opposite direction).


Unseating the bead might happen if the tire in question is badly enough underinflated but is unlikely otherwise.

The main thing to realize is that taller profile tires give more warning (tires squealing, mushy steering response) as their limits are approached. Most people then do the sensible thing and not drive quite that hard any more unless they're avoiding some kind of accident.


It's probably harder to break a tire bead by "hard driving" than you think, even at near-zero psi. Never mind how I might know this.


Norm

Cruzinaround

Actually its relevant the performance of the tire design in question. The patterns of the radials and the treads along with the composition used in the tire compounds. All relevant to the ultimate performance characteristics of those tires in relation to the width and height. Predictability on performance is gained from a stiffer shorter sidewall.... So that you can under inflate the tire for better grip without the mushy response and feedback of the taller profile. And have better feedback behind the wheel. The outer limits of the tire with a wider contact patch and stiffer sidewall allow for a linear failure at the limits of the combination...the entire combination of suspension, tire and wheel.

End Goal being a slow degradation of grip after its exceeded conditions for peak grip to where its predictable and easy to recover from.


The fact that the failure is linear with the combination of all the components means a lesser skilled driver can catch it.

Unseating the bead would likely happen when the failure results in "hitting the wall" or "the Curb" or any irregularities on the tarmac surface that would cause the tire sidewalls to crumple and fold.

Then again the same can Happen with a lower profile sidewall or even a bent rim, but the linear failure again allows for a lesser skilled driver the benefit of more opportunity to recover.



Its not the failure of the grip that breaks the bead...its the final outcome and where you end up that will ...break the bead, or bend a rim, or bend an axle. There are far more variables involved.

Tire design is driven by the faster performance vehicles... and clearly driving faster means that this is one area where the engineers are on point to go fatter and lower. Not for a 1/4 mile run but an extended long range at higher speeds. Which is why when the pinnacle of tire and wheel design is leaning more and more towards non pneumatic solutions with extremely low profiles and impact absorbing wheel designs to allow for those higher sustained speeds without a catastrophic failure.

If anything what engineers have learned is that outside of the short 1/4 mile expectations a taller profile tire actually hides much of the feedback response that is beneficial for staying on course.

They don't put tall tires on a Bugatti or a Hennessy or a SSC Aero or a Pagani... Or any Vehicle capable of sustaining these speeds WELL beyond a quarter mile simply because they can explode at sustained high speeds. Its an engineering thing.... I know.