terry993 said:
All very interesting this. One question I have if this is all correct why do Porsche fit 21" wheels to the GT3RS?
terry
Yes very good question Terry,
Wheels have got bigger on Road cars for numerous reasons:
To accommodate bigger brakes, but also to deal with Increased heat.
Narrower higher profile Tyres have a longer (Front to rear) contact patch and this does not allow the tyre to cool much
between each revolution, Lower profile Tyres have a narrower contact patch front to back, but a wider contact patch from
left to right which cools a lot better.
The heavier and more powerful Road car's evolved the higher profile tyres (70 then 60 series) had to be made with a hard compound
(Treadwear rating) to avoid them overheating, wearing out very quickly and potentially having a blow out.
Widening the tread and making the sidewall smaller decreased the amount of tyre on the road front to rear and allowed softer compounds
to be used, as mentioned previously car's got heavier and more powerful so a bigger diameter Wheel was also beneficial to accomadate
bigger brake discs.
They have also been used as a fashion feature, especially when touring cars had to go large diameter (due to ride height regs)
they started putting them on Hot hatches, and from then on Big wheels were marketed as being cool like Touring cars (but not F1)
In time with more understanding and evolvement in the case of Porsche they have engineered the car's suspension to suit such large wheels
and of course all the electronic aids now work overtime.
If it was possible to fit 21" wheels in your 993, you would then experience an awful dangerous and very uncomfortable driving experience
where the steering wheel be constantly trying to snatch itself out your hands, the car's handling would be terrible as the scrub radius and other
geometry would all be wrong, out of whack and generally it would not be possible to drive the car safely.
Formula one attempting to consider using 18" Wheels (To improve he Looks for younger generations!) and they did try a development set,
but the car not only lapped 12 seconds a lap slower but the driver said the car was far too nervous, skitty and dangerous!
So they've stuck to 13", although they are going wider for next year's car's again to improve the Look, and make better use of more downforce.
The downside of a low profile tyre and large wheel is acceleration (Traction) and braking is not as good as the contact patch of
a larger profile tyre, but today's modern cars are too heavy and powerful to handle these large profiles without causing heat and wear issues, so
they all now engineer many electronic traction, skid, stability, Yaw controls etc....to make them safe for the road.
R