magic!jaistanley wrote:The reason the cars handle best on 15"s (or indeed the wheel they were designed to run on) and not aftermarket wheels is that certain geometries are programmed in.
The king pin inclination is the angle of the centre of the wheels effective contact patch to the pivot point of the top of the McPhereson strut. This and the slip angle of the tyre determine the dynamic camber and castor of the wheel.
If you choose the offset, width and tyre profile correctly you can reduce adverse effects. Smaller profile tyres, to a point, can improve the feel of a car but has two nock on effects. The slip angle of the tyre is reduced and on rough surfaces has less compliance so don't deform to maintain grip.
Changing diameters widths and profiles also changes the shape of a tyres contact patch. Different shapes exibit different characteristics of grip and camber thrust.
The cumulative effect of the above are the symptoms you describe. 'Not feeling right'. Rather than go into detail (and have to look stuff up in uni notes - quit while you're ahead!) I'll leave it at that!
Touring car wheels were massive to accomodate massive brakes and reduce tyre temperatures and pit stops (wear).
Jai
Just what i was after!!
So surely by keeping 15's and lowering the car, this would also have a similar adverse effect as you are changing the standard geometricies that the car was inherited with?
Also in chosing aftermarket wheels, consideration has to be given to changing the suspension set up of compensate the adverse characteristics of aftermarket wheels (or just drive slower)?
After reading your post, I would question whether touring cars larger wheels are a response to improved grip. As you said, the tyre will not deform to maintain grip and this surely will put an increased stress on the rubber, causing greater wear? I suppose this is offset by having big tyre widths?
Formula 1 technology braking has also demonstrated that immense braking power is possible without supersized brakes?
It's probably not a fair comparison as Touring car have completely different suspension set ups which are a conclusion of heavy investment, testing and some fecking clever people.
We have our mates opinion and mass market plug and play alternatives!!
