FAO Peter Humphries

[dejay]

Peter,

As you do alot of racing in your green V8s, are you able to answer a query I have.

Why do TVR put different size wheels on some of there models ie 15" wheels on the front, 16" on the rear, Do they keep the same rolling radius front and back?

I assume its to help with handling, but I can't see what the advantage is, can you help?

Ps I know its a strange question, but its one of those annoying things that has been bugging me!!!

Cheers......

One happy S owner from MK

[shpub]

quote:Peter,

As you do alot of racing in your green V8s, are you able to answer a query I have.

No he isn't! He's broken the diff again and having one made from unobtanium with expensivcium coating! The car has been abandoned at Tower View for the last 3 months.

You don't have to have the wheels the same size as they front move independently of the rear. Bigger wheels allow bigger discs and different width/profile tyres. Higher profile tyres have more give in them and give a bit softer handling and suspension. Lower profile are stiffer and do the opposite. Running different sizes allows some tuning of the handling characteristics.

The only cars that I know that run different front/back diameters are the Griffs and Chimaeras. The others have same diameter wheels but different tyre sizes.

Steve
www.tvrbooks.co.uk

[GreenV8s]

quote:Why do TVR put different size wheels on some of there models ie 15" wheels on the front, 16" on the rear, Do they keep the same rolling radius front and back?

Without going into the mechanics that cause it, wider lower profile tyres are stiffer sideways and produce slightly more grip in the dry (but less in the wet). Disadvantages are the grip falls off more quickly once the tyre is pushed past the limit of grip (the tyre 'breaks away' more) and there is less sidewall height to protect the rim from the road and soak up bumps. I went from 15 to 16 on the rear of the V8S because the extra lateral stiffness meant the car was more stable at high speed. The difference is quite noticeable by the way, and was one of the factors in correcting the high speed oversteer. As far as I know the overall rolling radius of the 15" front and 16" rear Chimaera / Griffith wheels are similar (at about a nominal 1970mm I seem to remember) but there is no reason why they need to be. There are various pros and cons of taller/wider wheels and tyres but I suspect the real reason TVR chose those sizes was more to do with styling!

BTW thanks for the sympathetic note Steve! How's the tripple throttle body coming on? They do look very nice, and John was saying if I couldn't afford a supercharger they were definitely worth considering!

Cheers,
Peter Humphries (and a green V8S)

[dejay]

thank you for answering my question, I thought it would be mainly to do with handlining but i didn't want to make any assumptions.

Cheers