Tyre size - feel the width ?

[21TVR]

Tuscan: Currently running on 245/40 ZR18's on the rear (S02's)
I am about to re-tread to Toyo Proxes T1's
It is possible to run a 275/40 on this rim - so says the Toyo web page!

What will happen to the handling if I do ?

Thanks guys

sp

[shpub]

1. Just because it will fit on the rim doesn't mean it will clear the bodywork.
2. It will screw up the handling because of the different profile and the wider tyre which effectively screws up the geometries.
3. Going to the extreme width on a rim distorts the contact patch and can actually reduce the amount of grip.

steve
www.tvrbooks.co.uk

[Guillotine]

not lucky enough to own a tuscan but my griff (and chimps) have different sizes on the rear. these vary from 225 - 245 back and 205 - 225 front so going up one size MAY give you some more grip and (as i suspect is what you want) look even better!
geometry may be slightly different but i doubt you'd notice a change of +20 on standard.
best to speak to someone like www.peninsulaautomotive.co.uk to see what they think. they have developed several handling packs for grifs/chimps so know what they're doing.
i beleive joospeed (on here) has done similar

[GreenV8S]

best to speak to someone like www.peninsulaautomotive.co.uk to see what they think. they have developed several handling packs for grifs/chimps so know what they're doing.

With all due respect to Peninsula, you should pay attention to Steve's advice. There are not all that many people around who have explored the range of wheel/tyre/suspension setups under controlled and repeatable conditions and know the actual pros and cons of changing them.

[21TVR]

Thanks for this people, makes you wonder really, the car was designed to have the standard 16" rims and tyres, I bought it with the 18's and wonder wether it's had anything changed to compensate!!!

thanks again

sp

[Guillotine]

fair enough...

i was only suggesting that someone who has developed suspension systems for griff/chimps with nitron and has fitted hundreds of after market wheels/tyres to all makes, and has therefore had the chance to drive them before and immediately afterwards, MAY be worth a phone call.

arms folded - nose in the air...

[andyf007]

One of the important factors is the rim width in determining wether a tyre will fit or not. 275's will work better on 9.5 to 10" rims, with 9" as a minimum and 11" as a maximum, therefore I'm assuming you are on 9" rims? 245's are a bit on the small side for a 9". Best tyre size for that size rim would be to go to 25540. This will only increase the side wall by 4mm and the tread width by 10mm, but will maintain the geometry, if not improve it as the 245's are a bit small. Like SH said though check your clearances lock to lock, it may be that the 245's were fitted because they only just clear the arches and inner wing.

If you must fit the 275's, then don't try to pull too many 'G' when cornering.

Andy

[shpub]

I am running 225 and 245 tyres on 9 inch wide ex Tuscan Racer split rims on the 520 and they are good because the sidewall is braced and this stops the tyre rolling off the rim. Used to run the standard 225 tyres on a 7J rim and used to wear out the sidewall lettering. The wheels were too narrow and the tyre ballooned at the edge.

This is the problem that many forget about because things look good cosmetically. A significant amount of the suspension movement and response is determined by the tyre/wheel combination and tyre pressures. Change any of this and the handling is modified. This why us competition types spend so much time adjusting tyre pressures and so on.