195 and 205 front or rear?

[grayfox]

Was just thinking with the same wheels and tyres all round apart from either;

the front pair width being 195 while the rears are 205 or vice versa be any kinda problem? I realise sidewall height would differ very slightly and due to that it may actually not be great if your running abs (which I am.. I hate flat spots) I know many rwd circuit chaps run slightly wider wheels at the back for better traction.

 

[Sylvester]

Was just thinking with the same wheels and tyres all round apart from either;

the front pair width being 195 while the rears are 205 or vice versa be any kinda problem? I realise sidewall height would differ very slightly and due to that it may actually not be great if your running abs (which I am.. I hate flat spots) I know many rwd circuit chaps run slightly wider wheels at the back for better traction.

If you put 205 on the front, the handling will be a bit worse than before. FF cars at 1/4 mile run have wide front tyres, due they don't need to turn much. 205 on the rear are not much problem, but if you can, just put 205 on all wheels around. I was thinking about 205 as well, but insurance would go quite high to me

 

[joedeltahf]

i have ran 205s all round before and they provide more grip in conering and breaking and less wheelspin in low gears but it feels less nippy and i get a little bit of contact on the front inner wing on full lock

 

[Ian G]

You'll adjust the understeer/oversteer tendency, wider on the back will just make it more likely to break away at the front. Which is quite safe but far less fun and probably not even as quick when you consider broken traction is also at your driven wheels.

Might even make it worse at the back depending on compound choice, ground pressure effects etc.

Tyre contact patch is a function of the weight of the entire car and you should aim to maximise that, anything else in particular changes to one axle relative to the other is just moving around the handling characteristics, not necessarily increasing absolute traction.

Different thing for RWD where you have forward linear and lateral forces acting on that axle. There's also a lot more than tyre size that will affect the overall picture, roll stiffness relative front to back being the other big one. If you had a handling complaint then it might be one thing you could try, or if you want to try and see where the tendancy moved to that would be an interesting exercise, but its not correct to say it will give you more outright grip. You'd need to try it.

 

[grayfox]

You'll adjust the understeer/oversteer tendency, wider on the back will just make it more likely to break away at the front. Which is quite safe but far less fun and probably not even as quick when you consider broken traction is also at your driven wheels.

Might even make it worse at the back depending on compound choice, ground pressure effects etc.

Tyre contact patch is a function of the weight of the entire car and you should aim to maximise that, anything else in particular changes to one axle relative to the other is just moving around the handling characteristics, not necessarily increasing absolute traction.

Different thing for RWD where you have forward linear and lateral forces acting on that axle. There's also a lot more than tyre size that will affect the overall picture, roll stiffness relative front to back being the other big one. If you had a handling complaint then it might be one thing you could try, or if you want to try and see where the tendancy moved to that would be an interesting exercise, but its not correct to say it will give you more outright grip. You'd need to try it.

Great reply, cheers mate.