Running different profiles of tyres front / rear?

[BrotherMouzone]

My track tyres are 195/50/15, and my set of road tyres are 195/55/15 as recommended by the manufactuer.

I'm going to two track days in France this summer (same weekend) and I'm planning to bring two full size spare wheels.

If I had to mix up the tyres (due to punctures etc), it doesn't really matter does it? It wouldn't affect the handling characteristic too much would it? Obviously I would change the pair rather than just the punctured tyre.

Thanks.

[TypeRTom]

No problems with doing that but I would try to fit similar tyres to the two spare wheels to avoid any big difference in grip front to rear that could alter the handling characteristics of the car and catch you out.

[jonnyleroux]

not recommended. you're changing the rolling radius (and therefore ride-height) of the car at one end. If you have the taller tyres at the front it's likely to understeer (safe but dull) if you have the taller tyres at the rear it's like to oversteer quite badly.

Jonny
BaT

[TypeRTom]

Agree it's not ideal but the difference the OP is talking about is 1cm sidewall/ride height (about 10% difference) and ~3% rolling radius difference. I think with a difference in tyre size that small you could easily re-adjust the balance of the car with tyre pressures and just take a bit of time to get a feel for the effect it may have on the handling.

[andburg]

Have you checked out the legality of straying from the manufacturer specified tyre size? I understand France is quite strict on modifications

[Jerry Can]

jonnyleroux said:

not recommended. you're changing the rolling radius (and therefore ride-height) of the car at one end. If you have the taller tyres at the front it's likely to understeer (safe but dull) if you have the taller tyres at the rear it's like to oversteer quite badly.

Jonny
BaT

err j5, i know you are not the biggest fan of bavarian metal, but all bmw m sport models have taller profiel tyres at the front and lower profile tyres at the rear. Beemers aren't really understeerers are they.

as for the OP, you need to put the same profile tyre on each axle ( but they can be different front to rear, IYSWIM)

[jonnyleroux]

Jerry Can said:

err j5, i know you are not the biggest fan of bavarian metal, but all bmw m sport models have taller profiel tyres at the front and lower profile tyres at the rear. Beemers aren't really understeerers are they.

as for the OP, you need to put the same profile tyre on each axle ( but they can be different front to rear, IYSWIM)

The difference is the BMW's are designed to operate that way. The issue isn't the difference in tyre size, it's the relative adjustment in the axle height. you would end up with the same issues if you ran tyres with the same profile on a BMW designed to have different profile tyres.

As for not being a fan of bavarian cars - we've had BMW's for nearly 10 years now - it's a great ROAD car ;-)

Jonny
BaT

[BrotherMouzone]

Thanks for all the replies.

I will need to replace the 'road' tyres in April (with track biased road tyres as I don't do that many miles) but undecided about the profiles hence this thread. Cheers.