Just sorted some TT comps for a mate two are 195 and two are 205. Which way is advisable? 195 fronts 205 rears? Or the other way around?

Neither, it will screw up the ABS as rolling circumference will be wrong between axles, unless he runs different profiles for the two tyre sizes.

Thought he just meant widths. If they are the same profile then they will be fine

Thought he just meant widths. If they are the same profile then they will be fine

Yeah I did mean widths they've got 40 profile both of them.

But profile is a percentage of width so if the width is different so is the profile.

But let's do some maths

40% of 195mm is 78mm

40% of 205 is 82mm

So 4mm difference in profile, being as you can have 8mm difference between a brand new tyre and a worn out one I can't see it causing an issue.

I used 205 and 215 before now, was told difference would be to small for the car to notice, and it was fine.

Matt

I've got 195's on my 16's, noticed no difference swapping between the 205's

In the short term you'll be fine..

Just change to the same size tyres when the time comes to needing a change!

But profile is a percentage of width so if the width is different so is the profile.

But let's do some maths

40% of 195mm is 78mm

40% of 205 is 82mm

So 4mm difference in profile, being as you can have 8mm difference between a brand new tyre and a worn out one I can't see it causing an issue.

Are you sure on those figures, don't you need to then multiply the ratio by 2?

So the difference in total profile is 8mm (164mm-156mm) before you compare between a new and old tyre.

Need two spare wheels if you get a puncture

Need two spare wheels if you get a puncture

I have no spare wheel, just a can of tyre weld. if mine goes it's too low to get the jack under so it doesn't really matter :p

Are you sure on those figures, don't you need to then multiply the ratio by 2?

So the difference in total profile is 8mm (164mm-156mm) before you compare between a new and old tyre.

A new tyre typically has 8mm tread whereas an illegal one has less than 1.6mm, so that's a 6.4mm difference all around the circumference of the tyre. Techies calcs show a difference of 4mm all around the circumference of the tyre, i.e. less than the difference between a new tyre and an illegal one. You can go and double both of those figures if you want to compare the diameter, but there's really no need to because the point has already been made