Running Two Different Tyre Sizes... Help

[Gmac]

Needing help/thoughts...

Looking at getting winters for the S3 8l and I've seen 2 x 225/45/18 and 2 x 225/40/18

So I was wondering if this would be ok to run with the haldex on the S3.

Would these calculations be correct....

225/40 = 225mm width and side wall 40% of this so 22.5 x4 = 90mm ie 9cm for side wall (4.5 top 4.5 bottom)

225/45 = 225 width and side wall 45% of this so 90mm + 11.25mm so 101.25mm ie 10.12cm

So 1cm different? (.5cm top and .5 bottom

Tia

 

[monopole]

I'm sure they would be fine on different axis, but you need better advice than I could offer on this

 

[Gmac]

Anyone else?

 

[Andrew@A.L.D]

if you have traction control you will have issues

 

[Gmac]

if you have traction control you will have issues

Not sure what you mean? do you mean the esp or do you mean the haldex controller might not like it?

 

[snowy]

The ABS unit's speed sensors will detect the axles turning at different rates and assume slip

It might try to do all sorts to fix this - eg using brakes or more power to rear axle

You can use any width combo, but circumferences of wheels on both axles has to be the same

 

[Gmac]

Great, cheers snowy! I'll just get the 225/45's and keep an eye out for some more of the same! Thanks folks!

 

[kryton]

It goes bananas and traction control light flashes . I tried this

 

[Alex C]

When the 225/45 are doing 62.4mph the 225/40 are only doing 60.3,mph, so one set of tyres are walking slowly away from the other pair and subsequently the Haldex works overtime

 

[RobinJI]

Sounds like you're not going to try it anyway, but just for future reference, the size calcs are correct, but that's for each side of the wheel. So a 225/40 has 9cm top and 9cm at the bottom as well.

(I'm not sure on this, but isn't the standard S3 size 225/45r17, so surely a 225/45r18's going to be an inch too big? I'm sure someone will know.)

 

[Nick_sheep]

Anyone who's interested I use this calculator for tyres.

http://www.rimsntires.com/specspro.jsp