I have had my a4 for around 6 months it drives fine but i was looking at the tyres yesterday and they are 245/40/18 on the back and 235/40/18 on the front is there a reason for doing this or should i go 245s allround or 235s or is it ok
Tyres
- Thread starter jimmc
- Start date
They should be the same size all round really. I'm sure some people mix them, however the manufacturer would certainly advise you stick to 235 40 18 for all tyres. Some people fit 225 40 18, however I've not seen 245's fitted. I suspect they probably look and work fine, however if it were me I would buy two more in 245 or 235 to make a matching set.
northernlight
Registered User
If you deviate much from the manufacturers recommendation then the speedo will read inaccurately due to the change in overall diameter. I don't imagine 245/40/18 will have a huge difference over 235/40/18, maybe 2-3mph change in reading. One advantage of the wider tyre will be less chance of kerbing the alloys!
Visual Tyre Size Calculator | Kouki Tech
Although i imagine its only affected by the front wheel tyre size.
The correct sizes for the B7 are :
235/50/16
235/45/17
235/40/18
235/35/19
There is less than a percent difference in diameter between these four sizes.
It's usually accepted that up to a 2% difference is okay.
245/40/18 is 1.5% larger than 235/40/18
So if the 245's are on the front wheels (doubt it) your speedo will read 1.5% lower than standard.
marktdisport
Registered User
why will the speedo read different between 235/40's & 245/40 the 40 is the profile which is the same the 235/245 is the width no difference in reading until you change the 40 number !!!
northernlight
Registered User
Shouldn't rub. I bought some wheels with 245 on and no problems even though wheels were ET50. Plan to use some other wheels I have with 245s on ET45 currently fitted to another car. Stock is ET42 so even more lateral clearance.
Is your car a Quattro? If it is, then there are potentially serious consequences for the transmission if the car is run on different size tyres for any great length of time. The front wheels will be rotating at a different speed from the rears, and if the car has four-wheel drive, this will cause excessive wear in the centre differential.
John@mk
Registered User
