tyres for 21" 239 v spoke wheels

[raf555]

factory fit is:
285/35/21 fronts (10J)
325/30/21 rears (11.5J)

Was wondering what is widest / narrowest i can go with these wheels as the factory size tyres are very very rare?!!

thanks

[X5Sport]

No wider on either as those are the max recommended width, but the 10J could go as narrow as 255 and the 11.5J down to 285.  Remember you need to maintain the rolling radius as well by changing the profile ratio to match or you will end up with problems with the speedo, or wind up the transmission to the point of breaking something (front/rear diff or transfer box being the most likely).

Oh and welcome......

Richard

[raf555]

what size should i fit on the front if i went 305/30/21 on rears??

cheers

[X5Sport]

305/30/21 isn't the correct profile.  Those tyres will cause problems as the rolling radius is different. 

The middle figure is the sidewall height expressed as a percentage of the tread width so a 305/30/21 has lower sidewalls than a 325/30/21 and has a different rolling radius.  If you come down in width then you must come up in profile.

That set will throw your speedo out.

Richard

[martin33100]

Has anyone ever gone to a narrower tyre on the 20's?