I have a MK. 1 CRM 250 which I am thinking of converting to SM. I recently fitted USD front forks from a later model and need to know what is the maximum rim and tyre width I can fit without getting any chain rub.
I was thinking of: Front rims 3.5\" with a Maxxis Street sport 120/70 R17 tyre and Rear rims 4.25\" with a Maxxis street sport 160/60/R17 tyre.

I don't want to order this stuff, then find it won't fit.

Any help appreciated.

I have the same sizes on my Mk1, the rear tyre runs very close to the chain, I can see where the chain has fouled the tyre slightly, I have also had to cut off the inner Chain guard mount.
A 150 width would be much more suitable but you would still need to remove the chain guard mount.
The front is fine on mine (conventional forks).

Thanks, d5aul, seen the photo of your SM on an earlier post. The wheels look good.
what tyres are you using on you Mk1? and was the amount of chain rubbing a major concern? Also did you change your rear sprocket size?

Thanks

Hi, I am running Dunlop D207RR's, they are soft sticky track day tryes but road legal, I got them from ebay as a pair of part worns, only really scrubbed in & cost £50.
The chain rubbing has not caused a problem, the chain does actually clear the tyre but it is the sideways movement of the chain that causes the clash. done quite a few miles now & no problems.

Thanks again d5aul, that has sorted my problem. It will take a month or so to finish the project but will post a pic when it's finished. If I need anymore info , I will PM you.

Cheers