tyre size

Does anybody know what the biggest tyre size you can use on your st70?? without catching chain and front forks lee

In 10" version:
Michelin S1 130/90 at the rear
110 - 120 in front (depends from make and model)

Thanks waynus your a star!!

Waynus are you 100% sure you can fit 130x90 rear and 120/90 front ? as i am looking to change my standard 3.50x10 i like the look of some michelin reggae,s and do not want any issues fitting them to standard rims on my 76 st70.

I made a little typo... It's the Michelin S1 130/70, not /90.

I have this set, 130/70 + 110/80 (if you have the 110/90, the front will be higher as the rear)
Thi set should fit all Honda ST's. The 130 won't fit some of the Chinese versions.
A 120 should fit any time, in front and rear.

Sorry Waynus i,m a little confusesd can i fit 120x90 front and rear,they are only available in 120x90 or 130x90 .
cheers Ian.
Also some kenda tyres are on ebay advertised as 120x90 to fit st70s ????

Sorry for the confusion, I'll try to sum it up as simple as possible.
First the size notation: 130 = Width of tyre (mm) 90 = height of tyre, % in relation of width
Each make and model has it's own shape of the 'cheecks' of the tyre.
Together with the different dax models (OT, NT, low fender, high fender,...) makes it impossible to give an easy answer to this question.

Front: 110 fits always, 120 depends on bike and tyre
Rear: 120 fits always, 130 depends on bike and tyre

(All on standard 10" Honda rims, on an original bike.)

Keep in mind that for handling having a smaller front tyre compared to the rear is nicer.
It also looks better when the rear is higher as the front. (Too my taste... and you will have to do the math to find out the different heights)
Michelin S1 tyre sizes:
10-90/90
10-100/80
10-100/90
10-110/80
10-130/70
10-3.00
10-3.50