tyre size

[A Williams]

I have a 1956 BSA B31. It has 3.0x19 front and rear. The front is ok and I am happy with it. The rear looks like it should be on a push bike! Their is a very large gap between the tyre and the lower edge of the rear mudguard. I would like to fit a bigger tyre, 3.25x19 is standard but would like a Avon AM7 safety mileage but they do not make a 3.25 but do make a 3.5. Will this be ok with the 3.00 front? My other problem is I have a fully enclosed rear chain guard, will the bigger tyre hit this? 

Andy

[Pete C]

I think the B31 Standard tyres are 3.25x19 front and back. I usually use a 3.50x19 on the rear as these are easier to come by and that's the recommended size for the B33 which is identical to B31 except for the extra 150cc.

Pete

[STAR TWIN]

I have a 3.25 ribbed on the front and a 3.50 SM MkII on the rear of my B31.

[Richard Mills]

I have a B33 with a 3.25x19 (Avon) front, and a 3.5x19 (Heidenau) rear with a fully enclosed chainguard. No clearance problems, but I will measure if you want.

[Richard Mills]

Meant 3.50 x19 rear.

[A Williams]

I have a B33 with a 3.25x19 (Avon) front, and a 3.5x19 (Heidenau) rear with a fully enclosed chainguard. No clearance problems, but I will measure if you want.

I will definitely buy a 3.5 19 Avon AM7 for the rear now I know it will work with my chain guard. I will probably get a 3.25 19 AM6 for the front.
Thank you every one for your help. Andy

[paulm]

fit road riders will transform the bike