The tyre manufacturers publish details of the circumference and diameter of their tyres but probably this will be suck it and see. The 11.00 x 22.5 tyre is considerably bigger than a 10.00 x 22.5. It is however almost the same dimensions as a 10.00 x 20 which IIRC I have seen on an RM. You will need to check clearances on full lock as well as clearance on bump. It will definitely increase the overall height. They will more than likely not fit on the rear so you will need to be careful.

I suspect you're right there roy, clearances on lock will be zero!

I had this problem with an RT many years ago when presented for certification the examiner insisted it needed 1000x20 tyres. The London 7 Country had their RT on that size and tyres rubbed the chassis on full lock. After I told the examiner that there were 4700 of them in London on 900x20 tyres and gave him the number of another certified RT, he had to accept what I said.

Didn't RMLs run on 1000x20s due to the extra weight?

My bus number (if any): RML2532, BEA MLL721, BEA MLL738, GS67, RT2629

To the OP, DON'T use those rims on the back unless you've had the additional holes for the brake drum bolts drilled out.

My bus number (if any): RML2532, BEA MLL721, BEA MLL738, GS67, RT2629