I'm trying to discover who supplies the replacement wheels for RMs to take the 1000R225 tyres, I need a set for a customer abroad. Maker and part number would be useful.

You really need someone to look at what is stamped on their rim, wheel centres are sized by tyre bead width not the tyre size other than the diameter, split rims are sized the same and as you know you will need to make sure the stud hole size is correct and of the cone type
Split rims are stamped as well, usually in this format B7.0HD20 which translates as 7.0 is 7 inches from outer bead to bead on the centre on a 20 inch centre, offset which is from centreline of two beads to outer edge of end flange that nuts go to comes into play as well.
I have dug into my memory and by chance searching on the net come across a name i have seen before doing multipallet deliveries for one of the pallet hub local depots.
http://www.aspectwheels.co.uk/contactus.php
Think there is another firm in south wales that make them as well, i would think that the ones fitted with 10R22.5 on RM/L's will be 7.0 x 22.5 in wheel centre speak which is about 10 1/2 inches face to open end (ie complete width of centre)
HTH

Mark

My bus number (if any): RM1414 sort of

Thanks for the info. Aspect Wheels can make them to order, cost around £300 each plus vat and carriage.