Alloy wheel choice for largest Avon roadrunner rear tyre

Peter Waller

Peter Waller

MEMBER
Joined
May 2021
Messages
56
Country flag
I have a 1974 Commando 850 in Norvil race trim cafe racer style and want to change the rims from the standard chrome 19" to alloy flanged rims with stainless spokes. I would like to fit a wider rear tyre as it drives me mad looking at that skinny rear tyre! My question is what rim size for the rear to accomadate the largest Avon roadrunner tyre my frame can take. Should I have an 18" on the back and 19" on the front? And will this affect the handling having a wider rear tyre AND an 18" on the back with a 19" on the front? I am only 5ft 7" so lowering the bike would be a bonus and I live in the UK. Thx Pete.
 
Going from 19" to 18" rims is not much difference in height, going wider you are restricted to your swing arm, chain clearance and all, you might have a bigger choice in tyres to choose from, but seems a lot go for the 18" on their Commando's, when I built my 850 Commando/Featherbed back in the 80s I just went with 19" Akront alloy rims and they were cheap at $90 for each rim in them days, they are still on my Norton and still look great after 46 years on the bike, the bike handled better going from steel to alloy rims, you wouldn't think so but made a big difference, well on my bike anyway.
So does size matter, everyone will have an opinion, myself just stuck with the size rims my Norton came with.

Ashley
 
On my 72 750 i have 18 x 3" rear rim and 19 x 2.5 " front alloys. I tried a 120 pirelli on rear but it was too wide. Had to run it not in line with front tyre to miss the chain guard. Installing the wheel was a problem as well. I now run dunlop tt100 GPs 4.0 x18 rear and 100/90 19 front. Good handling, stick like glue but don't last long. Pirellis were useless. No grip and understeered, but lasted too long! couldn't wait to get them off. IMO handling is affected more by other things, like engine mounts, how they are adjusted, especially top mount. CNW mount is good. Changed triple clamps to 850 ones for more trail. That made a big difference. Lot more stable at high speed cornering. Any 4.0 x 18 will fit nicely on the rear, with an appropriate rim size. Graham
 
velo54 said:
On my 72 750 i have 18 x 3" rear rim and 19 x 2.5 " front alloys. I tried a 120 pirelli on rear but it was too wide. Had to run it not in line with front tyre to miss the chain guard. Installing the wheel was a problem as well. I now run dunlop tt100 GPs 4.0 x18 rear and 100/90 19 front. Good handling, stick like glue but don't last long. Pirellis were useless. No grip and understeered, but lasted too long! couldn't wait to get them off. IMO handling is affected more by other things, like engine mounts, how they are adjusted, especially top mount. CNW mount is good. Changed triple clamps to 850 ones for more trail. That made a big difference. Lot more stable at high speed cornering. Any 4.0 x 18 will fit nicely on the rear, with an appropriate rim size. Graham
Click to expand...
Thanks for the reply Graham:) Pete.
 
I have now found a rim supplier here in the UK (Central Wheel Components) https://central-wheel.co.uk/collections/norton-commando-rims so can I ask which one of these 18" rims do I need for the widest rear tyre but WITHOUT causing any clearance problmes with the swinging arm and chain etc? 18x2.5 WM3. 18X1.85 WM2 and 18x 1.60 WM1. Also for the front it is a choice of 19x2.15 WM3 19x1.85 WM2 and 19X1.60 WM1. Sorry for all the questions but I want to get it right first time and not waste my money on the wrong product.
 
I got my standard alloy rims from Central Wheel about 2 years ago. 18 x 3" and 19 x 2.5 ". SS spokes as well. I did the fitting and all went together very well. Rims nice and straight. Most would probably prefer 18 x 2.5" and 19 x 2.15". The wider rims put a little more rubber on the road and less chicken strips on the side. I think the 3" rim looks impressive with its deep drop centre. With the TT100 GPs i can use all of the tread. Any 4" tyre will have enough clearance. 100/90 front will clear as well. Graham
 
I was doing something similar a few years ago and made the following spreadsheet - may be helpful?
Alloy wheel choice for largest Avon roadrunner rear tyre
 
We seem to have at least 3 threads asking pretty much the same thing currently. Don’t you guys asking these questions read other threads ??

FWIW I now favour Bridgestone BT46s. I’ve done with Avon due to their contemptuous conduct.

I believe Bridgestone say that 2.15 is ideal for the 3.25 19 front and that it’s fine with 1.85 to 2.15.

Ideal for the 4.00 18 rear is 2.75 and is ok 2.15 to 2.75.
 
Alloy wheel choice for largest Avon roadrunner rear tyre


AM26 Universal has a range of 2.15-2.75 rim size. Unfortunately they are not available. But that spec seemed fairly common for that size tire the last time I investigated. I'm pretty sure the BT45 had those same specs but for some reason the BT46 calls for a 2.5 IIRC, working off of memory on that one.
 
Back
Top