Rim width vs tire size and style

I have read various opinions regarding ideal rim width for tires such as the newer Avons. Some say WM2 is sufficient, some say WM3 is minimum and others recommend WM4.
I need to purchase new rims front and rear and I will choose alloy, probably valenced. My question is, have any of you had a bad experience with WM4 and modern Avon tires and, conversely, what is the widest rim that an older style Avon Road Runner will properly fit?
I should add that I want to fit tires that are as wide or close to the original 4.10 Road Runners.
Thanks,
Ed

I have been investigating this myself, because I'm in the process of adapting yamaha cast aluminum wheels to my commando. I wasn't so worried about the front rim's width since I didn't want a fatter front tire, so I just went with a WM2 (1.85") front rim width. For the front tire, I am trying to decide between a 100/90/19 tire or to go skinnier for lighter weight and quicker steering with a 90/90/19, but either way I think a WM2 rim width is fine up front. I don't see any advantage to a WM3 up front except to change the aspect ratio of the tire's shape on the rim.


The back tire was a different story. Like you, I contemplated WM4, but I really didn't want to find out the hard way that it wasn't going to work OR that it was going to give me a situation where I had to ditch the chain guard and run my tire dangerously close to a greasy open chain. The rear tire that I found was a WM3 (2.15") rim width and it already had a useable (but not new) 120/90/18 tire on it. Since I am going to buy a new pair of tires for these rims anyway, mocking up the new wheels with the existing 120 width tire on it gives me a chance to test that 120 wide tire to see if it will fit before I buy a new 120 width avon to replace it. If I am not comfortable with the clearance of the 120 width tire then I'm just going to order the new avon tire in 110 width.

In my case, I was facing too many other obsticles to make my cast wheel modification work to take a chance and add WM4 width rims into the equation, especially when a 120 width tire fits WM3, and is probably as wide a tire as you can get on the rear of a commando anyway. I also checked out the tire heights because people are always warning against going to an 18" tall back wheel. The 2 tires I have are both exactly the same height even though the front is 19" rim and the rear is an 18" rim. I can't see why it would diminish the handling when they are both the same height.

This week I will get the modified rear wheel parts back from the machinist. I'll put my new parts on, and I will know for certain how the WM3/120 width tire combination works in my commando swingarm. If you're interested, I can post how much clearance there is to the chain and the swing arm with that combo... If I can keep the chain guard and have a 1/8th space to the tire, I am going with the WM3/120 tire...

Yes. Please do post your results.

Thank you,
Ed

Go to the Avon website. Avon states that the proper rim width for the 100/90 x 19 Roadrider is WM4 (2.5") with acceptable alternatives being 2.75" or 2.15". A WM4 rim gives the proper profile for these tyres. Look at what they recommend for the Norton Commando with 1.85" rims and, guess what? They recommend the 100/90 Roadrider, a full two sizes narrower than the ideal. I have used enough of these tyres to know that they work fine on the standard rims. BUT, you will have chicken strips half an inch wide, which tells you that the profile is wrong. You simply cannot go to the edge of the tyre. If you leaned it far enough to get to the edge, you would have ground half your crankshaft away in the process.

I run Morad 2.5" x 19 alloy rims both ends with Avon Roadrider 100/90 x 19 tyres. The little handling quirks that Commandos show are either elimjnated or reduced to almost zero. Light and accurate steering results.
I suspect that this combination puts more rubber on the road at any lean angle than a 120 section tyre on an 18" rim. No proof of this. But, the 100/90s on 2.5" rims only just fit. I've had to use button headed capscrews to hold the front guard on (when fitted, haha, don't ask!) or the wheel just doesn't squeeze into the forks. No issues with the chain or the chain guard. The fact that a 120 section tyre fits should tell you that the profile is wrong under the same conditions.
The few people who have tried this combo have given positive feedback. AS soon as someone says "I'm doing it for the looks" has lost me in the discussion. The same people who go out with high heel shoes I guess.

Interesting that you have in effect gone for a wider front tyre when a lot of people go for the narrower rubber. I have a pair of 100/90 19" Roadriders and at some stage will have the wheels rebuilt and had never considered a wider front rim, I understand however what you are saying about the profile.
It will be interesting to hear your thoughts on this combination, on the road.

No speculation involved. I have run this combination for many thousands of miles. Other people who have ridden it comment on the handling.

I use 100/90 Avon Roadrider rear tire on a stock WM2 rim, no problem at all. I fact a noticeable improvement compared to the Dunlop TT100 I used previously.

Has anybody installed the Avons with spoons not a tire machine? I 've never had an issue putting on
TT100s, was wondering if the modern tires are difficult or impossible to hand mount.

Onder said:

Has anybody installed the Avons with spoons not a tire machine? I 've never had an issue putting on
TT100s, was wondering if the modern tires are difficult or impossible to hand mount.

Click to expand...

Tube-type tires are easy. Also they are less problematic on what would be considered a too-narrow rim. The bead seat area on a tubeless tire is critical and using a too-narrow rim may result in leakage or complete unseating under heavy load. This is why the Avons can be safely mounted on narrow rims. Nothing to do with profile.

I had Avon Roadriders but the rear seemed to wear out very quickly. It also "felt" too thin. I've since switched to the cNw wheels (wm3 & wm4) with Bridgetone BT45. Feels more confident when riding.

Anglophile said:

I had Avon Roadriders but the rear seemed to wear out very quickly. It also "felt" too thin. I've since switched to the cNw wheels (wm3 & wm4) with Bridgetone BT45. Feels more confident when riding.

Click to expand...

Yes, they do. They are a "universal" tyre for front or rear. Don't know if Avon still make the 4.00 x 19 which is rear fitment only and supposedly gives significantly greater life.

Danno said:

Onder said:

Has anybody installed the Avons with spoons not a tire machine? I 've never had an issue putting on
TT100s, was wondering if the modern tires are difficult or impossible to hand mount.

Click to expand...

Tube-type tires are easy. Also they are less problematic on what would be considered a too-narrow rim. The bead seat area on a tubeless tire is critical and using a too-narrow rim may result in leakage or complete unseating under heavy load. This is why the Avons can be safely mounted on narrow rims. Nothing to do with profile.

Click to expand...

Correct profile has everything to do with contact patch and handling though.

Fullauto said:

Danno said:

Onder said:

Has anybody installed the Avons with spoons not a tire machine? I 've never had an issue putting on
TT100s, was wondering if the modern tires are difficult or impossible to hand mount.

Click to expand...

Tube-type tires are easy. Also they are less problematic on what would be considered a too-narrow rim. The bead seat area on a tubeless tire is critical and using a too-narrow rim may result in leakage or complete unseating under heavy load. This is why the Avons can be safely mounted on narrow rims. Nothing to do with profile.

Click to expand...

Correct profile has everything to do with contact patch and handling though.

Click to expand...

I agree 100%. I always say what you can get away with is not always what you should do.

Tube-type tires are easy. Also they are less problematic on what would be considered a too-narrow rim. The bead seat area on a tubeless tire is critical and using a too-narrow rim may result in leakage or complete unseating under heavy load. This is why the Avons can be safely mounted on narrow rims. Nothing to do with profile.[/quote]

Correct profile has everything to do with contact patch and handling though.[/quote]

I agree 100%. I always say what you can get away with is not always what you should do.[/quote]


Ha!! You're a Norton owner!!

Fullauto said:

Tube-type tires are easy. Also they are less problematic on what would be considered a too-narrow rim. The bead seat area on a tubeless tire is critical and using a too-narrow rim may result in leakage or complete unseating under heavy load. This is why the Avons can be safely mounted on narrow rims. Nothing to do with profile.

Click to expand...

Correct profile has everything to do with contact patch and handling though.[/quote]

I agree 100%. I always say what you can get away with is not always what you should do.[/quote]


Ha!! You're a Norton owner!![/quote]

Since 1973. I'm well aware of the size limitations we're dealing with. The 4.00 x 18 rear tire I'm now running is just about as large as you can go before swingarm conflict.

I use the very same rim and tire combo that Fullauto uses. In fact I took his recommendation to use this set up. The rear tire wears quicker with the universal and that is the nature of the beast. I switch the front tire to the rear and place a new skin to the front which gives me one new tire change when I reach the wear limit on the rear tire. Its a little more work but you can clean spokes and inspect the tension, re grease the speedo-gearbox, etc. as a preventive maintenance inspection. I have put over 30,000 miles on my workhorse 850 using this combo.
Cheers,
Thomas
CNN

I found a link that explains some of the dynamics of rim and tire choices pretty simply and clearly. http://sportbike.natkd.com/tires.htm

I also went to Avon's website to look at the chart with all the models of bikes, along with their respective rim specifications and the recommended tire sizes for each model.... Of course the rim sizes listed for the yamaha tires I am adapting for my commando are WRONG, so why would the tire sizes they reccommend be correct...? (story of my life, there's always at least one extra hurdle to jump)

These pictures are from my Commando with 100/90-19 Roadrunners on stock WM2 rims front and rear. They handle really well, and both my grandson and I like the way it drops into turns so easily. As Fullauto said, you do end up with large chicken strips at the edge of the tire. These pics are from a bike that has ground the rubber off the ends of both footpegs, and that's as far as you can safely lean it. I thought about putting folding pegs on, but I like the idea of having a soft limiter like the rubber.





Ken

Thanks for all the responses.

Fullauto and others who have used the Roadriders, what mileage do you get from the rear tire?

Ed

Good question, Ed! Normally, I would get about 4000 miles out of the rear. But that's after it's already done the same mileage on the front. So, I go through one tyre in 4000 miles. My current tyres are over four and a half years old and are looking pretty good after 3500 miles. Maybe because of the age related hardness?