Type rims? and tires

gortnipper said:

Not sure what the "91 0033" stamp means. It doesnt follow a date stamp format that is normal for other things I am familiar with in that era (tubes/valves, Garrard turntables, etc) , but may be a batch code. Dunno.

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Most likely the Jones part number, similar to the Dunlop (MB41, MC275, MC286, etc.) rim ID code numbers.

Roadriders are excellent tires...however the 100/90 universal is not recommended by Avon for the stock WM2 1.85" rim and will be visibly pinched if you mount one (but do realize many run them without incident). So far as tubes go I've had good luck with the ones Harley dealers carry, very good quality...

I'm another fan of the Avon AM26 in 100/90x19. I have them on the stock steel 2.15 rims on a MK3 (not the recommended width, but within the allowable range in the Avon specs) and love the way the bike handles. The only drawback to them that I can see is that they wear pretty fast on the rear, because the universal tires don't have as much tread depth as the ones designed for rear wheel use.

Ken

Try them on 2.5 inch rims which they are made for. Truly a revelation!

lcrken said:

I'm another fan of the Avon AM26 in 100/90x19. I have them on the stock steel 2.15 rims on a MK3 (not the recommended width, but within the allowable range in the Avon specs)

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The stock 850 Mk3 rims are WM2 which is 1.85".

My bad. I'm so used to using WM3 rims on the race bikes that I had a senior moment and let that slip right past me. I still like the way my MK3 handles with the Avons on the stock WM2 rims, but they are not within Avon's approved width range, so I can't recommend them to anyone else.

Ken

Several questions at this point. What IS the correct avon roadholder tire width for the standard stock rim that came on, say a 1974 850. Would there be a difference we could notice? Many here like the AM29 100/90-19 front and rear on stock rims. And a second trivial question (maybe for others but not for me). I just read an article about Avon's that said the rear tire should rotate in the direction of the arrows. Presumably the points of the tread pattern should be facing forward when they are at the top of the wheel. But it said they could (or maybe should)be placed to rotate in the other direction when the tire is mounted on the front! The name of the magazine writer escapes me, but I can dig it up. Any opinions or official word on any of ghis?

Avon state that the 100/90 x 19 Roadrider is made for a 2.5 inch (WM4) rim to give the designed footprint with either 2.15" or 2.75" rims as acceptable alternatives. But, they also state the same tyre as suitable for the standard 1.85" WM2 rims, which works very well. It doesn't present the most suitable profile, leaving chicken strips a mile wide, due to the mushroom effect. However, it is a great combination. However, it is not perfect. The steering is definitely heavier on the 1.85" rims which is why some go to a 90/90 x 19 for the front to lighten it up. I use 2.5" WM4 rims on both ends and have for years. People seem to shy away from this combination for some reason, but simply try it. The little Commando foibles disappear and it becomes a delight to ride. Very light in the steering, yet strangely stable, even at higher speeds. I've been playing around for years and I've been through over twenty of these tyres in that time.

The Avons are a universal tyre, which means that they are usable on front and rear, but the forces acting on front and rear tyres are different, so the tyres must be fitted with the directional arrows pointing the right way for the application. When my rear wears out, the new one goes on the front and the old front goes on the rear. Simple.

"So the tyres must be fitted with the directional arrows pointing the right way fo the application". And what is that right way?

The universal tires usually have direction indicator for front and rear i think.

Sorry fellas for the unnecessary questioning about tire rotation. I had ordered Avon Roadriders but they hadn't come yet. They're here now and low and behold there's a tire rotation fitment guide stamped on the sidewall. Feel silly, but didn't know. Learning curve and all that.

You'll really like them Joe. An excellent tyre. Some complain about tyre wear, but if you wear the rear out and put the front on the rear, you will get more useful miles out of them, because they barely wear on the front.

The wear complaints about universals is due to tread depth. Univsersal tyres have a shallower tread than a dedicated rear (5.6mm versus 7.5mm), thus the rear wears down to the min faster as you’re starting out with less depth.

It’s a small price to pay for good tyres though IMHO.

When it comes to the time for new rims, you could fit an 18”rear. If you look at the choices in the table posted above, you can get 18”rear and 19” front with the same rolling radius, thus negating the argument by some that 18” rear wheels adversely effect geometry etc.

I’m with Fullauto 100%, these are my ‘standard’ tyres on all my classic bikes, even ones I use on track days etc. They are very confidence inspiring. If you go to a vintage race meeting you’ll see guys racing on them, and going far quicker than you ever will on the road.

Fullauto said:

You'll really like them Joe. An excellent tyre. Some complain about tyre wear, but if you wear the rear out and put the front on the rear, you will get more useful miles out of them, because they barely wear on the front.

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Sorry Nigel. I have to call "furphy" on the whole 18" rim thing. They still perpetuate all the funny little quirks that Nortons have. The wide 19' rims gets rid of them with a stability and confidence I've never felt in any other Commando.

How do they do that Ken? Rolling radius is the same, widths are the same or wider. What magic effect am I missing?

Fast Eddie said:

How do they do that Ken? Rolling radius is the same, widths are the same or wider. What magic effect am I missing?

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Nigel,
Side wall height is increased by 1/2”, perhaps that changes the way the tire behaves. Probably not as stiff as a shorter side wall. A 1/2” on the side wall might have more affect than .030” of bead width (.185” vs .215”)
Pete

I can’t see that being an issue Pete, but I’m not a tyre expert!

Out of interest, I wrote to Avon with this question today and will update when they answer.

All that follows comes under the question of "how much difference would I notice?" I've gotten the 100/90-19 Roadriders but have the WM2 rims. I could keep the one as a spare and get a 90/90-19 for the front -- no problem there. But the question is since Avon does not fully endorse the 100/90-19 for the WM2 rim, which I have on both ends, wouldn't it be better to have front And rear 90/90-19? Also, Fullauto talks about using WM4 rims. And that sounds pretty interesting. Now I have successfully built (laced) my own bicycle wheels and trued them, but Would not attempt motorcycle wheels without very expert backing. There has to be a significant cost to buying a pair of these with WM4 rims, especially if you don't want to strip your original hubs.

The most important lesson you have to learn with these bikes, is learning to draw the line somewhere...

I speak from experience, I took the head off of my perfectly OK, recently purchased, 850 MK2A in winter 2013 just to ‘have a look’. It led to a seemingly endless OCD driven consumption of time and money!

I’m quite sure that if you fit what you have, you’ll be perfectly happy and get a lot of enjoyment out of it.

Start stripping it to fit new rims etc and goodness knows where it will end!

I'm with Nigel here, Joe. It seems like the 100/90 Avons should work better on wider rims, but in the real world, I'm not sure you would notice the difference. I've been riding with them for a long time on stock WM2 rims, as have many others here on the forum, and they work just fine. And they get ridden very hard on occasion. I like the way the bike handles with them. It is very neutral feeling in corners. It falls into corners very easily, holds it's line properly, and doesn't push coming out under power. What more could I ask for on a street bike, except maybe better mileage on the rear?

As far as using the 90/90 on the front, I don't know what benefit you would gain from that. It would certainly work. I've seen a couple of Commandos with that combination, just never tried it myself. I raced several Commandos back in the day, and all had smaller front and larger rear tires. In fact my first race bike, a Commando PR came from the factory with 4.10x19" rear and 3.60x19" front.

Having said all that, if I were replacing the rims anyhow, and wanted to stay with the 19" size, I would go with the wider rims (in alloy, of course!). I can't see any drawbacks to following the manufacturer's recommendations.

Ken