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Modern tyres on 1970s rims

Post Tue Feb 02, 2016 3:18 am

Posts: 1654
Getting a bit further into the XLCH project, I have come against an issue which I once knew about but had forgotten - tyres.

The blue XLCH has an original back wheel with a perished, rotten Goodyear All Traction still in place. The question is, what modern tyres (if any) fit this rim?

As far as I can see, the rim is a CM profile rather than the usual WM profile. The Goodyear A-T is long gone (which I don't regard as any great loss) and there are no modern tyres marketed as fitting CM rims. I do have a set of Dunlop K70 originally intended for the Ariel bike, which are the right load rating for an ironhead (64S on the rear) provided they fit the rims.

So far, I've collected one thread from Jockey Journal setting out in a fair amount of detail, why modern tyres shouldn't be used with these rims, plus a thread on the XL Forum which has rather strayed into the predictable "Hell, yeah!" territory. There are the well-known issues from the MoCo about not using them, compromised by their obvious commercial interest. There are modern tyres that post-date these rims.

So, the question is; are any modern tyres rated to be used with the CM rim?
Shoot, a man could have a good weekend in Dallas with all that stuff...

Post Wed Feb 03, 2016 2:48 am

Posts: 30
I run the rear 4.00 x 18 K70's on my 741B same tyre front and back. They look great and handle very well. I used to push that bike hard on our twisty mountain roads(75mph for the little 741), all weather. No problems. A popular tyre here in NZ.

Post Thu Feb 04, 2016 9:00 am

Posts: 1676
Location: Interlaken, NY USA

I run the aluminum 19" sporty rim of that type on the front of my Panhead, and have for years with any variety of modern tires. I'm using the Michelin commander II presently. About 2 years ago I had a quick flat on the front just as I entered the turn off the main road to my secondary road I live on at approx 35mph. Tire stayed on the bead and otherwise performed as the rim was designed to do. It was a scary but not dangerous situation. Rode it the 400yds to my driveway uneventfully. (at 5mph, granted).
Bottom line, in my experience, under normal circumstances tires fit and go round and round, and if you get a flat, they don't go all flippy floppy like a regular rim. (sorry for those technical terms there)
Memory being what it is, I can't guarantee I was running the Michelin at the time, it could have been a Chen-Chin at the time(back before I got smart about tires after hydroplaning one too many times). But I don't think that makes my experience any less valid. If anything, the Michelin are a tighter fitting bead than most tires of any given size, and would be better proposition on the rims in question.

Post Thu Feb 04, 2016 2:37 pm

Posts: 1654
The front rim isn't the issue, bike has a steel rim.

Unfortunately the Michelin tyres (Commander and Marathon) don't come in a suitable size, the 18" rear rim seems to be going the way of the 19"

Avon RoadRiders seem to be the preferred choice. The Cobras on my Evo Sportster are a very tight fit, and the AM26 has a 4:00x18" size
Shoot, a man could have a good weekend in Dallas with all that stuff...

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