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Old 08-18-2011, 11:36 AM
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Jerry Jerry is offline
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Join Date: Jun 2002
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As has been noted (and has been on prevous threads on this topic) the profile at the side of the rim, where the tire bead meets the side of the rim, is different between the tube and tubeless rims.

There is also a difference in the construction of the tire. Tubeless tires tend to have lighter and more flexible sidewalls, and often have reduced rolling resistance when compared to a tube-type tire of otherwise equal specifications. The bead area is, most often, constructed differently between the two styles. Tubeless tires tend to have more reinforcement material in the bead area.

The danger of using tubeless tires on tube-type rims (other than sealing the rim lock holes) is that in low-pressure situations the tubeless tire on a tube-type rim is more likely to break the bead between the tire and rim.

Think about that for a moment, and consider that if you get a puncture in a tubelss tire on a tubeless rim, the tire is more likely to stay beaded and let you come to a controlled stop. The same tubeless tire on a tube rim may suddenly dis-bead and flop from side to side, making an otherwise controllable stop into a white knuckle affair.

I guess the question is, "Do you feel lucky?" Best bet, from a safety perspective, is to to use the suggested combination: tubes in rims not marked as suitable for tubeless tires, and tubeless on those rims that are marked for tubeless use. Sure, you can do otherwise, but understand there are additional safety risks in doing so.

Short history note:

Tubeless tires were first marketed for cars in the mid-to-late '40s, and by then most manufacturers were promoting "safety" rims suitable for tubeless tire use. Tubeless tires came much later to foreign cars, motorcycles, and other modes of transportation. When it did, those manufacturers followed the same path as the auto manufactuers had taken and began equipping vehicles with the "safety" rims. (Sometimes called the J-rim.)

"They originally had a J designation stamped on them to signify they had a single 'safety' bead, the aim of which was to retain the tire on the rim if it deflated. These rims have a visible raised bead near the lip that the tyre 'pops' over to seal against the rim edge. They will have stamping something like ROH 14J 5 (or similar) which will be the manufacturer, diameter, J for safety and then the rim width. With the use of tubeless radials they went to double safety beads, I think in the 70s (?) with are designated JJ (e.g. ROH 14JJ 5) which have the raised safety bead on each side of the rim. Most build standards now require JJ rims."

Have a good day!
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