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Wheel numbers/letters?

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I am in search of knowledge:

I have wheels marked 4 1/2 J x 13 H1   or H2   or just 13.  What do the letters mean, particularly the H1, H2 or no H?  Thank you. P

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“H” signifies “single hump”, “H2” signifies “double hump”. These humps are...humps on the rim’s barrel, just inboard of the outer lip. The humps serve to keep the tire from slipping inward and breaking its bead under hard cornering or other severe conditions.


The German TUV, by some time in the mid-1970’s, was requiring rims that were NOT double hump (a.k.a., H2) to utilize inner tubes with all tires. The tube, of course, would keep the tire supported if it broke its bead at the rim’s lip. I don’t know precisely when the German TUV began to focus on this particular wheel safety issue, but it appears to have been a driving force in the specifications of rims from 1970’s. The OEM rims were generally the first converted to H2 specifications — the early OEM alloy rim, introduced in 1971, was an H2 design — followed by aftermarket rims. I haven’t seen a double-hump Borrani (CMR) rim dated before 1979, so German-resident users of rims such as these were forced to use inner tubes through the ‘70’s.








Edited by Conserv

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Tubeless tires needed to be humped twice!  If the tire bead slipped away from the bead it will loose the air.  Tube tires aren't affected the same.

It would be very exciting in a hard corner loosing the air and flop, flop, flop.

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