FWIW, there are actually two parts to the "safety rim" design, which the web
site Joe identified does not clearly distinguish.
The "dropped center" has been standard design for many years, possibly even
since before Triumph started building motor cars. (FT : Does your Model A have
dropped centers ?)
To be a "safety rim", the wheel must also have two ridges near the outer edges
where the tire bead seats. The diagram on the web site has arrows to these,
but the ridges don't show clearly. This modification was invented sometime in
the mid-1960s, and was primarily intended to keep the tire from coming off the
rim in a "run-flat" situation. I believe it became a US DOT requirement
sometime in the early 1970s.
In any case, neither disc nor wire wheels used on TR2/3/4 were "safety rims".
I'm not certain, but believe I have two TR6 disc wheels that don't have the
ridges either.
Randall
59 TR3A daily driver - with TR6 rims and no tubes
Joe Flake wrote:
>
> Also, earlier on, someone mentioned that some wire wheels
> might not be suitable for tubeless tires since they weren't
> of the "safety rim" design. I didn't know what that meant
> and did a search. Found:
> www.autosite.com/garage/subsys/bawheelb.asp
> The photo/diagram link shows it pretty well.
> My 72 spoke rims are of this design; I assume it's only
> the older 48 or 60 spoke wheels which don't have the
> "safety rim" design.
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