----- Original Message ----- From: <Wornoutguy@aol.com>
> I picked up two Hi - E front hubs one is a 20 and the other 24 - the
twenty
> four was already laced to a matrix rim with no eyelets (bladed DT spokes
> radially laced) a couple of the spoke holes were cracked severely and
when I went to take it apart they pulled right through. I assumed this was
from too much spoke tension???????
>
Probably not. For one, the early Matrix rims were known for cracking
problems, so that could contribute. Secondly, low-spoke-count wheels "then"
were not what they are now. From the peroid that wheel is likely from, these
types of wheels were considered very limited use items. Mostly track and
special climbing events. The tension necessary to have a strong wheel with
those low counts is too much for rims of standard designs and weight if you
want any durability. Most current low count wheels use rims that are much
stiffer radially (and heavier), sometimes stiffer tortionally, and also
often have special nipple interfaces and rim designs that spread the load
over more surface area. Both rims and spokes (often 13g ends) will handle
more tension, and the stiffer rim will make the wheel stronger and more
durable, even if all else is equal.
> I built up the 20 hole and the rim is the same type I put just enough
tension
> to get the rim straight and true. My question is how much tension does a
low spoke count radially laced spoke require??
>
That's a judgment call based on many variables, but the easy answer is; more than that arrangement can handle. That rim is probably a fairly shallow aero rim, of around 400-420 grams. As a normal design rim, it simply is not going to be stiff enough or strong enough to be a good wheel. If you leave the tension low, there's an increased chance the wheel could just buckle, under the right load or circumstance, and spoke fatigue life will be poor. If you tension it enough to make a strong wheel (strength and durability are not the same), it will still be usable to a limited extent (you didn't mention your weight or intended use), but localized rim stress will eventually cause the same failures you have now in the rear wheel.
In short, at best it's a very limited use wheel, or get a heftier rim. Relacing with spoke washers would help a little, but that's really just turd polishing. It's just not a combination of parts that can be made to work like current stuff. They're OT, but I think you can get Velocity Deep V's in 20ยบ.
Jon Schaer
Columbus, OH