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Wheel build. (following up on Woof’s post)...(9 posts)

Wheel build. (following up on Woof’s post)...TFerguson
Dec 9, 2003 8:50 AM
It seems, from discussions and experience, that:

1. Given decent components, the build is the most important part of a robust wheel.
2. The most important part of the build is the compromise between "round and true" and even spoke tension.
3. What determines the extent of this compromise is how "round and true" the rim is initially.
4. Therefore, the vast majority of our effort should be getting the perfect rim which is something I've never seen discussed here.

Comments?

TF
Don't agree........Len J
Dec 9, 2003 9:41 AM
having built several sets of wheels, I disagree with your hypothesis.

You say: "...the vast majority of our effort should be getting the perfect rim...." I would disagree. All's a perfect rim does is make the build easier, it is not necessary for a great build.

You say: "The most important part of the build is the compromise between "round and true" and even spoke tension." I would disagree. The most important two parts of a great build are the balance you describe and adequate & uniform stress relief. Riding buddies bring me wheels to true. In every case where the build keeps failing, the culprit is inadequate stress relief. Not setting spokes properly is a major contributor to build failure. This is why so many machine built wheels fail, stress relief (with some machine builders, not all) is an afterthought.

Just my experiencs.

Len
I agree with you to a point...TFerguson
Dec 9, 2003 1:51 PM
By stress relief you mean no spoke wind up or relieving the internal stresses of the metal.

I took the latter as a given. Grab the spokes by pairs between each tightening.

If you mean spoke wind up, I've never really found that to be a problem. I can build the wheel, and by making the spoke wrench torque in each direction the same, have it come out with no wind up. I've tried several times during and after builds to do the "lay it on the floor and press sideways" thing and I may get one little ping someplace, but generally not. I've purposely wound up a spoke and tried it to know what the ping would sound like. Note that I never use anything thinner than DB 14/15 spokes.

So with , I believe, both of those in hand, my worst problem is the compromise.

TF
It may be a given, but..........Len J
Dec 9, 2003 5:29 PM
it is the leading cause of bad builds.

By stress relief, I am mainly tlaking about both "setting" the spoke in the hub and relieving internal stresses. I haven't had problems with wind up (maybe because I concentrate so much on stress relief. This "setting" the spoke in the hub ensurese that the tension you build into the wheel is not reduced as the spoke sets when you ride it.

As I say, you may take this for granted, but it's the cause of build failures more often then not.

Len
Stress relief won't make a bad wheel goodCarbonTi
Dec 9, 2003 7:21 PM
I think the characteristic that makes a good wheel is moderately high, evenly distributed tension across the wheel. A poorly built wheel hasn't the same. Simple as that.

I agree that stress relief will settle the tension forces acting on the wheel components from its being built. It's possible to wind uneven tension into a wheel and have it round and true after stress relief. A tensiometer or notes from plucking adjacent spokes will verify this. These are the wheels that look straight on the bench but won't stay true after being ridden a while.

A wheel also has to withstand the forces that act on it when its being ridden and for that you need even tension across the wheel.
I also use a spoke punch to set the heads. (nm)TFerguson
Dec 10, 2003 8:33 AM
Rims can make builds easy or tough...CarbonTi
Dec 9, 2003 10:20 AM
A bad rim starts you off in the penalty box.

Rim quality can vary from brand to brand and even from the same maker. I have found it to be basically a crap shoot as far as consistency of roundness, especially at the seam where the rim is joined.

One bad scenario is when the rim has a slight flat spot manufactured somehwere on the rim. So right out of the box you have uneven tensions to compensate in working the flat spot to get to acceptable round. Another is when the rim has a slight lateral misalignment right at the rim seam.

Both force uneven tensions into the wheel to get to round and true even before you start to wind tension into the wheel. I've built with Mavic, FIR, Ambrosio, Velocity, IRD and Zipp rims. I have had the best luck, consistency-wise, with Ambrosio. The worst luck with Mavic. Zipps pop out of the mold perfectly round and true but for what they cost, they'd better.

You can get a good workable wheel out of a bad rim, just takes more time - nice chromatic scale when you pluck the spokes!
Your right but.....jhr
Dec 9, 2003 12:34 PM
How do you determine if a rim is perfect, or even very good, without building it? Unless a rim is way out (so far out you can see it just by laying it on a flat surface) how do you know without building it. A big stiff aero rim also seems to build easier than a wimpy lightweight rim.

Anybody know how to test or measure a rim before building it up?

My experience is that Fir rims build up the easiest, therefore I perceive they are the straightest in general. However, I have only built with a couple of different rims in the last 5 years (Fir, Ritchey, Mavic, Velomax).

jhr
In theory...torquecal
Dec 9, 2003 5:38 PM
you could take a big enough caliper or outside mike and take a number of diameter measurements around the rim prior to build. I've seen .001 resolution tools big enough to do it.