Wheel building: disc wheel tension differential

[foo_fighter]

Seeking the collective advice of the wheel pros here.

What are the typical tension differentials on a front disc wheel? I'm getting 10/15 on the TM-1 which according to the chart for CX-Rays is 74/119 Kgf. Is that pretty typical? One is a CLD11 hub and the other a DT350, both centerlock.

Second, what tolerance do you guys strive for roundness. Of the 2 front wheels I've built the valve side is typically a bit shorter than the joint side(the joint side rubs first). I see about 1-1.5mm difference, but all of the spokes are very balanced for tension, so if I try to reduce the gap, it'll have to be at the expensive of even tension all around.

[ergott]

Not right. You want even tension and round barring any local hops that would effect tension to address. If your wheel is overall high on one side and low on the opposite, tension the high side half a turn or so and loosen low side half turn or so. Do quarter turns when you are closer to getting it right.

Tension left to right depends on hub. Just make sure side with higher tension is where it should be and each side is even with itself. I don't measure the other side because it's moot. The spoke calculator will give you the answer in percentage of high side if you are concerned with the geometry of the hub.

[oldpotatoe]

Not right. You want even tension and round barring any local hops that would effect tension to address. If your wheel is overall high on one side and low on the opposite, tension the high side half a turn or so and loosen low side half turn or so. Do quarter turns when you are closer to getting it right.

Tension left to right depends on hub. Just make sure side with higher tension is where it should be and each side is even with itself. I don't measure the other side because it's moot. The spoke calculator will give you the answer in percentage of high side if you are concerned with the geometry of the hub.

Disc wheel so rotor side is like cassette side of rear(flange closer to centerline of hub) and will have higher tension than the non rotor side. So, yes, I'd say about typical for a disc brake front hub.

As for roundness and a disc wheel..even tension is key, and enough and even keeps the wheel true. Often if the wheel is not round, the tension is not even..but if the tension is even, and the rim not round, I'd say a not well made rim and strive for even tension..on a disc wheel, no rim brake, not a big deal.

[d_man16]

Thanks Eric...I've always checked both sides, I have no idea why I've never thought of this ;)
~D

[Hermes_Alex]

In practice, about .3mm of roundness tolerance while keeping tension spec really tight is doable with better rims. With crappier ones, about .4-.5mm.

[foo_fighter]

I will try to get it rounder and see how that affects the tension balance. I think the readings are all within 0.25 of 15 on the meter on the disc side and about the same tolerance to 10 on the non-disc side. A gap of 1mm between high and low is really a tolerance of 0.5mm.

[ergott]

±0.5mm is higher that I would prefer. I assume you are talking about a gradual swing from -0.5mm at one end to +0.5mm at the opposite end. When you tighten one side and let up the other you will still end up with even tension in that case. If you are talking about a low spot at the joint, some rims are worse than others. Still should be better than ±0.5mm or there might be a dent in the hook.

[foo_fighter]

I was able to reduce the error and you're right, the tension balance wasn't affected much. On one rim, there is a consistent gap all around and then right at the joint there is a low spot. I gave up on that one. On the second one, I was able to reduce it to about +/-0.25mm, then I called it good.


±0.5mm is higher that I would prefer. I assume you are talking about a gradual swing from -0.5mm at one end to +0.5mm at the opposite end. When you tighten one side and let up the other you will still end up with even tension in that case. If you are talking about a low spot at the joint, some rims are worse than others. Still should be better than ±0.5mm or there might be a dent in the hook.