fz77

Hello, I've started building a new rear wheel in an attempt to replace my old one on a 2014 REI Novara Buzz
Parts:
Rear hub: Shimano Deore XT
Rim: Velocity USA Atlas 700c
Spokes: DT Swiss, Steel, 2.0mm x 294mm (non-drive side)
DT Swiss, Steel, 1.6mm x 291mm (drive side)
Nipples: DT Swiss, brass, 2.0mm x 15mm


When I ordered the spokes I wasn't able to purchase the two sizes I needed from the same supplier. When ordering the second set I tried to match the specs closely as possible, but the description said "2.0/1.6mm" - well I ended up with the 1.6mm spoke. I decided to go ahead and use it anyway.
I didn't run into any problems lacing the wheel, but when I tried to true the wheel I couldn't quite get it to straighten out, no matter how much I tightened the spokes. What ultimately happened was one of the nipples failed, cracked at the rim and stripped on the eyelet side.
The recommended tension for the rim is 130kgf. Before attempting to true the wheel I tensioned it first, the non-drive side was at about 110, the drive at about 140.
I figure the two different sizes of spoke is an issue, and obviously the fact that the two sides were unequally tensioned was a reason why the rim failed.
Going forward do I need to remove all the spokes and completely start over, and if not how do I ensure this doesn't happen a second time?

BTinNYC 

I'm an amateur, but my method is to tighten all the spokes in stages, and roughly true the wheel at each stage.
I like to start with all nipples at the same level, say, with 3 spoke threads exposed. Then all the nipples get the same number of turns, just a few, until the wheel is tightening up. Then it's true and tighten, repeated.

maddog34

huh.. i just looked at the DT website.. they don't make a straight gauge "1.6mm" spoke... I'd suspect what you bought is actually a 1.8/1.6mm Butted spoke... Are the ends slightly larger than the middles?
One other thing i noticed.. have you test fit that hub to your frame? it may be too wide of an O.L.D. to fit.... Your frame may be 130mm between the dropouts, whereas an XT hub of disc type design will almost ALWAYS be a `135mm O.L.D., or wider.
(O.L.D. is the Outside Locknut Distance, or Width of the axle setup as it relates to the frame...)

tFUnK

Assuming this is a freehub wheel, the drive side is supposed to have a higher tension than the non-drive side due to the dish.

Russ Roth

140kgf is too much, it isn't a balance of the two spokes but the highest tension shouldn't exceed 130kgf. Breaking of brass nipples can suggest a couple things since it doesn't happen easily building a wheel. Use lube between the nipple and the rim, this will allow the nipple to turn without stripping. Also, are you certain your tensiometer is accurate? Even the Park gives a generalized generic reading based on the average of what the springs they use should produce, the cheaper ones are even less accurate. As to building
First I'd get the right spokes, trying to balance the spokes with 2.0 on the non-drive side side and a lightweight 2.0/1.6 spoke on the drive isn't going to be an easy one to balance. If the sides were reversed, they'd be great.
When I build a wheel, I lace the spokes and set the spoke nipples so that they just cover the threads, at that point I start tightening the drive side spokes in half turns all the way around till the wheel is close to dished and generally straight. Once this is done I check the spoke tension and make sure the drive side spokes are all the same, then do the same for the non-drive side. Then I start tightening all the spokes in 1/4 turns for a couple of times around the rim. At this point i should be about 80% tight. Now I make sure the wheel is straight, then round, then dished before finalizing the tension. Finish by stressing the wheel, I put the wheel on the floor and lightly push down around the sides but you can also just grab spokes from opposite sides of the hub and squeeze towards each other, either works fine and then fine tune the true if anything pinged and the rim moved any. With practice, should take 45-60 min from start to finish per wheel.

ThermionicScott 

130kgf is the maximum recommended tension for that rim. Back off the tensions a bunch and work on getting the wheel straight and centered.

FBinNY 

FWIW

There are no 1.6mm spokes, for the simple reason that there are no 1.6mm nipples.

So, your 1.6mm spokes must be double butted to either 1.8 or 2.0mm at the threaded end.

In any the different gauges aren't the problem. Plainly put tension is tension, independent of gauge. So 140kgf is 140kgf regardless of which spoke was used.

Not meaning to insult you, but you need to get back to basics and accept that your problems trace back to your technique.

KCT1986

Your tension is much too high. Unless you are building a low spoke count wheel, or planning to have a heavy load on the bike, even 130 Kfg is very high. Most wheels are built closer to 110 Kfg in the drive side max.

Also, your NDS tension seems to be much higher than what it would be to properly dish the wheel. For MTB wheels the NDS is usually in the 60% range of the DS tension. So, if DS is about 110 Kfg, NDS would be in the 65Kfg range.

Unless you have a special need to have such high tensions, it is not needed.

Are you using the standard 3 cross lacing?

Your spokes are probably what you expected, (2.0/1.6 butted). If the threaded end was smaller, you probably would have had problems with the nipples not engaging properly and stripping before reaching such a high tension.

fishboat

Tensions are waaay too high, though with an inexpensive tension meter you'd be hard pressed to measure that high, reliably/accurately, so it's hard to say where you're at. You need to back the tension off what you have (slowly all the way around..maybe 1 turn/spoke at a time) and start over. Having the wheel true and dished correctly happens as you build the wheel(as you begin the tension-up process), not after you've reached full tension.

This is a good, easy to follow guide:
https://www.wheelpro.co.uk/wheelbuilding/book.php

Start over.

Trakhak

That's an unfortunate combination: heavier gauge on the non-drive side, lighter on the drive side. Properly tensioned dished rear wheels, as noted in an earlier post, always have lower tension on the non-drive-side spokes. Therefore, considering that you want the wheel to last as long as possible, you should consider writing off the spokes you've bought and getting a light set for the non-drive side and a heavier set for the drive side.

"2.0/1.6mm" means that they are double-butted spokes---2.0 gauge at the ends, 1.6 gauge in the thinner middle section.

As noted in another earlier post, 130kgf is not the recommended tension for the rim; it's the maximum tension that the manufacturer believes is safe. Lower tension than the recommended maximum is better, generally speaking, assuming that the spokes end up within their recommended range of tension. Some wheel builders like to use light-gauge spokes even with heavy-duty rims, with no deleterious effects on wheel longevity I'm aware of.

Many wheel builders prefer to use two different sizes of spokes, with the lighter-gauge spokes on the non-drive side. That way, each set of spokes should end up within its recommended tension range. Heavy spokes on the non-drive side can fatigue prematurely as a consequence of being below their optimal tension range.

Also, you say that "the rim failed" - that's a vague description. If you mean that the rim is now unusable, throw it away and buy a new rim.

And get at least one new set of spokes, for the non-drive side. The same gauge as the drive side (2.0 by 1.6) would be fine, but if you can get lighter-gauge spokes for the non-drive side, that should be even better.

As noted several times in earlier posts, after lubricating the spoke threads and beginning the build, begin correcting the wheel's roundness and trueness and its dish while bringing the tension up slowly. The higher the tension, the more difficult it is to make corrections. The wheel should be nearly perfect in all dimensions before it approaches full tension.

One technique many of us employ is to maintain the dish while tensioning the wheel such that the rim is slightly off-set to the drive side while approaching the wheel's final tension. That way, the final step is tightening the non-drive-side spokes to pull the rim into perfect dish. Since those spokes will always be at lower tension than the drive-side spokes, it's much easier to do the final dishing with those spokes than with the drive-side spokes.

Trakhak

One other consideration in building a wheel---stress-relieving the spokes. Many wheel builders bring the wheel up to nearly full tension and then apply sideways pressure to the spokes near the hub flange to get them to take a permanent straighter line from flange to rim, followed by retruing, etc.

An alternative technique that some other builders use is to bend each spoke over the flange as they insert the spoke into the hub.

The head-out spokes don't require much of a bend, but the head-in spokes should be bent over the flange a good 45 degrees or so. With this technique, the finished wheel doesn't need any subsequent stress relief.