Wheel Build
 

In building a new wheel is it improbable to expect uniform spoke tension around the wheel? I have heard that in using a tensiometer, one should find the average tension of the wheel and then conduct relative tension measurements. If these fall within 20% of the average then the wheel is considered solid. Is this way off the mark or an adequate guideline? Thanks

It's unrealistic to expect all of the spokes to have the exact same tension when the wheel is round and true.

Plus or minus 20%, however, sounds like a lot of variation to me. I'm thinking that, assuming you're using a decent quality rim, plus or minus 10% should be plenty.

I'd concur with the 10% figure. It's quite possible to have a spoke or two that won't cooperate, but the average should be within this amount.

I agree with Panthers007 comments. I use a tensionmeter and have trued many wheels with it BUT if the tension falls out of these specs, it means the wheel is bent BUT still usable, just with different spoke tensions. Then if you break too many spokes, you detension the wheel, use new spokes and try to bring it back but usually this won't work and you have to get a new rim and new spokes.

The more even the tension, the stronger the wheel. Aim for perfection, but you'll likely have to tweak a spoke or 2.

It is completely unrealistic to expect that a wheel will have uniform tension all around. The range of "acceptable" deviation is dependent on the quality of the wheelbuilder and the quality of the parts. If all the parts were perfectly made, then theoretically all you need to do is bring every spoke up to the exact same tension and the wheel would be perfectly radially and laterally true.

This is obviously not the case. Ever. The higher quality the parts, the less of a standard deviation from the average spoke tension there will be. Which means, a more durable wheel. Now somebody throw out some figures for acceptable tension on a handbuilt wheel with quality parts. I'm going to say +/- 15kgf.

numbers thrown
 

Acceptable is completely subjective, but that won't stop me from throwing out some numbers. On the last front wheel I built using a 32 h XT hub and Ambrosio Nojo rim and Wheelsmith 2.0g spokes, I got the following numbers using a Park tension meter. I used the meter carefully, releasing it slowly, and measuring each spoke two or three times until I got a consistent reading.
(On a Park meter, 25=121 kgf, 26=137 kg, and 27=156 kgf.)
Drive side highest tension=26.2
Drive side lowest tension=25.10
Drive side average tension of all 16 spokes=25.62
Non-drive side highest tension=26.80
Non-drive side lowest tension=25.15
Non-drive side average tension=25.56

This resulted in a wheel that was perfectly laterally true, at least visually. Only the slightest whisper of contact would be heard from the rim contacting the calipers of a Park truing stand. I haven't had a chance to use this wheel to see how it stands up to it's intended purpose-rolling down the road carrying my weight.

I'd like to hear your opinions on how acceptable tension variations may change between two wheels with different average tensions, say one wheel has an average tension of 100 kgf, and has a +/- of 15 kgf, compared to another wheel with an average tension of 130 kgf with the same +/- of 15 kgf.
I'd also like to learn whether there's a difference in a wheel where two adjacent crossing spokes have a +/- of 15 kgf versus a wheel where two spokes 180 degrees apart have a +- of 15 kgf. Without knowing the physics of it, my instincts would tell me to be more concerned about differences in adjacent crossing spokes.

You are correct. I'll write a more detailed reply when i'm not smashed, k thx. Bai!

Ever since the Park Tool TM-1 Tensiometer (gotta love that - right up there with their "Lazer-Cut" headset-wrenches...Baaah!) came crawling out of Minnesota, wheels that had served people more than adequately ended up in the trash. And now we have Jobst Brandt* telling aspiring wheelbuilders to just get every spoke into exact tension with every other spoke - and never mind the wheel being laterally or vertically true. As a result, I place the TM-1 alongside a bike shop that hands out spoke-wrenches to all their customers.

I see a Bad Moon Rising. Perhaps it's time to write The Wheelbuilder's Jokebook - complete with pictures of wheels resembling potato-chips on a roller-coaster. But absolutely identical tension!~~~~~~


* - Don't get me wrong. I highly respect the man and his theories. I just wouldn't let him near my bicycles.

...assuming that you have kept perfect count of how many turns you've got on each nipple...

And every hole on the hub was equidistant from the center. And the spacing of the eyelets of the rim were equidistant. And the rim itself was perfectly round. And.... Then such a claim could be made.

Real world data. Spoke position (odd = left, even = right), and tension difference from what it "should" have been:

#1 +3.9kgf
#2 -1.8
#3 -7.8
#4 +4.0
#5 +2.8
#6 +1.7
#7 -7.8
#8 -0.4
#9 +2.8
#10 +7.7
#11 -14.9
#12 +5.5
#13 +2.8
#14 -3.2
#15 +5.2
#16 -1.8
#17 +2.8
#18 +5.5
#19 -6.2
#20 +8.7
#21 -6.3
#22 -1.2
#23 +4.0
#24 -0.4
#25 -6.3
#26 +0.9
#27 +4.0
#28 +1.7
#29 +0.5
#30 +0.9
#31 -6.2
#32 -1.8

This wheel runs true. There must have been an anomaly in the rim at spoke #11 because spokes #10 through #12 are all "pulling" the rim to the right to make it true. And then, 90 degrees further, there is another similar anomaly from spoke #18 to #21.

Do keep in mind that the above numbers have limited accuracy - they work best as an average over the whole wheel. The smallest and biggest "left" side readings vary by less than 2 TM-1 marks. The max "right" side reading variation is only 1.5 marks.

EDIT: This is a MTB disc brake front wheel, hence dished but in the opposite direction of a rear wheel.

I've actually had that happen a couple of times. (well - almost) It was when I built my tandem wheels using Velocity Dyad rims. Consequently, I'm high on Dyad rims.

+1 Most of my wheels fall in the 3-5% range (I'm willing to put up with up to 1mm in favor of more even tension). I have yet to find a NEW rim that couldn't come within 10%. Used rims are a different story, and some of them just have to be tossed.

The point made about differences in quality of rims from bottom on up is pretty much true with minor exceptions...

For instance, my entry level single-wall MTB rims are the victim of very fast high volume production. The machinery responsible for rolling the rim, holding and pinning the rim joint are overly agressive. The result is that quite a few of my rims have a deviant spot near the valve hole and near the joint.

Usually they require a lot more tension to bring them in line with the rest of the spokes. So on the occasions I do check, I'll have 70, 75, 72, 70, 75...85...75,70...etc...with the bump indicating the questionable spot. (Wheelsmith meter...which I rarely use...)

However, the wheels hold up just fine.

On the other hand, if the damage spots are "weak" spots where the tensioning results in a considerable hop when finally tensioned - I toss the rim for two reasons.

1. It's ugly for a handbuilt wheel.
2. If trued in line with the others - the spoke will be loose - and break prematurely.

Now as you go up in the ranking of rims...it gets better...

However, while I normally recommend Mavic for high quality lightweight rims - I do find myself picking a bone and wagging the finger at Mavic on occasion.

A. When folks bring me Open 4 CDs, I ask them if they can to bring 3 instead of 2. Because for about every 10 Open 4s I build - 1-2 will have a weak spot at the joint. Bringing it in tension-wise just results in an ugly hop. I refuse to do that - nor will I hide it with spoke-prep. I'll hand the rim back to the customer and say, "Defective - go to the source and get a replacement." It's a hassle, but my customers appreciate it.

B. The same goes for the Mavic 819 Disc. But I would say it's a tad worse than with Open 4s.

C. Back in the early 90s, Mavic for about a year had a serious quality control issue with their 561s. Here the problem was a tad different. Before pinning the joint - they weren't cutting the ends of the material an exact 90 degrees. The result was that the joint would flare out to one side or the other about 2-3mm. This happened at a rate of about 3-4 per 10 rims. So I was constantly telling the shop I was building them for - defective - send 'em back. Trying to pull it in would only result in a severely under-tensioned spoke on the opposite side.

Funny thing was - this didn't seem to be an issue with it's narrower sister the 531.


So as another already mentioned...keep you eye out even with high quality rims. There will be exceptions.

=8-)

It really does boil down to which you believe is the greater priority - even spoke-tension, or perfectly in true & round. The absolute nirvana point is being able to achieve both. Top-drawer wheelbuilders are able to achieve this. Operator is going to scream but - I have a set of wheels built by Peter White. They are within .1mm of true and round. And the variation in tension is difficult to read on my FSA tension-gauge. It's minimal at worst.

The real keys to achieving this high-standard is practice - and patience. The latter being a concept I've found to be in short supply in our culture. 10% is certainly acceptable, and 3 to 5% is excellent. Achieving the magical 1% takes years to reach for most of us - unless we get very lucky.

Mr. Panthers007

I am sure no expert wheel smith but I have built a couple of wheel set over the years and have trued several wheels. Most of the wheels that need much work are cheap wheels. My experiance has been that decent to good wheels need minor work if any at all. I don't doubt your word that skill will produce less spoke tension variation but I don't understand why. It seems that it takes 'x' about of nipple turns to tighten and then true the rim. How can skill change the mechanics of the tight spokes and true rims with the components being of equal quality?

Hey. All of the words are in a $3.00 dictionary. Great literature is simply a matter of arrangement. Some writers are obviously better at it than others.

It's entirely possible to have a wheel that is both laterally and radially true yet still have significant spoke tension differences. I know because I've personally worked with several such wheels. That doesn't happen in a well built wheel. I think that most of the skill comes in the gradual tensioning process. Like writers, some wheelbuilders are better at it than others.

This is the crappiest and easisest to obtain on a crap built wheel. You can always get a wheel perfetcly true radially and laterally at the expense of spoke tension. That just means you have no business being an actual wheelbuilder.

In answer to your query - how does this improve where you can't see/understand the reason - it seems to just happen over time. As to how the....? does this take place, I doubt you'll find two wheelbuilders that agree. I've written it off to the last refuge of the confused: Magic.

Retro Grouch is quite right about well-built wheels hardly needing any real work. They were built correctly. Their spoke-tension is close to the mark. They are true both vertically and laterally. They were stressed/tensioned and re-trued and stressed again. So forth until there is no variation - just the mild 'sproing!' as you apply pressure to the spokes to help them settle into their new, happy home. And these wheels rarely go out of true. They don't break spokes for no good reason. They just do what you want a wheel to do - run true and straight with truly minimal attention required.

Magic?

If there is one most important thing to have when building a wheel you want to be like the above, it's: PATIENCE. Speed comes with experience. And you also find out something new: Building wheels is FUN! If it seems too stressful or frustrating, then quite possibly building wheels is not for you. No shame there. But relax and go slow and patiently. If you get hung-up and you're not feeling good - set it aside and go watch The Three Stooges or something. Return to the task at your leisure.

I have a set of brand new wheels, factory built, never been ridden, flat spokes. I checked the spoke tension with a Park Tensiometer and all the spokes have the exact same tension, the wheel is laterally and radially true with narry a bump.