AGuinness

Hi everyone,

I have a strange problem. About six months I built some track wheels by lacing some Sun M14A rims to a pair of 36 hole low-flange Gipiemme Special Pista hubs 3X, using DT Competition spokes. I used this website: https://spokeanwheel.110mb.com/ to calculate spoke length by filling in the formula provided with the rim ERD and the hub measurements explained (I used Vernier measuring calipers). The numbers I came up with were 295.5 (I rounded down to 295) for front wheel, 295.6 (also rounded down to 295) for rear non-drive side and 294 for rear drive side.

I tensioned the front wheel and rear drive side to about 100 kg, rear non-drive I think was about 60 kg or so. Anyway, I rode the wheels for a good while without any problems, until I noticed that they were a little out of true (most likely due to occationally forgetting to maintain adequate tire pressure and then riding over the numerous potholes in this city) and decided to re-true them and also bring the spoke tension up a bit (after reading here and in books about how high tension adds longevity and helps to prevent wheel from going out of true, etc, etc).

I was able to bring the front wheel up to about 130 kg (I use a Wheelsmith tensiometer, btw. Average reading of 60) without any problem. However, when I tried to bring the rear drive side spokes up to about 160-180 kg, the spokes extended quite far beyond the nipple head (about 3-5 mm) almost touching the rim tape, and I was forced to reduce the tension.

I'm not sure exactly what happened here. Did I make a mistake by rounding non-drive spokes (didn't have any problem with these) down to 295? What is the relation of ERD to spoke length? Are the spokes supposed to end up flush with the nipple head? What did I do wrong?

Thanks everyone

AEO

does this rear wheel have any dishing?

operator

What you did wrong?

Overtension and probably tension variation. "Normal" tension range for a front 32/36h on a regular hub with straight gauge spokes/double butted is 100kgf for front, and 120kgf for rear drive. 160-180 = stripping nipples = reduced spoke life = fail wheel. There is no problem with your spoke length rounding.

Did you

1) Stress relieve
2) Tension normalize +/- 20% variation at MOST. Smaller the better.
3) Bend the spokes at their crossing?

Whoever you read from that said higher tension increases spoke length is wrong and is an idiot. The best spoke life is achieved by the *minimum* spoke tension necessary for the wheel to stay in true in use.

Torchy McFlux

Pretty much.
Should have used this:
https://www.dtswiss.com/SpokesCalc/We...px?language=en

operator

That spoke calculator blows ass. Especially since they removed all non dt hubs from their DB. Use spocalc and measure everything yourself. Unless you make a measuring or data entry error, spocalc will always be right.

AGuinness

The hub does have dish of course, otherwise formula would have given me the same number for both sides, however it is very little as it is only for a cog and lockring. Also, I did stress relieve, after every round of truing. I guess it's just too much tension.

Now that I think about it though, I think I brought up the front wheel tension to an average reading of 70 on my tensiometer, which is about 130 kg. I was under the impression that tension on the drive side is usually a little bit higher than tension on the front spokes, which is why I was trying to get 180. I know, the difference is huge (50 kg) — I should have thought of that. However, even down at 130 the spokes extend beyond the nipple head.

The only book I have on wheelbuilding is Schraner's, which does not have very much info though his lacing method is neat. He does mention that high spoke tension results in a more durable wheel. I didn't mean to say extremely high tension or anything, just high tension.

Wheelbuilders — have you ever had any problems with spoke length due to high tension? On a finished wheel, using the spoke calculation systems available, have you noticed spokes extending beyond the nipple head? Do you use spokes a couple mm shorter than those recommended?

Thanks

operator

**** stupid subjective terms like "high tension". Tension has a quantiative measurement, that's a ****ing number. If that's a direct quote from schraner he's wrong. And you should throw his book into a fireplace. If you've measured everything accurately and want to have a a to b wheelbuild, spoke lengths are +/- 1mm.

LarDasse74

You need to calm down a bit, there, buddy.

mrrabbit 

Actually I like Operator worked up...so back off party pooper.




To the OP:

100-110 kgf is all you need for most front alloy wheels...

110-115 kgf drive side rear is a good starting point for 6/7/8/9/10/11 speed rears.

You were really pushing it dude...

AEO

I'm actually surprised the rim didn't crack.

Jeff Wills

No to all of the above. I've used the Spocalc spreadsheet for years and it's been spot on every time, even with my whackdoodle wheels.

AGuinness

Great. Thanks everyone for your help, really appreciate it.

That's what this is here for, right?