Sending SOS to the PL wheelbuilders

[Broccoli Cog]

Hey all,

I'm having some frustration with some wheels I am building. This only my second set so I am very inexperienced. I am building with previously laced rims and new hubs. It's a 36 spoke 3x pattern. I am experiencing a huge dishing error on the rear wheel. I am building with the same side spokes on both sides. The calculator called for a difference of 2mm spokes between the sides but I opted to take an average of the two to build with same spoke length.

After radial and lateral truing the wheel I went to check the dish and it was massively off center by 24 to 25mm. I feel like my spoke tension is too high to go tighter. I am getting a reading on the tensiometer of 25 for reference.

What have I done wrong? Did I error on the spoke length? I had no issues lacing the wheel and starting at an even tension so I don't think that's the problem but I just can't seem to figure out how to correct such a large dishing error.

Any insight as to steps to resolve?

[Mark McM]

There's a reason that the calculations for dished wheels specify longer spokes on one side - it's because the spokes on the that side really are longer. The danger here is that if the same length spokes are used on both sides of a dished wheel, the right spokes might run out thread before they are tight enough, or the left spokes might not go deep enough into the nipple for full support.

As far as you're dishing error: The only way to produce wheel dish is for the spokes on one side to be tighter than the other - on rear wheels, the right spokes need to be up to 2 times higher tension than the left spokes. If you are tightening the right and left spokes to the same tension, the wheel will not be dished, and the rim will be centered between the flanges - but because the left flange is further from the wheel center than the right flange, the rim will be offset to the left.

To get the wheel dished, you'll have to tighten the right spokes, while at the same time loosening the left spokes. Hopefully you won't run out of threads on the too long right spokes.

[Flinch]

When tensioning you have to watch the centerline during the whole thing, especially for the rear wheel. Be sure that the nipples and spoke threads are lubricated to prevent galling and spoke wind-up.

I would back the tension off to around half or less of the final value, and retension by winding up the drive side first to pull the wheel to center. Not sure of what your '25' refers to in real tension - each brand of gauge has their own numbers and you should have a conversion chart that would give us better tension data.

Note that the non-drive side tension will be about 60-70% of the drive side. Don't despair, it will come out OK and it's just spokes and nipples, not something that can beat you at this game.

[StressStrain]

It's very common to have rear wheel spoke length differ by just 2mm. I would not use a single average length for both sides. But it's probably too late to change that....

If you are confident the lacing is correct, I would drop the tension in ALL spokes way back and start the tensioning and truing all over. I would not want to correct 25mm off dish when the spokes are highly tensioned - it's too easy to accidentally overtension.

So...drop tension, start the true/round/dished iterative dance, and finalize tension at the end.

[Spaghetti Legs]

Did you measure the rim ERD yourself or use some other source? I think you set yourself up for failure with the spoke length compromise and will have a huge challenge getting a good wheel doing that. Every time I’ve had a problem with a wheel build it’s boiled down to an incorrect smoke length, usually from an incorrect ERD.

I would mentally prepare to have to start over on the spokes and also triple check your ERD.

[j_gantzer]

Off-set rim?

[Broccoli Cog]

Originally Posted by Spaghetti Legs

Did you measure the rim ERD yourself or use some other source? I think you set yourself up for failure with the spoke length compromise and will have a huge challenge getting a good wheel doing that. Every time I’ve had a problem with a wheel build it’s boiled down to an incorrect smoke length, usually from an incorrect ERD.

I did not measure ERD myself. I used the manufacturers website for the specs. It's a Velocity Atlas rim so I thought I would be fine using that.

Regarding the differential spokes I knew I might be taking a chance but the Park Tools video I watched talked about taking an average of the two. It sounded less complicated to do it this way so I figured I'd try it. I don't have a lot of money invested in the hubs and the rims were hanging in the basement not being used so I may decide to start over. I'll try backing off the tension first and then try to correct the dish as I add tension back.

Thanks for the feedback.

[PortlyPuncheur]

A massive dishing error is to be expected if you are putting equal tension on drive side and non-drive side spokes. A pretty common result for properly dished wheels is 120kgf DS and 65kgf NDS.

I would highly recommend Musson's wheel building book. It is the most succinct (yet complete) guide to building wheels that I've come across. Very easy to read the entire thing in less than one evening, and is a useful guide to follow every time you build a wheel for your first dozen times. Probably the best $11 you'll ever spend.

https://www.wheelpro.co.uk/wheelbuilding/book.php

[Broccoli Cog]

Originally Posted by PortlyPuncheur

A massive dishing error is to be expected if you are putting equal tension on drive side and non-drive side spokes. A pretty common result for properly dished wheels is 120kgf DS and 65kgf NDS.

I would highly recommend Musson's wheel building book. It is the most succinct (yet complete) guide to building wheels that I've come across. Very easy to read the entire thing in less than one evening, and is a useful guide to follow every time you build a wheel for your first dozen times. Probably the best $11 you'll ever spend.

https://www.wheelpro.co.uk/wheelbuilding/book.php

I have the Musson book but can't access the new spoke calculator he has. I purchased the ebook in 2015 and of course can't find my proof of purchase. Part of my problem is that I need a reliable spoke calculator that I am confident using. I am attempting to reach out to him now but I'm guessing I may need to buy the book again.

[Mark McM]

Originally Posted by Broccoli Cog

I have the Musson book but can't access the new spoke calculator he has. I purchased the ebook in 2015 and of course can't find my proof of purchase. Part of my problem is that I need a reliable spoke calculator that I am confident using. I am attempting to reach out to him now but I'm guessing I may need to buy the book again.

The calculations for spoke length are easy (it's just high school level trigonometry). The critical part is getting the correct dimensions as input to the calculations. There are many on-line spoke length calculators that do the calculations, once you enter the dimensions.

[dgauthier]

Originally Posted by Broccoli Cog

(...) Regarding the differential spokes I knew I might be taking a chance (...) I may decide to start over. (...)

I have two suggestions to offer:
1. I encourage you to start over with different length spokes, for the reasons Mark McM cited -- you want the drive side spokes and the non-drive side spokes to engage the nipples the same way. Spokes are cheap, and you want the wheel to be right.

2. As PortlyPuncheur pointed out, in a rear wheel only the drive side spokes will be at full tension. The non-drive side spoke tension will be so low it can be difficult to ensure the non-drive side tension is adequate. One way to address this is to only bring the drive side spokes to full tension, while leaving the non-drive side completely slack. Once the drive side is fully tensioned, the non-drive side is tensioned to center the rim. (The drive side tension will increase as you do this, but typically only a small amount. It's a good idea to check the final drive side tension to ensure it does not exceed the tolerance of the rim, and reduce tension slightly if necessary.)

[PortlyPuncheur]

[QUOTE=dgauthier;3352053]I have two suggestions to offer:
1. I encourage you to start over with different length spokes, for the reasons Mark McM cited -- you want the drive side spokes and the non-drive side spokes to engage the nipples the same way. Spokes are cheap, and you want the wheel to be right.

Agree with the above.
But before you order anything I'd do the following just to learn from it.
Try "building from right to left":
1. Leave your DS spokes alone (sounds like they are pretty tight) and loosen all of the NDS spokes.
2. Check your dish in this state (It should now be skewed too far to the DS).
3. Start applying equal tension to NDS spokes in small increments, for example half turn to each NDS spoke at a time.
4. Check your dish repeatedly as you go, and stop adding tension when the dish is correct.
5. Then do final lateral truing.

If you're still struggling, post details on the rims, spokes, and hubs you're working with (disc or rim brake?)

[dgauthier]

Originally Posted by PortlyPuncheur

(...) But before you order anything I'd do the following just to learn from it (...)

This is great advice. You'll get the experience of tensioning a rear wheel properly, without going to the trouble of taking everything apart.

[PortlyPuncheur]

These have been my favorite spoke calculators of late:

https://www.kstoerz.com/freespoke/
https://spokes-calculator.dtswiss.com/en/
https://spokecalc.io/

[bikinchris]

Portly is correct.
First mistake is using the same spoke when you need a 2mm difference from side to side. If you use an offset rim and only have 1mm difference, then you can use the same spokes on both sides.
In your level of wheel building, I would work the wheel back and forth taking a whole turn out of the dish on the non-drive side all at once, then adding a whole turn on the drive side to see if the spokes you have will work. If you run out of threads, you will have to change the drive side and if you have to back off the non drive side until the threads are showing, it will make them weaker.
You will find that the drive side is much tighter than the non drive side and that's just the way it's going to have to be.