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Wheel centering - tension versus length

Old 02-15-20, 02:14 AM
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Wheel centering - tension versus length

A hub can be mounted away from the wheels center, and to avoid tyre also away, compensation is needed along the spokes connecting hub to rim. What are the rules in this, for ex a small out of center of the hub can be compensated along a spokes tension difference left/right. But there must be a limit to this, from which different spokes lengths have to been used. Is there a rule describing that point?
What max distance can be corrected along tension differences?
What are the consequences of tension differences in regards to wheel strength?
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Old 02-15-20, 03:18 AM
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You can find the difference in spoke length by using a spoke calculator-- usually one of the inputs is the offset from the centre line to the flange.

A rear wheel for a road bike will often have different spoke lengths by about 1mm or so, often it's small enough that you will get away with using the same spokes left to right.

You would ideally like a good bracing angle for lateral stiffness. It's not ideal that the right side of a rear wheel has the spokes closer to vertical.

Assymmetry also gives you a difference in spoke tension from left to right and this can also be a problem if it pushes either side out of the acceptable range of tension. On a rear wheel for example it may be hard to get the left side tight enough for the spokes not to go loose without so much tension on the right that the rim fatigue cracks after a few thousand miles. A controversial subject but this can be mitigated by using a bit of thread lock or just linseed oil.
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Old 02-15-20, 03:26 PM
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When I initially read the OP I thought it was about wheels with the hub off center as in the wheel not being round when it spins

So much of the answers are shades of gray ones. The dished side of the wheel, as in the drive side for common bikes, starts to have too tight issues with much less then 1/2 the left side's flange to center. Or the left side starts to have nipple loosening issues from too little tension (Hence the rise of the thread locking nipples). I have no real numbers to quote and numbers alone serve as a poor substitute for experience and hands on learning. Andy
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Old 02-15-20, 04:40 PM
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Originally Posted by Novalite View Post
a small out of center of the hub can be compensated along a spokes tension difference left/right. But there must be a limit to this, from which different spokes lengths have to been used.
Turning the nipples in and out changes the effective length of the spoke. Once that is opposed it also changes the tension.

Two things can resist the pull of one spoke: the geometric arch of the rim, and the tension of other spokes. So you can tension a wheel with the rim in different positions of dish.

Are you perhaps really asking how far you can move things by using different positions of the nipples on the same spokes, vs at what point you need to source spokes cut to different lengths?

That would essentially depend on the range of adjustment - in a double wall rim probably where the nipple bottoms out on the spokes on one end (possible extended with a washer) and where the spoke isn't threaded far enough into the nipple on the other, forcing the shoulder of the nipple to carry the spoke force in tension.

Precut spokes typically come in 2mm increments, so one simple answer would be "where the next size becomes a better choice"
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Old 02-15-20, 08:18 PM
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A hub can be mounted away from the wheels center, and to avoid tyre also away, compensation is needed along the spokes connecting hub to rim. What are the rules in this, for ex a small out of center of the hub can be compensated along a spokes tension difference left/right. But there must be a limit to this, from which different spokes lengths have to been used. Is there a rule describing that point?

Any decent hub should be engineered to make sure the spokes won't build up too far out of proper tension. There are no real rules, you build the hub so the rim is true to the hub. The only time I built with campagnolo hubs I found them to be really bad for the non-drive side spoke tension but the wheels still held up fine long term.

What max distance can be corrected along tension differences?

You really want to look at hub dimensions to answer this question. Most 130mm hubs the center of the hub to the drive flange is right about half the distance as the distance from the center to the left flange,much more than this can leave the spokes on the non-drive side rather loose. It is possible to deal with the tension difference by using different spokes, the last wheel I built I used 2.0/1.7 butted spokes on one side and 2.0/1.5 spokes on the non-drive. The narrower section spoke requires higher tension to pull against the thicker spoke. The result was them having nearly equal tension for a really stiff build. If I was really worried about tension I'd do a 1.8/1.6 butted spoke which would take a lot of tension to keep even a poorly designed hub properly built.

What are the consequences of tension differences in regards to wheel strength?
Varies but the rin can have side movement during sprints resulting in rubbing, early spoke wear and breakage, constant need to retension.
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Old 02-16-20, 08:02 AM
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Originally Posted by Andrew R Stewart View Post
When I initially read the OP I thought it was about wheels with the hub off center as in the wheel not being round when it spins

So much of the answers are shades of gray ones. The dished side of the wheel, as in the drive side for common bikes, starts to have too tight issues with much less then 1/2 the left side's flange to center. Or the left side starts to have nipple loosening issues from too little tension (Hence the rise of the thread locking nipples). I have no real numbers to quote and numbers alone serve as a poor substitute for experience and hands on learning. Andy
I thought the OP might have bee referring to hubs that are off center laterally such as Cannondale's Asymmetric Integration system. https://cannondale.zendesk.com/hc/en...c-Integration-
It puts the rim 6 mm off center from the middle of the OLD to even out the CTF dimension on both sides.
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Old 02-18-20, 03:32 PM
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I don't refer to specific hubs or so, just that I measured the hub as 5 mm shifted to the driveside.
The hub was referenced as "Surly hub Ultra singlespeed disc 135x10mm 36G".
A possible reason for the hubs offcenter may have been a chainline error reduction, since with a centered hub, the original chainline error would have been 10 instead of 5 mm. The chainline is now straight but I suspect that the rear tyre doesn't run in the fronts trail (tyres don't wear in their center but away from the driveside. Also, the bike is like hard to keep on a road line, especially without weight on its rear rack.
In case it is indeed the reason, I wondered why the wheel wasn't built like it should, being the reason for this topic.
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Old 02-18-20, 09:02 PM
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Making the hub off center from the rim does nothing to alter the chain line. It's an asymmetrical rear triangle that does that. Shifting the position of the rim relative to the hub is then necessary to bring the rim back to the center line of the frame. This has the added benefit of equalizing the bracing angle of the spokes on both sides, making for a stronger, more stable wheel.
Check the link in my post above.
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