Bicycles Asked on May 29, 2021
I am building wheel with 7 speed freewheel so my rim dishing needs to be towards the side of the hub.
Using 281mm spokes on both sides of the hub except for side close to freewheel used 12mm nipples and for other side 16mm nipples.
I have tension 160 kgf for spokes at hub side and about 90 kgf for spokes on opposite side.
Somewhere i read "tension for spokes ideally needs to same prevent breaking" is that same tension for all spokes on one side of the rim or every spoke on the rim needs to be same tension?
If i set same tension i will loose dishing, so if i say use 181 mm spokes on one side and 184mm spokes on other side then i can set equal tension and rim still be centered over center of fork?
The drive-side rear needs to be at higher tension because the spoke angles are asymmetric. There have been two other alternatives to spoke angle asymmetry: rim spoke hole asymmetry and frame asymmetry but neither has become widely used. In disc brake front wheels, the opposite effect is seen: the non-drive-side will be at higher tension due to needing to have space for the disc brake rotor.
160 kgf is a high tension and unless your rim has double eyelets (sockets), may be too much for the rim. Even if your rim has double eyelets, having such high tensions might make the rim buckle, meaning getting it completely trued might be a bit difficult as a small adjustment somewhere can create a large error in some other location, and stress relieving by grasping the spokes can make it untrue in a wavy way.
160 kgf really requires reasonable spokes (so overly butted spokes or spokes too thin in the middle section such as 2.0mm/1.5mm/2.0mm should be avoided), lubrication at the nipple-to-rim and nipple-to-spoke interfaces, a strong rim and a wheelbuilder who knows how to over-do all adjustments slightly and back off to eliminate spoke windup when adjusting the nipples.
If you observe any minor amounts of buckling, reduce the tension. Also reduce the tension unless your rim has double eyelets.
The rule of thumb about spoke tensions is that every side has equal and high tension on all spokes, but for asymmetric spoke angles the tensions on both sides can differ. Only rim brake front wheels and some really wide fatbike wheels (so wide hubs that can be made to have symmetric spoke angles) have equal tensions on both sides.
Spoke length does not affect tension symmetry. Improper spoke lengths can however make it impossible to tighten the nipple fully, or strip nipple threads if there is too little engagement.
Correct answer by juhist on May 29, 2021
1600N is a lot. Check your rim’s specification, most rims are limited to 1200N. You can go slightly above the 1200N, especially since pressurizing the tyres will de-load the spokes by 50N or so.
The non-drive side will end up somewhere around 700–800N.
The most important thing is that you don’t have single spokes with very low or very high tension. In an asymmetric wheel ideally you’d have all spokes on each side at the same tension.
Using longer or shorter spokes won’t really change anything of this. The problem is simply that the spoke angle on the drive-side is steeper to make space for the cassette sprockets while keeping the rim centered.
Answered by Michael on May 29, 2021
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