Bicycle Mechanics - wheel dishing
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i;ve never built a wheel
but it occurs to me..
when dishing the rear for the cassette offset, does anyone ever use shorter spokes for the drive side?
seems like if you don;t, you would end up with high tension on the non drive side and low tension on the drive side..
which could lead to collapsability....
also when it;s dished, how is it still straight?
seems like the rim edges wouldn;t be parallel to the ground any more, they would be higher on the non drive side [at the ground], due to higher tension...?
i mean how can you have higher tension on one side than the other, and not distort something?
04-14-12, 12:00 PM
1. 1-2mm shorter drive side is common.
2. The spokes regardless of length are competing to pull the rim to one side or the other - a rim that naturally needs to fall centered between the locknuts of the hub. The side that wins is the side with more tension. In a symmetrical wheel - both sides are even. In an asymmetrical wheel one flange has less offset and is closer to center and therefore need to carry more tension to keep rim centered between the locknuts.
3. For a rear asymmetrical rear - it is the shell flanges that have moved away UNEVENLY away from the center of the structure - not the rim. The rim is still centered between the ends of the locknuts of the hub.
Some educational brush up points for you to follow up on:
1. Simple physics. (A wheel is a pre-stressed assembly, not a rigid structure.)
2. Definition of dish:
- As an adjective - an appearance of dish. (Not brought to bear in the actual technical process of assembling a wheel.)
- As a verb - the act of centering the rim between the ends of the locknuts of the hub - or in some cases - the ends of the end caps of the hub. (Directly applies to the technicals of wheel assembly.)
3. What offsets are in relation to the center of something and how it influences things.
04-14-12, 12:47 PM
Go take a really good look at a rear wheel - that would have answered quite a few of your questions. Most of your other questions would have been answered by a little internet enquiry on your part. There's a new website www.lmgtfy.com. You're sure to find it useful.
"Go take a really good look at a rear wheel - that would have answered quite a few of your questions. Most of your other questions would have been answered by a little internet enquiry on your part. There's a new website www.lmgtfy.com. You're sure to find it useful. "
that helped a lot
04-15-12, 06:50 AM
Classically, yes, you would use shorter spokes on the drive side. Some hubs, however, this is not necessary. And usually ds and nds are so close, you can get away with one spoke size.
04-15-12, 07:44 AM
Most of your other questions would have been answered by a little internet enquiry on your part.
How is that not what he did?
04-15-12, 07:49 AM
You could google a lot of sites and not find the answer to your question. I find these forums actually have very few GIYF responders.
04-15-12, 07:22 PM
Non-drive side spokes should "theoretically" be shorter than drive side spokes in an asymmetrically dished rear wheel, if you
want the spoke threads to engage to the same depth on the nipples of the ND and Drive sides. As a practical matter you can often
get away with the same spoke length for both sides. The common wheelbuilding "spoke calculators" will let you know what you need
for your particular hub/rim combo. What you don't want to have happen is the drive side spokes sticking too far or bottoming out
into the drive side nipples when you tighten up the wheel.
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