[Closed] Resolving spoke tension into component parts

Wheels are simple trig which most people completely over complicate and get wrong

First rule everything will be in balance. So the axial forces which set the dish always match, if they didn’t you have discovered perpetual motion.

Second rule is the spoke angle gives the ratio of axial to radial force. This is basic trigonometry.

This then tells you the correct spoke tensions on each side. It also describes the ideal spoke flange design which you have to compromise to fit things like disc mounts and freehubs in

I’m amazed when people are surprised the tensions are different on each side, and come up with spectacular reasons to justify their point.

And to the people who say spokes are weak, you can pick up a car with 4-5 of them

Yes the side forces are minimal but there are 32 of them. Also when a wheel is in use the force is always directly straight through the wheel.... it’s why you lean over in a corner!

Neil Superstar

Yeah, perfectly happy with the trig, and the fact that horizontal forces need to be balanced. Happy that this means a difference in spoke tension between two sides.

It was just that I've been amusing myself with the numbers and while it's perfectly logical, I was surprised at how low the horizontal components are.

the tensions are different on each side

OMG!!! Surely you'd have to ride with the bike leaned over or you'd crash, no?

Where does the phrase flying by the seat of your pants come from?

It’s because the force you feel pushing you into the seat of the plane is not gravity. But the plane is banked over to make the forces of lift affect in the direction of the wings.

Same on a bike, if you don’t lean over you fall off.

So these side forces are surprisingly small. But under load go up a bit as the structure flexes if you land a jump badly and side load the wheel

I find it mad too that a few 1.5mm bits of wire hold it all together but it’s exactly the force this structure requires

Neil Superstar

Could of obvious examples to prove your point:

Rear wheels are far easier to bend, if you side load the front wheel the steering turns and the load goes away, at the back it can't so the wheel gets bent.

Soapbox racers, if you've ever watched the endless re runs on Dave you can see the ones using bmx/mtb wheels just fold over in the corners as they're just not designed to take loads axially.

Did Sunday morning chess club finish early this week?

So what we're saying is that boost and superboost are pointless (other than to fit our frames) as it makes such a small difference as to make no difference, unless you've ****ed up at which point, it doesn't matter much as you've ****ed up.

I've not ran the figures, but doesn't boost/superboost just put relative spoke angles back to where they were in the days of ye olde 26" 9 speed, for modern 11/12 speed 27.5"/29", while minimising offset?

Depends
Hub manufacturers/designers don't all seem to have the same idea on how to optimise flange spacing/height within the extra OLN widths of Boost/SBoost.
11 speed runs absolutely fine on my yay olde 26" 135/142 hubs, stronger shorter lighterer spokes and stronger stiffer lighterer 26" rims and stronger lightrerer funnerer 26" tyres.
Oh.. .and not forgetting the strongerer lighterer rear mech from not needing a stupid 50T saucer sprocket on the cassette

#264LYFbro

The reason this came about is, I was looking at the theory of building the wheel one side at a time. The idea is that you only tension the drive side spokes on the rear, but only look at radial trueness. Once that's done, tension the disc side until you have the dish and lateral trueness that is required. This way, the high tension drive side nipples don't need to be touched again and it saves trying to achieve high tension on the nipples.

However, looking at the numbers, due to the low angle (5.8°) then there's very little difference in the tension on the drive side spokes whether the disc side is added or not (unless I've missed something thing fundamental).

Yup it’s what you have to do on 11speed road wheels because the drive side angle is so steep. You tighten the nondrive side last as it is at lower tension and if you try and do the drive side it is hard as the tension seizes the threads

Downside to road is that the nondrive often is so loose it causes problems and you can’t increase it because the drive ones are maxed out

Boost is good as it means instead of a 70:120 tension ratio you get 100:100 for example which is better as you eliminate both the overtightened and under tension problems. But... just slamming the flanges out as wide as possible does the opposite. It’s why our boost front are slightly inboard on the drive side, further out is a step backwards

It’s all simple trig

Neil Superstar

But according to the trig, the drive side tension doesn't change by any noticeable amount whether you add the opposing side tension or not.

Did Sunday morning chess club finish early this week?

E-bikes are the new chess.

It’s a proportional ratio. Double the tension and the axial forces double. Then do trig to work out what happens on the other side (it doubles)

But yes the axial forces are minimal in a wheel. Contrary to much of the marketing guff out there

I have always thought offset spoke beds are a good idea. But the idea has not really caught on.

Asymmetrical rims are a good idea but are more expensive to make. Help balance up the spoke tension gap. Most of our range are asymmetrical mainly for build reliability reasons

Neil Superstar

But according to the trig, the drive side tension doesn’t change by any noticeable amount whether you add the opposing side tension or not.

In reality it shows a measurable change in tension on most wheel builds.

Easton used to tension the drive side rear then use the non drive to dish and true. Makes replacing a drive side spoke time consuming to do as per the instructions.

When an Easton rear wheel is hand-built, the drive side spokes are brought to the highest tension possible with a spoke wrench. Then, the builder will use the non-drive side spokes to bring the wheel into dish and true. The result is a drive-side spoke tension higher than can be achieved by turning a nipple. This affects maintenance in two significant ways.

While truing the rear wheel, the drive-side nipples should not be used. Because of the higher tension, the nipples will likely be stripped if they are tightened. In addition, the uniformity of the drive-side spoke tension is essential to the wheel’s long term stability.

If a drive-side spoke is broken, simply re-lacing the spoke will not create the necessary tension to match its surrounding spokes. This imbalance can cause repeated spoke breakage, as the other spokes strain to compensate. To avoid this, the non-drive side spokes must be completely de-tensioned before replacing the drive-side spoke. Once the replacement spoke has been brought to an even tension with the other drive-side spokes, the wheel can be brought back to into true and dish using the non-drive spokes. This process will ensure proper tension, maximize strength, and utilize the original design of the wheel.

That's how I got into all of this. I want to use that build method and I'm aiming for 120kgf max tension on the finished wheel so I'm trying to work out what tension to take it to initially.

Cripes Easton must be using very high tensions then. Or possibly alloy nappies. <<Amusing autocorrect left in. I am sure that Easton could do nice triple butted nappies in aluminium if they tried.

After having slept on it, it's clear that what I've overlooked is the increase in distance between nipple and flange when dishing the rim. I'm comparing apples to oranges.

Maths gets a bit trickier now.

The increase will be relatively small though. But if you are running into problems achieving the high tensions you want then every little helps I guess. More relevant for road wheels with 130mm axles like others have said.

I'm not having any issue with maximum tension, if anything, I'll end up with too much. If I want to finish with a max of 120kgf, I'm trying to calculate how much tension is required on the drive side only if I build the wheel right to left.