Out of balance Hunt carbon wheels?

[Ajax Bay]

Answer to final Q. The thoughts and words are my own. Please feel absolutely free to ignore them.

Thank you. Problem is that if what you type seems in error and not queried, others may think what's said is correct.

I think we are maybe talking in cross purposes? In the case of a rim brake rear wheel rim is centred between the hub's spoke flanges, but the protruding axles lengths left and right are unequal, so the frame has to be built to accommodate. In the case of a disc brake rear wheel, the rim is not centred between the hub spoke flanges, and the protruding axle lengths left and right are unequal. Again the frame is built to accommodate that.

"In the case of a rim brake rear wheel [the] rim is centred between the hub's spoke flanges" No, this is not the case.
"the frame has to be built to accommodate the protruding axles lengths left and right [which] are unequal." The frame may or may not be built asymmetrically. Many/most aren't. Not sure what you mean by "protruding axle lengths" but assume the dimension between flange and dropout is meant.
I will go and look for a diagram, to help you, and edit this post to add it - Edit: see below (from https://www.prowheelbuilder.com/spokelengthcalculator/)
I think, like Matt (assumed) you have maybe just transposed the sentences/phrases in these ideas, causing lack of 'clarity'.

 

[monkers]

Thank you. Problem is that if what you type seems in error and not queried, others may think what's said is correct.

"In the case of a rim brake rear wheel [the] rim is centred between the hub's spoke flanges" No, this is not the case.
"the frame has to be built to accommodate the protruding axles lengths left and right [which] are unequal." The frame may or may not be built asymmetrically. Many/most aren't. Not sure what you mean by "protruding axle lengths" but assume the dimension between flange and dropout is meant.
I will go and look for a diagram, to help you, and edit this post to add it.
I think, like Matt (assumed) you have maybe just transposed the sentences/phrases in these ideas, causing lack of 'clarity'.

I had quite deliberately used the words 'offset' and 'dishing' to mean different concepts. It seems that they have become conflated.

I made one error, I have had no difficulty in acknowledging that.

My intention was to answer the questions that were being asked about dynamic wheel stability I still believe I answered that point successfully.

The point about Euler is interesting, but is not relevant to my points. Euler relates to single static axial compressive load on a material of uniform section.

 

[matticus]

The point about Euler is interesting, but is not relevant to my points. Euler relates to single static axial compressive load on a material of uniform section.

I just think "The Euler Strut" is an amusing name. It has been tickling my friends and I for 30 years

 

[I like Skol]

Not sure what bikes are being discussed here, but I build my own wheels and on all my builds/bikes, regardless of rim or disc brake, the rim is centred in the frame and midpoint between the dropouts. To confirm I have got it spot on I always flip the wheel to check. That's right, even the back wheel should have the rim in the middle of the frame regardless of which way it is fitted ( you might have to remove the cassette/disc to try this).

 

[monkers]

Thank you. Problem is that if what you type seems in error and not queried, others may think what's said is correct.

"In the case of a rim brake rear wheel [the] rim is centred between the hub's spoke flanges" No, this is not the case.
"the frame has to be built to accommodate the protruding axles lengths left and right [which] are unequal." The frame may or may not be built asymmetrically. Many/most aren't. Not sure what you mean by "protruding axle lengths" but assume the dimension between flange and dropout is meant.
I will go and look for a diagram, to help you, and edit this post to add it - Edit: see below (from https://www.prowheelbuilder.com/spokelengthcalculator/)
I think, like Matt (assumed) you have maybe just transposed the sentences/phrases in these ideas, causing lack of 'clarity'.
View attachment 588633

A diagram is a useful edit, so thanks for that. I had replied before seeing your edit.

One point though, there are posts that illustrated my error; however you've made one too. In an effort to bring clarity to the point about rim brake rear wheels, you've posted a dimensioned diagram of a disc brake hub.

As I always say, we all make mistakes said the Dalek climbing off the dustbin.

 

[Ajax Bay]

Since you seem up for a 'chat-joust'.

My intention was to answer the questions that were being asked about dynamic wheel stability I still believe I answered that point successfully.

Genuine question: what question about "dynamic wheel stability" do you think was being asked? The OP had shown us an unbalanced wheel. There were no lateral forces involved.

One point though, there are posts that illustrated my error; however you've made one too. In an effort to bring clarity to the point about rim brake rear wheels, you've posted a dimensioned diagram of a disc brake hub.

The diagram I posted was quite deliberately chosen. I aimed to show that the dish of a disk-braked rear wheel was less (you had suggested more) than a rim-braked one (like the OP's). This means a disk-braked rear wheel (normally with an OLD of 135mm as a bonus) is less dished so stronger, structurally (ceteris paribus), and the opposite spoke tensions are less unequal. The required spoke lengths for this build were L=293.8mm, R=292.6mm btw.

 

[matticus]

Not sure what bikes are being discussed here, but I build my own wheels and on all my builds/bikes, regardless of rim or disc brake, the rim is centred in the frame and midpoint between the dropouts. To confirm I have got it spot on I always flip the wheel to check. That's right, even the back wheel should have the rim in the middle of the frame regardless of which way it is fitted ( you might have to remove the cassette/disc to try this).

Some frames are built with asymmetry in the rear triangle (usually to reduce dish, as it happens). But they are rare ..

/chat-joust

 

[monkers]

Not sure what bikes are being discussed here, but I build my own wheels and on all my builds/bikes, regardless of rim or disc brake, the rim is centred in the frame and midpoint between the dropouts. To confirm I have got it spot on I always flip the wheel to check. That's right, even the back wheel should have the rim in the middle of the frame regardless of which way it is fitted ( you might have to remove the cassette/disc to try this).

I agree.

In order for the rim to be central in the frame, the wheel needs to be dished to compensate for hub offset. This remains true if the wheel is switched round in the frame. If a disc brake front wheel was switched round though, the spokes would surely foul the caliper? At the rear the disc would foul the seatstay?

 

[monkers]

Since you seem up for a 'chat-joust'.

Genuine question: what question about "dynamic wheel stability" do you think was being asked? The OP had shown us an unbalanced wheel. There were no lateral forces involved.

The diagram I posted was quite deliberately chosen. I aimed to show that the dish of a disk-braked rear wheel was less (you had suggested more) than a rim-braked one (like the OP's). This means a disk-braked rear wheel (normally with an OLD of 135mm as a bonus) is less dished so stronger, structurally (ceteris paribus), and the opposite spoke tensions are less unequal. The required spoke lengths for this build were L=293.8mm, R=292.6mm btw.

I don't mind a conversation that leads to greater understanding; but if by chat joust a game of winners and losers I'm really not interested.

I've had both back wheels out again. The rim brake Bontrager wheel has little discernible visual asymmetry when I stand over it and look down, whereas the disc brake Zonda wheel has a pronounced difference (which is what I said in the first place). I was careful to say I hadn't measured anything.

I do follow your reasoning and I'm a bit confused on why the dishing looks so much more pronounced on the Zonda. When I've had the time to have lunch then measure, scratch my head and so on, I'll come back with an honest approach without chat jousting. But if it's chat joust that you want, you'll need to look elsewhere.

 

[Ajax Bay]

I've had both back wheels out again. The rim brake Bontrager wheel has little discernible visual asymmetry when I stand over it and look down, whereas the disc brake Zonda wheel has a pronounced difference (which is what I said in the first place). I was careful to say I hadn't measured anything.

btw
Your vision, for whatever reason, is deceiving you. The rim-braked rear wheel has greater dish and therefore its two flanges are at, say, 35mm and 18mm from the wheel 'centre line'. The diagram I shared of a disk-braked rear hub shows that, because the hub is 135mm OLD and because the rotor and fitting takes space, the 'offset' from hub centre is less (33mm and 21mm). The latter is like your Zonda: there's a 'difference' (assume same as your 'offset') but it's less pronounced. I appreciate that you've been consistent. [Spolier][spoiler/]

 

[fossyant]

What's any of this 'ballcocks' got to do with the OP's wheel out of balance ? I'm suspecting excess resin somewhere on the rim construction.

 

[monkers]

Since you seem up for a 'chat-joust'.

Genuine question: what question about "dynamic wheel stability" do you think was being asked? The OP had shown us an unbalanced wheel. There were no lateral forces involved.

The diagram I posted was quite deliberately chosen. I aimed to show that the dish of a disk-braked rear wheel was less (you had suggested more) than a rim-braked one (like the OP's). This means a disk-braked rear wheel (normally with an OLD of 135mm as a bonus) is less dished so stronger, structurally (ceteris paribus), and the opposite spoke tensions are less unequal. The required spoke lengths for this build were L=293.8mm, R=292.6mm btw.

In answer to your first question - there was a discussion about wheel imbalance. The discussion was about static imbalance. The OP then posted a clip where the wheel imbalance was producing a pronounced lateral shake (or shimmy) in the frame. This is dynamic imbalance rather than static. The discussion was in context with his new Hunt wheels. I had previously seen a youtube film made by bikotic where his new Hunt wheels produced some bumtwitching moments for him when fitted to his Cervello bike. When he changed the wheels to his Cube bike, he got the same effect. He swapped his Cervello for a Scott bike in the meantime. Hunt replaced the front wheel with a less deep aero rim, and Bikotic has not reported anything since (maybe the Hunt wheel have done for him).

A couple of people asked questions. I went on to make some points that covered the Hunt wheels in the OP and those in the Bikotic video concerning speed induced death wobble when riding on new Hunt wheels. I gave my own perspective and pair of analogies based on experience of the dynamic behaviour of shallow section structures etc based on work in the automotive industry.

There are a number of unknowns in the equation meaning that neither I or anyone else can form opinion of. We haven't seen the OP's front wheel spin to know if there is any balance issues with that wheel. We can't know if Bikotic's first deeper Hunt wheel had dynamic balance problems or if the effect was purely aero.

I think people may have confused by my use of the term 'offset' where I was referring to hub design and 'dishing' where I'm talking about wheel build.

Anyway, moving the discussion on - I've now measured the Zonda wheel, it's dimensions are somewhat different from the diagram of the hub up the thread above. I've looked to see why Campy have done it this way, and the reason has become apparent - the Liv Langma has six bolt disc rotors rather than centre locks. This requires putting the disc further out from the hub and a longer through axle. I'd like to have a Campy centre lock built wheel to compare it to, but alas I haven't.

I had said that my observations were visual rather than obtained by measurement. With the wheels to hand I was not wrong in that observation; but I was wrong to say that the Emonda rear wheel is not dished, visually it is not so much, but measurement shows that it is slight, presumably because in the Bontrager hub design, hub offset has been minimised.

Long story short, bike wheels are dished to offset hub offset, but different hubs have different amounts of offset making it difficult to generalise as I had done - hand up - guilty.

I think we can generalise on one point though and say that rim brake front wheels need no hub offset so they require no dish in the wheelbuild.

 

[monkers]

btw
Your vision, for whatever reason, is deceiving you. The rim-braked rear wheel has greater dish and therefore its two flanges are at, say, 35mm and 18mm from the wheel 'centre line'. The diagram I shared of a disk-braked rear hub shows that, because the hub is 135mm OLD and because the rotor and fitting takes space, the 'offset' from hub centre is less (33mm and 21mm). The latter is like your Zonda: there's a 'difference' (assume same as your 'offset') but it's less pronounced. I appreciate that you've been consistent. [Spolier][spoiler/]

Thanks.

No it isn't. We've cross-posted and my reply to these points is to be found in my previous post.

 

[monkers]

What's any of this 'ballcocks' got to do with the OP's wheel out of balance ? I'm suspecting excess resin somewhere on the rim construction.

The clip of the unbalanced wheel showed that it has pronounced dynamic imbalance. I didn't say earlier but my partner's Liv Langma had a wheel collapse in the front wheel when the bike was new due to unequal spoke tensions. She did say that the collapse was preceded by a lot of vibration.

Having seen the manner in which the wheel suddenly folded I was reminded of shallow section stability theory. I was able to reverse the 'flip' of the wheel as it had folded by hand and tweak the spokes to make it more stable. The wheel needed to be replaced under warranty though as the collapse had also produced a flat spot on the rim that the technician was unable to eradicate. Hunt had given the possible reason for the vibration as unequal spoke tensions. Imbalance and vibration are not the only consequences of unequal spoke tension.

Please feel free to ignore my 'ballcocks' posts as you see fit in the future.

 

[fossyant]

Please feel free to ignore my 'ballcocks' posts as you see fit in the future.

I will, no issues here.