Bike journo doesn't do physics shocker

They’re very, very stiff… a quick twang of the spokes quickly explained why, there’s incredible spoke tension between hub and rim

nobody want to support Matt then?

where’s it from then?

very short quote you’ve given us.

Why not simply explain his ‘mistake’ (if indeed there is any), rather than attempt to look all superior?

I don’t ‘do physics’ either. Or maffs. Not in my field of inertest.

How good’s your cycling journalism?

Random internet person doesnt do proper thread shocker.

I’d have given up after the first non-response, tbh.

would that not make them stiff? 😕 😆

did more than a spot of physics, back in the day, and struggling here

Is it because the tension is between the spokes?

Obviously nobody else reads the mag then?

No – spoke tension doesn’t affect wheel stiffness. Don’t have a problem with people not doing stuff outside their specialist field, but it is irritating to see incorrect stuff in print.

Yea, where’s the mistake?

High levels of pre applied tension = stiff structures, a principle used eveywhere from spoked wheels, railway lines through to huge dams.

I believe it’s a miss-quote from one of Charlie Sheen’s Tweets, I’ve rework it based on that assumption, should be read like this?:

I’m very, very stiff… a sudden twang In my underware and I realise, I’ve necked a dangerous cocktail of Rohypnol, Viagra and Half a bottle of Tequila… It’s going to be another messy night, and yet again I won’t remember a thing…

so if the spokes were barely screwed into the nips and all floppy it wouldn’t affect the wheel stiffness?

spoke tension doesn’t affect wheel stiffness

go on then, enlighten us to what does.

so if the spokes were barely screwed into the nips and all floppy it wouldn’t affect the wheel stiffness?

That’s a strawman. Provided the spokes are under enough tension that they don’t go completely slack in use (as is the case for any half-decent wheel), increasing the tension further doesn’t increase the stiffness.

increasing the tension further doesn’t increase the stiffness.

I think you’ll find thats not true.

No – spoke tension doesn’t affect wheel stiffness.

(Loosens spokes on wheel; notices wheel is now flopy. Tightens spokes on wheel, notices wheel is now stiff)

😕

I think you’ll find thats not true.

I think you’ll find it is! Try superposition of forces.

We’ve already done that strawman, elf.

Is it panto season already?

He’s behind you!

Imagine a structure with no stength in tension and lots of strength in compression (the opposite of a spoke in this example, a wall) with no cement.

Normaly the wall is fine. The forces act directly through the middle of it.

Push on it and the imaginary line the force travels down moves towards the edge. Once it gets about 2/3 of the way accross the wall falls over as 1/3 +1/3 either side of the line is in compression, but the 1/3 furthest from the line is in tension, and falls appart. This also applies to loading the top of the wall, if you put an off center weight on the wall it will fall over even if the COG is within the wall itself.

To counteract this dams and other structures can have steel tie rods/cables tensioning them top to bottom to keep back the water. This does the job of the spokes in the wheel.

Surely a spoke that is barely under any tension has more of it’s elastic range available;

it will elongate (allowing the wheel to deform) under a lesser load than a spoke which has a higher pre-tensioning, which will require higher loads toachieve the same deformation (higher loading meaning a podgier IT manager)…

http://www.sheldonbrown.com/rinard/wheel/index.htm#1

Surely a spoke that is barely under any tension has more of it’s elastic range available;

it will elongate (allowing the wheel to deform) under a lesser load than a spoke which has a higher pre-tensioning, which will require higher loads toachieve the same deformation (higher loading meaning a podgier IT manager)…
No. As suggested above, look up superposition of forces.

To counteract this dams and other structures can have steel tie rods/cables tensioning them top to bottom to keep back the water. This does the job of the spokes in the wheel.

Except a wheel isn’t a dam – though to be fair it’s not a bad analogy. Increasing the tension in the steel ties in a dam doesn’t increase the stiffness of that either – it just increases the maximum load.

Yep, he says

“If spokes are tighter initially, then the sudden increase in flexibility shown in data points 9 and 10 is less likely to occur in use because a tighter wheel can bear a higher load before spokes become slack.”

(where 9&10 show a large deflection, 1-8 don’t).

I.e tighter spokes = less deflection.

It doesn’t obey Hookes law, but it does show a deflection for a given weight can be shown Vs initial tension. It’s just a modulous that relies on 3 variables (force, initial tension and deflection).

“If spokes are tighter initially, then the sudden increase in flexibility shown in data points 9 and 10 is less likely to occur in use because a tighter wheel can bear a higher load before spokes become slack.”

<sigh> – we’re not talking about what happens when the spokes become completely slack! His first statement is:
“Some believe that a wheel built with tighter spokes is stiffer. It is not. Wheel stiffness does not vary significantly with spoke tension unless a spoke becomes totally slack.”

Depends whether ‘significantly’ is detectable by humans after you’ve stuck a nice squishy tyre on I suppose,

Yes, but you’re telling me you’ve never ridden a bike with spokes that are tight (but not very tight), and it felt horrible, then added 1/4 to 1/2 turn to each spoke? to improve them?

My shimano facotry wheels on the road bike needed a half turn to stop the rear rubbing on the brake blocks while climbing out of the saddle. They ‘felt’ different afterwards too, but the brake blocks show it’s not a placebo.

we’re not talking about what happens when the spokes become completely slack!

You aren’t, I am. Because thats where the difference is.

i’m not sure i understand.

a loose spoke means ‘not stiff wheel’. tight spoke means stiff wheel but tighter spoke does not equate tighter wheel.

There is a threshold limit of tightness where it becomes stiff and no stiffer?

Really, who gives a sh*t.

a loose spoke means ‘not stiff wheel’. tight spoke means stiff wheel but tighter spoke does not equate tighter wheel.

There is a threshold limit of tightness where it becomes stiff and no stiffer?

Errrr kinda, the “tight” and “very tight” (lets ignore completely loose spokes for now), both have (aproximately) the same stiffness up untill the point where you load them past the point where half the spokes go slack. Beyond this the stiffness drops off massively.

The point is a tighter wheel takes more load to reach this point. So the “very tight” set of wheels won’t deflect during a hard corner, landing a jump or hittig a rock where the “tight” wheels MIGHT deform IF the force is grat enough to slacken off a proportion of the spokes.

All I know is that I once had a bike (04 Stumpy FSR) that was feeling a bit wobbly on the back end in fast corners and that by retensionning the rear wheel it improved dramatically. That was only about 1-1.5 turns on each spoke nipple to achieve that noticeable difference.

Explain away……….!

@ thomthumb

yes, tightening the spokes will increase the rigidity of the wheel, but only up to a certain point (whatever value that point may be)

If you turn the nipples 3 times more, it will not increase the stiffness of the wheel (technically it may on paper, but certainly not noticable to the rider)

Yes, but you’re telling me you’ve never ridden a bike with spokes that are tight (but not very tight), and it felt horrible, then added 1/4 to 1/2 turn to each spoke? to improve them?

Apart from the very first set of wheels I built which disassembled themselves on the first ride, no. Only badly built wheels do that.

You aren’t, I am. Because thats where the difference is.

But that difference is one of strength, not one of stiffness – the amount of force required to make a spoke slack is very little less than the amount of force required to buckle a wheel. The normal measure of stiffness of wheels is when the spokes haven’t gone slack – try re-reading that article I linked, and you’ll see there are significant differences in stiffness between different wheels without spokes going slack.

pedant of the week award goes to…

but it is irritating to see incorrect stuff in print

I take it you post with your eyes closed most of the time. 🙂

If you’d actually wanted to educate people you might have started by saying “I read this in a magazine today but…”

spoke tension doesn’t affect wheel stiffness
so if the spokes were barely screwed into the nips and all floppy it wouldn’t affect the wheel stiffness?

That’s a strawman. Provided the spokes are under enough tension
its not its a poorly worded explanation by you that you had to add a caveat to in order for it to be true.

No tension = floppy, tension = stiff , more tension = no more stiffness.
So stiffness is not affected once enough tension is achieved which is not what you said.
Yes as per the original point it is annoying when people dont express themselves well. When they do it whilst mocking others then deny it is is even less better [ see what i did there 😉 ]

Now reading all the other posts and see my attempt at a response has been done already…

Jobst Brandt will be along in a minute and then this thread will never end. I’m getting horrible flashbacks to the spoke tension flame wars on u.r.c

its not its a poorly worded explanation by you that you had to add a caveat to in order for it to be true.

Taken in the context of the mag quote, the caveat wasn’t needed – it should have been quite clear what I meant to anybody paying attention and not deliberately taking my comment out of context. I mean it’s not like Matt wrote “there’s sufficient spoke tension between hub and rim”, and he presumably wasn’t comparing the stiffness of these wheels with other pairs he’s used where the spokes were floppy. Or did I need to requote the bit from the mag in the first post to make that clear to you?

Nobody compares the stiffness of wheels with loose spokes.