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-   -   Wheel lateral stiffness. WHat makes it stiff? (https://www.bikeforums.net/bicycle-mechanics/1021256-wheel-lateral-stiffness-what-makes-stiff.html)

Fly2High 07-29-15 12:34 PM

Wheel lateral stiffness. WHat makes it stiff?
 
Not sure I understand bike wheels.

What makes a wheel stiff?

Is it the spoke tension?

Spoke diameter?

rim width?

or what???

details please


Can you improve on a wheels lateral stiffness? How?


thanks

CliffordK 07-29-15 01:02 PM

Probably all of the above. Did you mention spoke count?

I would think spoke tension would be primary.

The rim will deform somewhat under your weight, and de-tension the lower spokes somewhat. So, a deep profile rim might also be a little stiffer than a low profile rim.

Bill Kapaun 07-29-15 01:03 PM

Spoke angle from wider hubs.
Fewer crosses.
A heavier spoke probably adds a very slight amount.

Marcus_Ti 07-29-15 01:04 PM

It is the constituent parts, and how well the wheel builder can work them.

You can take the best parts around, and make a floppy wheel if you don't know what you are doing. A spoked bicycle wheel is stiff fundamentally because of the large amount of tension in the spokes.

AnkleWork 07-29-15 01:12 PM


Originally Posted by Fly2High (Post 18025060)
. . . details please . . .

You first:
Define "stiffness" as you mean it.

Wilfred Laurier 07-29-15 01:12 PM


Originally Posted by Marcus_Ti (Post 18025174)
It is the constituent parts, and how well the wheel builder can work them.

You can take the best parts around, and make a floppy wheel if you don't know what you are doing. A spoked bicycle wheel is stiff fundamentally because of the large amount of tension in the spokes.

Except that they aren't stiff laterally. Event he meatiest and most well built wheels have very little lateral stiffness or strength. You can create significant lateral deflection in a spoked wheel with your pinky.

Fly2High 07-29-15 01:26 PM


Originally Posted by AnkleWork (Post 18025197)
You first:
Define "stiffness" as you mean it.

resistance to lateral flexing

Fly2High 07-29-15 01:28 PM

Then what prevents a wheel from rubbing on the front brake in a turn?

Black wallnut 07-29-15 01:45 PM


Originally Posted by Fly2High (Post 18025252)
Then what prevents a wheel from rubbing on the front brake in a turn?

The brakes are on the top of the wheel not the bottom where the lateral pressure is.

AnkleWork 07-29-15 01:50 PM


Originally Posted by Fly2High (Post 18025248)
resistance to lateral flexing

That's not very detailed. What unit of measure would you use for the quantity of "resistance?"

For design purposes, more useful quantities include elasticity, strain, stress, deformation, section modulus, etc, all of which have specific definitions and units of measure.

CliffordK 07-29-15 01:51 PM


Originally Posted by Fly2High (Post 18025252)
Then what prevents a wheel from rubbing on the front brake in a turn?

It happens sometimes.

Give just a touch more pad clearance, and all should be fine.

Fly2High 07-29-15 02:03 PM


Originally Posted by AnkleWork (Post 18025320)
That's not very detailed. What unit of measure would you use for the quantity of "resistance?"

For design purposes, more useful quantities include elasticity, strain, stress, deformation, section modulus, etc, all of which have specific definitions and units of measure.

OK, someone went to school to be a Mech Eng.

Congrats.

IF you will define them, I will select one.

AS I commented earlier, which ever one prevents the rim at the top from rubbing the brakes.

Otherwise, for each, define how to improve that metric :)

ThermionicScott 07-29-15 02:13 PM


Originally Posted by Fly2High (Post 18025252)
Then what prevents a wheel from rubbing on the front brake in a turn?

A modicum of brake pad clearance, plus the fact that the force you put on your wheels is generally "straight down" even when you're banking into a turn.

Fly2High 07-29-15 02:29 PM


Originally Posted by ThermionicScott (Post 18025397)
A modicum of brake pad clearance, plus the fact that the force you put on your wheels is generally "straight down" even when you're banking into a turn.

They only call for 1-2mm.

How much do you put?

And yes, I do pull out the feeler gauges.


If it is not flex, what could cause it?

CliffordK 07-29-15 02:30 PM


Originally Posted by ThermionicScott (Post 18025397)
A modicum of brake pad clearance, plus the fact that the force you put on your wheels is generally "straight down" even when you're banking into a turn.

Good point. Bike balance is a combination of gravity and centrifugal/centripetal force going through the wheels.

On a standing hill climb, however, forces may deviate somewhat from the wheel axis.

rmfnla 07-29-15 02:32 PM


Originally Posted by Fly2High (Post 18025445)
They only call for 1-2mm.

How much do you put?

And yes, I do pull out the feeler gauges.


If it is not flex, what could cause it?

I just fold a business card in half...

CliffordK 07-29-15 02:33 PM


Originally Posted by Fly2High (Post 18025445)
If it is not flex, what could cause it?

A wheel out of true could cause a periodic brake rub. Or, effectively reduce the clearance significantly.

1mm out of true.
1mm clearance.
And suddenly you have essentially zero clearance. Even if not rubbing on the stand, the slightest perturbation and it will pulse.

AnkleWork 07-29-15 02:37 PM


Originally Posted by Fly2High (Post 18025367)
OK, someone went to school to be a Mech Eng.

Congrats.

IF you will define them, I will select one.

AS I commented earlier, which ever one prevents the rim at the top from rubbing the brakes.

Otherwise, for each, define how to improve that metric :)

Not exactly.

I guess you don't want the details enough to actually think about them.

ThermionicScott 07-29-15 02:39 PM


Originally Posted by Fly2High (Post 18025445)
They only call for 1-2mm.

How much do you put?

And yes, I do pull out the feeler gauges.

If it is not flex, what could cause it?

Oh, they do flex. No one can argue that. I'm just saying why it generally isn't more than a mm or two for normal riding. If your wheels are true, with adequate tension, perhaps you just need to add a little more brake pad clearance.

Marcus_Ti 07-29-15 02:40 PM


Originally Posted by Fly2High (Post 18025445)
They only call for 1-2mm.

How much do you put?

And yes, I do pull out the feeler gauges.


If it is not flex, what could cause it?

It could also be that your wheel is stiff as stiff can be...but you are flexing the frameset

fietsbob 07-29-15 03:17 PM

Left out hub flange width and diameter .. a IGH or proper track rear hub is stiffer laterally because it is un dished

lacks the tension imbalance needed to pull the rim to the right
to make room for all those 'speeds' in a cassette

and the hub flanges are further apart.. flanges of the front hub are wider apart than a cassette Rear..

JohnDThompson 07-29-15 03:32 PM


Originally Posted by fietsbob (Post 18025601)
Left out hub flange width and diameter ..

And number of spokes.

fietsbob 07-29-15 03:37 PM

And what it's made out of .. Skyway uses a carbon or glass fiber reinforced Nylon

McBTC 07-29-15 04:36 PM

The issue isn't flex at the top of the wheel because all of the weight of the bike is essentially standing on the spoke at the bottom of the wheel.

FBinNY 07-29-15 05:14 PM

I didn't read all the answers above, so apoligies for duplicate info.

wheel stiffness depends almost entirely on the total amount of steel, namely the cross section X the no. of spokes.

Shorter spokes also increase stiffness, but the difference isn't great because the difference between the shortest (radial) and longest spokes possible is very small.

Rim lateral stiffness is also a factor, especially if spoke counts are lower, because stiffer rims spread the load more, bringing more spokes into play.

Then other factors come into play, including flange separation and spoke hole offset in rims, which affect the bracing angles & whether the spokes are woven over/under at the cross.

However TENSION HAS NO EFFECT ON STIFFNESS.


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