wheel balancing

neeb

Most bike wheels when fitted with tubes & tyres have an uneven weight distribution around the rim, you really notice this if you lift the rear wheel off the ground and spin it up to a reasonable speed with the cranks.

I guess some of this might be due to the wheel itself but it seems that a large percentage is due to the tube valve, especially if you have a deeper rim with a valve extender. I know that the campagnolo high-end wheels partially compensate for this by being a little heavier on the side opposite the valve.

Is it possible to balance your own wheels at home, optimising for the particular tubes/valves you are using? How would you go about doing this? My LBA could doubtless do it but they have a weeks or months long waiting list in the summer...

ugo.santalucia

There are wheel balancing machines, but they are largely un-necessary, given the speed and the RPM reached by a 28 inch wheel. I doubt your bike shop has one.
I would say, if you often exceed 50 mph on descends, it is worth thinking about it, otherwise the advantage is beyond perception. Once the wheel is true and round, it is balanced well enough for the job it's got to do.

Campagnolo should think on how to make their wheels serviceable, rather than wasting time balancing weights

neeb

Thanks, makes sense. I guess there would be no harm in sticking something small & heavy inside the rim on the side opposite the valve, however, just to balance things out a little?

ugo.santalucia

neeb wrote:

Thanks, makes sense. I guess there would be no harm in sticking something small & heavy inside the rim on the side opposite the valve, however, just to balance things out a little?

Probably not, I just wonder if then it will need to be moved every time you change to a new tyre. It is a nice idea, but largely un-necessary

TheEnglishman

I don't see that adding more weight to the rim is a good idea unless you go a lot of downhill only stuff.

Twostage

I balanced mine Front wheel is easier than rear because it is free spinning (no freehub rachet involved).
Front :-
Spin the wheel slowly - it will stop with the heaviest bit at the bottom. Put a spoke magnet on a spoke on the opposite side in the middle of the spoke. Spin the wheel again. If it still stops with the magnet at the top then move the magnet towards the rim, if it stops with the magnet at the bottom move it towards the hub. Repeat until the wheel stops at random places.
Rear :-
Move the wheel by hand one ratchet click at a time. It will sometimes click and roll a bit forwards and sometimes click and roll back. When it goes from rolling back to rolling forward the heaviest part of the wheel has just gone over the top. Put a spoke magnet at the opposite side in the middle. You can then rev up the back wheel adjusting the position of the magnet on the spoke until the bike moves the least in the bike stand.
As to whether it is worth it who knows ? The bike felt better afterwards but this could have been psychological. Its certainly better to be able to spin up the back wheel whilst its in the bike stand without it being like a bucking bronco.
Interestingly the valve part of the wheel wasn't the heaviest on either front or back.
By the way you will probably have to move the position of your speed sensor to the new position of the magnet and you end up with a magnet on a wheel that has no sensor.

P_Tucker

neeb wrote:

Thanks, makes sense. I guess there would be no harm in sticking something small & heavy inside the rim on the side opposite the valve, however, just to balance things out a little?

What would be the point?

neeb

P_Tucker wrote:

neeb wrote:

Thanks, makes sense. I guess there would be no harm in sticking something small & heavy inside the rim on the side opposite the valve, however, just to balance things out a little?

What would be the point?

You're a master of negativity aren't you? (and that's not just based on this post)

Twostage summed it up pretty well I think (thanks), but the way I see it is: 1) it can't do any harm, the extra weight would be a number of grams you could count on the fingers of one hand 2) it might be beneficial. Pascal's wager. If someone can prove to me against my intuition that there is no disadvantage whatsoever in having a wheel that is unbalanced enough to jerk around like a hammer drill when spun off the ground, I'll forget about it.

desweller

Are you sure the wheel is radially true? That would make it pretty unbalanced.

The valve is very light; if it's really out of balance it's unlikely that the valve is the cause.

neeb

DesWeller wrote:

Are you sure the wheel is radially true? That would make it pretty unbalanced.

The valve is very light; if it's really out of balance it's unlikely that the valve is the cause.

Actually, it's not quite round - it's somewhere between 0.5 and 1mm out (something else I'm planning on fixing as soon as I figure out what wrench I need for the hidden nipples), but the unbalancing is much worse with the tyre & tube in place - I'm using a valve extender and very light vredstein latex tubes, so the weight difference at the valve is maximised.

P_Tucker

neeb wrote:

P_Tucker wrote:

neeb wrote:

Thanks, makes sense. I guess there would be no harm in sticking something small & heavy inside the rim on the side opposite the valve, however, just to balance things out a little?

What would be the point?

You're a master of negativity aren't you? (and that's not just based on this post)

Twostage summed it up pretty well I think (thanks), but the way I see it is: 1) it can't do any harm, the extra weight would be a number of grams you could count on the fingers of one hand 2) it might be beneficial. Pascal's wager. If someone can prove to me against my intuition that there is no disadvantage whatsoever in having a wheel that is unbalanced enough to jerk around like a hammer drill when spun off the ground, I'll forget about it.

You are correct that it can't do any harm, but my the same logic it can't do any good either. But if it makes you happy knock yourself out - although you might want to consider taking up ma$turbation, as this will make you feel even better and make a similar amount of difference to your bike.

neeb

P_Tucker wrote:

but my the same logic it can't do any good either.

Well, no, not unless you change the premises. Looks like logic might not be your strong point. Do you have any strong points, apart from spouting unsubstantiated bollocks and generally being unhelpful and unpleasant? I'd put you down as a troll if I thought it was premeditated.

Twostage

I suppose it comes down to what you feel like doing. If you only did stuff because it made a big/measurable difference shimano would only sell sora cassettes. Titanium bottle cage bolts ? Bottles/Bottle cages that match the bike ?

I like being able to spin up the back wheel with the bike resting on the clamp rather than being clamped in to stop it from jumping (I'm lazy that way). In that way it has done good. Having balanced wheels won't make your bike worse so why not ?

neeb

Yup, I'm with you Twostage, I guess I'm just a chronic fettler... If something seems less than optimal and I can do something about it I will get the itch to fix it.

bottom_bracket

I thought it was happening because my wheels aren't top end ones, but having read this I'm going to try to balance mine. Even if it's only a psychological help I'll take it, I need all the advantage I can get!

Lookyhere

I ve some C35 tubular wheels that are so out of balance (and thats without a tub fitted) its untrue, the recently acquired Fulcrum zeros are perfectly balanced...but at any speed on any road, cannot tell the differnce between the two.

P_Tucker

neeb wrote:

P_Tucker wrote:

but my the same logic it can't do any good either.

Well, no, not unless you change the premises. Looks like logic might not be your strong point. Do you have any strong points, apart from spouting unsubstantiated bollocks and generally being unhelpful and unpleasant? I'd put you down as a troll if I thought it was premeditated.

Yes, two strong points:

1. I'm practically always right
2. I don't waste time doing things that will make no difference to my bike

balthazar

neeb wrote:

P_Tucker wrote:

neeb wrote:

Thanks, makes sense. I guess there would be no harm in sticking something small & heavy inside the rim on the side opposite the valve, however, just to balance things out a little?

What would be the point?

You're a master of negativity aren't you? (and that's not just based on this post)

Twostage summed it up pretty well I think (thanks), but the way I see it is: 1) it can't do any harm, the extra weight would be a number of grams you could count on the fingers of one hand 2) it might be beneficial. Pascal's wager. If someone can prove to me against my intuition that there is no disadvantage whatsoever in having a wheel that is unbalanced enough to jerk around like a hammer drill when spun off the ground, I'll forget about it.

I think Pascal was joking with that wager, though it's often cited so solemnly..! Regardless, you're dangerously close to the wrong end of the burden of proof..!

This exchange might be interesting to you if you want a long read.

http://yarchive.net/bike/wheel_balancing.html

I think Jobst takes a sensible and authoritative line, especially in this last point:

"Subsequently I put a significant wrap of 1/8" thick solder wire around
one spoke at the rim and coasted down a hill no-hands, observing the
incidence and intensity of shimmy. There was no difference between
balanced and imbalanced wheel. Rather than hypothesize about it, a
test of theory does a lot to put it into perspective."

neeb

At last, some constructive debate..

balthazar wrote:

I think Pascal was joking with that wager, though it's often cited so solemnly..!

Yes he was, but he did hit on a useful rule of thumb - if you start from the assumption that a course of action may at worst be harmless but at best significantly beneficial, you may as well take it, depending perhaps on the trouble involved in doing so and the magnitude and probability of the positive outcome. The problem with Pascal's wager in its original application of course was that it didn't consider abject betrayal of one's own belief system to be a significantly negative outcome. No such moral problems with sticking a bit of blu-tack under a veloplug though..

This exchange might be interesting to you if you want a long read.

http://yarchive.net/bike/wheel_balancing.html

Long, but interesting - I learned stuff! I'm now prepared to accept that there may be no immediately perceptible benefits to wheel balancing, as in being able to feel a wobble on the road or being at greater risk of speed shimmy. However, I'm going to hypothesise that there may still be slight benefits in terms of efficiency, especially at higher speeds. I'm quite prepared for this to be refuted by someone with a better knowledge of physics. Firstly, I found the following extract from that link pretty interesting:

>> You removed a principal constraint by allowing the wheel to spin
>> freely. In reality the wheel is constrained to roll on the ground
>> with a tire so hard that its imbalance forces are insignificant
>> to the compliance of the tire, unlike hat of a car tire that has
>> about the same compliance and about 40 times the mass. They are
>> not alike.

> Oh, I now understand. You are correct - the compliance of the tire
> at the pressures we used, 110-130 PSI, is minimal when compared to
> the 3 grams of wheel imbalance. I don't know how to explain this.

The point is that car tires bounce completely off the road when used
with imbalance and they do this because they have a low spring rate
compared to their mass. You can estimate that by the rate at which
the two wheel bounce... like a table tennis ball and a basket ball.
The bicycle tire is more like the table tennis ball

So the reason you get perceptible wobble with an unbalanced car wheel even at some speeds that can also be reached by bicycles is that the mass of the car tyre (and hence the differences in centrifugal force at different points on the circumference) is much greater in relation to the tyre's compliance. It's heavy in relation to its bounciness, so it bounces more easily. You wouldn't get any wobble with the same car tyre if it was solid (unbouncy), although the ride would be considerably less smooth... With a bicycle rim/tyre the weight is much less significant in relation to its bounciness when properly inflated.

Note however that the effects of an unbalance will get continually greater with increasing speed - the 3 grams mentioned in the quote above will produce an ever increasing centrifugal force at greater speeds (F=ma, the acceleration in this case being the angular deceleration), so presumably there would be some theoretical speed at which the wheel would start to bounce perceptibly, even if you would never reach this in practice.

What I want to hypothesise however is that even although the imbalance forces are not significant enough in relation to the bicycle tyre's compliance to create a perceptible wobble, they may nonetheless slightly reduce rolling efficiency, this becoming more significant at higher speeds and on smoother roads. In effect there is slightly more downwards force on the tyre at a particular point in the wheel's rotation, which is presumably translated into slightly greater tyre deformation. So even although the tyre is completely absorbing the imbalance forces and you can't feel it, it is doing so by deforming once every revolution. It's almost exactly as if you were riding over a surface that had a tiny little bump in it once every 2.1 meters. This extra deformation force will slightly increase rolling resistance.

P_Tucker

jesus wept. Of the total resistance facing the rider, what percentage do you hypothesise that the tyre deformation caused by a slightly imbalanced rim would be? To the nearest 0.0000000001% please.

neeb

P_Tucker wrote:

jesus wept. Of the total resistance facing the rider, what percentage do you hypothesise that the tyre deformation caused by a slightly imbalanced rim would be? To the nearest 0.0000000001% please.

I've no idea - do you? If not, how do you know it's not significant?

In any case it will be more the smoother the road is and the faster the speed is.

P_Tucker

neeb wrote:

P_Tucker wrote:

jesus wept. Of the total resistance facing the rider, what percentage do you hypothesise that the tyre deformation caused by a slightly imbalanced rim would be? To the nearest 0.0000000001% please.

I've no idea - do you? If not, how do you know it's not significant?

In any case it will be more the smoother the road is and the faster the speed is.

Do you think you're the first person to realise that a bike wheel isn't perfectly balanced because of the valve? Given that the physics is about A-level standard, do you not think that someone at some point has done the sums? And you do not think that if there was anything in it whatsoever, wheels would come pre-built with a weight opposite the valve hole?

FFS. If you'd spent 15 of the seconds you'd wasted thinking about this training it would have had a greater effect on your cycling speed.

neeb

P_Tucker wrote:

neeb wrote:

P_Tucker wrote:

jesus wept. Of the total resistance facing the rider, what percentage do you hypothesise that the tyre deformation caused by a slightly imbalanced rim would be? To the nearest 0.0000000001% please.

I've no idea - do you? If not, how do you know it's not significant?

In any case it will be more the smoother the road is and the faster the speed is.

Do you think you're the first person to realise that a bike wheel isn't perfectly balanced because of the valve? Given that the physics is about A-level standard, do you not think that someone at some point has done the sums? And you do not think that if there was anything in it whatsoever, wheels would come pre-built with a weight opposite the valve hole?

FFS. If you'd spent 15 of the seconds you'd wasted thinking about this training it would have had a greater effect on your cycling speed.

:shock: .... Don't know what your problem is PT, but it's pretty clear you have some psycho-social "issues"...

Twostage

P_Tucker wrote:

Do you think you're the first person to realise that a bike wheel isn't perfectly balanced because of the valve? Given that the physics is about A-level standard, do you not think that someone at some point has done the sums? And you do not think that if there was anything in it whatsoever, wheels would come pre-built with a weight opposite the valve hole?

Nope. That wouldn't work. The fact there is a hole there will partially compensate for the weight of the valve and like I said when I balanced the wheels on my commuter the heaviest part of the wheel was not where the valve was.

neeb

Twostage wrote:

P_Tucker wrote:

Do you think you're the first person to realise that a bike wheel isn't perfectly balanced because of the valve? Given that the physics is about A-level standard, do you not think that someone at some point has done the sums? And you do not think that if there was anything in it whatsoever, wheels would come pre-built with a weight opposite the valve hole?

Nope. That wouldn't work. The fact there is a hole there will partially compensate for the weight of the valve and like I said when I balanced the wheels on my commuter the heaviest part of the wheel was not where the valve was.

Actually, the Campagnolo/Fulcrum Eurus/Shamal/Racing 1/Racing 0 wheels do come with more weight on the rim opposite the valve side, but it's completely hit-and-miss as so much depends on the weight/length of the valve and (as you have found out) natural variation in the weight distribution on the rims/tyres.

P_Tucker

neeb wrote:

P_Tucker wrote:

neeb wrote:

P_Tucker wrote:

jesus wept. Of the total resistance facing the rider, what percentage do you hypothesise that the tyre deformation caused by a slightly imbalanced rim would be? To the nearest 0.0000000001% please.

I've no idea - do you? If not, how do you know it's not significant?

In any case it will be more the smoother the road is and the faster the speed is.

Do you think you're the first person to realise that a bike wheel isn't perfectly balanced because of the valve? Given that the physics is about A-level standard, do you not think that someone at some point has done the sums? And you do not think that if there was anything in it whatsoever, wheels would come pre-built with a weight opposite the valve hole?

FFS. If you'd spent 15 of the seconds you'd wasted thinking about this training it would have had a greater effect on your cycling speed.

:shock: .... Don't know what your problem is PT, but it's pretty clear you have some psycho-social "issues"...

I've wouldn't deny it. However, resorting to personal insults is the MO of the internet argument loser. Fact.

neeb

P_Tucker wrote:

I've wouldn't deny it. However, resorting to personal insults is the MO of the internet argument loser. Fact.

Not an insult, just an observation. The problem is that your "arguments" are mostly just invective, so it's pointless and a waste of time to refute them because you'll just come back with some other cheap comment that distracts from the issue.

Anyway, since you insist (and this is the last time I'll be bothered..)

Do you think you're the first person to realise that a bike wheel isn't perfectly balanced because of the valve?

No of course not, but what's that to do with it whether it's worth correcting for it or not?

Given that the physics is about A-level standard, do you not think that someone at some point has done the sums?

Possibly, but I wouldn't bet on it - it's amazing how much accepted wisdom about bikes and cycling has never been critically examined, there's very little out there and with the exception of two or three studies/books most of what we know comes from people speculating on the internet.

And you do not think that if there was anything in it whatsoever, wheels would come pre-built with a weight opposite the valve hole?

As above, some (e.g. Campag) are.

FFS. If you'd spent 15 of the seconds you'd wasted thinking about this training it would have had a greater effect on your cycling speed.

Yup, you may be right, but I have a stinking cold at the moment, hence yesterday and today I'm (amongst other things) twiddling my thumbs speculating about this kind of stuff instead of getting a ride in before the TdF highlights. I'd be truing my wheels instead if I could just get hold of a 3/16" internal nipple spoke wrench at short notice..

neeb

P.S. PT, have you ever thought it might be interesting just to be friendly, balanced and considerate for a change? You never know, you might enjoy it. FFS.

P_Tucker

neeb wrote:

P.S. PT, have you ever thought it might be interesting just to be friendly, balanced and considerate for a change? You never know, you might enjoy it. FFS.

There are enough people like that, and they're universally utterly dull and pointless. The world needs more people to tell it like it is, unencumbered by social conventions like "manners". FFS

neeb

P_Tucker wrote:

There are enough people like that, and they're universally utterly dull and pointless. The world needs more people to tell it like it is, unencumbered by social conventions like "manners". FFS

Completely disagree, I think there aren't nearly enough, hence most of the problems in the world. And manners are something very different from being considerate, in fact they are sometimes used as a subtle way of being inconsiderate. Also, you don't "tell it like it is" by always looking for the negative/critical/adversarial interpretation, that just gets in the way because it makes people defensive, and defensive people aren't thinking about what "it" is (although it does have a role in hypothesis testing / falsifying / bullshit detecting).

Also I think you'll find that many of the most un-dull, un-pointless people in the world (the really talented great writers/scientists/artists etc) are remarkably friendly, balanced and considerate - for every tortured misanthropic genius there are about 10 mellow, incredibly nice ones - when was the last time you saw an aggressive theoretical physicist?

P_Tucker

Tuesday