[Typetwelve]

This may be a dumb question but it has had me scratching my nogin for some time now.

Coming from a background in cars...tire balance once mounted it paramount. If any of you have ever dropped a balance weight you know what I'm talking about.

Now, I know car travel at higher speeds but a lightweight bike running a sub 1" wide tire inflated at 90+ PSI seems to me that if it were out of balance, you'd be able to feel it.

I've learned that no wheel is perfectly balanced, nor is a tire. Now...add a tube to the mix and I would swear it would ride funny...

But it never does.

I'll probably never figure it out but it's always intrigued me.

 

[Randy99CL]

I've had some bike wheels that seemed to be pretty far out of balance when spun in a stand, but still rode well.

I think it is a large diameter, light weight, (comparatively) low RPM thing.

I try to balance the wheel with the speed magnet but it doesn't seem to make any difference. It's pretty flat around here though, I don't see high speeds.

 

[rruff]

I did the calculations once. As I recall the typical out of balance resulted in a +-~2lb force differential at 50 mph. It just isn't enough to notice.

 

[Lelandjt]

I sure do feel it on my dirtbike when htting the 60s on pavement. I've even felt it on DH bikes with their 1350g tires when going 40 on pavement. Roadbike wheels just don't have enough weight to create enough force to feel.

 

[hicksycle]

I went to a bike show in Japan where one stand was balancing peoples wheels for free. The head a way to measure force and a computer and a display which told them where to add weight.

 

[PlatyPius]

This may be a dumb question but it has had me scratching my nogin for some time now.

Coming from a background in cars...tire balance once mounted it paramount. If any of you have ever dropped a balance weight you know what I'm talking about.

Now, I know car travel at higher speeds but a lightweight bike running a sub 1" wide tire inflated at 90+ PSI seems to me that if it were out of balance, you'd be able to feel it.

I've learned that no wheel is perfectly balanced, nor is a tire. Now...add a tube to the mix and I would swear it would ride funny...

But it never does.

I'll probably never figure it out but it's always intrigued me.

I've always wondered if maybe wheel balance was the cause of the otherwise unexplained "shimmy" people experience at high speeds occasionally on some road bikes.

 

[headloss]

I can notice an unbalanced car wheel at 25mph or slower... so I don't think it's a speed thing. It might have to do with weight and/or surface area or overall diameter. *shrugs* I always just assumed it was the biproduct of having two wheels on the same axel... but now that I think about it, that doesn't even make sense due to the differential.

 

[Typetwelve]

I've always wondered if maybe wheel balance was the cause of the otherwise unexplained "shimmy" people experience at high speeds occasionally on some road bikes.

Could be.

I feel better knowing I'm not the only one who thinks about this. I often have my bike up into the high 30's, low 40's in the speed range...I've yet to have any issues but this thought is always on my mind.

 

[slomofron]

rruf is true! For a bicycle rim/tire combo there is not enough mass to worry about. I used to work for a MAJOR auto repair balancer maker! I can tell you honestly it is not the diameter, it is the mass weight that means something. We are talking bike tires that weigh @350 grams....lets talk tire that weigh 25 lbs!! plus. On that type of tire we are talking a 1/4oz might cause a vibration @30mph and it is minor!! On bike tires we do not have to worry.....it is nonsense.

 

[Kerry Irons]

Now, I know car travel at higher speeds but a lightweight bike running a sub 1" wide tire inflated at 90+ PSI seems to me that if it were out of balance, you'd be able to feel it.

I've learned that no wheel is perfectly balanced, nor is a tire. Now...add a tube to the mix and I would swear it would ride funny...

But it never does.

Think about what is happening with an out of balance car wheel. The tire is compressed from the force of the off center mass and the rim therefore moves off-center from it's neutral position. Then as the off-center weight moves around the rim it acts to try to lift the wheel off the ground. In one case it is working against the tire pressure/stiffness and in the other against the suspension spring and shock absorber.

Can you picture a bicycle tire at 90 psi compressing enough to cause this to happen? And what about the force that is opposing the "lifting" action as the weight rotates upward? It's the entire weight on that wheel.

There is no way that any realistic amount of bicycle wheel imbalance could trigger any movement either to compress the tire or lift the wheel. No way.

 

[rcb78]

One other thing, as an owner of a car that is known for it's "shimmies", it's really more of a harmonic issue as it will happen at multiple different speeds. If my wheels are out of balance, I get shakes at 15mph, and again at about 45-50 mph. Any other range and the car is smooth. And we're talking violent, part breaking shakes.
Cars have tons of room for movement, they are aren't rigid. The suspension will actuate, and in some cases, tie bars and control arms will flex in their bushes and allow movement that might have been damped if the weight of the car was rigidly connected, not suspended.

 

[looigi]

Easy enough to do an experiment. Stick on a few OZs of wheel balance weights to your rim (such that they don't interfere with rotation or the brakes) and see how much weight and at what speed the imbalance becomes evident. I think you'll find that it takes considerably more imbalance than what road bike wheels typical have before it becomes an issue.

 

[JCavilia]

I've always wondered if maybe wheel balance was the cause of the otherwise unexplained "shimmy" people experience at high speeds occasionally on some road bikes.

It's complex, but it's not "unexplained." It's a phenomenon of resonance involving wheel, headset, frame flex, rider input, and other factors. Wheel imbalance may be a small factor in some cases, but the evidence suggests it's a very minor one. For one thing, shimmy can almost always be stopped immediately by taking weight off the saddle and damping top-tube movement with the knees. You haven't changed wheel balance when you do that.

You could test by taking a bike that doesn't shimmy and adding weights to create extra imbalance in the front wheel. My guess is it still won't shimmy.

 

[OldChipper]

At top speed, 45+ mph, I can definitely feel a bit of a "hop" in my Zipp carbon clinchers. I've checked the rims themselves, and they aren't out of round. I assume the hop is from imbalance since the needed valve stems are pretty long (60mm) and therefore a bit heavier than average. I assume it's a percentage thing i.e. % that the imbalance weight is of the rim itself. I've never noticed it with aluminum rims.

 

[Kerry Irons]

At top speed, 45+ mph, I can definitely feel a bit of a "hop" in my Zipp carbon clinchers. I've checked the rims themselves, and they aren't out of round. I assume the hop is from imbalance since the needed valve stems are pretty long (60mm) and therefore a bit heavier than average. I assume it's a percentage thing i.e. % that the imbalance weight is of the rim itself. I've never noticed it with aluminum rims.

I'd be more likely to focus on a tire that is not uniform. Again: in order for there to be a hop the tire has to compress from the force of the rotating out-of-balance weight. Not happening with the weights involved and the tire pressures used.

 

[upstateSC-rider]

I come from an automotive background also and my best guess is that there just isn't enough mass to be noticeable.
I always mount my spoke magnet on the opposite side of the valve stem to try and offset the additional mass but don't think it would make a difference.

 

[jmpsmash]

i always position the tire labels on the opposite end of the valve stem.

 

[nOOky]

Some motorcycle tires have a mark indicating where the light spot on the tire is for consideration when mounting and balancing the tire. I'm guessing that a 200 gram bicycle tire just doesn't have enough variance throughout it's mass to cause a noticeable effect as others have suggested above.

 

[Kerry Irons]

I always mount my spoke magnet on the opposite side of the valve stem to try and offset the additional mass but don't think it would make a difference.

For aluminum rims, the heaviest point is at the rim joint, not where the valve is (tire installed). If you let your wheel find its heavy point, typically the valve will be up rather than down.

 

[froze]

Today most decent wheels are dynamically balanced at the factory which then just leaves the tire, and tires only weigh 7 to 8 ounces whereas the average wheel weight used to balance a car tire is 4 ounces. A bicycle tire is almost too light to cause an issue with imbalance...note I said almost. I once installed a computer magnet on a spoke directly adjacent to the valve stem and the tire/wheel had an imbalance that was felt at 25 to 30 mph, I moved the magnet to the opposite side from the valve stem and it disappeared. I've also experienced imbalance with tires, but by moving the tire 1/4 of a turn one way or the other usually took care of the problem. Today's tires are built more precise though than tires of old and I haven't had an imbalanced tire in over 15 years...except for when I put the magnet in the wrong place.

And speaking of this, car tires are installed by goons. There is on all tires a "heavy" dot, it's a dot that indicates that side of the tire is a bit heavier, if the tire goons installed tires with the dot directly opposite of the valve stem they would use less weight to balance tires. Actually the best way to balance a car tire is to shave the tire and not add weight, but no one does that.