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Old 01-17-06, 07:49 AM   #1
niceguy
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Do Bike Tires Need Balancing just like Car Tires Do?

Just wondering if at higher speeds (rpm), the tires of the bikes start vibrating just like car tires do. That's why car tires are balanced (weight is distributed evenly on the rim by attaching lead weights in strategic places) so that this does not happen. Has this ever been done with bike tires as well?
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Old 01-17-06, 07:59 AM   #2
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Bike tires do not require balancing.
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Old 01-17-06, 08:28 AM   #3
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Most bike wheel vibration at speed comes from out-of-round or lumpy tires. Bike wheels are rarely balanced except by the truly anal about such things.
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Old 01-17-06, 08:37 AM   #4
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Quote:
Originally Posted by niceguy
Just wondering if at higher speeds (rpm), the tires of the bikes start vibrating just like car tires do. That's why car tires are balanced (weight is distributed evenly on the rim by attaching lead weights in strategic places) so that this does not happen.
I have not encountered those, particularly that my speeds are low, but I have heard about the vibrations in the context of a criticism of the wheel reflectors. The claim was that a reflector, required in many places by law, can put the wheel enough off-balance to make it vibrate dramatically at high speeds. Myself, driven by safety, I use normally two reflectors that I put on the opposite sides.
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Old 01-17-06, 09:26 AM   #5
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Bike tires don't see the kind of sustained high speeds that car tires do, and bike tires are only designed for 1/20 the miles of most car tires...designed to be replaced rather than serviced.
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Old 01-17-06, 09:48 AM   #6
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A bicycle tire really won't affect the dynamic balance of the wheel in any significant way. Most wheels do, however, have an imbalance caused by the rim joining method. On every wheel I've ever seen, the valve hole will come to rest at the top (this may not be true for all wheels). The only ones I've ever heard of that address this issue are Campagnolo and their subsidiary Fulcrum, who claim that their wheels are dynamically balanced. As you can guess from the responses you've gotten so far, most people see it as a non-issue.
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Old 01-17-06, 09:50 AM   #7
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Bike tires don't see the kind of sustained high speeds that car tires do, and bike tires are only designed for 1/20 the miles of most car tires...designed to be replaced rather than serviced.
The concern isn't tire wear, it's bearing wear.
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Old 01-17-06, 09:55 AM   #8
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The claim was that a reflector, required in many places by law, can put the wheel enough off-balance to make it vibrate dramatically at high speeds. Myself, driven by safety, I use normally two reflectors that I put on the opposite side
I've seen those reflectors cause another problem when they are applied without rechecking spoke tension after installation. A lot of times they increase the tension and create a flat spot.
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Old 01-17-06, 10:18 AM   #9
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With a light enough wheel at high speeds, you're liable to notice some wheel wobble. However, this has less to do with the tire than it does the valve stem. And it's usually not enough to cause problems. Unless you spin at 40mph plus.
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Old 01-17-06, 10:22 AM   #10
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The reason that car tires need to be balanced is that car wheels go in pairs. Bike wheels go one by one.
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Old 01-17-06, 10:28 AM   #11
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Originally Posted by timcupery
The reason that car tires need to be balanced is that car wheels go in pairs. Bike wheels go one by one.
What difference do you think that makes?
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Old 01-17-06, 10:54 AM   #12
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Originally Posted by juicemouse
What difference do you think that makes?
Because cars need balance between the right and left rear wheel, and the right and left front wheel, because they're balanced side-to-side based on the tires. Bikes are balanced side-to-side based on the rider's steering and body control. Sorry, I should have explained this in the prev. post.
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Old 01-17-06, 11:02 AM   #13
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Quote:
Originally Posted by timcupery
Because cars need balance between the right and left rear wheel, and the right and left front wheel, because they're balanced side-to-side based on the tires. Bikes are balanced side-to-side based on the rider's steering and body control. Sorry, I should have explained this in the prev. post.
The issue here isn't a seesaw-type balance (technically known as static balance) that would affect the handling of the vehicle or anything like that, it's dynamic balance that causes vibration (leading to premature wear of components). Car and truck tires are balanced individually, not with respect to one another. If your scenario were true, you'd have to put 150 lbs of stuff in the passenger seat every time you were driving solo.
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Old 01-17-06, 11:10 AM   #14
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I've gone just over 60 MPH on my road bike, multiple times, and had no problems with wobble or vibration.

Do not try this yourself however, and IANAL.
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Old 01-17-06, 01:05 PM   #15
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Quote:
Originally Posted by timcupery
Because cars need balance between the right and left rear wheel, and the right and left front wheel, because they're balanced side-to-side based on the tires. Bikes are balanced side-to-side based on the rider's steering and body control. Sorry, I should have explained this in the prev. post.
So why are motorcycle tires balanced?

I had a pretty badly unbalanced motorcycle tire that would hop terribly at 90+ mph (on a racetrack).

I've never gone anywhere near 90 mph on a bicycle and I've never bothered balancing the wheels.

Az
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Old 01-17-06, 05:49 PM   #16
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Quote:
Originally Posted by 2_i
I have not encountered those, particularly that my speeds are low, but I have heard about the vibrations in the context of a criticism of the wheel reflectors. The claim was that a reflector, required in many places by law, can put the wheel enough off-balance to make it vibrate dramatically at high speeds. Myself, driven by safety, I use normally two reflectors that I put on the opposite sides.
Wheel reflectors are very lightweight and are unlikely to cause a noticeable effect. If you're concerned, put the reflector opposite the valve stem.
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Old 01-17-06, 05:53 PM   #17
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Quote:
Originally Posted by timcupery
The reason that car tires need to be balanced is that car wheels go in pairs. Bike wheels go one by one.
Sorry, but this is not true. Car tires require balance because they have significant weight at the tread and spin at high speed. Bike tires rarely spin at high speed and have very little weight in the tires. Consequentially, small variations in tire weight do not result in any significant vibration forces.
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Old 01-17-06, 05:54 PM   #18
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Originally Posted by Az B
So why are motorcycle tires balanced?

I had a pretty badly unbalanced motorcycle tire that would hop terribly at 90+ mph (on a racetrack).

I've never gone anywhere near 90 mph on a bicycle and I've never bothered balancing the wheels.

Az

Motorcycle tires are significantly heavier than bicycle tires and may have more of an imbalance. Of course, at 90 mph, even a little imbalance can spoil your afternoon.
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Old 01-17-06, 08:05 PM   #19
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Originally Posted by supcom
Sorry, but this is not true. Car tires require balance because they have significant weight at the tread and spin at high speed. Bike tires rarely spin at high speed and have very little weight in the tires. Consequentially, small variations in tire weight do not result in any significant vibration forces.
Quote:
Originally Posted by juicemouse
The issue here isn't a seesaw-type balance (technically known as static balance) that would affect the handling of the vehicle or anything like that, it's dynamic balance that causes vibration (leading to premature wear of components). Car and truck tires are balanced individually, not with respect to one another. If your scenario were true, you'd have to put 150 lbs of stuff in the passenger seat every time you were driving solo.
Okay, thanks for the correction. Sorry to mislead on this. I shouldn't comment too much on cars since I don't have one - I just live by bike.

Last edited by TallRider; 01-17-06 at 09:21 PM.
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Old 01-17-06, 08:46 PM   #20
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Thanks a lot... you've all been very helpful.
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Old 01-17-06, 10:23 PM   #21
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Okay, thanks for the correction. Sorry to mislead on this. I shouldn't comment too much on cars since I don't have one - I just live by bike.
No worries. The sticker on the back of my fender reads "One Less Car".
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Old 01-17-06, 10:46 PM   #22
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Originally Posted by niceguy
Just wondering if at higher speeds (rpm), the tires of the bikes start vibrating just like car tires do. That's why car tires are balanced (weight is distributed evenly on the rim by attaching lead weights in strategic places) so that this does not happen. Has this ever been done with bike tires as well?
I know a guy who HAD to balance his wheels. John Howard went to break the ~140 MPH drafting speed records. At those speeds he confirmed that weight had to be added opposite the valve stem to keep the wheel balanced. He also had a tube (schraeder valve) go flat at about 120 MPH. The wheel ws spinning so fast that the valve core depressed the internal spring, letting the air out. He survived leaving the slipstream of the powerful car he wss drafting and solved the air loss by putting an ordinary valve cap on the stem. He showed the ~390 gear-inch BMX type bike at a Bicycle Club of Irvine meeting years ago.
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Old 01-17-06, 11:05 PM   #23
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Adding weight opposite the valve stem will make the imbalance worse, not better. Juicemouse explained that the rim joint adds weight. Even when opposed by the valve stem, the joint is still heavier on every bike I've seen.

As for John Howard's tire going down due to compression of the valve core spring.... why doesn't this happen on cars and motorcycles frequently??? My guess is that it was a bad valve core. Adding a cap isn't a solution, at least not a sound one.
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Old 01-18-06, 12:56 PM   #24
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why doesn't this happen on cars and motorcycles frequently???
I can believe that centrifugal force would cause the valve core to depress itself. A 700c rim at 100 mph feels an acceleration of 680 g at the rim. That's quite a centrifuge. No wonder a Schrader valve might fail under that kind of force.

The reason it doesn't happen to cars is because the valve stem on every car wheel I've ever seen doesn't point at the hub. It's angled outward to be accessible. I presume motorcycles are the same.
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Old 01-18-06, 07:32 PM   #25
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Originally Posted by aerodave
I can believe that centrifugal force would cause the valve core to depress itself. A 700c rim at 100 mph feels an acceleration of 680 g at the rim. That's quite a centrifuge. No wonder a Schrader valve might fail under that kind of force.

The reason it doesn't happen to cars is because the valve stem on every car wheel I've ever seen doesn't point at the hub. It's angled outward to be accessible. I presume motorcycles are the same.
Nope. On motorcycles they point straight up from the rim. I'm glad my valve cores didn't "compress" when I did over 126 mph on a Kawasaki some time back. A 700C rim is larger in diameter than the typical motorcycle wheel, which would mean the motorcycle wheel would have more RPM at a given speed, therefore, more force to compress the valve core spring, (which doesn't happen). GP500 race motorcycles go insanely fast (faster than me on my Kawasaki ), better than 180 mph, if I recall correctly, and they don't have the alleged problem.

I'm reluctant to buy the spring compression story, even if it's involving my buddy John Howard....
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