Bicycle Mechanics - 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?

Bike tires do not require balancing.

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.

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.

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.

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.

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.

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.

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.

The reason that car tires need to be balanced is that car wheels go in pairs. Bike wheels go one by one.

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?

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.

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.

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.

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

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.

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.

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.

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.

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.

Thanks a lot... you've all been very helpful.

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". ;)

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.

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.

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.

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 :D ), 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....

Another problem with the valve story is that bike tires have 2-3 times the air pressure that car (and motorcycle?) tires do, so 2-3 times more force would be needed to open them.

That valve compression story was widely reported at the time. No one challenged it then. I always believed it.

That valve compression story was widely reported at the time. No one challenged it then. I always believed it.

Can't be true (excepting the possibility of a defective valve, of course). 120mph is no big deal on a motorcycle -- I've exceeded that speed any number of times myself (on a racetrack, of course). As someone pointed out, GP bikes approach 180mph or more, and drag bikes go far beyond that.

It is true that the larger diameter of bicycle wheels might result in more centrifugal force being applied to the valve (although wouldn't the much greater weight of motorcycle wheels and tires have to be taken into account?), but that would be compensated for by the far higher tire pressure in bicycle tires.

And I would have thought that any competitive cyclist would be running Presta valves (if not tubulars). Am I wrong? I'm not a competitive cyclist, so I'm not sure about these things.

Are car/motorcycle and bike Schraeder valves equipped with identical springs?

It is true that the larger diameter of bicycle wheels might result in more centrifugal force being applied to the valve

No, smaller radius for a given speed at the the rim will result in more centrifugal force, not less. Consider the Earth...you're going around the "rim" of the earth at something like 1000 miles an hour, depending on your latitude. But you feel virutally no tendency to fly off, because the raduis about which you make that turn is so huge. It's also the same reason tight corners on the road hare harder to take at speed thean gradual bends.



(although wouldn't the much greater weight of motorcycle wheels and tires have to be taken into account?),

Weight has no impact on the acceleration a turning object feels. Centripetal acceleration, which causes the reaction felt as centrifugal force, is given by


a = v²/r

where v is the velocity of the turning object (or in the case of a valve stem, approximately the road speed), and r is the radius of the turn (for valve stem, wheel radius). Mass is not included in the calculation for this acceleration. A heavy rim and a light rim of the same size will cause the same response in the valve stem.

You do need to factor the mass of the valve core in deciding if it could depress the spring, because the acceleration pushes the pin against the spring with a force proportional to the pin's weight. (F = ma and such). While acceleration at the rim isn't a function of mass, force is. If you know the weight of the valve core, and the spring constant of that little valve spring, you can solve this problem.

I don't, so I won't.

Are car/motorcycle and bike Schraeder valves equipped with identical springs?
There are at least 2 types of Scrader valve cores. One has a longer pin with an external spring that reduces the pressure necessary to open the valve. They were used in bicycles because the valve could be opened by air pressure alone. They were inflated with a pump that didn't have a pin to open the valve. That way, you didn't lose pressure when the fitting was unscrewed from the stem.


em

Late to the thread but to get back to balancing. I run a old 10 spd road bike as my commuter. 27" with 1 1/4" tires. LOW TECH! In the spirit of making myself more visible I put one reflector on each wheel oposite the presta valve. (when the rims are naked they stop so valve hole is at top).

Riding down a hill shortly after I felt an odd forward/backward pulsing I had never felt before. I forgot about it. Using a poor man's repair stand (rope from the garage door track) I was working on the bike. When I got the rear spinning fast the whole bike got into a rather violent harmonic back and forth pendulum mode from the ropes which were about 4 feet long.

Lesson I learned? These darn reflectors sure do put the wheels out of balance. Reading this thread the solution seems to be but two on the wheel to offset. Not a bad idea.

So. Can wheels be out of balance? Sure, hang your own bike and see how much. Can you feel it on the road? I could. Did it make things unsafe? Not at all. Does it matter? Doubt it. Can this topic generate over 25 replies? Yup. Must be cold outside and we're bored!

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 :D ), 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....

I'm not going to get into a big discussion on whether there is enough centripital force to compress a tire valve spring on a motorcycle, but suffice it to say I didn't pass inspection at a CCS sanctioned motorcycle race once because I didn't have metal valve caps with an O ring seal. The tech guy said it was because at hight speed, the valve can open and lose air.

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.
Done the same regularly and no vibration...except on a wheel with a flat spot once... bike wheels and tires are very precisely manufactured hence the high cost.

I'm not going to get into a big discussion on whether there is enough centripital force to compress a tire valve spring on a motorcycle, but suffice it to say I didn't pass inspection at a CCS sanctioned motorcycle race once because I didn't have metal valve caps with an O ring seal. The tech guy said it was because at hight speed, the valve can open and lose air.

Good point -- the valve stem caps on my motorcycle are exactly that kind -- O-ring sealed. I guess if anyone is concerned about the valves on bicycle wheels, he or she can pick up a pair of O-ring caps at their local auto parts store.

I can see how an uncapped and unscrewed presta valve would lose pressure at high speeds. Not a good thing to overlook...