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TLDR

Taking into account both drive safety and mechanical stresses, is a wheel imbalance of 50 g (~2 Oz) a safe threshold for a generic road motorcycle? Does the figure change if we consider motorcycles capable of more than 300 km/h?

By "50 g imbalance" I mean such an imbalance that can be corrected by applying a weight of 50 g at the appropriate location on the rim.


I had a guy in a tire shop telling me that balancing motorcycle wheels after a tire change is basically wasting time and balancing weights, whose glue residues are sometimes very annoying to remove.

He added that, on a common road motorcycle (17" rim), a weight imbalance up to 50 g does not cause any issue, and that modern processes for wheel and tire production ensure being well within that tolerance.

I was skeptical, but I could not to find official data from manufacturers, so I secured a 50 g rock to the inside of my front wheel and drove up to speeds reasonably achievable on open roads. I was surprised of not being able to tell the difference in any circumstance, in particular I could not feel any added vibration, even if I was really paying attention.

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  • So what are you asking?
    – Solar Mike
    Jun 17, 2020 at 16:03
  • That levels of unbalance is equivalent to whacking the wheel bearing with a 10-pound hammer, a few hundred times every minute. If the wheel bearing and suspension absorbs that so you don't feel it, that's fine, but ask yourself if you really need to give your bike that sort of treatment to save a few dollars on balancing.
    – alephzero
    Jun 17, 2020 at 16:11
  • "and that modern processes for wheel and tire production ensure being well within that tolerance." nonsense, balance the wheel tire assembly. 1 ounce of imbalace creates 10 lbs of throw on a 15" wheel, becomes greater with larger diameters.
    – Moab
    Jun 17, 2020 at 17:35
  • @SolarMike What is a tolerable wheel imbalance?
    – DarioP
    Jun 17, 2020 at 19:02
  • 1
    @DarioP not true.
    – Moab
    Jun 18, 2020 at 0:05

1 Answer 1

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It is quite rare for a manufacturer to report a maximum imbalance, but in a copy of the Kawasaki H2 service manual (which I managed to find online here) I was happy to find a maximum tolerance of 10 grams. Note that 10 g is also the minimum balancing weight officially provided by Kawasaki.

The dynamic force produced by an imbalanced wheel can be approximated [1] as:

F = m v² / r

where r is the wheel radius, m is the unbalanced mass and v is the speed of the vehicle.

Now, the H2 comes with standard 17" wheels and it is easily capable of breaking 300 km/h. Plugging these numbers into the formula above, together with the 10 g imbalance we get a force of ~320 N. At a speed of 130 km/h, the same force is obtained for an imbalance of ~53 g. Note there is likely some safety factor into this number.

From this analysis one can conclude that a 50 grams imbalance is within the manufacturer limits for legal road speeds and therefore can be considered safe (at least for the Kawasaki H2, but it is probably ok for many other decently built models given the safety factors). However one should be more careful with the balancing if planning to ride on the track or on the German autobahn. According to Kawasaki, the ultimate tolerable unbalance for speeds above 300 km/h is 10 grams.


[1] This formula does not take into account the different radii of the tire contact point and of the position of the imbalance weight.

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