14 - Wheel balancing: general
- It is customary on all high performance machines to balance the wheels complete with tyre's and tube. The out of balance forces
which exist are eliminated and the handling of the machine is improved in consequence. A wheel which is badly out of balance produces through
the steering a most unpleasant hammering effect at high speeds.
- Some tyre's have a balance mark on the sidewall, usually in the form of a coloured spot. This mark must be in line with the
tyre valve. Refer to Section 11. Even then the wheel may require the addition of
balance weights, to offset the weight of the tyre valve itself.
- If the wheel is raised clear of the ground and is spun, it will probably come to rest with the tyre valve or the heaviest part
downward and will always come to rest in the same position. Balance weights must be added to a point diametrically opposite this heavy spot until
the wheel will come to rest in ANY position after it is spun.
- The wheels should be removed from the machine and mounted on a stand to eliminate brake or final drive drag. Weights are available
from BMW in 5, 10, 15, 20, 25 and 30 gram sizes; these are attached to the rim by a spring clip, using special pliers, on early 100 models.
On later 100 models and all 75 models a similar range of weights is available which are stuck to the rim with their adhesive backing; these can be
fitted to all models and carry no risk of disturbing the tyre/rim seal, although the rim must be absolutely dry, clean, and degreased at the point
of contact if the adhesive is to be effective. The weights are stuck to the rim flange, next to the spokes, as shown in the accompanying photographs.
Note: all models - the sum of the weights fitted to any rim must not exceed 60 grams (2 oz).
- Most tyre-fitting specialists have wheel-balancing equipment which can be used to balance the wheels in a very short time,
making the labour charge reasonable.