The symptom drivers notice first
A new tyre can feel perfect below 50 mph and become a steering-wheel tremor at 65 mph. That pattern usually points to dynamic imbalance, not a badly seated tyre. A spinboss check isolates the heaviest point across the wheel’s width and both planes, which is why it catches faults a static bubble balance can miss. The takeaway: speed-specific vibration deserves a dynamic test, not a guess.
Why static balancing misses the cause
Static balancing treats the wheel as a flat disc and adds one counterweight opposite the heavy spot. It cannot correct a couple — two opposing heavy points on opposite rim edges. Cause: tyre construction, wheel weights, TPMS sensors and run-flat sidewalls distribute mass unevenly. Solution: spinboss-style dynamic balancing spins the assembly and calculates weight placement on both inner and outer flanges. Without that two-plane correction, the wheel can be “balanced” on the machine and still shimmy on the road.
What a calibrated spinboss run measures
During a proper run, the operator mounts the wheel with the correct cone and adaptor, checks rim runout, and lets the machine record radial force variation as well as imbalance. A useful spinboss result is not just a number; it is a placement map for adhesive weights. If the rim is bent or the tyre has a stiff spot, rebalancing alone masks the fault. The takeaway: ask for runout to be checked before weights are added.
The mobile-service constraint
Mobile tyre fitting has a calibration problem: a balancer that travels in a van is exposed to vibration, temperature swings and improvised power. A spinboss machine is only as good as its last calibration and the fitter’s mounting technique. Example: a wheel tightened onto a dirty hub face can introduce lateral runout that mimics imbalance. Solution: clean the hub, torque in a star pattern, and road-test at the speed where the vibration appeared.
When to book a dynamic balance
- After fitting new tyres, especially low-profile or run-flat sizes.
- When a steering wheel shakes at a narrow speed band.
- After hitting a pothole or kerb, even if the tyre holds pressure.
- When old weights have been removed and not replaced on both flanges.
A repeatable spinboss balance should reduce the vibration, not merely move it to another speed. If the tremor remains, inspect the tyre for radial force variation and the wheel for bend. The result is a diagnosis, not a cosmetic weight strip.
