The symptom: vibration that appears after a new tyre

A driver fits a new front tyre at the kerbside and, within a day, feels a shimmy through the wheel at 55–70 mph. The tyre holds pressure and the tread looks true, so the instinct is to blame the tyre brand. In most cases the problem is not the rubber; it is the wheel-and-tyre assembly’s balance state. A spinboss run is the practical check: it spins the assembly and measures where mass is missing or misplaced, then maps the correction weights.

Why imbalance survives a visual inspection

Static checks catch obvious bulges and loose beads; they cannot detect a 10-gram imbalance on the inner shoulder. At speed, that small offset becomes a centrifugal force that feeds back through the suspension. Mobile fitters often see this after a tyre is swapped without rebalancing the full assembly, or when old weights are left on and new weights are added. spinboss is the term used in this mobile-tyre context for the spin-balancing step that catches the error before the vehicle leaves the driveway.

Cause: the bead seat and the balance plane

Two causes dominate. First, the bead may not be fully seated; the tyre looks mounted but sits a few millimetres off, creating runout. Second, balance weights may be applied to the wrong plane—single-plane static balancing on a wide wheel leaves a dynamic couple that appears only at road speed. A spinboss check addresses both by spinning the assembly under load and reading both planes. The takeaway: ask for dynamic balancing, not just a bubble-balance check.

Solution: a mobile spinboss protocol

For a mobile call-out, the sequence is concrete: clean the hub face, seat and torque the wheel correctly, spin the assembly on the balancer, and fit weights on the inner and outer planes as indicated. If vibration persists, check road-force variation and wheel runout. A repeat spinboss pass after 20–30 miles confirms the weights have not moved. Drivers who skip this step often return with the same complaint and a second journey.

A second practical point is record-keeping. The job sheet should show the correction mass and the balance plane, because a vibration that returns at the same speed is easier to diagnose when the previous spinboss result is visible. That record also separates a balance issue from a tyre defect or a bent wheel before parts are replaced unnecessarily.

What to specify when booking

• Ask whether the mobile fit includes dynamic balancing or only tyre replacement.
• Request that old weights be removed before the spinboss run; stacked weights mask the true correction.
• Have the fitter record the gram amount and plane on the job sheet, so a repeat visit has a baseline.

Vibration after a mobile tyre fit is usually a balance problem, not a mystery. A spinboss check turns a vague complaint into a measured correction, and it is the difference between a tyre that merely holds air and one that runs smoothly at motorway speed.