Wire wheels need a specialist tool that disc and alloy wheels do not, a balancing cone that fits over the splined centre of the wheel and provides the central reference the balancing machine needs to spin the wheel true. A conventional disc or alloy wheel has a smooth machined centre bore that the balancing machine's cone seats into, centring the wheel precisely on the spindle, but a wire wheel has no such bore, its centre being occupied by the splined hub that mates with the spinner in normal use, so without a specific tool the tyre-fitter has nothing to locate the wheel against. The result of balancing a wire wheel without the correct cones is a wheel that sits off-axis on the machine, giving a balance reading that does not correspond to how the wheel actually runs, and the symptoms are steering-wheel shake at road speed and uneven tyre wear over time, frequently misdiagnosed as a steering or suspension fault and leading to unnecessary parts replacement when the real solution is a correct rebalance.
How the Cones Work
The balancing cones replicate the splined hub's centring function against the wheel's centre-lock bore, a pair of cones locating the wheel concentrically on the balancer's spindle so that its rotational axis during balancing exactly matches the axis it rotates about in service. The kits are manufactured from high-tensile plastic, a deliberate choice for this application, as metal cones would mark the centre-lock bore of a wire wheel, particularly on chrome-plated items where any scratch is visible, while the high-tensile plastic locates the wheel accurately without risk of marking and still provides the rigidity needed without flexing at operating speeds, tested to withstand a high axial clamping load. A typical kit comprises a male cone, a female cone, a clamping washer, and a pair of slip bushes sized to fit the majority of tyre balancing machines in current use, the male cone locating on the spindle against the machine face, the wheel centred against it, the female cone engaging the outboard side, and the clamping washer fitted before the assembly is clamped, the washer always being used to avoid damage to the female cone.
Sizes & Application
Balancing cones are stocked in the sizes used across the classic-MG and wider British classic range, the size referring to the centre-lock bore diameter. The 42mm kit is the correct size for all MG applications, MGA, MGB, MGC, Midget, and the T-types, and also suits Austin-Healey, Morgan, Triumph, and other British sports cars of the period using the same centre-lock architecture, while a larger 52mm kit is supplied for Jaguar, Rover, Alvis, and other fitments with the larger bore. The same cone works for any wire wheel of the appropriate hub diameter regardless of wheel type or thread pattern, so a workshop fitting wires across a range of British classics typically needs only two or three cone sizes to cover the entire range, and where a tyre fitter's spindle size differs, tailored slip bushes can be made to order.
Using the Cones
The cones are a workshop item used by the tyre-fitter rather than a roadside service item, living on the balancing machine alongside the rest of its accessories, and they are required whenever a wire-wheeled car needs tyre balancing, which is whenever a new tyre is fitted, an existing tyre is removed and refitted, or balance weights are lost in service. Not every modern tyre shop has the specialist wire-wheel equipment, and a fitter without the correct cones may attempt to balance the wheel using standard adaptor plates or by clamping the rim directly, neither of which provides accurate centring, so owners running wire wheels should confirm with their preferred tyre fitter that the right cones are available before booking the work. Many classic-MG owners keep a set to hand to supply to the tyre shop when needed, particularly for tours where tyre issues might be dealt with at an unfamiliar fitter, the cones being a modest investment that pays back many times over in the smoother running of a properly-balanced wire wheel.