How do you choose spigot rings?

So, if a wheel’s centre bore does not match the size of the hub’s spigot, the problem can be solved by fitting special spigot rings, which are sold at tyre centres. The only question left is how to choose spigot rings, and which ones are best? First of all, a wheel whose centre bore diameter does not match the standard one can only be fitted to the car if that centre bore is bigger than the standard one. If it is smaller, you will have to give up on that wheel: no amount of boring it out is acceptable here, since boring it out inevitably overheats the wheel, which changes the physical properties of the material it is made from (more on why you must not repair wheels that way).

To choose the right spigot rings you will only need two figures: the centre bore diameter of the wheel you would like to fit (DIA), and the bore diameter of the standard wheel. The first figure is stamped on the wheel itself (more on wheel markings); for the second, you can either look at the standard (original) wheel from your car (for example, if you still have the original spare wheel), or check the car’s documentation. Here, the first diameter will correspond to the outer (fitting) diameter of the spigot ring, and the second to the inner one.

It should be noted that no deviation at all is possible here: you need an absolutely exact match, or the whole point of fitting a spigot ring is completely lost.

Plastic or aluminium?

If we recall that the sole purpose of a spigot ring is to ensure the wheel is fitted precisely onto the hub, and that, once the car is in use, there is no load on the spigot ring itself (thanks, again, to those same tapered seats on the wheel bolts or nuts), the material the spigot ring is made from does not matter much the first time the wheel is fitted. It is worth understanding, though, that repeatedly removing and refitting the wheel does put some load on the ring by itself, so if it is made of plastic there is a fairly high risk of it warping and, as a result, losing its main working property: dimensional accuracy.

At the same time, the plastic spigot rings sold at tyre centres are, firstly, fairly cheap (compared with aluminium ones), and are also usually made from a fairly hard plastic. So they should last through several removals and refittings, and besides, their low price lets you buy and carry several spares in the boot “just in case”. So, if plastic rings made under factory conditions by a trusted manufacturer exist and are sold for your figures (standard and actual centre bore diameters), there is no point at all in looking for, or paying extra for, rings made from any other material.

Things get considerably more complicated when no rings of exactly the right size are available (which happens fairly often). In that case you will have to order rings made to the sizes you need, for which you simply need to find a good, working lathe with tight tolerances. The material the rings are made from is not so critical here; it can be aluminium or any other alloy. What matters is that this material be softer than the ones the wheel and the hub are made from, so that if the wheel is fitted incorrectly (for example, if the bolts are tightened with an impact wrench), it is the ring that suffers, not the wheel or the hub. It is also worth understanding that metal rings, although far stronger than plastic ones, cannot be considered eternal either. So you will still need to keep a few spare spigot rings in the boot, and every time you fit a wheel to the car you need to check how it seats on the hub: there should be no play at all in the vertical plane.