WHICH TYRES?

by Tony Marshall (published in the Isetta Gazette February 1980)

A member wrote in to say that he had several extra wheels which came with his Isetta, some of which are wider than the others, and how can he decide which of them he should be using.

The correct tyre size for the most numerous type of Isetta in the club (the Brighton built three wheeler) is the 4.80 x 10 on the two front wheels, and a 5.20 x 10 on the rear. The reason is that the rear wheel is a different width, as well as being a different 'dish' shape, a legacy of the conversion of the original four wheeler to three wheels to take advantage of the British taxation laws.

The rear wheel can be mounted on the front hubs, but a front wheel will not fit the rear. This brings us to the spare wheel, which sometimes poses something of a problem, but of course, the 5.20 x 10 is the wrong size for use at the front. The answer, therefore, is to use a 4.80 x 10 fitted to a rear wheel. Incidentally, if you are tempted to use 5.20 x 10 tyres all round, it would appear that when the steering is turned to full lock, the tyre then rubs on the inside of the wing.

The four wheeler Isetta is a little easier, having the same tyres (4.80 x 10) all round. However, some of the earlier German Isetta's were sold with wheels and tyres of 4.40 x 10 size, and this size is often quoted in manuals and other literature.

One other variation of Isetta wheel sometimes encountered is the 'split rim' wheel, which has to be dismantled in order to remove the tyre. This is another German type, quite common on the continent, as well as being found in America, and on some of the Romi Isetta's in Brazil. This wheel is probably a feature of the original Iso Isetta which lingered longer than some of the other features.

The BMW 600 is much easier in respect of tyres, at least in England, as it uses 5.20 x 10 tyres on all wheels.

Before you all start contacting me and telling me that you can use 5.20 x 10 tyres on the front of an Isetta, I can tell you that I have personal experience of the problem of the tyre fouling the bodywork on one car, whilst apparently being able to use them on another, apparently similar car. Why there is a discrepancy I do not know.