There seems to be an increasing trend for competitors to arrive at an event with incompatible tyre / wheel-rim combinations. Schedule A doesn’t cover this in any specific detail and perhaps it is sometimes difficult to determine if a car should be allowed to run in a certain configuration. The picture to the right is probably a ‘no-brainer’ and shouldn’t be accepted. Some other examples might not be so clear cut though so how would you determine if a tyre / wheel combination was acceptable ?
Tyre manufacturers design tyres to be used within a small range of rim sizes. As a general rule the sidewall of the tyre should be close to a 90 degree tangent to the rim bead for safe operation and optimum performance. There is a good table available on the LVVTA website showing recommended tyre to rim size data and if you suspect this may be a problem at an event you are officiating at it might be worthwhile printing a copy out for your reference. There are a number of other websites also that provide this advisory data. You could consider most of this to be industry best practise and a useful guideline when checking at an event.
Sometimes, if it just doesn't look right, then perhaps it’s not.