Metric size tyres
The quite confusing and puzzling tyre sizes that some vehicles are fitted with are called metric sizes a good example of a metric size is:
This size is one off the sizes found as original fitment on some of the old BMW 525.
The cross section of this tyre measures 230mm, the sidewall height is 55, the speed rating is ZR and the rim size as in the diameter of the wheel is 390mm.
Metric wheels were limited to a few cars only namely a BMW, Ferrari, and a few others. All these cars had wheels that were essentially in metric (mm) i.e. a 390mm, 360 mm etc. The difference was the standard rims came in exact inches i.e. 14 ", 15" and 16". Metric sizes also had different or odd width dimensions i.e.| 220, 230, 240 etc. Normal sizes the section width usually were 225, 235, 245 sizes go up 10mm and start and would never be 230, or 220. The tread designs were all similar or largely the same and very few manufacturers actually made these metric sizes most popular were Dunlop and Michelin. Metric wheels and tyres were never going to feature on every car as they never did become popular. The tyres themselves were quite stiff and were intended to withstand punctures and run as a run flat, that in itself is a very long debate with many different opposing views.
Metric tyres are quite hard to find the only company still making them are Dunlop and even their stock is often limited. Metric sizes no longer feature on new cars and it just as good as the price of an on off size was very expensive. Today drivers that have metric size wheels are stuck and often find it hard to get stock and if they do manage to find some they are paying over the odds for them. The only alternative is to change the rims to standard size rims.
A lot of people have followed manufacturers advice and changed from something like 230/55/390 to 225/55/16. If you're looking for Metric size tyres, please give our call centre a call on 0845 094 09 09.