I am looking for some "formal" information about which tyres I can put on my car rims. More generally speaking, I'd like to be able to find an optimal match between a tyre and rim width.

The question is triggered by the situation I found myself in now. My Volvo V70 came with 225/50-R17 tyres on 7Jx17-ET50 rims. Looking at www.tyresizecalculator.com, this is not an optimal combination, rather on the edge. It gives 195 mm as minimum, 205/215 as ideal and 225 as max allowed. Would Volvo build a poor combination wheel? A Volvo dealer, to whom I showed the linked table and whose competence I really doubt, said that 205 mm would be too narrow for these rims, not to mention 195 mm. On the other hand, another table I've found (in Russian) lists 7 inch as the optimal rim width for my tyres. So that Russian table (from an online tyre shop) seems to agree with the dealer and Volvo, but doesn't match TyreSizeCalculator.

I wonder where all this information is coming from, why a mismatch, and where I can find the "holly truth". Isn't there some sort of standard for this?

  • Do you have standard rim under the car? – Iman Dec 9 '16 at 23:07
  • @Zich, it is a Volvo original wheel and it is a rim that Volvo offers for these cars. Why? – texnic Dec 9 '16 at 23:26

A good rule of thumb is that your wheel needs to be a bit narrower that your tires, so that it squeezes the tire's bead area against the wheel's outer lip.

Your 7 inch wide wheels, in metric, come out to just under 178 mm. Therefore, any tire that has a width of more than 178 mm at the bead (the width stated in the tire size is at the tread) would fit nicely.

I've found this table to answer another user's question about tire width and rim width:

tire to rim fitment

  • I've seen this table too, I think it more or less replicates the one I linked in the post. At least they match for my situation. However, this is yet another table derived by some nice guy from some unknown information sources, rather than a standard (as in ISO or ANSI) chart. So while your rule of thumb makes sense, I wonder where to find the official data or, alternatively, why it doesn't exist. At least I would expect the tyre manufactures to care about it, but I couldn't find anything on Dunlop or Michelin sites. – texnic Dec 9 '16 at 23:21
  • As you mention yourself, the rim should be narrower than the tyre at the bead, while the tyre width is specified at the tread. So the application of the rule of thumb is not very straightforward. – texnic Dec 9 '16 at 23:23

Ok, let's look at this another way. My other answer was the "theorical answer", based on charts. When that doesn't provide a satisfactory answer, we need to look for an "empirical answer", based at what cars roll out of the factory with.

On the one hand, these vehicles all have your 225 mm wide tire on a 17x7 wheel:

On the other hand, all the following vehicles have 225 mm tires on a 7.5 inch wheel, and their 7 inch wheels only have 215 mm tires on them:

You'll notice that Toyota (through their Lexus brand), Subaru and Volvo are in both lists, so it isn't a hard and fast rule. It may have to do with "looks," as a tire on the wide-end of the range will be pinched more and the sidewall will be seen to "bulge out" of the wheel, whereas a tire on the narrow-end of the range will be pinched less, so it's sidewall will be seen to be more straight.

If all you're worried about is safety, stick with what your car came with. Volvo thought it was ok, as do plenty of other reputable manufacturers.

  • This is what I call a "nice guy" attempt :) While I appreciate this input, I was hoping for something more "official". I would assume that the tyre/rim combination is a safety factor, and therefore the authorities should test/approve them. So far couldn't find anything. Where do all these compatibility charts stem from? They are not based on statistics of what car makers do, are they? – texnic Dec 12 '16 at 15:05

Tyre manufactures list the range of acceptable wheel rim widths for each tyre type and size. On the narrowest allowable rim width the tyre will be more comfortable; on the widest allowable rim width the tyre will handle better. They usually specify a rim width in the middle of the range an an ideal compromise and this is what most manufactures on most models choose.

I hope that helps.

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