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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
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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
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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
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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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Are you planning on taking your car to a race track?

If we are talking about tires and handling, the order of importance is generally as follows:

  • Tire compound
  • Tire width
  • Tire construction (e.g. sidewall stiffness)
  • Wheel width

This is why race cars (real ones you see on TV) use tires that are worn out after 40 minutes of driving. They have extremely soft compounds compared to street tires. This is why tire compounds are almost always prescribed in the rules. This is why there are tire width limits in the rules and there are more rule sets with tire width limits than there are with wheel width limits.

Wheel width is #4 on the list. It makes sense to talk about optimizing wheel width after the first three items having to do with tires have been accounted for. I track Miatas and for best performance use 225 width tires on 9" wheels. But, the tires are the most important component by far. A race 225 width tire on a 6" wheel will perform better than a street 225 width tire on 7" or 8" or 9" wheel, or a street 245 width tire for that matter (if the car has enough horsepower).

(On a side note, the current generally accepted wisdom in the performance driving community is that for best performance the wheel should be slightly wider than the tread width (not section width) of the tire, with the sidewall of the tire ideally perpendicular to road surface. If you look at the various race cars across the disciplines you'll see many examples of this. But street cars generally have tires wider than wheels, and more section width than tread width, so that the wheels are not damaged against curbs and tires don't hit fender liners when cars are loaded with groceries to the max.)

For street driving in a family car, I doubt you'll be able to tell the difference between 1" of wheel width either way. Possibly even 2".

Street cars are used in a wide variety of conditions. Consider:

  • Driving in spring/fall with snow tires on (very soft sidewalls).
  • Driving on worn out tires in wet conditions.

In both of these circumstances, what wheel you have the tires mounted on absolutely does not matter.

Another consideration that matters a lot in street driving and not so much in track driving is rated load carrying capacity.

  • Wider tires support more load
  • Taller sidewalls support more load
  • Taller sidewalls make the vehicle less responsive

If you are considering getting narrower than OEM tires in particular, make sure they are rated to support the rated maximum gross weight of your vehicle. One issue with large diameter aftermarket wheels is the tires that fit them and the vehicle aren't rated to support the OEM max gross weight.

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