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Downsizing winter tires on a 2000 Toyota Camry

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  • A 10mm difference from 205mm to 195mm equates to 0.39 inch change. Between a quarter and half inch less width. Nothing to be concerned about going to a slightly less wide tire.
    – F Dryer
    Commented Sep 30, 2022 at 22:04

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Here is a really useful tool for answering questions such as this one:

Tire Size Calculator

The results from your sizes are:

Comparison

As you can see, there is very little difference between these two sizes. So it's very likely that you can use these smaller tires without any issues.

I would not, however, mix these two sizes on the car at the same time.

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There are several considerations here:

  • Do the tires fit? As they have the same rim diameter but are smaller in width (195mm vs 205mm) and in height (195mm * 0.65 vs 205mm * 0.65), they fit almost certainly, although in theory using less wide tires would ideally mean switching to less wide rims, but if 205mm tires are optimal for your rims, then definitely you can go to 195mm. If on the other hand 205mm is the absolute thinnest tire size your rims can support, then 195mm won't fit.
  • What is the speedometer reading difference?

Let's check about the speedometer. By installing smaller tires, your tires rotate faster for a given vehicle speed. The speedometer then shows a faster speed. This is not a problem. Going in the other direction might be a problem but usually there's designed-in error that allows slight tire size changes. If your real speed is 100 km/h, but your speedometer reads 101 km/h, that's ok but if your speedometer read 99 km/h that would not since your real speed would be above the speedometer reading.

Specifically, the 195mm tires have 195*0.65*2+15*25.4 = 634.5 mm size.

The 205mm tires have 205*0.65*2+15*25.4 = 647.5 mm size.

This means speedometer reading increases by a factor of 647.5/634.5 = 1.0205 or by 2.05%.

Usually speedometers have 5-10% error designed-in. If you had 5% error before, it would be 7.05% error now. If you had 10% error before, it would be 12.05% error now.

I think there may be some regulation for how big the difference in speedometer reading and true speed can be if the speedometer shows more. Obviously you wouldn't want to be driving at 20 km/h, while speedometer shows 100 km/h. But I don't really believe these laws would kick in for your use case.

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