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Discussion Starter #1
I am looking at putting together a winter set for my Canadian 2019 Limited. The stock wheels are 18x7.
I am looking at the Touren TR60 wheels with Blizzak WS90 tires. The TR60s are available as 17x7.5 or 18x8. Which wheel size would provide best performance from a safety perspective. I live in Southern Ontario, and this being a family vehicle, safety is a top priority. It will be doing a combination of city and highway driving.
From a safety perspective is there anything I should be considering between the two different wheel sizes? I see some people going down 0.5-1” on wheel size for winter sets but am unsure of the rationale. Given that it’s on Stock 18” wheels, I would think consistency in size would allow for easier transition when switching from all-seasons to winters. In my reading, it seems that increased width will increase contact area between tire and road which can either:
a.) increase tread contact and improve stability, or
b.) increase distribution of weight, reducing pressure of contact areas decreasing stability.
Is there not much difference between the two? Anything else I should be considering? Thanks for your help!
 

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2001 Forester
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The object with winter tires is to decrease tire width(go from 215 to 205) and therefore increase tire profile(60 to 65/70), with a corresponding decrease in wheel diameter(16" to 15"). Your object is not to increase tread contact patch as that only causes the tire to "float" on the surface versus digging/cutting into the snow for traction.
 

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Narrower tire width in snow on passenger cars is not as important as it's made out to be. It comes from seeing rally cars using very narrow tread to cut into the snow. That's great for rallying in snow.

Passenger cars spend more time on packed snow, ice or even more on pavement. So, there is little reason to go narrower than stock. Tread compound is more important than a narrow tire in winter.

Wheel size matters a lot more in the winter. I like more sidewall to absorb the inevitable potholes that open up. So, I prefer the smallest wheel that fits over the brakes and thus more tire sidewall. Keep the overall tire circumference and width the same, but go with the 17s.
 

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Discussion Starter #4
Thanks a lot for your replies, very helpful.

So I can put Bridgestone Blizzak WS90 225/55R17 on Touren TR60s 17x17.5?
 

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2019 Forester Limited CVT
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Thanks a lot for your replies, very helpful.

So I can put Bridgestone Blizzak WS90 225/55R17 on Touren TR60s 17x17.5?
The general rule is increase of 5 aspect ratio for each inch decrease of wheel size. Stock is 225/55 18, so you'd want 225/60 17. You could also use 215/65 17.
10mm difference in width might make a difference on a rally stage, but not in everyday driving. At least that was the case on my 2005 LGT wagon.
As others have stated a taller sidewall reduces the chance of damaging a tire on a pothole. They're also less expensive.
 
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