mellonc

for my winter set up (finally doing some road trips out of the warm Los Angeles area) I thought I could go with 225's instead of the 245's, which is stock. It will 50 profile instead of the 45 profile.

I thought the stock wheel width is 8 inches and should be fine for the 225's. And the speedometer error should be within 1% (the stock set up overstates the speed anyway....)

conventional wisdom is to go just a bit narrower on width and higher on profile for the all-season or winter set up. but I just wanted to throw it out there to see what you all are running for the winter.......

cocobeex

Love low profile in the snow...

SO MUCH FUNNNNN!!!!!

mikemargolis

I am running 225/45R17 run flat snows (Blizzak LM-25) while the non snows are 235/45R17

According to Waze, the speedometer is within 1mph, and everything's great.

A little less width is not a problem in the winter.

(for me the run flat snows didn't come in a 235)

Diesel #2

225s in the rear is too narrow, you wont have the same traction since it is a RWD.

A word of advice, if you want a higher profile tire you dont necessarily have to go narrower. I would recommend going with 255/45. This way you are a tad bit wider than stock and you will have even MORE tread than a 225/50 tires.

225/50 tires = 4.4" of rubber

255/45 tires = 4.5" of rubber

KEY08

He's talking a winter setup, correct? Better traction with a skinnier tire on snow than a wider tire. More weight per square inch bearing down.

mellonc

yes. Winter set up. (Though in southern CA, we r dealing mostly with rain with occasional trips to snow bound regions). I'd probably stick with 225's.

VegasE

Also, the wider the tire, the more likely it will "ski" over soft snow.

mellonc

I stand corrected on my stock wheel width. as it turns out it may be 8.5 inches wide. I could have sworn it was 8 inches but I really can't tell for sure. I looked at the wheel but it doesn't say on the wheel itself. the manual says both 8 inches and 8.5 inches.

It's a bit of an issue because I don't want to put on 225's on 8.5 inch wide wheels. Anyone know for sure?

I think the part number is: 2124015902

mikemargolis

A simple google search shows that part number is a 17" x 8.5" rim

iridium7777

i'm running 235/45/R17 blizzaks on 17x8 rims without any issues. this is even the alternate size offered by tirerack. clears the sport brakes without any issues.

normal "summer" is the 18x8.5 sport wheel.

looney100

The "weight per square inch bearing down" is determine by the vehicle's weight and tire pressures. Not by the width of the tire.

KEY08

Smaller contact patch equals more weight per sq inch. Why do I even respond in this forum anymore? Thanks for your insight.

looney100

So strong, so wrong.
While you are correct that a smaller contact patch means greater weight per square inch, you incorrectly assume that a skinnier tire results in a smaller contact patch. It does not, unless you increase tire pressure.
At 35 psi, a skinnier tire will just have a thinner, but longer contact patch than a wider tire.
3500lb car, 35 psi tire pressure, means 100 square inches of contact patch, regardless of tire width. It's just math.

You are welcome for the insight.

looney100

While I'm sure it won't hurt anything, I cringe when I drive over deep snow and hear it scraping the underbody...

Gorgeous car, BTW.

KEY08

Skinnier tires have always been better in snow than wide fat tires because they cut through the top layer to get traction and don't ride on top of it. More pressure bearing down from a smaller footprint. Simple math. Would you rather use a steak knife on your steak or a butter knife? This whole tread is about a skinny tire vs wider tire in snow.

looney100

Thinner tires do not create more pressure. One might argue that with a wider "wave-front" a wider tire may ride higher on heavy snow than a thinner tire, therefore more of that pressure rests on the snow than on the hard surface below. This affect doesn't necessarily translate to better traction. Here, in the winters, the roads often have a hard-pack snow/ice covering the pavement through much of the winter. In that case, the tires are better to bite the snow than slip across the top of the ice pack.
Your knife analogy is not appropriate as a steak knife has a sharper blade - a much finer point than a butter knife. Less surface area means more pressure, which improves cutting ability. A serrated edge further reduces surface area and improves cutting by increase the pressure. Same weight on few square inches. Which is not what happens with tires.

mellonc

I don't know about the all these physics stuff but rally car people have to run skinnier tires than road race people - wider tires transmit every little bump and gravel. Snow traction is better too. I'm told they run about 185 to 205 for dirt, water and snow. See this vid. and see how thin the tires are.
Formula 1 teams also typically run rain tires that are tiny bit narrower than full dry tires (though this may be limited by restriction put on by F1). see this comment from Pireli about needing narrower tires in the wet condition. http://www.f1fanatic.co.uk/2017/01/1...weather-tyres/

KEY08

Yeah, I give up to the Canuck. **** it.

looney100

you've got no argument from me here. Thinner tires are better in the rain due to needing to push a smaller "wave front" as I said earlier.

There could also be specifics related to the setup of the rally cars, need for much greater lateral bite and surface conditions that might make thinner tires favourable.

If if you go back to my initial points. They were that a thinner tire does not decrease the contact patch, nor increase the pressure on the road. These two points are simple math.

On the broader question of are thinner tires better in the snow - they could be under certain circumstances - particularly at higher speeds and if Snow cover is light and getting tire contact with good Pavement is possible.