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Discussion Starter #1
Thinking of if the traction and cornering will be improved by changing to winter tires for normal dry road In summer? Do the winter tires help?

My preference will be CONTINENTAL WINTER CONTACT TS800
 

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On the standard 4.5Jx15 ET23.5 front rims and 5.5Jx15 ET22 rear rims you can run the same size tires all round if you want. Vredestein Quatrac 5 are good in snow if it's not too deep.

Tire sizes that will fit both the 4.5J and 5.5J rims include:

175/55R15
185/60R15

Vredestein Quatrac 5 175/55R15 77T

Vredestein Quatrac 5 185/60R15 88H

However, my preference would be for 165/60R15 front tires and 185/55R15 rear tires. Matching Vredestein Quatrac 5 tires are available in both those sizes.
 

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There is a cautionary tale on here of the tire place that put a front rim on the rear and a rear rim on the front, with interesting results. I don’t recall if he had the same size tires front and rear, but the car definitely had issues.

I looked at a Cadillac CTS AWD Coupe earlier this year where the same thing had been done. Fronts on rear and rears on front. Previous owner ended up replacing all the axle bearings. Not sure if that was the cause, but I wasn’t going to pay good money to find out what else might have been affected.

If you get directional tires, watch them when they are mounted. I’ve had at least 4 instances where they were mounted backwards.
 

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Discussion Starter #16
I still get a bit of confusion. The OEM tires are 175/55 R15 and 155/60 R15.

but 175/55 R15 and 185/60R15 will fit? The tires will be hanging out from the wheels?

Bare with me because I’m not very familiar with the tire numbers lol
 

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On the front 4.5J rims, the sidewalls of 175/55R15 and 185/60R15 tires will bulge out a bit but not too much. This helps to provide a comfortable ride and helps to protect the rims from kerbing damage when parallel parking at low speed.

The lower profile 185/50R15 tire is officially approved for a 5J rim. 175/55R15 and 185/60R15 tires will fit a 4.5J rim as comfortably as a 185/50R15 tire fits a 5J rim.

175/55R15 and 185/60R15 is the limit for a 4.5J rim as far as 175s and 185s go, so don't try fitting lower profile 175/50R15 and 185/55R15 tires to a 4.5J rim. Those tire sizes need at least a 5J rim.

When fitted with 15" tires, the Smart Roadster uses the same tire sizes front and rear, in conjunction with 1" narrower front rims. On a rear engined car with a light front end, the front tires' sidewalls don't need to be as rigid as the rear tires' sidewalls.

One of the tire sizes that the Roadster uses is 185/55R15. These are fitted to 5J front rims and 6J rear rims. However, 175/55R15 and 185/60R15 tires can be fitted to 0.5" narrower rims, ie. 4.5J front rims and 5.5J rear rims. The reason being that 175/55R15 is narrower than 185/55R15, and 185/60R15 is higher profile than 185/55R15.
 

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Discussion Starter #18
On the front 4.5J rims, the sidewalls of 175/55R15 and 185/60R15 tires will bulge out a bit but not too much. This helps to provide a comfortable ride and helps to protect the rims from kerbing damage when parallel parking at low speed.

The lower profile 185/50R15 tire is officially approved for a 5J rim. 175/55R15 and 185/60R15 tires will fit a 4.5J rim as comfortably as a 185/50R15 tire fits a 5J rim.

175/55R15 and 185/60R15 is the limit for a 4.5J rim as far as 175s and 185s go, so don't try fitting lower profile 175/50R15 and 185/55R15 tires to a 4.5J rim. Those tire sizes need at least a 5J rim.

When fitted with 15" tires, the Smart Roadster uses the same tire sizes front and rear, in conjunction with 1" narrower front rims. On a rear engined car with a light front end, the front tires' sidewalls don't need to be as rigid as the rear tires' sidewalls.

One of the tire sizes that the Roadster uses is 185/55R15. These are fitted to 5J front rims and 6J rear rims. However, 175/55R15 and 185/60R15 tires can be fitted to 0.5" narrower rims, ie. 4.5J front rims and 5.5J rear rims. The reason being that 175/55R15 is narrower than 185/55R15, and 185/60R15 is higher profile than 185/55R15.
Great and thank you for your detailed explanation
 

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Discussion Starter #19
There is a cautionary tale on here of the tire place that put a front rim on the rear and a rear rim on the front, with interesting results. I don’t recall if he had the same size tires front and rear, but the car definitely had issues.

I looked at a Cadillac CTS AWD Coupe earlier this year where the same thing had been done. Fronts on rear and rears on front. Previous owner ended up replacing all the axle bearings. Not sure if that was the cause, but I wasn’t going to pay good money to find out what else might have been affected.

If you get directional tires, watch them when they are mounted. I’ve had at least 4 instances where they were mounted backwards.
I won’t do that either lol and thanks for the tips
 
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