Sportstick

Your tires are exactly where I would be replacing them for three season driving. If you intend to try to get through winter without dedicated winter tires, at least get those DWS now. But, I would do four, not just two. All that weight transfer forward under braking and steering needs the benefit of winter time traction! The rears mostly help you get going, a convenience, but those fronts can save you!

Here is what Tire Rack says, and yes, I know they sell tires for a living!

However, as a tire wears it's important to realize that the tire's ability to perform in rain and snow will be reduced. With 2/32" of remaining tread depth, resistance to hydroplaning in the rain at highway speeds has been significantly reduced, and traction in snow has been virtually eliminated.

If rain and wet roads are a concern, you should consider replacing your tires when they reach approximately 4/32" of remaining tread depth. Since water can't be compressed, you need enough tread depth to allow rain to escape through the tire's grooves. If the water can't escape fast enough, your vehicle's tires will be forced to hydroplane (float) on top of the water, losing traction.

If snow-covered roads are a concern, you should consider replacing your tires when they reach approximately 6/32" of remaining tread depth to maintain good mobility. You need more tread depth in snow because your tires need to compress the snow in their grooves and release it as they roll. If there isn't sufficient tread depth, the "bites" of snow your tires can take on each revolution will be reduced to "nibbles," and your vehicle's traction and mobility will be sacrificed. Because tread depth is such an important element for snow traction, winter tires usually start with noticeably deeper tread depths than typical All-Season or summer tires. Some winter tires even have a second series of "wear bars" molded in their tread pattern indicating approximately 6/32" remaining tread depth to warn you when your tires no longer meet the desired tread depth.

Pete7874

Well, I generally agree with their recommendations. But my fronts have 8/32" of tread left. Well above their 6/32" replacement recommendation. That's the only thing that's making me think twice before replacing the fronts. I'll definitely replace the rears.

kevink2

I agree with you. Wear pattern for rears looks very even. I still think they may have sold you on new-like used tires, with more wear on rears to start. Rears are definitely worn, esp if this was the original "mercedes" spec tire. Notice the finer surface tread groove pattern that has been worn through:

ContiProContact-MB Spec- 245-40-17

The 4matic has a base torque split rear bias at center diff of 45/55.

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The 'NEW' 2008-mercedes-benz-c-class

4MATIC Cars Get Rear-Biased Torque Distribution:

"Under normal conditions, Mercedes sport utility vehicles distribute torque nearly equally between the front and rear wheels. However, the 4MATIC-equipped C-Class and S-Class sedans come with a planetary gear set within the center differential that begins with 45-55 percent front-to-rear torque distribution."

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I think the best path forward is 2 new rear conti's, but 225-45-17, like front. (fits the 8.5" wide oem rim)

Then search ebay, dealers, etc, for a used set of your type front wheels. When purchased, put them on rear for the non-staggered lux model set-up, allowing proper rotation, and better ride and winter/rain performance in general.

Next tire set consider DWS, all 225-45-17.

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Sportstick

I feel more comfortable with the balance of similar traction at all four corners. But, if you only plan to buy two new DWS tires, I would toss the rears, move the fronts to the rear, and put the new DWS on the front. Braking and steering are more important to your welfare than accelerating.

Pete7874

Most tire manufacturers as well as TireRack think that better tires should be mounted on the rear. This is to prevent oversteer (your rear sliding out) which is much more difficult to control for an average driver.

Pete7874

Thanks for the correction. I don't know where I've read the 20/80 thing.

Sportstick

Yes, this is generally true, and a good reason for four equally capable tires. But, a non-aggressive driver will encounter the winter issues of a surprise braking and steering event more often than oversteer, which can predictably be prevented by the speed when entering a turn. Even for the low-to-moderate skilled driver who misjudges the proper speed for a situation, there is some chance for recovery if the tail move out a bit, (we all learned steering into a skid in driver's ed.?) but when the front starts to plow or skid, the control is essentially lost for all, and we just hope there is nothing solid in front of the car. However, we each assess risk differently, and I wish you well with your final choice.

kevink2

Are you sure the 8.5" x 17" rear rims would work up front, for his staggered set-up?

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Pete7874, remember this suggestion to avoid confusion:

*** All Members New and some Old, please click on User CP at the top left of page, just below the thread title. ***

Then add the following to either Profile and/or Signature , selecting buttons on the left side of that page: year, model, Sport or Lux, 4MATIC or RWD, and Location, city & state (and non-US/Canada country if needed). This helps response to issues, like tires, sales, etc.

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Sportstick

Good point about rims, which would need to be confirmed. I have 8" running on all four corners with no issues. I was thinking primarily about the tires, as the 1010tires.com calculator shows the front tires will fit the 8.5" rear rims.

kevink2

What offset? OEM Sport rears are 58mm ... most all the extra oem width vs fronts is inboard, so inside rub with suspension could be an issue.

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Sportstick

Here's the story...

https://mbworld.org/forums/c-class-w...g-17-reps.html

Pete7874

Thanks. I had it all in there except for the "Sport" part. Fixed now.

kevink2

Based on my calc's, ignoring the slight departure from oem tire width using your 8" rims vs oem 8.5" rears, the position of the inner side of the tire moves more inboard:

.27" using your rears up front.

.83" just moving sport rears up front.

When checking for front inside clearance at the tire, you need to consider the decreased "dynamic" clearance of the outside tire when hard cornering, as the sidewall experiences lateral shear displacement.

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Pete7874

A follow-up question: Will the TPMS have to be replaced when installing new tires? Another words, will I have to pay for new TPMS or do the existing ones get reused?