JimPap

I want to post this to see if anyone can figure out what has happened.

I purchased my 2008 C300 on September 29th, 2007 which was built in Germany. It came with Michilen Sport HX MXM4 stagger 17" tires.

The car always felt like it drove too firm. I had to play with the tire pressure so it didn't jar my fillings loose. Currently I run 28/32 front/back.

At 55,000 miles, I replaced my rear tires. The front ones look like they can still go for at least another 10K miles. Plenty of tread.

Now the weird part. The new rear tires which are the exact same model and size Michelins ride much better than the originals.

I'm fully aware that tires ride harder as the tread wears down but this car road hard from day one. They're also quieter.

I suspect that the rubber formula or something in the design is different between the two but I frankly don't know. In any event, I really like the way the car rides and steers with the new tires.

Do we have any tire gurus that might be able to explain why tires that are suppose to be the same are so different?

Sportstick

Yes.

They are not the same, despite the same model branding. Vehicle manufacturers specify a harder rubber compound to achieve a lower rolling resistance, which equates to higher EPA MPG ratings in their attempt to achieve the highest CAFE rating (Corporate Average Fuel Economy). OE formulations are typically not what tire manufacturers sell through the aftermarket, where they reduce the performance compromises to improve their product's performance. OEs will make significant compromises to improve CAFE by tenths of a mile per gallon. Had you put the same wheels on the front, you likely would have noticed a handling improvement as well.

JimPap

Sportstick,

Thanks for the reply.

Now that you mention it, I recall that I've heard that before and discounted it as not very likely. Seeing is believing.

Looking forward to seeing how much my mpg has suffered. The harder rubber compound explains why I was getting 32.5 mpg on straight highway driving. Hope it doesn't drop below 30. That's with the a/c off and the cruse control set at 70.

Carsy

Hello Jim,

The 55,000 miles on the rears is excellent mileage in my book.

I am looking at 35,000 kilometers only of conservative driving on my Bridgestone Turanza 205/55/16's.

The more I read about tyres the more the word compromise comes to mind. ie ride Vs handling ; grip Vs wear.

JimPap

Hi Carsy,

My thoughts too. (grip, noise, comfort,) vs (handling, wear).

I'm eyeing those front tires wondering if I were to replace them if the loss of handling would be worth the improvements in comfort. Tough choice given they still have so much tread.

Sportstick

It's the reverse. The replacement aftermarket tires of the supposed same OE model would handle and ride better due to the less hard compound. The sacrifice would be mpg and long term durability.

C300Sport

Could be the reason a lot of guys that move up to 18s from stock 17s say the ride is pretty much the same. The shorter sidewall is made up for by being more compliant even if they are going back with the same type of rubber.

Sportstick

A good theory....certainly, if one compared truly identical 17 vs 18, the loss of impact absorption in the shorter sidewall would be directionally negative for ride. The MB suspension may do a good enough job in not transmitting ride harshness, so the actual difference experienced may be insignificant-to-moderate at most. Then, the combination of moving from the stock harder 17" compound to a more compliant brand/model of an 18", just as you suggested, likely further reduces the noticeable difference. Of course, then, for those more concerned about ride, a great aftermarket 17" tire will still offer benefits.

JimPap

Good point. I never could buy off on the ride being the same with an inch less sidewall. Actually, I figured those who just spent a couple of grand upgrading to 18s didn't want to admit that the ride was worst.

It is fun to experience what the engineers must have intended for this car.

So those who got the OEM 18" AMG wheels with the special forumula tires probably have a fairly hard ride.

Carsy

Jim, Wear the fronts out . Its only 10,000 miles then enjoy the better ride of the new ones.It will make it easier to accept the higher wear rate !!!

ayilar

JimPap: Now that you have been running those new tires for a few months, how would you characterize silence/ride comfort/roadholding (especially in the wet)?