Mort

What offsets are the wheels? 245/35/19 front and up to 275/30/19 are possible depending on offsets.

zcct04

Tire Rack lists 2 options for 245/40ZR18 fronts. One is priced at $181.77 and the other is at $201.55. The second tire is described as MO Mercedes. Ratings all appear the same. Any clues about what's different, any insights about whether it's worth paying the extra $20/tire?

Standard: https://www.tirerack.com/tires/tires...SSXL&tab=Sizes

MO Mercedes: https://www.tirerack.com/tires/tires...XLV2&tab=Sizes

BLKROKT

Good question, I just asked the same thing fairly recently.

MO is for 2 things. The first is to show that these are the OE tire choice for the car, and that the tire is weight-rated and tuned specifically for the Mercedes that they came on (for instance the BS came in funky sizes and weight ratings that are impossible to match with anything outside of a MO tire). Both of these tires are 97Y, so there's something else going on. MO also stands for Mercedes quasi run-flat capabilities. It seems to be somewhere between a regular tire and a true run-flat in its abilities here, as they do not meet the true run-flat standard for distance etc. So from a practical perspective, I'd expect the MO tires to have a stiffer sidewall than a non-MO with all other things being equal.

More info here:
https://www.tirerack.com/tires/tiret...jsp?techid=234
http://www.rtecshop.com/shop/wheel-a...ted-tyres.html

Jasonoff

Tread width is wider on the non MO version (9" vs 8.6"). Since the section width is the same that suggests it may have a rounder shoulder for the Mercedes (MO) designed version.

Other than that, who knows. I don't think the design differences are ever made public knowledge. Even if both tires say they're a 97Y load rating, the MO version could actually be higher.

BLKROKT

No, actually it definitely is public knowledge. The differences are known - fit, run-flat, weight rating, etc. See the links above.

The rounder shoulder is so that they fit on Mercedes specifically - the second link explains explicitly how the tires are "tuned" to fit the Mercedes fenders etc.

Jasonoff

It's public knowledge if either manufacture makes the technical white paper available to the public. I haven't seen that done before, but, if you have, feel free to post the info from either Mercedes or Michelin.

Third party links, like what you provided are generally just speculation. Either by observation or possibly reverse engineering. Although potentially very accurate, it doesn't mean the technical details were made public knowledge.

Case in point, who TF is RTech Shop? That blurb could have been written by some co-op student.

BLKROKT

Fair enough. But do any manufacturers make technical whitepapers available on their proprietary and confidential tire technology and manufacturing methods? It's in their competitive best interests to not release much. So all we are left with is observation and reverse engineering in the end, no?

I think the Tire Rack link above is probably as accurate as it gets, as the manufacturers (both tire and car) probably give them as much information as anyone on how to differentiate one tire from another. That's outside of the racing tires which I assume are analyzed in extreme detail by racing teams and car manufacturers with the budgets to do so - although it's a question of how much of that is publically available.

This link is actually from MB, so might be a more reliable source but doesn't say much as you would expect. https://www.mbusa.com/mercedes/servi..._parts_article

And while this isn't exactly an "official" source, it's probably closer to what you're looking for. https://www.mbwholesaleparts.com/serviceItemTires.aspx

Jasonoff

Nope they don't which solidifies my comment. We, as the consumer have no idea what they changed other than what's physically obvious.

Yeah, that last link even suggests there could potentially be compound alterations. Maybe they use sriracha sauce as a mold release agent.

Erik Apple

Is 97Y an acceptable load rating for a C63 sedan?

todthedod

You'll be lucky to get 5k miles on those suckers but it sure will be a fun 5k miles.