RW15

Greetings all. Post number one for me on this forum. Just drove home today with a 2018 Certified GLS450.

Found a few examples online of people using 275/55/R20 tires on their GLSs, apparently without problems (though I don't know which model years). But the tolerances in the front wheel wells are pretty tight. Parked with the wheel at full turn I could barely squeeze a finger in between the outside edge of the tire (which are brand new 275/50/R20s) and the front wheel well molding. Doesn't seem like there is room for an an extra half inch there. I'd expect some minor rubbing with new 275/55/R20s. (Though I guess that extra tire diameter is at an angle to the wheel well at that point so you might not need a full extra half inch?)

Anyone using that larger tire size? I assume a heat gun with some minor massaging could open up the little extra space needed, if it does rub. But on day 1 with this beast, with years of warranty to go, it's a little intimating to think about modifying anything.

I live in very remote area and will take it on a lot of FS and BLM dirt roads in the mountains and southwest canyon country, and would like to mount all terrain tires, but I'm just not seeing those type of tires available in the stock sizes (275/50/R20, 275/55/R19.) I'm sure others have figured this out.

Thanks. Sorry if this has been discussed and rehashed many times, but I didn't see much information searching around for it (user error no doubt.) Looking forward to getting to know the vehicle and participating in these forums.
Rob White

mikapen

You may get better responses from the X166 forum (for your car - this is the forum for 2020 and newer M-B SUV's, the -167's).

I do have feedback, though, from our W164 and W166.
I have done extensive off-roading with the stock tire sizes. Tens of thousands of miles - most on the Colorado Plateau. This includes Canyon Country in Utah, NM and Colorado, with plenty of attempts to get stuck in Sand Dunes, Slick Rock and scree slopes.
IMO the only place an "off Road" tire is better than a good winter tire is in Mud or wet Caliche. Other than those, you are looking for Friction, which most off-road tires lack.
My tire of choice for extreme off-roading is the Nokian R2/3SUV. Right now we have mounted another set of Nokians - the WRG4 All Weather, which is more fun to drive than the full snows. Nokians use Aramid in their construction to guard against rock penetration - something that only a few "off-road" tires provide, and they come in stock sizes, too.

Air down and have a mini-compressor to get back to highway pressures when you're done. Skip the so-called Off Road tires. They just don't have the traction you are looking for.

RW15

Many thanks. Good to hear a first hand example. (And thanks for gently pointing out the user error. Didn't realize I had the wrong generation, or that the forum was by generation. MBs are new to me. Will try the x166.)

I'm probably over thinking it. I've been going into these areas in a low clearance Audi station wagon for a decade (and in a low clearance Toyota for a decade before that), sometimes in summer performance tires, and have never had a major problem. I've kind of enjoyed pulling up next to jeeps and toyota trucks in pretty remote areas in it. Though I hope to finally get into some areas that I couldn't/wouldn't with the Audi. I do plan to order a mini-compressor, some tire sealant cans, and a tire repair kit (any favorites or recommendations for those three?). Just paranoid without a full-size spare (which I'll probably buy at some point, to have along.) It came with new Pirelli Scorpion Verde A/S tires and a donut spare. I guessed/assumed A/T tires would be more durable and have more traction in relatively mellow off-road, and rough rocky road, type driving; but it wasn't through any direct experience. Makes sense though, what you said, which is similar with bicycle tires. Everyone seems to want aggressive tread but that is only better in muddy type conditions. Smoother tread is better for most dry riding, rough rock, etc. in addition to pavement.

But just so I understand, you used those winter tires (the Nokia R2s, now R3s) year round for warm weather off pavement desert/mountain driving with no issues? And they don't get quickly chewed up or have inherent weakness?

For winter I had Continental VikingContact tires on my Audi and considered using them year round, but I contacted Continental about it. And they said very specifically not to use their winter tires regularly above 40 degree F temperatures which spooked me.

Curiously, how low do you pressure down? Thanks again for the info.

mikapen

I used my "All Weather tires" year round, including lots of 90F+ traveling. I'm sure it shortened my tread life, but I still got @30,000 miles per set. I change out at 5/32nd because wet traction decreases at @4/32". That's the same mileage I get with regular All Season (I call them No Season) tires. The Nokian R2/3 get noisy under 4/32", but the WRG3 stay quieter longer.
It's nice, here in the Rockies, when it can go from 70F to 7F in one day (like tomorrow) and not have to slide through intersections on frozen pavement.

I air down to 25# and use my Viair compressor to air back up. It has enough "stuff" to air up several vehicles in our Party after a day around Ouray. 25# seemed adequate for most conditions with 19" tires.
And, as you said, it's fun to come across a Jeep Club, convened to strategize the next Obstacle, ask them if you can "play through" and then watch the expressions on their faces about how well the Mercedes handles the situation.

I attached a description I wrote back in 2011, of how I deal with off-road tire injuries. While our 2010 ML diesel had runflats and no spare, which I rectified before taking delivery, much of it applies today, and I still carry all those things in the back. Along with recovery strap, spare hitch *****, and of course snow gear.

RW15

Thanks for the document. This is all very helpful and will ease the learning curve. Much appreciated, the cyber mentoring.

Those current Nokian 'All Weather' tires look great, exactly what I want, either the WR G4 or the Rotiiva AT Plus. But unfortunately back to why I first posted: They don't seem to sell them (or at least aren't currently available) in the stock GLS sizes (275/50/R20, 275/55/R19), so I'd have to go up to 275/55/R20.

I used to live in Colorado and moved to the North Cascades in Washington a few years ago, but may move back to western Colorado in the relatively near future. If you see a white metallic GLS in an unexpected place in the San Juans or SE Utah in the next few years, that may be me!