Hello All,

I have been reading lots of threads about winter tires for x166 GL but I have a few questions.

I have a 2015 GL350 with stock 295/40R21 tires.

I have read about folks downsizing to a 19 or 20 inch wheel for winter tires. I put the stock 20 inch wheel size into the offset calculator at wheelsize.com.

It looks like the outer dimension of the tire is more than an inch to the inside. Therefore the overall tire stance is more than 2 inches narrower with 20 inch wheels than with 21 inch stock.

Much of this has to do with the 19 and 20 inch wheels being 8.5 inches wide vs 10 inch wide for the 21 wheels.

1) Any thoughts on running 2 inches narrower? I dont like this idea but I like the idea of a higher sidewall and narrower in snow. (plus lower prices for the tires)

2) I haven heard anyone running 275/45/21 tires instead of stock tire sizes. Anyone tried this or heard that it is approved?

I have not hear anyone doing this so I am guessing its not a good idea.

I am leaning towards buying used oem 21 inch wheels and putting some new stock size 21 perelli winter tires. It sounds like no one is unhappy running 295 wide tires in the snow.

I have read about two different kinds of perelli tires, im not sure how to tell the difference when shopping. They're doesn't seem to be many choices now in canada but the perelli tires are available.

I was asking mercedes if the GL vehicles, that come with stock 21 inch tires, have a narrower hub width to accommodate the 10 inch wheels or not. I couldn't get a straight answer.

I checked my vin and it says AMG side skirt and wheel arch enlargement. Maybe the hub width is constant and the body panels accommodate the wider wheels?

No one i have read about was complaining about the look of putting 20 or 19 inch wheels in place of stock 21 inch wheels but it must look a bit off, being an inch back under the wheel well.

Maybe I am overthinking all of this.

Any thoughts would be appreciated.

Thanks
Matt

 

I have a set of 20" replica wheels (Replika is the brand) and they are awesome. Not sure on tire size but I believe it's the same size as what comes on the 20" GL wheels from the factory (you can look it up)

I wouldn't go 21 for winter tires. Really expensive, too wide for snow, etc.

Get a set of 20" replica or factory wheels, then get a set of winter tires.

I would start checking Craigslist/Kijiji now and maybe you'll get lucky. People lease these cars all the time and slots of sets of winter wheels lying around as leases get returned. A 3 or 4 year lease means people are now returning 2017-18-19 models which have rims that will fit your GL perfectly.

 

Thanks bha1 for your reply. Did you have stock 21 inch wheels that you replaced with 20 inch replica wheels?

 

Matt,

You actually want the narrowest ties in snow. It's counter-intuitive, as large contact patches provide greater braking, acceleration, and cornering on dry pavement.

In contrast, a smaller contact patch provides better traction on snow/ice as the vehicle weight is concentrated. Think about how and why skis work. You don't want skis on your truck that easily glide across snow and ice.

Get the 19" wheels and enjoy the benefits of lower costs, taller sidewalls, and better performance on snow/ice. Granted, with smaller wheels on snow tires you won't have the same absolute performance on dry pavement in the winter, but the whole point of snow tires is safety during the season when you should not be pushing extremes anyway.

 

Thank you cadetdrivr for your reply,

Yes I agree and undersstand what you are saying with the benefits of more rubber below the rim and a narrower tread.

However I have my concerns about the offset and dont have a straight answer about taking off 21 inch stock wheels and running 2" narrower. I would be tempted to put in wheel spacers but then i would just rather run stock tire size given the other side of the argument:

1) everyone who ran 295/40/21 winter tires on a GL was really happy and would recommend doing it.

2) The benefits of narrower tires in the snow seem to be minimal given the user reports and this road test
It seems that the quality of the winter tire has much more impact on performance than tread width. Tread width at a percent to a few percent in difference, and quality of tire in the 10-20 percent in difference in performance. Just to put into perspective, based on the winter road tests in the above youtube link. (of course they didn't test a GL with 295 tread).

3) The reduction of dry and wet performance during the winter.

4) This is my main hang up or lack of clarity... My GL was engineered for stock tires size with stock 10 inch wide wheels and less positive offset.

19 and 20 inch wheels have ET +62mm offset and my 10 inch wheels have ET +46. So i am losing width in offset and again with a narrower rim, if I install OEM 19 or 20 inch wheels. This produces a 2" narrower stance. I am more confident with a wider tread than messing with extreme offset discrepancies until I get more information.

The dealership hasn't been much help yet.

If I had a little more info on how putting 8.5 inch wheels on my configuration works i would be much more ready to jump into some 20 inch wheels.

If I found replica wheels with an offset of +35 then i would maintain the existing outer tread stance for the vehicle.

In retrospect, I wish i bought a model with stock 20 inch wheels so the winter package wound be completely straight forward and more affordable.

Again, am i way overthinking this? i haven heard anyone else bring up these challenges of swapping out the 10 inch 21" wheels for smaller wheels but over 2" narrower sounds too much for me if i have to take a fast corner and the roof box loaded and the entire family onboard.

Many thanks for reading!

 

Directly from the horse's mouth (the manual):

 

Thank you w220430,
I just got off the phone with the service dept at my dealership and they confirmed that any of these packages are good to go on my vehicle.
His 2 cents are to go with any of these narrower profiles for better snow handling.
I had a lead on some beautiful OEM AMG 21 wheels for $500 canadian dollars that were tempting me but I will pass and keep looking.
He said yes, the aesthetics will change with the wheel backed under the wheel arch by and inch but there will be increased life for the wheel bearings and stick to the stock rim and tire combinations.
Others on the forums that were very happy with winter 295/40R21 wanted to keep the look of the vehicle and dry/wet performance.
The MB service tech also said some dry handling will be compromised in favour of snow performance with smaller wheels and the contact patch is moved inwards but it is within spec.
Before I spoke with the service dept, i spoke with parts and they had no other wheels listed and no other tires available than the stock perelli size. I started asking questions before they passed me off to the service tech who was very helpful.
For anyone in central Ontario, i recommend staying far away from mercedes Barrie. Mercedes kitchener waterloo has been night and day better in every regard and worth going the extra distance every time.
Thanks to all and I hope this helps others out there!