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Learn from my mistake and save lots of $$$

7K views 1 reply 2 participants last post by  altamonte 
#1 ·
Good afternoon everyone,

I've posted numerous times previously about tire related issues with our GL550. At around $2000 to replace them on the car (295/40/21), it was frustrating to learn that I could have prolonged the life of the recent Continental's had I known/considered this before. By driving for long stretches with the GL in sport mode (ours was full-time), you are putting the camber of the car out of whack and reducing the tire life drastically. We drove less than 20k on the most recent tires before the inner walls were gone.
I recently had the car in for an alignment after putting brand new tires on. They could not get the camber corrected without adding eccentric bolts. However, while standing there considering spending the money on the bolts, I realized that we always keep the car in "Sport" mode. I climbed up on the lift, got in the car while up there, and pushed the button to take sport off. The techs and I all watched real-time as the shop's computer program adjusted and the car was in perfect alignment out of sport mode. When in sport mode the camber was way out of alignment, then it was instantly perfect. This is just a friendly caution if you're as ignorant as I apparently was to use the different airmatic modes judiciously. The ride is comfortable in all of them. I had rotated the tires twice in the less than 20k we'd put on it too, so that won't help.

Incidentally, there are other less expensive options now for this tire size that weren't available when I'd last replaced them. At that time there were only Pirelli Scorpions and Continental Conti's. I replaced ours with Lexani's that are made in this size now after researching them a bit. So far, they perform just as well as the Continental's had, look nice, and are quiet. The total for all four was $645, including shipping across the country from CA to the northeast.

TL/DR - Don't stay full-time in "sport" airmatic mode, or you'll replace tires faster. Consider Lexani tires when you replace your Pirelli/Continentals.
 
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#2 ·
GL's don't need to eat tires

You have it right - here's a bit more info.

What the owner’s manual does not tell you. GL’s don’t need to eat tires – but you need to understand what the systems do.

With AirMatic you have 3 ride heights (presuming no Off-Road 430 package).

Reference ride height is 0. The standard “city” ride height is 30mm below reference (there’s a reason for this – read on). The sport / lowered mode is another 15 mm below city ride height. Raised mode is 20mm above reference for +50mm above city ride height. On an alignment rack – stock ride is -30mm, sport is -45mm, and raised it is +20mm.

With the Off-Road package you have an intermediate high setting which is actually the normal reference – intended for Europe’s cobblestone streets and the desert sand dunes of the middle east, and still allow the CV joints to run at 62 mph (100 kph). The Off-Road package also adds an extra high level which adds yet another 30mm to the total height above the standard high setting. But I digress …

The “reference” height is one at which the SUV clears any sort of obstacles you might encounter while driving at less than 60 mph. Unless you have the Off-Road package - you can't pick this height.

The standard “city” height is intended for smooth pavement only – which is what most US roads are.

The sport height is intended for driving at over 85 mph on the German autobahns - and that 15mm lowering truly betters the aerodynamics for high speed runs plus it adds negative camber to aid cornering. But that height is NOT supposed to be used for normal driving. The lowered level camber is great enough that if you leave it there you eat tires.

If you like the look of the lowered height (I do), then here's a possibility for you – it’s what I did.

Realize that the ML-AMG rides 15mm lowered all the time. The engineers are not idiots – the stock computer allows setting the reference height for AMG or not, and the eccentric bolt used in the ML and GL both has enough adjustment to allow the camber to be set for the AMG without resorting to the more extreme adjustment bolt. If the tech knows what he is doing there’s no replacement of the bolt needed. If your dealership wants to make a few bucks – well, you know how that goes.

I asked the alignment tech at my dealership to set the "standard" height of the GL to the AMG value (all done via Xentry/DAS). As the stock AMG lowering value is 15mm, I actually had him go a little further - lowering the front 20mm and the rear 25mm. The resultant look - even space around the wheel to the fender - in front, above, and behind the tire. (don’t forget to re-aim the headlights after you do this).

Then the tech aligned the vehicle so it was at normal spec even though lowered. Remember the stock camber bolt works on the AMG SUV – and it worked out just fine on my car. Camber spec is 1 degree 50 minutes - just shy of 2 degrees. The stock eccentric bolt should have enough travel to make it happen - but if need be the added eccentric (you were looking at doing it) at my dealership was only going to cost $30 for both sides together with labor – and they had the bolts in stock. Cheap enough if I had needed it.

Voila – camber and all alignment perfectly in spec. I had this done 2 years and 27,000 miles ago – tires wear flat and even (normal rotation every year), and are only about ½ worn – should easily get 50,000 miles out of them.

As to the cost of your tires – I replaced the 10x21” wheels with Mercedes W164 AMG wheels with a 9x20" size. Then I switched to 285/50-20’s. From Conti in SUV tire - $180 each. That 10% increase in sidewall height really helps. I run 42 lbs all 4 corners. Ride quality up, tire life up, tire cost ½ of what it otherwise would be. Add in that I don't eat tires - and I have a 4-5x improvement over what most GL owners do.

Cheers !
 
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