KeithS

I looked at my tires the other day (I have a 2015 SL550 w/ about 22K miles on them) and fronts are showing a lot of wear towards the inside of the tires. I brought the car into a german auto repair shop in orlando and asked them.... when I get new tires, will a 4 wheel alignment correct this issue? He said... on these cars, you can adjust the toe, but not the camber so this might not be able to be corrected. Does anyone know if this is correct? Do you have to buy something separately to be able to adjust the camber?

Dr. Manhattan

I've been wondering the same thing about the rear suspension on my car. When viewed from the rear, there's a clearly visible amount of negative camber back there. I assume this is where all the complaints about inner tire wear and cracks in the inside rear wheels are coming from (19s contributing their fair share, of course). My fronts aren't nearly as negative as the rears, but that doesn't mean I won't have the same problem as you. I was hoping I could specify a zero-camber alignment when the time comes...I hope it's all adjustable.

slk55er

There is a reason for the negative camber (tires are flat on the pavement when cornering hard and you need the full contact patch.) BMWs are notorious for rear camber causing inside tire wear. On my '83 633CSi and on a '95 M3, I recall flipping the rear tires on the rims because the outside had lots of tread remaining. On our race cars, we always had front adjustable camber plates 'cause we'd take tire temperatures across the tread and adjust the camber to yield even temperature across the tread.

If you do a search for camber kits you may find what you need. Here's a link for front camber adjustment hardware that may be of interest.

https://www.ebay.com/itm/Mercedes-Adjustable-Front-A-arm-Camber-Kit-R230-SL550-SL550-SL55-SL63-ABC/303525706472?fits=Model%3ASL550%7CMake%3AMercedes-Benz&hash=item46ab8abae8:gXgAAOSwhkVa710E#vi-ilComp

Click on "See compatible vehicles" to check for your model.

Here's the link for rear adjustment hardware:

https://www.ebay.com/itm/Mercedes-Re...AAAOSwSypY-hwN

I see rear adjustment hardware for earlier model SLs but nothing for '17-'19 model years. Frankly though, it is not worth the $$$ and bother to install these -- just monitor the inside tread of your tires and expect to buy new rubber when necessary.

Wolfman

Just inflate your rears by 3PSI and your inner wear will be fine. SL's have had that for decades...
Different story if you lowered your car.
We also have a sponsor here that deals with camber adjustments https://k-mac-camber-kits.com/. I have no experience with their products but maybe worth a look. Mercedes used to also have camber adjustment kits for the R230. Not sure if that is the same for the R231.
Since I received the above advice from a very experienced MB tech, our tires and wheels have been great and we have lowered all our SL's.
The higher pressure is also responsible to cracks to the wheel barrels, especially with run flats.

slk55er

Hey Wolfman, what do you mean by "wheel barrels"? Do you mean the outer rim edge? Seems like a higher pressure would do more to protect them. Or do you mean the portion of the wheel that goes over the hub? Also...

Effect of tire pressure on inner tire tread wear due to camber is always a topic of discussion and consternation. I've typically thought as you have indicated -- increase tire pressure -- 'cause making the tire balloon more would cause more wear (and temperature) in the center of the tire, reducing wear on the inside of the tread. However, here is a different perspective from my long-time racing partner who I believe is an expert when it comes to such matters.

We discussed several different situations, including obvious ones where the temperature (and wear) in the center of the tread is high. Obviously, reduce pressure. But higher heat and wear due to camber when camber is not adjustable is open to discussion.

So picture that you are behind the driver-side front tire and you see the following temperatures (degrees fahenheit):

OUTSIDE MIDDLE INSIDE
140 140 160

Here is my buddy's reply:
I've used my optical pyrometer to measure tire temps across the tread and tend to agree with this, but it is not straight forward. So what's your perspective and experience on this issue?

Wolfman

Your friends explanation is quite interesting but wonder if it may depend on the situation. For the track there are different dynamics in play. You align with negative camber and under inflate your high-performance rubber which needs to be warm for grip. The warm tires pressure would likely equal the cars recommended cold air temp. Grip vs longevity? A set of tires on the track last maybe a few track days (at least with AMG's), depending on driving. You'd wish for longer with regular driving

That said, I don't have the answer. My thinking is that since we increased the tire pressure on the rears (light over inflation) on our last 4 SL's (1 R230, 3 R231's), the problem has simply gone away and have been able to get over 20k miles out of our PSS and PS4's. On our old PS3's we got 6-8k miles on the rears before having bald tires on the inside while looking good on the outside. Same for bend or cracked wheels and yes, I meant the inner lip, not the barrel itself.

steve sl550

Wolfman
Pls advise what pressure you are recommending F&R when using factory run flats on MY 2017 and newer
3# over what for rear and what to run on fronts
Tx

Wolfman

Hi Steve,
It’s been almost 2 years since we have had our 2017 SL swapped for the AMG GTC so I can’t quite remember.
Just take the std. PSI from the fuel cover and add it. I think I bumped the fronts by just a touch.

slk55er

Thanks for your perspective. My SL is in winter storage now, but I'll try to run some tests on my CLS53, installing new Vredestein Quatrac Pro All-weathers this week. I''ll start with recommended pressures on the fuel flap (F:42, R:41, M&S F:42, R:44). With the all-weathers, I'll start with 42 all around and go +4psi and -4psi. I'll measure tire temps across the tread after driving at 50-60 mph. I'll do the same with my SL when I put my summer tires on. I'll start a new thread if I get some decent results to post.

Wolfman

Just to be sure, my recommendation is just for the suspension setup of the SL. I remember our W213 E63s has high PSI numbers like yours too and was hard like a brick. When we picked up the car from the dealer, some idiot actually had set them to 50psi...So we ended up under inflating the AMG by a good 3 psi and that worked great for the car. We also dropped the ride height by 20mm via lowering module without alignment (normally not recommended) but the tires lasted for a bit over 2 years without inner wear. The same could unfortunately not be said for for Pirelli Sottozero P240 snows which didn't last 6k miles
I am also running our GTC lower than stock (30-32psi).

Point is that each car has an optimal setting that seems to work best for it.

TennesseeZ4

My last set of Michelin AS3+ were worn down at 12K miles; I had an alignment done when they were installed; always ran the rears at +2 psi over the gas door recommendations. Had about 1/32nd left on the tread; drove in to the dealership during a rain storm to get new tires, and hydroplaned several times on the way in. Michelin had a 40K mile warranty on these tires, and provided me with a rebate to offset the variance. Fronts were about 5/32nds at that time, across the tread pattern. Something tells me I may have been a torque junky with the SL550!

And I agree with Wolfman on the variation on tire temps as the pressure guidance for street vs race track; as a former SCCA National License holder, my race set up was driven by the pyrometer; but at different tracks, you had different settings to optimize your contact patch. For the fronts, we varied camber over a large range from Road Atlanta to Sebring to Mid Ohio, to keep the largest contact patch on the track during hard cornering. Tire pressure, camber and toe in/out really made a difference on the track and each would alter the temps across the tread of the tire; and we would change each over the course of a weekend using the pyrometer and the ever popular stop watch (why can you not go faster?). The computerized alignment platforms employed by most Mercedes dealers provide an optimum setting for a passenger vehicle.

So here are the photos of my last set of Michelins on our dearly departed and often missed 2013 SL550:



Left Rear

Right Rear

LeadfootZ3

3 PSI higher than what? I have a whole table of values in the gas cover.