stevez11

I've got a '98 CLK320 running Eibach Pro Kit springs with Bilstein Sport shocks (and with #4 pads front and rear).

The problem I am experiencing is that the center portions of both of my rear tires is wearing out much faster than the edges of these tires, even though I only inflate the tires to 33 PSI.

It is the kind of problem I would expect to see if I was grossly over-inflating these tires, but since I am not, I am assuming that it is either an issue of camber or toe alignment.

However, because my CLK is only lowered ~1.2", I have deduced (possibly incorrectly) from various postings that I probably do not need either the Renntech or K-MAC kits.

ANY OPINIONS ON MY ISSUE WOULD BE MUCH APPRECIATED.

Mach430

Do you have a copy of your current alignment specs?

stevez11

I will get those tomorrow, and post it.

stevez11

Here are the relevant settings:

Driver-Rear Camber: -4.5 deg.
Driver-Rear Toe: 0.90 deg.

Passenger-Rear Camber: -1.1 deg.
Passenger-Rear Toe: 0.95 deg.

Rear Camber is not adjustable without an aftermarket kit.

I had the toe settings adjusted today, and they are now both at 0.15 deg. (according to the electronic readout, the acceptable range is 0.12 degrees to .28 degrees on the driver's side, and the reverse on the passenger's side).

The shop stated that they think my tire wear problem was casued by a combination of excessive toe-in and "under"-inflating the tires...

they stated 33 PSI is under-inflated for high-perf., low-profile tires; that stiff sidewalls require a certain amount of pressure before the contact portion of the tread is even, and that they got this information directly from the tire manufacturers.

I AM NOT CONVINCED THAT MY PROBLEM IS RESOVLED...I had new tires put on the back today (Pilot Sport A/S), so I should be able to judge the alignment changes.

stevez11

Just wanted to add, even though the negative camber is EXCESSIVE on the driver's side, it does NOT appear to be a "primary" factor in my tire wear problem, since that problem was seen on both rear tires...

however, now that I am researching what proper camber values should be, this seems to be a MAJOR problem by itself.

stevez11

HOW DOES ONE END UP WITH A 4.5 DEGREE NEGATIVE CAMBER, SIMPLY BY CHANGING THE SPRINGS ???

SoCalCLK

Steve,

I am running Brabus Springs with OEM Shocks and am asking myself the same question! The negative camber is bad, and I will admit it is worse now than it was when I first put on the springs in July 2003.

My guess is that the springs are settling, and that due to the car being heavy and the suspension being a multi-link set-up which has the springs and shocks sitting seperately, perhaps this triggers the massive negative camber!

I would suggest that next time you take the tires in for rotation, have them correct the rear camber the best they can...

BTW- I have been running 36 PSI (Cold) on all fours and have lasted 18,800 miles!

E55AMG99

Bump the tire pressure up a few PSI. Worn centers are more a sign of under inflation. I run 35-36 (cold) in my 18" Pilot Sports on the rear of my CLK compared to 32 in the stock 17". Camber wear problems would be more evident on the inside of the tires.

SoCalCLK

I agree. 36 psi (COLD) should help alleviate the premature wearing of the tires, even with a negative camber.

The next time you go for tires ask them to adjust the camber (as best they can, and this can be done at any reputable tuner shop) and that should do the trick.

varainstructor

These assesments on tire pressure are right on. It is a common misconception that the internal tread wear is a result of over inflation. To an extent, this is true. The part that is hard to understand is a lower cold tire pressure can result in a excessively high operating tire pressure. The key to tire performance is the hot tire pressure that is created under your driving conditions.

With low profile performance tires, your tire pressures,(always measured with a cold tire condition), are much more critical. At the risk of over simplifing the situation, this is what you have experienced:

A low tire pressure, while flattening the interior tread initially, will be subject to much greater friction. The greater the friction, the more radical the increase in tire temperature. The more radical (and rapid) the increase in tire temps, the more radical and greater the increase in tire pressure. So, you may be a few pounds low with cold pressures and end up a pound or two too high when the tires come up to operating temps/pressure.

Radical camber adjustments will also narrow the window of optimal pressures for similar friction producing reasons. The variations may only be a couple of pounds either way, but will have a very determined effect on your tire wear as you have found out. I have found that the optimum cold tire pressures for the stock 17's to be 34 psi front and 36 psi rear. Larger diameter, lower profile tires will require slight variations but no more than a pound. And keep in mind, one pound is a big leap for high performance tires. Consider that racers play with quarters and halves of psi to find the perfect tire perfomance. Your tires are not that dissimilar to a racer's rain or intermediate race tire.

varainstructor

p.s.

Before you invest in camber alterations that may lead you down the dark path of perpetually "chasing" your suspension adjustments, play with your pressures...AIR IS CHEAP!!!

SoCalCLK

34 / 36. Perfect combo!

Now my next dilemma is to decide on tires. Michelin Pilots or Yokohama AVS?

toymr2trd

Okay.... you guys. Yesterday while driving home from work... I felt this weird feeling... I stop the car and sure enough...right rear tire was blown.... I start taking it off w/ that stupid jack supplied w/ the car... the damn thing is giving out. End up calling AAA and finally they come and take the tire out.... the inside of my tire was totally shreaded... but the center still had some good thread still. My car I've noticed that the inside of the tires are wearing out pretty damn quick. I'm going to go and buy me a tire now.... but just wondering... you guys think my camber needs to be played with? or just a matter of alignment. How much is a camber kit anyways for a benz? Thanks guys..... OOhhh what if I install my Kleeman suspension and slap on my Iforged wheels.... will I need to redo my alignment again? Thanks guys

varainstructor

As for the current condition of your car's camber, you should have a four wheel alignment performed by a reputable service center. They should check your camber all the way around to comply with factory specs. There is enough adjustment built into the car for this type of minor correction. For street applications, this is perfectly suited to the car. Some guys will set a more aggressive camber to their cars using after market kits once they have upsized their wheels (18's and / or 19's) solely for the purpose of creating fender clearance.

The problem with aggressive camber, though great for handling, it's hell on tires and definitly not for street applicatioins (unless your car is show only, or you can grow a tire tree in your backyard). In the long run, it is far cheaper, and better looking in my opinion, to have a quality body shop roll your fenders for the extra fraction of an inch you need to clear the more radical wheel off-sets. It will allow you to maintain factory camber specs.

That being said, any time you go to fresh rubber or install suspension components, a four wheel alignment is an absolute requirement. Even if you are replacing with original factory parts, disassembly of the suspension will alter the geometry of the swing arm assemblies just enough to cause issues later. Trust me, the alignment is money well spent.

By the way, if you firgure out how to grow that tire tree...let me know.