Mercedes SLK World banner

1 - 16 of 16 Posts

·
Registered 2009 SLK55 AMG
Joined
·
297 Posts
Discussion Starter #1
Replacing my tires, soon, and was wondering if there's an alignment fix for the car stepping out every time I go around a corner ('09 SLK55)...? Searched & reviewed all the forums for info, but, nothing was particularly helpful. Apparently, there's no camber adjustment on the rears? My wear is fairly even (the center more so than the outsides - due to higher tire pressures... Will bring those down by a couple psi...:D). It's just that, even with the best tires (Super Sports, 255/35 ZR18s on the rear), even with moderate throttle, the back end steps out. Worse, on large sweepers, it doesn't inspire confidence above 80 mph (my taller, narrower, smaller-tired WRX corners better)... Any suggestions (for improving handling w/o compromising my driving pleasure)?
 

·
Registered
Joined
·
500 Posts
By adjusting the rear tires pressure will improve your oversteer issues. In your case, it cause two issues. Oversteer and wear uneven in the center. So lower the rear tires pressure.
 

·
Premium Member
Joined
·
2,454 Posts
Replacing my tires, soon, and was wondering if there's an alignment fix for the car stepping out every time I go around a corner ('09 SLK55)...? Searched & reviewed all the forums for info, but, nothing was particularly helpful. Apparently, there's no camber adjustment on the rears? My wear is fairly even (the center more so than the outsides - due to higher tire pressures... Will bring those down by a couple psi...:D). It's just that, even with the best tires (Super Sports, 255/35 ZR18s on the rear), even with moderate throttle, the back end steps out. Worse, on large sweepers, it doesn't inspire confidence above 80 mph (my taller, narrower, smaller-tired WRX corners better)... Any suggestions (for improving handling w/o compromising my driving pleasure)?
http://www.slkworld.com/amgs/38001-alignment-fix-step-out.html

I thought we discussed this already? Are you still using 46PSI front/rear? :confused: There is no camber adjustment on the rear unless you buy an aftermarket camber kit and have it installed. SPC and K-MAC are some brands to consider.
 

·
Registered 2009 SLK55 AMG
Joined
·
297 Posts
Discussion Starter #4
By adjusting the rear tires pressure will improve your oversteer issues. In your case, it cause two issues. Oversteer and wear uneven in the center. So lower the rear tires pressure.
The center wear is to me (relatively) insignificant, I'm more concerned about the handling. I'll drop 'em down to 41 psi & see if that has any affect (on the handling). An easy fix, I admit. That's why I was asking about possible alignment (or other) solutions. Thanks!
 

·
Registered 2009 SLK55 AMG
Joined
·
297 Posts
Discussion Starter #5
http://www.slkworld.com/amgs/38001-alignment-fix-step-out.html

I thought we discussed this already? Are you still using 46PSI front/rear? :confused: There is no camber adjustment on the rear unless you buy an aftermarket camber kit and have it installed. SPC and K-MAC are some brands to consider.
We did. However, I was hoping for something a little more definitive (e.g., your answer above :) - much appreciated!) - thus, the posting in a different forum (potentially viewed by different sources of expert judgement?). My concern w/ aftermarket adjustment kits are that they will significantly increase the wear on the rears (the cost-benefit will be outside my comfort zone - in the other direction)...

I must admit, that it HAS been an enjoyable (ongoing) exercise to induce oversteer (with and without ESC), to fine-tune my driving style... :tazz:

Thanks, again, for your response.
 

·
Premium Member
Joined
·
2,454 Posts
The center wear is to me (relatively) insignificant, I'm more concerned about the handling. I'll drop 'em down to 41 psi & see if that has any affect (on the handling). An easy fix, I admit. That's why I was asking about possible alignment (or other) solutions. Thanks!
Is there a reason why you're using higher than recommended PSI? Try 34 front and 36 rear for OE specifications. I still recommend getting lifetime alignment at Firestone.
 

·
Premium Member
Joined
·
6,796 Posts
I'm with you James...

Does this fall under more is better (pressure)?!?!? Where did you ever get the impression that 46 or even 41 was a good idea? (Don't read too much tone into that question...)

Only time I've heard of those sort of numbers was for people storing their car and worried about flat spotting (which WAS an issue with bias ply tires, not an issue on current generation tires.).
 

·
Registered
Joined
·
500 Posts
Wow.....46 psi !!!! That's way too high and I can see why your car step out so easy. The factory setup has a slight negative camber for better handling with also cause a slight wear on the inside. Your tires pressure are so hight that now your tires probabbly only making 60% contact to the road. I run mine around 35 psi cold front and rear. I also has an adjustable aftermarket camber for the rear .
 

Attachments

·
Premium Member
Joined
·
2,454 Posts
I'm just looking at some tire pressures from a tire website. I'm not sure if there's some official information somewhere.

SLK55 AMG

2005-2007: 36 front, 39 rear
2008: 32 front, 35 rear
2009-2010: 34 front, 36 rear
2012-2013: 33 front, 36 rear
 

·
Premium Member
Joined
·
6,796 Posts
Agree Klinh...

Remember the contact patch when you're on the move is about 3" wide across the tire at spec'd pressure. You're making it as hard as a hockey puck...thereby decreasing the contact patch significantly (a .5" decrease is 15% ....)
 

·
Registered 2009 SLK55 AMG
Joined
·
297 Posts
Discussion Starter #11
I'm with you James...

Does this fall under more is better (pressure)?!?!? Where did you ever get the impression that 46 or even 41 was a good idea? (Don't read too much tone into that question...)

Only time I've heard of those sort of numbers was for people storing their car and worried about flat spotting (which WAS an issue with bias ply tires, not an issue on current generation tires.).
Actually, my driving style is (admittedly) hard... Especially on tires (& their sidewalls). Analyzing and testing various tire pressures on my other cars resulted in my higher pressures - it offered the best (to me) combination of handling, comfort and tire wear. This car is - different.

I just replaced my tires - at the recommended pressure - and, so far, have seen a significant improvement (well, the previous ones were BALD :rb)... We'll see how this affects my driving style as the tires break in and heat up...

Thanks, again!
 

·
Registered 2009 SLK55 AMG
Joined
·
297 Posts
Discussion Starter #12
Wow.....46 psi !!!! That's way too high and I can see why your car step out so easy. The factory setup has a slight negative camber for better handling with also cause a slight wear on the inside. Your tires pressure are so hight that now your tires probabbly only making 60% contact to the road. I run mine around 35 psi cold front and rear. I also has an adjustable aftermarket camber for the rear .
Haven't experienced that inside wear (because of the high pressure)... See post, above...

Looked for a P30 model, but, couldn't find one (only ≈45 '09s in the U.S.). I'll take a look at the aftermarket pieces mentioned. Are your (rear) brakes part of the performance package, or aftermarket (they look SWEET)?
 

·
Registered
Joined
·
500 Posts
Haven't experienced that inside wear (because of the high pressure)... See post, above...

Looked for a P30 model, but, couldn't find one (only ≈45 '09s in the U.S.). I'll take a look at the aftermarket pieces mentioned. Are your (rear) brakes part of the performance package, or aftermarket (they look SWEET)?


I think you mis-understood. The higher pressure like at 46 psi cause the tires to be rounder and that will cause the center to wear more then the outer. My brake are 030 package.
 

·
Registered 2009 SLK55 AMG
Joined
·
297 Posts
Discussion Starter #14
I think you mis-understood. The higher pressure like at 46 psi cause the tires to be rounder and that will cause the center to wear more then the outer. My brake are 030 package.
Nope. As I mentioned, I was experiencing center (tread) wear - due to the higher pressures (so, no inside wear)... I'll look into having my brakes upgraded to the 030 package... Thanks!
 

·
Premium member 2009 SLK55 AMG
Joined
·
4,918 Posts
So has lowering the tire pressure to the level recommended by the manufacturer helped with your traction problems?
 

·
Premium Member
Joined
·
806 Posts
46psi? Holy crap! Way too high! Right around mid 30s is where you should be at depending on conditions and tires. I autocross in the ~34-6ish range. With a bit more in front.
 
1 - 16 of 16 Posts
Top