JosanK

I have been experimenting with tire pressures. I find that setting cold pressure on the front to 40 and the rear to 42 makes the car feel far more nimble and gives a better ride.

The max pressure stated on the side of the tire is 51 so I'm well within limits. Question: Is this the "cold" maximum or the max at any temperature?

I am receiving conflicting info on the wisdom of doing this.

I have had a performance tire shop and a Mercedes tech give the thumbs up on this. The mbusa website says running more pressure is just fine but doesn't get into numbers.

I have had another Mercedes tech and advice from this very forum saying this is too high.


What's the reality?

Interesting side note, on my 98 Lexus LS400 they recommend a cold pressure of 32 but go on to recommend 38 for "sustained driving over 100 mph".

vraa

I'm not going to comment on the SL because that's actually been in the back of the garage for about a month now.

The LS however, I'm at 36 PSI and i do sprited driving on that and it's perfect, however I do lose traction quite easily and even though the owners manual says no more, I'm still getting a lot more wear on the outter edges in the rear rather then having an even wear.

Twinturbo

All tyre pressure are related to cold pressures. Inflating your tyres by about 6psi is usually recommended to enhance grip, rolling resistance, fuel consumption, wear and handling. If it is within the limits it is fine. The pressures on the placard are given to give a comfy ride, however, due to the factors I just mentioned, you need to increase the tyre pressures a bit in fast driving. It's up to you, if your willing to sacrifice some comfort or not. Considering your an 55 owner, I'd say you are so try it out. However, I do not know what the normal recommended pressures are, but up to 10 psi should be no worry at all.

IngenereAMG

I have tracked my SL55 and what is really necessary is to DROP the cold tire pressures on track days. THAT is what will help the tire bite better. Because of the harder work that you will doing during 'sprited' driving the tires will build up plenty of heat...and therefore there will be a fairly hefty pressure increase. I will generally bleed off some of that pressure to get the tire to bite better in the corners again.

Pressures are increased for high speed highway driving to improve milage....but if you want the tire to perform better in the corners...I will generally run 28/30 cold or lower, but for everyday driving the factory pressures are fine.

pablo4.2

If the outer edges on both sides are wearing faster than the center your tires are underinflated.

pablo4.2

Since tire pressures can increase 10-15PSI when hot on hard track driving you have a point but it is different for different cars. Since tire pressures never increase so much on the street an increase may be a good idea as long as the cold inflation doesn't exceed the max. Like you I have found standard recommended pressures are fine but I have yet to experiment much with the SL55 tire pressure.