Well, it's that time of year again...NH State inspection time for me.

I go down to my friendly local shop for my sticker and since my car is basically 100% bone-stock the whole process is usually quite painless.

At the end of the winter season this year, I mounted up a fresh set of Michelin PSS's to my CLS 18" wheels (~ April 2012) and set the pressures based on the inner door striker recommendation (32 Front, 35 Rear IIRC) The ride was nice and comfortable that way, so I didn't make any further adjustments to those pressure values.

As the car went up on the lift today, the mechanic showed me that the tires were basically worn-out already.... but not in the typical "my-car-is-slammed-and-the-inner-bead-is-corded" way that guys always talk about on this forum. In fact, the center of the tread was still quite good, but both the inner and outer tread areas were down almost all the way to the wear bars, indicating to me that the center of the tire wasn't really doing it's job at all. To me, that sounds like not enough air pressure all the way around.

I'll confess I don't own an IR pyrometer, so I've never checked tire temps across the tread to optimize my tire pressures, etc. and I dont' use nitrogen to fill them either. There is no other indication of a bad alignment on the car, so I seem to be facing the reality that the PSS wants more pressure than the MB factory spec.

Fronts are 245/40-18
Rears are 275/35-18


Anyone have a pressure setting that seems to be giving them more consistent wear across the tread? It's a bit of a bummer since these tires have maybe 3000 miles on them and ran me close to $1200 for the set. Live and learn, I suppose.



Oh, and the shop said I can forget about passing inspection with my MBH long tube headers and primary cat delete.... so I guess I'll have to leave those hanging on my office wall for a few more months while I consider how to work around that obstacle too.


-G

 

I think Im at around 33-37 in the rears and they are not wearing out like that.Id have to check but if you filled them to 35 in the summer heat you most def were around 28-30 in colder temps.

 

Thanks Angelo...

Yeah, it's starting to get cold around here. I can always tell becuase my car feels absolutely "beastie" in the mornings with the extra power. One of these days I'll have to get a ride in a "real" E55 to see what 530WHP feels like.

On that subject, how worried should I be about exhaust mods and passing NH inspection? Is it just a matter of finding a "friendlier" shop to put the sticker on? I don't want to have to deal with swapping parts every year to pass inspection. That reminds me too much of the crap I used to deal with in CA when I lived there.


-G

 

Its crazzy how strict NH has gotten.I can remember being jealous when they didnt even check for cats back in the day,I live in MA and we have the hardest inspection that even checks vins from the ecu to match the car but every shop around my area dosnt care and just plugs it in and if there is no pending codes its all set.

I have taken my car to 3 different places and passed every time with ease

 

I run 36 front/37 rear cold.

PSS tire wear is great.....so far, much better than my PS2s were.

 

I have a brand new set waiting to go on and an IR thermometer. After I get em mounted up (Monday hopefully) I'll play around a lil and see what I get.

 

On the E63 with 245/40-18 front and 265/35-18 rear I have to run 41 front and 36 rear to get even tread wear across the tires. It really feels sharper and more responsive in turns, we notice no deterioration in ride quality.

 

Interesting.

You guys have quite a bit of variation in your settings.... Some run more pressure up front than rear, others are just the opposite. My guess is that I wasn't watching my pressures carefully enough over the summer and they ended up too low.

Pyrometers are cheap these days, so I think I'll pick one up when get my next set of tires and really fine tune my settings..... Pyrometers are a LOT cheaper than replacing tires once a year!

BBBSS, looking forward to seeing your data.


-G

 

Not sure the tire pyrometer will give you any useful data, but have fun .

Serge from Benzworks had a recommendation on tire pressures, basically several pounds higher than factory recommendations if the car was lowered. Interesting to see that MB has two recommended tire pressures - (1) normal driving and (2) for high speed driving.

 

I probably should have acknowledged that the factory recommendations only really make sense for the original factory OEM tires....

The PSS seems to want quite a bit more pressure than I gave it originally. Live and learn.



-G

 

Incorrect, sorry.

 

I changed my fronts recently to Hankook Ventus v12's (19's) and run them at 42psi - Rears at 36psi - interestingly, if you look at the options Tirerack has for replacement tires (19's) for our cars all the selections including the PSS's recommend to run the fronts at 42 psi 'for proper load' - no such note for 18's though?
quote: from tirerack site
Front: XL/RF tires required. Customer must maintain higher tire pressure levels of 42psi for proper load. *********PLEASE COPY THIS NOTE ONTO INVOICE************ Rear: Mercedes recommends XL rated tires for ride issues. Some customers have experienced vibration issues from standard load tires.

 

so what is the vote on tire pressure for the rears guys ? Just got my michelin PSS for the rear in 275/35/18

 

I went up to 40 rear and 42 front since my original post.

Logged about 800 miles so far on the new pressures. The ride isn't as harsh as I'd feared. It's too soon to know if the wear is more even or not.


-G

 

interesting. my Dunlop Direzzas are worn on both inside & outside shoulders ONLY. running 34 all around. will bump to 40 asap.

 

I have 19s PSS running 38 front 40 rears.
No problems with ride.

 

Interesting thread, I too have the PSS onj 18's stock sizing all around and am running 34 front and 38 rear. No problems at all..

Guys at discount said to run 42 front 36 rear due to load, but did not sound right, these cars tend to plow corners so I want that extra bite, But I might play around with these pressures after reading some of these posts..

 

I got mine mounted Monday but it was raining so couldn't play with the temp gun yet. Shop set em at 35 all around and it feels a lil soft to me.

Stock front size and 275/35.18 rears here as well.

 

IR pyrometers are worthless on tires and even more worthless on street tires. Tire pryos are probe that pierce the rubber down to the skid (the belt binder layer)

40psi rear and 38psi front works well on my PSS's

 

Figure it can't hurt to see what comes up. I know my friends truck with a low quality lift had the front end looking like a bow legged hooker and you could very easily feel the temperature change across the tread. Even after a 2 hour drive at near highway speeds.

 

That's what I've been reading. The probe-type will work, but you have to measure the tires FAST after stopping the car. The tires cool down very quickly so it's hard to get an accurate measurement.

I think there is value in trying to measure tire temps, but it sounds like quite a bit more effort than I originally expected.


-G

 

I use 36 psi cold front and rear. Has been working well so far.

 

I run 40 in the fronts and 30 in the rears.

 

Just changed mine to 40 front and 36 rear.. Fronts up from 34 and rears the same, noticed the car rolls a little better thru turns, but bumps are harsher..

Getting aligned tomorrow and will speak with them about proper pressures, these guys are good, prepare track cars all the time...

 

BTT....

I just got a new set of PSS 275's (rear) installed.

Upon mature reflection since my original post, it appears that my tire pressures were not too low, but were in fact TOO HIGH. Excessive wear showing at the center of the tread indicates too much air pressure, not too little.

My previous PSS's were set at 35psi (rear) and that was apparently too high.... I guess I'll try something around 30psi out back unless someone here has some new "real life" data on what kind of pressure these tires like.....

Only got about 4000 miles out of my last set of PSSs.... I probably could have eeeked them out to 6000 miles if the pressures were corrrect from the start.


-G