Adi-Benz

Hey guys,

Just wanted to hear some opinions on what psi is best to run for daily driving use.
235/35/19 F
265/30/19 R
Conti DWS06
Currently running about 40 front and 45 rear (according to a note on tirerack, 42+psi is required for load rating for rears?)

m a x i m u s

I run 40 all around.

Nando_514

Open the fuel door, inside there's a placard with suggested tire pressures depending on load.

40 all around for me too... What I'm interested in, is what tire pressures some of you use on the track

Jasonoff

x2

What kind of oil do you use?

Adi-Benz

Good to hear some track pressures too.

Running different size rims and tires than oem so I would think it would not be the same, 30 front 35 rear is what I kept my oem ones at.

Ludedude

If you really want to determine the correct pressure to support the same loads as manufacturer specs for size, load rating and inflation, you can peruse the attached document.

Note: this is geared towards trucks but the concepts are the same and can be applied to passenger car tires as well.

Essentially though, you need to duplicate the manufacturer's load rating per tire or axle by determining what pressure you need in your new tires to meet or exceed the same. That information should be relatively easy to obtain from the new tire manufacturer.

Or you can just guess and say well the internet says this so I'm sure it's fine.

bhamg

Many of us also factor in handling, even tread wear and relative ride comfort into the equation. That said, IMO 40lbs all-around is an excellent starting point. I'm at 40F/39R myself on 245/275 (19).

Vladds

I just finished a set of DWS, the set that was on the car when I bought it.
the rears wear like there's too much pressure, if you commute alone in the car, even at 41 PSI.
I was trying to run 39, but then a low pressure warning kicks in and it is a slight nuisance to erase the message.


I am starting to look at the rear Michelin PSS and I start to see signs of biased center wear at 41 PSI. I have to reset the sensors somehow for a lower pressure.

MTV10

42 all around here.

chrisridebike8

There's a way to set the reference PSI. I have my reference set to 35 psi I think. I'll look when I drive to work this morning.

Ludedude

Yeah, it's under the tire pressure menu in the speedo screen. Under service I think? If you select the tire pressure display then click OK on the steering wheel, it will ask if you want to reset the sensors to the current pressures as a default.

chrisridebike8

Crap. Now I am at work. I forgot to check on the way in I will do it on the way out.

NotABaller

The tire screen is the second last one, I think.

From the AMG screen, go left by one or two. You should see tire pressure. If you go into tire pressure, it'll show you all 4 of your tires' PSI. If you press the down button (not the OK button), it will ask if you want to confirm these as the new reference values. I just did this a few weeks ago and got stuck with setting the new reference values. I kept pressing Ok and other combinations, even tried pressing the phone call button. It's the down arrow!

Currently running 42 front 32 rear for street on 245/265 19" MPSS.

I am Jeff

These are my cold temps. 39 f and 41 r

I am Jeff

If youre running 32 rear pressure, be prepared to buy new rear wheels soon..

D3-AMG

That only applies to 2010+ models. My 2009 is stupid and doesn't show individual pressures.

Also, the pressures listed in my fuel door are different from listed in the driver's door.

Ludedude

As they all are. The pressures in the driver's door are for full rated GVW. The ones in the fuel door have options for lighter loads as well.

NotABaller

why? From hitting a pothole or something?

I am Jeff

I'm going to give you the benefit of the doubt that you're not being a smart a ss, and that you really don't know. 30 psi on a 30 profile tire will absolutely destroy your wheels.

NotABaller

I'm running this for traction reasons. Is 30 PSI really too low for daily? People here run that or even lower at the strip or track.

Adi-Benz

You answered your own question tho.

NotABaller

in my mind, if the rims can hold up to stresses at the track then surely it's okay for the street. Is hiting rumble strips at 200KMH really much better than going through bad roads?

I am Jeff

Run your wheels at 30 psi for a month and let us know how that works out for you.

NotABaller

just filled up my air because I didn't want to take this chance!

Diabolis

First, there are no potholes on a race track. The track pavement is considerably smoother than what you'll find even on the nicest public roads. And, even when you drive over the curbing (rumble strips) at the corner apex, you are always driving over them with the unloaded wheels, i.e. when they are probably supporting no more than 20% of the weight of the car (if you ever go over the curbing with the loaded side, I guarantee you that your rims and tires are going to be the least of your concerns).

Second, the high tire temperatures on the track will cause the cold tire pressures to rise by about 10 psi. The most I've seen on the street is about 4 psi.

Third, at the track the load in the car is usually that of just the driver. On the street you may also have to carry a passenger or three as well as some cargo.

Fourth, tire longevity on a race track is measured in hours as opposed to years, so tire wear is not a concern. And, contrary to what some people may tell you, the rims absolutely DO suffer and are also wear and tear items. Aluminum alloys definitely weaken from fatigue and I wouldn't even think of using 10 year old rims on my track rat when entering a corner at 240 km/h and 1.8 lateral Gs, just like I wouldn't use an expired seat or safety harness.

So - when you take all of these factors into account, the cold pressures that you start with at the track need to be about 12-15 psi lower than what you need on the road.