Andrew-NY

Is 25 psi too low for everyday driving on 19" wheels? I want to keep my tires at the right pressure. i always feel that lower is better. Is this wrong?

What pressure do you guys use for everyday use?

BlownV8

Uh, yeah that's way too low. You will be bending some rims with that pressure. You need to be at least 40 psi in each wheel.

Andrew-NY

40 psi sounds a bit high. I just spent a few minutes reading the tire-rack threads and many recommend 35-38 in front and 32-34 rears. Luke recommends lower pressure in the rear. I don't know if this is accurate, but he definitely knows a lot more than me.

BlownV8

Maybe on a 3600 lb car. Our cars are much heavier and need the extra PSI to protect the rims. Not to mention, I think the lower pressure makes our cars feel squirrly because the additional weight flexes the sidewalls at the lower pressures.

Bend a few rims and bubble a few tires and you will be running higher pressures. I found out the hard way. Try running higher pressures for a few weeks and then lower it for a few weeks and see what feels best Your mileage will also greatly improve with higher pressures. In the end, just do what feels best to you.

mclarenm8d

Check under the gas cap cover ... I believe you will find the recommendations there. Your CL600 may be different than my CL55, but on my CL55 the recommendation is to actually go higher in the rear than the front. Tirerack qoutes are relative to the tire size, the bigger rear tires won't need as much air pressure to safely support a load. But that isn't necessarily pertinent to the specifics on the CL's.

Due to the perversions of how the ABC suspension work, I find going a little lower than recommended in the front makes the car ride smoother in the front, while going higher in the rear makes the car ride smoother in the rear. So, I have roughly a 32/40 split (18" rims).

Our CL's don't have LSD from the factory, which means that one can have the dreaded single-tire burn off when ESP is shut off. If you run the rear tires higher in pressure, it is easier to get both tires spinning for dual-tire burn offs. Just FYI if you are into that type of thing.

DFW01E55

Inside the fuel filler door you will find the recommended pressures, both cold and hot, full and normal loads. I'm not sure that I'd deviate from there too much, they seem to make sense.

Andrew-NY

I tried 38F/34R and the car seems pretty solid at this setting; I was definitely too low before.

Andrew-NY

In the past two days I've done some investigating:

Mercedes recommends R33/F29 for our cars with 18" wheels. Luke from Tirerack recommends 34F/32R for my CL600 with 19" wheels.

Why do you feel 40+ is the right pressure? You're significantly higher than what Luke and MB recommends for the CL. How do you come up with 40?

MarcusF

The "proper" way to determine the correct pressure for your car (pressures can vary from car to car due to weight, but this is especially true if we're talking about different wheels and tires) is to take a pyrometer and read the temperatures across the face of the tires. If you can get the temperature of the center of the tread, to be the average of the inner and outer sections of the tread "THAT" is the correct temperature for that tire on that car. Do that once for each tire and you'll be right on the money and know you're right. Don't be surprised if you have four different tire pressures. I use an infrared pyrometer, & I check the temperatures IMMEDIATELY after making several passes through left and right turns (no cool down lap).

There is another method for those who don't want to buy a pyrometer, that is to chalk the tires. Take a piece of chalk, run it across the tread portion of the tires and about an inch down the sidewall. Drive through some curves and check the chalk. If all the chalk is rubbed off the face of the tread, and about one sixteenth of an inch is rubbed off the sidewalls, that's probably a good pressure. More than one sixteenth is too little, and if all the chalk on the tread isn't gone, thats way too much pressure.

Other than those two methods, for a regular daily driver, I'd go with whatever tirerack says. Their WAG is as good as anyones.

Lastly, an IR pyrometer is really a good tool to have. Wondering if your AC is blowing ice cold air? It'll tell you. Want to know if your radiator is clogged? What temperature the thermostat opens up? If the vents in your house are blowing cold air? Disc brake temps, catalytic converter temps, how well the oil cooler works, whether the coffee from your Kuerig is really 190 degrees, if your steak is hot, which of your girlfriends is truly hotter, etc.

bcook201

Andrew,
I find that 40 psi all around works for me. It will absolutely extend the life on your tires. The tire rack guys always go lower, because you will burn them up faster and buy new tires quicker. FYI, typically a Bridgestone/Firestone store will match the price on TireRack and give you the warranty along with including the Mounting and Balance. Make sure you rebalance after about 2500-3000 miles on your new tires. The passenger rear will always wear out first due to the transmission. Happy Driving

Andrew-NY

I appreciate your comment about Tirerack wanting us to buy more tires. I'm not sure If I believe your theory, but it makes sense.

If your theory is correct, then why does MB also recommend early 30s psi? I don't think Mercedes cares if we buy more tires from Tirerack unless of course they're getting a commission from Tirerack, which I highly doubt. If 40psi is best, then don't you think MB would recommend 40 insted of 30/33?

BlownV8

Mercedes recommends less pressure for a smoother ride.

Andrew-NY

I think I found the perfect pressure for our cars: 38F/35R. Seems great at this pressure.

techbike

When I ran 19"s, I had to have 40 ft/lbs or else, the rims just get whacked. I went through 2 sets of rims when I ran 34 lbs. Especially in New York!

Hey, I have barely used Yoko AVS 19s if you're interested. EM me.

Andrew-NY

I thought the higher pressure (40+) would be more harmful to your rims. Am I wrong?

techbike

Yup, since the sidewall of the large diameter tires are so small, there is barely enough rubber to absorb shocks that could bend the rims. So, you must inflate the tire higher so that when you do hit a pothole, the sidewall doesn't give. Also, the width requires a higher pressure to properly shape the footprint. Lower pressures, although more comfortable, will allow the middle of the tread to cave in, resulting in more wear to the outside edges. Alignment is critical when you switch to low-profile rims and tires. Toe and camber must be spot on.

Andrew-NY

I still feel that 40+ all around is too much. I think my car drives nice with 38f/35r.

techbike

Try it if you like it.

All I can say is, I just put on my 2nd set of rear tires (Conti Sport Contact 2s) and the old ones wore pretty evenly at 40 psi, and the AMG rims were perfectly round.

Enjoy!