Tire pressure
 

What are you guys running for tire pressures?

The gas cap door says under normal load it should be front 33 and rear 33 but on maximum load it should be front 35 and rear 39.

The driver door jam only shows front 35 and rear 39.

So my question is, what is considered normal load and maximum load?

What psi are people running for their GLK? I'm thinking about 37psi all around.

1) How much gas is in the tank?
2) How much luggage?
3) How many passengers?
4) A cup or DDD cup on passengers?


Get the point!

:D

Without getting into complex calculation of MB guide's spec, normal driving would be 4 small to average persons with light baggage. Thus, your use of 37 psi is high and firm drive for 1 driver specially with East coast summer temperatures.

I keep 35 all around. It's a nice firm ride..:zoom:

yep 33-35 here also

I use 33 all around.

decided to run 35 psi all around.

I am running 35/39 all the time.

I have the factory option 20" Pirelli Scorpion Zeros on it, which have a shorter / stiffer sidewall than the stock non-option tires.

I tried 35 all around, as well as 33 all around. I would have thought equal pressures would have made the handling better, but more in the rear seems better even w/o hauling loads.

(Note: I have a GLK dealer loaner with almost no options, and the handling is immensely improved by the Pirellis. Highly recommended to get better tires, do the plus 1 thing.)

interesting... i'll have to play around with it and see if i can feel a difference. maybe i'll try front 35 and rear 37 for tomorrow. good to have an air machine at home.

Hi gsrjc,

Did you try the tire pressure. I have 20'' rims with factory installed tires. Currently I am keeping 33psi in all tires. I was wondering if I need to change it to 35/39

35/39 will make the lawyers happy because this soft setting in the front tires, high in the rear tires, promotes understeer which is most comfortable and safe for the average driver. But if you want a little crisper handling with less understeer ("push" in NASCAR terms), I suggest using the same front and rear, say 37 or so. I'm thinking that with 35/39, you'll find the outside edge of the front and the center of the rear tires will wear prematurely.

If you push it in NASCAR terms you'll be wrapped around the pole regardless of your tire pressure.

Lawyer don't give a crap about understeer. If anything, they would care about tire blowout. If your car is loaded and you drive at highway speeds your tires will have more tire-flex which can lead to a blowout. With increased tire pressure, tire is firmer and produces less tire flex.

That's also why it's 35 front and 39 rear. Most of the weight in a loaded car will be in the back, while front will be only slightly heavier.

Actually based on the 4 matic's ratio front to rear, I find 36F and 40R in colder climates and 33F 37R (before being driven) on hot summer days... to be the best for me but our GLK has the 20" Dunlops, not the Pirelli's.

I believe glkowner1 was considering 35/39 for normal load as stated on the door jamb which he mentions in his original post.

36/40 sounds OK for a full load (although I'd opt for 40/40), but with a lower front pressure settings for a "normal" load, one can enjoy "roll and scrub" -- scrubbing speed off with the front tires in turns (rather than with the brakes; "slow in fast out.")

But these settings will keep the corporate lawyers happy. They don't care about tire wear and don't want to be sued when suspension design and recommended tire pressure result in oversteer ("loose" in NASCAR terms) which is troublesome for the average driver.

OOOh! '65 GOAT. Trade my MB for that.:bow:

Tire Pressure
 

I live in Florida, I have the Pirelli Scorpions on 20 inch wheels with "NITRO" fill, I found 33PSI to sluggish, I had them put the PSI at 35 and in the heat they seem to expand to 37-38. The ride is much firmer and seems to handle better, I have 16000 miles and the dealer told me I will need new tires at around 18500-19000..The center seems to have warn down more than the sidewalls...MY bad..I like the stiffer ride, I have some RENNTECH work done and the car drags at lower PSI. :zoom:

Question..For those of you that may have had to replace their tires, did you buy thm from the dealer or??? tx...Dan:nix:

Bought my tires from my tire guy see post above. I have about 32K on my tires and still have some life in them. My tire guy is holding my new tires till later this year befo0re I put the new ones on.

I checked my tire pressure and they were all at 27psi. I filled them all to 35psi. I told the wife to check them, I guess she doesn't want to get her fingers dirty. She hasn't chech tire pressure since new almost 2 years ago. I think she needs to be punished now.

Dirty fingers? I check mine through the on board computer.

How about not blaming your wife and getting your hands dirty...no excuse to avoid doing routine maintenance. Read your manual and see how to check the air pressure.

Canadian version doesn't have it. It monitors tire pressure by rpm differential between tires. The down size is the low sensitivity. I lot low pressure warning last time, only when it dropped to below 25psi.

That's interesting. Mine probably is the same since you have to drive a bit for it to read. So it's calculating pressure by comparing tire rpm vs speed? That doesn't make sense. So what is it reading?:confused:

Yualfred and 420tee, are you saying that you don't have tire pressure readings on your display?...service, down arrow, tire pressure...

Direct Systems
attach a pressure sensor/transmitter to the vehicle’s wheels. An in-vehicle receiver warns the driver if the pressure in any tire falls below a predetermined level. Direct systems are typically more accurate and reliable and most are able to indicate which tire is underinflated.



Indirect Systems
use the vehicle’s antilock braking system’s wheel speed sensors to compare the rotational speed of one tire versus the others. If a tire is low on pressure, it will roll at a different number of revolutions per mile than the other three and alert the vehicle’s onboard computer. Indirect systems (except for the TPMS on several 2009+ Audi models and 2010+ Volkswagen models) are unable to generate accurate readings in cases where all four tires are losing pressure at the same rate, such as the effects of time and temperature.

The GLK is hers.........I drive it 3 times a month when I fill up the gas tank for her. If she doesn't learn to take care of her car. I'll just buy her a Skoda next time :)

Good info. Mine is indirect for sure (Canadian version). It doesn't indicate which tire, just a general message (Check tire pressure).