ivrier

32 psi is the recommended tire pressure for daily driving. There is nothing in the manual indicating the tire pressure needed for trailer towing? Any experienced towers or is it haulers have any idea what the pressures should be at the front and/or rear tires?

thanks in advance.

BeanCounter

32 is the recommended psi for average/light loads. I am not sure of the pressures by tire/wheel size but I have the 19 inch wheels and the fully loaded pressures are 38 in the rear and 32 in the front. Check on the inside of the gas cap door for yours but my guess is that they would be similar. My personal preference is to go a little above the recommended tire pressures (a pound or two). Whatever your preference, do not run them underinflated because as that can lead to higher operating temperatures and potential problems.

Nevada Jack

I think the recommended PSI on the 550 (21 inch) is 35 all around. I recently had the car serviced and checked the pressure and it was 35 in the rear and 36.5 in the front. I thought maybe when I checked the first front that they had over inflated it, but the other tire was exactly the same. The car rides great at these pressures.

Danno4x4

If you check behind the fuel filler door, it lists loaded and unloaded tire pressures... You would want to pick the loaded tire pressure...

ivrier

Thanks for the reply guys. I have running at 32 psi on a loaded vehicle and though the GL runs well, I get some veering at speeds of 80 mph. I will adust it to 38 at the rear as indicated.

Danno4x4

What are you towing... I hate to say it, but assuming that you are towing anything more than 1000 lbs, you really don't want to be exceeding about 65 MPH.

The GL was designed to be a well handling SUV that fits the family and can also tow when you need it to...

but it was not designed as a tow vehicle that is also well handling and can fit the family.

The big 1-Ton plus long wheel base trucks do a much better job that, but their practicality is limited in the driving performance and people hauling categories.

In other words, most SUVs compromise a few things in the towing department.

For the sake of your family and those you share the road with, please, slow down a bit.

MKW

32/38 is what I use for my '08 GL 450 with OEM 19" Contis. I started at 32/35 , but after returning from first trip to Tahoe last fall with 4 people and load of luggage , I noticed the edge of rear tires' sidewalls where partly whitish ( meaning they were "underinflated" for conditions of cold and altitude ) and not just running on the tread . Inflated them to 38 and never saw that again rest of the winter. Now I just keep that setting year round because as you know , with summer trips and full load you want more rear pressure to keep from overheating the tire due to sidewall squirm .

ivrier

I am towing a 5600 lb, 22 foot trailer. It is equipped with an Equal-i-zer which avoids the swaying motion of the vehicle. I've searched this forum on towing experiences and people have generally been quite satisfied with the performance of the GL. I definitely would not go beyond 65 mph with a trailer. I just cannot understand those who risk the lives of their family and others driving an excess of 75 while hauling trailers.

tnguyenmdc

I just upgraded to 20" tires and wheels from the 19" that came with the 450. My tires installer told me to run 40 PSI on all 4 tires, which is a little rough for me. Could you please confirm for me what's recommended on the 550? Also, what size tires are on it? Thank you.

Nevada Jack

The tires are 295/40 R 21's. With 3 passengers recommended pressure is 33/33. Full load recommended is 35/42. As indicated I have found that 36.5/35 works well for me in ride and handling.

tnguyenmdc

Just to confirm. So that's 36.5 in front and 35 in rear, correct? That's perfect, because my tires are almost the same. 295/45 R 20. Thanks again...

lkchris

All well and good for the "stone age" vehicles from American manufacturers.

Mercedes is a bit different I think.

ESP will control trailer sway within reason, too.

StevethePilot

You're kidding, right? I mean, what is the speed rating for the trialer's tires is the first question. Next of course is what's the new stopping distance with the trailer (with or without brakes on the trailer). And last, the huge amount of wind turbulence that will affect the trailer, both from the GL and from vehicles it passes will probably be beyond the ability of the stability control to handle. It's stability control, not magic. It's still bound by the laws of physics.

Stumblefoot

You know physics too?

You truly are a pilot (jack) of all trades!

BeanCounter

Danno's post is spot on. Doing 80 while towing anything is just not a great idea.

Nevada Jack

Correct on the front and rear pressures...

StevethePilot

Jack(a**) of all trades, master of none. Dat's me.