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Junghole
Junghole SuperDork
10/13/21 4:23 p.m.

So I've got my nice new 2020 GMC express van. Thing only has about 18,000 miles on it. The problem is the tire pressure light comes on, and it tells me the rear tires are at 60 psi. Keep in mind, when I got this van all four tires were inflated to 80 psi. Which I deemed absolutely ludicrous.

When I took it down to 70 psi the tire pressure light came on. I have done the tire monitor re-learn from the dash display, and that has not fixed anything. Right now I am leaving the tires at 60 psi, but I am wondering if even that is too much.

The sidewalls on the tires say that 80 psi is the max. I'm not sure what hooligan put them at 80 psi, but I'm sure it was to keep the tire pressure light from coming on. So is this normal? I don't think I have ever inflated a tire beyond 45 psi. 

BoxheadTim
BoxheadTim MegaDork
10/13/21 4:26 p.m.

What does the sticker on the door jamb say? That's what I'd start at. You generally don't want to inflate tires that close to their max psi rating unless that's what the manufacturer calls for. But if the sidewall says 80psi and you put 80psi cold in there, you may well end up with higher pressure once the tire is warmed up.

That said, I think the door sticker on my F250 calls for something like 80psi on the rears, but that's fully loaded.

David S. Wallens
David S. Wallens Editorial Director
10/13/21 4:29 p.m.

A second to check the sticker on the door jamb. 

Junghole
Junghole SuperDork
10/13/21 4:33 p.m.

Interesting. I checked the door jam. It is 80 psi cold on the rears and 50 psi cold in the front. So what do you do when the tire manufacturer says 80 psi is the max? I'm pretty sure these are the factory tires!

codrus (Forum Supporter)
codrus (Forum Supporter) PowerDork
10/13/21 4:34 p.m.
BoxheadTim said:

What does the sticker on the door jamb say? That's what I'd start at. You generally don't want to inflate tires that close to their max psi rating unless that's what the manufacturer calls for. But if the sidewall says 80psi and you put 80psi cold in there, you may well end up with higher pressure once the tire is warmed up.

That said, I think the door sticker on my F250 calls for something like 80psi on the rears, but that's fully loaded.

I believe sidewall "max pressure" is for cold, they leave room for it to heat up the expected amount during normal street use.

Light truck tires are designed to work at substantially higher pressures than normal passenger car tires, 50-80 psi is not unusual.  Assuming that the tires on the van are the same spec as the original ones then I would go with what the door jamb sticker says.  If someone has replaced LT tires with P tires then that may be a different story.

 

MrFancypants
MrFancypants Reader
10/13/21 4:42 p.m.

132 psi

Junghole
Junghole SuperDork
10/13/21 4:45 p.m.

In reply to MrFancypants :

Lmfao. Well at least it won't have sidewall flex...

Streetwiseguy
Streetwiseguy MegaDork
10/13/21 5:07 p.m.

The sticker says 80, the light comes on below that.

Lawyers.

If you find a friendly intelligent dealer, they should be able to change the setting, but lawyers.

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
10/13/21 5:20 p.m.

The 80 psi max on the tire is max COLD.  The pressure is allowed to increase as the tire gets hotter, which helps reduce load on the sidewall, reducing heat.

If you get a lot of temperature rise, you have not enough pressure.

 

That said the pressures are assuming the vehicle is at a certain load.  If you are driving it empty, you could probably get away with 50psi.  the TPMS light being on is just the van complaining that it's a workhorse, not a moped.

L5wolvesf
L5wolvesf HalfDork
10/13/21 5:23 p.m.

1. On every tire made there is a maximum inflation number, for that (brand, model, size etc tire) cast into the tire. But that is only a max and not the recommended inflation for the vehicle it is on.

2. For a particular vehicle there is a sticker on the door indicating the recommended pressures for the size(s) listed.

3. Additional loads (hauling lumber, towing etc) will likely need to be compensated for with additional pressure. But refer to #1 above in that case.

Pete Gossett (Forum Supporter)
Pete Gossett (Forum Supporter) MegaDork
10/13/21 6:01 p.m.

In reply to Junghole :

If the tires say 80 psi max cold, air them up to 80 psi & don't worry about their hot temps. 

I just encountered this with my E450 RV when I discovered after driving it home the tires were quite a bit hotter than they should have been, even though they were all around 60psi. 

Ranger50
Ranger50 MegaDork
10/13/21 6:44 p.m.

Straight from 1965....

Cactus
Cactus HalfDork
10/13/21 7:04 p.m.

You can look up a load chart for your tire size. Each size has a recommended pressure for a certain load. Loading is dynamic, so I always overshoot. In general, you'll do more harm being under pressure than over.

Toyman01 + Sized and
Toyman01 + Sized and MegaDork
10/13/21 8:20 p.m.

The 6 tires on my RV run at 80 psi. The 6 tires on my F350 ran at 80 psi. The tires on my last E350 ran at 80 psi. 80 is pretty normal for an E-rated tire. Commercial trucks usually run between 95 and 105. They are designed to carry a load, not ride well. 

As was stated above, read the door sticker. Set the pressures to that. 

 

Antihero (Forum Supporter)
Antihero (Forum Supporter) PowerDork
10/13/21 8:36 p.m.

80psi is a lot but not really untoward with truck tires, they are assuming you are carrying a heavy load in the van.

 

You can probably get by with less if you aren't hauling but make sure you inflate them all the way up with a heavy load or else it will be bracing

Toyman01 + Sized and
Toyman01 + Sized and MegaDork
10/13/21 9:06 p.m.

Another fun one. When I last owned a road bike 30 years ago, those skinny little tires ran at 60 psi. 

Datsun310Guy
Datsun310Guy MegaDork
10/13/21 9:20 p.m.
Toyman01 + Sized and said:

Another fun one. When I last owned a road bike 30 years ago, those skinny little tires ran at 60 psi. 

I had the same bike and you had to constantly air them back up every few days.  

codrus (Forum Supporter)
codrus (Forum Supporter) PowerDork
10/13/21 10:43 p.m.
Antihero (Forum Supporter) said:

You can probably get by with less if you aren't hauling but make sure you inflate them all the way up with a heavy load or else it will be bracing

If you aren't hauling, then 80 psi will wear out the centers of your tires pretty quickly.  Big trucks don't make great single person commuters. :)

 

 

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
10/13/21 10:59 p.m.

In reply to codrus (Forum Supporter) :

While true, the front tires will also wear the shoulders and also get a really bad longitudinal (radial?) feathering from braking loads, so you need to cross-rotate the tires every 3000mi or so anyway...

 

confession:  Cross rotating tires would suck without a lift.  Also, I never rotate my tires, I swap winter for summer every six months and put the best on the front/examine tire wear and put the tires in such a place that they will smooth out any strange wear.  This is probably why I go through tires so much.

codrus (Forum Supporter)
codrus (Forum Supporter) PowerDork
10/13/21 11:18 p.m.
Pete. (l33t FS) said:

While true, the front tires will also wear the shoulders and also get a really bad longitudinal (radial?) feathering from braking loads, so you need to cross-rotate the tires every 3000mi or so anyway...

Neither of the two Duramaxes that I owned did anything nasty to the fronts, but AIUI they have a pretty different front end geometry to most 3/4 ton trucks.

And yeah, even same-side front-to-back rotation on a truck like that is a PITA.

KyAllroad
KyAllroad UltimaDork
10/14/21 7:01 a.m.
jgrewe
jgrewe HalfDork
10/14/21 9:13 a.m.

Something I've always wondered. I had a very experienced certified mechanic tell me the tire pressures on the door sticker were only correct for the OE tires and were for max load of the vehicle.  My Dodge Ram 2500 lists 50 front, 70 rear. When you consider the engine weighs over 1000lbs itself(Cummins) and the bed is empty most of the time there has to be better pressure to run out back when not hauling. I usually run 50 all the way around to keep the truck from riding like an ox cart and air up when its time for the truck to do some heavy work.

I saw a website years ago about trailer tire pressures that I can't find now.  Do manufacturers offer up the info on specific tires?

pirate
pirate Dork
10/14/21 9:34 a.m.

Just about every tire manufacturer has a website that includes a tire inflation chart/guide for every model tire the manufacture. This is especially true for truck tires. For truck tires they recommend or is good practice to have vehicle weighed front and rear axil and inflate for those weights per chart.  Just about any truck stop has a Cat Scales that is either has an operator or is automated.

AnthonyGS (Forum Supporter)
AnthonyGS (Forum Supporter) SuperDork
10/14/21 9:36 a.m.

In reply to Toyman01 + Sized and :

Try 100 psi now or even 110 in a skinny bike tire.  

ShinnyGroove (Forum Supporter)
ShinnyGroove (Forum Supporter) HalfDork
10/14/21 9:40 a.m.

Have we determined what tires are on the vehicle and whether they're the OE tires?  I'm guessing by the high pressure recommendations that they're LT tires rather than passenger tires.  If that's the case, you can air them down from the recommended pressures a bit when the van is not loaded to give you a little better ride quality.  Just be aware that LT tires actually have less load carrying capacity at equivalent pressures to passenger tires.  In other words, a passenger tire can carry it's max load around 36psi, while an LT tire can only carry a fraction of it's max load at that pressure.

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