Tire pressures

[rjgvt]

I brought my AT4 HD home last week and set the tire pressures to 60 psi for all 4 tires. Rode around the last few days. The bed is a little bouncy on our crappy roads but it is empty. Rides nice on the interstate. Getting an ARE cap put on this Friday. The cap and the rest of the stuff I put in the bed weighs around 450 lbs. 

 

Today I decided to reduce the tire pressures to 55 psi for all 4 tires. The DIC showed 56 psi. Went for a ride around the neighborhood and it read 57 psi when I got back. No TPMS sensor errors. Got out my Autel TS508 to read the placard tire pressures through the OBDII. Tire pressures for front and rear on the TS508 read -17 psi. I have the option to set them whatever I want but left as is. I have the tire pressures showing on the right side of the DIC all of the time. The MyGMC shows the recommended tire pressures at 59 psi / 69 psi. 

 

Not sure why the MyGMC page is different unless my Autel is not reading correctly through the OBDII. It's the first time I used it like that. I did read the sensors individually and they are reading correctly.

 

 

Edited January 23 by rjgvt

[Crazy Canuck]

Not sure if there is a question here or just a statement about how you run your tires?

[rjgvt]

Not a question on what pressures to run. Thought it was odd that I didn’t receive a TPMS error with the rear tire pressures at 56 psi and that the tire placard read -17 psi for both front and rear axles on my Autel TS508. I thought the tire placard on the Autel would read the same as tire placard on the door jamb label. I have read a post about others getting TPMS errors at 62 psi for rear tires. 

[Another JR]

My 2021 3500 has a max recommended rear tire pressure of 80 psi and the rear tpms alert comes on at 62 psi (although it didn’t alert when they recently dipped below that a little in recent sub-20F temperatures).  The 2500 from that year had a maximum recommended rear tire pressure of 70 psi and a lower alert pressure. I don’t know what it is, but I’d guess it’s about 53 psi.  
 

If you have the lighter weight gas engine and 450 lbs in/on the bed, with full fuel and a 200 lbs driver, your front axle weight is about 4500 lbs and your rear axle weight is about 3600.  This is based on weighing my truck and adjusting for the bed length difference and transmission difference. 

Edited January 24 by Another JR

[rjgvt]

Another JR,

 

Thanks for the info. Based on your info I could run 40 psi in the front and 35 psi in the rear. Curb weight is 7637 lbs. I figure that with 2 passengers + cab stuff is ~450 lbs + 450 lbs in/on bed + curb = 8537 lbs. We don’t have scales here but there are 2 CAT scales across the lake and will take a ride one day and weigh my truck. I don’t think I’d run less than 50 psi. I tow a boat during the summer, not sure of the tongue weight, maybe 200 to 300 lbs or so. Will probably be negligible.

[Another JR]

Yeah at highway speeds even when empty I’d stay at 50 or above. You have 20s so my experience with stock 18s doesn’t read across directly, but I run my fronts at around 52-54 and I have even wear. I run the rears just over the tpms alert level because I don’t have a tool to change the alert level. With my pop up slide in camper  fully loaded for travel at anout 1800 lbs my rear axle weight is at 4900.  I would run the rear at 55 to 57 if not for the alert. 

[Pryme]

9 hours ago, rjgvt said:

Another JR,

 

Thanks for the info. Based on your info I could run 40 psi in the front and 35 psi in the rear. Curb weight is 7637 lbs. I figure that with 2 passengers + cab stuff is ~450 lbs + 450 lbs in/on bed + curb = 8537 lbs. We don’t have scales here but there are 2 CAT scales across the lake and will take a ride one day and weigh my truck. I don’t think I’d run less than 50 psi. I tow a boat during the summer, not sure of the tongue weight, maybe 200 to 300 lbs or so. Will probably be negligible.

Why would you want to run a heavy duty pickup at the same psi I run my Corolla at? You must not need the capability of a heavy duty truck if you’re prepared to run 35-40psi which btw is unsafe for a 7-8k pound pickup 

[rjgvt]

I’m not going to run the tires at 40 psi. Currently at 55 psi and wouldn’t run them less than 50 psi. I didn’t need an HD truck but didn’t want some of the features on the new 1500’s. Difference between a 1500 AT4 w/6.2 and 6.5’ bed was ~$2k less than my AT4 HD. So my kids get a little less inheritance! 

[Crazy Canuck]

On 1/23/2024 at 9:37 PM, rjgvt said:

Not a question on what pressures to run. Thought it was odd that I didn’t receive a TPMS error with the rear tire pressures at 56 psi and that the tire placard read -17 psi for both front and rear axles on my Autel TS508. I thought the tire placard on the Autel would read the same as tire placard on the door jamb label. I have read a post about others getting TPMS errors at 62 psi for rear tires. 

 

No worries.  I run my tires at what the placard on the door tells me (60 front/70 rear) so am not sure when the alarm is triggered although I did have a leak in my '22 that set it off.   That way if I ever want to tow/haul something, I am safe within the capacities of the truck.  I also figure it is a truck so expect it to ride like one which is actually quite a bit better than my '19 F150 I had rode on the stock 22s.  Unless I am in sand or something, I couldn't see airing down for any other reason.

[ManyCamaroz]

I've always been leery of running too far below the manufactures recommended pressure. Firestone claimed the massive tire failures in the nineties was attributed to running underinflated tires at high speeds and was the cause of over 200 deaths. It wasn't the root cause but was deemed a contributing factor. 

[Pryme]

42 minutes ago, ManyCamaroz said:

I've always been leery of running too far below the manufactures recommended pressure. Firestone claimed the massive tire failures in the nineties was attributed to running underinflated tires at high speeds and was the cause of over 200 deaths. It wasn't the root cause but was deemed a contributing factor. 

That went into the early 2000’s too. I had a 2k ranger with firestones on it and in 2001 I had a business card stuck under my wiper for a tire shop saying I can come in for new free tires. So I went in and got a new set for free. 

[Jettech1]

Anything below 55psi sends me a message.  BUT I have to ask this.  I run my tires 60 in the front and 57 in the rear unloaded mainly for ride quality.  Why would GM want the pressures to be higher in the rear and not in the front?  I weighed my truck empty, it was 4480 in the front and 3380 on the rear axle.  To me and for comfort reasons unloaded I run a higher pressure on the front axle and a lower pressure on the rear axle due to the weights.  Unloaded I'm talking about.  When we tow our camper I put them all at 75psi.  So I don't get why a higher pressure on the rear tires over the front tires is recommended.  Please explain this to me.

[Pryme]

54 minutes ago, Jettech1 said:

Anything below 55psi sends me a message.  BUT I have to ask this.  I run my tires 60 in the front and 57 in the rear unloaded mainly for ride quality.  Why would GM want the pressures to be higher in the rear and not in the front?  I weighed my truck empty, it was 4480 in the front and 3380 on the rear axle.  To me and for comfort reasons unloaded I run a higher pressure on the front axle and a lower pressure on the rear axle due to the weights.  Unloaded I'm talking about.  When we tow our camper I put them all at 75psi.  So I don't get why a higher pressure on the rear tires over the front tires is recommended.  Please explain this to me.

Because when you’re towing you have more weight on the rear. It also probably has to do with proper steering control. 

[Another JR]

GM doesn’t actually give us recommendations for how much to reduce pressure at lower weights than the GAWRs, and I suspect they don’t want to take on the liability of providing that advice.  
 

I don’t think GM necessarily “wants” the tire pressure to be higher in the rear when the rear axle weight is way below the front axle weight. I believe the OEM alert pressures for the TPMS are simply some fixed percentage below the maximum tire pressure recommended based on the axle weight rating and whatever handling factors went into setting the maximum pressures on the door jamb sticker. They only want to pay for a fixed alert level, and they want to give you a meaningful alert level for when you are maxed out (probably driven by DOT regulations).  Their 80 psi recommendation at 7200 RGAWR and the associated 63 psi alert level (and 70 psi and 55 alert level for the 2500) don’t account for the fact that, when empty, the rear axle weight is only about 3350 lbs.  

 

Towing a medium or heavy trailer is a whole different set of concerns, and you want maximum lateral stiffness to avoid sway regardless of rear axle weight, so “good on ya” JT for running at the max rear pressure when towing. 

 

 

 

 

[rdonarski]

I remember the 3 hour trip home on 2 lane roads when I 1st picked up my truck. Butt was sore. Thought maybe I'd made a mistake buying it. Bought a cushion to sit on. Lowered the tire pressures as much as possible. Now I don't even notice. No longer use the cushion, Biggest problem I have now is if I'm not using cruise control, I'm always going faster than I think I am. Going 80 feels like 50. I do pull a trailer with a skid steer or tractor at times. My pressures are set about 5 lbs above minimum. Haven't noticed any swaying problems pulling the trailer. Overall happy with everything.