Correct cold PSI for 33's?

[Ralph]

Can someone tell me the correct tire pressure for the 33" tires?

[Ralph]

Can someone tell me the correct tire pressure for the 33" tires?

[ketcat]

Check out the sticker on the drivers B pillar. I think it says 35psi.

[NEOCON1]

a few of us run at 38-40 psi on road for milage benefits and it keeps your TPM's quiet

[fourfourto]

I keep mine at 35 ,every 6 to 8 weeks TPM goes on and I check and top off to 35.

[ketcat]

I guess I could have told you I run 32psi on the road and 20ish off road. The TPM in my H3 has not worked from day one and the SVC TPM light is always on so I am use to the light being on.

[Ralph]

I went with 38 PSI for a 460 mi trip and the MPG was a decent 19 MPG. The ride felt about the same as when I had 34 cold. The tires look better (bigger) as well.

[f5fstop]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by ketcat:
I guess I could have told you I run 32psi on the road and 20ish off road. The TPM in my H3 has not worked from day one and the SVC TPM light is always on so I am use to the light being on. </div></BLOCKQUOTE>

Running low air pressures in your tires does not mean the TPM is NOT working. It is designed to come on and warn you of low air pressure in a tire (or tires).

[ketcat]

F5fstop

I guess I was not clear with I said:

“I guess I could have told you I run 32psi on the road and 20ish off road. The TPM in my H3 has not worked from day one and the SVC TPM light is always on so I am use to the light being on.”

So let me explain. When I pick up my H3 at the dealer 6-14-05 SVC TPM was displayed on the dash. At the time of delivery Edmark stated that they thought it was a bad tire pressure sensor but that none were in stock. I had come from Phoenix to take delivery and needed to get back home so I told them I would just have it taken care of later. Since that time the H3 has been to the dealer 8 times to repair the problem (and a bunch of others) to no avail. It is going back in on Monday for a BCM which is what they think is causing the problem.

As for the TPM working or not. It is not working at this time. When it was delivered it in fact did work because it would display low tire when I ran low air pressure and SVC TPM would turn on and off intermittently. After the third visit to the dealer the TPM stopped working and now it just displays SVC TPM intermittently (mostly on the freeway). I am familiar with and have performed the reset procedure and have a TECH II and CANDI module at work which I have used to reset the system on numerous occasions.

Sorry if my statement caused you or anyone to think that I was saying the system didn’t work because SVC TPM was displayed when I ran low pressures. That is what it’s designed to do, inform the driver of the vehicle that they have a low tire to supposedly prevent rollovers which in my experience is a driver issue not a fault in vehicle design. Well that’s a story for another day.

Thanks for helping me clear that up.

[ketcat]

F5fstop

Based on your posts you obviously have a bunch of automotive / Hummer experience. Have you tried changing the tire size setting using the TECH II. There are bunch of different sizes and pressure which if it works would allow you to run lower pressure with out getting a low tire warning. Does changing the tire size change the speedometer calibration? I have been wanting to test it but am waiting for the TPM to work correctly. I know GM wouldn’t want this done and maybe the answer needs to be the same as the locker over ride question.

[f5fstop]

ketcat, now I understand. If you want the TPM system to work properly, I would suggest a different dealer to repair the issue. The system is actually quite simple, and a GOOD tech can repair the problem.
The larger tires will reflect set a message, if pressures are low, due to the higher volume of air inside the tire.
However, the system only uses five sensors (spare not recognized until on a corner), the BCM and the IPC to display the message. Most of the problems are due to a actual low pressures, or pressures variation between a warm day and a very cold night. In addition, dealers are being hit with people who never check their air pressures, so from warm weather to cold weather the system will go on since there is an approx. 1 psi drop for every 10 degrees.
The people who visit this site are smart enough to check their pressures, but the dealers don't know that. Some dealers automatically assume the person is one of those who does not check pressures.
I would demand the dealer to explain why they cannot fix the system, since for those on this site who say the system does not operate, there are hundreds more for each one who does not have a problem. Last resort, call the customer assistance center and complain. If it was happening to me, I would be furious too.
One bad sensor, could be the problem, a bad BCM could also cause a problem, but less likely.
As for programming the system, the dealer, nor I, can program in different parameters. This system is required by Federal Law, and GM will not allow reprogramming by a dealer, and even if they could, most dealers will not accept liability to reprogram in a different setting. (All vehicles will have this system by fall of next year, the Feds allowed them to be phased in over a period of time, and GM, like all manufacturers is installing the system on all new vehicle first, then redesign them on existing vehicles to meet the law.)
I do not believe there is a tire size bit to flip via the Tech 2. I guess I should take a look someday to verify this, but I have been told there is not a way to reprogram for a different size tire.
However, a 1" tire size increase between the 32 stock and the 33 off-road package, will not show that much on the speedo or odo, and keeps the speed and odometer within Federal requirements.

Again, my suggestion would be to get a dealer to fix the system. We all will have to live with the message when off-roading with reduced tires. Someone on this site (I believe it was Paragon) made a great recommendation to program the BCM to turn off the TPM system if the vehicle was in 4-LO Lock. I made this suggestion to someone at GM, and it didn't go over very well. I guess someone at GM (did I say attorney ), has reason to assume that there are idiots out there who would actually drive at a constant 40 mph, on a very hot day, and blow a tire. I hate to add, that they are probably correct in this assumption. (Actually met one that would be a candidate last year in Utah. Thought he could go where I had just been with an Chevy (ALL-WHEEL drive) Equinox with low ground clearance. I should have charged him for pulling him off the rocks, but just made him attach the tow rope to his vehicle.

As for the locker override...well, if a person understands electrical schematics, there might possibly be a way to override the locker. But this does not mean I know, or even imply that it can be done, or should be done, or has been done, etc.

[ketcat]

F5fstop

I agree with you about the dealer. I think they are the issue with my TPM and several other reoccurring issues with the H3. Unfortunately for business reasons I can’t push them or go to GM like I could if it were another business. I would explain my reason but this is not the forum so maybe we will meet up on a run someday and I can explain.

On the temperature variation issue. Will that cause the system to display SVC TPM or Low Tire? I know mine has a issue unrelated to temp but a co workers H3 is having an intermittent issue. I’m thinking he does not check the tires and if he is running close to min pressure and the temp change could cause SVC TPM to be displayed then he might just need to check his tires more often.

Thanks again appreciate the advise.

[f5fstop]

yes, temp variation will cause the system to post a message in the DIC intermittently.
It even happened to me, when the temp dropped considerably.
I check my pressures every two weeks, but in the late fall, we had a considerable drop one morning, and the message came on, the chime chimed, but after driving a few miles, the message went out.
The vehicle sat for over eight hours and the temps dropped to the 20s, so when I started the tires were below the minimum set point, and the display lit up. After driving about two miles the message went out, due to the tires warming and the air pressure going up just enough to set off the TPM warning.
Two days later on Saturday AM, before the H3 was driven, I checked the pressures and they were all at 33 psi, but it was in the 40s that day.
So, I have to assume that that morning the system went off, they were at around 29 psi.
I adjusted the pressures, and so far, with checks every two weeks, no more messages.

I believe that GM has issued a bulletin in regard to some porosity problems with some aluminum rims, which is quite common with aluminum rims. However, this would be noticed by someone who is constantly checking their pressures and notes that one wheel assembly drops more pressure than the other wheels, and this would indicate there is a problem with the tire or the porosity of the rim. Easy fix to repair the porosity in the rim since it is at the edge.
My Vette had this problem, and it is sealed by the technician, and after almost three years, never had a problem again.

Now, even if you work or do work for GM, it is not impossible to go to another dealer. Post on this site for another dealer in Phoenix that someone on this forum can recommend. (I have no idea how many dealers there are in your area.)
I know many GM employees who have registered complaints with the assistance center. I did on my Caterra a few years ago, and got it finally fixed correctly.

I can tell you this, there are two things that the dealers are really upset about with new GM vehicles. One, the GM oil change light, took away a lot of their 3000 mile oil change business. Two, the tire air pressure monitoring system.
They are flooded with people who never check their tire pressures, flooding them in the fall with the TPM message, and all that is wrong is the tires are now running low due to the owners not checking or having checked their tire pressure. Since this is not technically a warranty issue, then cannot submit a warranty claim; therefore, they are covering this cost themselves.

Many have their pressures checked at the local oil change shop, and this is one problem. The person drives to the oil change shop, the tires are HOT, the guy doing the checks looks at the tire pressure label, sees 35 psi, and reduces the tire pressures in all tires to 35 psi. (The worse case scenario is this guy thinks all tire pressures should be at 30 psi because the first time he check tires, that was what the first label he looked at stated.)
Tire pressures should only be checked on a tire that has not been driven for at least three hours.
Tires can gain three to four psi while driving on a hot day. (On my Vette, I would gain 4 psi on a hot day in TN. The Vette displayed the pressure in each tire on the DIC.)
So, the guy just reduced the pressures from (let's say) 38 psi to 35 psi; however, after sitting a few hours, the pressure in the tires drops to 32 psi. Temps drop overnight by thirty degrees and now the tires are at 29 psi at startup...system will display a TPM message.
Another problem people to when checking their tire pressures is to check on a day with the sun shining on one side of the vehicle. Direct sunlight can cause the tires in the sunlight to be about two psi higher than those in the shade. So, the person balances out the tires, and those in the sunlight will be lower when the sun disappears.

[DarthKarl]

Great info f5. Thanks.

This should be mandatory reading for everyone who has ever seen a TPM light come on. (including me)