Pressure Way Off Towing With One Tire

Larry McNeil

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No trailer sensors. I do need to get some before heading down to Sebring next week.



I've noticed that as well. They the sunny side is always more but I still can't account for the extra pressure in the one tire. I took the truck to Costco and they found a very small pinhole on that tire between the sidewall and the tread that couldn't be fixed. Could it be from too much pressure when it was heating up or a defect?

Since I'm towing the Camaro down to Sebring next week, I swapped my OEM 22" Hankook's over to some new 18" Goodyear's from an F150 takeoff. I'll set them to the max pressure of 51 PSI and do a 20 mile test run with the Camaro on the trailer before I leave to see if there's a change.

Is there a possiblity that the Expedition's stability assist is kicking in too much and overheating that corner?
I think we may be allowing ourselves to chase a squirrel here. OP states his drivers side rear PRESSURE ‘jumps up’ 20 pounds when he connects his trailer. We seem to be primarily addressing Temperature. TechDude - does it really ‘jump up’ as in coincident with connection, or within a couple miles towing, or does it only become evident after an hour or more towing? If it’s essentially immediate, then clearly it’s an electrical gremlin of some sort. Also, is the pressure increased on some TPMS (OEM or aftermarket) install, or is it up by manual pressure gauge? Just things to consider before going after temperature, which does not seem likely in this case. (Or, is the tire and wheel WAY hot after towing?

The only other contributor I have ever heard is something I have not confirmed- but I do have a HOTTER tire and wheel on my 17 on the drivers rear after towing. Have been told to expect it because that wheel is the ‘power wheel’ due to some conditions I’ve not sorted out yet. I guess possibilities would include the crowned roads we drive on, or even ‘god said so’, but my tire temps on drivers side rear are consistently 10 - 20 degrees higher on that wheel when towing. Don’t get it, don’t understand it, but it seems real.
Ooops, sorry, I seem have have dumped another possible squirrel into the mix!
My reasoning was sorta like this - IF the ‘power wheel’ thing is true, then more power gets transferred to ground thru that wheel, and then IF the trailer is pulling especially hard, then OP could be seeing higher TEMPS on that wheel, but I would not expect the PRESSURE transients he is seeing? Just my 2 cents!
 
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techdude99

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I would say dragging e-brake, but it doesnt seem to happen when unladen. Try the fender drop measurement. If there's substantially more load on one side that would be the first clue.

The cargo in the Expedition had about 200lbs more on the impacted side. Didn't notice any droop last time but will check when I load it up this week.

Tire pressure will increase/decrease by 1 psi for every 8 to 10 deg F in temperature change. The OP’s saying 20 deg F change, so that would mean a 160 to 200 deg F change in temperature and that is something that would be noticed just walking by. Is the pressure measured from a gauge or the monitor in the vehicle?

I verified the TPMS with an Accutire gauge and it lined up with each corner.

Would check the tire pressure with a gauge when you are getting the high reading, tpms could be going out.

Verified.

Certainly Very Strange, especially because of the one side only.
Does this happen when the unloaded trailer is connected or only when the trailer with the car is connected and you drive for awhile?
I assume you are testing with a known accurate tire pressure gauge and not relying on TPS for info.
With the trailer connected, have you verified that the rear wheels of the truck and all trailer wheels spin freely by jacking the back of the truck and each side of the trailer?
You mentioned installing 18" wheels with different tires, does this still occur with this different rear wheel / tire combo (assuming with different TPS)?

I haven't verified free spinning wheels with the truck and trailer but I can give it a shot.

Looks like some really bad weather rolling in over the next couple of days so this is going to be unpleasant.
 

JamaicaJoe

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I had a problem with my 2001 right rear caliper locking up. Initially we thought it was the E Brake and so that was serviced. It got worse until the axle seal failed and smoke poured out. An IR thermometer will tell you quickly that a wheel is overheating. Heck, my nose and just walking by the wheel I could feel the heat. I replaced both rear calipers and ALL of the rubber brake lines. Problem never came back.

If it isn't a problem with the hub overheating, you might check to see if the tire has a lot of water (condensation) from the fill air hose. Water turns to steam and then you have volume displaced.
 
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techdude99

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I think we may be allowing ourselves to chase a squirrel here. OP states his drivers side rear PRESSURE ‘jumps up’ 20 pounds when he connects his trailer. We seem to be primarily addressing Temperature. TechDude - does it really ‘jump up’ as in coincident with connection, or within a couple miles towing, or does it only become evident after an hour or more towing? If it’s essentially immediate, then clearly it’s an electrical gremlin of some sort. Also, is the pressure increased on some TPMS (OEM or aftermarket) install, or is it up by manual pressure gauge? Just things to consider before going after temperature, which does not seem likely in this case. (Or, is the tire and wheel WAY hot after towing?

The only other contributor I have ever heard is something I have not confirmed- but I do have a HOTTER tire and wheel on my 17 on the drivers rear after towing. Have been told to expect it because that wheel is the ‘power wheel’ due to some conditions I’ve not sorted out yet. I guess possibilities would include the crowned roads we drive on, or even ‘god said so’, but my tire temps on drivers side rear are consistently 10 - 20 degrees higher on that wheel when towing. Don’t get it, don’t understand it, but it seems real.
Ooops, sorry, I seem have have dumped another possible squirrel into the mix!
My reasoning was sorta like this - IF the ‘power wheel’ thing is true, then more power gets transferred to ground thru that wheel, and then IF the trailer is pulling especially hard, then OP could be seeing higher TEMPS on that wheel, but I would not expect the PRESSURE transients he is seeing? Just my 2 cents!
The temperature increases during laden towing after an hour. TPMS reports same temperature as Accutire gauge.

I had a problem with my 2001 right rear caliper locking up. Initially we thought it was the E Brake and so that was serviced. It got worse until the axle seal failed and smoke poured out. An IR thermometer will tell you quickly that a wheel is overheating. Heck, my nose and just walking by the wheel I could feel the heat. I replaced both rear calipers and ALL of the rubber brake lines. Problem never came back.

If it isn't a problem with the hub overheating, you might check to see if the tire has a lot of water (condensation) from the fill air hose. Water turns to steam and then you have volume displaced.
That's interesting. I had Costco do a Nitro fill on the 22" tires before the last trip. The current 19" tires are filled from my air compressor that does have condensation. I may stop by Costco before I leave.

I'll look at the calipers, too
 

Utah Driver

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I thought the diag was fairly obvious in the first couple of sentences. Thirty nine psi while towing the weight and cargo you described is an under inflated tire. You want max pressure cold as per side wall placard on your tire when towing. Also, if you are towing heavy you want light truck tires. If you have p tires under inflated they are going to get hot. The power wheel thing is real. I'm a diesel mechanic and even on semi trucks the power goes to one wheel. Cheers
 

JamaicaJoe

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The temperature increases during laden towing after an hour. TPMS reports same temperature as Accutire gauge.


That's interesting. I had Costco do a Nitro fill on the 22" tires before the last trip. The current 19" tires are filled from my air compressor that does have condensation. I may stop by Costco before I leave.

I'll look at the calipers, too
Costco may just purge the air and backfill the N.

Dismount that tire and pull the valve core with it face down to try and force the water out. My compressor draws in a lot of moisture and I purge it after every use to keep the tank from rusting up.
 
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techdude99

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Costco may just purge the air and backfill the N.

Dismount that tire and pull the valve core with it face down to try and force the water out. My compressor draws in a lot of moisture and I purge it after every use to keep the tank from rusting up.

I'll ask them.

I thought the diag was fairly obvious in the first couple of sentences. Thirty nine psi while towing the weight and cargo you described is an under inflated tire. You want max pressure cold as per side wall placard on your tire when towing. Also, if you are towing heavy you want light truck tires. If you have p tires under inflated they are going to get hot. The power wheel thing is real. I'm a diesel mechanic and even on semi trucks the power goes to one wheel. Cheers

I don't tow often and this has been a very informative thread. The specs for the tires are attached. Cargo in the back Expedition varies between 200-400 lbs, trailer is 1400 lbs, and the car is 3800 lbs. I'm using a Weight-safe adjustable hitch.

Do I need different tires with this configuration?

Thank you.

1674660796721.png

1674661049910.png
 

JasonH

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What are the GVWR and GCWR on your door sticker? Your trailer tongue should be between 520 and 780. Your tires should be ok, but that max load of 2601 is at 51 psi. If you're running less tire pressure than that, you may have issues when operating fully loaded. You can upgrade to a "D" or "E" tire for a higher load index and more puncture resistance if needed.
 
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techdude99

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I took a pic before I left and posted it below.

All tires set to 51 PSI before leaving MS. Tongue was between 700-800 lbs according to Weightsafe. With a setting of 5.5, I verified the trailer was level and did a few stops with only the trailer brake controller to confirm the feel.

I just arrived in Sebring. In summary, no overheating and it drove fine. I averaged 15.8 MPG at 70 MPH and tried to keep the highway speeds under 2000 RPM while being mindful of boost. Anything more aggressive dropped it to 12.9 MPG.

The truck had some electrical gremlins surface but I'll address those in another thread.

I appreciate all feedback. The shared knowledge gave me areas to address and the confidence to make the trip.
 

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