Community Forums

bobk3d · 08-15-2017, 06:36 AM

They were never badly mismatched, but I recently did a full check on all my tires pressures, made sure the rear duals matched to within about 1 psi cold, checking with manual gauges. Recommended pressure is 80 psi, mine are set for 85, which should be okay. I measure in the morning before the sun comes up, temps in the high 60's, so I'm pretty sure I'm doing it right.

But yesterday on the road, I noticed that inner and outer had badly mismatched pressure while driving, and I actually had an over-temp alarm as I pulled into my campsite.

So I made it a point to check this morning, and the TPMS shows them still being matched to where I set them.

I know the temperatures from the EEZTire can be affected by sun on the sensors, but that wouldn't explain the pressure difference.

The only thing I can think of is that I spent the entire day on hilly and curvy 2-lane roads (US 209 & US 6, Kingston NY to Scranton). Perhaps the outside tires take more of the load on corners?

Has anybody else run into this? Any thoughts? I don't want to mess up my tires.

jim27358 · 08-15-2017, 06:42 AM

You didn't say just what the pressure difference was.

AITG · 08-15-2017, 06:44 AM

Is the circumference of the inner and outer tires approximately the same? If the tires are mis-matched, this can happen. You'll need to raise the tires slightly to run a tape around them.

Boondockin · 08-15-2017, 06:46 AM

Are the tires new? Never had any issues before?

RT 41 · 08-15-2017, 02:46 PM

On the open highway your inboard tires are riding on the crown of the road and are supporting more weight thus higher temps ( this comes from a driver of an 18 teen wheeler with 40 years on the road)

Boondockin · 08-15-2017, 02:55 PM

Quote:

Originally Posted by RT 41

On the open highway your inboard tires are riding on the crown of the road and are supporting more weight thus higher temps ( this comes from a driver of an 18 teen wheeler with 40 years on the road)

I agree 100%... but it I think he was indicating the outside tires were hotter than the inside... if that's the case... maybe the sensors are reversed...?

Mac99 · 08-15-2017, 02:58 PM

Also, where did you get the 80psi base inflation ? If you
did not get weighed and get the manufacturers load/inflation
chart then you might have an issue there.
Previous post are spot on. The tire temp could be as much
as 50/60 degrees above ambient temp and be normal.
Also, don't understand the "badly mismatched" phrase.
The tires must be exactly the same including age, size,
brand, etc

Waiter21 · 08-15-2017, 03:04 PM

Engine exhaust??

bobk3d · 08-15-2017, 07:49 PM

Thanks for the replies.

To be honest, I didn't pay close attention to which tires were higher/lower when driving, but the over-temp alarm was on the outer driver side. I think I noticed the inner passenger side was high earlier, but not sure. The difference was something like 95psi vs 110.

Given the road conditions, it's quite possibly from the road crown effects. I hadn't noticed such a big mismatch before. Tomorrow I have mostly Interstate driving, so I'll see how that goes and take better notes.

more details as requested:

The tires are about a year old, Dunlop SP348. 80 lb recommended pressure is from the RV. I think I checked the Dunlop chart when I got them, but it only showed inflation for the full rated load, and I'm 30% below that. I can't recall the entire process, but I think I looked into it and arrived at the 80lb number using some derating method.

I'll be darned if I can find inflation charts vs load for ANY brand of tire. The best I ever found was some sort of "industry-standard" chart, which agreed with my other two assessments. And then I added 5psi for good luck.

Quite possible I should increase psi, since my gas mileage has sucked with the new tires. But I can't find any documentation that I should inflate them more, and they usually run reasonably cool.

I'm under the GVW; rear axle is close to capacity (13.5K), but not over. Actually I last weighed it with full tanks so it's probably less now. Front axle is about 6500 vs 7500 capacity.

Thanks again for the suggestions, I'll report what I find after some different roads.

GreaTOne65 · 08-15-2017, 08:02 PM

bobk3d, you didn't specify what size tires you are running, nor what coach, but with limited information, I don't believe any tire larger that a 19 should run a measly 80 psi.

bobk3d · 08-16-2017, 06:15 AM

245/70-19.5 Built with load range F, I'm running G.

2003 Bounder 32W, as in my sig. 20.5K GVW, Workhorse W-22/20 chassis.

Quote:

Originally Posted by GreaTOne65

bobk3d, you didn't specify what size tires you are running, nor what coach, but with limited information, I don't believe any tire larger that a 19 should run a measly 80 psi.

Crasher · 08-16-2017, 07:23 AM

If you get that kind of information from the TPMS again, stop and check the pressures with a gauge. It wouldn't be the first time a sensor was erratic or wrong. Buy an infra-red tester and confirm what the tire temp actually is. I never go by the temp that the sensors read. Too much variation from the ambient air.

Dark Sky · 08-16-2017, 08:38 AM

I run all tires between 105 and 110 psi. Temperatures fluctuate somewhat based on weather, and the 'heavy side' is always warmer. And, the two inner duallies have always been the warmest two tires under any road condition. They are clearly taking more of the load than the other tires.
The tpms may be quite repeatable and good for temperature trends, but in no way are the displayed temperatures accurate. My infra-red sensor shows that the sidewalls are substantially warmer than what the sensor sees at the tire valve. I can't trust my memory for accuracy, but think the delta is about 25 or 30 degrees f.
Back to the original post, if you got a high temperature alarm on the tpms, I would check the pressure with a manual gauge, and have your brakes and wheel bearings checked. Something is going on.

DENSHER · 08-16-2017, 08:48 AM

I have Goodyear 19.5 load range F with same weight on front (6500 lbs) and 12,300 on rear and load range chart in my chassis manual calls for 95 psi in all 6 tires. Michelin has lower psi listed for same loads but @ 13500 on rear calls for 90 psi. I have tried running lower pressure @ 85 psi before getting it weighed to soften the ride and noticed tire temps increased faster and higher at lower pressure and handling, steering comfort decreased.