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-   -   High exhaust system temp affecting DEF and tire pressure? (https://www.irv2.com/forums/f278/high-exhaust-system-temp-affecting-def-and-tire-pressure-552916.html)

Butte64 09-06-2021 10:16 PM

High exhaust system temp affecting DEF and tire pressure?
 
There have been posts suggesting the high temps from the DPF and exhaust system on recent year coaches is affecting DEF quality.
Im wondering if it also affects tire pressure and temp in the area. I have 85 PSI in drive and tag tires. My PS tag, which is closest to the exhaust system, quickly increases pressure and temp while driving. It soon gets to 101 degrees and the warning starts. The others rear tires eventually get up to 101. Meanwhile the temp on the tag tire goes up, eventually getting up over 135 degrees. None of the other rear tires get that hot.

What are others seeing for pressure and temp on tag tires?

Gary.Jones 09-06-2021 10:54 PM

Jerry

I run 85 PSI in all my tags and drive Michelins tires and have my baselines set at 90 PSI. That lets those pressures pass through as "normal".

You know that there is nothing "God-given" about where you set your baselines and you should not set the baselines at the set tire pressure.... that is too low. You set them to a logical higher place given your set tire pressures. If your tires trigger too high warnings at perfectly normal pressures, set the baselines higher. Just don't get silly about how much increase you feel is tolerable.

Gary

Tim Fox 09-07-2021 05:13 AM

My tags are reasonably close to each other. About the highest any of the rears have gotten is around 104, and yes the alarm goes off at 101.

ransil 09-07-2021 05:30 AM

My Toad tires heat up from the engine / exhaust heat, dont notice tags heating up.

brobox 09-07-2021 06:26 AM

Quote:

Originally Posted by Tim Fox (Post 5904590)
My tags are reasonably close to each other. About the highest any of the rears have gotten is around 104, and yes the alarm goes off at 101.

That is what I can't understand with the factory settings. I'll bet the pavement temperature is higher than 101* during the summer in half of the nation. Why are many of the TPMS setup for winter travel only when it leaves the factory?

Butte64 09-07-2021 08:55 AM

Quote:

Originally Posted by Tim Fox (Post 5904590)
My tags are reasonably close to each other. About the highest any of the rears have gotten is around 104, and yes the alarm goes off at 101.



Thanks. How about the PS tag temp? I have significant difference in temp even when pressure close.

Turbojack 09-07-2021 10:39 AM

Have you weighed the coach and gotten individual weights? There could be a problem with too much weigh on those wheels

Butte64 09-07-2021 12:06 PM

Quote:

Originally Posted by Turbojack (Post 5904877)
Have you weighed the coach and gotten individual weights? There could be a problem with too much weigh on those wheels



Thanks, that is a good point. Those tires are all Michelin 315 at well under capacity. 85 PSI is the minimum pressure recommended even though the chart shows lower pressure possible for the weight being carried. A key point is the wide variance in temperature even though similar pressure.

jwprosser 09-07-2021 02:05 PM

You probably are not overloading the wheels. More than likely you have more weight on one side, remember that water tank and I believe grey tank are on the passenger side. As far as the dpf /scr causing a heat problem on your tires - nope all your exhaust is is to the rear of your tires about 3 feet away. you will get more heat from the asphalt than the exhaust.

KCBless 09-07-2021 03:46 PM

Could also be an alignment issue with that axle. Watch the wear on the tires and make sure it looks comparable to the other tires.

Tim Fox 09-08-2021 05:32 AM

Jerry, my tag tires are within a few pounds of each other. Nothing like the spread you seem to have. I would hope you have a faulty sensor, otherwise you would seem to have a mechanical issue. Have you checked to see what the sensor is seeing regarding temperature difference.

Butte64 09-08-2021 08:47 AM

Quote:

Originally Posted by Tim Fox (Post 5906000)
Jerry, my tag tires are within a few pounds of each other. Nothing like the spread you seem to have. I would hope you have a faulty sensor, otherwise you would seem to have a mechanical issue. Have you checked to see what the sensor is seeing regarding temperature difference.



Tim, the pressures are close. The PS tag hits 101 and alarm goes off. The DS tag is about 99 at that point. ThThe big difference is the temp. The PS tag goes to max 104 and DS tag max 102. The big variance is in temp. The PS tag gets much hotter than DS tag or drive tires. It gets up to similar temp as steer tires.
What temp do you see on your tag and drive tires?

Turbojack 09-08-2021 08:55 AM

Might try and verify by putting IR temp gun on all tires when you stop and compare to the sensors.

I was told that you can also go across the tread and make sure the temps are the same all the way across. If not may have an alignment or tire problem.

Butte64 09-08-2021 11:42 PM

Quote:

Originally Posted by Turbojack (Post 5906179)
Might try and verify by putting IR temp gun on all tires when you stop and compare to the sensors.



I was told that you can also go across the tread and make sure the temps are the same all the way across. If not may have an alignment or tire problem.



Good point about the IR temp gun. I have been doing that and see significant difference on outside sidewall temp and what is reported by TPMS. I also see that running in same direction for a long way with sun on the tire makes for much higher sidewall temp.

I had not thought about going across the tread, thanks.

Tim Fox 09-09-2021 06:50 AM

Jerry, while I’ve checked my temps, they have never given me a reading high enough to concern me. In all honesty, I don’t recall temps. I’m headed to AIM event at Swan Bay this coming Monday. It’s only forecasted to be in mid 70’s, but I’ll take a look and see what I get.

MuggsnMe 09-10-2021 04:05 PM

Tim
We just arrived here today at the AIM’s event.
Outside temp, 73, beer temp 32 F
Just incase you were interested
Thanks
Bob

Butte64 09-12-2021 08:40 AM

It looks like alignment is the answer. One side of tire showing more wear. Disappointing since I had alignment checked at Spartan in June. Now Iím a long way from home and Josams.

brobox 09-12-2021 08:46 AM

Quote:

Originally Posted by Butte64 (Post 5910680)
It looks like alignment is the answer. One side of tire showing more wear. Disappointing since I had alignment checked at Spartan in June. Now I’m a long way from home and Josams.

JME, Spartan left my steering timing 180 degree out after aligning my front end. By the time I reached Columbia MO the outside edge of the tire was worn. Last place I will trust for an alignment. The computer printout from Perry Legends comparing Spartan was unreal.

Tim Fox 09-13-2021 06:40 AM

Jerry, I drove about 150 miles yesterday at about 68 mph. Temperature was about 78 degrees. I started with 85 lbs on all the rears. Left tag got to 97 psi and 115 degrees F. Right tag got to 98 psi and 117 degrees. As reported on the valid tpms.

Gary.Jones 09-13-2021 11:03 AM

Whole different angle.... Maybe

Any possibility that you have brake shoes dragging more on one side than the other side and your tire temp problems are due to brake heating rotors which then heat tires and nothing to do with tire pressures????

Gary

Greg Hindson 09-14-2021 04:18 PM

Quote:

Originally Posted by Butte64 (Post 5906162)
Tim, the pressures are close. The PS tag hits 101 and alarm goes off. The DS tag is about 99 at that point. ThThe big difference is the temp. The PS tag goes to max 104 and DS tag max 102. The big variance is in temp. The PS tag gets much hotter than DS tag or drive tires. It gets up to similar temp as steer tires.
What temp do you see on your tag and drive tires?

I notice that the tires that are on the side where the sun is shining will have higher pressure because of the higher tire temperature.

vanlieremead 09-14-2021 05:58 PM

Definitely! If I stand still more than 10 minutes in a hot day with the engine running, the exhaust side gets hot and alarms.

Butte64 09-14-2021 06:50 PM

Quote:

Originally Posted by vanlieremead (Post 5914031)
Definitely! If I stand still more than 10 minutes in a hot day with the engine running, the exhaust side gets hot and alarms.



Thanks, good to know!

Butte64 09-14-2021 06:52 PM

Quote:

Originally Posted by Tim Fox (Post 5911928)
Jerry, I drove about 150 miles yesterday at about 68 mph. Temperature was about 78 degrees. I started with 85 lbs on all the rears. Left tag got to 97 psi and 115 degrees F. Right tag got to 98 psi and 117 degrees. As reported on the valid tpms.



Good to see your temps are similar.

Butte64 09-14-2021 06:54 PM

Quote:

Originally Posted by Gary.Jones (Post 5912257)
Whole different angle.... Maybe

Any possibility that you have brake shoes dragging more on one side than the other side and your tire temp problems are due to brake heating rotors which then heat tires and nothing to do with tire pressures????

Gary



Interesting thought. How do I check? Iíve used an IR heat gun in various places around the wheel and donít see anything out of order.

photraveller 09-15-2021 11:54 AM

Jerry, it's weird that one side gets affected more than the other, but I would still lean toward alignment issue. Plus, I haven't had any luck with Spartan Alignments. Find a good 3 axle truck alignment shop along your travels.

In our case, with pressures in drive and tag tires set at 85, our tags would heat up 10-15 PSI higher than the drive axle tires. After proper alignment, the hot PSI for the tags are still higher, but usually around 5 PSI higher than the drive axle tires.

Sadly, the wear I was seeing on the tag tires (one side bevel on each tire), continued until I replaced them last year. Even though I got religious about dropping tag pressure on all tight turns.

Steve

Gary.Jones 09-16-2021 01:04 PM

I've owned this Cornerstone (with disc brakes) now for about 3.25 years, and I have been in extensive stop and go traffic situations, once in New York state and once around Denver Colorado. In both, I am talking 30 - 40 miles of stop and go travel. Denver, I remember very well as there was some huge festival south of Denver and maybe 20 miles north of Denver, traffic came to a complete stop and then for ~ 40 miles went from stop and go, to traffic seemingly clearing, traffic picking up speed to 40-50 mps and then suddenly having to brake hard back to a crawl and stop-and-go crawling forward before repeating this whole process again and again. Never been in anything like these two situations before in all my driving.

The point of my story is that I began getting amber warnings on my tire pressures and tire temps on the tag and drive tires and then red tire pressure warning on all my drive and tag tires and I was VERY concerned and worked my way to the berm so I could check tire pressures. They were indeed high. Then I used an infrared thermometer to measure tire temps and the surface of the tires were high, but not all that critical. So, I measured the temps of my aluminum wheels and the wheels were very hot. By examining all around, what was very clear was that the wheel heat was from the disc brake rotors. The sun had nothing to do with these elevated temps. The very high temps were from the constant braking and even high speed braking in this "crazy" traffic pattern. I was heating the rotors highly and since the rotors are connected with the wheel mounts, the temps and pressures sampled from sensor bonded directly to the wheel with stainless steel bands, (not simply mounted on the stems) the brake heat was producing the excessive heat and pressures.

It took an hour or more at normal interstate speeds once this crazy stop-and-go pattern resolved before I was able to cool the rotors/wheels/tires to get the idiot lights back to the green range on the dash.

A dragging brake/rotor would imitate exactly your problem, IMO.

Any competent truck brake shop should be able to figure out this possibility.

Gary


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