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Old 12-06-2019, 08:43 PM   #1
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Continental Tires PSI rising 20

I recently bought Continental 255/70R 22.5's for my Tradewinds, it has always ran Michelins but none were available. I'm traveling from Southern Utah to Southern Arizona and am running 100psi in all 6 tires. I have a TST TPMS that I've used since TST first started that monitors each tires temperature and psi. The 100psi goes up to 120psi going down the road at 65mph. Outside Temps were running high 50's/60's. The Michelins never went up this much. I don't think they ever went more then 6-8 psi, even in 108 outside temperatures. My Honda CRV tow vehicle only gains 2 to 4 psi and these are with Continentals also. My old Michelins were 14 ply and the new Continentals are 16 ply, could this be the cause???

Is there anyone on here who is running the same size Continentals with a Tire Pressure Monitor System that monitors PSI and Tire Temps?? One more thing my Tire temperatures were running a few degrees above the outside temps. The tires were not hot at all, only problem is the 20 degree rise of the psi
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Old 12-06-2019, 10:26 PM   #2
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I added a TST monitoring system to my coach last year. I have been surprised at how much the tire temps rise as I drive down the road at highway speeds.

What you are seeing doesn't seem abnormal at all. I have Michelin tires and see similar temperature rises.
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Old 12-06-2019, 10:37 PM   #3
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There is no problem with tire temperatures, it's the psi going from 100 to 120. My Michelins usually would only gain less then 10 psi on the road.
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Old 12-06-2019, 11:33 PM   #4
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During operation, tires will normally increase 10 to 15% psi. When monitoring internal temperature, then tire operating temperatures will rise to "ambient temperature + 60 degrees F" …. so in your case, 120 degrees F.

Do all wheel positions run at the same psi/temperature?

Were the Michelin tires also 255/70R22.5 XZEs, or were they 235/80R22.5 XRVs?

Link to datapages:
https://blobs.continental-tires.com/...guide-data.pdf


https://www.michelinb2b.com/wps/b2bc...s_Brochure.pdf
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Old 12-06-2019, 11:41 PM   #5
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Quote:
Originally Posted by PatriciaM View Post
During operation, tires will normally increase 10 to 15% psi. When monitoring internal temperature, then tire operating temperatures will rise to "ambient temperature + 60 degrees F" …. so in your case, 120 degrees F.

Do all wheel positions run at the same psi/temperature?

Were the Michelin tires also 255/70R22.5 XZEs, or were they 235/80R22.5 XRVs?

Link to datapages:
https://blobs.continental-tires.com/...guide-data.pdf


https://www.michelinb2b.com/wps/b2bc...s_Brochure.pdf
I run 100 psi in all 6 tires, down by Tucson AZ today with outside temps around 60 the psi on 3 of my tires went to 120, the others were 2 @ 118 and 1 @ 117. Tire temps were 64-68. And yes my Michelins were 235/80R 22.5 XRV
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Old 12-07-2019, 08:23 AM   #6
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Quote:
Originally Posted by sgtjoe View Post
There is no problem with tire temperatures, it's the psi going from 100 to 120. My Michelins usually would only gain less then 10 psi on the road.
Sorry, it was late when I was replying. I meant to say the pressure changes I see are consistent with yours. It is normal.
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Old 12-07-2019, 08:38 AM   #7
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...fairly normal, depending on tire size.....I have my TPMS alarms set at roughly 10% below and 20% above "normal" cold pressure settings....ambient or road surface temps, sunny side of coach, cross-winds, exhaust from coach on tires [eg towed vehicle] can all contribute to rises in operating tire temps....
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Old 12-07-2019, 11:18 AM   #8
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Quote:
My old Michelins were 14 ply and the new Continentals are 16 ply, could this be the cause???

Partly. A greater ply rating generally means a stiffer sidewall and that tends to generate a bit more heat from the rolling flex. Other tire differences that can effect the amount of heat when in motion include tread design (smooth vs knobby), traction rating, high mileage vs softer tread compounds, and size differences (more or less rubber in contact). Inflation is also a major factor, where "proper inflation" is determined by the tire manufacturer's inflation tables. Under-inflation leads to greater heat. Are you sure that 100 psi is the right psi for your load and the tire size?



In any case, what you are observing is within normal range, though toward the high end. I'd re-check inflation. And are the Continentals the identical size to the Michelins, or perhaps a slightly different equivalent?
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Old 12-07-2019, 12:03 PM   #9
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Although elevation alone wouldn't account for a 20% change it is another consideration on tire pressures.

https://www.coyoteents.com/compensat...ings-altitude/
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Old 12-07-2019, 12:05 PM   #10
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My Michelin 235/80R22.5 XRV's are all inflated to 90 psi, which fully supports both axle GAWR weights for our 22,000 lb motorhome. I routinely see them around 103-109 lbs psi. The tire temps on the TST 507 were showing around 84 when this happened yesterday.

Yes, fully loaded we weighed in at just below our GVWR and we rarely run with full water or close to that.

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Old 12-07-2019, 12:55 PM   #11
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10-15% increase from "cold" to "running" temperature is common. 20% (20 psi on a 100 psi inflation) is at the high end of normal. However, if the ambient temperature or the altitude also changes, the change in psi differs even more (up or down).



All tires are equally affected by ambient temperature and atmospheric pressure (Charles' Law of Gases) but the heat generated by the tire itself when in motion is determined by its materials, construction and design.
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Old 12-07-2019, 05:03 PM   #12
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If it were my coach I would add 10 psig to the tires and see if the increased psig was significantly less

Ambient temperatures aren't high enough to justify that high of increase

What would the increase be on a 100 degree day?
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Old 12-08-2019, 12:09 AM   #13
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If you start out with 100 psi @50* and over the course of the day you have 120 psi, as was said, that's 20%. However, if when you reach that 120 psi, the OAT is 80*, 6 psi of that 20 psi increase is due to ambient temp increase. In other words, if you had not mover the coach at all, when the tires increased to the 80* OAT, they would be @106*. The result is that 14 psi of the total increase was due to rolling resistance. Which is an adjusted 14% increase.
Some days my steer tires will go from 115 psi @ 60* up to 141 psi @ 100* which is over 20%. Because of the 40* increase in OAT temperature, close to 10 psi of increase is due to OAT temp increase. When the OAT remains the same throughout the day, my pressure will be near 132 psi, or a 15% increase from rolling resistance.
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Old 12-08-2019, 01:29 AM   #14
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I run a coach very similar to yours in size and weight (2002 DutchStar 40ft), but for some reason mine left Freightliner with slightly beefier tires— 275/70/22.5. The coach is right at GVWR of 31K Lbs.
I am running Michelin XZA2 @ 110 front and 95 rear, and I see the same pressure rise that you do on the highway— about 15-20%.
I’d say you’re in the normal area.
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