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Wednesday, August 9, 2017

New Goodyear Endurance pressure & temperature question

Saw this question on temperature and pressure increase on a new set of Goodyear Endurance tires.

"Took our first trip with the new Goodyear Endurance tires.
Trailer rode great, better than the old tires.
So, on this first outing I closely monitored the TPMS to see if there were any differences in the readings I had with the old tires.
Obviously, the first difference was the starting "cold" tire pressure. (65 psi vs the old 50 psi)
The first thing I noticed was how quickly the tire pressure increased once we got on the road.
87 degree day, 60-63 mph, tire pressure on sun load side got to 75psi (73 - 74 psi on shaded side). Tire temp got to 96 - 97 degrees (99 degrees on one tire briefly).
This compares to the average 5 - 8 psi increase I experienced on a typical trip with the old tires.
This brings me to my question.
Is a 10 - 12 psi increase in pressure considered acceptable? If so, what should I set the high pressure alert at on my TPMS?
"

My reply:
The temperature and pressure changes are reasonable for most 14" - 16" RV tires, especially trailer  applications, but I will focus on your question.

Not sure if your "test" is "scientifically" sound -- You were comparing two different tires (LR-C vs. LR-D) and a new tire vs. old used tire.

New tires will always run hotter than old tires.

With nominally dry air the pressure will increase by about 2% for each +10F. One other related item is that aftermarket external TPMS are not reporting the temperature of the hottest areas of the tire which is internal to the structure. Also while it may not seem reasonable, it has been demonstrated that the temperature of the air inside a tire is not uniform. It is also known that the metal body of valve stems and the metal body of the sensor will be cooled as it whips around in outside ambient air which will result in a lower reading.

In all probability your tire is actually 20 F to 30 F hotter than the TPMS is reporting, but this is within the expected design limits considered by tire engineers.

New tires do run hotter than old for a couple reasons. Extra stress as initial cross-link chemical bonds are broken as tire is "broken in." This takes about 100 miles. New tires have deeper tread depth, which will also make a tire run hotter, which means more pressure growth.  Your GYE have extra components (mass) in the tread. Read the sidewall and I believe you will see Nylon cap plies in the tread which were not in the old GYM tires. This is another contributor to more heat.

To your question on pressure increase setting for TPMS. As I covered in my blog post on TPMS settings I figure that +25% from baseline is a reasonable number, but obviously the pressure you select for your baseline may affect the top number.

Bottom line. Your numbers look normal and acceptable.

##RVT806

4 comments:

  1. I have a suspition I was sold wrong size tires for my Silverado 3500 dually. Stock size was 215.75.16, my local Les Schwab recommended 235,75.16. Looked fine at 1st but by about 5000 miles I notice that the two tires on each side touch at the sidewall at the bottom of the tire. The rest of the circumference of the sidewall they remain about 3/8" apart. Looking for a non'scwab opinion before I go back to them.

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    Replies
    1. Sorry but without changing wheels that control the dual spacing I do not know of an option. Looks like Schwab will just have to swap the 235 back to the original size tire to avoid the "kissing"

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  2. I am NOT a professional, but I had the same truck with the same 215 tires. I always disliked the look of those skinny tires and wanted to go wider when I replaced them, but a quick glance told me that would be a bad idea, for the reason you mention. I could be wrong, but 2 tires touching just seems like a real poor idea.

    ReplyDelete
    Replies
    1. Roy, You are not wrong. Dual tires should not touch at any point. This could lead to tire failure.

      Delete

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