TPMS - temperature setting

Ger08 · Senior Member

TPMS - temperature setting

Peter_n_Margaret · Guru

Temperature readings from external TPMS are a complete waste of time. They can not be useful.
I have a set on the OKA. The TPMS's were showing at 40C. I made some checks with an infrared thermometer. The METAL valve stem was 50C, the steel rim was 60C and the side wall of the tyre was up to 70C. The temperature of the inside of the tyre would be even higher.
The TPMS is in a howling gale of air as you drive down the road, stuck on the end of a rubber valve stem. It can not possibly give any temperature information about the inside of the tyre that is remotely useful.
The default setting is usually 70C. I suggest leaving it at that, but being under that does not mean that the tyre has not already overheated and been fatally damaged.
Cheers,
Peter

erad · Guru

IF you have the internal type of TPMS, the temperature readings would mean something, but the units with sensors screwed onto the valve stems are useless because of excess cooling as the wheel rotates. As for temperature settings, imagine what the temperature of the tread must be when travelling at high speed, heavily laden in Central Australia at mid summer. I would expect up to 50 Deg C ambient temperatures, with sun radiation heating the blacktop to at least 70 Deg C and friction in the tyre increasing the temperatures to at least 75 Deg C. So if you have internally mounted sensors, I would be inclined to set the alarms at 80 Deg C.

Fast_Eddie · Member

Guys, first post as a new member. Amongst other things, I am an ex tyre design engineer and test driver - so a few comments that may help with this discussion.

Low pressures are by far the single biggest reason for tyre failure, so a good TPMS system is very important, especially for the sort of work that you guys are doing. Tyre failure is almost always an outcome of low pressures - so monitoring tyre temperature is really irrelevant for that situation.

Where tyre temp can help is in two main scenarios:
1. Where you may have had a puncture in the tread area and have had it repaired (hopefully professionally and not just a plug through the tyre!). In this case over time water WILL get into the steel belts and will almost always result in the steel belts rusting. This can lead to a belt separation and tyre failure without pressure loss. Best to regard a repaired tyre as temporary and replace the tyre after no more than 12 months. May last longer, but it is a guessing game because you cannot see inside the tyre.

2. If the tyres have a manufacturing fault. This is a pretty rare event these days as most quality manufacturers are pretty good.

in these two cases the tyres may not lose pressure until they actually self destruct (and in doing so causing lots of damage and maybe loss of control). In this situation, the tyre heats up very quickly and the rolling resistance increases quite markedly. If the tyre was on the car on bitumen then you would notice the extra drag on the vehicle. On a caravan not so easy to notice, particularly when off road.

Very generally speaking failure will occur at around 120 - 140C at the edges of the belts in the tread area. But this is impossible to measure with an on valve sensor. The issue is, as has been pointed out earlier, where the temp is being measured with your TPMS sensor.
Regardless, the temp you set is largely irrelevant. What is useful for this scenario is being aware of any rapid increase in temp. You can then stop and work out what is happening and if in doubt, change the wheel anyway until you can get to a tyre store.

Hope this helps.

Whenarewethere · Guru

I have watched major chain tyre suppliers plug a few tyres. Remove screw etc, drill hole in tyre, plug, air up with over saturated air supply.

No different to what I can do with my air compressors, after cooler, refrigerated condenser, moisture trap.

Possum3 · Guru

Fast_Eddie wrote:
Guys, first post as a new member. Amongst other things, I am an ex tyre design engineer and test driver - so a few comments that may help with this discussion.

Welcome to GN's Fast_Eddie; It is good to see another Engineer on the site.

Fast_Eddie · Member

Sure.

So long as you know where you can and cannot repair, you remove the tyre from the rim, know how to carefully inspect the inside for damage, buff and patch correctly - all good.

The issues arise when someone who does not know how to do it properly simply plugs from the outside and thinks it is a permanent repair.

JackoFJR · Senior Member

I have seen temps as high as 60c . I just set the temp high to stop the alarm beeping , like others have said the temperature is next to useless .
I have a Patrol now with internal pressure sensors as std no temp , pressure is all you need .

Whenarewethere · Guru

Once you have had TPMS on a bit you really notice how much tyre pressure changes over the day. Even things like the sun on one side of the car for 30 minutes. That side will be a bit higher pressure. First thing in the morning everything is a bit lower with colder weather.

I would easily notice an abnormal 2°C rise in temperature above other factors.

My setup. I prefer it over the car's own system as it only does 5 wheels, which is more difficult if you have two spares.

Gary and Barb · Senior Member

Good, sensible post Fast Eddie, without the huff! Thanks.

I have a TPMS and haven't been too worried about the temperature setting. I figured that the pressure was far more important.

-- Edited by Gary and Barb on Sunday 19th of September 2021 02:46:25 PM

Peter_n_Margaret · Guru

Gary and Barb wrote:
I have a TPMS and haven't been too worried about the temperature setting. I figured that the pressure was far more important.

Actually, the temperature is much more important that the pressure, but it is simply too difficult to measure with any useful accuracy.

Provided you drive at walking speed, there is no problem driving around all day with a tyre at 10psi.

When the pressure is low, there is no risk to the tyre unless the speed is too high for that pressure. If that happens, the temperature in the tyre increases and it is the excessive temperature that destroys the tyre.

The TPMS lets you know (reasonably accurately) if the pressure decreases significantly. Provided you have the alarms set appropriately, that is the signal to stop before the temperature increases and destroys the tyre.

Cheers,

Peter