Temp Monitoring for Brakes/Bearings

Alloy

Well-known member
We were on a FSR in the fall along with allot of logging trucks towing our trailer.

As usual there was allot of twists and turns but this time we were pulling off (radio controlled) more for the logging trucks and I was pushing the speed trying to get to the end of the road. After a hard stop I was about to pull out when I saw smoke coming from a wheel.

In the past I've relied on the TPMS to monitor the temperature but this time the temperature rise was too fast for the sensor to pick up.

Is there a system that can be used/modified to monitor the temperature of the brakes/spindles/hubs/bearings?
 

roving1

Well-known member
Not sure a sensor would help much if it is the brakes.

If the trailer brakes were smoking but the vehicle brakes were not and did not feel bad you probably have the trailer brakes set too high or on too aggressive a weight profile. Most people have their trailer brakes cranked up way too high I have found jumping in and out of tow vehicles. It may not feel bad for stop and go driving but it's not sustainable for repeating heavy braking loads.

I have done a lot of vehicle testing for OEMs with trailers at max weight and vehicles at max GCVW. If the trailer brakes are cooking off first after some spirited driving they are set up too aggressive for the situation.

Also a brake can smoke because a bearing is puking grease or oil and nothing is wrong from a temperature persective.
 

rgallant

Adventurer
I am with the rest too much brake too often, you need to revisit the trailer setup. A temp monitor will not help much, more engine braking and slow down you need to accept on active logging routes your timelines can be pretty worthless
 

Alloy

Well-known member
Not sure a sensor would help much if it is the brakes.
EGT / coolant temp / engine&trans oil temp is monitored when going up a hill. Knowing brake temp would be just a useful going down a hill.

Depending on the grade our truck will run away in 3rd but in 2nd it is too slow. When we are descending a hill slowly and a loaded truck is coming up from behind there are 2 options. Either go faster or pull off. I've been pulling off and maybe I should be going faster. Maybe going faster works at one speed/grade and pulling off works at another.
 

OllieChristopher

Active member
When we are descending a hill slowly and a loaded truck is coming up from behind there are 2 options. Either go faster or pull off.
Or you let them go around. There is no such thing as too slow when it comes to safe descents. If you are in a situation ( single lane no passing ) where you need to pull off then you are doing it right.
 

Rando

Explorer
It sounds like you have TPMS on the trailer tires, in which case tire pressure may be able to give you some warning of brakes overheating. While it may take a while for the air in the tire to heat up, particularly if you are using a valve stem mounted TPMS, if the rim is getting warm the pressure will increase quickly. Tire pressure is proportional to the tire air temperature in the tire (in kelvin). For example, if you are nominally running 50psi in the trailer tires (at normal operating temperature), and the wheel temperature increases from 25 - 50C, the tire pressure will increase to ~55psi.

I definitely see this on very steep descent in my TPMS, it is not unusual to see a 5-10% increase in tire pressure under prolonged braking.

There are also systems to monitor brake temperature, but they are not cheap and/or straightforward:

If you were really interested in this you could probably DIY a way to measure the drum backing plate temperature for not too much money:
 

Alloy

Well-known member
It sounds like you have TPMS on the trailer tires, in which case tire pressure may be able to give you some warning of brakes overheating. While it may take a while for the air in the tire to heat up, particularly if you are using a valve stem mounted TPMS, if the rim is getting warm the pressure will increase quickly. Tire pressure is proportional to the tire air temperature in the tire (in kelvin). For example, if you are nominally running 50psi in the trailer tires (at normal operating temperature), and the wheel temperature increases from 25 - 50C, the tire pressure will increase to ~55psi.

I definitely see this on very steep descent in my TPMS, it is not unusual to see a 5-10% increase in tire pressure under prolonged braking.

There are also systems to monitor brake temperature, but they are not cheap and/or straightforward:

If you were really interested in this you could probably DIY a way to measure the drum backing plate temperature for not too much money:
Hey Thanks

Our TPMS will show a temp rise but there is a long delay. As we waited for the wheel to cool the TPMS did alarm but it took 2-3 minutes. Ideally we'd have something that tracks the temp minute by minute.

I've considered DYI (thanks for the links). Before I go there I'm going to try a wireless BBQ thermometer and clamp the thermocouple to the brake caliper. The hardest part will be figuring out if it should be set to Chicken, Pork or Beef :p
 

roving1

Well-known member
EGT / coolant temp / engine&trans oil temp is monitored when going up a hill. Knowing brake temp would be just a useful going down a hill.

Depending on the grade our truck will run away in 3rd but in 2nd it is too slow. When we are descending a hill slowly and a loaded truck is coming up from behind there are 2 options. Either go faster or pull off. I've been pulling off and maybe I should be going faster. Maybe going faster works at one speed/grade and pulling off works at another.
You are better off figuring out how to measure brake application pressure/effort which might be as simple as figuring out the PID for that and displaying it on a phone or tablet. Literally no vehicle has brake temps but some commercial vehicles do have brake application pressure gages which is admittedly much easier with air brakes.

Really though it's quite easy to pay attention to how much braking effort yields how much stopping effort and compare the feeling as you are descending a grade. The brake feel and fade is palpable before the brakes are smoking. You can literally apply the same brake pressure and count how many seconds it takes to scrub off 5MPH. Once you are aware of this it should be obvious when a descent is unsustainable at a speed and you need to slow down for the next gear.

Yes sometimes like on a really straight high speed stretch both aero load and engine braking can actually make a faster speed sustainable while descending. But the same technique applies. Try it out and if you have to hit the brakes twice in a row at a pressure and time that you know is unsustainable to drop 5mph then bail out and drop down to slower speeds.

For a lot of commercial trucks I drove for instance something like a 40% brake effort on a grade might with cool brakes take 2-3 seconds to scrub off 5mph. Doubling the brake effort would also probably half the response time. If that creeped up to about 5 seconds I knew that was not sustainable. At that point also you can double the brake effort and immediately tell you don't get the same slowing response. So at that point you need to decide is there only a couple more brake applications before the end of the grade and I am OK or will there be many more untill the end. Then you slow and try again. If the lower gear starts creeping up to the 5 seconds to drop 5mph then you have to go through the process again.

Sometimes that can lead to needing to pull over. But the act of stopping all the way and taking the cooling away from the brakes almost always heats them up to max temp anyways. So it's a fine line of being safe and not wanting to pull over but even pulling over earlier doesn't mean the brakes won't be at max temp anyways from having to haul the vehicle down to zero.

Once you think about it in these terms you will realize the gage is superfluous.

Really this should just be basic innate behavior for driving on grades in a heavy vehicle. The temp sensor thing is reinventing the wheel when it isn't really needed. Once you figure out the particular system that works for what you are driving it will be easy and even satisfying to do.
 

billiebob

Well-known member
Learn the truck trailer combination you are running. Drive so you don't disrupt commercial traffic who paid for the road in the first place. PS, a bit of smoke off te brakes is not an issue..... and how would a TPMS or brake temp monitor help with a loaded logger on yer tail. Suck it up Buttercup or get off the road.

PS, if yer trailer brakes are working properly they will not overheat before the truck brakes fail. I think yer issue is balance.

Finally. you are the reason 4 wheelers keep finding road closures. WE pay ZERO to build or maintain those Forestry Roads, I know we like to think OUR taxes pay to build them but in reality the Forestry Roads are resource roads for those commercially extracting resources. We just get access cuz it is too difficult to stop us. Once we get in their way, they apply to block our access.

A temp monitor would only tell you you need a better braking system so you don't create a problem.... but you already know that.
 
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Alloy

Well-known member
Learn the truck trailer combination you are running. Drive so you don't disrupt commercial traffic who paid for the road in the first place. PS, a bit of smoke off te brakes is not an issue..... and how would a TPMS or brake temp monitor help with a loaded logger on yer tail. Suck it up Buttercup or get off the road.

PS, if yer trailer brakes are working properly they will not overheat before the truck brakes fail. I think yer issue is balance.

Finally. you are the reason 4 wheelers keep finding road closures. WE pay ZERO to build or maintain those Forestry Roads, I know we like to think OUR taxes pay to build them but in reality the Forestry Roads are resource roads for those commercially extracting resources. We just get access cuz it is too difficult to stop us. Once we get in their way, they apply to block our access.

A temp monitor would only tell you you need a better braking system so you don't create a problem.... but you already know that.
Here's the newly release BC Auditor's report as to what's happening with FSR.

 
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