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Topic: Disk brake temperature (Read 1653 times) previous topic - next topic

Disk brake temperature

Using my Raytek laser IR thermometer I have been checking brake temps after extended driving. Today I took these readings after pulling into our neighborhood after driving about 150 miles:
Left front disk: 220 F
Right front disk: 315 F

At last inspection both front pads had 60% left, and there is no pull either way while braking.

I'm wondering if this difference is within normal operating range for left and right disk brakes?
Peter and Tammy Fleming
1991 U300 GV 40 - Sold, owned for 4 years
Downsized to Roadtrek Popular 210 class B

Re: Disk brake temperature

Reply #1 –
I would drive down the road without braking for several miles. Coast to a stop without touching the service brakes on a slightly uphill section and then apply the parking brake and shoot both disks again. One may be sticking from inactivity during the winter season. Even wear may not reflect what is happening right now. One disk running warmer than the other also may not be felt during braking. Elevated temperature on one side could compromise braking when starting down steep grades as one side could fade before the other.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Disk brake temperature

Reply #2 –
WHY I just cleaned, inspected and installed the spring kits on all wheels, to make sure all is well, pads back off when not needed, also if the slack adjuster is too tight causing a slight drag will sure elevate the temps.  if my brakes were running that hot, I would be in a near panic state. :o unless you just hogged it down with the brakes from highway speed.

Re: Disk brake temperature

Reply #3 –
Rule of thumb for me has been rotors on the same end running within + or - 10 degrees of each other. Front rotors tend to run hotter then rear rotors with front brakes doing about 60% of the braking.With the large mass of the rotors on a Foretravel they will hold there temp a lot longer then the smaller rotors on a car,but you have to great a difference right to left. Gam
joseph gambaro
1999 U295 36'

Re: Disk brake temperature

Reply #4 –
The trouble with these new-fangled testers is now I am measuring everything. My new alternator runs 200 F after driving with lights on and running the fridge on the inverter. Using my clip-on DC ampmeter, this load is a constant 70 amp draw from the alternator driving down the road. The alternator (Delco 28si) is rated to 125 C (257 F) so 200 F doesn't bother me.

In reading up on disk brakes, 300 F is not unusual after a stop, and 400 F is not out of the question. Also, lightly applying brakes over a long distance can cause one side to heat significantly higher than the other, due to normal caliper operating friction between left and right. A firm braking for a few seconds, followed by no braking for a few seconds will more evenly heat the rotors. The same kinetic energy is dissipated as heat whether you "pulse" the brakes vs a long light brake pressure to stop the vehicle. I personally feel that +/- 10 degrees, although ideal, won't always be the case. I also think that my near 100 degree difference is excessive, and warrants further checks.

Pierce, I will try your test measurement as soon as I can and post the result.
Peter and Tammy Fleming
1991 U300 GV 40 - Sold, owned for 4 years
Downsized to Roadtrek Popular 210 class B

Re: Disk brake temperature

Reply #5 –
I've been checking mine at most rest stops for the last 2 months/4000 miles.  I've never seen a temp over 150F and the rotors are usually within about 20 degrees of the tires.  Today at 80-90F ambient temps, I was running about 120 tires and 130 brakes max--usually 10-15 degrees cooler.

Rich 
Rich and Peggy Bowman
2002 U270 3610 WTFS, build #5939--"Freedom"
2022 Jeep Grand Cherokee Summit 4xe
SMI AirForceOne brake system
PakCanoe 15

Re: Disk brake temperature

Reply #6 –
Don't forget that most IR thermometers assume a constant emissivity that is usually set for dull objects.  Shiny metal (i.e. brake rotor) can give you false readings.
John Fitzgerald
1991 U300 (SAI) Side Aisle Island Bed 40'
Detroit 6V92 with Allison Retarder
Meridian (Boise), Idaho

Re: Disk brake temperature

Reply #7 –
Brake Update:

My son and I took the coach out tonight for a test drive and measured the front disks after driving a couple of miles with a slow stop using very little braking. The left front disk had increased from 80 F to 100 F, right front disk had increased from 80 F to 180 F. I called and discussed with the shop where I have had work done and the consensus is I likely have a frozen caliper after storage over winter. We drove the coach to the shop and they are going to service the brakes on all 4 corners.
Peter and Tammy Fleming
1991 U300 GV 40 - Sold, owned for 4 years
Downsized to Roadtrek Popular 210 class B

Re: Disk brake temperature

Reply #8 –
Peter,

Here is a link to the service manual.

Pay particular attention to the section on lubrication.  It details removing excess grease from the assembly which can cause brake drag.  Also DO NOT allow the shop to use regular grease on the calipers.  Use Clay Based grease Air Disk Brakes Lubrication
Not all shops understand these brakes.

http://beamalarm.com/foretravel-links/PDF/brakes-maintenance-manual-mm4m.pdf

Keith
Keith, Joyce & Smokey the Australian Cattle Dog
1995 U320 SE Extreme 40' WTBI Build # 4780, with a Honda CR-V hopefully still following behind.
Motorcade # 17030
FMCA # F422159

Re: Disk brake temperature

Reply #9 –
Just got the coach back from the shop. All disks and pads were good, the RF caliper was stiff and not letting go. The shop was able to service the caliper and not replace it. I also had the hub oil changed to synthetic. After 25 mile trip home the left front disk was 113 F and the right front was 114 F - much better.
Peter and Tammy Fleming
1991 U300 GV 40 - Sold, owned for 4 years
Downsized to Roadtrek Popular 210 class B

Re: Disk brake temperature

Reply #10 –
Pulse stopping is not positive with air brakes.

Clean & lube Disc Brake calipers every few years.  Be sure to clean and lube the guide pins.  Sad to say this but this portion of the procedure is overlooked more often than not.

Due to the design of truck disc brakes, if you have an instance of continued long braking, keep an eye on the pads, they are know to
separate from the backing (a spare set?).  Why this happens, I wish I knew but it does happen unlike drums. 

Anything out of the ordinary merits inspection, especially brakes.

Greetings, pc
S/W Houston 95" U320C SE/40' 
Build #4778  Cummins M11
Repairs & Covered RV Parking (BAO)
PPL is close..

Re: Disk brake temperature

Reply #11 –
Quote from: prfleming –
Just got the coach back from the shop. All disks and pads were good, the RF caliper was stiff and not letting go. The shop was able to service the caliper and not replace it. I also had the hub oil changed to synthetic. After 25 mile trip home the left front disk was 113 F and the right front was 114 F - much better.

The meritor spring addition I think helps addressing dragging calipers. 
"Riding and rejoicing"
Bob
1997 U320 40' Mid entry, build 5132,  wtbi ce27, 4th owner
2007 Solara convertible
2 prodeco tech outlaw ss electric bikes

1095 watts solar
08 Ls 460 and a sc430
2000 Ford F-250 superduty 4x4

Re: Disk brake temperature

Reply #12 –
The spring kit does help, buy it does not make it idiot proof, you still need to clean the slide pins about every  30-40 k miles, has been my experience.