Brake Data

[Aldev]

This is the data that I had after putting thermocouple wire on all 4 calipers and reading the temperature. The first chart was April 23, 2009. This chart started in Mammoth Lakes Ca. Going home. The down grade is a long slope on US 395 going into Bishop Ca. and then going home to the LA area.
All Numbers are degrees Fahrenheit


Left Front Right Front Left Rear Right Rear
44 45 45 50 Mammoth Lakes Ca.
51 48 55 60
53 50 59 63 Going down the
56 55 64 67 grade into
58 58 73 69 Bishop Ca.
58 61 86 81
89 82 103 95 In Bishop
65 68 84 81
75 81 99 100 In LA stop
& go Traffic
70 78 117 110 Going by LAX & home
This shows the actual temperatures for the 350 mile drive. I feel that these temps are normal.

My next trip on Memorial weekend (5/22/09) to Yuma Az. was different.

Left Front Right Front Left Rear Right Rear
65 65 65 65 At Home
96 108 160 173 Traffic in
94 107 189 206 Pomona Ca.
103 104 327 319 pulled off freeway
95 100 216 213
91 97 154 155
88 95 123 150 Sprayed calipers with water
88 95 115 120
84 85 108 110 Arrived in Yuma
78 77 78 78 Left Yuma
82 82 97 103 Traveling home
I couldn't pull off the freeway right away because of construction. They also had those concrete barriers along the shoulder. What a mess in stop and go traffic. We couldn't smell anything and the ABS light didn't come on.
We sat in the parking lot for an hour and then I got a spray bottle of water and squirted the rear calipers to cool them off This brought them down to about 120 degrees F. I didn't have anymore caliper problems the rest of the trip. When we reached the sand dunes outside of Yuma my cruise control quit. I had to adjust the switch at the brake pedal. This had happened once before and I adjusted it then. It's a plastic switch, so I think it wears a bit. Also the brake power booster comes on which in turn puts the brakes on. This didn't happen in Pomona as it's very audible when the motorhome is stoped. I'm thinking that the average temp on the front is about 100 degrees F and the rears run about 120 degrees F.for normal driving. I crawled under the motorhome today and didn't see any cracks in the rotors. I'm going to have to take the rear wheels off to really see. The ABS sensors are OK.
For your information--I hope that I haven't forgotten anything! I didn't mean for this to be this long. I sent in a brake post last year describing what I had done to get this information.

Al DeVinaspre
2002 32H Bounder
Torrance Ca.

[mfire1339]

All I can say is "Great Report"

[Aldev]

Information only: After I had my calipers getting hot and posting my data, I went to my tire place today and had them remove the rear wheels. We checked the rear rotors and brakes. The rotors didn't have any cracks and the pads appeared OK. My next step is to bleed the brakes again and wait for my recall for the brakes. I signed up with the S&J Chevrolet Workhorse Center in Cerritos Ca. These people have been very helpful in all my endevers. They didn't know how long it will be before I'm called. My next trip (July) is to the Eastern Sierra again and after that I'm going to Yellowstone (August). Now that I know what the caliper temperatures are going to be, I think that I will be prepared for any problems with the brakes.
Al DeVinaspre
2002 32H bounder
Torrance Ca.

[Aldev]

Driver, I'm curious about the Times listed on these posts. My Time here on the west coast is 10:05 PM, but the posted time is 5:03 AM today. Why is this?
I would like to know this.
Thanks,
AL DeVinaspre
Torrance Ca.

[DriVer]

Quote:

Originally Posted by Aldev Why is this? I would like to know this.

Al, I believe that our clocks are synchronized for Eastern Time however that said you have to go into your User Control Panel (User CP) and setup what Time Zone you are in. I'm sure that will answer your question and improve your time management.

Give it a try.

[John350]

Good post. It appears by your temps that the Chassis is rear biased for braking. Most likely do to the dual rears. Is my observation correcet???
John
Tiffin Allegro Bay
2003 W22 Chassis

[Aldev]

The rear brakes are running hotter than the front brakes by Approx 15-20 deg F. I don't know if this is normal or that there is more air movement at the front calipers than the rear. The front calipers are more exposed to the air flow.

Al DeVinaspre
2002 32H Bounder
Torrance Ca.

[DAN L]

Quote:

Originally Posted by Aldev The rear brakes are running hotter than the front brakes by Approx 15-20 deg F. I don't know if this is normal or that there is more air movement at the front calipers than the rear. The front calipers are more exposed to the air flow. Al DeVinaspre 2002 32H Bounder Torrance Ca.

per michelin and bridgestone web info, the rears will normally run hotter than the fronts due to limited airflow.
there is info in the archives of this forum about how much hotter and that normal tire temps measured at the bead will run up to 60 degrees hotter than ambient.

[DriVer]

Friction being what it is, 4 tires on the ground will no doubt retain more heat than 2 tires on the ground.

That said ..... That's why I use a dual tire inflater and monitoring device like a Crossfire.

Having both tires inflated to the same pressure will assure that heat won't be allowed to build up excessively in one tire causing it to prematurely fail. The use of a TPMS is also essential I believe. Knowing what's going on with pressures at all times is just as essential as knowing your oil pressure.

On my Crossfire I use a single transmitter TP device to monitor the pressure. It has been suggested to me that I should get a second manifold and device so that I can monitor both pressures individually. I'm considering it - I already have the 2 TP transmitters as I bought a 10 sensor system.

[Aldev]

This is a follow up of my Yuma trip. After getting home I used Oemy's drip method to change the brake fluid on the rear calipers. This actually worked great and was easy to do.It took approx 2 hours. We went to the Eastern Sierras on the 4th of July towing our boat. We didn't have any brake temp problems going and coming back. We left Crowley Lake approx (7200 ft) and went down the hill in 2nd gear towing to approx 4200 ft in Bishop Ca. without any problems. The front caliper temps were about 100 degrees and the rears stayed about 120 degrees. This was with minimum brakes going 35 mph downhill towing. Even in LA traffic during rush hour we had no problems. That's about it for now. My next trip is in August, so we'll see what happens.
Al DeVinaspre
2002 32H Bounder
W22 Workhorse
Torrance Ca

[wa8yxm]

I saw nothing alarming in any of those.. 20 degrees difference is nothing. and I did not see any temp over 120 in the list (hot water is 120 normally)

Now if I'd have seen say 200 degrees on one caliper.. I'd have been concerned (Actually, depending on the others, far less would have done it, say 150)

[gg]

Great Post, The sign says: In GOD we trust, ALL others bring data !!!!

[Full-Timers]

I am not sure I understand you. You said,

“Also the brake power booster comes on which in turn puts the brakes on.”

Are you saying the Brake Booster comes on all by its self? If this is happening (not sure how it can) then that’s a lot of your problems.

[EngineerMike]

Brake boost can "self-apply" brakes w/the Bosch HydroMax if hydraulic pressure from the pump is too high. Usual symptom is for the brake pedal to depress automatically when the engine is started, but return to normal angle when engine is shut off. When this is the case your brakes will at least drag and heat up, but may go further in applying stopping pressure. It is an unusual condition, but can happen.

Per the Bosch HydroMax Manual, the booster requires 3.2-5 gpm at 1000psi at the device (i.e. after losses at other things in the hydraulic system like the power steering gear). If the flow rate is too high, or the pressure too high, the booster can begin applying pressure to the master cylinder without signal from the driver.