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Old March 10th, 2012, 16:43   #1
alloutdoorsboy
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Default How hot should your brake discs be after driving??

Just curious as to how hot other folks rotors get whilst driving?? I checked mine mine after getting home today, very minor braking on the way home and all 4 rotors were too hot to hold your finger on. Is this normal?
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Old March 10th, 2012, 17:14   #2
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Should be. The pads make contact albeit lightly all of the time. There's going to be heat and the fact that you cannot hold on to it means it's, what, 130 - 140 degrees? Too hot to handle but not at all "hot."
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Old March 10th, 2012, 17:58   #3
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This low highway MPG is driving me nuts!! So I just went out and got on a highway and drove for 5 mins at 60mph without using brakes and came to a stop on an incline without using brakes. Rotors felt cool, guess just slowing down a bit to turn into my driveway does heat the rotors that hot. OK on to other things.....Guess the injector pump is next....
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Old March 10th, 2012, 18:20   #4
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Ive personally had one bad caliper. after driving three corners were too hot to touch, the bad one, the heat could be felt 3 feet away, and the whole rim was hot to the touch.

That was on my 95 pathfinder, not my jetta

Brakes can get very very hot under normal use as all that is slowing you down is friction between a ceramic pad and a metal rotor, in which friction translates directly into heat.
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Old March 15th, 2012, 10:17   #5
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Sorry to hijack the tread but.
my front driver side rotor gets very hot, changed caliper , hose, rotor & pad.
help !!! going nuts.
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Old March 15th, 2012, 10:56   #6
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I received a nice second degree burn on my leg from my rear disc on my bicycle, and both rotors will boil water off of them after anything but mild downhill runs.

A 4000lb car requires a whole lot more energy to stop; if there's no smoke or burning smell there's nothing to worry about.
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Old March 15th, 2012, 11:21   #7
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Remember... to stop a vehicle kinetic energy is converted into heat, mostly in the brake pads and discs... also a relative low (in machinery terms) temperature, I think, 60 Celcius, is too hot to touch..
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Old March 15th, 2012, 11:22   #8
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Jack up the rear of the car with PB off and see how easily the wheel will spin. IIRC, somebody here said the wheel should spin freely for one and a half revolutions.
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Old March 15th, 2012, 16:44   #9
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Occasionally, our cars can have a sticking e-brake cable that won't always stick. I had that on mine before changing cables. I have also read of other causes....I think vacuum booster issues maybe.
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Old March 27th, 2018, 05:27   #10
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Sorry to resurrect old thread but... I am on a 3rd set of front brake rotors and they are warped again!
Today I checked the brake rotors after some city driving. Rear rotors are completely cold.
Front left one is hot. Front right is even hotter, you can't hold the finger over half a second.

Question: has anyone ever measured the exact temperatures? What is considered normal and what's not?
Tomorrow I am going to do some actual measurements after mild driving.
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Old March 29th, 2018, 00:09   #11
Henrick
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Ambient temps around 1 *C. After normal city driving and exactly 3 minutes rest time, front right rotor is at 54 *C, front left one is at 41 *C.
Rear left - 18 *C
Rear right - 24 *C

Any clues what temperatues are normal?
What are the maximum values which ae safe?
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Old March 29th, 2018, 00:33   #12
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I wouldn't recommend touching the rotors to check temperature. The caliper is less likely to melt off a fingerprint.
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Old March 29th, 2018, 03:38   #13
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I was having problems with a sticking rear caliper a while back. So I pulled out my IR thermometer to check the rotor temps. The fronts were at about 130 (F). Neither of them were exactly the same. This caused me to check a couple of my other vehicles and temps seem to vary a bit. Fronts seem to be typically a little hotter than the rears. I came to the conclusion that the temps should be somewhat close say about 10 degrees or so on the same axle.

The rears seem to be somewhat less as a rule. My one side was at about 90 (F) and the other, the sticking side was a little over 600 (F). That was of course the problem side, the heat could be felt from 3 feet away, there was a very distinct brake smell even the rim was hot. After replacing the caliper I did a complete brake job, rotors, pads, etc.

I haven’t had to replace the wheel bearing yet, this was about six months ago, but I wouldn’t be surprised if I have to sometime in the near future.

So after checking temps across several vehicles, I’m not sure you can say the temperatures should not exceed X. I came to the conclusion that each side on the same axle should be approximately the same. If for instance one rear wheel is at 98 and the other is at 140 you probably have a slightly dragging e brake or frozen slider. 98 on one side and 108 on the other, and I wouldn’t worry about it.

Maybe someone else has done a little checking and can chime in with their experience and conclusions.
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Old March 29th, 2018, 12:49   #14
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Quote:
Originally Posted by Henrick View Post
Ambient temps around 1 *C. After normal city driving and exactly 3 minutes rest time, front right rotor is at 54 *C, front left one is at 41 *C.
Rear left - 18 *C
Rear right - 24 *C
Any clues what temperatues are normal?
What are the maximum values which ae safe?
Rotors can reach a few hundred centigrade Fahrenheit (300-400) and be well within operating range. Yours don't seem to have an imbalance when looked at it from that scale, and rear brakes carry much less load than the front when braking, so they will run cooler.
http://www.crashforensics.com/brakefailure.cfm

Last edited by ToxicDoc; April 4th, 2018 at 09:09. Reason: This source apparently is in Fahrenheit. Apologies for the error
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Old April 3rd, 2018, 16:18   #15
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Quote:
Originally Posted by Henrick View Post
Sorry to resurrect old thread but... I am on a 3rd set of front brake rotors and they are warped again!
Today I checked the brake rotors after some city driving. Rear rotors are completely cold.
Front left one is hot. Front right is even hotter, you can't hold the finger over half a second.

Question: has anyone ever measured the exact temperatures? What is considered normal and what's not?
Tomorrow I am going to do some actual measurements after mild driving.
BOTH rotors are warping on you?

Biggest impact on rotors is a hard and complete stop and then sitting still. All the built up heat by the pads will stay concentrated on one spot. I look to creep forward a bit after a hard stop. But...

Rotors really shouldn't be warping unless they're utter junk. I'd suspect calipers (sounds like you got one sticking) are your real problems. This past year I replace the front calipers (rotors and pads) with VW OEMs for the wife's car after I found one caliper sticking; it was crap work and crap parts the PO had commissioned that I didn't want anything more to do with (couple years back I'd found a stripped slider pin- required a heli-coil).
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