Overheating effect on brake system

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Post Wed Nov 26, 2008 10:27 pm

What are the effects of overheating on a road-going brake system?

The reason I ask is because I was driving extremely hard up in some mountain roads and I over-cooked the brakes, they faded and were smelling horrible. It got to the point where braking was almost gone.

So what are some possible effects on the entire system? Will the pads need to be replaced due to possible glazing or whatnot? Will the brake fluid need to be replaced? Or what about the calipers? Any damage that might have happened internally? Or will everything be fine with no consequences hopefully? :?

The calipers are two piston front/one piston rear, with ventillated discs, and normal pads (everything OEM besides pads).

Thanks in advance.


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mx_tifoso
 
Joined: 30 Nov 2006
Location: North America

Post Thu Nov 27, 2008 2:01 am

Pads are probably glazed. You could try to sand off the glaze, but replacement is a better route. Try EBC green pads.

Calipers should be OK.

Brake fluid probably boiled. Drain and switch to a DOT 3 or 4 (at least).

Rotors might have warped - have a professional check their run-out.

I'm only an enthusiastic amateur (the Emma Peel of this board, if you will) my hands-on training ended in the drum brake and carbureter era-- looking forward to more erudite input.
Enzo Ferrari was a great man. But he was not a good man. -- Phil Hill
donskar
 
Joined: 3 Feb 2007
Location: Cardboard box, end of Boulevard of Broken Dreams

Post Thu Nov 27, 2008 2:20 am

Maybe more extreme, but recalling an incident Martin Brundle had, restricted ventilation on calipers one time led to them overheating and part melting - brake pedal suddenly became VERY long then came a moment of chasing down the nearest wall to stop against :wtf:
Agree with changing pads and fluid and that the discs may not be too good. Bit of a rude question - were you dragging the brakes at all? If this is something you are likely to have a go at again, maybe a bit of an upgrade is needed, maybe just slotted/drilled discs to wipe the pad face. Or a stout bit of chain and an anchor to sling out the back...
I am an engineer, not a conceptualist :)
alexbarwell
 
Joined: 20 Mar 2008
Location: London

Post Sat Dec 13, 2008 12:53 pm

donskar wrote:Pads are probably glazed. You could try to sand off the glaze, but replacement is a better route. Try EBC green pads.


Sanding will will do with a medium emery paper.


donskar wrote: fluid probably boiled. Drain and switch to a DOT 3 or 4 (at least).


Push the boat out and get some AP660. Mine go the same way when I drive like an idiot through the round abouts in Milton Keynes on the way to work.
"Whether you think you can or can't, either way you are right."
-Henry Ford-
Scuderia_Russ
 
Joined: 17 Jan 2004
Location: Motorsport Valley, England.

Post Sun Dec 14, 2008 3:17 am

Scuderia_Russ wrote:
donskar wrote:Pads are probably glazed. You could try to sand off the glaze, but replacement is a better route. Try EBC green pads.


Sanding will will do with a medium emery paper.


donskar wrote: fluid probably boiled. Drain and switch to a DOT 3 or 4 (at least).


Push the boat out and get some AP660. Mine go the same way when I drive like an idiot through the round abouts in Milton Keynes on the way to work.


Scuderia_Russ, I'm never shy about exposing my massive ignorance (and I HAVE done a quick Google . . .): when you refer to AP660 - is that an AP pad or fluid? My little SE-R can use all the help it can get!
Enzo Ferrari was a great man. But he was not a good man. -- Phil Hill
donskar
 
Joined: 3 Feb 2007
Location: Cardboard box, end of Boulevard of Broken Dreams

Post Mon Dec 15, 2008 12:02 pm

Brake fluid. Overly extravagant for your road car but you would never have to worry about it boiling again. 551 would probably do it. Or you could drive slower and brake gentler for longer. :wink:
"Whether you think you can or can't, either way you are right."
-Henry Ford-
Scuderia_Russ
 
Joined: 17 Jan 2004
Location: Motorsport Valley, England.

Post Mon Dec 15, 2008 4:24 pm

Most likely everything in the calipers was cooked beyond it's design specification. The brake fluid has to be changed, definitely. Most likely the seals for the caliper pistons could be damaged too, they require inspection and change. Seals are cheap, lives aren't.
Beer is cheaper than therapy.
DaveKillens
 
Joined: 20 Jan 2005

Post Tue Dec 16, 2008 2:54 am

Scuderia_Russ wrote: Or you could drive slower and brake gentler for longer. :wink:


Please! I haven't much time left. I must go as fast as I can!
Enzo Ferrari was a great man. But he was not a good man. -- Phil Hill
donskar
 
Joined: 3 Feb 2007
Location: Cardboard box, end of Boulevard of Broken Dreams

Post Tue Dec 16, 2008 5:37 am

"Slow down, I'm in a hurry" -- Napoleone Buonaparte -- (or, for mx_tifosi: "Despacio, que voy de prisa")

If Napoleon were an F1 racer, he would have said "Slow on entrance, quick on exit". :)
Ciro
Ciro Pabón
 
Joined: 10 May 2005

Post Tue Dec 16, 2008 12:55 pm

mx_tifosi, the clutch is also a brake and it couples the wheels with an "air pump" :wink:

If you use both, the heat will be shared. Besides, the "air pump" will cool itself while pumping, helping to keep temp down in the clutch.

I have made some stupidities myself in the "Cuesta del Lipan" (Jujy province) to descend 2000 metres in some few kilometres:

Image

There were signs wich claimed "use engine brake" and "descend slow and in 2nd gear" :D
"You need great passion, because everything you do with great pleasure, you do well." -Juan Manuel Fangio

"I have no idols. I admire work, dedication and competence." -Ayrton Senna
Belatti
 
Joined: 10 Jul 2007
Location: Argentina

Post Tue Dec 16, 2008 6:27 pm

Rule No1 :The longer you brake the less time they have to cool down.Brake as hard as possible without loosing control to achieve desired speed and release the brakes!
Rule No 2: Without temperature strips on calipers and brakedisk temp paint you are very unlikely to know what really happened .fresh fluid and rockhard (well bleeded )hydraulics,at least 2/3 of pad thickness ,full thickness disks.
Sanding disks is a no-no.

If your calipers have seen temps above 230°C the seals are toasted ,extended usage above 200 will call for frequent replacing of seals ,better yet more cooling or applying of rule No1 might help as well..

Of course you need to have the proper fluid in the lines ,not old (attracts water -hygroscopic)-heres the weak point of APs racing fluids ,they are not meant for use on the road and degrade quite quickly.

Use a proven pad designed for the intended use.(in case you happen to run high performance pads at racing temps ,don´t be surprised to have a sudden loss of the whole pad in the next braking zone...)
leeds to rule No3: Don´t mess around with safety critical stuff .The information necessary is readily available for example try AP Racings web site and make sure to follow their advice very strictly .And make sure you get the basics right.Dont put your life or worse your drivers, passengers ,or others at risk.
marcush.
 
Joined: 9 Mar 2004

Post Thu Dec 18, 2008 1:48 am

Thank you to everyone for the responses, very helpful indeed. Theres no need to stop giving advice, please continue doing so if theres something new to contribute.

I will be getting new pads in a few days, or when I come back from Mexico in a couple of weeks. Up until now everything has been working fine, no problems, but since I installed them almost a year ago they let off so much dust (continously) that they have 'stained' the front wheels! So I am purchasing new [ceramic] pads, of higher quality no doubt, for the front. And the rears are staying as they are.

Hopefully these new pads will offer better bite during normal driving and let off way less dust. And I'm looking forward to fine-tuning the pedal feel so that it suits my 'assertive' breaking habits, something that I didn't do the previous time around.

And I rarely drive as hard as I mentioned in the first post, but the location called for it and I had to answer the call. I'm sure you guys understand. From now on I'll try to get my dose of speed from the local karting facilities.
Forum guide: read before posting

"You do it, then it's done." - Kimi Räikkönen

Por las buenas soy amigo, por las malas soy campeón.
mx_tifoso
 
Joined: 30 Nov 2006
Location: North America

Post Mon Dec 22, 2008 12:08 pm

marcush. wrote: Without temperature strips on calipers and brakedisk temp paint you are very unlikely to know what really happened.


Ours doesn't kick in until about five hundred degrees so it probably isn't much use for this application.
"Whether you think you can or can't, either way you are right."
-Henry Ford-
Scuderia_Russ
 
Joined: 17 Jan 2004
Location: Motorsport Valley, England.

Post Mon Dec 22, 2008 12:34 pm

Scuderia_Russ wrote:
marcush. wrote: Without temperature strips on calipers and brakedisk temp paint you are very unlikely to know what really happened.


Ours doesn't kick in until about five hundred degrees so it probably isn't much use for this application.

what is this paint?? does it show a certain colour at a certain temperature or something ?
ernos5
 
Joined: 21 May 2008
Location: Flight Level 510

Post Tue Dec 23, 2008 1:39 pm

these colours change when a certain temp is reached ,normally you got green red and orange to start with.
of course these colours are available also for higher temps (tempil stick).Using ceramic brakes or carbon I guess infrared probes to monitor temps realtime are in the budget anyways.
marcush.
 
Joined: 9 Mar 2004

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