AP Racing breaks
Discussion
Are there any brakes which are less prone to catching on fire than the standard cerbera AP racing breaks? I drive quite aggressively on the track and my brakes caught on fire this weekend - when the fluid boiled I had a total failure (fortunately Id managed to slow down before they failed!!)
racing breaks - doh, here was me expecting a thread about competitive driving holidays... Seriously though, it ain't the fault of the AP kit...but back in the mists of time when I had the Cerb I had the same problem on track days, but did eventually solve it. So, 1) got decent fluid - Dot 5.1 or Dot 4 super? As the fluid you have now has boiled, it needs changing. 2) Decent pads? I found EBC little better than cardboard, Mintex 1144 better, but Ferodo DS3000 the best. Not great when cold and v.noisy, but the realy stop the car when hot without huge pedal effort. 3) Got thickish pads? If they're worn thin you'll transmit more heat into the caliper and then fluid. 4) Got enough air? There's not a hooge amount of space in the wheelarches of a cerb. If the car is lowered from standard this is reduced even more. I went from no-boil to always-boil just by dopping the car an inch or so! I put some little 'scoops' on the front of the lower wishbones to direct more air onto the disk. You can of course buy proper duct kits.
With the above, I could run track days with the brakes just running at a nice temp - even at Knockhill which is a brake-killer - with only stops for fuel or when the tyres went off.
and for anyone else who hasn't had total brake failure, note the warning signs and understand what happens. Lots of folks think that once the brake goes spongy it'll just get progressively worse - wrong! They go 100%, typically 2 corners later...as I found out. Theory goes that obviously the fluid is reaching boiling point, and its actually boiling in a few 'hot spots'. These small bubbles need to be compressed to make the brake work - hence the first sign of spongyness. YOU MUST STOP AT THIS POINT. Otherwise, the next time you press the pedal the bubbles get compressed and the brakes continue to appear to work. However, the heat source (the braking effort) has not been removed so the fluid gets more heat in it. But as you're on the brakes and the fluid is pressurised it won't 'boil'. So, like a pressure-cooker, the fluid is now forced over its boiling point under pressure.
Now when you loft off the pedal the pressure is removed from the system - the fluid, now over its boiling point - instantly boils up all over the place. You now have loads of bubbles in the system that will not be compessed on a single (or even multiple) pumps of the pedal. You have total brake failure.
So, I don't know how your failure came about, but the typical scenario is:
Corner 1 - notice spongy pedal...this is the warning
Corner 2 - notice much longer travel, but still working, apparently...the point of no return
Corner 3 - No brakes!
WB
There is of course a theory (only a theory mind) that says that far too many track drivers use their brakes far too hard as they do not carry enough speed into the corner.
I am sure that if you have done a few track days now then this is not the case but additionally all brake/clutch fluids should be regularly completely chnaged every 2 years anyhow; it is on most service schedules. This is because it is hygroscopic and absorbs moisture thru the cylinder breather hole, this then becomes vaopur (steam) when the fluid gets hot and you lose the pedal etc etc
Hope this helps, losing brakes is a nasty scare even without a fire!
I am sure that if you have done a few track days now then this is not the case but additionally all brake/clutch fluids should be regularly completely chnaged every 2 years anyhow; it is on most service schedules. This is because it is hygroscopic and absorbs moisture thru the cylinder breather hole, this then becomes vaopur (steam) when the fluid gets hot and you lose the pedal etc etc
Hope this helps, losing brakes is a nasty scare even without a fire!
tvrolet said:
1) got decent fluid - Dot 5.1 or Dot 4 super?
2) Ferodo DS3000 the best. Not great when cold and v.noisy, but the realy stop the car when hot without huge pedal effort.
3) Got thickish pads? If they're worn thin you'll transmit more heat into the caliper and then fluid.
4) Got enough air? There's not a hooge amount of space in the wheelarches of a cerb. If the car is lowered from standard this is reduced even more. I put some little 'scoops' on the front of the lower wishbones to direct more air onto the disk.
Which should I ask the dealer to use then, Dot 5.1 or Dot 4 super?
re: Ferodo DS3000 - does anyone else use these? 99.95% of my driving is off the track as the cerb is my daily driver. Id really rather not have loud brakes - You're not referring to sqeualing/squeaking, are you?
My pads were worn. I didnt know (makes sense) this would exacerbate the problem. I dont have scoops for cooling either, but will look into it. I assume this isnt a costly mod?
The track: There is only one 'fast' 70mph corner which I take on the limit, backend light, tyres squealing etc. All the other corners are *very tight* very narrow 90+ degree 10mph corners usually preceeded by a straight (TRL coned-out course in crowthorne) so it is necessary to scrubb off 90% of your speed pretty much in a straight line then turn into the corner whilst the nose of the car has been forced down when max grip has been apportioned to the front, and repeat.
My Scenario was:
Corner 3-5 - Girlfriend thought she couldnt find the brake pedal when she was driving, she is new to the cerb so I put it down to inexperience/nerves/whatever as she didnt explain. We then came off as she had finished her laps.
Corner 6-8: The pedal felt spongey (before I pulled out) but I was told so long as I had brakes, it would be fine(!) and to get back on the track. So, taking that advice, off I went...
Corner 9-ish - No brakes! They just went, very suddenly, and as you said were literally 100% gone very shortly after the problem had started.
I tried to flag someone down whilst driving past him asking him to help stop the car, he didnt twig, so I had to jump/fall out the car whilst it was moving (not easy in cerbie seating position) run around to the front and stop the cerb with my hands (in front of everyone
) Thanks for the post, its been very helpful. Im just thankful they failed when they did. 5 seconds earlier and Id have plowed into half a dozen people. 25 seconds earlier and Id have hit a barrier head on at 70mph. Just feeling a bit pissed off having followed the advice to ignore the problem. And lucky to have avoided an accident.
Max Attacker said:This track/excercise is a little different. The point being to gain max speed, then brake in a straight line to take tight/sharp turn at a very low speed. Others cooked their brakes, but I was the only one with a total failure (I was also the most aggressive driver, so they said
There is of course a theory (only a theory mind) that says that far too many track drivers use their brakes far too hard as they do not carry enough speed into the corner.
Hope this helps, losing brakes is a nasty scare even without a fire!
) But yes, very very scary, and with a little knowlege or proper advice, totally avoidable(!)No handbrake?
If you really have no brakes at all then you can stop the car by switching the ignition off, you don't get a great deal of decelleration but if you're at walking speed it'll stop you in a few yards.
By the way, the person who told you to go out with a suspected brake problem was an idiot.
>> Edited by GreenV8S on Monday 24th April 13:08
If you really have no brakes at all then you can stop the car by switching the ignition off, you don't get a great deal of decelleration but if you're at walking speed it'll stop you in a few yards.
By the way, the person who told you to go out with a suspected brake problem was an idiot.
>> Edited by GreenV8S on Monday 24th April 13:08
ehasler said:I was doing cooling laps with everyone else before they failed. I just... didnt fully appreciate the benefits of doing so until after they had failed
Rob,
It's a bit late now, but next time try doing a slow cooling down lap at the end of each session. It will cool the brakes down much more effectively than coming straight in after a run and leaving the car sitting for 30 minutes.
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