brake fade!

[mak]

ok! i've completed several track days's with my car and the brakes to my astonishment have never once let me down, due to worn pads and disc's i've replaced both and fitted mintex fast road pads, i've now got severe brake fade, just braking from 100-30 is enough to cause the brakes to go dead, the brake fluid has been changed and the calipers are in no way way seized, help! i've got a track day booked for the 6th of may and i might as well forget it with these brakes.

[sparkythecat]

How are your flexible hoses?

If new pads are harder and brakes are running hotter, perhaps hot fluid could be softening the hoses and causing them to balloon.

[shpub]

You did clean the discs with brake cleaner to get rid of the protective finish?
You will also need to follow the bedding in process as well before the brakes will come up to standard.
The procedures come with the pads and are examples are also included in the bible.

[GreenV8S]

shpub said:

You will also need to follow the bedding in process

What he said.

[trackcar]

mak said:

just braking from 100-30 is enough to cause the brakes to go dead,

even an incorrect bedding process wouldn't cause this sort of situation .. I would seriously take the pads out and replace them. I use mintex all teh time because they're fantastic pads, never had this situation though even on the very cheapest of pads, methinks there's a fundamental problem.

[mak]

yes the discs where cleaned and fitted properly as where the new pads bed in correctly, the hoses seem fine but considering the old worn brakes did a fantastic job i'm a little perplex'd as to the problem, surley i've not been sold the cheap pads in the expensive box?

[mak]

forgot to say i've had rear pads fitted by a garage, not sure wot pads they put in but is it possible the fade is from the rears? Under hard braking the brake pedal does not go spundg'y nor does it go to the floor it just reaches a normall stop before feeling like i'm using to blocks of wood to slow the car down instead of grippy pads, dont get me wrong the brakes are fine for normall use pulling the car up as they should but start pushing on and forget it. cheers for all your reply's. steve.

[trackcar]

Sounds like it could be pad gassing .. where the resin that bonds the pad together gets hot enough to vapourise .. it's the reason they give you grooves in pad and grooved discs .. it lets the pad gasses escape otherwise you end up with the pad surface riding on a cushion of it's own resin vapour .. result is a rock hard pedal with no retardation.

Might be worth checking those pads .. and see if they have grooves in to let the gas out, and what make they've fitted aswell to make sure they're up to the job.

To be fair the fronts should be doing most of the work and they're the mintex ones you say? anyway investigate further cos it doesn't sound a particularly friendly set-up you have there at the moment.

[GreenV8S]

trackcar said:

mak said: just braking from 100-30 is enough to cause the brakes to go dead, even an incorrect bedding process wouldn't cause this sort of situation

I think it could; pads that haven't been bedded in properly can 'go off' with relatively small amounts of heat. I don't know why, but I imagine it being a combination of local vaiations in contact pressure causing local temperature variations, and fresh pad material generating gas at lower temperatures than normal. Bedding pads in properly is important in my experience. If the calipers are worn this can be a particular problem, in fact when the original rear calipers were very worn on mine they put a distinct angle on the pads under heavy braking. It took me a couple of sessions to wear the pads to the required angle on the track, and afterwards the brakes would be pretty rubbish under light use until the angle had worn off again.

[zippee]

mak said:

yes the discs where cleaned and fitted properly as where the new pads bed in correctly, the hoses seem fine but considering the old worn brakes did a fantastic job i'm a little perplex'd as to the problem, surley i've not been sold the cheap pads in the expensive box?

I had exactly the same thing today on my first track day, running 12 groove black diamond discs and predator pads and have had them on the car since mid last year. On the road in normal use the stopping power is fantastic but on track today on about my 4th lap braking very hard for a chicane and the car just didn't want to slow. Fluid was also changed at the last service (1 month ago) for 5.1. Drove my mates Elise with std brakes and it felt amazing compared to mine.