Track day brake fade diagnosis?

[stopintime]

Good rotors - Brembo HP full floaters (.15 mm wear)

Somewhere around/under half the pad material left - say 1-2 mm before the (wear indicator?) grooves are gone (Ferrodo sinter, which worked without fade last year)

First track day on fresh Shell 5.1. 
Second and third track day on fresh Castrol React Performance 4.0 (higher boiling points than Shell's 5.1)

More and more fade from 10 minutes until 20 minutes each session - same problem throughout the days.

The flush and bleed were good with a firm lever and plenty of action and feel on both occasions.

Weather conditions similar to last year.
.................................

To my knowledge, everything is the same - except the somewhat reduced pad material thickness.
Is that enough to cause brake fade?

[Ddan]

too much time on the brakes.












I'm no help, I know   

[stopintime]

too much time on the brakes.

I'm no help, I know  

No, but you're funny Dan, so all is good

I try to not drag brakes too much, but there are limits to how little I can get away with

[Ddan]

No, but you're funny Dan, so all is good

I try to not drag brakes too much, but there are limits to how little I can get away with

On the SS track bike I use Motul DOT 4 with the stock 4 pot calipers, Brembo snowflake rotors and a 749 radial pump.  I've never had any fade.

[stopintime]

It'll be interesting to do a visual check on the pads - can sinter pads cook/glaze/xxx ?

[Ddan]

I would assume they could, but you would then just have crap braking, not fading once they got hot.

[BK_856er]

Well, the friction material insulates between the rotor and the caliper piston, so I suppose half thickness could contribute to greater heat transfer to the fluid.  Seems like a lot of meat left to cause an issue.

Are your fluids from new sealed containers (i.e., starting with known dry fluid)?

Have you regularly cleaned the caliper/piston with soap/water and toothbrush?  Maybe there is more hangup/drag than usual and that's inhibiting cooling between braking zones?

BK

[ducpainter]

Have you gotten faster?

That will show weaknesses that weren't apparent previously.

[stopintime]

BK:
The fluids came from sealed containers, but I don't know if they are water-/humidity tight.

I haven't washed the calipers/pistons/seals, but there is no drag at all - they free up instantly.

DP:
Yes and no - there were sessions where I was faster and sessions where I was slower. The fade was more evident in the faster sessions, but also during the (slightly) slower ones.


I can't think of any other suspects than the semi worn pads, but I'm surprised if I need to run almost fresh pads at all track days. I know that racers run fresh pads, but despite riding hard I'm not quite there. I do notice that my braking points are much later than the other red group riders, so my brakes clearly have to work harder. If my level is high enough to require the extra couple of mm pad material - so be it.... 

[ducpainter]

I'm thinking even when you feel slower you're faster than you used to be when you built the bike.

Try a fresh set of properly bedded pads...1/2 or more worn out is not the same as 'almost fresh'.

[koko64]

I had fresh pads and fluid do the same. The previous owner fitted them. I bled the brakes just be sure. Worst brake fade ever!  I changed pads to an organic race compound and used a different brand fluid and problem gone. Some street type sintered pads are prone to fade under track conditions because they are designed for fast warm up and street conditions.
I was suggested to me that some fancy race fluid is more hydroscpic and should be changed regularly as race teams would, but the track day rider may want to use a street type fluid for the bike that sits around.

[ducpainter]

Is he using street pads?

[koko64]

He said Ferrodo sinter, but I'm only guessing what type.

[Howie]

Was the fade symptom the lever going to the grip or a firm lever, but no braking power?  If the lever went soft on you the problem is fluid.  If the lever was firm but the bike didn't want to slow the problem was either the pad material or gas fade.  Gas fade is when brake dust mixes with the hot air between the pad and rotor, working like a dry lubricant.

[koko64]

. Nice rule of thumb that.
My sintered street pads got hot enough to boil the fluid, bringing the lever back to the bar.
Glazed pads are a possibility too, depending on the symptoms.