Brakes after a track day

[kula]

I've discovered something annoying.

After a hard day at wakefield, everything is fine, except for the rear brakes.
How do i know this? I parked my car last night on my steepish driveway, and it rolled back after the handbrake was applied.

now I'm running the following setup:

F: OEM NA8 discs
NA8 brackets
recoed NA6 calipers

R: OEM NA8 Discs
new NA8 calipers

Hawk HP+ pads,
Goodridge braided lines on all 4 corners,
Castrol SRF fluid.

Front brakes seem fine, maybe a touch lower than usual,
but the rears, on the handbrake are next to useless
having recently replaces the entire rear brake system, my handbrake was perfect, it would hold on any hill, and this just annoys me.

could be fluid?
or do i have to readjust the rear calipers? (what a crap system)
or bleed em?

it happened after a previous WP day when I have NA6 rear brakes with bendix pads too.

The handbrake was never applied at the track.

[bruce]

Probably not adjusted properly at the back (it is only a cable).

[kula]

they were 100% fine on wednesday,
128 laps of wakefield on thursday zero handbrake usage,
crap hand brake on friday.

[Matty]

DriftFury once told me that high temp bitey pads can have very poor static friction coefficients. Could be the cause?

Check your rear calipers aren't seizing though...

[16bit]

DriftFury once told me that high temp bitey pads can have very poor static friction coefficients. Could be the cause?

Check your rear calipers aren't seizing though...

to add to this if the pads are glazed from the track work the static friction would be even worse.

[manga_blue]

Adjusted your handbrake lately? The cable stretches over time. It's just a screw between the handbrake lever and the tunnel under the plastic trim. Should be full on after 5-7 clicks.

[Brad]

How are you running NA6 calipers on NA8 rotors? The swept area is totally different?

I wouldn't be surprised if you've glazed the pads on the rear. HP+'s are not as good as normal road pads for cold temp friction, hence the handbrake not working as well as it should.

[Fatty]

somebody had a thread recently (i think it was sheck) about modding the rear brackets or cailpers or something, to increease the effectiveness of the handbrake. in his case, he wanted it for drift, but it should apply to you regardless. i recall it involved an angle grinder and welder, so not for the faint hearted, but worth thinking about.

[CT]

DriftFury once told me that high temp bitey pads can have very poor static friction coefficients. Could be the cause?

Check your rear calipers aren't seizing though...

Absolutely true - race pads will not work when at normal road temps and the rears do so little work they may not even really be getting hot at all. HP+ pads are not that high in co-efficient though so they should be OK. My guess is they are not adjusting properly. I've never had to adjust rear calipers on the race cars - and the SE's handbrake actualy works!

[Rob E]

How are you running NA6 calipers on NA8 rotors? The swept area is totally different?

He obviously has the NA8 Caliper brackets. This is a very common and cheap upgrade in the states, here its harder to get the NA8 brackets at a good price.

[Matty]

DriftFury once told me that high temp bitey pads can have very poor static friction coefficients. Could be the cause?

Check your rear calipers aren't seizing though...

Absolutely true - race pads will not work when at normal road temps and the rears do so little work they may not even really be getting hot at all. HP+ pads are not that high in co-efficient though so they should be OK. My guess is they are not adjusting properly. I've never had to adjust rear calipers on the race cars - and the SE's handbrake actualy works!

It wasn't a hot vs cold issue he talked about. It was a sliding vs static CoF issue.

[kula]

seems a little better now..

i reckon its glazing or fluid...

might bleed em next week..

but its not cable..
like i said, wednesday its 100% fine,
thursday track day,
friday its crap.

[Brad]

Won't the fact you are using the handbrake all but remove the fluid from the equation?

[kula]

not sure..

the cable pushes the piston, so if there is air in the system it first has to compress the air?

[zoomzoom]

On the back of my nb8b calipers there is a adjuster screw which needs to be woud in as the pads wear, 128 laps should be enough to cause a bit of wear, so I would take a look ad see, I am pretty sure they have this adjuster screw. It is a allen key hidden behind a hex head bolt(similar to that holding the line in) it just needs to be wound i then backed off a touch and this will make the handbrake start at the right point.