Soft brake pedal

[braddo]

I recently acquired a 90s K-series Caterham and after a couple of track days the brake pedal was going a bit soft, so a well known specialist changed the brake fluid. This brought the firmness back to the pedal but by the afternoon of the next track day the pedal was softening again.

Might this be a case of the system needing bleeding? Can a Seven ever boil fluid?!

The braking system is standard and the tyres R888Rs. I don't know what pads the car has.

Any advice gratefully received...

[DCL]

It depends what you mean by soft - if you mean long (ie travel increases) and it still feels able to stop the car, then this is probably normal. Upgrading to the high effort pedal, or even a AP race master cylinder will help.

If it is spongy (and stays that way) then you need to look at bleeding the brakes again. If that happens repeatably then there may be air getting into the system from a faulty seal somewhere. Changing pads may also be a good idea, even if they look OK, as pads can give a spongy response if they have been abused, particularly the rear Sierra standard issue pads. It is highly unlikely the fluid is anywhere near boiling.

Edited by DCL on Thursday 11th July 15:56

[V7SLR]

It might sound a stupid question, but are you applying the handbrake between sessions or when not actually on the track?

[braddo]

V7SLR said:

It might sound a stupid question, but are you applying the handbrake between sessions or when not actually on the track?

Never - that was one of the good tips I got on my very first track day.

I would say the pedal feels spongy. I think I'll look at replacing the brake pads and go from there, thanks.

[HustleRussell]

Is it definitely a soft pedal or are you just experiencing pad knock back?

[braddo]

HustleRussell said:

Is it definitely a soft pedal or are you just experiencing pad knock back?

Sorry I don't know what pad knock back is?

The only way I can describe it is it's like other cars I have taken on track days where the pedal feels a bit soft and ineffective when you first go back out on track after earlier sessions. Usually the brakes will warm up and go back to normal. And then once the track day is over they also go back to normal. However, the Caterham's brakes have kept that first lap feeling of the pedal being a bit soft and spongy. From my Elise and other Caterhams the pedal should be a lot firmer with shorter travel.