Spongy brake pedal

[TheManAlive]

On my last few track days i have noticed that the brake pedal quickly becomes spongy. Braking isnt denigrated, the pedal just has a bit more travel and the biting point on the brakes isnt very firm (if thatmakes any sense)

I have bled the brakes repeatedly, also with one end up in the air to shift any bubble etc. Changed the brake fluid to a race one, but still happens. Pads are fine, rears only a year and half old, fronts about eight months.

Any ideas on what else i can try. As is said, its not effecting performance as much as confidence.

 

I should add, i dont think its overheating cause the problem does not go away over lunch breaks of a while in the pits.

 

Edited by - Themanalive on 16 Nov 2009 08:21:35

[Paul Deslandes]

Almost certainly air in the system and changing the fluid to a different type won't help.

 

What car and brakes? If you have the Caterham 'Big Brake' kit or other 4 pot system on the front, each calliper has two bleed nipples, both at the top on either half, and the inner one is often forgotten 😳

 

Also the rears were not designed to be fitted horizontally on a Sierra so the air needs a bit of help getting out. Often this can be by simply lightly tapping the calliper with a hammer with the bleed nipple open and usual bleed pressure applied from the pedal or easibleed. This will free the bubbles from the wall of the fluid way. Alternatively, carefully undo the calliper from the upright and tilt the calliper so that the nipple is uppermost. If you have rigid brake pipes rather than flexible, this needs to be done with care so as not to kink or damage the pipes but can be done if careful. As always, an assistant can make this job a lot easier 😬

 

Be careful when removing the callipers not to allow the pistons and pads to close up. Block them with a disk-thickness piece of wood or don't allow the calliper to come completely off the disk, otherwise you'll need a piston wind-back tool to get them home again as they cannot simply be pushed back into the cylinders.

 

Paul

 

 

[Iain A]

Had a similar problem with the Rally car recently, turned out to be a couple of things.

 

First was unevenly worn disks which meant that things were having to flex as the pads were squeezed into the disks.

 

Second.. worn brake pads often feel rubbish. Put in a new set (after you have had your disks skimmed.. watch for min thickness)

 

Then look closely as you apply brake pressure... if things are bending and moving around or the pads don't contact the disk surface squarely.. work out why. All the flexing makes the brake pedal feel spongy.

All the above assumes that your brake fluid is in good condition.. makes a big difference.

 

Good luck

 

One of the Duratectives

[MADMALC]

How old are the flexible pipes.

Get someone to pump the pedal slowly but very firmly while you put your hand round the tubes. Feel for any expansion all along the pipes.

Just an idea

 

S7MAD

[Gridgway]

When I had this, I found that changing the pedal from a low ratio to a high ratio pedal did the trick. There was nothing wrong with the brakes, just that the feel of the pedal going a long way put me off. I did all the bleeding things you have done and it made no difference at all!

 

Change the pedal, all nice.

 

Graham

[TheManAlive]

Brakes are standard caterham ones on a 2008 Roadsport SV. I would hope the flexible hoses etc would still be in good condition after only a year and a bit. I will have a look though. Same goes for wear on the pads and discs - whilst i drive enthusiastically on track i would hope there would be plenty of life in them!

 

I will give it another go on the bleeding, tapping them as i do so. Hopefully this will sort it out. I just want to have brakes that when i stand on them they feel solid! As they are i love how late and hard i can brake (that hairpins on bedford gt are great for that), i just want a little more confidence in them.

 

 

[TobyCoulson]

I do have a set of calipers, discs, mintex 1144 pads and hoses from my 2008 Roadsport SV to go on the for sale forum if you are interested.

[TheManAlive]

Thats the setup i already have! What are you changing to?

[TobyCoulson]

Hi spec 4 pot callipers with 10" grooved discs and Mintex1144 pads. Much better progressive feel and bite.

I suggested you might want mine if yours had worn too much and wanted to keep the same set up for a very cheap price.

 

 

 

Edited by - TobyCoulson on 17 Nov 2009 08:35:32

[k.russell]

similar problem TMA on my 92 HPC, and went a similar route with the bleeding and fluid, pads, finally bit the bullet and sent for a set of cc uprated fronts before the v.a.t goes up in Jan. hoping it will improve my set up.

 

Kevin R

 

black(but sometimes orange)-ali HPC

here

[Gridgway]

have they always been like this?

If the brakes work ok but you just want them to feel firmer, change the pedal!

Graham

[Manxseven]

 

I have a High ratio pedal for sale,

see for sale section.

 

Simon

 

---

Caterham BEC here

[charlie_pank]

I'm also on Mintex 1144 on the fronts. My brakes feel fairly 'wooden' under normal driving where they never get any heat into them. They give more feel when the pads are warmed up on track. I'm sure there's nothing wrong with them at all in my case, maybe yours just do the same if your braking is not being copromised by it?

 

back here because I want to be.

[Adrian Williams]

When re-bleeding get someone to pull the handbrake up and down while bleeding the rears, another way to make sure no trapped air. Rears can be a pain front 4 pots are a delight to bleed.

 

Adrian