Improving brake feel with AP calipers

[Shad]

I've come to the Caterham from essentially a race-spec Honda with fantastic brakes. I had Wilwood calipers with Ferodo DS2500 pads and high-temp fluid and the pedal was always firm and consistent no matter how hard I pushed the car.

 

I was hoping for similar from the AP setup on the Caterham, but so far it's not delivering. On the road they're ok but then I never push that hard. On track however they are very inconsistent. Pedal travel varies a lot - starting a session it will be long, then it seems to come back a bit as everything warms up, then it will get longer again as the session progresses. They also feel quite soft, I don't get that hard bite that I'm used to.

 

So I'm just wondering what I could try to improve things. It's been suggested that the pads might be glazing, so that's one possibility - maybe grooved discs or different pads would help that? Also how about a fluid change to high-temp fluid? I'm know that Caterham offer a couple of different pads for the AP calipers, but as they are a standard caliper do companies such as Ferodo or Mintex also offer pads?

 

Comments appreciated

[F355GTS]

Simon

 

For mixed track and road I'd consider Mintex 1155, it's likely the problem that you are seeing is the rear std brakes overheating, mine used to do this after a spirited track session the pedal would be very soft then come back after the first few laps of the next, I now run uprated rears, the fronts can suffer from pad knock back too particularly if there's any bearing play or disc run out. I use Castrol SRF fluid, expensive but does the business.

 

I'd guess the first thing is to see which pads you have installed?

 

Mark

[Slipper man]

I have the same issue with mine (race master cylinder, AP fronts, standard rear). The long pedal at the start s fixed by pulling the handbrake a few times before you start, but the pedal feel is never as good as I would like. I have bled the brakes many times and am sure it isn't air in the system. A friend has an early Superlight with apparantly identical brake setup and he has amazing pedal feel. I have tried changing rear pads, with no effect and don't know what to try next.

[Shad]

Mark, Mintex on the rears? I did notice when loading the trailer at the end of the day there was a lot of heat still around the rear wheels. I'll try and get the pads out and find out what I've got (front and rear).

 

Glad it's not just me anyway!!

 

I don't think I have a race master cylinder... I'm guessing that would just reduce the pedal travel rather than any other significant gains?

[Paul Deslandes]

An earlier discussion on here included advice on bleeding the rear callipers (Mark contributed) which I'm going to try as I have the same problem. I've de glazed the disks and cleaned the pads (Pagids) after talking to John at Performance braking and they're still not as good as they should be.

 

If you are looking at changing the front pads have a look in the archive about having the disks faced so that you can use a wider pad on the AP fronts to get a larger contact area. If the disks are new and/or have no wear step then you can go straight for the wider pad. A chat with John is very worthwhile. Performance Braking 01600 713117

 

 

[F355GTS]

Simon

 

depends what's in the front, ideally you want a matched set or something slightly less at the rear. The BDR (Green one ) has 1155's in with a std Master cylinder and big front brakes, works perfectly on the road and as far as I could see the other Week very well on track too, maybe have a drive of it at Abingdon on 7th if you are there?

 

Mark

[millsn]

I would say to change your fluid and bleed the whole system, especial attention to the rear calipers which are a bugger. If the fluid has been boiled it wil lnever be the same again. Not sure about the APs but my Alcons have two bleed points for the fronts, so when bleeding the fronts bleed both points starting inboard.

Lastly, I understand that the rear calipers themselves are a culprit in a less than rock solid feel which is why there is a rear AP calipers to replace them. Not sure if you have that caliper of just the fronts?

 

Nigel Mills - 2.0 zetec

[Shad]

Thanks chaps, been reading up on the potential issues with rear caliper bleeding so will bear that in mind. Unfortunately I don't think I can get to Abingdon Mark (bit late to book holiday now) but thanks for the offer anyway! I'll get the pads out one evening this week and go from there

[Rob Walker]

Another thing to look at is the rear wheel bearings. My rear wheel bearings are getting shot and rear pad knock off is becoming a problem.

[Alex Wong1697456877]

Race master cylinder gives a much more positive feel and shorter pedal travel. Still has that initial soft bit of travel though. Best feeling brakes I've tried were on a standard C reg Live axle car, although actual braking power was not as good as mine. SRF brake fluid certainly improved things - I used to have problems with the pedal going soft using normal dot4 fluid.

 

Edited by - Alex Wong on 26 Nov 2007 10:11:58

[Shad]

Finally got around to taking the front pads out for a gander:

 

Markings on friction material

'L' stamped on backing

 

Any ideas which brand they are? I have Lucas pads on the back which were fitted by Caterham at the last service, according to the invoice.

[F355GTS]

Simon

 

they are mintex but their std road pads as fitted at the factory,1202 or 1203 whichever it says, time for a change to something more substantial, for the price buy a set of 1155's if you don't get on with them they won't have broken the bank but I believe they'll suit your mix of use

 

Mark

[Shad]

Thanks Mark. Just been trying to work out which calipers I have, think they are the most recent design, the CP2340 with the pins holding the pads in rather than a single bar as with the earlier calipers. Anyway, £72.71 plus the vat from Demon Thieves, not too bad.

 

Worth putting 1144s in the rear at the same time?

[F355GTS]

Yes rears as well

 

Mark