Where to buy seals etc for AP calipers?

[Shad]

Has anyone recently (or not so recently) bought a rebuild kit for their AP 4-pot calipers? I have the later calipers, with the two push pins for retaining the pads. I'm after seals, pistons and anti-knockback springs. If anyone can recommend a supplier that would be great, cheers

[Sheds Moderator]

Try your local motor factor or failing that a hydraulics supplier. It won't be easy though, as garages no longer do this sort of work, it's not viable. £10 in seals and an hour's labour plays a shiny exchange caliper for £50 or £60, with new bleed nipples that you know work, blast cleaned, bores cleaned, honed, polished as necessary, guaranteed and reliable.

[peterg]

Try AP Racing themselves or www.raceparts.co.uk as they say they can get the rebuild kits

[ruff seven]

Never had much luck getting these either, Circuit Supplies sent me a couple of kits although some right some wrong seals, couldn,t be bothered to pusue it further, would like to know though.

[Shad]

BOSS, quite happy to do the rebuild myself in the garage with my mechanical engineer friend keeping watch. The AP calipers tend to go for a little more than £50-60 either new or rebuilt

 

So this afternoon I had an email conversation with Kevin McDonnell at AP and he's provided answers to my questions as best as possible. The following part numbers are relevant for the CP7605 caliper (quantities per caliper):

 

CP7605-109 Pistons (x4)

CP7605-110 Anti rattle clip (x1)

CP4525-JJ Seal kit (x1)

CP3880-1 Bleed nipple (x2)

 

I forgot to ask about the wear plates, which are listed as CP7605-117 for the CP7600 caliper family for road cars (that's us, annoyingly), and CP7605-116 for the CP7606 race caliper. I'm favouring the latter since the CP7606 is designed for a disc the same thickness as the vented AP disc we use, rather than a 24mm disc for the CP7600 family. But this is mostly conjecture based on information on the AP site.

 

Then we come to the anti-knockback springs. These are of particular interest to me for reasons I've discussed in the past on here. I asked Kevin if CP2667-113 springs (7lb, for pistons greater than 1.375" diameter) would suit the pistons listed above:

 

"No, they are not suitable. Because they are standard road car type calipers the pistons are not machined to accept a spring."

 

Bugger. So then I had a poke around the AP site looking for race calipers with 1.5" diameter pistons that take springs, and I found some. I cheekily asked if the smaller CP3636-107 piston for the CP5090 caliper would fit or if it would be too deep:

 

"No, that piston is too long

 

CP7605-109 1.5” x 24,85mm long

CP3636-107 1.5” x 30,20mm long

CP3228-103 1.5” x 25,70mm long, this is the nearest that we have available that will run with springs.

 

You must check that there is enough space available to run the longer spring if you decide to try them."

 

Based on this, I'm probably going to take a punt on the CP3228-103 pistons and the lighter 4lb springs (CP2667-105) and see if it fits ok. I have no idea how significant 0.85mm is going to be in the caliper. It might be a deal breaker, or it might mean that I'd need to take 0.85mm of pad material from new pads. Or it might only be a problem with the heavier springs (7lb and 9lb). The alternative is to go with the correct pistons and have them machined to accept a spring. They should look like this:

 

http://www.eliseparts.com/img/up//d1/11-d0299.jpg

 

Those are the springs and pistons used in the rear AP calipers or the front calipers on Elise/Exige (same caliper for all intents and purposes). Getting the dimensions right for machining could be tricky, I don't know. Could be another avenue to explore though.

 

So there we have it, some actual information (and some conjecture!). Next step is to speak to some of the distributors mentioned and others listed by AP and get some prices and go from there

[Sheds Moderator]

Ah yes, I missed the AP bit, forgot that these are a specialist part. My comments apply to standard 7 fronts (Triumph) amd rears (Sierra 4x4 or XR4 or whichever it is) which are straighforward exchange units as per tintops. I've tried to get repair kits for tintops, it's a waste of time these days and a shame because as you say it's not complex to fit. Good news that AP will supply all the parts though.

[Rob Walker]

I took the springs out of my AP four pots, the pads were dragging all the time causing the pads to glaze up.

[Shad]

Interesting Rob... you must have the earlier silver calipers then? Do you know what lb the springs were?

[Hanns Per]

I bought a AP clutch master cylinder repair kit from

interspares

and received very good service

Hanns Per