Bob Simon Posted March 4, 2005 Share Posted March 4, 2005 My car is fitted with uprated rear two pot AP calipers, no handbrake. (well, there are some sort of handbrake calipers in a box buried in my garage) The AP calipers are the bling-bling versions with the fancy yellow Caterham badges embedded in them. I need to replace a rear disc after the pad delaminated and toasted it. The part number I find is: 77183A Rear Disc Assembly - Uprated (92-99) I order this. Caterham sends me a disc that is 10mm thick. It won't fit through the slot of the one piece caliper. The original discs are only 8mm thick. Does anybody with this setup know what part number I really need for this disc? -Bob 95 HPC VX Link to comment Share on other sites More sharing options...
Chelspeed Posted March 5, 2005 Share Posted March 5, 2005 This is the "race" rear brake kit using the solid disc (ie not the "uprated" race rear brake kit which uses a vented rear disc) and the 2 pot radial mount alloy rear calipers and different ears? If so then it uses the standard front disc but fitted on the back with a big thick black alloy spacer ring between the back of the hub and the disc. The spacer brings it back towards the centre of the car to suit the opening in the new style caliper. The caliper is an AP 2 pot, part no CP3677, and the AP catalogue says it wants a 9.7mm disc. So sounds like you have the right disc. What exactly fouls? Does the disc hit the caliper body? Have you still got the spacer fitted? Is the disc in the centre of the caliper "hole" and just too thick or does it foul just one side (offset problem). You have pushed the pads back (sorry, clutching at straws...)? Can you post pictures? Link to comment Share on other sites More sharing options...
Chelspeed Posted March 5, 2005 Share Posted March 5, 2005 Pictures of caliper here AP Racing. Are these what you have (picture shows view from the back, fronts are smooth one piece)? Pick Rally rear, 2 pot, CP3677. Says 9.5mm here. Can't think of anything else that could be wrong. Quite possible someone has skimmed your old discs down to 8mm to save weight, mine are. But even then they can't have thinned the calipers down to suit because they are one piece so don't come apart. I'm concerned about the description though "77183A Rear Disc Assembly - Uprated (92-99)". As I said before the race rear brakes I have use the standard front disc but mounted differently. So why is it described as Uprated? The only uprated rear disc I have heard of is the vented one brought in late 90's when the racers started overheating them, not available from 92 though. Plus I'm sure you'd have noticed if the new one was vented and the old not....... Link to comment Share on other sites More sharing options...
Bob Simon Posted March 5, 2005 Author Share Posted March 5, 2005 Thanks for your help! That's the caliper! (CP3677) The other side of the caliper has the yellow enameled Caterham badge set into the casting on the piston centreline. BTW...The disc is 9mm, my mistake. By "uprated" , I meant that the car was fitted with the optional AP calipers and discs and not the standard Ford Sierra parts. The car was a knocked down kit as delivered from Caterham. There were some tiny alloy cable operated calipers and brackets in the boxes that evidently are supposed to be used as an emergency brake. These and the under-dash "Johnson bar" were not installed as the additional ballast was not required. The slot in the caliper itself is too small to take a standard 10mm front rotor. The slot in the casting is wide enough at the inner diameter, but tapers a bit smaller towards the outer diameter. When you snug the caliper bolts down on a standard disc, it fouls the inner and outer edges of the disc. I have the black anodized spacers you mentioned in this setup. I asked the former owner if the rotors were modified. He said they were installed right out of the kit box. One interesting feature that might help identify the discs is a 6mm wide by 3mm deep groove around the periphery of them. It doesn't seem to have any function, however no other Caterham disks I've seen have this groove. The discs Caterham sent me are on this list here The vin on my chassis is SDKRDKHVXQxxxxxxx which I see makes it a 1994 HPC, not 95. I'm going to take some snapshots this afternoon and post them. If I still can't find the appropriate discs, I guess it's time to have some standard ones turned down. ☹️ -Bob 95 HPC VX Link to comment Share on other sites More sharing options...
Rob Walker Posted March 5, 2005 Share Posted March 5, 2005 The standard solid discs will not fit as they differ in that the uprated has a machined undercut in the inner face of the flange that accomadates the black anodised ali spacer. It would be possible to have this machined from a stock disc if you have the wll and the equipment. Link to comment Share on other sites More sharing options...
Bob Simon Posted March 5, 2005 Author Share Posted March 5, 2005 Hi Rob, The plot thickens! The "77183A Rear Disc Assembly - Uprated (92-99)" I recieved from Caterham has the recess for the spacer around the mounting bolts as you describe. It's just too fat. piccys soon... -Bob 94 HPC VX Link to comment Share on other sites More sharing options...
Chelspeed Posted March 5, 2005 Share Posted March 5, 2005 Having a recess machined in the back face for the spacer to seat explains the word uprated in the description then. Still not sure why a 9mm disc won't fit a caliper that AP say will take a 9.7mm disc. Nor why the new ones are different thickness to the old ones. Taken a verinear to mine and there's 12mm or so gap all along the disc path. Totally confused. Link to comment Share on other sites More sharing options...
Bob Simon Posted March 5, 2005 Author Share Posted March 5, 2005 OK! I have pics now. here here Pics show original 8mm disc. You can see the groove in the periphery of the disc. It seems the fatter 10mm discs only foul the *outside* of the caliper. Since the caliper cocks over, I thought the slot was too narrow. It is not. The problem is the spacing. The new discs will work if I add about 3mm to the anodized spacer to move the disc into the centre of the caliper slot. Unfortunately, it looks as though I'll have to turn up a new pair of spacers. I don't think a shim would keep the disc concentric. ☹️ -Bob 94 HPC VX Link to comment Share on other sites More sharing options...
Chelspeed Posted March 6, 2005 Share Posted March 6, 2005 All looks right. Nothing to add sorry. Guess you either bother the Parts Dept as to why they are different or mod them yourself. If skimming one or both of the faces will get them to fit I'd do this rather than mod the spacers as that way you get lighter discs for free! Wouldn't go thinner than 8mm though. Link to comment Share on other sites More sharing options...
Bob Simon Posted March 6, 2005 Author Share Posted March 6, 2005 If skimming one or both of the faces will get them to fit I'd do this rather than mod the spacers as that way you get lighter discs for free! Good thought! I wouldn't have to manufacture spacers as well. -Bob 94 HPC VX Link to comment Share on other sites More sharing options...
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