Jason Plato Posted February 21, 2001 Share Posted February 21, 2001 Has anyone else , who has recently converted / upgraded to the AP front brake upgrade ( black calipers ) with vented discs experienced a slight vibration through the pedal - not the steering , when under braking ?? . During the Pembrey trackday last weekend 3 cars were suffering the same problem , it didnt appear to matter if the brakes were hot or cold or at any particular speed . I have the older style (grey ) AP fronts and they are fine . The sensation is like as if the the disc is warped however the runout was measured as less than 0.2mm . Any suggestions or experience appreciated . Ta Dave Link to comment Share on other sites More sharing options...
StewartG Posted February 21, 2001 Share Posted February 21, 2001 It is possible to fit these calipers so that they foul the discs. You must have a spacer washer between the caliper and the lugs they bolt to on the uprights. If you don't the inner corner of the disc rubs on the caliper and scores the disc. Could this be the problem. Initially I was tempted to delete the spacer washers as the standard bolts are a bit short for use with these calipers, luckily I noticed before too much damage was done. Link to comment Share on other sites More sharing options...
Number Six Posted February 21, 2001 Share Posted February 21, 2001 I believe James Whiting mentions something about this, which is why his Alcon's are an easy fit. Andy Link to comment Share on other sites More sharing options...
StewartG Posted February 21, 2001 Share Posted February 21, 2001 His Alcon's are an easy fit because they use the standard discs which are thinner and smaller in diameter so more clearance all round. Link to comment Share on other sites More sharing options...
Number Six Posted February 21, 2001 Share Posted February 21, 2001 Lighter, less unsprung weight, cheaper. I'm not sure about relative stopping power to AP's --- anyone know? Andy Link to comment Share on other sites More sharing options...
R2D2 Posted February 21, 2001 Share Posted February 21, 2001 0.2mm is a fairly horrid amount of disc runout and I would think some remedial work would be needed. In old money .003inches was considered as a maximum value and .2mm is 0.008inches I would ceratinly re-check the run out and make sure that the wheel bearings are correctly adjusted. If it is 0.2mm you may need to re-face or replace the discs. Is it the disc which has a problem or the hub? I think it would be worth checking the discs with a micrometer to see id the thickness changes. Link to comment Share on other sites More sharing options...
StewartG Posted February 23, 2001 Share Posted February 23, 2001 APs use bigger caliper pistons with the same pads working on a bigger diameter discs so I assume they have more stopping power. The standard discs are significantly lighter and the Alcons work with the standard master cylinder, you pays yer money..... Link to comment Share on other sites More sharing options...
Jason Plato Posted February 23, 2001 Author Share Posted February 23, 2001 relative "stopping power" of different braking systems is irrelavent , as the maximum retardation is governed by the grip of the tyres !! . Try braking on slicks vs RE720's !!! So has noone else experienced this vibration then ??? .... or are you lot just not braking hard enough ??? [;E] Dave Link to comment Share on other sites More sharing options...
Number Six Posted February 23, 2001 Share Posted February 23, 2001 "relative "stopping power" of different braking systems is irrelavent , as the maximum retardation is governed by the grip of the tyres !!" Right Dave. That's precisely my point. Once you lock up for example all 4 tyres on 2 identical cars with 4 identical control tyres that are bias-balanced and padded identically surely the only difference between the braking systems will be the effort required by the driver to press the pedal (due I guess to initial "bite," piston sizes and the differences in the brake discs themselves.) i.e. pedal feel. Even a standard modern 7 can lock all 4 wheels with ease so the Alcons and AP 4-pots have no problems whatsoever. So surely the Alcons should have the edge over the AP's - less unsprung weight for directional changes, lighter etc. etc. I'm only interested because I'm tossing up which system to go for. Have you asked the factory Dave? Is it a manufacturing or design fault I wonder? [i doubt it very much...] Andy Link to comment Share on other sites More sharing options...
paul jacobs Posted February 23, 2001 Share Posted February 23, 2001 I've got the older grey APs' with vented rotors and not had the vibration problem, but I have had overheating and a soft pedal with little bite. They will lock eventually, but certainly don't inspire confidence, and will fade when hot too - very unsatisfactory. I'm currently putting on even bigger rotors, up to 285mm fronts, with standard rears, spacing off the calipers and as well as the bigger discs, which I hope will help with the cooling, I'm installing the bigger 13/16" "competition" master cylinder. Anyone done any of the above, or had the soft pedal problem with the standard m/c. It occurred to me that perhaps the factory should specify the bigger m/c as a matter of course if the big brake kit is specified? BTW, the overheating only occurs on the track, and I ought to mention that it is not on a se7en but on a 21, with a 245bhp Vauxhall engine installed, so a restriction in air around the rotors/calipers, but surely no worse than any other full bodied car? Link to comment Share on other sites More sharing options...
StewartG Posted February 23, 2001 Share Posted February 23, 2001 Number six, sounds like you're making a good case for standard brakes as yes they can lock the wheels. The problem is not in the right order. I think better brakes bring not more wheel locking power but the ability to engineer a better balance front to back and therefore more car stopping power. Paul. get yourself a race master cylinder the APs wont feel soft then. Link to comment Share on other sites More sharing options...
elie boone Posted February 23, 2001 Share Posted February 23, 2001 stopping power depends on pad area, feel on the piston size of the calliper and cooling can be made better by extra grooves in the disc (up to 40)but for a Caterham 21 it would be wise to have some cooling tubes on the caliper. Red Dot makes solid disc's with grooves i think i payed 100 £ for a pair with 6 grooves. Link to comment Share on other sites More sharing options...
Number Six Posted February 23, 2001 Share Posted February 23, 2001 There is also the problem of brake fade, not such a problem on sprints and hillclimbs, certainly is for track use, hence the need to uprate above standard. Andy Link to comment Share on other sites More sharing options...
captain chaos Posted February 23, 2001 Share Posted February 23, 2001 I've got the older grey AP's with a Std M/Cyl and I too feel it is too soft without any initial bite. I've been thinking about upgrading the M/C...any ideas on how much, is there a choice of models (which bore size?) There's a chance I might be able to buy direct from AP. Link to comment Share on other sites More sharing options...
Number Six Posted February 23, 2001 Share Posted February 23, 2001 CC I might be wrong but I think it's 138 squid... Andy Link to comment Share on other sites More sharing options...
captain chaos Posted February 24, 2001 Share Posted February 24, 2001 I take it the thing will be relatively easy to fit. How different is the installation in terms of brake pipe location? Link to comment Share on other sites More sharing options...
StewartG Posted February 24, 2001 Share Posted February 24, 2001 There's no difference in terms of brake pipe location but I had to shorten the threaded plunger, the bit that the pedal pushes in, in order to stop it fouling the pedal. It seems a bummer to have to hacksaw the end off something you've just paid nigh on 150 nicker for. The real tedious bit is bleeding the brakes. I suggest you plug the pipes with something like matchsticks to stop all the fluid leaking all over everything whilst you actually do the change-over. Once everything is reconnected fill the new m/cylinder with fluid and gently pump the pedal with the resevoir lid off until no more bubbles come out. This will take ages but unless you get all the air out of the m/cylinder you can't hope to get the fluid pumped through to the calipers. Once there's definately no air in the m/cylinder bleed the brakes in the normal way. Link to comment Share on other sites More sharing options...
paul jacobs Posted February 24, 2001 Share Posted February 24, 2001 I finally worked out that I needed the bigger M/cylinder, shame that the factory didn't recomend it when I ordered the big brake kit when the car was new, they've just made another 160 UKP out of me, or is this what they call "business"? I only got it this week, so haven't had a chance to fit it yet, it looks as if all the pipes are the same, my problem is that I really need a remote resevoir, because on the 21 the unit is fitted in front of the bulkhead and points forewardm and ends up under the throbble botties, which means it fouls the no. 4 air filter/trumpet, and is difficult to fill, though thankfully that isn't often. Graham Ford advised me that twin m/c and balance bar layout wasn't as good as the pukka factory part, so I've taken his advise. Great to have friends isn't it? P.S. The matchstick trick sounds like a great idea. Link to comment Share on other sites More sharing options...
Number Six Posted February 24, 2001 Share Posted February 24, 2001 Caterham are the dog's bollox but they @@@k up all the time. It's a real shame and they could easily, easily, get their act together. Basic business sense. Don't hire anyone who is a no-nothing. Andy Link to comment Share on other sites More sharing options...
elie boone Posted February 25, 2001 Share Posted February 25, 2001 To bleed the brakes easely take an old reservoir cap, drill a hole in it the size of the air gun u use to clean out parts,then put the gun in the hole of the old cover NOT MORE THAN 800gr PRESSURE !!! With this system it only takes about 5 min. to bleed the brakes. Link to comment Share on other sites More sharing options...
EFA Posted February 25, 2001 Share Posted February 25, 2001 I'm not going to admit to this, but you can fit the pads with the BACK to the disc in the AP setup!! I heard of "someone"who drove 300 miles without realising the problem! This gives strange steering effects under braking as you can imagine, not that I know of course..... Arnie Webb The Fat Bloke blush.gif in a Slow Old Vauxhall wink.gif Link to comment Share on other sites More sharing options...
mark.hall Posted February 25, 2001 Share Posted February 25, 2001 OH..........MY............GODteeth.gifbiggrin.gif Link to comment Share on other sites More sharing options...
elie boone Posted February 26, 2001 Share Posted February 26, 2001 Fast Arnie,It is indeed possible yo fit the pads with the back on the disc side,but it is not very effective. blush.gif Link to comment Share on other sites More sharing options...
captain chaos Posted February 28, 2001 Share Posted February 28, 2001 I shall place a message in the wanted section, but can anyone recommend a possible source for a second hand uprated M/Cyl? Link to comment Share on other sites More sharing options...
Gary Furst Posted February 28, 2001 Share Posted February 28, 2001 I have used the old AP Racing calipers for about 4 years now and only experienced a small amount of brake fade whilst racing with the original pads suggested by Caterham. After a couple or races I changed to Carbon Metallic pads and have never suffered from brake fade again. I have the standard (original fit) capacity master cylinder. The only problem that I have suffered with the original grade of Carbon Metallic pads was that they were very hard on the discs and caused them to crack-up. I should point out that I compete in endurance races (100 Miles) so the discs and pads have a really hard time, so 3years of my use equates to a lot of short race or normal track/road time. I can't remember of hand what grade of pads I am using at the moment, but if anyone wants to know I'll check. Link to comment Share on other sites More sharing options...
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