malcolm Posted June 10, 2005 Report Share Posted June 10, 2005 I noticed at the Elvington drag strip day that there's something odd going on with the brakes. Under lighter pedal pressure I can feel the pedal 'undulating' under my foot and some vibration through the steering. I had the wheels off and took a look at them with a mechanic friend yesterday. Plenty of material on the pads, the (vented) discs are barely worn but have some black/grey marking on the surface. My mechanic friend recons these are scorch marks - a sign the brakes have been overheating - and that the discs have warped. This makes sense to me given the symptoms. Question is what can I do to stop it happening next time. These are 4-pot Princess type brakes with vented discs. Would grooved ones help? Drilled?? Malcolm. Quote Link to post Share on other sites
andrewt Posted June 10, 2005 Report Share Posted June 10, 2005 Of course you could not brake so hard or so often That would do it. Does your inner wing have the cut out for air ducts at the bottom front. the new inner wings i fitted had this whilst the early ones i removed did not. You could cut out the shape & duct air from your spoiler over the brakes. Another possibility is to make a duct that bolts to the caliper & forces air over the caliper & brake, kind of like a scoop. Also what wheels do you have on? Is there room for air to pass through the wheel unhindered? Also what pads are you running as some are better at heat absorption than others and finally buy big brand discs only as I have had bad experiences with cheap pattern discs warping. Andy. Quote Link to post Share on other sites
marvmul Posted June 10, 2005 Report Share Posted June 10, 2005 Grooves in the discs are very useful in my own and others' experience. The grooves make the brakes perform better by removing the dust/gas layer of the pads. Better performing = cooler pads and discs. Quote Link to post Share on other sites
Cinnobar Posted June 10, 2005 Report Share Posted June 10, 2005 Malcolm, they could be warped or it could be DTV which is disc thickness variation. This happens if they're not 100% square to the hub, generally because their was muck on the hub where the disc fits over. You'll need a dial guage to check. Yes grooving does help keep the pads clean although drilling can cause cracking. Noise from either can be a bit disconcerting though! Jim Quote Link to post Share on other sites
malcolm Posted June 10, 2005 Author Report Share Posted June 10, 2005 Of course you could not brake so hard or so often That would do it. The combination of powerful 4-pot brakes and the V8 is what makes the car as good as it is on track. I'm interested in the ideas for cooling though. It's a 1976 car so no ventilation from the inner wings, do you think this would help significantly? Malcolm. Quote Link to post Share on other sites
andrewt Posted June 13, 2005 Report Share Posted June 13, 2005 I agree about the grunt and brakes as i run the AP competition set up the works car used, but updated to the latest spec calipers. Even then discs don't last too long. Adding this ventilation and then enhancing it by directing the air thru a duct would definitely help when the car is moving quickly, as it can only help air pass over the wheel. You could also close off the bottom of the f/glass spoiler you run using ally sheet or grp fibreboard secured to the flat edge of the spoiler in the wells below the headlamp assemblies. Then direct the pressurised air from the closed area that creates thru a 3 or 4" hole in the bottom of the front of the inner wing into the wheel well. if you then made an wide ally scoop (a bit like your power bulge) that attaches to the caliper bolts (since the Tr is conveniently front braked) then this air would be directed over the caliper & disc to spill out thru the spoke gaps in your supalites. Actually ducting this is even better except this creates a big problem of accomodating the huge lock the Tr has without rubbing or crushing the ducting. I am seriously considering this and also to enhance the rad cooling by closing off below the rad as well. This will force that air through the rad & oil cooler instead of letting some of it spill below the rad. Andy.. Quote Link to post Share on other sites
malcolm Posted June 13, 2005 Author Report Share Posted June 13, 2005 Thanks Andy. I'll be giving some of this ago and let you know how I get on. Today's problem is that my current 1980s AP brake discs are no longer available so I'll have to replace everything with a modern set-up anyway. No bad thing, except the price of course Malcolm. Quote Link to post Share on other sites
andrewt Posted June 14, 2005 Report Share Posted June 14, 2005 Malcolm What discs are you running? Just about anything is available from competition stuff to road stuff. There are a couple of good places to try. Brakes International are very good for standard stuff. I got the rare & elusive early Rover SD1 master cylinder from them. If you describe your problem they are very willing to help. Brakes International For AP stuff and Mintex competition stuff especially, try Questmead. Alan Brown is the boss so tell him Andy from Aberdeen recommended him. They can also get you anything AP that is available. this is where i got my competition AP stuff from. they are also the best people for advice etc. Questmead Good luck Andy Quote Link to post Share on other sites
malcolm Posted June 15, 2005 Author Report Share Posted June 15, 2005 Hi Andy. I think I need to have a chat with you off here. Would be good if you could mail me a contact no and let me know when it would be convenient. SnS tell me I have some AP brake discs that were made in the 80s and are no longer available. To fit these with Capri discs means drilling and welding the calipers to modify them - I really don't like the sound of this. I totally understand that I can buy replacement hi-spec or AP brakes but the prices for these..... I'd also like to discuss springs! Thanks very much for the links. Malcolm. Quote Link to post Share on other sites
malcolm Posted June 24, 2005 Author Report Share Posted June 24, 2005 AP have been very helpful about this and put me onto BG Developments who were responsible for the set-up I have at the moment. Hopefully they will be able to make up some discs to suit. An interesting comment from AP is that if I change from the iron Princess calipers to more modern alloy ones brake travel will increase (iron calipers are very stiff). Not considered that ??? Malcolm. Quote Link to post Share on other sites
Guest Chris Draper Posted June 24, 2005 Report Share Posted June 24, 2005 BG Developments did my AP set up a couple of years ago. Very helpful & professional. Quote Link to post Share on other sites
jonlar Posted June 25, 2005 Report Share Posted June 25, 2005 An interesting comment from AP is that if I change from the iron Princess calipers to more modern alloy ones brake travel will increase (iron calipers are very stiff). Not considered that ??? Hi Malcolm, if I understand that comment correctly do they mean that the calipers will flex and the gap expand, when pressure is applied by pistons squeezing the pads and discs, or the cylinders are a smaller diameter in the alloy ones resulting in more piston movement - if the former, I find that rather hard to believe ? Quote Link to post Share on other sites
malcolm Posted June 25, 2005 Author Report Share Posted June 25, 2005 It was only an email message from AP Jon. I'll quote it extactly, but the inference is that alloy calipers will somehow flex or expand? "If the conversion kit involves an alloy 4-pot then be aware that brake pedal travel will increase. Iron calipers are very stiff!" I'd certainly not considered this but it is straight from the horses mouth.... Malcolm. Quote Link to post Share on other sites
malcolm Posted June 29, 2005 Author Report Share Posted June 29, 2005 An update. Interestingly Jon Wolfe's book also talks about cheaper alloy calipers 'separating' and increasing pedal travel, so I guess that's what AP are referring to. BG can make up bells and discs to suit the original AP Princess caliper set-up and I think that's where I'm going. If anyone else would like some now's probably a good time to say as I expect it would reduce the price. Talking about prices - the new bells/discs and fittings are likely to be under £400 which isn't bad compared with the other options. Expecially as I was happy with the set-up until I broke it Malcolm. Quote Link to post Share on other sites
jonlar Posted July 1, 2005 Report Share Posted July 1, 2005 Thanks for that Malcolm, very interesting information. It all makes sense when temperatures, forces and pressures are taken into account I s'pose. Quote Link to post Share on other sites
Guest Chris Draper Posted July 3, 2005 Report Share Posted July 3, 2005 Just thought I'd note that I don't have excessive pedal travel with the AP calipers. Braking is strong & consistent with good feel - & that's with the standard servo. Some alloy calipers flex more than others - I've heard that Wilwood calipers flex a fair bit for example & it's something to consider when selecting calipers. It is a fact that iron is more rigid than aluminium, but if you consider that AP calipers are used on many of the top marques, I'd doubt that the amount of flex is significant. One of the major advantages of ally calipers is the reduction of unsprung weight - I couldn't believe how light mine were compared to the old 2.8 Capri calipers. I guess what it comes down to is that you'd probably notice a difference, but judging from my set-up it wouldn't cause a problem with braking capacity. Quote Link to post Share on other sites
andrewt Posted July 4, 2005 Report Share Posted July 4, 2005 I would agree about the AP alloy calipers being stiff & light especially compare to Willwoods. My point of reference is AP Racing's Alloy range. In summary, having experience of both over the years, the AP's are worth the price difference over the Willwoods in my opinion. The burst pressure of the Willwoods is reported to be within the normal working capacity of the AP's. I use a standard Tr7 servo with an early SD1 Rover master. This is a straight fit except for a spacer to compensate for a slight difference in length of the pushrod. This gives less travel of the pedal for the same displacement helping to offset the larger caliper & slave cylinder capacities. Also i like a firm brake pedal as all the other controls are also somewhat firm. Andy Quote Link to post Share on other sites
malcolm Posted July 10, 2005 Author Report Share Posted July 10, 2005 This has been a great thread and I've learnt a lot. Will definately be making some additional ventilation along the lines of AndrewT's suggestions. I finally got around to removing the hubs and discs today. The idea being to check/repack or replace the wheel bearings, have a good look at the discs & hubs, and re-fit/tighten everything. The bolts attaching the disc to hub on the driver's side were loose! I've tightened these up and it seems much better so hopefully I've staved off the big spend for a while. It is a good setup, but I'd have to agree that the old iron Princess caliper is really heavy. I'm also now told that parts for the caliper have become so rare/expensive that rebuilding one may not be economical in the future. Ho hum, best start saving up :: Malcolm. Quote Link to post Share on other sites
frankman Posted July 23, 2005 Report Share Posted July 23, 2005 Hello T7-8's What kind of Brake conversion seems to be in a good range of price and effect.. there are some Volvo(240) then MGF (Rover100, Montego) Lotus Elise and AP as well also I have seen some Brembo -Porsche Who has experience of this, what kind ever and do I need to change the Brake Master /Servo Cylinder... thanks I use 16" wheels Just bether brakes - please Thanks for some infos Quote Link to post Share on other sites
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