Garth Posted July 1, 2010 Share Posted July 1, 2010 My 125 Roadsport failed ☹️ its IVA today because the 'braking force' difference between the rear brakes was in excess of 30% . There was also a difference between the fronts, but this was within acceptable limits! The left hand side was the weaker both back and front. The tester also did an emergency stop and the car was sideways by the time it stopped! 🙅🏻♂️ CC charged to bleed the brakes during the post build check, so I am assuming this is not the problem although the pedal does still feel a little 'spongy'. It does certainly not feel really hard - should it? I will bleed them again! I spent a reasonable amount of time on the 15 mile journey to the test braking quite hard and they did get better, but on the way back I braked much harder stax of times and it still felt very unbalanced! The right rear locked a couple of times! Do not appear to be any obvious leaks? Any advice/help would be much appreciated - difficult to really check the problem is solved before taking it back for a re-test? atlast Link to comment Share on other sites More sharing options...
F355GTS Posted July 1, 2010 Share Posted July 1, 2010 Are the n/s rear pads seated correctly with the small lug on the pads seated in one of the 4 slots in the piston? if not you will only get a small area of pad touching the disc Mark Link to comment Share on other sites More sharing options...
James_Russell Posted July 1, 2010 Share Posted July 1, 2010 did the friction material/discs get contaminated with grease or oil during the build? Q41 ACF Classic Grad #98 Link to comment Share on other sites More sharing options...
Garth Posted July 2, 2010 Author Share Posted July 2, 2010 I will check the alignment of the pads in the calliper again, but I am pretty sure they are sitting correctly and making good contact with the disc. It is possible I might have got some lubricant etc on the pads? So my plan at the moment is to replace the pads and then re-bleed and hope for the best!? Any other ideas? atlast Link to comment Share on other sites More sharing options...
James_Russell Posted July 2, 2010 Share Posted July 2, 2010 I have contaminated pads before and - at your discretion - you might chose to clean them up with aerosol brake/clutch cleaner available from motor factors. Use the same gear and some clean cloth to clean the discs. Obviously if the pads are saturated with brake fluid you might want to replace them! Q41 ACF Classic Grad #98 Link to comment Share on other sites More sharing options...
Garth Posted July 2, 2010 Author Share Posted July 2, 2010 Thanks for the advice, I think I will get new ones to avoid any doubt. I presume I can get them from most car places as they are a ford product? Met someone at the school gate who had a Fiat that had similar rear calipers (which only have one piston) and he said that a common problem was the movable part of the caliper used to stick, so will check to see (somehow!) that this is not snagging? atlast Link to comment Share on other sites More sharing options...
Stuart McGill Posted July 2, 2010 Share Posted July 2, 2010 I have some used Mintex 1144s if your interested in them? Probably still have about 5mm of pad left I reckon. For standard front calipers. Sure they will fit but best to check with someone who knows better than me!!! Link to comment Share on other sites More sharing options...
rswestling Posted July 2, 2010 Share Posted July 2, 2010 During my build I had to wind down one of the rear brake callipers, but not the other one. If they are out of balance than maybe they could be providing different levels of force when braking hard. It's pretty easy to tell if they are wound to the same degree. There should be a small amount of play between the pads and the disk. If the play is asymmetrical between right and left than maybe winding down would help. Good luck with the retesting. -robert Link to comment Share on other sites More sharing options...
Garth Posted July 2, 2010 Author Share Posted July 2, 2010 Robert can you be a bit more specific about what 'winding down' is? Thanks atlast Link to comment Share on other sites More sharing options...
rswestling Posted July 2, 2010 Share Posted July 2, 2010 sure, but this thread might be a good start: Rear callipers On my rear callipers the exterior pad is held in place by a knurled threaded adjustable plate. I was able to turn the plate to provide balanced clearance between the right and left. When I first started to put the rear brakes together, the disk would not even fit between the pads on the right, but was fine on the left. I understand that the brakes self adjust, but, as delivered, I could not even build one of mine. Not sure if this is an issue in your build, just what I learned during mine... Rgds, Robert My build Link to comment Share on other sites More sharing options...
7 wonders of the world Posted July 2, 2010 Share Posted July 2, 2010 So far as I know CC ae still using the stock cast iron Sierra rear calipers which have no manual adjustment, common areas for concern on these which can cause inbalance are: 1-Air stil present in the system, as the nipple is not the highest point it's possible that a small quantity is left captive in the caliper, take the caliper off and hold the piston back with the wind back tool or find something solid and clean to act as a temp disc, tip the caliper to allow the trapped air out and bleed as normal. easier if you've got the fully braided rear hoses and not the rigid versions on the DD tube which are a poor engineering solution. 2-As preveiously said friction material contamination, either fluid from bleeding or copper slip! 3-Piston is wound back and friction locked in the body, check both calipers, wind the pistons fully home and then back out by 1/4 turn, assuming the internal mechinism is working correctly they will then self adjust with footbrake application 20-30 firm footbrake pumps usually does the trick. Too young to be old ! Link to comment Share on other sites More sharing options...
Garth Posted July 2, 2010 Author Share Posted July 2, 2010 Thanks for the advice MR 7 Wonders!! I will give this a go. What I cannot really understand is how air in one of the calipers would only affect that caliper, my limited understanding of hydraulics would suggest that air anywhere in the system would affect both calipers as the drop in pressure would be even throughout the pipe? Can someone confirm this please? I have just dismantled the offending side an it looks as though one face (of the external pad - opposite side to the piston) is worn very slightly unevenly. Perhaps they have simply not bedded in properly? Think I will swap the left and right hand side pads? atlast Edited by - Garth on 2 Jul 2010 22:09:15 Link to comment Share on other sites More sharing options...
mrl98 Posted July 2, 2010 Share Posted July 2, 2010 The advice from my colleague at work was that the brakes won't really be bedded in by the time you go for SVA, so use them lots on the way to the test centre !!!! (mine passed, but got significantly better as they bedded in afterwards) Also, Definitely make sure there is no grease on the disc or pads after build. It is very easy to leave greasy fingermarks almost anywhere. They definitely need removing from the discs and pads!! All the best Martin Link to comment Share on other sites More sharing options...
mrl98 Posted July 2, 2010 Share Posted July 2, 2010 btw. was about 60 miles away, and after 60 mile trip on country lanes for caterham's post build check. Might be worth taking the scenic route to the test centre. Link to comment Share on other sites More sharing options...
Garth Posted July 3, 2010 Author Share Posted July 3, 2010 How did you use the brakes on the way to the centre? atlast Link to comment Share on other sites More sharing options...
Graham Perry Posted July 3, 2010 Share Posted July 3, 2010 The traditional cure for brake pad or shoe contamination for many garages is to remove the pad and heat the friction material gently with a blow torch to burn off the contaminants Link to comment Share on other sites More sharing options...
Garth Posted July 3, 2010 Author Share Posted July 3, 2010 About to swap the brake pads at rear - at least that will tell me whether or not it is an issue with the pads or the calliper!? atlast Link to comment Share on other sites More sharing options...
fred_gustafsson Posted July 3, 2010 Share Posted July 3, 2010 One one my rear calipers was completely unwound when I got it from CC. I couldn't wind it back myself so I returned it to CC to sort out. Didn't have any problems after that. Link to comment Share on other sites More sharing options...
Garth Posted July 6, 2010 Author Share Posted July 6, 2010 Bought winding in tool and used it. Everything seems to be working fine. Booked in at the local test centre today to check the brakes on their rollers. Let us hope!.... atlast Link to comment Share on other sites More sharing options...
Garth Posted July 13, 2010 Author Share Posted July 13, 2010 Thanks for all your help chaps - after stripping, swapping pads, re-bleeding, time on some MOT rollers and plenty worring I could find nothing wrong, so can only assume that they were not bedded in well! Took for re-test today and tried as best as conditions would allow to follow 'Sigmamarks' advice! The brakes were alot better and went straight through! Now for the DVLA bit! Garth atlast Link to comment Share on other sites More sharing options...
spiderlane Posted July 13, 2010 Share Posted July 13, 2010 Brilliant news Garth :) - let us know how you get on at DVLA. Link to comment Share on other sites More sharing options...
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