Rear disk brakes 30% efficiency? Please Help

1. AntscVTR Infrequent Poster Joined: Aug 2012 Lancs Posts: 187 99 VTS

   #1 28th February 2013, 16:45

   Hi guys I took the motor in for an MOT yesterday and it failed on the rear brakes.. They are only at 30% efficiency and I am looking for suggestions on what it could be? I have changed the rear pads and disks since the MOT with no joys (handbrake is spot on, 5 clicks to the top and holds the cars weight on 2 ticks)
   
   The car prior to the MOT had been standing for around 2 weeks with little movement whilst I serviced it and did everything i thought it would need for its MOT, The service made the car perform better than I had ever experienced.. I had bit of a shaky experience with the back end when testing it, at first I thought it was the extra power gained making it feel like a new car lol but from what I can find on here it could be the Brake Bias Valve seized from little movement.. I have doused that in WD40 and there is 10mm play in the bolt (which I believe is required) the valve opens and closes now with little effort and the changes to my rear brakes wasn't fantastic.. I could turn the rear wheel with my left hand fairly easily before I WD40'd the Bias Valve now they seem to have increased to me having to use my right arm with some force but still only one handed.. From what i can guess it maybe up to 40% now? Still think it will fail its MOT and the guy wont let me go back for free again after the next visit (been twice now hehe)
   
   Any help would be great
2. MuZiZZle Saxperience Post Whore Joined: Jul 2011 Newcastle upon Tyne Posts: 7779 Phase 2 VTS , E61 M5

   #2 28th February 2013, 16:47

   I'd expect 30% to be high for a saxo, I'm sure mine do nothing!
3. AntscVTR Infrequent Poster Joined: Aug 2012 Lancs Posts: 187 99 VTS

   #3 28th February 2013, 16:53

   Quote:

   Originally Posted by MuZiZZle I'd expect 30% to be high for a saxo, I'm sure mine do nothing!

   Thanks for the speedy reply Muz, I am not sure if it is the different size's 'n' thickness of the front and rear disks that create the balance of 80/20 (front/rear) brake force. The tester was sure it had to be above 50% for the rear.. Im stumped!
4. Gandi699 Saxperience Post Whore Joined: Apr 2011 Posts: 9100 Amazon green VTR 16v, Inferno RS clio 182

   #4 28th February 2013, 16:55

   change your bias valve to be honest. I "unseized" my old one yet it still caused lock up issues at the rear, the spring was a bit shagged.
   Now a new one is fitted (with new brake lines as chances are the old ones are unlikely to come out in my experience) it stops just fine with no locking up at the rear upon harsh braking.
   
   Also you really dont want a 50% bias to the rear, thats stupidly high
5. Bedford126 Saxperience Post Whore Joined: Jul 2010 Morley, Leeds Posts: 8469 Civic ep3 type r powered by TDI NORTH

   #5 28th February 2013, 19:47

   Quote:

   Originally Posted by AntscVTR The tester was sure it had to be above 50% for the rear.. Im stumped!

   I would take my car elsewhere to be tested if I was you.
6. AntscVTR Infrequent Poster Joined: Aug 2012 Lancs Posts: 187 99 VTS

   #6 1st March 2013, 14:01

   Admin please delete thread as the info is wrong
7. blackie_2k5 Saxperience Hardcore! Joined: Oct 2008 Birtley Posts: 22253 VTR Turbo, 106 xsi track slag, Transit recovery, B

   #7 1st March 2013, 20:55

   Saxo rear brakes are known for being shit
   
   Usually the cables or bias valve