FAO Lee and JP's mate - Braking issues

  1. Saxperience Post Whore Joined: Mar 2007 Reading Posts: 8980 French tin can
    #1
    Chaps,

    I've been thinking about what Kam brought to my attention about excessive stiffness of the rear dampers resulting in the car becoming skittish. I've got a feeling this problem I've got may have started around the time I changed the stiffness of my dampers.

    I'm using some rather cheap Koni sports dampers, and they only have 3 damper settings. I changed from them from the softest to the stiffest in an effort to stop the rear becoming so floppy.

    Now, the worst part of the braking problem I'm experiencing, is when you brak hard from high speed. As you know, the weight will shift to the front during braking, and more so with harder braking... The rear damper stiffness does make a difference to how much weigh shifts forward, so I'm thinking of a few scenarions:

    1) The dampers are so stiff, causing a lack of weigh shift under heavy braking.

    2) The rear right damper may be stiffer than the rear left, causing weight to shift more towards the left under heavy braking, in affect, causing the car to pull to the left.

    This ties in with the increased tyre wear I noticed on the front left as well, as this could very well mean that more braking is happening on the left...

    Lee, JP, have your cars had the stock suspension changed by any chance?
  2. Super Moderator Joined: Feb 2004 Tonbridge United Kingdom (England) Posts: 38236 Vtr, 172, throttle bodied track slut
    #2
    overdamping the rear would cause it to become skittish.
  3. Saxperience Forum Bum Joined: Dec 2006 Buckinghamshire Posts: 2700 under age
    #3
    well it is a simple job to do as you said yourself, wont take you long to adjust them try it when it next becomes dry
  4. Saxperience Post Whore Joined: Feb 2006 northumberland Posts: 7693 pulsar gtir, mk4 astra sxi
    #4
    the koni's dont go hard enough to over damp it too much imo, your thinking up problems that arent there i reckon. i had mine on hardest setting front and back and liked them like that.
  5. Saxperience Forum Bum Joined: Dec 2006 Buckinghamshire Posts: 2700 under age
    #5
    i think toad is becoming stuck for ideas tbh the left hand pull under breaking is really dngerouse
  6. Saxperience Post Whore Joined: Jul 2007 Nuneaton Posts: 6476 RB RS 200
    #6
    Quote:
    Originally Posted by Toad View Post
    Chaps,

    I've been thinking about what Kam brought to my attention about excessive stiffness of the rear dampers resulting in the car becoming skittish. I've got a feeling this problem I've got may have started around the time I changed the stiffness of my dampers.

    I'm using some rather cheap Koni sports dampers, and they only have 3 damper settings. I changed from them from the softest to the stiffest in an effort to stop the rear becoming so floppy.

    Now, the worst part of the braking problem I'm experiencing, is when you brak hard from high speed. As you know, the weight will shift to the front during braking, and more so with harder braking... The rear damper stiffness does make a difference to how much weigh shifts forward, so I'm thinking of a few scenarions:

    1) The dampers are so stiff, causing a lack of weigh shift under heavy braking.

    2) The rear right damper may be stiffer than the rear left, causing weight to shift more towards the left under heavy braking, in affect, causing the car to pull to the left.

    This ties in with the increased tyre wear I noticed on the front left as well, as this could very well mean that more braking is happening on the left...

    Lee, JP, have your cars had the stock suspension changed by any chance?

    well it did it before i changed from the old shocks that were fitted to the car before i brought it and now im using spax psx shocks with 28 stage adjustment and it doesnt make an ounce of difference between really soft and rock hard it still pulls to the left im stuck for ideas on this tbh.
  7. West Midlands Joined: Dec 2007 West mids Posts: 23149 Supra,civic GL
    #7
    ive seen this in the flesh on lees car its pretts scary thb
    id jus picked my car up n he came past then braked hard for an island i think (dosent really matter)
    i thought he was gunna at least end up sideways
    proper scary
  8. Saxperience Post Whore Joined: Feb 2006 northumberland Posts: 7693 pulsar gtir, mk4 astra sxi
    #8
    why not check your brakes prperly? all calipers move freely, drain, refill and bleed fluid, all discs and pads are in good condition?
    instead of trying to think of a more complicated answer.
  9. Saxperience Post Whore Joined: Oct 2005 Sydney Posts: 8525 Mango Westcoast
    #9
    No problems on mine,

    thats with the billie group n's
  10. Saxperience Post Whore Joined: Mar 2007 Reading Posts: 8980 French tin can
    #10
    I know, I'm grasping at straws.

    Williams, I've done all that mate. New pads all round, discs are fairly new anyway, the system has been flushed a couple of times. The calipers slide back and forth nice and freely... What else can I do? A guy I know at work who's a racer, is convinced it's brake balance, and the rears are driving the front under heavy braking, as the calipers are much more powerful at the front. I really don't know what else I can do. What a BITCH of a problem.
  11. Super Moderator Joined: Feb 2004 Tonbridge United Kingdom (England) Posts: 38236 Vtr, 172, throttle bodied track slut
    #11
    Quote:
    Originally Posted by jpsaxo View Post
    No problems on mine,

    thats with the billie group n's
    yours are gmc ones though are they not josh? so not using groupN rear dampers.
  12. Saxperience Forum Bum Joined: Dec 2006 Buckinghamshire Posts: 2700 under age
    #12
    Quote:
    Originally Posted by Toad View Post
    I know, I'm grasping at straws.

    Williams, I've done all that mate. New pads all round, discs are fairly new anyway, the system has been flushed a couple of times. The calipers slide back and forth nice and freely... What else can I do? A guy I know at work who's a racer, is convinced it's brake balance, and the rears are driving the front under heavy braking, as the calipers are much more powerful at the front. I really don't know what else I can do. What a BITCH of a problem.
    if thats the case then you need to shut off the rear breaks some how, have you still got your original break hoses, could you swap them back over then clamp the rear break lines
  13. Saxperience Post Whore Joined: Mar 2007 Reading Posts: 8980 French tin can
    #13
    No, they went in the bin!
  14. Saxperience Addict Joined: Nov 2006 A farm shed in Aylesbury Posts: 14916 Corolla AE86 Peugeot 205 B18C (in bits)
    #14
    are you getting the same clamping pressure left to right? MOT stations check this?

    If you are then I doubt its a brake issue but its either something is bent or a bush is worn..

    Toad I'm lost on whats been checked / replace / altered. Perhaps you could do a summary and I'll think some more.
  15. South Wales Joined: Jan 2005 The Valley's init Posts: 3601 vtr mk2
    #15
    could it be the brake bias valve that is on the back axel? as i know mine was making the back brakes lock before the front and it would make the back kick out, what about a faulty master cylinder?
  16. Saxperience Forum Bum Joined: Dec 2006 Buckinghamshire Posts: 2700 under age
    #16
    yeah thats what i said sim69er but i am not totally sure wether it is possible to swap the 2 brake lines over to check this, otherwise it would mean buying a new one which could be expensive especially if it dosnt fix it
  17. Saxperience Post Whore Joined: Mar 2007 Reading Posts: 8980 French tin can
    #17
    Quote:
    Originally Posted by sim69er View Post
    could it be the brake bias valve that is on the back axel? as i know mine was making the back brakes lock before the front and it would make the back kick out, what about a faulty master cylinder?
    There is no bias valve like with the mk1 106s / Saxo's. All done electronically... Bugger that!
  18. Saxperience Post Whore Joined: Mar 2007 Reading Posts: 8980 French tin can
    #18
    Quote:
    Originally Posted by KamRacing View Post
    are you getting the same clamping pressure left to right? MOT stations check this?

    If you are then I doubt its a brake issue but its either something is bent or a bush is worn..

    Toad I'm lost on whats been checked / replace / altered. Perhaps you could do a summary and I'll think some more.
    Cheers Kam, I'd appreciate the advice. I'm really lost on this one.

    Right, there's 2 different symptoms:

    1) Braking hard from low to medium speed - The car pulls side to side. Often left, and then right. It feels skittish, like the rear is stepping out.

    2) Braking hard from high speed - The car pulls to the left, HARD! You have to let off the brakes and steer to the right to correct things. Very scary. This seems to happen anywhere above 75, 80mph.

    I've taken the car to an MOT testing station, and it checked out just fine. I can only think that when on the rollers, they cannot test the brakes to their full potential, as they probably just lock the rollers... Anyway, if I don't brake too hard, I can still get the car to pull up fairly quick, but it's when you start to really get them biting that all hell breaks loose.

    I've had the suspension checked out a few times, there's no play anywhere, it all seems to be tip top. The bushes are fairly new, they are poly ones from Powerflew.

    The thing is, when the car pulls to the left when braking from high speed, it's so dramatic, I can't see how a slightly worn suspension item would be accountable.
  19. Saxperience Post Whore Joined: Oct 2005 Sydney Posts: 8525 Mango Westcoast
    #19
    Quote:
    Originally Posted by Ryan View Post
    yours are gmc ones though are they not josh? so not using groupN rear dampers.
    aye, whatever comes in there "group n kit"

    Once we've checked my mates over i'll post up if we find anything
  20. Saxperience Post Whore Joined: Mar 2007 Reading Posts: 8980 French tin can
    #20
    OK mate, fingers crossed. Do the symptoms I have explained above seem similar? I did a little more testing yesterday, braking from lower speeds, and this side to side pulling is definately NOT suspension related. I can feel one side brake harder than the other and then vice versa, as the car pulls left and then to the right. It's as if the ABS system is on the piss as it appears to reduce the braking power to the front wheels, but not to both sides evenly if that makes any sense? I did disconnect my ABS system a while back and tried braking from high speed, and it didn't make any difference. I'll disconnect the ABS again, and play about at braking from low speeds, as it does seem ABS related.
  21. Saxperience Hardcore! Joined: Oct 2005 Aycliffe Posts: 32205 Saxo VTS
    #21
    if there is any major discrepancies in the damping of the rears you'll know about during dramatic changes of direction...


    take it for a few spins on the country roads and see if you can feel any difference. ultimately you'll have to get them tested to confirm their damping rates are equal.

    secondly... did you ever sort out the camber issues??? if not then why not? as thats the problem.
  22. Saxperience Post Whore Joined: Mar 2007 Reading Posts: 8980 French tin can
    #22
    Explain to me how to sort out the camber issues and I will. So far, nobody has been able to help with either problem.
  23. Saxperience Addict Joined: Jul 2005 Solihull / Bournemouth Posts: 14233 2015 Lapiz Blue Golf R
    #23
    Just a thought, but if any of the brake lines had taken a knock, like a dent or something, but not leaking, would thaty cause perhaps a reduction in braking from one caliper, causing it? Just a thought as I rear this.
  24. Saxperience Post Whore Joined: Mar 2007 Reading Posts: 8980 French tin can
    #24
    I certainly haven't noticed anything untoward mate. The hoses seem fine too.
  25. Saxperience Post Whore Joined: Oct 2005 Sydney Posts: 8525 Mango Westcoast
    #25
    The only other thing i can think of is you, or the previous owner have hit a kurb and bent the beam - we have come across this when refurbing them - it only needs to be slight but its enough!

    I'll find out when my mate brings his beam down to us hopefully.
  26. Saxperience Forum Bum Joined: Dec 2006 Buckinghamshire Posts: 2700 under age
    #26
    you say it may be to do with your abs but we turned it off by removing to fuses and it was fine
  27. Frequent Poster Joined: Oct 2007 Newcastle Posts: 825 306 GTI-6
    #27
    lets gets back to basics. Brakes arent that complicated really. It starts by pushing your pedal which in turn pushes a rod with seals on it (the master cylinder). This in turn pushes fluid down the pipes to some sealed pistons, which in turn push against a brake pad that squeezes against a brake discs and then you stop. Simple. Forget ABS etc for now. For a car to weave or pull under braking is either down to a) faulty suspension (ie not holding the car true under braking force when the weight is shifted) or B) one of the 4 brake lines not doing its job and creating uneven braking.

    Lets rule out a) as youve obviously got some decent and recent suspension there. Dont clutch at straws with things like dampers too hard to stop the laws of physics etc etc. Im sure everything is fine on that front.

    Im pretty sure your problem is with your brakes. First port of call would be checking the bias valve. You dont have one so it cant be that lol. However, you will have something that distrubes braking force as the issue is still there whether its mechanical or electrical. Have you looked fully into this? How is braking force controlled if you have a loaded up car?

    Next check the calipers slid ok, the pistons are free, etc which you have said you have done.

    Im suprised a braking rolle test didnt show up any uneven braking especially when your symptoms sound so strong.

    Next thing i would try is a new master clyinder as if one of the seals has gone, the braking wont be even. You can even buy kits to replace the seals but try one from a breakers first. (you'll need to bleed all the brakes obviously).

    Then if all that is working i'd maybe start looking back at the suspension. have you checked the anti roll bar bushes etc?

    Mine has very strong rear brakes, which i think are actually binding slightly. I had great fun finding out i could lock the rears before the fronts over the last few days. I felt like a pukka rally driver but i'll kill myself on sprint if i dont sort it. Im pretty sure mine will be simple with a sticky bias valve (it did it when standard height too).
  28. Saxperience Forum Bum Joined: Dec 2006 Buckinghamshire Posts: 2700 under age
    #28
    wow thats good help
  29. Saxperience Post Whore Joined: Mar 2007 Reading Posts: 8980 French tin can
    #29
    Blimey Andy, thanks for the big post.

    All I know about the braking bias, is that it's electronically controlled, unlike the previous model 106 / saxo, which used a physical object to measure the rear ride height. So if anyone knows anything about how the bias works on the phase 2 106s / Saxo's, PLEASE shed some light!

    I was thinking of changing the MC as I'm considering getting a 306 GTI one to help with the travel in the brake pedal. Quick question, does anyone know if 4 pot set ups give the same pedal travel as when fitting 306 GTI calipers? If so, I'm definately going to change the MC as my future plans are to get rid of the HEAVY 306 GTI calipers for some lightweight 4 pots...

    The bushes are all pretty much new, as they are poly ones by Powerflex, and have been in for about 6 months now.