|
|
Post by stantondavies on Jul 19, 2009 15:46:34 GMT
The car has always had a tendency to lock the near side front wheel under heavy braking.
I have fitted new callipers, pads, discs, flexible pipes front and back, and rear wheel cylinders which float correctly. All fixed pipes renewed and a new servo fitted.
On Friday whilst the car was being MOT'd I noticed that the figures on the brake testing display were around 420 NSF and 290 OSF. I wasn't paying as much attention as I should have and the figures kept flickering between different values, but it suggests significant uneven braking between the two front wheels.
The car pulls up straight, but yesterday the NSFW locked up in the wet.
I am surprised that there is apparently so much difference in performance
between recently renewed units and, coupled with the fact that the car did this previously, are there other factors at work which would produce the same problem eg steering geometry? Rear brakes seem fine.
|
|
|
|
Post by johnwp5bcoupe on Jul 19, 2009 17:46:51 GMT
Difficult one but if it were me I would change the OS one  just because they are replacements may not mean they are 100% you seem to have covered all other possible causes  then have a word with your friendly garage and ask them to check them on the rollers  |
|
|
|
Post by Phil Nottingham on Jul 19, 2009 18:33:40 GMT
I agree - those brake rooler testing particularly the modern computer4sied ones are very god and should not be ignored - something is wrong. Front brakes should not be unblanced by more than 255 tp pass the MOT and even 10% is much to be safe
If disks/pads are new swap pads over.
Did yoy clean off the coating from the new disks
|
|
|
|
Post by stantondavies on Jul 19, 2009 22:58:51 GMT
Thanks gentlemen. New discs were cleaned off with scraper and thinners. Will consult with the MOT centre to check the exact figures and their opinion - the car did pass. The car pulls up fine in normal conditions, no pulling to the side. What niggles me is that the car did this BEFORE I renewed everything. It's got me foxed.
Surely the tyres can't be implicated in view of the roller test figures? They are a matched pair of Michelins on the front.
Would air in the system give similar problems? I can't say that the brake pedal feels soft.
Will swap pads over to see what happens.
(off to Scotland for eight days first thing Monday, so cannot acknowledge any responses till I get back.)
|
|
|
|
Post by Phil Nottingham on Jul 20, 2009 8:16:30 GMT
Air in system should not affect blanace - weak shockabsorbers fromnt or rear and or springs can cause wheel locking on one side. This may not show up on the brake tester.
Tyres unlikley if a matched pair but just swap from side to side will prove that
|
|
|
|
Post by enigmas on Jul 20, 2009 12:50:44 GMT
Is one of the front brake hoses ballooning more than the other. This would reduce pressure to one side.
|
|
|
|
Post by stantondavies on Jul 30, 2009 9:07:55 GMT
Thank you Gentlemen, I appreciate your input. The brake hoses are new last July but will check for ballooning.
What puzzles me is that this locking up was happening BEFORE the renovation last July when different refurbished calipers were fitted. The pads are new as are the brake hoses. All shock absorbers have been replaced within the last 30,000 miles and a set of JRW heavy duty springs have been fitted about fifteen years ago. I have spare wheels with brand new Hankooks on so can easily try them.
Could the torsion bar be implicated in this intractable problem?
|
|
|
|
Post by Phil Nottingham on Jul 30, 2009 9:19:46 GMT
The torsion bar and suspension could affect braking effort - is car level at front? Torsion bars do not give trouble unless its mountings on subframe has corroded/fractured.
It may be trying to test for movement on each of the 6 subframe mounts as these can come apart
|
|
|
|
Post by eisdielenbiker on Jul 30, 2009 11:19:05 GMT
Hello Phil,
how would you test the 6 mounts for play ? A car jack wont help I guess...
Mark
|
|
|
|
Post by Phil Nottingham on Jul 30, 2009 14:12:06 GMT
A long lever/screwrdriver inserted twixt subframe and body near each mount
|
|
|
|
Post by enigmas on Jul 31, 2009 1:53:41 GMT
Phil, what is the tolerance (movement allowable) for a front subframe mount before it requires replacing.
Has anyone ever replaced the rubber mounts with a fabricated soliid mount (for improved handling)?
|
|
|
|
Post by Phil Nottingham on Jul 31, 2009 7:46:03 GMT
Difficult to say more that a couple off mm's would betoo much? If there are signs of the rubber squeezing out then they have gone
|
|
just because they are replacements may not mean they are 100% you seem to have covered all other possible causes 
then have a word with your friendly garage and ask them to check them on the rollers 
