JAG IRS brake shudder

[ollykiwi3]

Tom- thanks for your thoughts.in regard to rear brake bias and lock up,I only did that briefly for isolating the issue.brakes are back to where they should be,front locks first.

As for the handbrake test,I'm pretty sure I did that a long time ago. I don't really see the relevance as the two are independent and it only does it with foot pedal pressure.its also intermittent.very hard to repeat consistently. But the handbrake pads do keep wearing? I have return springs on the arms now,but maybe not enough.i keep having to adjust them?


Rotors are centred.
I'm going to bleed them again this weekend and see if that helps.i will be looking into the ebc Reds soon.

Cobra3170- interesting,that's kindof what the brake guy was saying.im not sure if the sensation you had was pulsating due to material build up or more like mine and being a high pitch chatter.i don't get any pedal feedback.
But another thing to look into all the same.

I did record it yesterday but too much background noise was picked up.will try again today.

Ok.thanks guys.

[Tom Wells]

Olly,

But the handbrake pads do keep wearing?

i keep having to adjust them?

This may be a clue...

Mine haven't worn in 32K miles.

Tom

[ollykiwi3]

Tom-do you have any idea how much tension you have on your return springs or a measurement from the arm to the chassis securing point for the springs?
Or the length of the spring in its relaxed posi.

I only just put mine on and had to guess at the tension.maybe not enough and the pads keep contacting due to centrifugal forces during cornering?

Agreed,it needs to be looked at but still don't see how it can affect the main brakes,unless the handbrake pads are transferring material which is screwing with the coefficient?

Will keep trying

Thanks

[Cobra #3170]

Originally Posted by ollykiwi3

Tom- thanks for your thoughts.in regard to rear brake bias and lock up,I only did that briefly for isolating the issue.brakes are back to where they should be,front locks first.

As for the handbrake test,I'm pretty sure I did that a long time ago. I don't really see the relevance as the two are independent and it only does it with foot pedal pressure.its also intermittent.very hard to repeat consistently. But the handbrake pads do keep wearing? I have return springs on the arms now,but maybe not enough.i keep having to adjust them?


Rotors are centred.
I'm going to bleed them again this weekend and see if that helps.i will be looking into the ebc Reds soon.

Cobra3170- interesting,that's kindof what the brake guy was saying.im not sure if the sensation you had was pulsating due to material build up or more like mine and being a high pitch chatter.i don't get any pedal feedback.
But another thing to look into all the same.

I did record it yesterday but too much background noise was picked up.will try again today.

Ok.thanks guys.

Did not feel it in the pedal just vehicle shudder with the rotor contamination problem. I did change to a different pad material when I switched rotors though, used carbotech pads. The stick slip occurs at a constant pressure so pedal does not pulse. You could actually see where pad material was unevenly deposited on the rotor in my case because there were dark and light spots. You can usually feel thick thin wear in the pedal so you are right that probably isn't it.

[Tom Wells]

Olly,

Can't get my car on the lift for the next couple of days maybe so here's some Googling from Jag-lovers.org:

> I know the parking calipers are tightening and releasing,
> but evidently they are not always releasing fully.

It might not explain ALL of your symptoms, but one common problem
with the handbrakes on these cars is a misadjusted cable. By that I
mean, some nimnul has misadjusted the cable; they don't get
misadjusted on their own. The pads wear, the self-adjusters in the
caliper sieze up, and then when the lever can come all the way up
without engaging the brake, the solution is to readjust the cable.
Then when you FIX the worn pads and the siezed calipers, they still
don't work correctly because they're not being fully released when
the lever is lowered to the floor.

Full release of those handbrake calipers is imperative if you ever
want them to work correctly. The only way I know to be sure is to
get under the car and grab ONE lever and try to move it in the
release direction -- possibly pulling the other lever tighter if the
cable is in place. Each lever should be felt to be against a hard
stop. If it's not, you'll need to adjust the cable looser. The
adjustment is at the lever, where you've gotta fiddle with the
carpeting to get at it.

-- Kirbert

and

Aahhh. I think you've hit upon it. On the car with the dragging parking
brake, I discovered that the "plate" (the U-shaped thing with the points
that go in the holes on the top of the handbrake calipers) actually bends as
the pads wear. Whereas the original condition has the arms farther apart at
the points, the dragging pad side on mine had bent past perpendicular so
that it was parallel to the side that wasn't dragging.

Which came first, the bent arm or the dragging? I'm not sure, but it would
seem that as the pads wear, the arm would have to give. Also, it's made of
rather soft metal, and I could almost straighten it by hand. I used pliers
anyway because looking at the pictures and the ones I've removed, they are
supposed to be pretty much straight down the outside edge of each side.

If you can see what you are doing, align it with the holes in the handbrake
calipers. Then reinstall it and safety wire it. I'd add that if it isn't
wide enough, it will probably act as a spring pulling the pads together a
little, until they wear enough to remove the tension.

The bent arms may have been the cause of your problems all along, so you
might want to see if you can straighten the arms and reinstall the "plate"
before dropping the calipers. I don't know if you'll be able to safety wire
it in that position, but I don't know how necessary that is. Anyone?

To sum this all up, it appears that the "plate" acts like a spring, bending
in as the pads wear, but having just enough give to pull the pads away from
the rotor when the brake handle is released. Ingenious engineering.

Mark

P.S. Just so everyone knows I'm not a complete idiot, in the previous
e-mail, I said to disconnect the brake lines from the rotors. Of course, I
meant calipers. Thanks to everyone for not being cruel and pointing that out
(while laughing uproariously).

-----Original Message-----
From: owner-xj at jag-lovers.org [mailtowner-xj at jag-lovers.org]On Behalf Of Darrin hodges
Sent: Sunday, April 08, 2001 5:05 AM
To: XJ Lovers
Subject: Re: [xj] hand brake

Mark
thanks for that suggestion. my main problem was the brass
hook thingie, the original park brake pads were quite worn, im not
sure if the 'arms' on the brass thingie have been 'pushed' inwards, making
it difficult to get the hooks easily back into the holes in the calipers, so
i think ill give your idea a go and see what happens. after that i was going to
change the trans filter/fluid and reseal the exhaust joints, phew, getting worn out
just thinking about it, hopefully, ill even get to drive her before the holiday
is out!

cheers
darrin

Anyway, if you cruise over there and look, maybe one of those guys can point you in the right direction.

Tom

[ollykiwi3]

"Did not feel it in the pedal just vehicle shudder with the rotor contamination problem. I did change to a different pad material when I switched rotors though, used carbotech pads. The stick slip occurs at a constant pressure so pedal does not pulse. You could actually see where pad material was unevenly deposited on the rotor in my case because there were dark and light spots. You can usually feel thick thin wear in the pedal so you are right that probably isn't it. "

Do you recall what kind of speed it was happening? heavy load, or light braking like mine?
thanks again for your insight. where did you get the carbotech pads? what country are you in. here in NZ we are very limited to choice.

Tom- jag lovers was my next move. I heard it can be a pain to adjust these things, correctly. I have mine set so it takes one click to just get a feel of drag on the calipers. I will have to look at the brass tensioners and see what they look like. I do recall one being a bit bent.i only ever adjust the cable length as the calipers are self adjusting, and it is all working fine.although that's one hell of a complex set up.

does anyone else have a measurement for the return springs? in the relaxed state.
thanks again.

[Cobra #3170]

Originally Posted by ollykiwi3

"Did not feel it in the pedal just vehicle shudder with the rotor contamination problem. I did change to a different pad material when I switched rotors though, used carbotech pads. The stick slip occurs at a constant pressure so pedal does not pulse. You could actually see where pad material was unevenly deposited on the rotor in my case because there were dark and light spots. You can usually feel thick thin wear in the pedal so you are right that probably isn't it. "

Do you recall what kind of speed it was happening? heavy load, or light braking like mine?
thanks again for your insight. where did you get the carbotech pads? what country are you in. here in NZ we are very limited to choice.

Tom- jag lovers was my next move. I heard it can be a pain to adjust these things, correctly. I have mine set so it takes one click to just get a feel of drag on the calipers. I will have to look at the brass tensioners and see what they look like. I do recall one being a bit bent.i only ever adjust the cable length as the calipers are self adjusting, and it is all working fine.although that's one hell of a complex set up.

does anyone else have a measurement for the return springs? in the relaxed state.
thanks again.

I am in the US and Carbotech is a US company I used their AX6 compound. I think any mildly aggressive compound would work and yes it was under light pedal pressure. You could also try sanding the rotors with an orbital sander and 80 grit paper to remove the old pad material and see if that makes a difference.
If it were me, I would sand the rotors as described above and put in new pads (what ever you can get) and then break them in following manufacturers recommendations. Multiple stops from a specified mph in a row then cooling then repeat for several cycles then drive with no brake application to cool to ambient temperature and then what ever else they recommend to complete the break in and get an even level of the new pad material transferred to the sanded rotors. If that doesn't work I have no other idea's

[ollykiwi3]

Thanks for the info.
Am going to a mates place to put car on hoist and run it up so I can see from underneath while running.

I just rebled the brakes and went for a drive.

I tried the handbrake only today and all was Quiet.i checked with main brakes at the same time and it chattered. So definitely not handbrake issue.yes I still need to look at that wear problem separately anyway.

Just another thing to throw in the mix,and it's something I was wondering about.
I found the stub axle splines with some wear and was wondering about spline backlash chatter.
I did find today that while driving steady at 20mph with light brake load on I could get the chatter fairly consistent BUT only going downhill or off load coasting. Not going up hil or while slight acceleration. And that seemed fairly repeatable.
Has anyone experienced spline wear like this creating problems?