ZX Brake wobble

Stuart McB · Unread post by **Stuart McB** » 03 Oct 2003, 01:23

Sorry for this post guys, but I'm new to the site but have been reading it for a couple of weeks now (problem with me fire wall not allowing to register).Any how I've got an old ZX Td it's done 143k and is still going strong. I've just had it serviced at a Citroen specialist , you know the usual stuff like oil 'n' filter and cam belt.All is ok but on picking up the car the garage explained that I needed new front and rear brakes. I've changed brakes before so again I put on my overalls and changed the front brakes. Fitted new disc & pads and also checked over the caplipers. Now my problem is that when you brake at speed all is ok but if you are on the motor way slow down from 70 to 50 nice & smooth, 50 to 40 ok but from 40 to 30 it vibrates really bad. I took it back to the garage who've looked at the rear end and said every thing was ok the drums were not oval and suspension rubbers were as new. I've also pulled on the hand brake at speed and you can feel the wobble through it so I'm sure it's the rear. Now I know you 've heard this question befor but does any body know what's going on. I never really noticed it befor but I've changed jobs & use the motorway daily in stead of back roads. Car is a 1993 ZX Advanage TD.

AndersDK · Unread post by **AndersDK** » 03 Oct 2003, 03:26

That's not an old ZX Stuart [;)]
What sometimes happens is - that dirt/rust comes between discs/drums and the hub - making the disc/drum wobble a bit. Also if any small fitting bolts used to hold the disc/drum in place are torqued too much - it may happen. These screws are only there to hold the thing in place - untill the wheel comes on and wheelbolts are torqued correctly.
I suggest you dismantle the rear brake in question - and rub clean the mating surfaces of the drum & hub. Then rub down the brake surface lightly & evenly with emery paper - and ensure no greasy fingerprints are left on the surface. Inspect the brakeshoes for any signs of grease on the brake surface. Likewise "cut" the surface using emery paper.
BTW : you're aware that brake discs & drums needs to be cleaned off stain protecting agents before using ?

jeremy · Unread post by **jeremy** » 03 Oct 2003, 12:18

While you've got the rear brakes to bits its worth bevelling the ends of the linings. Its an old trick for smooth braking and prevents the sharp edge of the lining picking up on any rust in the drum and pulling the shoe into contact whith the drum very sharply.
I find an approximate 45 degree bevel to be fine and usually cut it in situ with a craft knife or a carpenters chisel (much easier). In the days before asbestos was considered a problem files were used and a longer bevel produced but I've always found 45 degrees to be fine.
Jeremy

AndyGimpy · Unread post by **AndyGimpy** » 03 Oct 2003, 22:44

Just a very long shot, But I had a similar problem years ago on a Peugeot 205, We put the car on the ramp in the garage and checked all over and found nothing obvious, Then the young trainee mechanic decided to spin the wheel. Ever so slight noise was heard and on a very careful check of the wheel bearing noticed the bearing had very slight play. New bearings and hey presto problem solved.

Stuart McB · Unread post by **Stuart McB** » 04 Oct 2003, 02:01

Cheers guys for the replies. I'm up to speed with brake changing as I've done it quite a few time over the years. Down side is I also had new rear shoes, hand brake cables all the springs and other bits fitted during the service (sorry I didn't mention it befor). The NSR wheel had a new brake cylinder fitted as well so the whole system has been bleed as well. So I know it can't be the the shoes are dirty etc, can they???
I didn't do the rear brakes my self as I havent got a tourque wrench that goes up to the massive 148 lbf ft also had to work that week end.

AndersDK · Unread post by **AndersDK** » 04 Oct 2003, 03:06

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">I'm up to speed with brake changing as I've done it quite a few time over the years.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
Knowledge is power ...
<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">I didn't do the rear brakes my self <hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
... if you know what's going on [;)]

Stuart McB · Unread post by **Stuart McB** » 05 Oct 2003, 00:40

Ah, message received. Will have alook next week end. Quetion as I haven't got a torque wench that goes up that far can I just judge it and tighten it as much as possible? Or do I need to be spot on with the torque setting of 148 lbf ft? [?]

AndersDK · Unread post by **AndersDK** » 05 Oct 2003, 01:17

Ya mean the hub nut torque ?
148 lbf ft is a lot !
On my BX I use a 1m piece of water piping over my socket winder - this seems to give adequate torque - as you can quite accurately feel WHEN the nut won't give anymore - and then you stop.
Done this for y's to both my CX & all my BX'es.
Of course this is not an accurate method - the nut must be torqued to ensure it won't unwind - but no more than the threads can take.
To be sure - you allways have the option of getting the torque checked/set by a garage. But don't be scared if they just try it - w/o using a torque wrench [;)]

Stuart McB · Unread post by **Stuart McB** » 05 Oct 2003, 22:11

Cheers for that. I've got all the tools left over from my days as an engineer working on 20,000 ton hydraulic presses. Haven't used the 1 meter long socket set for years.

Dave Burns · Unread post by **Dave Burns** » 06 Oct 2003, 02:19

You could hang a bag of spuds (56lb) on a 31 1/2 inch long bar, that would give you about 148 lbf ft, or a 37lb weight on a 48 inch bar.
Personaly I just grab the goose neck bar from my socket set and give it some umpty, not had any problems yet.
Dave

wrinklet1 · Unread post by **wrinklet1** » 07 Oct 2003, 02:44

Just a question, when you replaced the brake disc, was the securing screw/bolt that holds the disc in place removed or did you have to drill it off? If you did, did you put the new disc back in the right place? I have had to re do a Citroen Garages work, because they put the new disc on without replacing the securing screw/bolt, and because it was protruding the disc then wobbled causing a bad vibration.
Hope it helps
Paul

Stuart McB · Unread post by **Stuart McB** » 09 Oct 2003, 01:11

When I replaced the disc's I had a right old game. The driver's side was welded on I think. Both fixing studs were in but had to be drilled out and re tapped using a 6mm tap (giong through from 1 to 3) and the passenger's side only had one stud in it but this came out ok. Again both holes were re tapped and new studs fitted. The front is fine, the wobble is deffinatley from the rear. I think I'm on the right track though another web site I use has sugested it could be tyres or possibly a rear bearing. I've now had a right good raz up the M5 and applied the hand brake at 75mph nothing like silk the same at all speeds except 50mph to 38mph. My journey up the M5 lead me the Cit specialist that did all the previous work as it was now up for the cam belt. I have again had them look at the rear brakes & while it was up I had a look my self. All is in order brakes nice & clean etc and the drums arn't oval. As the tyres are looking a little tired (no punn intended) I think it could be tyres first & see how it goes.
Again sorry for the long reply.

BonceChops · Unread post by **BonceChops** » 09 Oct 2003, 01:17

When I have had to drill out the disc retaining bolts in the past, I have never bothered to retap them - just left them out. The wheel nuts/bolts hold the disc in place. The 6mm bolts are only there so the disc does not fall off when you are changing the pads [:D]

Stuart McB · Unread post by **Stuart McB** » 10 Dec 2003, 23:54

Hurray!!! I have finally gotten rid of the wobble on my brakes completley and it only cost £140. Had 4 new tyres put on last week end and the brake wobble I was getting betweeb 50 & 40 mph has now gone. The guy's at Kwik fit said that the tyres were a little bold but nothing to indicate that one or more were out of balance. Only problem now is the steering wheel is slightly off center even though the car goes in a straight line when you take your hands off the wheel. I'll have the Kwick fitt guy's re ajust the traking so the straight a head position on the steering co insides with the wheels on Friday as I have a day off. Christmas doo the night be for. I'll let you know how I get on.