Changing rear brake discs

[briggy 0]

I've just had my car serviced and they tell me that the rear discs need replaced. I'm happy with that as they're a bit rusty and also bind when the car stands for a couple of days.

 

I thought "right, time to get my hands dirty". I've bought the discs from GFS. I've read a few threads on what's involved but would appreciate answers to a few specific questions :

 

1. Do I need any special tools?

2. Do I need to replace any nuts, bolts etc. If I do - where do I get them from & are they expensive?

3. Should I do the wheel bearings at the same time. If so, the same questions as above.

 

Cheers,

Bryan

[dinkus 10]

I don't think you need any special tools as such, but some WD40 and/or PlusGas and a big breaker bar are recommended. Douse the bolts in that and leave them while you have a cup of tea before you try getting them off. Some copper slip is highly recommended as well - put some on the back face of the wheel and wheel nuts before you put them back in.

 

You'll almost certainly have to drill out one of the retaining screws. You don't need to replace them but it'll make your life easier if you do.

 

Yup, definitely do the wheel bearings at the same time. They're pressed into the disks and can be a pig to get out and you're likely to damage them in the process. If the disks are so old that they need replacing then the bearings will be of similar vintage and need doing as well. It's a lot easier to do it at the same time as the disks.

[Roger Blassberg 0]

1. Yes, you need a piston winding clamp to get the pistons back into the caliper. About £20 from Halfords. You will also need a sturdy 8mm hexagon wrench (Allen key or, better, an 8mm fitment to your socket set) to undo the caliper carrier bolts which are done up very tight. The top ones are quite inaccessible too - make sure you give them a soaking with WD40 several days before you do the job. This is that part of the job which will give you the most difficulty.

2.Replace the bolts which hold the calipers to the carriers; they are treated with a locking compound and are one-use only. 4 needed, about £1 each. Also, have 4 hex socket-headed bolts for the caliper carriers to hand (see above) because there is a good chance that you will damage them when taking them out. Again, about £1 each. All from VAG.

3. It's so much easier to change the bearings than to attempt to extract them from the old discs. They come as a kit complete with grease seal, split pin and grease cap (which will prove to be just too big and which you will throw away after 10 minutes trying to hammer it in. before reverting to the old one....) About £10 a side. The inner tracks need to be pressed or carefully drifted into the hub/disc.

 

You might also need new ABS cages (about £10 each from VAG); they can be salvaged from the old discs if you are careful, but any distortion raises the possibility of an ABS fault signal. Make sure you clean any dirt off the ABS sensors for the same reason.

 

The stub-axle nut is not to be done up tightly, otherwise the taper roller bearing will last about 5 minutes. OK do it up tight to settle the bearing fully into the hub, but then undo it again, then nip it up just enough to trap the thrust washer against the outer bearing; so long as the hub doesn't rock on the stub axle, that's tight enough. Put on the locking cap and insert the new split pin.

 

Give the guiding surfaces of the carriers a good wire brushing to ensure that the pads move freely.

 

Check that the guide pins in the carriers move freely in and out; pull them out and grease them, then replace carefully and relocate the rubber seal bellows.

 

Get some copper grease for the metal surfaces of the pad back-plates and the guiding surfaces of the carriers.

 

Do not overtighten the bolts ito the guide pins; hold the 15mm hex on the pin with an open-ended spanner, and do up the bolt with a 13mm socket. It has been known for the bolt head to be sheared off by heavy handedness, and then you need a new carrier because the guide pins are not available separately. That's a £40 mistake to avoid.

 

Good luck. It's a satisfying job, especially if it improves your handbrake action.

 

Best wishes

 

RB

[dinkus 10]

*cough* err yeah and what Roger said :oops:

[Roger Blassberg 0]

Well, having a quiet afternoon, as you can probably tell...

 

Best wishes

 

RB

[fla 9]

Just a general comment, when you spin the back wheels (off the ground of course) should the pads rub the disk slightly and hinder rotation or should they be totally free? And fronts, because of the diff, these will be hard to move even when in neutral?

[stevemac 0]

Be very careful when tightening the rear wheel bearings - usually the correct tightness is learned with experience. Once rebuilt, the rear wheels should spin without resistance & without any "play" in the bearings.

 

Rear caliper carrier allen bolts can be a bar steward to remove - had to grind the heads off 2 of mine at the weekend !!

[briggy 0]

Thanks for all the advice. I'm glad I asked BEFORE I started.

 

Cheers,

Bryan

[Gaz154 0]

yea dude new allen bolts a must i snapped two 8mm allen keys trying

to get them out was not fun

[Supercharged 2]

Yep new bolts is a good idea for any 10 year old car...

 

As for getting the old ones out -

 

Soak overnight with Plusgas

Hammer the allen socket all the way in

One short-sharp belt to release.