uneven brake pad wear

[dmccormick]

Treated myself to a Clarke 240v impact driver for £70 and an 8mm 1/2 inch hex bit and it did the trick on the bottom bolt. Unfortunately the top one is no good - I don't know the term for it but its the equivalent of the thread being stripped, the hex hole is rounded and the key just turns inside it without gripping.
Have ordered an Irvin bolt extractor in hope that the 11/16 will grip the Allen bolt head.

 

[Mursal]

Bad luck its not easy to get then shifted, you could try a 3/8 inch imperial Allen head, it will be just slightly bigger than 8mm. Or even a 9mm, but you might need to grind a start before hammering it in fully.

 

[Burnerman]

As above, the trick is to bray in an imperial size key and then say a prayer or two.....give the bracket a shove to and fro - it will relieve some of the tension on the bolt - but not much!
John

 

[dmccormick]

The next complication seems to be that you have to remove the hub nut to take the disc off. It looks like the bearing is part of the disc itself ?

Does that sound right ?

 

[Burnerman]

Personally I cant speak for your A4, but the vast majority of discs are separate from the hub.
Do you have a picture of the replacement part, or the part itself yet?
If the disc is separate there should be 2 torx screws holding it on - can't see any in this case so it would seem that its in one piece - complete with the ABS reluctor ring.
If it has to be taken off, undoing the hub nut allows it to pull free.
John
Just edited this one.....can you post a close up of the centre nut?
J.

 

[dmccormick]

Haven't got the new disc yet as haven't got the old one off yet to see if I need new ABS ring or not. (waiting for my bolt extractor to arrive...)

It was just that I saw a post here where it looked like you have to take the hub nut off and the bearing is attached to the disc.

Car has been making a whining noise at speed so might be worth replacing bearings anyway if it's not a big job

However, yet again car parts site shows two different bearings for my car (eurocarparts nos 628440500 and 628440770) so not really sure which it would be.

 

[Burnerman]

Hell, that sure does look like its one bit - and I thought VAG had stopped using taper roller bearings ages ago!
No wonder the bloody thing whines - they always did and yes, there are two sizes! A motor factor should have all you need there, and knocking out taper roller races is dead simple....the outer race is smaller than the inner so its easy enough to get in with a flat ended drift.
John

 

[dmccormick]

They probably did - I bought the car new in 1996 and haven't seen any reason to change it yet !

 

[Burnerman]

I bet the other sides a rumbler too!
Lets know how things go and do have a successful day.....those calliper bolts are a right PITA and put hours onto the job.
I would recommend dealer replacements though, due to thread and shoulder lengths - unless you have some identical ones kicking about.
John

 

[Mursal]

Yes 2 different types listed
http://bit.ly/19WorpF

One complete, one splits

The one that splits has as John said a 5th hole for the retaining screw. So clean the copper grease off and double check for a recessed screw, on the surface of the disk where the wheel rests.

The bearings are a soft spot (always noisy) but you have a fine car, well worth keeping.
The bearings are very reasonable new, bit fiddly to tap in and don't forget to grease well. Tighten the nut just to eliminate all inward/outward slap in the top of the wheel. Its the split pin that actually holds the wheel on, so a new one is recommended, every-time.

 

[dmccormick]

Have managed to identify the correct bearings from the vagcat parts catalog.

Just wondering, if I manage to get it all apart which type of grease to use on which bit. I understand I need silicone grease for the caliper slide pins, copper grease for the back of the pads, not sure about the bearings.

Also, would you put any grease or threadlock on the dreaded calliper bracket bolts ?

 

[Burnerman]

Where there's rubber parts, use a red rubber grease or equivalent. (Calliper slide pins).
For the bearings, high melting point multi purpose grease will be fine.
Coppaslip on the back of the pads, and on the pad sliding surfaces (clean the calliper bracket up with a file when you get it off - there will be quite a bit of rust there).
A bit of threadlock on the (new) caliper bolts (they will come with locking compound already on, likely as not) and a thin smear of grease on the bolt shoulderYour new bearings should come with a new split pin, retaining cap and grease seal.
John

 

[mfarrow]

^^ What he said!

 

[dmccormick]

Great. Thanks for all the help. I've managed to get the bolt out by drilling the head with a 9m drill bit - the rounded hex hole was a perfect pilot hole !
Once I got into it, the head just tapped away and after removing the hub nut I could get the whole lot off.
The petrol tank is in the way on the other side so I'm off to get an angled drill shaft to do the same on that side.

The ABS rotor separates from the disc so I will just get the disc and bearings kit.

The calliper slide pins on the left side are completely seized but the pads are evenly worn, whereas on the right hand side the pins are free but one pad is down to metal. Would have expected it the other way around,

 

[Burnerman]

Looks like you are getting there mate so well done on that one.....I guess the pads on the other side were even thickness because they weren't actually working
After this, you'll notice the brake pedal is a lot less 'wooden' to the feel and the handbrake will have that sprung return.
You'll be aware that the calliper pistons have to be rotated as they are pushed in.....you mustn't heave them back.
John