Why are my brakes still "grabbing" after disk/pads replaced?

[technicalfoamboy]

Advice please........

Car is BMW E46 330CI 2004. A few months back whilst braking the steering wheel would judder so I assumed disc(s) had warped.

Sourced new Bosch discs and pads and all was fine for a couple of drives then judder reappeared.

It "feels" more like the brakes are grabbing i.e., when pressing the brake pedal the pads are not flush with the disc? But I suspect that could be the same sensation as a warped disc?

Or, is it something else considering new hardware and issue is still there?

Has something contributed to perhaps uneven wear of pads/disc? I think it's just the one side though not both.

P.S. Single piston calipers.

Thank you in advance

Edited by technicalfoamboy on Thursday 1st December 16:57

[Pieman68]

Did you check that the caliper pistons were functioning properly? Did they retract fully when changing pads?

[technicalfoamboy]

Pieman68 said:

Did you check that the caliper pistons were functioning properly? Did they retract fully when changing pads?

Thanks Pieman68.

I forced them back in so as to get the pads out, is that what you mean?

[georgeyboy12345]

They all do this. BMW’s have crap brakes, ime. Same with Alfa Romeos. Still good to drive though

[Scootersp]

Could be the flexi brake hoses. I had it with my BMW

https://www.bimmerforums.co.uk/threads/645-front-b...

[Heaveho]

Did you replace the discs yourself? Were they cleaned of the protective coating properly before fitting. Were the hubs cleaned of corrosion properly before the new discs went on? As said, are the calipers free? A runout gauge will tell you whether or not the discs are running true.

If the answer to all of the above is yes, then find somewhere quiet and bed them in properly. You may have already managed to have pad material transfer to the discs unevenly. I managed to clean up the discs on my Evo with several 100 mph, full on the brakes down to 30 sessions. Mine were pretty close to being on fire at the end, and the pedal all but disappeared at the end of it, but it fixed it. The difficult bit is then not using them again until they've cooled down, that's the hardest part of the whole procedure.

[Scootersp]

Also I don't know about the 330's but the 6 series everyone recommended the genuine ones over any aftermarket.

[Pieman68]

technicalfoamboy said:

Pieman68 said:

Did you check that the caliper pistons were functioning properly? Did they retract fully when changing pads?

Thanks Pieman68.

I forced them back in so as to get the pads out, is that what you mean?

Yeah, if you had to "force" them back it could mean they're stiff. Then when you've applied the pedal they've maybe not retracted and that's why they're grabbing

[technicalfoamboy]

Scootersp said:

Could be the flexi brake hoses. I had it with my BMW

https://www.bimmerforums.co.uk/threads/645-front-b...

Great shout Scootersp! thanks



Any other ideas

[technicalfoamboy]

Pieman68 said:

Yeah, if you had to "force" them back it could mean they're stiff. Then when you've applied the pedal they've maybe not retracted and that's why they're grabbing

I will dismantle the brake system this weekend and start from scratch refitting discs/pads.

What should be the correct procedure (I did follow a YouTube vid) in detail? Just so I can be reassured I've done it right and therefore if it reoccurs then it could be a problem elsewhere.

I'm especially interested on how to check everything is OK and as it should in each step of the installation if that makes sense?

P.S. I do recall somehow that to undo bleed screw to let out a bit of brake fluid/ease the pressure or something like that. I didn't do that this time, is that something i should also consider doing this weekend?

Edited by technicalfoamboy on Thursday 1st December 17:20

[Draxindustries1]

It could well be rust which wasn't removed on the hub before the new discs were mounted. Ideally these should be either wire brushed or cleaned with emery paper like 120grit to make sure there's a perfectly flat mating surface.

[technicalfoamboy]

Draxindustries1 said:

It could well be rust which wasn't removed on the hub before the new discs were mounted. Ideally these should be either wire brushed or cleaned with emery paper like 120grit to make sure there's a perfectly flat mating surface.

Thanks, I did clean hub with wire brush and cleaned disc with brake cleaner to remove protective coat.

[andygo]

Seems odd that the issue has replicated itself after doing a few miles with new parts fitted.

I'd undo the chrome slide pins completely out of their rubber sleeves and make sure they are clean and can move easily. If they are corroded that 'might' be the issue.

Try getting a sheet of medium sandpaper (or a concrete or a paving slab!) and rub the face of the pad to deglaze them

How did you bed the new discs and pads in? If you were over aggressive, you might have glazed the pads or warped the discs. Discs prefer a few reasonable heat cycles in my experience. Only saying this as I used to help develop carbon brake pads on my rally car for Mintex lots of years ago.

https://www.ferodo.co.uk/blog/give-brakes-a-break....

https://apecautomotive.co.uk/techmate-guides/beddi...

Edited by andygo on Thursday 1st December 17:33

Edited by andygo on Thursday 1st December 17:34

[Krikkit]

Fit a set of refurbed calipers and new flexi hoses.

If you didn't clean the hubs before you put the new discs on make sure you put them back in exactly the same spot.

[technicalfoamboy]

andygo said:

Seems odd that the issue has replicated itself after doing a few miles with new parts fitted.

I'd undo the chrome slide pins completely out of their rubber sleeves and make sure they are clean and can move easily. If they are corroded that 'might' be the issue.

Try getting a sheet of medium sandpaper (or a concrete or a paving slab!) and rub the face of the pad to deglaze them

How did you bed the new discs and pads in? If you were over aggressive, you might have glazed the pads or warped the discs. Discs prefer a few reasonable heat cycles in my experience. Only saying this as I used to help develop carbon brake pads on my rally car for Mintex lots of years ago.

https://www.ferodo.co.uk/blog/give-brakes-a-break....

https://apecautomotive.co.uk/techmate-guides/beddi...

Edited by andygo on Thursday 1st December 17:33

Edited by andygo on Thursday 1st December 17:34

Thanks andygo, I did remove and clean/sand down before refitting. I will check them again to see if there is anything obvious

[andygo]

technicalfoamboy said:

Thanks andygo, I did remove and clean/sand down before refitting. I will check them again to see if there is anything obvious

Heres a bit more:

https://apecautomotive.co.uk/techmate-guides/brake...

[Draxindustries1]

technicalfoamboy said:

Draxindustries1 said:

It could well be rust which wasn't removed on the hub before the new discs were mounted. Ideally these should be either wire brushed or cleaned with emery paper like 120grit to make sure there's a perfectly flat mating surface.

Thanks, I did clean hub with wire brush and cleaned disc with brake cleaner to remove protective coat.

In that case imo it's the caliper pistons sticking. I'd remove the calipers , remove the pistons ,check the bore for any corrosion or surface damage and if okay put them back together with a caliper rebuild kit.
These are cheap as they usually just comprise the piston rubber seal and dust cover.

Ebay- 332637440936
Sorry its not a direct link. This kit includes everything needed Inc new pistons for under £30..

Edited by Draxindustries1 on Thursday 1st December 18:48

[Griffith4ever]

technicalfoamboy said:

P.S. I do recall somehow that to undo bleed screw to let out a bit of brake fluid/ease the pressure or something like that. I didn't do that this time, is that something i should also consider doing this weekend?

Edited by technicalfoamboy on Thursday 1st December 17:20

Well worth buying some fluid, and an eazbleed kit if you are going to DIY brakes.

I shy'd away from touching the brake lines when doing discs and pads for years, but you really shouldn't - its dead easy to work with brake fluid, lines, and bleeding. I've always forced calipers back with a long screwdriver and pice of wood too, until I got my off roader (bike) and needed to remove a caliper to service it. That gave me the confidence to do the same on cars.

- bleeding brakes (You NEED to learn this with KTM enduros....)
- removing brake hose from caliper (clamping), then working at your leisure on caliper on bench
- rebuild caliper with service kit (seals etc)

All you have to do is bleed the brakes once done with your caliper work - and it's a pice of piss with two of you, OR, on your own with an eazybleed kit.

I've refereshed the fluid on several of my cars now on my own - just dont' use a tyre inflated to 30psi with an eazybleed - you'll find out why..... :-)

[Xcore]

Seized sliding mechanism?!

[Baldchap]

Xcore said:

Seized sliding mechanism?!

Or so filthy they stick.