Guide Pins - Grease?

[bradjsmith88]

Search and Google have given me so many different responses i've given up and i'm asking!!!

I have a 2001 BMW Z3 which I suspect has a sticky front caliper.

To investigate I'm going to take off the caliper and give it a good clean including the slider/guide pins.

The questions are:
a) Do I grease them?
b) What grease do I use.

I have some Pagid CeraTec and some White Lithium grease - are either of these suitable? I understand they need to be rubber safe due to the design of the calipers.

Thanks in advance.

[brrapp]

I always use copper slip for all brake components. I know you're not supposed to use it on slide pins as it can supposedly soften the rubber seals but I've been using it for over 30 years and not had a problem.
Either the caratec or lithium which you've already got should be fine or red rubber grease.

[DuraAce]

I've used bosch superfit for the last couple of brake jobs. No problems at all.

Saying that, I've used copperslip prior to that for 20 years without a problem!

[E-bmw]

Yes grease, either will do fine but I would use either ceratec or generic silicone grease.

Yes copper grease will do it but is technically not ideal it is FAR better than nothing.

[bradjsmith88]

Thanks all, duly noted!

[helix402]

Despite internet folklore the caliper is probably sticking due to a rusty piston rather than a guide pin problem.

[bearman68]

bradjsmith88 said:

Search and Google have given me so many different responses i've given up and i'm asking!!!

I have a 2001 BMW Z3 which I suspect has a sticky front caliper.

To investigate I'm going to take off the caliper and give it a good clean including the slider/guide pins.

The questions are:
a) Do I grease them?
b) What grease do I use.

I have some Pagid CeraTec and some White Lithium grease - are either of these suitable? I understand they need to be rubber safe due to the design of the calipers.

Thanks in advance.

Irrelevant. Guide pins are stainless with rubber bushes, don't need lubrication, but lubrication doesn't harm. I use Tunap ceramic grease, after cleaning the guides.
Horror of horrors, I normally ease the pads into the holders with a file as well, to make sure they are loose enough,and then grease them with the same grease, on the contact points.
And I would change a caliper that's sticking - this is prob where the problem is anyway. Almost certainly aint the guides.
And don't forget to clock the discs if you are changing them.
Glad I got that off my chest.

[GreenV8S]

bearman68 said:

Guide pins are stainless with rubber bushes, don't need lubrication, but lubrication doesn't harm.

Are you talking about pad retaining pins, or the slider pins used to mount single sided calipers? I think the OP is asking about the slider pins, which are a metal on metal sliding joint with a considerable load on and definitely need lubrication.

[thebraketester]

IANAE but I use ceratec on everything on brakes, and on the back of pads etc. Brilliant stuff.

Did the rears on mine a few weeks ago and used ceratec on the slide pins.

[bearman68]

GreenV8S said:

bearman68 said:

Guide pins are stainless with rubber bushes, don't need lubrication, but lubrication doesn't harm.

Are you talking about pad retaining pins, or the slider pins used to mount single sided calipers? I think the OP is asking about the slider pins, which are a metal on metal sliding joint with a considerable load on and definitely need lubrication.

Sadly I just checked on the brake design to make sure I hadn't got confused.The brakes are a single caliper, mounted on a pair of screw in shafts. As the brake comes on, the braking pressure is equalised on both sides of the disc by sliding on the shafts (pins),so my previous comment I think is correct. The pad locates into the brake carrier, and it is these I normally ease, and lubricate tomake sure they don't jam or stick. So I'm not sure what the metal on metal slider pins are sorry.
Here's the pic I was looking at.
http://www.ebay.co.uk/itm/Brand-New-BMW-3-Series-R...

[GreenV8S]

bearman68 said:

Sadly I just checked on the brake design to make sure I hadn't got confused.The brakes are a single caliper, mounted on a pair of screw in shafts. As the brake comes on, the braking pressure is equalised on both sides of the disc by sliding on the shafts (pins),so my previous comment I think is correct. The pad locates into the brake carrier, and it is these I normally ease, and lubricate tomake sure they don't jam or stick. So I'm not sure what the metal on metal slider pins are sorry.
Here's the pic I was looking at.
http://www.ebay.co.uk/itm/Brand-New-BMW-3-Series-R...

I'm not familiar with these BMW calipers. My experience is with Fords, but they look similar and I don't suppose they are very different. The slider pins I'm referring to are the pins that connect the caliper to the upright. They screw into the upright, the caliper slides over them. They will probably have either sliding seals or bellows to keep the dirt out, but I expect the bearing surface itself will be a metal bushing. The sliding joint is very heavily loaded and slow moving. The ones I'm used to are definitely designed to be greased and I'd be surprised to see one that is designed to run dry.

[helix402]

The 7mm bolts on BMW should not be greased if you want to follow BMW instructions. If you grease them though the world won’t end. Unless you use Copperslip, which is pants and horrible and from a by gone era.

But if you like it and have used it for 25 years great. However I’m not having a pointless internet argument about the pros and cons of Copperslip.

[bearman68]

GreenV8S said:

I'm not familiar with these BMW calipers. My experience is with Fords, but they look similar and I don't suppose they are very different. The slider pins I'm referring to are the pins that connect the caliper to the upright. They screw into the upright, the caliper slides over them. They will probably have either sliding seals or bellows to keep the dirt out, but I expect the bearing surface itself will be a metal bushing. The sliding joint is very heavily loaded and slow moving. The ones I'm used to are definitely designed to be greased and I'd be surprised to see one that is designed to run dry.

No, the metal pins run in a rubber bushing, and as said, shouldn't be greased (though I usually do, as it makes them easier to reassemble) Forgive me for saying so, but the sliding joint isn't heavily loaded - the braking torque is reacted by the pad in the carrier - at least as far as I understand it. That's why the pins are rubber mounted - to allow a degree of motion,and prevent the braking torque being applied to the pins, and not to the pads. The pins are I think an M9 fitting,so won't take much load.

Just as I see it.

[GreenV8S]

bearman68 said:

Forgive me for saying so, but the sliding joint isn't heavily loaded - the braking torque is reacted by the pad in the carrier - at least as far as I understand it. That's why the pins are rubber mounted - to allow a degree of motion,and prevent the braking torque being applied to the pins, and not to the pads. it.

Maybe BMW have a better design which doesn't rely on the pins being stiff. On the Ford ones I've seen the slider pins wear out over time and tend to jam, causing all sort of strange problems. I haven't seen what happens under braking but I suspect the caliper is flexing and trying to twist the piston assembly relative to the upright - the sliders would be trying to prevent that. Just based on the pad wear I can see there has been a lot of flex under heavy braking.

Anyway, if the contact between the pins and the moving part of the caliper is metal on plastic then I agree it can't be carrying much load and perhaps doesn't need to be greased. The ones I'm familiar with definitely do need to be greased, though.

[Mr2Mike]

bearman68 said:

No, the metal pins run in a rubber bushing,

On your calipers perhaps, but that's not common IME. Not a single one of the cars I've owned has had rubber bushes in the sliders, just rubber bellows to prevent water and dirt ingress.

[Krikkit]

No harm in greasing and cleaning everything OP, but I suspect as noted above it's a sticky piston - chances are a rubber boot has a small split and has allowed water ingress, so the piston has corroded enough to be awkward.

IME quite common on front calipers/where the piston doesn't twist as it's extended (like a lot of Bendix rears).

[bradjsmith88]

Thank you, I suspect the same but it's a very slight issue at present, so no harm in a clean up, and ill likely change the caliper next month when I have some time off.

Thanks to everyone who has replied, interesting that there really isn't still a consistent answer, seems to be personal preference.

From what I have deduced:

BMW TIS states no lubrication needed.
But most people lubricate in any case as it doesn't do any harm.

[helix402]

Spot on. Unless you use Copperslip which is grease of the devil.

[kev b]

Theres no need to replace the caliper in the majority of cases, you ned to remove the piston and both rubber seals and clean out the dirt and corrosion in the groove the seal sits in.

I use a brass brush on my dremel but scraping it out works, it just takes longer, polish up the piston and use rubber grease when you reasemble it.

If the piston has rust pits or the dust seal is split then its better to buy a new caliper but IME sticking pistons are usually caused by corrosion under the seal. BMWs seem particularly prone to sticking pistons which can cause all sorts of steering weirdness. Pulling to one side, steering wobble, darting under braking and tramlining are often the reult of a sticky caliper.

It goes without saying that the slider pins must be free, I use rubber grease on them as it probably helps prevent water ingress from puddles or pressure washing.