What grease for brake caliper guide bolts???

[I-S]

K - let me know. I've acquired new front discs, have pads ready to go, etc.

If there's a sticking issue with copaslip then could this have contributed to the death of my brake disc by getting pad dragging? Only the OS disc is affected it seems...

Got time next weekend? I should have the discs by then, have the pads, shims, Amsoil GHD....

[I-S]

Testing?

[Kieran]

Got time next weekend? I should have the discs by then, have the pads, shims, Amsoil GHD....

Sorry Isaac - as I think Alex has said somewhere else - we're busy the next three weekends in a row! Suffice to say there will again be the sound of clattering in the air at Japshow time!!

[I-S]

No probs, I will see what I can do.

[Kieran]

Well, as promised, here's the reasons behind my ealier statement - What I don't understand is why this has happened.... All the seals were intact and such, but nonetheless, the results are plain to see. Anyway, more discussion later.

Here is the vicious bast@rd that was causing me such grief at the weekend.... The little fecker wouldn't come apart! The sliding bolts were siezed, and one of them would *NOT* undo at all!!

[Kieran]

Anyway, I finally prised the caliper away from the housing, and managed to unscrew one of the pins.... And I saw a disturbing sight.

This is one of the pins from the nearside rear caliper. The rears haven't had any attention before in either my tenure or Nick's. So, to be fair, this is really just one of those things - what the eye doesn't see and all that.....

[Kieran]

More disturbing was the fronts.... At the end of last July, I had to make an emergency pad change and when I rebuilt the caliper I smeared a good amount of copper anti-sieze on the pins, and they were sliding quite freely when I reassembled them.

However..... 10 months later and the same pins look like this......

[Kieran]

However, the offside rear caliper (again, untouched since December 2004 at least) was still free and sliding very well.... And when I took the pins out, there was a good coating of grease still on them.... But what the hell kind of grease is it?!?!?!

[Kieran]

So... There you have it.

Well, there are several posibilities..... Here's the ones I can think of:

1. I haven't inspected the brake pins often enough.

- this is certainly possible, but when you consider the length of time that the brakes SHOULD operate for without being looked at, this isn't likely...

2. The grease I've been using isn't up to spec.

- Certainly possibe. It was copper grease, made by Granville - so it's not the pukka Copaslip, but it *should* be up to the job.... But is it?

3. I've used the wrong type of grease.

Well, the grease on the only pair of pins that were still serviceable was certainly not copper grease.....



More research required.

[Kenneth]

I always thought that you just used standard GP (General Purpose) grease on them...

[Kieran]

I always thought that you just used standard GP (General Purpose) grease on them...

Hmmm..... Don't think so!!

[I-S]

GP grease will last two or three stops before breaking down from temperature.

I HAVE THE ANSWER

http://cgi.ebay.co.uk/ws/eBayISAPI.d...MEWN%3AIT&rd=1

On it's way to me

[I-S]

I've also just sold my soul for some new caliper pins from a main stealer.

[I-S]

At the risk of talking to myself.... Camskills sell it too: http://www.camskill.co.uk/products.p...7b32s1209p5833

[I-S]

Right, I've just finished doing my front brakes.

Both guide pins were very dry, but the lock pins were ok. Kieran used copper grease on them when we sorted them out last time. One guide pin was very stiff indeed.

I replaced all the pins as well as the pads and discs. However, the particularly stiff pin remained so, so I think it's an issue with the seal in that caliper. There were other problems I found too though, like a pad that was badly bound in the caliper. Nearside brake was fine, with perfectly good wear levels on the disc and pads, but the offside disc is really screwed, and some impact on pads (although still loads of material left on them). All pads rather glazed though.

And to the Ceratec. Lovely stuff. It's a translucent yellowy-green grease, and feels more slippery than copper grease. Time will tell how it performs. Brakes aren't squealing though.

I asked about grease this morning at the mitsu dealer when I picked up the pins. They said they use copper grease, or some stuff from millers.

[Kieran]

Mmmm! Interesting info Isaac. Will be interested to see how the cera-tec holds up.

So that's two black marks against copper grease...

[Kieran]

Okay, I think I've finally pinned this one down, worked out what grease(s) we should use, and which ones to avoid.

I must say thankyou to the Mitsubishi FTO boards - Seems they have similar issues, and my information below is distilled from several postings on there - thanks guys.

Curiously, it's not mentioned anywhere much on the MLR though.

Anyway - let's deal with Copaslip and related products first and explain why they're great for nuts, bolts and the back of pads, but no good for sliding pins.
The main reason is that it's an 'anti-sieze' compound - not a lubricant. Yeah, I know we need to stop the pins siezing, but copper slip isn't the way. It's too thick (resulting in 'stiff' operation when new) and when exposed to temperature changes, it quickly degrades - leaving a horrible gloopy mess behind that doesn't help your caliper pins.

Now, you may be wondering why it's good on bolts in high temperature situations. Well, that's easy to explain. You coat the threads in copaslip, and wind them in. Even if the grease fails, the copper in the grease is lift behind. And it's this that stops your nuts/bolts binding up - the copper helps prevent the threads rust-welding together.

Thing is though, it's no good for moving parts - that thin layer of copper won't protect a pin for very long before it's worn away, and then you're in big trouble.

There's another reason why copaslip and such are no good - they cause rubber seals to swell. And if you rememeber, one of the caliper pins has a rubber bush on the end. Get this to swell, and it'll interfere with the operation of the caliper and may possibly 'pop off' the end of the pin!

So..... What to use instead then?

Well, any hydrocarbon-based grease is also out the window. They usually have low melting points, and again, they'll cause seals to swell. So we need a silicone grease that can withstand temperatures upto around 300 degrees and provides a good film of lubricity. You don't need 1000 degree grease on a caliper body - hell, the surface of the pads probably don't get that hot!

Several recommendations have been made to me, I will be using a lithium, high temperature, synthetic based grease from Mobil, though if you can't get it, there's a Amsoil equivalent (I think it's the 2000 racing grease) that's very similar. The reason why I've gone with the mobil is it has a hligh temperature range and has a stable lubricant film, yet it's also very thin for a grease. It has also been recommended to me by a friend who uses it on their car, after similar experiences with Copaslip.

Here's the Mobil stuff:

http://secure.silmid.com/action_main...art=MOB28001LB

I hasten to add there are other greases that will probably do just as well. Some people have access to more exotic compounds, based on silver and Nickel, so get out there and have a look.


Hope this clears things up a bit.

[amsoil]

Your tenacious research is to be applauded!.
If you cannot get the Mobil military grease (as they are shown out of stock of tubs) and don't wish to spend £35+ for the cartridge I will send you a cartridge of S2000 to try (I have faith here) and its less than 1/3rd of the price of the Military spec Mobil. Have you looked at ZX1 , we stock this too.

Rewgards Don

[g6acb]

I remember talking to Isaac about this apres Mountain Biking and thought I had posted this before.. but apparently not...

the stuff I used was one of these products

http://www.rocol.com/lubricants/engl...ance/bearings/

I'm not too sure which one it was as the dude in the Bike shop gave me it in an plastic container when I had my wheel bearings fixed

Not sure if it makes a difference now as you have found the Mobil stuff....

Be Interested to know the results with whichever you go with

[Kieran]

Quick footnote to this thread.

Mintex 'CeraTec' works well on the backs of pads.

It does NOT work well on brake pins, as Isaac and I discovered! It turns into a sticky goo what stops squeal and also stops your pins sliding well!