Hi I have done a front brake caliper rebuild. New rubbers clean and paint. But I have a problem with the sliding pins seizing up.. I installed new sliding rubbers in the calipers cleaned the pins and they are mooth. Greased them both with brake grease en slide the pins into the new rubbers, I'm make sure they slide smoothly. Now here it comes when I walk away for 15 minutes they are seized again and I need a mallet the get them apart. Redoing all results in the same problem.. what am I doing wrong here?

I haven't even installed the brake pads yet.

Corrosion in the bores where the pin go into?

Arlo said:

Greased them both with brake grease en slide the pins into the new rubbers

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Brake grease? Can you be more specific? I'm wondering if you've used a mineral based lubricant on the rubbers? If so, and I've done this, they slide together quite nicely but after a wee while the mineral grease starts to make the rubber swell and it'll grip the pin. Long shot I know, but just maybe?

Shell gadus lithium grease.

I'm not familiar with that particular grease but do have past experience of Castrol LM which is a lithium based high melting point grease. It would be commonly used in wheel bearing assemblies. i would guess (and it's only a guess) that your shell grease is not compatible with rubber parts? Proper red rubber grease or maybe silicone grease would not react with the rubber.

Chris's suggestion to examine the pin bores might be worthwhile but then why would it all slide together ok initially?

Difficult to help from a distance on this one. Good luck. please let us know if you find the cause or a solution as it helps us all to know the outcome.
Jock

Pugglt Auld Jock said:

Brake grease? Can you be more specific? I'm wondering if you've used a mineral based lubricant on the rubbers? If so, and I've done this, they slide together quite nicely but after a wee while the mineral grease starts to make the rubber swell and it'll grip the pin. Long shot I know, but just maybe?

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You where spot on. i used the wrong grease. now i cleaned out the rubbers of the old grease put in the red rubber brake grease and they are good now..

Thank you for the tip!:worship:

Arlo said:

You where spot on. i used the wrong grease. now i cleaned out the rubbers of the old grease put in the red rubber brake grease and they are good now..

Thank you for the tip!:worship:

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I'm glad it's all turned out well for you. Thank you very much for letting us know. I'm going to show this post to Mrs Jock, just to prove that I do actually sometimes get things right! Ho, Ho.

From my experiences and practice I do/use the following:

1) For calliper piston and seals only ever use the correct brake grease compatible with brake fluid. This is normally red in colour.

2) For all other brake parts (piston rim outside of dust shield, back of pads to piston contact rim, guide/slide pins, etc) I use molly grease AND NOT copper slip.

3) For wheel boss / hub interface I use molly grease

Molly grease is high temperature (as already pointed out) and water proof and water resistant. It is also compatible with rubber components hence its use in bearing, bearing seals, CV boots etc.

The problem with copper slip is it:

1) tends to dry out
2) does not like water (which is exactly what it will get in the wheel arch)

I learnt from a very long time ago on those early Fiat/Bendix callipers that used "fish plates" to hold the callipers in the carriers and allow then to float that every time I used copper slip I had all sorts of issues especially after wet winter periods. I switched to using molly grease some 40+ years ago and have never ever had any issues even on our cars we did motor sport in where the brakes, hubs and wheel rims were hammered with heat.

I'll add a word of caution when using molly grease in or around brake components. Only the thinnest/smears of the grease. You are not trying to pack a bearing or CV joint.

I also use molly grease on just about every nut, bolt, head bolt, screw, self tapper trim screws, etc. One possible exception is Nylock nut and bolt/stud interfaces. So for say a suspension strut bolt I'll apply molly grease to the whole bold shaft and thread up to around mid position of nylock nut body/length. Torque up as required. Now the nylock is placed/locking onto a grease free thread. I'll then put a smear of molly grease over the bolt length protruding beyond the nylock nut. All very tedious and possibly OTT but well worth the effort which will be repaid several times if you ever have to revisit years later.