Front disc brake question - lubing the pins
 

Hi guys,

Working on an 04 Ranger FX4 Level II, front brakes in particular, and I've got a question. On the caliper slide pins that the front brake calipers bolt to, how much Sil-Glyde should be applied to each pin? A super thin coat? Moderate thickness? Slober them up real good?

I've had abnormal brake wear on my front pads (all four pads are tapered AND inside pads on both sides wore faster than outside) and as much as I know this is normally attributed to stuck/binding slides, no evidence of this issue was found upon inspection. Slide pins, the rubber bushings on them and the boots have been replaced. Pin bores in caliper brackets thoroughly cleaned with brake cleaner and q-tips. Hoping for normal, MOL equal and uniform pad wear this time around. Which leads back to, how much grease is appropriate?

Thanks!

One person's moderation is another person's slobbering. :-X21

I say put as much grease as you can on them without making a mess.

What he said.

I would put just a light coat. There is literally no large back and forth motion, just the slide eventually moving to take up the slack as the brake is applied. There is then more final motion as the pad wears. The inner (piston side) wear indicates the pistons are not retracting away from the rotor sufficiently. The piston comes out, squishes the pad against the rotor, and tries to move the sliding portion(outer pad) inward in equal and opposite pressure to what is being applied to the piston side.. If the caliper won't move, the inner pad will wear, just as if the piston would not retract. The outer pad will have less wear as it is not getting pushed against the rotor, or has less pressure due to the corrosion on the sliding surface.
The old calipers on my truck got rusty on the sliding surfaces and the 'pins', though the 'pins' appear to be chrome plated metal glued to an inner chunk of 'rubber'. I had been using wheel bearing grease successfully for years, and tried some 'silicone' brake grease, which apparently led to the corrosion. I used a wire wheel to clean off the rust, and re-lubed the sliding surfaces & 'pins'.
In my opinion, the grease on the sliding surfaces is to prevent rust. The motion is so small and slow over time that it is not there for friction prevention as much as rust prevention. If you have actual round pins, the same is true, and the calipers are equipped with rubber boots to prevent water and dust intrusion. They would need minimal grease also. Any excess grease that is used will fall off or get onto more brake parts.
tom

Thanks guys, this gives me something to work with.

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Let's talk about this odd pad wear I've got. I bought this Ranger with 1K on the clock, now it's at 103K and this unusual pad wear has always been there. While not impossible, it seems unusual that the pistons and slides would be sticking on a new vehicle, and on both sides. I did throw on new MC pads at about 45K and cleaned out the slides and pins. There is a rubber bushing one of the two pins on the slide, so to prevent swelling, a non-petrol lube was used.

I've always heard what you have re the cause of tapered pads and the inner pad wearing more than the outer. I have a set of meticulously cleaned and lubed (Sil-Glyde) brackets with new pins and boots. No rust on any surfaces. Gut instinct tells me that for some reason there was always a slide issue that caused the goofy wear and not a piston issue. This now goes back to the likelyhood/probability that both calipers would have sticky pistons going wayyyyy back in time.

Thoughts?

*The finish on the pins, I believe that is nickle and not chrome for $ reasons. And agreed on the motion of disc brake parts, there is hardly significant movement over the life of the vehicle on these parts. One more thing, the calipers will grab the rotor a bit when applied and move slightly, IMO slide grease helps muffle and sound and lessens what minor contact wear there is from this.

In my observations the piston side pads always wear down faster then the outers on all the vehicles I have worked on, any maybe that's why the wear indicator is always on the inner pad.

I would think that the fact that the pistons are retracted only by the twist in the seal, they would tend to stay closer to the pad. The outer pad & movable slide are more reluctant to move than the piston as there is more friction and the motion is only in response to the inner pad already being in contact with the rotor. The outer won't move until the inner has contacted and started to build pressure. FWIW. I think.
tom

Thanks everyone, and yes, I couldn't agree more with both the observations and operation on discs. Now if it were only possible to somehow test my current calipers for sticking, given that the slides aren't. There is no drag on the front brakes when the vehicle is raised and each wheel is spun and there is no noteworthy heat on the calipers. Something has been *strange* since this vehicle was new, the result being tapered pads on both sides and the thinnest being the leading edges (meaning, when driving forward the first part of the pad touched by the rotor) of the inner pad.

Example:

Left side inner: .155" / .256"
Left side outer: .255" / .234"

Right side, similar.

If you put too much lube on the slide pins they will hydro lock Just clean the pins and bores well and litely lube.

Yup, I was suspicious of that, especially with one of the slide pins having that funny rubber sleeve on it. Cerami-Glyde, FTW!

It's been awhile since I'd looked at those slides. There is less space in there than I had thought, it would be pretty hard to really slobber a lot of grease in there. Now if there were only a logical explaination for the taper on the pads to be replaced. No sticking slides and no sticking calipers. Go figure.

How is your wheel bearing free play????

There is none. It's the latest rendition of the no hubs, sealed bearing unit.

Ok, are these single or dual piston calipers????

Dual. Ford implemented duals in 1995 and up for Ranger and Expl. Just went out there and as part fo the brake job, pushed them back in at the same time with a c-clamp. No sticking/hanging.

OK, you read my mind about sticking/dragging pistons. Edit: Maybe its time to consider replacing both sides with loaded calipers????