What Does the Slide Pin Rubber on the Lower Brake Caliper Bolt Actually Do?

Wondering what the sleeve on the lower brake caliper bolt does? This article reviews what the lower brake caliper bolt’s slide pin rubber is and it’s purpose.

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brake caliper lower bolt slide pin rubber sleeve

Why Is There a Rubber Sleeve on the Lower Brake Caliper Bolt?

If you have ever had the pleasure of doing a brake job on a rusty car before, you have likely encountered the engineering nightmare that is known as a “lower brake caliper slide bolt.” Now, if you have erased this hardware-laden memory from your brain, or aren’t familiar with this style of bolt, I’ll do my best to help out.

This is the type of bolt that doesn’t want to come out of its hole because rust has essentially fused it with the brake caliper bracket. It’s the bolt that gives you a few hope-filled turns with a pipe-extended, half inch drive ratchet, and then crushes your dreams when it becomes stuck solid for absolutely no logical reason. It’s the threaded evil that requires a chisel and sledgehammer to remove when the ratchet fails to do its one job. Yep. That’s the bolt we’re talking about here today.

A Theory: The Brake Caliper Slide Pin Rubber Is an Anti-Rattle Device

If you have ever successfully removed this bolt (which not many have in the Northeast), you know that it has a rather cute little rubbery sleeve on the end of it as if to mock each one of your herculean removal efforts. The upper caliper bolt does not have this cute rubber sleeve, so why in the world did the car manufacturer put one on the bottom caliper bolt? The truth is, I don’t have an answer for that. However, I have spent quite a few late night hours in search of the truth, and I’m now here to share with you the one theory that makes the most sense to me.

These cute little rubber caliper bolt “sleeves” (that’s the most common name for these) are anti-rattle devices for the calipers.  The sleeve provides additional friction, which prevents the brake caliper from rattling/chattering within the confines of the caliper bracket. It works similarly to a shock absorber, where it slows down and dampens the movements of the calipers.

As long as the whole system stays rust-free and lubricated, it’s truly a simple and effective system. However, when that rubbery sleeve prevents the caliper bolt from sliding, or rust begins pulling the vehicle back into the earth, all bets are off.

What Do You Think?

So does this theory make sense? Do you have a better explanation of what the rubber caliper bolt sleeve actually does? Tells us in the comment box below.

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What Does the Lower Brake Caliper Bolt's Slide Pin Rubber Do? - 1A Auto
Find out what the slide pin rubber sleeve on the lower brake caliper bolt does in this article where our expert gives one theory
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Jeremy Nutt

Hi, I'm Jeremy.

16 thoughts to “What Does the Slide Pin Rubber on the Lower Brake Caliper Bolt Actually Do?”

  1. Pivot pin. Loosen it, remove the other for new pad install and when bracket needn’t be fully removed.

    1. Hi. I thought the same but noticed the rubber sleeve locks air in which pushes the pin out. In my humble opinion this creates the opposite effect as it pushes the caliper out too far and causes the outer shoe (one closer to the rim) to ware more than the other. Just another theory perhaps.

  2. That rubber piece is EXACTLY what it is a dampening device to stop the pads from rattling. Nothing more nothing less. It will seize because of LACK of the proper lubricate. It needs proper lube which will not cause the rubber to expand or swell. Another issue is environment, harsh winters and corrosion and bad seals. Sure they will eventually seize. Preventative maintenance goes a long way.

  3. Rebuilt calipers for 2001 Corolla has rubber sleeve on TOP pin.
    I’ve seen a video a mechanic removed them from 100 cars with no problem.
    They were seizing brakes, getting stuck etc. No problems reported from his customers….

    1. The last shop that did my brakes removed all of the rubber sleeves from the guide pins on my 2009 Nissan Murano and the brake started singing like an opera singer after only about 15K miles. I purchase and installed the sleeves and the problem was gone. My two take-aways are: 1) I guess the engineers that specialize in, and designed, the brake system knew what they were doing and 2) I wonder if your mechanic is not hearing of problems from customers because they’re going someplace else for their next brake-job because the last one resulted in squeaky brakes.

  4. I’ve had a hard time removing my rusty pins out, and only the ones with the inner boot, and it probably was most likely due to extreme pressure created by deteriorating/expanded/loose/and breaking apart rubber jacket (in addition to rust problem.)

    I cleaned the rust, then tried to installed with the old rubber sleeve all packed with gooey grease the above mentioned pin back to no avail–it would stick and wouldn’t go in as the rubber jacket slid. One can observe the jacket being really loose and sliding easily due to rubber deterioration and edges of it frayed.

    After few futile attempts the rubber jacket finally tore into two pieces. I threw one away and left the other half of it on. With less rubber friction the pins moved freely! Viola. Such a relief. I went with that and assembled everything together (new rotor and break pads having been installed.)

    It works fine but I am sure the pins slide more freely than they were designed for. It is all hard to say with surety, but I thought I heard brakes snap back a few times when breakes were released as I drove… only a few times.

    Here is the crux of the matter–I think they prevent the snap back effect, which could be construed as a ‘rattle’ as some have pointed out. The release of the breaks causes sudden depressuarization in that break system arrea, and I believe it is not gradual.

    With time, my ‘half-rubber-tube’ jig might become the ‘new normal’ as the friction increases due to loss of grease and rust issues.

    All said and done, I did order new two sets of rubber boots/jackets (just in case and made by different manufacturers and they do have different shapes) and two new sets of pins (total of 4) for both wheels…for whenever I may get to do them again normally or if they start sticking again.

    There is no huge reason to buy whole remanufactured caliper set if your pistons are compressing all right with an extra large pliers or a special tool–that means your pistons are working fine. You might be able to get by by spending around $35 total for two wheels on Amazone, like I did, speaking here for four pins and one set of four boots and two jackets.

    I hope this helps someone in their adventure.

  5. Just as you described. I did the brakes on my Delica L400. Four solid slide pins and 4 with sleeves. Two of the sleeved ones came out with no problem. The other two were a nightmare. Turned hard with a breaker bar throughout the whole threaded section. Then used a thick adjustable spanner (“Crescent” wrench) as a wedge between the bolt head and the caliper and kept turning the bolt. Added more wedging until the bolt was at least half out. (half hour later) Then it finally wiggled free. The sleeve was still inside the carriage on one bolt and I had to fish it out with a wire. Weirdest part was that after a quick wipe with a cloth, the pin and sleeve pushed in and out with little resistance. No big globs of rust or anything were wiped off. It was just really dry. Honed the inside of the carriage hole with some emery on a folded over coat hanger. Put it in a drill and it cleaned up really quick.
    Note: I watched one video where the guy suggested to not lube the ends of the pins as it tended to push the pins back out. I’m guessing that may initially be the case but the pressure would eventually equalise and then work as an effective damper. My sleeves have grooves in them parallel to the pin axis so as to relieve pressure I assume.

  6. Obviously it requires very high precision to have both guide pins moving smoothly in their respective hole. The pin-to-hole precision would be easily achieved if there were only one guide pin. But as we have two guide pins operating in high temperaturen we can’t have the tight fit on both pins at the same time.
    So in my mind it is obvious that the pin without rubber has a very high pin-to-hole precision and the other pin with rubber must have less precision for it to fit into it’s hole. This lack of precision is compensated by the rubber which also prevent noise/rattle.

    So in other words: one pin is for high precision fit, the other pin with rubber is to absorb the tolerance when fitting two pins in cohesion.
    Placing the rubber pin in top or bottom position does not make any difference, it will have it’s tolerance absorption function anyway as the drill holes has the same dimension.

    1. Martin, I’m 100% with you on this. You can’t have two precision fits and expect them to stay in tolerance during mass production. Without the rubber-bushed pin to compensate for tolerance stack-up (just as you’ve described), you could have a situation where the pins would be tight in the bores because they were not the same center-to-center distance as the bores are. Thank you for your accurate answer!

  7. On a 2015 Cadillac XTS V-sport, which calliper pin goes up or in the down position on front and rear? TIA

  8. I’ve read about this widely and I’ve got a conjecture (I may be wrong but I’m a non-auto design engineer):

    I think there may have been a design change in which both pins were changed to include the rubber. I think it would be at the top rather than the bottom of the pin if it was anti-rattle? (another theory would be they put it at the bottom to help avoid it swelling). The idea would be that the air cushioning would improve the behaviour of the brake pad on initial and final contact with the brake disc. Having the rubber on both pins would give the most even performance. However I conjecture that this actually caused rattle due to the need to have a less tight pin (again this might have been a flawed solution to the swelling issue?). So, perhaps even to save face, one of the pins was replaced with a non-rubber pin.

    All conjecture, but I smell some sort of flawed design followed by face saving. One mechanic says he doesn’t put the rubber on and has had not a single complaint over the years by his customers.

  9. i removed it and installed a plain pin matching the other side to not have to deal with it again, no issues after

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