Question for the pros

[txrider]

I'd like to pose a question about brake caliper seals and lubricating- I've read somewhere about using an application-specific lubricant for lubing caliper piston seals to extend seal life and improve brake feedback/sensitivity so I did this using a NAPA product, Sylgard. That is after cleaning all the gunk out of the caliper, extending pistons far enough out to clean and lube as well. Due to inclement weather I've only done a short ride but the improvement was noticeable.

 

So, in my rambling way I'm getting to the point- For the experienced pros like Greg Field, Pete Roper, Todd Haven what is your take on this? Recommended? Have you tried this? Problem with contaminating brake fluid?

[Greg Field]

Sorry, TX. I have no experience with this issue of lubing caliper seals. If were lucky, one of the others will.

[todd haven]

Tx,

We use a product with a catchy name like "Brake Assembly Lubricant" made by either Bendix or Wagner, designed to aid assembly of caliper seals. Seems to work better than the old school method of brake fluid.

This is a clear to amber liquid.

 

Not familiar with Sylgard, there is a product called Syl-glyde, used for lubrcating slide pins and backing plate contact points. It is a brownish paste, works well for this purpose, but unsuitable for contact with rubber components.

[txrider]

Thanks for the response guys and you're right, Todd about the product name. As usual I managed to mangle the spelling, it is Sil-Glyde I used. Not too happy to learn it isn't suitable for caliper piston seals, however. I was mislead by the product description as being suitable for "Brake pads, calipers, rubber boots, fan belts, V-belts, weather stripping, trunk seals and bumpers, speedometer cables, window channels, hood strips and pads, and rubber gaskets".

 

Hopefully I won't see problems stemming from my woops. Brakes are too critical to be experimenting with but I had hoped to improve the brake performance another step over caliper cleaning. One brake pad was dragging a bit due to a semi-stuck piston although the calipers had had a recent cleaning (well, 3000 miles ago). A reclean and lube freed up things nicely but that's after a very limited test and few miles.

 

I found it interesting when working the pistons in and out of their bores just how stiffly and what lack of movement they exhibited even when spotlessly clean. Of course, they only have to move a very short distance ( a few thou) to do the job. The lube fixed that but for how long and with what long term results I can't be certain. I'll let you guys know as this gets more of a trial.

[badmotogoozer]

Thanks for the response guys and you're right, Todd about the product name. As usual I managed to mangle the spelling, it is Sil-Glyde I used. Not too happy to learn it isn't suitable for caliper piston seals, however. I was mislead by the product description as being suitable for "Brake pads, calipers, rubber boots, fan belts, V-belts, weather stripping, trunk seals and bumpers, speedometer cables, window channels, hood strips and pads, and rubber gaskets".

 

 

Yup. And WD-40 claims to be a lubricant...

 

We are lied to every minute of every day...

 

Rj

[dlaing]

here is a good article

http://www.aa1car.com/library/2005/ic80560.htm

[pete roper]

I'm not familiar with any 'Wonder Products' for brakes I'm afraid.

 

This is one area where I'm probably less likely to be able to offer sensible advice than pretty much anyone else. As you probably know Oz is generally a hot, dry place apart from the bits that are very hot and wet and very cold and dry . The universal thing is that we have little cold, wet, weather of the sort that requires the application of salt or other such brake seizing crud.

 

The important thing to remember is that anything that interferes with the free movement of the pistons and pads is a bad thing. The problem is that any sort of lubricant is liable to get on the pads or disks and diminish or destroy their ability to fo their task of turning kinetic energy into heat!

 

As I said, we don't have the horrible, grimy, corrosive stuff that makes all *modern* brakes bind up and seize in European winters but I do have a cleaning regieme with my brakes. Every time I have to replace the pads I will clamp all but one piston in a caliper and pump the other one out as far as I dare. I'll then clean it thoroghly with brake cleaner and a 'Scotchbrite' type spongy thing to remove any traces of manked-on dust etc. before pushing it back into the caliper. I'll repeat this with all of the pistons before installing new pads and bleeding the fluid. On the front of the Griso or any model with 4 piston calipers this is a bit boring and time consuming but it does ensure that any residual muck that has been deposited on the bits of the pistons that are proud of the seals in the caliper can't rip the seals to bits when they, the pistons, are pushed back into the caliper. Is this overkill? I have no idea but seeing as seal kits for later Brembos seem to be made of unobtanium it seems like cheap insurance to me!!!!

 

As for the lubricants? Well, if you do pop out a piston and need to re-install it or if you are simply rebuilding a rebuildable brake then I use lashings of PBR rubber grease on the seals on assembley, The 'Brown Stuff' mentioned above is I reckon one of the many anti squeal products on the market designed to be put on the back of the pads to help diminish brake squeal. Since I've not had a bike with squealing brakes I imagine this is probably mainly a 'Car' thing.

 

One thing that is worth doing occasionally is using a TINY bit of lube on the bobbins that disc mounts to the spider on. DO NOTE THOUGH THAT I TAKE NO RESPONSIBILITY IF YOU OVER-LUBE YOUR BOBBINS AND END UP WITH LUBE ON THE DISC AN NON FUNCTIONING BRAKES. If you are so dim that you can't work out that adding a slipery thing to a braking surface is wrong then don't even f#cking attempt it, OK? Can I be any clearer than that?

 

Pete

[txrider]

Greg, Todd, Pete thanks for your input on this. And dlaing, the link you provided was informative.

 

Thanks all.

[todd haven]

txrider, stopped by the shop this am to pick up a few tools for a chore at home.

 

checked the tube of sil-glyde, and you are correct,

it is shown as suitable for o-ring, boots, etc.

 

I did not know this, we have always used the other stuff(from Raybestos, actually,

with the catchy title of Hydraulic Brake Cylinder Assembly Fluid) on the rubber bits.

Mainly because it works well for that task, so why change?

 

I don't think you have anything to worry with sil-glyde on the piston seals.

Dog knows we have no shortage of lawyers and lawsuits. If there were any risk,

it would be displayed across the package in inch-high letters.

 

Pete, is right, we use the sil-glyde mainly for cars with squeaky brakes,

usually little old lady in a V8 Mercedes with autobahn-grade brakes who

idles to the grocery store, to church, and then home.

 

Even with our hot, humid weather(25.5 inches of rain since Jan 1), we don't see much problem out of the

modern Brembos on Guzzis.

 

Pete, WTF is a bobbin? I'd hate to over-lube mine

[Guest ratchethack]

Pete, WTF is a bobbin? I'd hate to over-lube mine

My translation is that a "bobbin" as Pete's used the word here could be close to a "gubbins".

 

In American, I b'lieve Pete refers to the spring-washer loaded "buttons" that attach disk rotors to disk carriers on semi-floating brakes.

 

Per previous posts on this, without occasional lube, they've been known to seize up under certain conditions, causing pulsing brakes -- sometimes to the extent of being unserviceable.

 

But I'd have to refer to Blackie's "Down Under" Dictionary of Australian Slang to be sure, and my copy seems to've wandered off. . .

 

G'day, mate.

[badmotogoozer]

I've always heard them refered to as bobbins here in Canada too...

 

 

Rj

[todd haven]

Got it....

Bobbins and spiders =

buttons and carriers.

 

Shoulda known.

[mike wilson]

_As I understand it_ the way a hydraulic disc brake works is by distorting the seal under pressure, allowing the piston to move and push the pad against the disc. Removing the pressure allows the seal to relax to its normal square section, and pulling the pad away from the disk. The seal _must grip the pad_ in order for this to work. Therefore lubricants are undesireable on the piston. As the pad wears, the piston will slip through the seal microscopically to take up wear. If the piston is lubricated, it will slide though the seal and not be pulled back properly from the disc, causing premature wear of the pad.

 

I suspect, having been a copious lubricator of pistons for some years, that the seals are able to work as designed even when covered in slippery stuff. Certainly, until recently, the rust resistance of lubricated pistons was more desireable than any percieved disparity in pad wear.

 

I leave you with a snippet (from memory, so the wording may not be precise) from a 1927 Velocette owner's manual.

 

"If the brakes are too fierce, a light smear of grease may be applied to the linings."

[Dan M]

_As I understand it_ the way a hydraulic disc brake works is by distorting the seal under pressure, allowing the piston to move and push the pad against the disc. Removing the pressure allows the seal to relax to its normal square section, and pulling the pad away from the disk. The seal _must grip the pad_ in order for this to work. Therefore lubricants are undesireable on the piston. As the pad wears, the piston will slip through the seal microscopically to take up wear. If the piston is lubricated, it will slide though the seal and not be pulled back properly from the disc, causing premature wear of the pad.

 

I suspect, having been a copious lubricator of pistons for some years, that the seals are able to work as designed even when covered in slippery stuff. Certainly, until recently, the rust resistance of lubricated pistons was more desireable than any percieved disparity in pad wear.

 

I leave you with a snippet (from memory, so the wording may not be precise) from a 1927 Velocette owner's manual.

 

"If the brakes are too fierce, a light smear of grease may be applied to the linings."

 

 

Mike has it right about the whole flexing of the square-cut seal and self adjusting. The idea is to have a clean, dry caliper piston. If the dust boot around the piston is intact, you will have a clean, dry piston. No lubrication needed. If you feel the need to mess with it and damage the boot, you have to replace it. Adding lubricant will just attract dirt & brake dust causing things to get muddy pretty fast. Sylglide is an excellent product for caliper slides (Brembos have none:homer:) is can also be used sparingly on the edges of the pads where it contacts the caliper and on the back of the pads where they contact the pistons. The key here as Pete said earlier is don't use too much. More of a smear than a glob, DO NOT GET IT ON THE FACE OF THE PADS OR THE ROTOR. If you do clean it thoroughly with brake clean.

[Guest ratchethack]

Mike has it right about the whole flexing of the square-cut seal and self adjusting. The idea is to have a clean, dry caliper piston. If the dust boot around the piston is intact, you will have a clean, dry piston. No lubrication needed. If you feel the need to mess with it and damage the boot, you have to replace it. Adding lubricant will just attract dirt & brake dust causing things to get muddy pretty fast. Sylglide is an excellent product for caliper slides (Brembos have none:homer:) is can also be used sparingly on the edges of the pads where it contacts the caliper and on the back of the pads where they contact the pistons. The key here as Pete said earlier is don't use too much. More of a smear than a glob, DO NOT GET IT ON THE FACE OF THE PADS OR THE ROTOR. If you do clean it thoroughly with brake clean.

Dan, I appreciate your posts on brakes. It's kinda like being on an extended big game hunting trip with a gunsmith or a ballistics expert in the party -- you just can't beat professional specialty expertise if & when it's called for. . .

 

Though I will very sparingly use penetrating oil on disk brake "buttons" to keep them from freezing -- always carefully wiping up all excess -- I'm with Pete (per his previous post in this thread). I've always been leery of anything resembling grease or oil anywhere near pads and disks -- likewise brake shoes or drums back in the day. I'd no more put Sil-glyde or anything remotely like it on brake piston seals, let alone ends of pads or between pistons and pads, than I'd put wheel bearing grease on pad faces or disks. Knowing how hot brakes get, seems to me any lube anywhere near a hot spot stands a good chance of melting and running out into wotever it's close to, following the heat path as would be expected, and pads and rotor are just too close to where you don't want contamination by lubricants for my comfort. But that's just me. . .

 

I've also seen guys spray their disk brake calipers -- pads, disks, the whole thing -- with WD-40, as if it were the same as Brakleen. Someone on this Forum not long ago posted he does the same.

 

This may be perfectly fine in practice, but it just gives me the heebie-jeebies , and I wouldn't do it, knowing that WD-40 is essentially naptha-based cleaning solvent with a little penetrating oil additive. Seems to me this would ensure the brake pads would suffer contamination and performance loss from the oils driven into relatively porous pads by the solvent.

 

But that's mostly shade-tree speculation on my part. Any comment?