Triumph Rat Motorcycle Forums banner

Fitting new seals to my Lockhead caliper

6K views 15 replies 7 participants last post by  StuartMac 
#1 ·
Somehow I have a problem with installing new seals, really only dust covers in my Trident caliper.
The are simply little too big for a grooves there, or they are OK but I make some mistake installing them.
I got one side installed, but it'/s so tight I can't move a piston by hand, is it normal ?
I clean the grooves as well as possible and submerged them in brake fluid, still no cigar.
Any tips ?
The seals are from Walridge, but I believe they are all the same.
 
#3 ·
Using brake fluid makes the job much more difficult than it should be. Get yourself a tub of rubber grease, fit the seal and smear the seal and the caliper bore with rubber grease. Fit the dust cover top edge to the bottom of the piston, ease the the bottom lip into the recess of the caliper and push the piston down square. If it's even slightly to cock it will bind and make you think it's seizing.

Regards
Rod
 
#4 ·
Thanks Red, this is mostly what I did but without grease, just brake fluid.
Had a feeling it is not as slippery as it should be.
But finally piston being in caliper moved square and even.
From my experience working on japanese aluminum calipers they are much easier to rebuild and
not as tight as this, you can easily move a piston with your thumb - with Lockhead I used small vice.
Now wonder if pistons will be able to move back after pressure is gone.
 
#6 · (Edited)
As you apply pressure it pushes the piston out until the pad contacts the rotor and then starts to compress the seal before finally applying the most pressure to the piston and pad. It's this compression of the seal that brings the piston back after releasing pressure. If your piston moves out under pressure it should retract no matter how tight they are. I ran the brake caliper department of Rebco Racing Enterprises back in the mid 90's. When racers complained about brake drag from getting hot, we would replace the "square" o-ring with a round one that retracted more than the square ones elevating the issue.
I never used anything but brake fluid for assembly. If they are tighter than you think they should be pull the o-ring seals and make sure there is no corrosion build up in the seal grooves, use a pick to make sure they are clean before installing the seals.
 
#5 ·
I have been advised by the people who make our caliper and master cylinder kits in the UK to never use anything but brake fluid to lubricate the seals during installation, and to use ONLY Dot 3,4 or 5.1 brake fluid.

Now especially for the rear caliper I pre-bleed each side by pouring about 1/4 to 5/16" of brake fluid in each half before offering the piston. Lockheed has never recommended that Dot 5 be used in there brake systems.
 
#9 ·
You could go on for hours on just this subject. We buy our hoses and rebuild kits from Nelson-Stokes. Their standard kits are designed to be used with Dot 3,4 and 5.1 glycol based brake fluid. This information is on their web site. They do, at special request, make kits suitable to be used with silicone based brake fluids. I don't know of anyone in the British motorcycle business who offers NS, or any other manufacturer's, silicone master cylinder or caliper kits.

Both NS and AP Racing will give a warning about using anything other than Dot 3, 4 or 5.1 to lubricate the rubber during assembly. The current offering from AP Racing includes the following note:
"Important servicing note:
AP Racing products designed for brake fluid and fitted with rubber seals must be cleaned in soapy water or an alcohol based cleaning fluid e.g. Methylated Spirits.
DO NOT USE PETROL, GASOLINE OR MINERAL OIL BASED CLEANING/LUBRICATING AS THESE WILL DAMAGE THE SEALS."

The answer to your question about not using an petroleum based cleaner/lubricant (ed. like in grease) is it can damage the seals! They do make glycol based rubber grease used for lubricating automotive caliper pins that either ride in rubber bushings and/or have rubber boots covering them. I have not seen one of these greases recommended for lubrication the caliper seals. Do you know of a brand that specifically recommends there use for lubricating caliper or master cylinder seals during rebuilding?

Remember the word "grease" has become generalized. It covers a range of products made from differing compounds. All someone rebuilding their caliper sees I use grease to lubricate the pistons during a rebuild and he pick ups the first one he comes across.

If you check AP RACING's current web site under brake fluids they say highlighted in red in RED "AP RACING does not sell and do not recommend using a silicone based brake fluid in any of their products.

Now Stuart will be all over me for this post!! Fair enough, but what you find where one person has had good luck with using a particular brand of a silicone based product/seal kit, your experience may differ. The one thing that seems universal is a change from glycol to silicone brake fluid should come with a complete rebuild of the brake system - including all hoses and seals. This includes a complete flushing of all metal piping. The only area where silicone brake fluid shines is not damaging paint if some fluid is spilled on it. It has more performance draw backs which is why it is never used in racing applications.

I expect pages of rebuttal from Stuart...
 
#12 ·
AP Racing products designed for brake fluid and fitted with rubber seals must be cleaned in soapy water or an alcohol based cleaning fluid e.g. Methylated Spirits.

The answer to your question about not using an petroleum based cleaner/lubricant (ed. like in grease) is it can damage the seals!
This can never be under emphasized John.

Not only avoiding grease as a lubricant, but special attention to cleaning parts which had been subjected to petroleum solutions during the servicing process.


I'm personally not averse to using "Rubber Lubricant" which is a non petroleum based product.

Maybe when original instructions went out rubber lubricants were either not about or not well known?

http://www.penriteoil.com.au/products.php?id_categ=14&id_products=105
 
#10 · (Edited)
I'll just get in before Stuart. I never recommended using a petroleum based product to lube the seals. I said to use rubber grease, rubber grease is a specific product made from vegetable oil that is designed for use in hydraulic systems. It is compatible with both natural and synthetic rubber.

Both Castrol and Penrite recommend there rubber grease for the assembly of hydraulic brake and clutch components.

Rod
 
#11 ·
But from 50 years of experience giving advice to customers and dealers is a lot of them only see "grease." They either don't read what you write or don't see it because of dyslexia or some other other reading impairment. It seems a lot of mechanics found that the "educators" shooed them off to technical/trade school thinking they were not that bright. Often it was just the opposite...

I, for example, learn visually. If I did it, or saw someone else do it, I owned it. Then reading the manual made some sense. But just given the manual I was lost. I find a lot of my dealers have the same dysfunction. It wasn't until I was fifty, and a friend who understood my problem, helped me to read so that I could comprehend what I am reading.

Still today, my eyes glaze over trying to follow Stuart. By the time he makes his point I have moved on. But I understand that most of the population are like Stuart. It is just that I have been around more people like myself in this business.
 
#13 · (Edited)
I, for example, learn visually. If I did it, or saw someone else do it, I owned it. Then reading the manual made some sense. But just given the manual I was lost. I find a lot of my dealers have the same dysfunction. It wasn't until I was fifty, and a friend who understood my problem, helped me to read so that I could comprehend what I am reading.
Your situation is pretty normal John.

Some learn purely by verbal or written instruction.

Others need to combine this visually, by observation.

Yet others need to follow up verbal instruction & observation, by actually performing the work.


I personally can be at sea with written instruction alone.
The writer often assumes the reader already possesses related knowledge, or may write in a way which can be interpreted to mean several things.

Listening/Reading, followed by observation, then execution is the best form of learning.
That's why snaps and vids are invaluable with forum instructions.

A big downside of novice restorers is that expensive parts can be buggered up without first experiencing observation.


In restoration experience is King.


Take an engine re build for example.
Given minimal competency, apart from specialized tools, experience is the difference between a specialist engine re builder and a novice.

I wish I could download into my brain the experience amassed by Dudes such as Grand Pauly, Don, Stu, & yourself, just to name a few.
 
#14 ·
So reading back through. Brake fluid is a perfectly suitable lubricant for assembling the caliper, so long as it meets the specifications required. Alternatively, if you want to make the job easier (try it, it will change your life) you can use Rubber Grease (not ordinary petroleum based grease).

I'm also a touch confused as to the description offered as to how the seal operates. Perhaps I misunderstand but the square section seal is not compressed during operation. As the piston is forced out under pressure friction against the seal causes it to distort (it twists). Once the hydraulic pressure is removed the seal returns to it natural shape and the same friction retracts the piston enough to free the brake. I am not convinced that suggesting someone messes with this fundamental part of brake design by replacing the square seal with an O ring is really a great idea?

Regards
Rod
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top