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Triumph TR6 - Brake Caliper Circumferentiality

Finally got the pistons out of the brake calipers (took over 100 PSI compressed air) but as I decided to Powder Coat the caliper I reinserted the piston in the cylinder to protect the interior from the powder. I had already removed the rubber seal and cleaned up the cylinder somewhat. What a surprise when I discovered that the piston did not smmothly slide into the now polished cylinder, but did so only when I rotated it about 60 degrees or so. That suggested to me that either the cylinder or the piston have gone out of round. If indeed this is the case must I now purchase new calipers (to go with my new stainless steel pistons) or visit my local machine shop or just ignore the issue?

I would have thought that the piston would fit rather loosely in the cylinder since the seal is the rubber ring around the inside of the cylinder. I cannot determine by eyeball if circumferentiality has been compromised, but it sure seems to be so. I would not want to expect a hard stop to discover in the failure analysis later that the piston stuck and caused the brakes to fail.

Comments?
db
Doug Baker

Hi Doug
I find it hard to imagine the caliper has actually gone out of round. even if when cleaned and polished they went out of round ,they would have gone out of round on the big size ( the piston would have even been more "sloppy" in the hole).
But then a vernier will measure this.
Rick
Rick Crawford

Did you try both pistons in the caliper Maybe a little PC inside. I don't think it would matter with the 60'. Both would have to be out the exact same. I think something screwy here!!
DON KELLY

Doug--Did you split the caliper before you put it in the powder oven?
Rick Orthen

Rick Orthen,
Excellent question. I too pondered how I was going to protect the mating surfaces from powder etc. I DID separate the calipers. Took a BF wrench and then a cheater bar, but unscrew they did...finally. Had to get the "O" ring out before putting into the oven, but then I've been advised that the calipers probably see hotter temperatures in use than the 350-400 degrees I'll subject them to in the oven. Nonetheless, after some thought and reading/re-reading Nidel's articles, I think that I'll reassemble the halves for the powder coating exercise. With the bolts tightened down if not torqued to spec to make sure the threads, bolt holes, etc remain clear of powder. Nidel advised just masking the mating surfaces to protect them, but I think all would be better to avoid as much masking as possible. I do have fiberglass tape to help mask the cylinders with the old pistons in. If this experiment does not work, I'll be out a couple of calipers. I'll advise success/failure in a couple of weeks, maybe some photos too. Still pondering the piston interference issue right now. Would like to resolve that before I undertake PC'ing these suckers.

Don, you're right...sum'en's screwy here.
db
Doug Baker

Very good. Let us know what you torque the halves to when you reassemble them for use. I've never seen that spec.
Rick Orthen

Rick O-According to Nelson Riedel's tech article on brakes, (which he disavows) he recommends 40 ft. lbs. for the outer 3/8" bolts and 70 ft. lbs. for the 7/16" inner bolts.
Berry Price
BTP Price

Berry, Rick,
Roger on the torque specs, but I assure you that it took a hellvu lot more than those values to break the bolts loose.
db
Doug Baker

OK folks. Think that I got it figured out. My S-I-L came by last night and we pondered the "tight" fit. His observation was that we were canting the piston vertically in the cylinder and that's what was binding. I checked the circumferentiality as best as I could with a caliper guage (ironic huh?) and while there was some slight variation, could not detect a true out of round condition on either the cylinder or the pistons. So I'm going to proceed with the plan to polish the cylinders, bead blast the exterior and powder coat these suckers, put the new parts in and get 'em off my work bench. Happy holidays to all.
db
Doug Baker

S-I-L ???
DON KELLY

My guess is Doug's daughter's husband???
Rod Nichols

Don, that'd be my daughter's husband...Son-In-Law...!! He's a bit more inclined to putter with me in the shop than are the females in my family:)
db
db
Doug Baker

Doug, you say your going to polish the cylinders, if you mean clean the gunk off the chromed surface, great.
If however that chrome coating has been chipped or worn off you must get new cylinders. Stainless steel is the way go, they never corode and are available for our calipers.
Chris
Christopher Trace

Dougs got a daughter?
DON KELLY

Chris....
Check back to the first post....new stainless pistons. Doug, when I cleaned mine up, the pistons slipped in & out very nicely. (There's one Don Kelly will have his way with) are you fitting the old pistons, just to do the powdercoat, or is this with the new ones?
Rod
Rod Nichols

I concur with SIL, think you may have canted the pistons a bit, and turning them straightened them out some. Instead of turning them, you could just wiggle a bit next time to confirm the theory.
Tom

Rod, I'm only using the old piston as place holders to protect the cylinders while I powder coat the exterior of the caliper bodies. I MAY abort and go to masking if it appears that the powder will get by the pistons. I don't want to get powder in the cylinders and since I'll have the dust covers removed, masking may be the best alternate. All holes will be plugged with silicone plugs or bolts including the bleed screw. I have new ones of those. Broke one getting the caliper off the car. I hope to finish this task in the next few days and I'll try to post some photos for those interested.
db
Doug Baker

Doug, Rod,
sorry, that is what happens when you get old.
Chris
Christopher Trace

For anyone who may be interested, I send Charlie some photographs of the Powder Coated Calipers. I used Eastwood Argent Silver which cured to an almost chrome finish. I was quite pleased with the outcome. I reassembled the "halves" to avoid contamination on the machined surfaces. Cured at about 350o for 20-25 minutes.
db
Doug Baker

Rick, I guess we're not on Doug's mailing list anymore.
DON KELLY

If you are talkin'bout this Rick, well I get Doug's other questions:) Gotta say, Doug is really doing this right and is going to end up with a first place car.

Charlie, going to flickr them...would love to see them.
Rick
Rick Crawford

Pix of Doug's calipers are now posted..very shiny !! look great !

Charlie

http://www.flickr.com/photos/tuxedotwo/sets/72157594457846205/
Charlie B.

Here's what I get when I go to that link


This page is private.

Oops! You don't have permission to view this page.

Here's a link back to your home page.
DON KELLY

Thanks Don...a minor glitch now fixed
thx
Charlie

this works

http://www.flickr.com/gp/15689640@N00/23oDaZ
Charlie B.

Absolutely beautiful Doug. I think I will pull mine off and send them down to you.

Any concern about getting paint on the 2 mating surfaces or are they "clean"?

PS the first link works just as well as the second. Don's problem is because he is from home town of Bill.
Rick
Rick Crawford

Rick,
I'll be happy to do yours...just take the damn pistons out first!! No, no issue with contamination on the machined surfaces if you reassemble the "halves" and tighten down well. Note the small "o" ring that seals the channel between the halves. I removed that before firing. Had to spend considerable time with polishing compound and a buffing wheel on my dremel to clean up the residual corrosion and "smooth" the cylinders. As you can see they're still not "mirror" smooth, but they are clean as are the channels, so they'll do. Thanks for the note on fluid.

Don, you're still on every list I know about!! BTW, how's the wiring coming. I've ordered my set from Dan. Expect to get started on that in early spring.
db
Doug Baker

Doug- After you do yours come and do mine!
DON KELLY

BILL???
DON KELLY

As in Gates
Rick Crawford

Don,
It'd probably be easier and certainly cheaper for you to send yours to me rather than me coming to you, but what the hell, I haven't been in Seattle for several years so send me a plane ticket. Oh, and an extra aircraft to haul all the stuff...:)
db
Doug Baker

That's just Mr. Gates
DON KELLY

Doug, those look sweet! For years I've heard that you should NEVER take apart the halves of a brake caliper,
but it looks very simple. Is it just those little sealing washers that constitute all the warnings?
Nice job,
Chris
Christopher Trace

Doug
I have been told the same...do not take apart.

Now you need to do the same to the intake manifold, thermostat housing, fuel pump cap, and the dip stick. I wounder what the carbs would look like?
Rick
Rick Crawford

Rick,
I'm on my way...!! This Argent Silver stuff is pretty neat. Comes out looking almost like chrome. I've been toying with doing the carb bodies. May try it. I'll let you know.

Chris, the "O" ring which is not really a ring and not really an "O", rather flat and fits in rather oblong instead of round. But yep, that's what seals the channel for the fluid to go from one side of the piston where the inlet hose is to the outside "side" which has no open access. I think that admonition about never separating the halves is because of the very real possibility of not getting a good seal again and having a leaky caliper. You might induce an anomoloy to the mating machined surfaces; you might not get the torque back just right; you might get contamination on one half or the other...you might a lot of things, but it is separable and I figured what the hell, if Nelson Ridel can do it why can not I? I'm only out an overhaul kit and a new set of calipers if I fail, so I decided to go for it. I'll let y'all know if I have a leak when I get them back together on the car. Rick Crawford has about convinced me that Silicone Brake Fluid is the only option and since I have new or rebuilt the entire braking system, I'm offered the option of DOT 4 or 5 (Silicone). I'm leaning to Silicone, but could be convinced otherwise if anyone has a good argument against it. In any event, I should know if the brakes are gonna be OK by late Spring or early Summer.

BTW, PC'ed the brake box and all components a gloss black so even if I suffer a leak and have DOT 4 I'm not going to have the "paint" come off!! Booster was overhauled and is also PC'ed gloss black, The brake and clutch master cylinders are painted with POR-15 Silver. SS hoses, connections and lines throughout.

Thanks for all the interest and comments. This thread has run a lot longer than ever expected.
db
Doug Baker

Doug
The only time you would use DOT 4 is if you plan to race/rally your car.

I think the carbs would look cool in the silver.
Rick
Rick Crawford

Doug, I've had Silicone Dot 5 fulid in my clutch and brake system for about 5 years now. No problems of any kind. I've even been out on the track a couple of times and didn't experience the spongy brake pedal you hear about.
Chris
Christopher Trace

Rick,
I guess that I don't understand...why would DOT 4 be more or less advantageous if one raced/rallied their -6? I'm hoping for power in the range of 150 HP when I'm finished with this sucker. Would that drive the decision to DOT 4 and if so, why? I'm obviously missing something here!!
db
Doug Baker

Doug
Sorry...should have elaborated.
Chris answered your question. After considerable use of the brakes, (race or rally) DOT 5 brakes would be a little spongy.....the nature of the beast. Also, as you know, DOT 5 is a LOT more expensive so no point using more expensive stuff when you could be draining the fluid after each race.
The big advantage (for us) is that 5 is considerably less hygroscopic than 4 which makes it ideal for longer drain periods and for us winter guys ideal for extended non use of vehicle periods. More specifically for the winter thing is: change of temperature equals condensation equals water equals rust.
Rick
Rick Crawford

So Rick, how often do you have to change the DOT 5? Some advice I've seen recommneds a complete fluid change of DOT 4 about once a year!! Seems way excessive to me, but then what do I know??
db
Doug Baker

I put in silicone fluid in 1990 when I finished the restoration of my TR3A. All the brake and clutch rubber was new. Since then (94,000 miles) I have changed the silicone fluid twice. Another big advantage of silicone fluid is that it lubricates the pistons and cylinders of the front calipers and rear brakes. This makes them operate without any problems even after winter storage. I store mine every winter for 5 months and never had a problem with the brakes or cylinders jamming up. Also because silicone does not absorb water, there is no water to rust the pistons etc. I re-used my original caliper pistons in 1990 after smoothing out the rusty spots on the outside diameter and they are still free. They now have over 174,000 miles on them with one change of the rubber seals in 1990.

Don Elliott, Original Owner, 1958 TR3A

http://www.triumphest2006.com/images/clubcars/30donelliott'str3.jpg
Don Elliott

Well if that does not convince you Doug....
Hi Don..happy new year to you.
The reason for the recommended frequent DOT4 change is because it is hygroscopic. In reality I think every second year is OK with .4 especially if using CASTROL LMA.

Maybe it is time for me to do a change. My DOT 5 has been in both hydraulic systems since the restore back in 2001.......6 years. Not as long as Don though. So maybe in another year or 2:)

Rick
Rick Crawford

And when you drain all the silicone fluid, let it sit in a glass jar for about a month and it will be like new again. In the TR3A, it turns black with time in use whereas in a TR6, I have heard the purple colour becomes clear. After a month all the black in my case has settled to the bottom of the jar and I can re-use the purple fliud at the top. The reservoir on the TR3A is a closed can and it may be that the translucent plastic on the TR6 fluid reservoir lets the sunlight change the colour from purple to clear.
Don Elliott

Hey Don, what do you think the black stuff is? Probably aluminum oxide and/or rubber worn off of the seals, I guess. Have you ever rubbed a bit of it between your fingers? Just curious.
Tom

Hi All,
As the moisture absorbs into the brake fluid it gravitates to the lowest point in the system... usually the front calipers, and creates at least two problems:

1. that of corrosion hampering the smooth motion (particularly retraction) of the pistons in the calipers creating brake drag and undue heating.
2. the boiling point of the fluid is reduced causing poor braking, spungieness, brake pulsing as it boils the compressed fluid.

I think that like most fluid changes it is about the cheapest mechanical investment in time and money possible. Drain your system and flush it biannually if using DOT 3 or 4. For those of us with an garaged season, I wonder if sealing of the master cylinders ( both brake and clutch) would be a good idea as brake fluid readily absorbs moisture from the surrounding air... all winter long! Has anyone tried a tight fitting piece of poly under the caps to prevent H2O infiltration?


My 2 cents,

Rob
Rob Gibbs

Doug
Rob tells you why you had a problem getting your pistons out. Are you convinced yet to go DOT 5?

Rob
Good point on the 2 reservoirs. Both have vent holes in the lids. Possibly best solution to prevent moisture in the 2 reservoirs is to have them full to the top at storage time....kinda like the gas tank. Adding some "food storage wrap" across the mouth then screw lid on might act like a vapour barrier.
Rick
Rick Crawford

Rick, yeah, y'all have 'bout convinced me that the silicone will serve my purposes a bit better than the traditional stuff.

On a different note, I've had a hellava time finding Red Rubber Grease. The Castrol website lists it, but I've not found a distributor in CONUS which still carries it. Kai Radicke at Wishbone allowed as how he was hoarding his deminishing supply and that a clear substitute had been marketed but he had not tried it. I did find and order some from a UK company. Now remains to be seen if indeed they will fill the order. They also had a tub of copper antiseize for a nominal price.
db
Doug Baker

GEEEES Doug....do I need to come down there and twist your arm?
Rick Crawford

Come on down Rick. We can twist the tops off some bubbly pop or pull the cork on some Single Malt:) Obviously I need all the help I can get.
db
Doug Baker

Doug, I have a sealed packet of that red rubber grease from Lucas sitting on the self It's yours if you want it, I can throw it in the mail.
Chris
Christopher Trace

Chris, You have mail:)
db
Doug Baker

Doug, we are right in the middle of changing from 26.4kb per sec. dial up email to 1MB per sec. 2 way satelite Ka band email and I think both are still working but here is the new sat. email address in code...
catraceATxplornetDOTcom
Christopher Trace

This thread was discussed between 18/12/2006 and 11/01/2007

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