O-ring material for DOT-3 fluid

Just got a new Cleveland caliper assembly for one of our club's G-103's. Grob requires the use of DOT-3 fluid because of the master cylinder. The o-ring in the piston is designed for 5056 fluid. I'm told DOT-3 will call that o-ring to swell. So we need to replace the o-ring.

Does anyone know what common o-ring materials are compatable with DOT-3?

Aircraft Spruce, BTW, doesn't sell DOT-3 compatable o-rings.

Thanks,
Larry

Larry, I think what you need is Viton. McMaster-Carr (www.mcmaster.com) can set you up.

Thanks, Bob K.

On Tuesday, January 6, 2015 7:02:07 PM UTC-8, Larry Suter wrote:
Just got a new Cleveland caliper assembly for one of our club's G-103's. Grob requires the use of DOT-3 fluid because of the master cylinder. The o-ring in the piston is designed for 5056 fluid. I'm told DOT-3 will call that o-ring to swell. So we need to replace the o-ring.

Does anyone know what common o-ring materials are compatable with DOT-3?

Aircraft Spruce, BTW, doesn't sell DOT-3 compatable o-rings.

Thanks,
Larry

EPDM rubber is what you want for DOT 3 compatibility. Look at the following compatibility list, Dot 3 is under "Brake fluid DOT 3, glycol type". Viton is NOT recommended.

I have a whole bag of EPDM O-rings that are the correct size for the Cleveland 300 series brake calipers, as used in most GA Cleveland brakes with 5606 type mineral based fluid (and as used by Stemme GMBH w/DOT fluids) . . . send me a stamped self addressed envelope and I'll send you 4. No charge.

Or, you can order a new MKIV yaw string and I'l throw in the O-rings for free!

Also note that when using DOT-3 fluid it's important to make sure they pucks (pistons) in your caliper are anodized - otherwise they will tend to corrode if there's any water in the system (and sooner or later there will be, as DOT-3 is hygroscopic).

To check the pucks, use an ohmmeter or continuity tester. If the pucks are anodized, putting the probes on the surface will show and open, as the anodize layer is an insulator - bare aluminum conducts of course.

My understanding is that early Cleveland brakes were not anodized while those made in the last decade or so are anodized.

bumper
194 Taylor Creek Rd.
Gardnerville, NV 89460

Do not use this address for targeting purposes.

Ooops, left out the link in previous post:

http://www.marcorubber.com/compatibility.htm

On Tuesday, January 6, 2015 8:09:21 PM UTC-8, bumper wrote:

EPDM rubber is what you want for DOT 3 compatibility. Look at the following compatibility list, Dot 3 is under "Brake fluid DOT 3, glycol type". Viton is NOT recommended.

Thanks for clarifying! I thought Viton was the right stuff, but it looks like I was wrong about that.

Thanks, Bob K.

Nice to see this kind of help!

On Tuesday, January 6, 2015 11:09:21 PM UTC-5, bumper wrote:
EPDM rubber is what you want for DOT 3 compatibility. Look at the
following compatibility list, Dot 3 is under "Brake fluid DOT 3,
glycol type". Viton is NOT recommended.

I have a whole bag of EPDM O-rings that are the correct size for the
Cleveland 300 series brake calipers, as used in most GA Cleveland
brakes with 5606 type mineral based fluid (and as used by Stemme GMBH
w/DOT fluids) . . .

Also note that when using DOT-3 fluid it's important to make sure
they pucks (pistons) in your caliper are anodized - otherwise they
will tend to corrode if there's any water in the system (and sooner
or later there will be, as DOT-3 is hygroscopic).

To check the pucks, use an ohmmeter or continuity tester. If the
pucks are anodized, putting the probes on the surface will show
and open, as the anodize layer is an insulator - bare aluminum
conducts of course.

My understanding is that early Cleveland brakes were not anodized
while those made in the last decade or so are anodized.

Thanks Bumper!
Was there a change to the cylinder liner as well as the pistons?
If one finds an early corroded unit, what to do?
Just hone the cylinder?
Replace un-annodized pistons with new parts from Cleveland?
Thanks again for the education,
Best Regards, Dave

On Wednesday, January 7, 2015 8:45:53 AM UTC-8, Dave Nadler wrote:

Thanks Bumper!
Was there a change to the cylinder liner as well as the pistons?
If one finds an early corroded unit, what to do?
Just hone the cylinder?
Replace un-annodized pistons with new parts from Cleveland?
Thanks again for the education,
Best Regards, Dave

Not sure if Cleveland anodized the calipers, but I don't think so. The Corvette guys have been rebuilding the older car calipers due to corrosion with plain aluminum calipers. There's a cottage industry boring out the cylinders, then epoxying in a brass liner, which solves the problem completely. A company called Sierra Brass did the ones for my previous Stemme, around $70 a 14 years ago, I doubt they are still in business as the guy was getting up there (kinda like me now :c) and I couldn't find him w/ a quick search.

I anodized the pucks myself, as I have a small set up for making little aluminum parts pretty. Any anodize/plating shop should be able to do it for a few bucks.

This link will give you some leads on resleeving cylinders: http://forums.aaca.org/f120/resleevi...er-341332.html

bumper

I also anodized my Cleveland 30-9 brake caliper.
With mixed success.
See my project at
https://sites.google.com/site/threeu...-brake/caliper

Bumper, I think the guy you are referring to is Joe or Jack Way at Sierra Specialty Automotive in Quincy, Ca.
http://www.brakecylinder.com/contact.htm
indeed, he retired, as the webpage says.

I was in touch with him 3 years ago for a brass sleeve job on my caliper, but he indicated that he had stopped doing aviation stuff for liability reasons.
If I recall well, he had some sleeves pushed out.
(Learning: tell your shop it is for a cart or something like that)

My anodizing job (done at a local shop) was not as successful as I had hoped for. I think the problem was in the severe pitting.
The anodizing does not fill in the pitting.
As is visible in the images, both the caliper and the piston were pitted where the O-ring sits.
I tried to polish that out, but could not get in deep enough.
Now, in very hot weather (100 F) the caliper leaks a bit.
I thinks the DOT4 gets so thin that it creeps through the pitting past the O-ring.

My suggestion: If you are looking to anodize your brake system and your aluminum is corroded, take care of the pitting first before you do the anodizing.

3U

On Thursday, January 8, 2015 at 12:52:00 PM UTC-8, wrote:
I also anodized my Cleveland 30-9 brake caliper.
With mixed success.
See my project at
https://sites.google.com/site/threeu...-brake/caliper


3U,

Nice work!

For the pucks, simple to make new ones on a lathe.

I know one gentleman who filled the caliper bore pits with JB Weld, then sanded smooth. It worked, at least initially. I moved from that airport so don't know long term efficacy - I imagine little bits of JB Weld would come loose and fowl the works.

bumper