split calipers - seals - Warren?

[KobaltBlau]

edit: First a disclaimer: Any action you take based on information from this thread is your sole responsibility. No person providing information on this thread shall be held liable for your actions based on their information. Brakes are a life or death matter, and if you choose to work on them, you take this responsibility. If you have any doubt, have the work done by a qualified professional

Hello Pelicanites,

I recently bought some wide ‘A’ calipers off of a carrera 3.2. When they arrived, they were “split,” meaning that the two halves of each caliper were apart. In fact, they were bolted together loosely, with the spacers that go between the two halves floating in between on the through-bolts. The necessary seals for the center of the caliper (one on each side of each spacer, four total per caliper) were missing. I did not think to ask the seller if the calipers were split (I assumed they were not), and neither did the seller tell me.

So I now have 2 unforeseen problems:

1. I need a total of 8 (identical) seals to be able to put these calipers back together.

2. I need to be able to tighten the through bolts, which have an odd bolt head (not torx, but similar)

Pelican does not seem to have either the seals or the necessary tool (more on the tool later), I have called them and looked at the website.

As for number 1, I have searched the archives and come up with some good info from Warren:

Originally posted by Early_S_Man
Splitting the Ate caliper halves is no big deal ... except for the fasteners used and obtaining the proper Ate replacement seals. The procedure used to be included as a routine item in the brake section of the air-cooled VW Bentley manuals, and also is in the Clymer 912 book. The bolts are often rather rare and odd, such as 'RIBE' spline, and will be mangled or destroyed if XZN or Torx bits are used in the attempt to loosen them! The proper Ate rectangular cross-section seals used to be sold at VW and Mercedes dealers, and the Porsche part for 'M' calipers is 901.351.928.10 (same as VW pn 311.615.277) ... though I can't seem to find the part number for the 'A' calipers, and there may be a problem getting the 'M' caliper replacement part, too at dealers! Stoddard still lists it at $1.28, though. Silicone grease, which VW and Ate call 'brake paste,' should be used on ALL of the rubber seals when reassembling calipers! A very tiny 1 gm tube of unlabeled silicone grease with the same color & consistency as Dow Corning 4 or 4X ... used to be included in the Ate rebuild kit for 911 master cylinders!

Stoddard does indeed still list that part, although the price has gone up to $2.28. The question is whether the ‘M’ caliper seals are the same as those for the wide ‘A’ caliper from the Carrera 3.2. Warren said this in response to an SC owner (Olivier) with a similar problem to mine:

Originally posted by Early_S_Man

None of the regular factory Ate, or Raybestos-Ate rebuild kits come with those rectangular cross-section sealing rings that go between the cast-iron caliper halves!

You can, however, use VW 311.615.277 part which comes from Ate as well. It is identical to what came out of my 'M' calipers, and is OEM part for the 'L' calipers on '66 VW Type 3s.

Does this mean that the M and wide A calipers really use the same seals between the halves? I think this is what Warren meant, but I'm looking for confirmation...

On number 2, Warren referred to the necessary tool as a “Ribe” drive bit. He said that a Torx bit can strip this fastener, and indeed, looking at the head, it is not a Torx, although similar. Pelican has a tool for 914 cv-joints, an 8mm, picture here: 914 CV Tool

The size seems plausible, but I am not certain whether this is a Torx or a “Ribe”, or sure it is even the right size. Anyone know of a source for the correct tool?

I am tempted to use some high quality standard hex-head or socket-head bolts to replace the stock through bolts instead of buying a $28 tool that may not work and even if it does I will probably never use it again. Anyone done this? The only drawback I can think of is wheel clearance, I’m not sure whether that would be an issue or not.

Also, does anyone think that the dow corning 4 or 4x silicone grease is better than the permatex brake caliper lube?

Thanks in advance!

[jpnovak]

M and A caliper seals will not be interchangable. They are physically different sizes.

[KobaltBlau]

Thanks for the response, Jamie. Just to clarify:

Are you referring specifically to the seals between the caliper halves, that normally don't get disturbed in a caliper rebuild? I realize that the piston and dust seals will not be compatible between A and M, but that is not a problem.

[jpnovak]

I assume the seals are will be a flat square cut seal that is the same dimension as the mating surface of the caliper halves. This would be like a valve cover gasket that fits between two mating surfaces. Since I have never split a caliper for these exact reasons I assume they are not just an o-ring seal at the fluid passageways.

The A calipers are about 2 inches longer than an M caliper. They are just different in size beyond the piston bore, mounting flange, and pad dimensions.

Maybe you could put them together with that orange locktite stuff or some other sealant. It works at the case halves!

[KobaltBlau]

Originally posted by jpnovak
I assume the seals are will be a flat square cut seal that is the same dimension as the mating surface of the caliper halves.

No, they are not. I probably should have mentioned this. They are similar to an o-ring seal right around the fluid passages, but the seal rings themselves have a rectangular cross-section, as opposed to the round cross section an o-ring has. They are also made of an appropriate material to come in contact with brake fluid; I have no idea whether standard hardware store o-rings are and whether they would leak. Frankly I would rather get the proper seals. Alas, I would never have split the calipers either, but the person I bought them from sold them to me without telling me that they were split.

soooo, my questions still stand! Thanks!

[jpnovak]

I see, Why don't you measure the ID and OD of the recess for the seal and see if it matches those of the rear M based calipers. I have some old M calipers and are willing to split but I don't have the right tool.

[KobaltBlau]

Good idea. I could measure the recesses on my calipers and post that information, and maybe someone who already has M calipers apart could do the same.

But the easiest would probably be if someone, perhaps Warren, has done this job on 'A' calipers and knows what seal to use.

Thanks, Jamie.

[jstgermaine]

Andy,

I have several sets of 'M' calipers I am currently rebuilding. I will measure the o-ring seals and post tomorrow.

[KobaltBlau]

Thanks for the help, Jerry. I have made a bunch of measurements and taken photos, and I will post all of it tonight.

[KobaltBlau]

OK, first for some background:

Here is how my calipers arrived, split (argh):



you can see the spacers floating on the through-bolts.

here's the outside, for reference:



the inside:



opened up, spacers are on the right half, with 2 through bolts just holding them in place (below). You can see the recess for the seal on the left half, notice that the spacer does not have a seal recess on this side. It does, however, have one on the other side, and the other half of the caliper does not. In other words, each joint has the seal groove on the wheel side of the joint.



here is a closeup of the recessed area on the outer part of the caliper:



here is a closeup of the recessed area on the spacer, that holds the seal against a non-recessed area on the inner (relative to the car) part of the caliper:



My measurements, all in mm:

A 10.95-11.05
B 6.15-6.35
C 10.95-11.15
D 6.35-6.40

edit: please note I posted measurements for the depth of the recesses in my next post below

So basically the seal we are looking for should be a little less than 11mm diameter, with a hole a little more than 6.35mm in the center. Note that I don't have any of these seals, even tired old ones.

Here's the funny bolt head, probably Ribe based on Warren's posts, definitely not Torx!



I'm still thinking I will replace these with grade 8 socket head cap screws (that you use an allen bit in). Especially now that I have noticed that a couple of the through bolts are a bit rusty and may not be completely straight. Although the head face pressing on the caliper will likely be a little smaller diameter, I am not too worried about this since the calipers are iron. I could even use a washer (gasp). Does anyone know the torque spec for these through bolts? My Bentley manual doesn't list it since you're not supposed to take the halves apart.

So if anyone could measure those inner and outer diameters on an M caliper, or give me an opinion on my through-bolt replacement, I'd be grateful!

Thanks, All!

[Eugene at Pelican Parts]

I had some A calipers apart a few months ago. I recall the through-bolts to be fine-threaded, and the nut to be extra 'thick'. They seemed to be a pretty high grade steel. You know... by smell. I actually used a Torx bit and it worked fine. I also didn't care if I broke anything.

I also recall the hole in the little seals to be smaller than the inner diameter of the passage. ID of 6mm should be fine, and not too critical. However, a more important measurement to concern yourself with is the thickness of the seal. Obviously too thin is rather useless, and too thick might also obstruct the caliper halves from sealing correctly. Anyway, that's just what I recall.

[KobaltBlau]

Originally posted by Eugene at Pelican Parts
I had some A calipers apart a few months ago. I recall the through-bolts to be fine-threaded, and the nut to be extra 'thick'. They seemed to be a pretty high grade steel. You know... by smell. I actually used a Torx bit and it worked fine. I also didn't care if I broke anything.

I also recall the hole in the little seals to be smaller than the inner diameter of the passage. ID of 6mm should be fine, and not too critical. However, a more important measurement to concern yourself with is the thickness of the seal. Obviously too thin is rather useless, and too thick might also obstruct the caliper halves from sealing correctly. Anyway, that's just what I recall.

Thanks for your input, Eugene. Um, yeah, that _IS_ an important dimension! Here's my measurement for the depth of the recess that carries the seal:

Spacer recess: 1.46 mm deep
Caliper recess: 1.55 mm deep

These should, of course, be about the same, since I believe they are made to carry the same seal. The variation is primarily due to differences in machining, I believe I was able to minimize measurement error using my micrometer. In any case, the depth is roughly 1.5mm.

However, my primary goal here is not to make a seal that will work; I want to know whether 'M' and 'A' split seals are compatible so that I can try to use Warren's VW part number. If that fails, I may be trying to make something as a last resort. Frankly, I'd like to avoid assembling calipers and having them leak, taking them apart, putting back together, yadda yadda yadda...

Thanks again, everybody.

[Bill Verburg]

The only available caliper half seals are the 901.351.928.10 ~$1.28 last I looked


I believe that the seals are all the same, but could easily be wrong

The bolts are the obsolete Ribes

Note, ATE does not supply either the caliper half seals or the through bolts as replacement parts

[KobaltBlau]

Thanks, Bill. Any opinion on replacing the bolts (some of which really need repacement)?

Much Appreciated,

[Bill Verburg]

By all means replace them

My personal choice would be to use some unmolested calipers

[smdubovsky]

FWIW, the new "torx plus" bolts look alot like those "ribe" bolts. You might be able to find a bit that fits them (Im sure you can find the dimensions of the torx+ system on the web and see before you go buy one).

http://www.textronfasteningsystems.com/products/torxplus/index.html

SMD

[KobaltBlau]

SMD, thanks for the tip on the torx plus!

Originally posted by Bill Verburg
My personal choice would be to use some unmolested calipers

Yes, this would be my preferred choice as well. However, I just paid ~$150 shipped for these plus some used rotors, and I sure hope that wasn’t totally wasted.

I questioned the seller about the condition of the items, but I never thought to ask whether the calipers had been split, since hardly anyone does this. The seller did not mention anything about this. Do you guys think I should go after the seller? He does post on Pelican. Shipping back to him is about $17 for the 45lb package. I could get fasteners and seals for this, most likely.

I guess I need to bolt the two halves back together and blow the pistons out to make sure the bores are clean, and the calipers are otherwise good. hopefully the caliper will seal well enough to do this without the proper ribe bit or seals. I could probably even clamp them together, minus the spacer. If the calipers have other problems, it's not worth re-sealing the split and I should just go after the seller for selling me junk.

Thanks Much,

[vash]

get your money back! i think he should have mentioned that the calipers were split.

[KobaltBlau]

I have an inquiry in, we'll see what I get back. We'll see if i have time to @%*& around with this before the next driving event; my SC rotors are at their wear limit.

[Early_S_Man]

Kobalt,

Based on the dimensions of the recesses posted ... the 'M' caliper seals won't work.

My suspicion is that the front caliper seals for a '70s Mercedes 450 series car would work. Their front calipers are cast iron Ate 'SS' calipers with a 60 mm bore, and the seal was significantly larger than the 'L' or 'M' seals -- the VW part I posted the number for in an earlier thread.

I will dig out a ruined 'SS' caliper I had to replace [saved in the garage] and measure the seal recess dimensions, and post them this weekend.

I believe replacing the Ribe fasteners with DIN 12.9 Allen bolts would be a good idea ... luckily you don't have to extract the bolts, or worry about finding the correct Ribe drive bit! Metric & Multistandard used to carry them.