Banjo Bolt Bleeders on Seville Calipers

[pmbrunelle]

Banjo bolt bleeders seem common in the motorcycle world.

Banjo bolt + bleeder =

JDA-458073-2.jpg (38.16 KiB) Viewed 3230 times

These seem to be available in M10x1.0 and M10x1.25 threads (common in motorcycles).

I have looked for M10x1.5 (i.e. GM) banjo bolt bleeders, and they are unobtainium.

RaceTech Titanium makes a banjo bolt bleeder that's almost close enough:
https://racetechtitanium.com/product/ti ... eder-bolt/

I asked them about a custom M10x1.5x23 banjo bolt bleeder, and I was given this preliminary pricing:
4 pcs -> 125 USD /each
10 pcs -> 75 USD /each
20 pcs -> 40 USD /each

I would like four banjos (2 on my Fiero, 2 spares), so I find the price a bit expensive if I just get them for myself.

I was wondering if anyone else would want to hop in on this party.

Perhaps you have a brake caliper installed upside-down like I'm planning on doing:

Seville Caliper.jpg (169.03 KiB) Viewed 3230 times

In this install, the brake cable passes below the CV joint, the banjo bolt is at the top, and the bleeder is at the bottom. So air bubbles cannot escape via the bleeder.

A banjo bolt bleeder could be used to remedy this situation.

I have a plan B to convert my calipers to M10x1.0, but I'd rather not do that.

[pmbrunelle]

Doesn't seem too popular, not that I was expecting this idea to be...

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So this is on my Zettner-style brake setup, and more specifically I have Kohburn-style 10° rotated brackets in the rear.

Finally the banjo hole isn't at the highest point of the caliper, so air could remain trapped in the bore.

Seville Caliper.JPG (635.93 KiB) Viewed 3179 times

I think this problem can be solved by cutting an inverted trench running from the high point to the banjo hole, but since I will have crossed the bridge of modifying the calipers, I might as well Heli-Coil them for M10x1.0 off-the-shelf banjo bolts.

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I guess I have an ultimate objective of making the drum-in-hat work, so I can lose the Seville calipers, but that's for later.

I do not attempt to meet all objectives on the wishlist of a project in the first go; I seek to satisfy many objectives, and get something working on the car.

Like this I take bite-sized chunks of work, and I can test and get feedback on the rest of the system; feedback which could be useful for the next iteration.

Also I like to be able to use the car as a DD, sometimes.

[The Dark Side of Will]

Sounds like a great idea... But limited applicability. The upside down Seville calipers being the only app I know of, although it would be interesting to understand what the apps for 10x1.0 and 10x1.25 sizes are.

[pmbrunelle]

Banjo bolt bleeders seem common in the motorcycle world.

Ducati, Kawasaki and Magura (among others) are names that popped up when I was searching for this stuff. (1.0 and 1.25 pitch)

My understanding is that the banjo bleeder bolts are used for compact brake/clutch master or slave cylinders, where adding a separate bleeder screw would be bulky.

Polaris PN 1910886 is an M10x1.0 banjo bleeder. Length is unspecified, but can be estimated by counting pixels on pictures. I don't know what vehicle they use it on.

Generally these banjo bleeder bolts are 18-20 mm long; shorter than the 23 mm Fiero banjo bolt. I think this is because the motorcycle banjo fittings are less thick.

I ordered some M10x1.0x20 banjo bleeders:
Goodridge 992-31BNC

20 mm is about the longest available off the shelf. Not ideal in terms of thread engagement (at least with the Fiero banjo fitting), but I'm willing to roll with this, on my personal car.

[pmbrunelle]

So I worked on my calipers this weekend.

I began with cutting the Heli-Coil STI thread.

To align the drill press with the original hole axis, I screwed a long bolt (head cut off) into the banjo bolt thread. Then, I tightened the drill chuck onto the bolt shank, resulting in the caliper hanging from the chuck. Then, I adjusted the table to fix the caliper's position relative to the spindle.

IMG_5708.JPG (148.63 KiB) Viewed 3099 times

Once the caliper was C-clamped to the table, I could loosen the drill chuck, and unscrew the headless bolt. Drilling+tapping could proceed.

For tapping I used a cone in the chuck to help guide the tap. I had one hand turning the wrench, while my other hand applied a slight downwards pressure on the quill.

IMG_5710.JPG (185.75 KiB) Viewed 3099 times

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I bought a 90° Dremel adapter. With this, I was able to cut a trench from the highest point of the caliper cavity towards the banjo bolt.

IMG_5715.JPG (136.83 KiB) Viewed 3099 times

[ericjon262]

I like the fit up method, I'll have to remember that one.

[The Dark Side of Will]

Yeah, good thinking on how to clamp it down.

Did you try Old Europe for a group buy? Did I reply there?

[pmbrunelle]

I like the fit up method, I'll have to remember that one.

I was lucky enough that the caliper had a flat face that was stable.

My dad suggested that I could pour concrete around the caliper to cast it in place if I couldn't find a way to clamp it, but I didn't need to go that route.

Did you try Old Europe for a group buy? Did I reply there?

No, I didn't really desire the M10x1.5 banjo bolts enough to offer them to a wider audience besides this smaller group.

It was just less time/trouble/cost to go with the Heli-Coils; wasn't that bad at all.

This thread isn't really about a group buy anymore, it has evolved into modifying rear Seville calipers for use on my 84-87 Fiero.

[pmbrunelle]

I got the Heli-Coils installed and test-fitted the 20 mm long Goodridge banjo bleeder bolts.

IMG_5749.JPG (552.41 KiB) Viewed 3053 times

The banjo bleeder bolt cannot penetrate too deeply into the caliper. If it does, then air could become trapped above the end face of the banjo bleeder bolt.

I torqued up a random old hose with new copper washers.

IMG_5756.JPG (404.86 KiB) Viewed 3053 times

Penetration looks OK. I find this to be a satisfactory solution; I'm gonna roll with this.

I think that a stock-length (23 mm) banjo bleeder bolt would have penetrated too far into the calipers. That said, it may be possible to reduce the slope of the inverted trench to allow for the use of a 23 mm bolt.

[Honest Don]

Solid fix!

[The Dark Side of Will]

I think that a stock-length (23 mm) banjo bleeder bolt would have penetrated too far into the calipers. That said, it may be possible to reduce the slope of the inverted trench to allow for the use of a 23 mm bolt.

Since it's only for bleeding purposes, you could also make that cut WAY smaller... think just the edge of a dremel cutoff wheel.

[pmbrunelle]

My initial plan was actually to use a cutoff disc, but with the angle required to perform that cut, the Dremel body (or 90° gearbox) ended up interfering with the caliper casting.

The integral bridge on this caliper was a PITA with regards to tool interference; it would be easier to do this type of modification on a caliper that is bolted together from inboard and outboard parts.

It was only with a 1/4" spherical carbide burr and 90° gearbox that I was able to get the cutter where it needed to be with reasonable control (freehand).

I also wanted the groove to be large enough that I could visually (and with a paper-clip probe) inspect my progress for a monotonic slope all the way to the banjo hole.

I agree that the material removal for bleeding purposes could be much reduced. The groove has its actual shape due to implementation and inspection reasons.

[The Dark Side of Will]

https://www.mcmaster.com/4370A5/

https://www.mcmaster.com/4344A74/

You said you used a 90 degree gearbox, though.

Just another reason to put a 5 axis mill next to your garage throne.

[pmbrunelle]

The gearbox I used looked pretty much like the 4344A74.

I was actually using a Mastercraft (Canadian Tire house brand) rotary tool, not a Dremel-brand tool.

It seems that they mostly share the same interface at the nose of the tool, so the attachments work just the same.

[ericjon262]

https://www.mcmaster.com/4370A5/

https://www.mcmaster.com/4344A74/

You said you used a 90 degree gearbox, though.

Just another reason to put a 5 axis mill next to your garage throne.

Those flex shafts are pretty handy, they really help with getting into tight places. I used to have one years ago.

[pmbrunelle]

Aside: '78-'80 Caddy Fleetwood rear calipers share the narrower mounting center of the '80-'85 Seville calipers used in the Fiero Zettner brake package. The Seville calipers have 2" pistons, while the Fleetwood calipers have 2.5" pistons, at least per the catalog. This means that the Fleetwood calipers could be used with the Camaro or S10 front calipers to give the Fiero the "square" brake setup that works well on it.

Good find.

From the photo I could find, the bleeder is opposed to the parking brake cable mount, which could make these banjo bolt bleeder shenanigans unnecessary.

However, the Fleetwood calipers don't appear to be as readily available as the Seville calipers.

[The Dark Side of Will]

Thanks! I've had a "Zettner Upgrade Upgrade" thread in my head for a bit, but it hasn't been a high priority to post.

Yeah, the supply chain for the Fleetwood parts is a lot thinner than for the Seville parts.

[The Dark Side of Will]

LOL... I *thought* that the Motorhome disk conversion kit used the earlier wide mounting center calipers

It actually uses the later narrow mounting center calipers.
In looking for closely for calipers for the Motorhome, my dad found that the '78-'80 Fleetwood rear calipers I found are NOT HANDED.

It seemed sketch for GM to build them that way, but there's no technical reason not to.

I found this topic on CadillacForums: https://www.cadillacforums.com/threads/ ... cs.159416/

It has this photo:



As you can see, one caliper mounted forward and one caliper mounted aft.