100-6 front drum brakes?

[Dandare]

Speaking to a couple of ex BMC acquaintances they assert that having the pistons backed into the cylinders is the crucial part of bleeding these type of Girling systems (not unique to Healeys).

Can't hurt on any drum system? Some Lockheed front leading/trailing shoe types need the brakes adjusted up hard to achieve this!

Danny

 

[steveg]

Speaking to a couple of ex BMC acquaintances they assert that having the pistons backed into the cylinders is the crucial part of bleeding these type of Girling systems (not unique to Healeys).

Can't hurt on any drum system? Some Lockheed front leading/trailing shoe types need the brakes adjusted up hard to achieve this!

Danny

For the pistons to be all the way retracted, don't the shoes have to be in their most retracted position? Then the springs would push the pistons down. Enquiring minds want to know.

 

[Novamonte]

If you adjust the shoes hard, i.e. beyond the point when the shoes hit the drum, the other end of the shoe will push the piston further into the cylinder.

 

[Randy Forbes]

If you adjust the shoes hard, i.e. beyond the point when the shoes hit the drum, the other end of the shoe will push the piston further into the cylinder.

Exactly the point I was trying to make in post #17, though I didn't explain the reasoning behind it

 

[roscoe]

Brilliant. I've never heard that suggestion. If nothing else it reduces the volume of each slave cylinder and possibly eliminates some spot where air is trapped. I hope I remember it the next time I arrive at my wits' end. At least it is something to try.

 

[Dandare]

This is the system I was suggesting where you would lock up the brakes to achieve the least space between the pistons in the cylinder. The larger end of the piston is for the trailing shoe and this piston exerts 2.5 times more force than the small piston for any given pedal pressure and the shoes are free to slide in the slots in the end of the pistons and the fixed abutment at their other end to centralise them.

This is a Lockheed power assisted drum system and apart from my lowly Wolseley was used, albeit with self adjusters on the MkI Jag before it went to discs.
I thought both pics were going to be big ones but oh well!

Danny

 

[Randy Forbes]

The four (4) front wheel cylinders for the 100 & 100/6 utilize a single piston in a blind cylinder bore, for a twin leading shoe (self-servo) system. The trailing edge of the shoe(s) rest on the blind end of the opposite shoe's cylinder.

Picture courtesy of Moss Motors: https://mossmotors.com/austin-healey-100-100-6-3000/brakes/front-drum-brakes

 

[Dandare]

A Lockheed twin leading shoe set-up from the same era is much the same apart from the micram adjusters. There didn't seem to be any bleeding problems however mainly due to the bridge pipe looping down from the wheel cylinder unlike the Girling system.

Danny

 

[Chet Zerlin]

Returned from vacation last week and went by my shop today determined to try all of the great ideas outlined here and report back to you all what worked and what didn't.
Before I had left on vacation I had propped a stick to hold down the brake pedal - trying in sheer frustration for the miracle cure some have reported on this form.
When I removed the stick today I had a hard brake pedal! I left it alone for an hour or two and same result. Hard brake pedal!

I'm suspecting that the constant pressure finally moved the air bubble....somewhere(?).
I'll check it again next week to see if it's gone back to the old soft pedal but for now I'm a happy camper....

Chet

 

[Chet Zerlin]

Well....apparently I spoke too soon
Yesterday my brake pedal returned to its original "soft pedal" condition.

So next up are trying all of the excellent suggestions given here.

I'll report back...

Chet

 

[Leew]

It's a long while ago Chet, but I assume you solved the soft pedal issue. How did you do it?

 

[Chet Zerlin]

Thank you for reminding me of this and so sorry that I completely forgot my promise to "report back"!
After trying everything that was recommended here to no effect, I decided to just upgrade my braking system by completely removing the front drum brake assemblies and installing disc brakes instead. I immediately realized a huge difference and much improved pedal feel. I've carefully packaged up the original drum brake assemblies for "posterity" (since I'm not planning on selling my Healey anytime soon) and put them on a shelf in my garage. I would imagine that there was some faulty part(s) somewhere in the system that was causing my issues but after replacing the wheel cylinders, spending hours trying every method of brake bleeding recommended and even staring at them for a long time nothing worked.
So basically the answer to your question of how did I solve my soft pedal issue is "I changed everything in the front of the car that was attached to it" :smile-new:

Chet

 

[John Turney]

....
So basically the answer to your question of how did I solve my soft pedal issue is "I changed everything in the front of the car that was attached to it" :smile-new:

Chet

That's what I did.

 

[steveg]

I had removed my front drum brakes for my Toyota 4-piston disc conversion. Asked my favorite mechanic Russ Thompson if he wanted them. He said no one ever goes back to the drums and they're a drag on the market and might as well throw them away.

 

[Leew]

I’ve had installed the Denis Welch girling front disc conversion and the mechanic is pulling out his hair trying to find where the air is coming from as he gets a good pedal but it disappears

 

[steveg]

I’ve had installed the Denis Welch girling front disc conversion and the mechanic is pulling out his hair trying to find where the air is coming from as he gets a good pedal but it disappears

Maybe the master cyl needs in-situ bleeding.
Check out this thread:
http://www.britishcarforum.com/bcf/...ding-quot-issue/page2&highlight=recirculating

 

[pan]

G'day Chet,
While I don't wish to sound like I am criticising you for deciding to fit disc brakes to your 100-Six (it is after all, a desirable conversion) I was disappointed not to find out what the original problem was.
In your first post on the subject, you asked if the long pedal was a typical characteristic of twin-leading shoe drum brakes. As you have been advised, it certainly isn't and as Derek Job pointed out this design of brake was considered desirable for high-performance cars before the widespread adoption of disc brakes in the late 1950s. To resort to curing an obviously malfunctioning brake by converting to a different system was not only expensive, but also risky because there was no guarantee that it would solve the problem, should that problem have been elsewhere in the system.
My BN1 has similar brakes to the 100-Six (albeit with narrower linings) and I have rarely had trouble achieving a satisfactory pedal when the job is done according to the manufacturer's procedure (I'm not trained as a mechanic, so getting creative isn't a good idea!). I'm happy to say that I have never had to resort to bench bleeding the master cylinder or using Randy's method of cracking the seal on the connecting pipe. There was obviously something wrong with your brakes and I think we all would have benefited from learning what that very obscure problem was, and the solution.
Cheers from down under. Here's looking forward to being able to enjoy our Healeys again in the near future.
Alwyn