• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

rear brakes

Share this page

oxford

oxford

Jedi Hopeful
Offline
Hi everyone
I am still fighting to get reasonable brakes on my BN4. They work but the pedal is soft and with a lot of travel. I clamped the hose leading to the rear and the pedal was hard. This leads me to believe that the problem is with the rears. There are no leaks and all cylinders are new. I adjust the shoes out so they lock the drums and then back them off to free the drums. If I then pump the brakes, the drums seem to free off more and need adjusting up again. When the rear shoes are tight on the drums, the pedal is harder.
I don't understand why the shoes need constant adjusting after pumping the pedal. I am doing this with the car on stands, not driving.
Could it be that the linings are too worn? They haven't been replaced.
This is driving me a bit mad! Any help would be appreciated.
Cheers
Matthew
 
oxford said:
Hi everyone
I am still fighting to get reasonable brakes on my BN4. They work but the pedal is soft and with a lot of travel. I clamped the hose leading to the rear and the pedal was hard. This leads me to believe that the problem is with the rears. There are no leaks and all cylinders are new. I adjust the shoes out so they lock the drums and then back them off to free the drums. If I then pump the brakes, the drums seem to free off more and need adjusting up again. When the rear shoes are tight on the drums, the pedal is harder.
I don't understand why the shoes need constant adjusting after pumping the pedal. I am doing this with the car on stands, not driving.
Could it be that the linings are too worn? They haven't been replaced.
This is driving me a bit mad! Any help would be appreciated.
Cheers
Matthew
Click to expand...

Yeah that is weird.

However:
i am going to suggest you replace the rear brake shoe lining. Maybe the adjuster is at its wits end and slips back a bit each time full pressure is applied.
Thus requiring you to readjust it
Just a guess
 
Also, it may be that your drums are not round any more. I think you said that you are adjusting the shoes up tight then bleeding the system. then back off the adjusters till the brakes are mostly free. You can have a slight drag. That is the correct way. BUT ! If your drums are not round anymore you may be bleeding the system when the shoes are at their tightest point then when you get your final adjustment the wheel cylinder will have to travel out a bit more to compensate for the out of round drums. In cases like this the best bet is to make everything new back there to keep the tolerances as close as possible. also I have found that it can be a bear to get a good bleed on the Healey brake system. The master cylinder does not displace much fluid and if you are bleeding the brakes by the pedal pumping method it takes forever. You usually can't gravity bleed them either because the hydraulic line goes higher than the master cylinder or the rear wheels so air stays at the highest point. I have used pressure bleeders to get the job done. Sometimes after getting the system pretty good with the pressure bleeder I have finished up with the manual pump method to get it to its very best.
 
Thanks Keoke and Vette. I have ordered new linings/ shoes on your advice. I'll see if that works. If not I'll have the drums machined.
Cheers
Matthew
 
All due respect for everyone. I was almost as frustrated bleeding my brakes as I was fitting my seat covers (and I still don't like the way they fit).
If a system is free of air, a minimal pedal movement will put the lining against the drum, in or out of round. Fluids are not compressible by us and I'd think they would have to be way out of round for that much pedal travel. You may have other issues if your drum is out of round. I think Keoke has hit on one possibility if your lining is very thin but I'd think the adjuster would take care of that as long as you have thread left on it where you could make it tighter if the lining were even thinner. When I rebuilt my brake system I found Vette's comment to be so true. It took me days to actually get them bled. Using pressure bleeding, pumping the pedal and opening and closing method, it mattered not. It seemed like it would never end. My wife had reached her limit of patience for pumping the pedal because I was convinced that no matter how much I pressure bled them from either the top or bottom, there were air bubbles that were not moving past certain areas. Pedal pumping finally worked although I do not know why it took so long. If I could have installed glass brake lines just to see , I would have. Once finally bled, I have had no issues for several years. I say bleed on!!
 
A friend of mine who works on other British automobiles swears that the best way to bleed them is to use a large syringe and force fluid from the bleeders up into the master cylinder. Obviously, you need to be cautious about overfilling the MC when you do this, and I have yet to give it a try, but it sounds no more difficult than any other way that hasn't worked.
 
roscoe said:
All due respect for everyone. I was almost as frustrated bleeding my brakes as I was fitting my seat covers (and I still don't like the way they fit).
If a system is free of air, a minimal pedal movement will put the lining against the drum, in or out of round. Fluids are not compressible by us and I'd think they would have to be way out of round for that much pedal travel. You may have other issues if your drum is out of round. I think Keoke has hit on one possibility if your lining is very thin but I'd think the adjuster would take care of that as long as you have thread left on it where you could make it tighter if the lining were even thinner. When I rebuilt my brake system I found Vette's comment to be so true. It took me days to actually get them bled. Using pressure bleeding, pumping the pedal and opening and closing method, it mattered not. It seemed like it would never end. My wife had reached her limit of patience for pumping the pedal because I was convinced that no matter how much I pressure bled them from either the top or bottom, there were air bubbles that were not moving past certain areas. Pedal pumping finally worked although I do not know why it took so long. If I could have installed glass brake lines just to see , I would have. Once finally bled, I have had no issues for several years. I say bleed on!!
Click to expand...

Agreed if they are spongy its air . Period . Keep bleeding .
 
Matthew, In regard to clearances in the shoe/drum relationship I think I forgot to mention be careful if you decide to turn the drums, there is a max diameter that is allowed otherwise there is the potential of pushing the wheel cylinders apart when the shoes get worn really done. I don't know what that diameter is maybe someone here can offer it. Or it may be listed in the shop manual.
In regard to out of round drum, I will bet that many of us have felt a pulsating pedal on a long descent in a variety of cars when holding a constant pressure on the pedal. I just rebuilt the brake system on a BugEye Sprite and when I first worked on it I tried to make things work for the owner because a previous mechanic had installed new wheel cylinders and hoses and rebuilt the Master Cylinder but they were still having trouble with the brakes. I replaced a suspect hose, bled the system, then tried to do a very meticulous adjustment but I could not get a good pedal. I test drove it anyway hoping that maybe some hard stops would push the air around and I could get a better bleed. While I drove it I noticed the brake pedal pulsing on constant pedal pressure. Got back to my shop and measured all the drums. They were out of round and near their designed limit. I put them back on and adjusted the brakes again. One or two adjusters were all the way out and the drums still weren't locked up. On another drum I could adjust it till the drum was locked but then when I forced the drum to rotate as it came off the "high spot" It was very free for about 5/8ths of its rotation then would tighten up again. There was no way that wheel was going to be adjusted properly with minimal clearance to the shoe. by just loosening that one brake set you would be introducing considerable "play" in the pedal. So I convinced the owner to get new pads and drums on all 4 wheels. Now everything is working great.
Having always been in search of a method to bleed brakes single handedly, I bought a reverse pressure bleeder from Groits last year. It is used at the wheel location and the pressure is provided by your shop air hose. It does work pretty good and is sufficient when working alone. But i did notice when bleeding brakes on the older Vette that I could not get the best pedal that I wanted. I finally got the wife to come out and do a few pumps on the pedal for each wheel and the system is good to go. The midyear and shark bodied Vettes brakes are also kind of hard to get a really good pedal. They have 4 piston calipers at each wheel and an unusual design.
 
vette said:
The midyear and shark bodied Vettes brakes are also kind of hard to get a really good pedal. They have 4 piston calipers at each wheel and an unusual design.
Click to expand...

You got that right.

The Motive pressure bleeder with the new metal top, using a large C-clamp to hold that in place, is the ticket. It gives me the best brakes I've ever had on C3s.
 
re: "... there is a max diameter that is allowed ..."

My local parts house, that's been in business forever, refused to turn my drums because they couldn't find a max diameter spec anywhere (I think in California it might be a felony to do so and, at the least, the shop could lose their business license).
 
Are rubber hoses to the brakes newer or old? 2 in front and one in the rear. Older hoses can bulge and make a spongy pedal.
 
I've had good single-handed bleeds with an inexpensive brake bleeder syringe from Amazon:
BleederSyringe_1.jpg
Sealing around the bleeder threads either with grease or teflon tape.

Mike Salter told me once that there was a BJ8 he was only able to bleed by forcing clean fluid upstream from the bleeder screws.
 
Thanks again everyone. Brilliant suggestions. The rubber hoses are new. I tried with a syringe made up a fitting for the blender thread. I seemed to get lots of air so it think the thread may have been leaking. The fact that clamping the rear hose makes the brake pedal hard seems to mean it's the rear brakes. As I said, I have ordered new shoes. They should be here next week. Hopefully that may make a difference. If not I'll just bleed, bleed, bleed!
Cheers
Matthew
 
Back
Top