I just measured my pedal as I'm in the garage working anyhow. My pedal is 6" at rest off the floor, and if I stand on it as hard as I can it's 2 1/2 off the floor. I can't go that additional 1/2.
Anybody using a 15/16" bore master cylinder
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threewood
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I'll measure it here when I get out of work.
I have read that Chrysler stopped using residual valves in 1975 and that the wheel cylinders had expansion valves instead.
Here is a post from cuda-challengers.com Looking for thoughts on this...Since the mid 1970s Mopar eliminated the residual valve in all their master cylinders and then used wheel cylinders with expanders to prevent air entry into the system for a disc/drum brakes. I called Wilwood for their input and was told none of their MCs come with residual valves and using the newer wheel cylinders is correct and no residual valves are needed. The Disc-O-Tech article also mentions the elimination of residual valves.
I'm currently looking at a Right Stuff 15/16" MC, which does not have any residual valves. Wilwood stated only if the MC is mounted below the level of the calipers would a residual valve be required for both front and rear brakes.
Absent any compelling info, that's the route I plan on taking. Actually, I'm not sure if my current 1" bore MC has a residual valve and the brakes are solid now and I do have new wheel cylinders with the expanders.
Thoughts?
Here is a post from cuda-challengers.com Looking for thoughts on this...Since the mid 1970s Mopar eliminated the residual valve in all their master cylinders and then used wheel cylinders with expanders to prevent air entry into the system for a disc/drum brakes. I called Wilwood for their input and was told none of their MCs come with residual valves and using the newer wheel cylinders is correct and no residual valves are needed. The Disc-O-Tech article also mentions the elimination of residual valves.
I'm currently looking at a Right Stuff 15/16" MC, which does not have any residual valves. Wilwood stated only if the MC is mounted below the level of the calipers would a residual valve be required for both front and rear brakes.
Absent any compelling info, that's the route I plan on taking. Actually, I'm not sure if my current 1" bore MC has a residual valve and the brakes are solid now and I do have new wheel cylinders with the expanders.
Thoughts?
Interesting. I installed new rear wheel cylinders along with everything else in this car. Maybe I have valves at both ends on the rear. I think I am going to call Cass to get his opinion when I get a chance.
Apparently new rear cylinders are ALL made with the valves and have been for a good number of years. I think E-berg mentions that in his Disc-o-brake article.
threewood
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Ok, pedal up is 7 1/2" to the floor, pedal all the way down is 3" to the floor. So 4 1/2" of travel.
Yours is not too far off from mine. Have you tried a panic stop from about 30 mph to see how they act?
Yours is not too far off from mine. Have you tried a panic stop from about 30 mph to see how they act?
Just nearing completion of the restoration and haven't started the car yet. Your measurement makes me feel better about the cylinder. I bet I have a defective prop valve causing the light to stay on. And this has already been replaced once......
Thought I would update this thread to the current state. With this virus thing going on Cass is unable to talk on the phone for some reason (I didn't ask why), but he is emailing. And we have been doing a lot of that the last couple of days. He is so great to deal with, his customer support is second to none.
So, we are both learning more about master cylinders and wheel cylinders. Cass has talked to the manufacturers of both and taken parts in his stock apart to get this figured out.
What he learned is the the 15/16", 1 1/32", and 1 1/8" aluminum master cylinders that he sells for disc/drum manual systems do not have any residual pressure valves in them. But the 15/16" iron mc DOES have a pressure valve installed in the port for the rear brakes only, and this is the one I have.
He talked to the somebody from where he gets his wheel cylinder from and was told "A modern master cylinder does not incorporate a residual pressure valve because modern wheel cylinders are designed to keep air from entering the system when not in use". My next question to him was should I be removing the valve in my mc, and he was told no, leave it in.
I was not aware how popular the aluminum master cylinders are. Cass says he sells them 100 to 1 compared to the cast versions.
So long story short, everything I have is supposed to be compatible and we are thinking I have a defective prop valve switch which is shorted to ground and bringing on my dash warning light. He is sending me another valve. This is the third one going in this car as the first one wouldn't seal because of a ding in the valve body. Actually the second one he sent me had a bad surface on the top nut so I had to make one out of 2. These valves are such a pain in the a$$ to replace with the motor, steering, and headers in the car....
So, we are both learning more about master cylinders and wheel cylinders. Cass has talked to the manufacturers of both and taken parts in his stock apart to get this figured out.
What he learned is the the 15/16", 1 1/32", and 1 1/8" aluminum master cylinders that he sells for disc/drum manual systems do not have any residual pressure valves in them. But the 15/16" iron mc DOES have a pressure valve installed in the port for the rear brakes only, and this is the one I have.
He talked to the somebody from where he gets his wheel cylinder from and was told "A modern master cylinder does not incorporate a residual pressure valve because modern wheel cylinders are designed to keep air from entering the system when not in use". My next question to him was should I be removing the valve in my mc, and he was told no, leave it in.
I was not aware how popular the aluminum master cylinders are. Cass says he sells them 100 to 1 compared to the cast versions.
So long story short, everything I have is supposed to be compatible and we are thinking I have a defective prop valve switch which is shorted to ground and bringing on my dash warning light. He is sending me another valve. This is the third one going in this car as the first one wouldn't seal because of a ding in the valve body. Actually the second one he sent me had a bad surface on the top nut so I had to make one out of 2. These valves are such a pain in the a$$ to replace with the motor, steering, and headers in the car....
Glenwood
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After finishing a 4 wheel disc conversion and 15/16" bore MC from Cass, the travel is about 4". I got a chance to finally take a drive yesterday and found the brakes to be too soft. They work needing more distance to stop, but could not lock them up. This is not satisfactory imo, so I'll bleed them and the MC again but I'm not sure this MC is the right fit for this system.
not so famous bob
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Not so, I have a 15/16'' bore master on mine w/ 4 wheel manual discs, very little travel and great pedal heigth > normal really.
I have been thinking about going to a 7/8'' master, but isnt that big a problem, altho I cant lock them up.
Glenwood
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Which MC are you using? I have the aluminum dual from Cass for my 4 wheel manual discs.
I have the 15/16" iron master cylinder. We found out that the switch in mt prop valve was bad. Cass sent me new valve and I got it installed yesterday. dash warning light is now off. Bled out everything again and I still have the same pedal travel as before. Granted I have not started the car yet to see how they work. Maybe they will be fine, but there sure is a lot of pedal travel imo.
Sure sounds like you still have some air in your system?
2 things seem odd to me. Everybody says that a 15/16" cylinder should have some travel and that you can't lock up the wheels. Shouldn't a guy always be able to lock them up? Unless of course we are talking about the newer anti lock systems.
Glenwood
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How much pedal travel do you have?
I had a nightmare trying to get a good bleed. As I mentioned in the video my colleague from work (a mechanical engineer who worked at an independent BMW Porsche shop during college) bailed me out. One of the In Line Tube replacement lines had a bad double flare; he made me a new brake line using his Eastwood jig. We had to bleed, bleed, and bleed some more to get things right. He also had to tighten and torque the lines at the proportioning block to the point of rounding off the nuts to get a good seal. He blamed the poor quality of In Line Tube lines as part of my problem, but I am in the minority here as 99% of FBBO and FABO people praise In Line Tube products.
Anyhow, the brakes work great and I'm not messing with them ever again!
See post #21.
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