convert to manual brakes
#201
TGO Supporter/Moderator
iTrader: (12)
Join Date: Jul 1999
Location: SALEM, NH
Posts: 11,784
Likes: 0
Received 94 Likes
on
79 Posts
Car: '88 Formula, '94 Corvette, '95 Bird
Engine: LC9, LT1
Transmission: TKX, 4L60E
Axle/Gears: 3.42, 3.23
Re: convert to manual brakes
What would be the appropriate bore size to use with factory front calipers, and factory PBR rear calipers?
-- Joe
-- Joe
#206
TGO Supporter/Moderator
iTrader: (12)
Join Date: Jul 1999
Location: SALEM, NH
Posts: 11,784
Likes: 0
Received 94 Likes
on
79 Posts
Car: '88 Formula, '94 Corvette, '95 Bird
Engine: LC9, LT1
Transmission: TKX, 4L60E
Axle/Gears: 3.42, 3.23
Re: convert to manual brakes
Ok. So I've got the strange 1.032" bore master, and I've set the pedal for a 6:1 ratio.
Right now I have factory front brakes, and rear LT1 PBR brakes.
Should I swap the front calipers for non-low drag calipers?
I was looking at speedway big bore calipers:
http://www.speedwaymotors.com/Big-Bo...per,25158.html
They are non-low drag, so they should immediately clamp the rotor the second the pedal is pressed.
Consensus among members?
-- Joe
Right now I have factory front brakes, and rear LT1 PBR brakes.
Should I swap the front calipers for non-low drag calipers?
I was looking at speedway big bore calipers:
http://www.speedwaymotors.com/Big-Bo...per,25158.html
They are non-low drag, so they should immediately clamp the rotor the second the pedal is pressed.
Consensus among members?
-- Joe
#207
Senior Member
iTrader: (5)
Join Date: May 2005
Location: Midwest IL
Posts: 831
Likes: 0
Received 1 Like
on
1 Post
Car: 1984 Z28
Engine: Alky 360
Transmission: TH400, Freakshow 9.5"
Axle/Gears: 9" 4.71
Re: convert to manual brakes
I am still using the factory fronts, curious to see how it works if you change these out. For me I am waiting and saving pennies until I get wilwoods light weight front setup.
#209
Senior Member
iTrader: (5)
Join Date: May 2005
Location: Midwest IL
Posts: 831
Likes: 0
Received 1 Like
on
1 Post
Car: 1984 Z28
Engine: Alky 360
Transmission: TH400, Freakshow 9.5"
Axle/Gears: 9" 4.71
Re: convert to manual brakes
First pump, about 1/3 pedal travel, however I have a 15/16 bore cylinder. I foot brake the car and push the pedal down 1/2 way, set the line lock then push into the beams, then, while holding the line lock (biondo) I pump the brakes 2 more times.
With that I have a good pedal, and am not worried about locking them up. When I go through the beams I push half way down, then let up and start back down on the pedal.
I am sure there are better ways, but that has always worked good for me.
With that I have a good pedal, and am not worried about locking them up. When I go through the beams I push half way down, then let up and start back down on the pedal.
I am sure there are better ways, but that has always worked good for me.
#211
TGO Supporter/Moderator
iTrader: (12)
Join Date: Jul 1999
Location: SALEM, NH
Posts: 11,784
Likes: 0
Received 94 Likes
on
79 Posts
Car: '88 Formula, '94 Corvette, '95 Bird
Engine: LC9, LT1
Transmission: TKX, 4L60E
Axle/Gears: 3.42, 3.23
Re: convert to manual brakes
I ran it on my thirdgen for a little while. I have hydroboost on my other vehicles (daily drivers). For a daily driver hydroboost is great, especially if it's a blown motor. Hydroboost is consistent.
The down side to hydroboost is the hoses and space everything takes up. My firebird is more of a track-only car, and I felt that I'd rather trade a simple pulley setup and manual brakes.
-- Joe
The down side to hydroboost is the hoses and space everything takes up. My firebird is more of a track-only car, and I felt that I'd rather trade a simple pulley setup and manual brakes.
-- Joe
#212
Member
Join Date: Sep 2014
Location: south central Texas
Posts: 474
Likes: 0
Received 0 Likes
on
0 Posts
Car: BUILDING 1985 HARD TOP T/A
Engine: sbc
Transmission: stick
Axle/Gears: GM
Re: convert to manual brakes
Thanks! I'm looking at a procharged sbc with dry sump, I'm running 14" rotors & 6 piston calipers, but for the hp & tq this thing is going to make coupled with the top speed I'm trying to achieve. ... I want as much WOW! as possible.
#214
Member
Join Date: Sep 2014
Location: south central Texas
Posts: 474
Likes: 0
Received 0 Likes
on
0 Posts
Car: BUILDING 1985 HARD TOP T/A
Engine: sbc
Transmission: stick
Axle/Gears: GM
Re: convert to manual brakes
Looking at 32psi ( F3-121A), inter-cooled, 9.5:1 compression, 14° heads, 900 cfm c&s blow thru, 400+ cubes ( custom bore&stroke ).... 2000+ hp
#215
TGO Supporter/Moderator
iTrader: (12)
Join Date: Jul 1999
Location: SALEM, NH
Posts: 11,784
Likes: 0
Received 94 Likes
on
79 Posts
Car: '88 Formula, '94 Corvette, '95 Bird
Engine: LC9, LT1
Transmission: TKX, 4L60E
Axle/Gears: 3.42, 3.23
Re: convert to manual brakes
My car won't stop safely. I've bleed the crap out of the calipers.
I'm going to buy the speedway non-low drag calipers and give that a try. I think the low-drag have way too much take up, so the brakes don't actually start clamping the rotor until the pedal is almost at the end of it's travel.
-- Joe
I'm going to buy the speedway non-low drag calipers and give that a try. I think the low-drag have way too much take up, so the brakes don't actually start clamping the rotor until the pedal is almost at the end of it's travel.
-- Joe
#216
Re: convert to manual brakes
I'd figure out the problem before replacing more parts. Does the pedal come up if you pump it? Plug one section of the MC and see how the pedal is, this will show you what section the problem is in. If necessary plug both outlets, if pedal is low it's in the MC.
#217
TGO Supporter/Moderator
iTrader: (12)
Join Date: Jul 1999
Location: SALEM, NH
Posts: 11,784
Likes: 0
Received 94 Likes
on
79 Posts
Car: '88 Formula, '94 Corvette, '95 Bird
Engine: LC9, LT1
Transmission: TKX, 4L60E
Axle/Gears: 3.42, 3.23
Re: convert to manual brakes
I did some more research and it seems the low-drag calipers have a lip in the seal which retracts the piston in the bore. This requires some fluid to take up the clearance before they actually start compressing the pad. It seems others have had the same problem I'm having, so I ordered the large bore calipers anyway. Will give that a try this week.
The question I have now is, are my rear PBR calipers going to have the same issue...
-- Joe
#218
TGO Supporter/Moderator
iTrader: (12)
Join Date: Jul 1999
Location: SALEM, NH
Posts: 11,784
Likes: 0
Received 94 Likes
on
79 Posts
Car: '88 Formula, '94 Corvette, '95 Bird
Engine: LC9, LT1
Transmission: TKX, 4L60E
Axle/Gears: 3.42, 3.23
Re: convert to manual brakes
You guys have any issues with the rod binding in the master?
Mine seems ok when pressing on the brackets, but when releasing the pedal it binds, so the last 1/2" or so of (pedal) travel it has to be pulled by hand. I get an audible "squeak", so something is binding. thought it was the heim joint but doesn't appear to be.
I wonder if maybe rod is binding in the master itself due to the angle. ?
-- Joe
Mine seems ok when pressing on the brackets, but when releasing the pedal it binds, so the last 1/2" or so of (pedal) travel it has to be pulled by hand. I get an audible "squeak", so something is binding. thought it was the heim joint but doesn't appear to be.
I wonder if maybe rod is binding in the master itself due to the angle. ?
-- Joe
#219
Moderator
Join Date: Jul 1999
Location: 51°N 114°W, 3500'
Posts: 17,169
Likes: 0
Received 136 Likes
on
114 Posts
Car: 87 IROC L98
Engine: 588 Alcohol BBC
Transmission: Powerglide
Axle/Gears: Ford 9"/31 spline spool/4.86
Re: convert to manual brakes
To get the proper angle, the rod should be attached to the brake pedal roughly 1" higher on the pedal. This will also give more mechanical leverage.
#220
TGO Supporter/Moderator
iTrader: (12)
Join Date: Jul 1999
Location: SALEM, NH
Posts: 11,784
Likes: 0
Received 94 Likes
on
79 Posts
Car: '88 Formula, '94 Corvette, '95 Bird
Engine: LC9, LT1
Transmission: TKX, 4L60E
Axle/Gears: 3.42, 3.23
Re: convert to manual brakes
I just get this slight bind when the pedal is almost all the way returned. I have to pull it back the last little bit.
I'm torn between getting rid of the heim joint and using a traditional brake push rod (that floats), or trying a pedal return spring like on manual brake corvettes.
But I was wondering if maybe the ball end of the pushrod is getting cocked in the master bore. maybe grind it a hair undersize ? On the mopar master, the rod goes in like 1" inches so it doesn't give a whole lot of leeway when it comes to angle.
-- Joe
#221
Moderator
Join Date: Jul 1999
Location: 51°N 114°W, 3500'
Posts: 17,169
Likes: 0
Received 136 Likes
on
114 Posts
Car: 87 IROC L98
Engine: 588 Alcohol BBC
Transmission: Powerglide
Axle/Gears: Ford 9"/31 spline spool/4.86
Re: convert to manual brakes
Not all heim joints are the same. Mine just uses a heim joint to attach a 3/8" rod to the brake pedal that pushes into the master cylinder. I don't think it was anything fancy. It may have even been the OEM rod. If using round stock for a rod, make sure the end that goes into the master cylinder is ground to a rounded end.
This picture might be a few pages back in the thread but here it is again. Glad it doesn't look that ugly under my dash any more.
This picture might be a few pages back in the thread but here it is again. Glad it doesn't look that ugly under my dash any more.
#222
TGO Supporter/Moderator
iTrader: (12)
Join Date: Jul 1999
Location: SALEM, NH
Posts: 11,784
Likes: 0
Received 94 Likes
on
79 Posts
Car: '88 Formula, '94 Corvette, '95 Bird
Engine: LC9, LT1
Transmission: TKX, 4L60E
Axle/Gears: 3.42, 3.23
Re: convert to manual brakes
Not all heim joints are the same. Mine just uses a heim joint to attach a 3/8" rod to the brake pedal that pushes into the master cylinder. I don't think it was anything fancy. It may have even been the OEM rod. If using round stock for a rod, make sure the end that goes into the master cylinder is ground to a rounded end.
This picture might be a few pages back in the thread but here it is again. Glad it doesn't look that ugly under my dash any more.
This picture might be a few pages back in the thread but here it is again. Glad it doesn't look that ugly under my dash any more.
I'll play with it more tomorrow. It's got to be the ball end is too big.
-- Joe
#223
Former Sponsor
Join Date: Mar 2004
Location: Houston, Texas
Posts: 100
Likes: 0
Received 0 Likes
on
0 Posts
Car: 1980 El Camino
Engine: Turbocharged 305
Transmission: TH350 (future 4L80E)
Axle/Gears: stock 2.56 posi
Re: convert to manual brakes
I am also guessing that the BMR push rod slides into the master cylinder piston's retention "hole" or "cup".
When your brake pedal is fully pressed in when braking, the push rod should be inline with the master cylinder piston. When it returns to the resting position, the push rod will start binding inside the master cylinder piston's retention "hole" or "cup" because it has a slight downward angle. The retention "hole" or "cup" is not much larger is diameter than the push rod itself which is causing the binding.
Best remedy is to reduce the diameter of the push rod that slides into the cup. You can keep the same diameter at the tip of the push rod that goes inside the retention "cup", but neck it down from there to just outside the retention "cup". This should give you enough clearance for it not to bind.
If the push rod is 3/8" in diameter, just neck it down to 5/16" in diameter. I don't have the exact diameters in front of me, this would be an example.
I hope what I wrote made sense. Let me know if you have additional questions.
#224
TGO Supporter/Moderator
iTrader: (12)
Join Date: Jul 1999
Location: SALEM, NH
Posts: 11,784
Likes: 0
Received 94 Likes
on
79 Posts
Car: '88 Formula, '94 Corvette, '95 Bird
Engine: LC9, LT1
Transmission: TKX, 4L60E
Axle/Gears: 3.42, 3.23
Re: convert to manual brakes
I picked up another pushrod, with the little palstic thing and stuck it inside the master. This pushrod only allows a very slight angle to drop (and prevents it from binding) I'm guessing because of that little plastic bushing:
But this requires me to run the hole 1 5/8" above the stock location. I'm not sure that I'm going to get enough piston travel. It's 2 1/8" down from the pivot.
I can grind the pushrod down and remove that little bushing, but I can't help but feel like that's against the design.
I feel like the adapter on the firewall should have been milled at a slight angle (kinda like the brake booster bracket is). I also noticed that the fluid in the resevoir is about 1/2" higher in the front than the back, meaning the front is nosing down. This seems to make sense based on my pushrod issue.
So.. I know what the problem(s) are. I'm not sure what the correct solution is.
-- Joe
#225
Member
iTrader: (1)
Re: convert to manual brakes
Ok so. the BMR pushrod is missing the little plastic bushing thing, so it allows it to be at a more severe angle then correct. To use the bottom hole (1.25" above stock) the rod binds on the master itself.
I picked up another pushrod, with the little palstic thing and stuck it inside the master. This pushrod only allows a very slight angle to drop (and prevents it from binding) I'm guessing because of that little plastic bushing:
But this requires me to run the hole 1 5/8" above the stock location. I'm not sure that I'm going to get enough piston travel. It's 2 1/8" down from the pivot.
I can grind the pushrod down and remove that little bushing, but I can't help but feel like that's against the design.
I feel like the adapter on the firewall should have been milled at a slight angle (kinda like the brake booster bracket is). I also noticed that the fluid in the resevoir is about 1/2" higher in the front than the back, meaning the front is nosing down. This seems to make sense based on my pushrod issue.
So.. I know what the problem(s) are. I'm not sure what the correct solution is.
-- Joe
I picked up another pushrod, with the little palstic thing and stuck it inside the master. This pushrod only allows a very slight angle to drop (and prevents it from binding) I'm guessing because of that little plastic bushing:
But this requires me to run the hole 1 5/8" above the stock location. I'm not sure that I'm going to get enough piston travel. It's 2 1/8" down from the pivot.
I can grind the pushrod down and remove that little bushing, but I can't help but feel like that's against the design.
I feel like the adapter on the firewall should have been milled at a slight angle (kinda like the brake booster bracket is). I also noticed that the fluid in the resevoir is about 1/2" higher in the front than the back, meaning the front is nosing down. This seems to make sense based on my pushrod issue.
So.. I know what the problem(s) are. I'm not sure what the correct solution is.
-- Joe
Also if I should change front and rear calipers to non drag Afco or just front and if so, which master goes with that setup?
#226
TGO Supporter/Moderator
iTrader: (12)
Join Date: Jul 1999
Location: SALEM, NH
Posts: 11,784
Likes: 0
Received 94 Likes
on
79 Posts
Car: '88 Formula, '94 Corvette, '95 Bird
Engine: LC9, LT1
Transmission: TKX, 4L60E
Axle/Gears: 3.42, 3.23
Re: convert to manual brakes
I know it's been awhile, but how's your brakes? I have stock disc brakes front/rear and can't decide which master will be best, 7/8, 15/16, or 1.03
Also if I should change front and rear calipers to non drag Afco or just front and if so, which master goes with that setup?
Also if I should change front and rear calipers to non drag Afco or just front and if so, which master goes with that setup?
Everything is in a box, for sale.
I couldn't get the geometry right or something. I don't know, but I gave up.
It could be just that I'm more picky than others, or maybe my standards are higher, but there was no doubt in my mind it was not as good as power.
-- Joe
#227
Member
iTrader: (1)
Re: convert to manual brakes
Went back to power.
Everything is in a box, for sale.
I couldn't get the geometry right or something. I don't know, but I gave up.
It could be just that I'm more picky than others, or maybe my standards are higher, but there was no doubt in my mind it was not as good as power.
-- Joe
Everything is in a box, for sale.
I couldn't get the geometry right or something. I don't know, but I gave up.
It could be just that I'm more picky than others, or maybe my standards are higher, but there was no doubt in my mind it was not as good as power.
-- Joe
#228
Former Sponsor
Join Date: Mar 2004
Location: Houston, Texas
Posts: 100
Likes: 0
Received 0 Likes
on
0 Posts
Car: 1980 El Camino
Engine: Turbocharged 305
Transmission: TH350 (future 4L80E)
Axle/Gears: stock 2.56 posi
Re: convert to manual brakes
I know it's been awhile, but how's your brakes? I have stock disc brakes front/rear and can't decide which master will be best, 7/8, 15/16, or 1.03
Also if I should change front and rear calipers to non drag Afco or just front and if so, which master goes with that setup?
Also if I should change front and rear calipers to non drag Afco or just front and if so, which master goes with that setup?
From my experience, any rebuild/reman caliper should be a normal, NON drag caliper.
Depending on your rear caliper piston diameter, you will need either a 7/8" or 15/16" bore master cylinder. For stock sized calipers from and rear, the 1.03" bore is too large and will cause a hard pedal with low clamping forces at the calipers.
If you are going to use the stock size front calipers and rear calipers with a piston diameter under 2.0" (or under 3.14 square inches of piston area) go with the 7/8" bore master cylinder. Above 2.0" in diameter (or above 3.14 square inches of piston area) go with a 15/16" or 24mm bore master cylinder.
If you calipers will be the same metric calipers front and rear, you will need to go with a 15/16" or 24mm bore master cylinder.
Last edited by manualbrakes.com; 03-10-2017 at 08:31 AM.
#229
COTM Editor
iTrader: (22)
Join Date: Mar 2001
Posts: 10,073
Likes: 0
Received 1,941 Likes
on
1,325 Posts
Car: '89 Firebird
Engine: 7.0L
Transmission: T56
#230
Former Sponsor
Join Date: Mar 2004
Location: Houston, Texas
Posts: 100
Likes: 0
Received 0 Likes
on
0 Posts
Car: 1980 El Camino
Engine: Turbocharged 305
Transmission: TH350 (future 4L80E)
Axle/Gears: stock 2.56 posi
#231
Member
iTrader: (1)
Re: convert to manual brakes
The front calipers are the only ones that are LOW drag and will need a step bore master cylinder to work. If you go with a strait bore master cylinder, the front calipers will need to be changed to NON low drag (normal) calipers.
From my experience, any rebuild/reman caliper should be a normal, NON drag caliper.
Depending on your rear caliper piston diameter, you will need either a 7/8" or 15/16" bore master cylinder. For stock sized calipers from and rear, the 1.03" bore is too large and will cause a hard pedal with low clamping forces at the calipers.
If you are going to use the stock size front calipers and rear calipers with a piston diameter under 2.0" (or under 3.14 square inches of piston area) go with the 7/8" bore master cylinder. Above 2.0" in diameter (or above 3.14 square inches of piston area) go with a 15/16" or 24mm bore master cylinder.
If you calipers will be the same metric calipers front and rear, you will need to go with a 15/16" or 24mm bore master cylinder.
From my experience, any rebuild/reman caliper should be a normal, NON drag caliper.
Depending on your rear caliper piston diameter, you will need either a 7/8" or 15/16" bore master cylinder. For stock sized calipers from and rear, the 1.03" bore is too large and will cause a hard pedal with low clamping forces at the calipers.
If you are going to use the stock size front calipers and rear calipers with a piston diameter under 2.0" (or under 3.14 square inches of piston area) go with the 7/8" bore master cylinder. Above 2.0" in diameter (or above 3.14 square inches of piston area) go with a 15/16" or 24mm bore master cylinder.
If you calipers will be the same metric calipers front and rear, you will need to go with a 15/16" or 24mm bore master cylinder.
Also, gonna run new lines so can I eliminate proportioning valve like some have suggested? Skinnies up front.
Last edited by indebt; 03-10-2017 at 11:57 AM.
#232
Former Sponsor
Join Date: Mar 2004
Location: Houston, Texas
Posts: 100
Likes: 0
Received 0 Likes
on
0 Posts
Car: 1980 El Camino
Engine: Turbocharged 305
Transmission: TH350 (future 4L80E)
Axle/Gears: stock 2.56 posi
Re: convert to manual brakes
In my opinion, With large, wide tires in the back and small, skinny tires up front, the prop valve becomes fairly useless. The bias that is built in to the stock prop is for the same size tires on all four corners. You will also NOT need an adjustable prop valve in the rear line for rear disc brakes as it will, most likely, be turned open all the way anyway.
#233
Member
iTrader: (1)
Re: convert to manual brakes
In my opinion, With large, wide tires in the back and small, skinny tires up front, the prop valve becomes fairly useless. The bias that is built in to the stock prop is for the same size tires on all four corners. You will also NOT need an adjustable prop valve in the rear line for rear disc brakes as it will, most likely, be turned open all the way anyway.
I guess if you are drilling a 2" higher hole, then having MC moved up is optimal for pushrod. Trying to read all your posts over this topic.
Last edited by indebt; 03-10-2017 at 10:55 AM.
#234
Former Sponsor
Join Date: Mar 2004
Location: Houston, Texas
Posts: 100
Likes: 0
Received 0 Likes
on
0 Posts
Car: 1980 El Camino
Engine: Turbocharged 305
Transmission: TH350 (future 4L80E)
Axle/Gears: stock 2.56 posi
Re: convert to manual brakes
I recommend going up on the firewall and mounting the master cylinder between the upper bolt holes from the vacuum booster bracket. From this mounting location for the master cylinder, you can drill a hole in the brake pedal arm 2.0" down from the brake pedal pivot point and have the correct push rod geometry and a higher 6 to 1 pedal ratio. I would not recommend this pedal ratio with the master cylinder mounted lower than the upper two hole as it will have bad push rod geometry that will decrease master cylinder piston stroke during the last 1/2 of the brake pedal range of motion. Its easier to see what I am talking about with the brake pedal assembly mocked up on the bench and watching the geometry as the brake pedal goes through its range of motion.
If you use other manual brake kits on the market, go by their recommendation on where to drill on the pedal. Regardless of which manual brake KIT you purchased, the push rod should be level (or inline) with the master cylinder piston at the END (or bottom) of the pedal stroke to keep the geometry correct. This is how the geometry is set up on the manualbrakes.com KIT and is optimal for the 3rd gen f-body brake pedal assembly.
Thread
Thread Starter
Forum
Replies
Last Post
1992 Trans Am
History / Originality
27
05-10-2023 07:19 PM
Hellbillydeluxe
Tech / General Engine
10
09-22-2015 09:58 PM
1992 Trans Am
Engine/Drivetrain/Suspension Parts for Sale
1
08-08-2015 08:16 PM