68 Master Cylinder
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68 Master Cylinder
I have a manual brake 68 with a 1 " piston Master cylinder. I want to reduce pedal pressure and a friend suggested a smaller diameter piston in the master. The standard manual MC uses a 1 " piston but I see someone on ebay advertises a 15/16 piston unit. Has anyone had any experience with this master ??
Is my vette stock?? HAHA
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Theres 2 different masters, one for power brakes and one for manual brakes. 1.125 bore (power) and 1.00 bore (standard) There is alos 2 holes for the brake booster pushrod in your brake pedal. The upper is for manual brakes, the lower is for power brakes. verify the rod is in the correct hole before buying anything, the you may consider deglazing your discs and guying some ceramic brake pads.
Last year I replaced my calipers that were leaking and put on new organic pads. It stopped great and was beautiful until I heated up the brakes on a road race course. The next day it felt like I was stepping on a brick and the brakes fely like I had to use a lot of pressure to stop. The pads had hardened and the discs where slightly glazed. I bought a disc brake hone and put on ceramic pads. I only got a short drive but they were very responsive again.
If I remember correctly a smaller diameter cylinder will increase the amount of travel needed to compress the cylinders the same amount but I dont think it changes your leverage, just the amount of fluid moving.
Check the rod hole and replace the pads...I use Hawk, you neeed to read up on their pads, theres many for a vette
Last year I replaced my calipers that were leaking and put on new organic pads. It stopped great and was beautiful until I heated up the brakes on a road race course. The next day it felt like I was stepping on a brick and the brakes fely like I had to use a lot of pressure to stop. The pads had hardened and the discs where slightly glazed. I bought a disc brake hone and put on ceramic pads. I only got a short drive but they were very responsive again.
If I remember correctly a smaller diameter cylinder will increase the amount of travel needed to compress the cylinders the same amount but I dont think it changes your leverage, just the amount of fluid moving.
Check the rod hole and replace the pads...I use Hawk, you neeed to read up on their pads, theres many for a vette
Last edited by Rescue Rogers; Jun 6, 2020 at 07:49 AM.
Melting Slicks
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Have you tried different pads, my 6t8 has manuel brakes and uses less foot pressure than my 69 with power brakes. 6T8 has Hawk ferro carbon pads while the 69 has some organic type of pad. T
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I just replaced the rotors with Wilwood drilled and slotted rotors and new Hawk Ceramic pads. Calipers are SS sleeved and are in good condition. I have pulled them apart to inspect them. There is some sludge in the system which is why I want to replace the MC and proportioning valve. I only have about 20 miles on the new pads. Had to park the car when rear toe in shims came out on one side and required servicing..
Melting Slicks
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Had that same problem with the shims, I feel for ya, gotta use that long cotter pin. As far a pedal effort I have to use very light effort on the pedal, same rotors but went with the Wilwood master and their proportioning valve along with stainless braided brake hoses. With the slicks on I could launch passengers if they decide not to wear the seat belts provided. Anyone that either drives or rides in the 6t8 are amazed by the braking and pedal ease. T
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I have the braided flex lines, I could not lock up the brakes when i stood on the pedal... I have dot 5 in it now, I am told it does not woork well with my O ring piston seals. I also may not have done a complete job of purging the old dot 3 out. What fluid do you use ??
Is my vette stock?? HAHA
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the sludde is either water or cross contamination. I drained my system and found the same crap when I bought her 5 years ago. Havent had an issue with the DOT 3 but now everything in it will void the warranty with DOT 5
https://www.cssbinc.com/1965-1982cor...1-1-1-1-1.aspx
https://www.cssbinc.com/1965-1982cor...1-1-1-1-1.aspx
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Ditch the silicone brake fluid and got to a DOT 3 or 4 fluid.
Pads make a HUGE difference.
I went from power to manual brakes, and then the change to Carbotech Autocross pads (front only) made them stronger than power brakes.
Pads make a HUGE difference.
I went from power to manual brakes, and then the change to Carbotech Autocross pads (front only) made them stronger than power brakes.
Melting Slicks
Joined: May 2012
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From: Allenton Wisconsin
Wilwood DOT 4, and if you think those hillbillies from Beverly Hills had found liquid gold you haven't bought any DOT4 from Wilwood. But had decided to run the high temp for the track, brakes do get hot. The Wilwood rotors are the second set of rotors, first set developed heat cracks up front. And then once you finally get your brakes working good you'll find out that the 68 has the small spindle like the 67s and earlier which causes brake pad knock back under hard cornering and braking leaving you with a brake pedal on the floor the next time you go to use them. It's what happens when the spindle flexes causing the rotor to push the pads into the piston, hence when you call on the brakes you need to refill the piston displaced by the flex with fluid prior to any braking action to happen. Only cure is to change to the larger spindles and hubs from a 69 or newer. Ya I know it's a never ending battle ,but with performance you are always finding the next weak link. T
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my 68 is set up for touring and going fast in a straight line so not too concerned about the tortures of road racing. Just want a solid pedal that does not take a gorilla to compress it and a car that stops like a Corvette should
Is my vette stock?? HAHA
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Start with the pads, and check your pedal pushrod....checking is free and you're going to need new pads anyway....no need to bleed cash on a master that may not be your issue......
It just occurred to me, have you bled your brakes manually or with a power bleeder? Your flex hoses may be collapsed internally and you could be getting little to no flow. Bleeding the brakes will tell you the stream pressure at each caliper
It just occurred to me, have you bled your brakes manually or with a power bleeder? Your flex hoses may be collapsed internally and you could be getting little to no flow. Bleeding the brakes will tell you the stream pressure at each caliper
Last edited by Rescue Rogers; Jun 6, 2020 at 09:16 PM.
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When I pulled apart the master, it was all clogged up, rebuild kit half the cost of a new Delco unit fro Rockauto. Rear brakes bled with a good stream but changing hoses anyway. About to pull the front calipers and pull them apart Pads are new Hawk Ceramics
Is my vette stock?? HAHA
Joined: Oct 2015
Posts: 20,174
Likes: 9,298
From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
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Hmmm, my 68 was similar. I had everything correct and it was like stepping on a brick. I just put in power brakes and was done with it....I would check the front flex hoses with a bleed then its decision time.....
After my upgrade the only time I had issues is when the booster failed and again when I overheated the pads
Have you ever had good brakes?
After my upgrade the only time I had issues is when the booster failed and again when I overheated the pads
Have you ever had good brakes?
Last edited by Rescue Rogers; Jun 7, 2020 at 07:21 AM.