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Moses

What brake lines do you recommend using on a 1967 jeep cj5 now that I have replaced the drum brakes with disc on front and back?

 

Thanks

 Kyle

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Brake lines are not so much an issue as the Master Cylinder. Certainly you need to upgrade to a M/C sized for the disks. A later year CJ that came with the disk brakes would probably be fine.

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Kyle...Rinky Dink has a good point.  You need a master cylinder that can displace enough fluid for the disc brake caliper pistons.  With some calipers, the master cylinder may need more reservoir capacity, too.

Drum brake master cylinders (like your '67 Jeep CJ type) use residual valves to keep brake line fluid under a constant low pressure when the pedal releases.  This pressure is lower than the spring tension on the brake shoes and just enough to keep the  cup lips in the wheel cylinders expanded.  Be aware that most master cylinders for disc brakes do not hold residual pressure in the brake lines.  (Exception: Very late model vehicle master cylinders for disc brakes do use slight residual pressure on the disc brake lines.)

Caution:  A drum brake master cylinder with the drum brake residual valves in place will create disc brake pad drag, rotor heat-up and premature brake wear.  Too much residual pressure and heat expansion of parts could lock up a wheel(s) in the worse case scenario.

Later Jeep CJ disc/drum brake master cylinders (late 1970s to 1986) do not have a residual valve on the port leading to the disc front brakes.  These CJ disc/drum master cylinders do have a residual valve on the drum rear brake port of the master cylinder...You would need to remove that residual valve beneath the brake line port at the master cylinder.

On my disc brake conversions, I have used either a master cylinder intended for disc brakes, or I have removed the residual valves from the port(s) that feed to the disc brakes.  On Jeep/Bendix master cylinders, these residual valves are behind the brake line flare seats at the master cylinder fluid ports. 

Since you have disc brakes front and rear, you would need to use a master cylinder designed for four-wheel disc brakes or a disc brake master cylinder like Rinky Dink suggests (Jeep CJ disc/drum application) with the residual valve removed from the rear (originally drum) brakes port.  That way, both ports will be for disc brakes. 

As for brake pipe sizing, the OEM pipe will likely work fine.  Is the current pipe 3/16" diameter?  If so, that should work.  1/4" would be the optional choice.  If you change to a later master cylinder, the rear brakes port might be a different sizing than the front brakes port.  You would need to change line and fitting size in that case.  The more significant concern, though, is removal of the residual valve on drum brake ports.

Note:  Use only brake rated fittings for any brake plumbing chores.  Do not use generic or non-brake grade fittings!

Here is some additional discussion, Kyle.  60Bubba and I discuss his later CJ-7 brake upgrades and the residual valve issue:  

This should help make your Jeep safer...

Moses

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There are several 1970's vintage Corvette master cylinders that are disc/disc and will bolt up to a stock CJ booster.  Measure the outlet sizes of your current MC to find one that matches a Corvette option, or be prepared to replace the fittings on your brake lines with ones that match the new MC.

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Kyle cj5...60Bubba's comments and 53HiHood's link for The Jeep Guy address your project.  Worth reviewing, you need to confirm the master cylinder mounting arrangement for your '67 Kaiser Era Jeep CJ-5.  Boosters are a popular upgrade with disc brakes, review the exchange with 60Bubba for details and installation concerns.  On a lightweight 1955 CJ-5 Jeep, I ran four-wheel disc brakes without a booster.  Your call.

Thanks for adding this information for Kyle's project, 60Bubba and 53HiHood!

Moses

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