Low drag caliper question

Discussion in 'Suspension, Steering, Brake & Wheel Topics' started by Gasoholic, Jan 16, 2021.

  1. Gasoholic

    Gasoholic Veteran Member

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    I acquired this rear brake drum to disc conversion kit for my 78 gen 2 10 bolt.
    I've installed the D52 kit from Wilwood on the fronts. I'm thinking about putting this kit on the rears if it will work.
    No problems with fit, I did a mock up and everything is pretty self explanatory. Just that I'm trying to figure out what kind of master cylinder I need to go with this.
    I believe these calipers may be the low drag type that require a step down type master cylinder.
    I dont know much about this kit. I got it with some rear end stuff I bought from one of the good members I met here. Like I said it does fit. Pretty much I have no money into it so I'm not opposed to doing some thing different.
    Also might mention I'm converting over to manual brakes.

    Any advice?

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  2. Rene Melten

    Rene Melten Veteran Member Lifetime Gold Member

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    I used a 1980 Corvette master cylinder, Raybestos MC #39052, same as the AC Delco #18030333.
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  3. Gasoholic

    Gasoholic Veteran Member

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    So the Vette M/C would be a step down type M/C. From what I've read its not a good idea to use a step down type M/C for a manual braking system.

    Appears my Wilwood front calipers are ok to use. Its the kit I acquired for the rears that is suspect.
    From my research the conversion kit calipers are for an S-10. The fact that they have metric fittings tells me they were indeed assembled during the time frame that GM was using the "low drag" type calipers.
    The seals are what make them "low drag" type. The housings are the same regardless. And rebuilt calipers are rebuilt using regular seals. Only brand new calipers have the beveled seals.
    Soooo....
    If what I have read is true then these calipers if they are brand new are most likely low drag type calipers. If however they are rebuilds then they are more than likely not assembled with the low drag type seals and would be ok to use.
    So how does a person know?
    IDK. Short of disassembling them and rebuilding with new seals. Then I would for sure know. Seems simple enough. Just pop them apart and put new seals in them.
    Not sure thats what I'm going to do yet.
    I may just buy the master cylinder manual conversion kit and see what happens. If it doesn't work it wont be the first time I've been down this road. I'll make it work one way or another :)
     
  4. Jodi

    Jodi Veteran Member

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    You could try putting a block of wood between the caliper housing and piston, then applied air pressure to move the piston out.
    Release the air and measure how far the piston retracts into the housing. I believe the low drag calipers retracts a little bit more than the regular calipers due to the beveled seal and is also the reason why a step bore MC is required.
     
  5. Gasoholic

    Gasoholic Veteran Member

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  6. kenny77

    kenny77 Veteran Member Lifetime Gold Member

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    Pretty sure that's just their version of a stock style MC. Low Drag Calipers are NOT anything special. The ONLY difference is the seal. Change it to a regular one, put it back together and Happy Motoring. My brother and I freaked out with this same question when he somehow got shipped Low Drag Calipers for the FRONT of his 76 LT.
     
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