Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

more disk problems

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by misfit, Jan 20, 2001.

  1. misfit

    misfit 1/2 ton status

    Joined:
    Jul 21, 2000
    Posts:
    324
    Likes Received:
    0
    Location:
    south central wa state
    just called a couple brake shops. a new 76-78 caddy eldo rotor measures 1.200. and it should be turned no more than 1.185
    i just put a tape measure across my new gm rotor(a 76) and it measures over 1.25! what the heck should i do? of course i could always take the rotors and turn them myself, but id like the least hassle. Shawn, suggestions? anyone?
     
  2. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

    Joined:
    Feb 17, 2000
    Posts:
    7,385
    Likes Received:
    0
    Location:
    Atlanta
    Not sure I see an Issue. All that means is the thickness of the rotor. The caliper fits over the rotor. Worse case I see is once you put the pads in it may be tight. If it spins with some light drag thats fine but if it won't spin may need to have a couple 1/1000 removed. If that happens take the pads to a machine shop and have them grind the pads down some till it fits. Takes some life off the pads but would be the simple fix. Just make sure you take good mesurments...may want to take a caliper and a disc with you and show the shop the issue and let them measure how much you need removed.

    [​IMG]

    Diging it in the dirt with my K5's
    Grim-Reaper
    <A target="_blank" HREF=http://grimsk5s.coloradok5.com/>http://grimsk5s.coloradok5.com/</A>
     
  3. pcorssmit

    pcorssmit 1/2 ton status

    Joined:
    Jan 2, 2001
    Posts:
    1,346
    Likes Received:
    0
    Location:
    Denver, CO
    If you are still running 1/2 or 3/4 ton brakes on the front, and the pads are slightly worn, you could swap the front and rear pads. The rear pads wear a lot less than the fronts, and will most likely still outlast them.

    Pete

    '83 K5, 350 TBI (ex 6.2), Dana 60/14 bolt, Detroits, 3" lift, 15-39.5x15 TSLs
    '97 Dodge 2500 4x4 CC LB Sport, Cummins 5 spd
     
  4. Shawn

    Shawn 1/2 ton status Premium Member Author

    Joined:
    Feb 17, 2000
    Posts:
    1,753
    Likes Received:
    5
    Location:
    5280'
    My Ford F250 rotors on my rear 14FF with the older TSM kit measure 1.25 and the 76-78 calipers I purchased from Checkers fit with no problems and I even had to turn the ebrake arm a little to make them snug (with new Caddy brake pads). Your rotors should be fine with the 76-78 calipers.

    Shawn
    87 K5
    few mods[​IMG]
    <A target="_blank" HREF=http://www.off-road.com/chevy>http://www.off-road.com/chevy</A>
     
  5. 1990K5

    1990K5 1/2 ton status

    Joined:
    Nov 6, 2000
    Posts:
    460
    Likes Received:
    0
    Location:
    LITTLETON CO.
    just did the swap a week ago i used 79 seville calipers w/brand new pads and 1991 1" thick chevy 1/2ton 4x4 rotors (brand new also). scott at rockstomper made custom brackets for me. i also had to reset the piston all the way back flush w/ the caliper to get them over the rotor and then ratchet the e-brakes to snug the pads against the rotor. after i ditched the stock abs setup everything works great. if you have anything older than a 1990 you will probably have to drill out the factory proportioning valve. i did this swap for only $200 let me know if you have any questions J.C. e-mail me at: MOTOLOCO@AOL.COM
     
  6. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

    Joined:
    Feb 17, 2000
    Posts:
    7,385
    Likes Received:
    0
    Location:
    Atlanta
    Why do you need to drill out the proportioning valve? Yes I'm interested in more details.


    Diging it in the dirt with my K5's
    Grim-Reaper
    <A target="_blank" HREF=http://grimsk5s.coloradok5.com/>http://grimsk5s.coloradok5.com/</A>
     
  7. HarryH3

    HarryH3 1 ton status Author

    Joined:
    May 31, 2000
    Posts:
    10,384
    Likes Received:
    2
    Location:
    Georgetown, TX
    You don't want to use front pads on the rear. You must use the Caddy Eldorado pads. They have a pin on the back of the inner pad that engages a slot on the caliper piston. The pin keeps the piston from rotating when the parking brake is engaged. There's a jackscrew inside the piston assembly that turns as the parking brake lever moves.

    <font color=black>HarryH3 - '75 K5</font color=black>
    <A target="_blank" HREF=http://ThunderTruck.ColoradoK5.com>http://ThunderTruck.ColoradoK5.com</A>
     
  8. 1990K5

    1990K5 1/2 ton status

    Joined:
    Nov 6, 2000
    Posts:
    460
    Likes Received:
    0
    Location:
    LITTLETON CO.
    the factory proportioning valve limits flow to the rear -a lot-, and drums take less fluid than calipers. obviously that combination won't work, so you need to drill out the the factory valve to the reg. line dia. the valve is usually located on the front cross member of the frame, you will know your in the right area when you pull the line out of the "T" block and look inside and see a pin size hole for the rear line. oh ya, also you can't use anything other than the caddy rear pads like that other fella said.
     
  9. Shawn

    Shawn 1/2 ton status Premium Member Author

    Joined:
    Feb 17, 2000
    Posts:
    1,753
    Likes Received:
    5
    Location:
    5280'
    My 87 K5 proportioning valve (at the front) is stock and I never had to do anything to it. TSM actually suggests using a an adjustable proportioning valve at the rear line only to decrease the pressure since the rear disks will usually grab much more than drums. Mine stops great with the disks in the rear and no modification to the stock proportioning valve (at front) was done. If you drill the stock proportioning valve, your rears will lock up before the front which is not a good thing at high speeds. Isn't the proportioning on all vehicles suppose to be 80% front, 20% rear?



    Shawn
    87 K5
    few mods[​IMG]
    <A target="_blank" HREF=http://www.off-road.com/chevy>http://www.off-road.com/chevy</A>
     
  10. 1990K5

    1990K5 1/2 ton status

    Joined:
    Nov 6, 2000
    Posts:
    460
    Likes Received:
    0
    Location:
    LITTLETON CO.
    yes the rear will stop better w/the same amount of pressure to the calipers but you need a lot more flow w/the calipers than you do the drums to get that same pressure (the piston in the caliper is way bigger than the one in the drum). yes you are correct, in most vehichles you need a proportioning valve to adj. the rear flow but you still have to drill out(or bypass) the factory valve to get full flow to the new ajd. valve so you have full range of adjustability. on my 1990 i could'nt even get the rears to lock up on ice when i stood on the pedal!!! now i by passed the factory valve by reflareing the lines and running them direct!! into the master cylinder and getting completely rid of the block below it. now this bitch stops. the master cylinder already limits rear flow slightly. as the rears seat in i might have to put in an in -line proportioning valve. anyway this is my experience, i fought it for a while but it works great now, but every vehichle is different.
     
  11. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

    Joined:
    Feb 17, 2000
    Posts:
    7,385
    Likes Received:
    0
    Location:
    Atlanta
    Ahhh the light bulb has come on above my head. Really the best thing to do is just remove the favtory valve and seperate the front and rear systems. Then put the adjustable valve on it.
    As for Shawn feeling the Drums work less. Actully Dums are self activating. Thats why it uses such small pistons. once the pads hit the drum they get pulled into it. There is also much more lining surface. The reason for the big springs is to decativate the brakes. If they didn't have the spring they would lock on.
    The problem comes in that they are hard to ballance and the self adjusters are prone to problems. Disc also self clean much better.
    Ok now I'm sold on the Disc but as usual I'm a cheap skate. Has anyone done a home brew on a 12 bolt? My though is I can make it pretty cheap. For those that have done a home brew is it better to put the disk in from the back like the front hubs or put it on the outside like the drums seat? Any issues with too little surface for the rim to seat against ( front disc's have a much larger hole in the center)? What about using stock calipers and a line lock and not messing with the parking brake? Ok one more and I'll shut up...On the new trucks I think the parking brake is actully a drum inside the disc just like my Supra rear set up is. Anybody tried using that set up on the 12 bolt?

    Diging it in the dirt with my K5's
    Grim-Reaper
    <A target="_blank" HREF=http://grimsk5s.coloradok5.com/>http://grimsk5s.coloradok5.com/</A>
     
  12. Cmoe

    Cmoe 1/2 ton status

    Joined:
    Feb 19, 2000
    Posts:
    2,884
    Likes Received:
    0
    Location:
    Mesa,AZ
    I'm with you Grim-Reaper...... I'm a cheap skate too, until I want something bad enough. Has anyone had any problem with the disk conversions that haven't been talked about already. What + and - have you found since your conversion? G.R. If you hear anything please let me know about the rear disc and mini drum for a P-brake.

    C'moe

    <font color=black>the blazer is "Back in Black"
     
  13. 1990K5

    1990K5 1/2 ton status

    Joined:
    Nov 6, 2000
    Posts:
    460
    Likes Received:
    0
    Location:
    LITTLETON CO.
    dynatrack and companies like that do the drum-in-disc thing but there is no way to do that on a budget. i did mine on my 12bolt for just under $200 total. you need to machine out the center of the rotors so they fit over the axle center then just slip them on from the outside, there is plenty of stud left. you can use more trouble free calipers w/out e-brakes off of 77-83 monty carlo,regal,or s-10, just make sure they are '83 or older. newer than that had "low drag" style calipers that take too much fluid to activate. but i got my e-brake working fine, how long that will last is another question!
     

Share This Page