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So I installed my dics brakes today... Not impressed with the stopping..

Discussion in 'The Garage' started by white-rhyno, Apr 11, 2003.

  1. white-rhyno

    white-rhyno 1/2 ton status

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    I am really starting to think I missed something. My k5 dosent stop near as good with disc's as it did with my drums. When I REALLY mash on the brake peddle it will lock up my rears. Maby I just expected a little more. Also my peddle is realy soft. Almost goes to the floor. I am positive I got all the air out.
    Guys gimme a little advice??
    Brad
    PS JKW makes great stuff. Also mike (Borregok5), sorry i didnt get any pics. My digi cam that takes the floppy discs, wont let me recieve the pics off the disc. Says the disc is currupt?
     
  2. mountainexplorer

    mountainexplorer 1/2 ton status

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    I've heard from a few people that you need to change the proportioning valve. However, I went to rear discs on my GMC, and it stops excellent. Nothing locks up, and the pedal is very easy to push but also very responsive and stays up top.

    One guy said it was because the Dana 60 up front in my truck has greater breaking than a Dana 44 or 10 bolt, and with the lesser breaking power of a 44 or 10 bolt, the rear is prone to lock up with the stock proportioning valve. If that even makes sense the way I wrote it.
     
  3. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    Have the system power-bled somewhere. From past posts, it seems like people flushed forever and still had a soft pedal, and no signs of air, but after a power bleed, the pedal went hard and braking was much better. I think Steve Fox was one of those people....
     
  4. outlaw612

    outlaw612 1/2 ton status

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    I agree with Leadfoot, have it power bled. I didnt have to mes with the proportioning valve, but I did decide to go to a 1 ton MC. It made a big difference.
     
  5. mastercraftkpk

    mastercraftkpk 1/2 ton status

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    Definitely get your brake system "flushed out".. When you start monkeying around w/ brake systems that are over 15 years old, you can break loose all sorts of dirt & sludge in the system that will clog up everything.

    /forums/images/graemlins/usaflag.gif /forums/images/graemlins/k5.gif
     
  6. HarryH3

    HarryH3 1 ton status Author

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    The low pedal just screams "air in the lines" or you're using Caddy calipers and haven't taken the slack out of the parking brake mechanism in the calipers. Either or both will cause the symptoms that you're seeing.
     
  7. BOWTIE

    BOWTIE 1/2 ton status

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    i just recently installed a disk conversion on my nephew's K5 and had the same problems that you discribed. after bleeding the brakes for hours we just couldn't get the system to work right, so he went ahead and took his K5 the have it power bled and that took care of the problems.

    another thing, as mentioned above, he also has a front 60 and has no problems with the rears locking up before the fronts.
     
  8. white-rhyno

    white-rhyno 1/2 ton status

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    Thanks for the advice guys. Ill try getting it powerbled tonight. We have one at work but my boss will have to show me how to use it. Good chance to learn. Im wondering if the 1ton MC will make any differnce. There not to horribly expensive. Oh I used the chevy calipers, not the caddy ones.
     
  9. bablazer73

    bablazer73 1/2 ton status

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    I have mentioned this to several people. Part of the problemis that the master cylinder is NOT designed to move the required amount of fluid to properly apply the rear calipers. You need to use a master cylinder that is designed to work with four wheel disc. This will improve braking power.
     
  10. Lance

    Lance 1/2 ton status

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    Along the lines of what bablazer73 said, I used a MC from a '78 corvette w/ 4-wheel discs. Bolted right up to my booster just had to get some adapters for the brake line to MC. Had it power bled after I was done, so I don't which helped and which didn't or if it was a combination of both. Stopped like a champ both times I got to drive it after that.
     
  11. BorregoK5

    BorregoK5 1/2 ton status

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    Good to hear you got it installed. I'm using my stock half ton Master Cyl with absolutely no problems, D60/14bolt combo. It was however difficult to get the air bubbles out at first, as would be with any major change in any system. Check the orientation of the bleeder screw as well. Many people run their calipers upside down or at angles for various reasons but if the bleeder is not at the top, you may have trouble getting the air out. Major changes to the system can sometimes place the master cylender plunger into areas it hasn't travelled in a while which can damage seals causing sudden problems which didn't exist before you began so keep that in mind if you cant seem to correct it.

    On a side note, gravity bleeding seems to work very well on the K5, better than the 2 man pump method.
     
  12. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Re: So I installed my dics brakes today... Not impressed with the stopping.

    Mine did the same thing. Put a few miles on them and see what it does. Peddled was spongy for a while. Now it's awsome!
    did you put an adjustable prop valve in there and disable the factory prop valve?
     
  13. white-rhyno

    white-rhyno 1/2 ton status

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    well I did a little research today, a half ton MC has an inch and 1/8th bore, where as a one ton dually has an inch and 5/16ths bore. so theroretically the one ton MC would move a higher volume of fluid with less pressure. So I don't know if a one ton MC would help all that much. I think I am going to go with the 78 corvette MC. If I were to put an adjustable proportioning valve, How would I plumb it in?
     
  14. ntsqd

    ntsqd 1/2 ton status

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    Re: So I installed my dics brakes today... Not impressed with the stopping.

    Stock there's a thing called the "Combination Valve", it has both a fixed proportioning valve in it and the shuttle valve that turns on the light in the event of one half of the system failing. You can put the adjustable P-valve anywhere in the rear system downstream from the shuttle valve (if you want the light to continue working) or replace the combo valve with the adjustable (if you don't care about the light).

    I'd do the power bleed/system flush first.
     
  15. white-rhyno

    white-rhyno 1/2 ton status

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    Wouldn't putting a P-valve on my rear brakes restrict the flow? Right know I can barely get them to lock up. Ill try the power bleed first. It is the cheapest. Can any of you guys with 38's or bigger lock up all four on pavement? I've never been able to lock em all up with 35's..... Can I try bypassing the stock P-valve for my rear brakes??? I would imagin that id have to plug the P-valve.
     
  16. SCOTTS_4X

    SCOTTS_4X 1/2 ton status

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    Re: So I installed my dics brakes today... Not impressed with the stopping.

    hell I can lock all 4 up on my truck with a 3/4 ton 10blt and a 3/4 ton dana60 from a early 70's chevy, and it still has the stock drum brakes on it with worn shoes. pedal is spungy, always has been, but I can still lock them up from about 25-30. btw, how much is it costing to get the system power-flushed? I might look into this to get rid of some of the sponge in my pedal.

    -Scott
     
  17. white-rhyno

    white-rhyno 1/2 ton status

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    Wish i could lock up all four, its not costing me anything to get it power bled. I work at a shop. My boss is really cool. I hardly pay for any thing, oils, anitfreeze, ect. Perks of the job I guess.
     
  18. BorregoK5

    BorregoK5 1/2 ton status

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    Yes, locking the 38's is relatively easy, especially with hydraboost braking. Not always a good thing though, cause big tires can get a bounce going when they are locked up. I went hydraboost while trying to figure out why my braking was so poor when the truck was on 33's, vacuum booster and 1/2 ton axles. The hydrabooster made the stock setup very responsive. I didn't add the disks until the one ton swap and it only improved the overall braking across the board.
     
  19. Beast388

    Beast388 1/2 ton status

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    Just for general info, how much did you guys pay to have your system power-bled? Can most local shops do it?(like Midas)
     
  20. jekbrown

    jekbrown I am CK5 Premium Member GMOTM Winner Author

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    where do you guys get your junk power bled? I went to a couple of brake places... both said theyd do it after a "full inspection... and if nothing else is messed up, it'll be $50". ehhhh, no thanks. /forums/images/graemlins/frown.gif talk about the oldest trick in the book. guarenteed after that "full inspection" theyd "find" $500 worth of work to do... even though pretty much all my brake stuff is brand new...

    j
     

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