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  1. #1
    Join Date
    Apr 2013
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    Country Flag: Canada

    uneven brake wear

    I finally have enough miles on the car that I think I may have found my true brake issue. Long story short is i have LS 4 wheel discs with a home made caliper bracket shown below. I cant remember the thickness i got the bracket cut but i dont think its to thin due to the caliper lining up almost perfect with the rotor. Anyways with enough miles on the car im getting uneven brake wear on the rotor more wear on the outside edge than on the inside edge by the rotor hat, so im not getting full clamping force.

    Is it possible that the caliper bracket is bending or is this a caliper alignment issue? if its a caliper alignment issue do i solve this with an angle finder and have the caliper bracket at true 90 degrees or grease sliders more?



    Im not sure where to go with this.

    thanks

    1970 Chevelle Malibu 350 "70 Hell"
    - UMI - Kore3 - LS1 4 wheel discs - Budnik


  2. #2
    Join Date
    Oct 2004
    Location
    IL/TN
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    751
    Country Flag: United States
    what are the front brakes?
    https://www.pro-touringf-body.com "doing what they say can't be done"

  3. #3
    Join Date
    Apr 2013
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    81
    Country Flag: Canada
    LS1 camaro/trans am brakes
    1970 Chevelle Malibu 350 "70 Hell"
    - UMI - Kore3 - LS1 4 wheel discs - Budnik

  4. #4
    Join Date
    Mar 2005
    Posts
    338
    The caliper is spreading apart. I've seen this on other '98 - '02 f-body brakes. After a while the pad wears in.

    Bob.

  5. #5
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    Apr 2013
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    Country Flag: Canada
    how does pad wear impact/change the caliper spreading?

    just to ensure we are talking about the samething; my pad wear isnt tapered in the rotor rotating direction. It almost seems as though the caliper might not be sitting square on the rotor so when i apply the brakes the caliper pad meets the rotor on the outside edge and thats my clamping force because the rest of the pad isnt touching the rotor.

    The car is in storage right now (winter) so ill try to get a photo of the wear on the rotor.

    Thanks
    1970 Chevelle Malibu 350 "70 Hell"
    - UMI - Kore3 - LS1 4 wheel discs - Budnik

  6. #6
    Join Date
    Mar 2005
    Posts
    338
    The caliper when under braking pressure spreads apart. Eventually this becomes permanent, which causes the top of the pad to meet the outside diameter of the rotor before the inner area of the pad meets the rotor.

    Once the outer edge of the pad wears the pad will then contact the rotor evenly.

    Bob.

  7. #7
    Join Date
    Apr 2013
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    81
    Country Flag: Canada
    should i get new calipers C5 calipers pressure cast in lieu of gravity cast to go with my 12" discs
    1970 Chevelle Malibu 350 "70 Hell"
    - UMI - Kore3 - LS1 4 wheel discs - Budnik

  8. #8
    Join Date
    Apr 2010
    Location
    Jersey Shore
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    625
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    A picture of the pad wear will show if its the caliper spreading or if your bracket is bent. (Likely both pads will have uneven wear if the bracket is bent, usually just the outside pad is worn at the top edge if the caliper is flexed)
    -Chris
    '69 Corvette
    '55 Chevy Hardtop
    AutoWorks Middletown, NJ
    @autoworksnj for corvette and shop car pics
    https://www.pro-touring.com/showthre...e-Build-Thread

  9. #9
    Join Date
    Apr 2013
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    Country Flag: Canada
    Finally some photos.

    So in summary the rotors are being used along the outside circumference (the pad is only contacting the outside edge of the rotor) the pad is not contacting the remaining surface of the rotor. If you run your finger down the rotor you can actually feel your finger rise as you get closer to the rotor hat, meaning this area is not being used.

    This is happening on the drivers and passenger side, see photos: top photo you can see the partial reflection of the rim on the second car in the garage, second photo is pretty clear there's only partial contact.


    I hope someone can guide me in the right direction.
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    1970 Chevelle Malibu 350 "70 Hell"
    - UMI - Kore3 - LS1 4 wheel discs - Budnik

  10. #10
    Join Date
    Apr 2010
    Location
    Jersey Shore
    Posts
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    Country Flag: United States
    What about the other side of the rotor?
    -Chris
    '69 Corvette
    '55 Chevy Hardtop
    AutoWorks Middletown, NJ
    @autoworksnj for corvette and shop car pics
    https://www.pro-touring.com/showthre...e-Build-Thread

  11. #11
    Join Date
    Apr 2013
    Posts
    81
    Country Flag: Canada
    Sorry itís taken so long. I took photos of both sides of the car including spindle, pads, both sides of the rotor and caliper mount with washers installed.

    The first set of 4 photos are the drivers side.

    Thanks
    Attached Images Attached Images                
    1970 Chevelle Malibu 350 "70 Hell"
    - UMI - Kore3 - LS1 4 wheel discs - Budnik

  12. #12
    Join Date
    Aug 2004
    Location
    north central Iowa
    Posts
    504
    Country Flag: United States
    in your pics it looks like the whole pad is being used, so I question if the pad is as wide as the "braking" surface of the rotor? is that portion of the rotor not being used because the pad isn't wide enough?
    72 Nova SS, on the back burner for now.


    current cruiser: "The green machine"

    '70 Impala 4drht, 26K original miles, 2" drop springs and large swaybars, drives pretty good for a land yahct in the middle of an ls1 swap, but thinking about changing directions to a duramax diesel swap.

  13. #13
    Join Date
    Apr 2013
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    81
    Country Flag: Canada
    Quote Originally Posted by justanova View Post
    in your pics it looks like the whole pad is being used, so I question if the pad is as wide as the "braking" surface of the rotor? is that portion of the rotor not being used because the pad isn't wide enough?
    Good point. You are correct the full pad appears to be being used and I would agree based on the fact that the ďrustĒ ring is limited to the area that doesnít get swept by the caliper.

    But my car does not brake like a 4 wheel disc car should. The rotors are 12Ē 2003 impala rotors with 2000 camaro calipers. I emailed tobin many times and read many threads on this swap that this was the ďgo toĒ route.

    I am happy to try other combinations that work to get this car to stop but thereís something wrong and the un even wear is maybe the issue. Even if the pad is contacting the rotor perhaps only part of it is 80% full contact 20% half contact or something?
    1970 Chevelle Malibu 350 "70 Hell"
    - UMI - Kore3 - LS1 4 wheel discs - Budnik

  14. #14
    Join Date
    Oct 2011
    Posts
    278
    Seems like the caliper should sit slightly lower. Is it possible the caliper brackets need to be swapped from passenger to driver and driver to passenger? Or maybe whoever machined the brackets machined them wrong? Or the caliper bracket dimensions are just wrong?

  15. #15
    Join Date
    Apr 2013
    Posts
    81
    Country Flag: Canada
    Quote Originally Posted by joeko23 View Post
    Seems like the caliper should sit slightly lower. Is it possible the caliper brackets need to be swapped from passenger to driver and driver to passenger? Or maybe whoever machined the brackets machined them wrong? Or the caliper bracket dimensions are just wrong?
    Brackets are built as per sketch, they are the same left to right.

    If the caliper brackets are built wrong wouldnít there be more guys on the forums having the same issue? Before I went this route everyone and their dog was doing the Ls F body brake swap on first gens camaros and GM A Bodyís?

    If the caliper sat further down how would this change the braking pressure? When the pistons close in all it needs is full contact on the rotor (no overhang to high)?

    Or am I wrong?
    1970 Chevelle Malibu 350 "70 Hell"
    - UMI - Kore3 - LS1 4 wheel discs - Budnik

  16. #16
    Join Date
    May 2014
    Location
    Louisville, KY
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    23
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    Do you have some pics showing the edge profile of the pads and discs? Are they flat or angled?

    Are you not getting the stopping performance that you think it should have? What master cylinder bore size are you running?

  17. #17
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    Apr 2013
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    Quote Originally Posted by grease View Post
    Do you have some pics showing the edge profile of the pads and discs? Are they flat or angled?

    Are you not getting the stopping performance that you think it should have? What master cylinder bore size are you running?
    I looked at the pads when I took it apart the other night, no taper or angle; note that I only have about 600 miles on the set up.

    Under basic braking needs car stops but if I have to do an emergency stop it struggles I have to give it everything I got. 1Ē bore master itís been bleed to death, nice strong good feeling pedal, The booster is in the power brake hole in the brake pedal arm, went through 3 bad masters, new booster, adjustable proportion valve in the rear line, again Iíve done the exact same thing that all you guys do to swap in LS brakes or C5 brakes the only difference is C5 runs 13Ē discs and I have F body 12Ē discs.

    also if I try to do a brake stand the car pushes through the brakes front brakes wonít hold the car back.

    So as stated above after some 600 miles I have noticed the inconsistent sweep pattern and this must be why Iím not getting full clamping force at the front.
    1970 Chevelle Malibu 350 "70 Hell"
    - UMI - Kore3 - LS1 4 wheel discs - Budnik

  18. #18
    Join Date
    Apr 2013
    Posts
    81
    Country Flag: Canada
    Here’s more background for y’all:

    - Factory 4 wheel power drum car.
    - Drum spindle cut down to a disc spindle car.
    - caliper bracket laser cut as per sketch that was found in other threads
    - 2000 camaro front and rear calipers
    - front 12” 2003 impala rotors (same diameter as camaro but fits within hub (camaro does not)
    - factory steel lines with kore3 stainless horse
    - adjustable valve in the rear circuit
    - manual bleed and power bleed for months
    - nice firm pedal
    - brakes engage about half way down pedal travel (too much travel in my opinion, disc brake car should start to stop at the quarter way down pedal travel).
    - brakes don’t squeak or grind
    - no binding on rotor with caliper and pads installed.

    That’s pretty much it in a nut shell.

    Thanks

    -
    1970 Chevelle Malibu 350 "70 Hell"
    - UMI - Kore3 - LS1 4 wheel discs - Budnik

  19. #19
    Join Date
    May 2014
    Location
    Louisville, KY
    Posts
    23
    Country Flag: United States
    How much vacuum do you have at idle? Do you have a big lopey cam with low manifold vacuum? That could cause increased pedal effort and poor brake performance?

  20. #20
    Join Date
    Apr 2013
    Posts
    81
    Country Flag: Canada
    Quote Originally Posted by grease View Post
    How much vacuum do you have at idle? Do you have a big lopey cam with low manifold vacuum? That could cause increased pedal effort and poor brake performance?
    Not sure on the vacuum but I donít have a large cam. I donít have increased pedal effort (low vacuum) I have increased pedal travel.

    A normal 4 wheel disc car should start to stop as soon as some weight is put on the pedal letís call it 1/4 travel down. For me to get any brake I need to be 1/2 travel down.

    I definitely have vacuum assist thatís not the problem, pedal feels like my new truck, I just donít have the clamping force on the rotors on the front.

    The rears donít have that half ďpolished/wornĒ rotor look like the front do.
    1970 Chevelle Malibu 350 "70 Hell"
    - UMI - Kore3 - LS1 4 wheel discs - Budnik

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