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Thread: Viper Brake / Big Brake Mediocre Performance

  1. #1

    Default Viper Brake / Big Brake Mediocre Performance

    After a couple pages of math and learning about braking systems and how they actually work I think I found a solution for guys with big brakes. Richard figured out that the 99-04 booster has 47% more surface area in the dual diaphragm booster. Dodge for some reason up sized the master to a bigger bore. That yields more volume but less pressure. Most guys who I have talked to with big brakes who are honest with themselves are not really impressed, somewhat stiff pedal and marginally better braking.

    After doing the calculations based on caliper piston size the master cylinder/booster setup is mismatched terribly for bigger brakes. While they might work it isn't working correctly.

    The guy at wilwood was nice enough to spend some time with me on the phone and he was even going in circles for a minute. But he recommended a 7/8 bore master with manual braking master and a 1" with the given surface area of the 2000 booster.

    Another consideration is our approximately 3.5:1 pedal ratio.

    I have changed some things out on my setup and will update this thread good or bad.


    "The journey is more fun than the destination"

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    niebs's Avatar
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    Are you switching to manual brakes?

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    Sick 660r's Avatar
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    Quote Originally Posted by niebs View Post
    Are you switching to manual brakes?
    Like lol


    Quote Originally Posted by BluRT00 View Post
    Part your red sport out and buy a gen 2. Problem solved.

  4. #4

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    Quote Originally Posted by niebs View Post
    Are you switching to manual brakes?
    Nope! No desire to ditch any of the stock braking systems. Will play with master cylinder bore size first. Then maybe investigate the metering valve and proportioning valve setup. But doing one change at a time to seem what helps/doesnt.


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    Guys aren't happy with their pedal feel on bigger brakes? Mine are about the same as the pedal feel of the hydroboost in my Cummins.

    I swapped to the 03/04 master which is exactly the same as what's in viper. Rock auto even lists them as the same part. But I did keep my original larger diameter booster. May consider switching to the newer booster but I'm happy enough as-is that I'm just not motivated enough.

    But with the myriad of swaps out there, and the variety of calipers out there with vastly different piston sizes and quantities, it's not surprising there are mis-matched combos that could use a different master size bore.

    Is that where you're headed? A custom master for big brake swaps?
    --Tom
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    Quote Originally Posted by Filthy Filbert View Post
    Guys aren't happy with their pedal feel on bigger brakes? Mine are about the same as the pedal feel of the hydroboost in my Cummins.

    I swapped to the 03/04 master which is exactly the same as what's in viper. Rock auto even lists them as the same part. But I did keep my original larger diameter booster. May consider switching to the newer booster but I'm happy enough as-is that I'm just not motivated enough.

    But with the myriad of swaps out there, and the variety of calipers out there with vastly different piston sizes and quantities, it's not surprising there are mis-matched combos that could use a different master size bore.

    Is that where you're headed? A custom master for big brake swaps?
    Well Chris Baxter isnt happy with his. Mine was just meh. Josh Klein did Mike Carlmans setup and he said it was the same as mine. Joe Monar ended up going manual brakes cause he was unhappy with the Viper setup. The bottom line is the bigger master cylinder bore of the 99-up (1.125) provides more volume but less pressure. It was designed for a couple pistons and some drums. Now there is 4 big pistons in front and 1 in the back X 2. There simply isnt enough pressure to fully apply the pistons, sure it stops the truck fine but not anything like "holy shit". My pedal was not high or hard (fag comments welcome) but just stiff. The pistons seem to be fighting back against brake pedal input. Now with more pedal ratio you may be able to aleviate lots of that. However I am not willing to or want to try to modify my pedal for more ratio. So it makes sense, especially after doing all the math that a small master bore may be the ticket especially with the dual diaphram 99-up booster.

    I have no desire to make a custom master cylinder setup to sell 2 of them


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    I may be wrong but the 03-04 master was different, and intended for a 4 wheel disc set up.

    When matching bore size remember that the earlier trucks had a single piston around 70mm? In diameter. The viper has 2, that are like 36mm and 38mm. (You ignore half of them because they are opposing and push back on each other.
    --Tom
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    Quote Originally Posted by Filthy Filbert View Post
    I may be wrong but the 03-04 master was different, and intended for a 4 wheel disc set up.

    When matching bore size remember that the earlier trucks had a single piston around 70mm? In diameter. The viper has 2, that are like 36mm and 38mm. (You ignore half of them because they are opposing and push back on each other.
    The viper is 40 and 38 on this generation. And actually the 03-04 master was 15/16" on the same booster. The 03/04 master has a level sensor as well. The combo valve is different. Lots of changes. I think the master itself would bolt up but I wanted to try a 1" bore first. Ironically the 98 R/T is a 1" bore. The 99-02 were 1.125 as I guess the felt they needed the volume to activate the drums vs the pressure to actuate more pistons. They also may have been compensating for a nearly 50% stronger booster than in the 97-98 trucks.

    And yes I am aware that you only calculate 2 of the pistons on a 4 piston setup.


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    Sick 660r's Avatar
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    Yeah I was never impressed with the stock pedal/booster setup with viper calipers. I thought it was due to lack of vacuum but with the vacuum pump pulling 18" I still couldn't get abs to kick in while literally standing on the brakes. I'm happy with 15/16" with 7.1:1 pedal ratio. I will admit that I'm curious how 7/8" would feel.


    Quote Originally Posted by BluRT00 View Post
    Part your red sport out and buy a gen 2. Problem solved.

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    one thing that really needs to be factored in and many people never consider it, is pad material. it can make a massive difference in braking effort and action. it can be used as the final tuning feel assuming there are choices. going smaller on the mc bore is going to help increase the amount of modulation available which is "feel" and pedal travel. most of us older vehicle drivers seem to want a good amount of travel. this will increase until you get to the point that you do not have enough displacement. what that point is will vary in each custom brake system. it seems that the 15/16" and 7/8" bores are a common end result in general regardless of manual vs power or pedal ratio.
    One B body build i'm doing has 13" rotors all around. the calipers are identical bores to a late 90's cobra mustang so i'm starting with a dakota mc with 15/16" bore (same bore as the mustang) with stock pedal ratio and a booster ( i don't have full specs on ratio or booster). We'll see how it feels and functions and adjust from there.
    1941 Dodge 1/2 ton, 493 twin turbo, EFI, 727, 4 wheel disc brakes, custom triangulated 4 link, DANA 60, Gleason Torsen diff,

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    Quote Originally Posted by Sick 660r View Post
    Yeah I was never impressed with the stock pedal/booster setup with viper calipers. I thought it was due to lack of vacuum but with the vacuum pump pulling 18" I still couldn't get abs to kick in while literally standing on the brakes. I'm happy with 15/16" with 7.1:1 pedal ratio. I will admit that I'm curious how 7/8" would feel.

    Didn't realize guys were having these issues. I can feel my RWAL cycling in if I'm aggressively downshifting and braking.

    If I had a stiff pedal and felt like I was leaving line pressure on the table and not maximizing my brakes, the first 2 things I would do is more booster and a smaller master, paying attention that my master has enough stroke to deliver the needed volume.

    Pad material as mentioned is crucial too. It sounds sexy to say you have high performance race pads but most race pads don't really bite until they have heat into them. Not what you want for street driving where you need to stop short with cold brakes when a deer suddenly jumps out infront of you.
    --Tom
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  13. #13

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    Pads is not the issue. I am running hawk hps pads which the viper guys seem to like for a street application. I have now PROPERLY bled rear calipers by unbolting them and sliding them back on rotor so the bleeders are facing up. Changed the to a smaller bore mc. After I bleed fronts I can report back and see if this was a step forward or not.


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    I eagerly await your results.

    My rear calipers also have to come off to be bled, but that's because I couldn't remove the cross over tubes without striping and tearing stuff up so I left them instead of switching the bleeders to the top. May do an exchange at some point on rebuilt calipers and flip bleeders then.


    If you had air in your rear calipers before, you just made your pedal harder
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    Sick 660r's Avatar
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    I think he will see a big improvement. A 1/4" reduction in bore size will definitely be noticeable.


    Quote Originally Posted by BluRT00 View Post
    Part your red sport out and buy a gen 2. Problem solved.

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    Rock Auto shows a 15/16 master on everything but 97-98 Dakotas--those are 1". Are the replacement masters smaller than OEM?
    --Tom
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    Quote Originally Posted by Filthy Filbert View Post
    Rock Auto shows a 15/16 master on everything but 97-98 Dakotas--those are 1". Are the replacement masters smaller than OEM?
    My basic theory was this. Brand new masters were nearly always quoted as accurate. Remans wtf knows. I do know people have disassembled all years and the 99-02 with drum brakes was 1.125 97-98 was 1" pre 97 15/16" and not 100% on 03-04 but going to trust the new mc specs from Napa and say 15/16" as well.


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    So I bled everything and took it around the block. Pedal feels better but sort of gives up at the bottom. It stops fine and feels like it wants to stop harder just gives up at the floor. Perhaps I have so air but I bled the shit out of it. Still possible I guess. Maybe I will drive it and get some miles on it and bleed one more time.


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    air would be soft and mushy at the top of the pedal stroke, not the bottom. almost sounds like you're running out of pedal stroke and bottoming out the master before reaching full line pressure.

    then again, if these are all new parts and you haven't driven the truck in decades, it could also be pads that aren't bedded in yet. If the truck feels like it's at least stopping safely, go bed the pads for 50-100 miles.
    --Tom
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    Quote Originally Posted by Filthy Filbert View Post
    air would be soft and mushy at the top of the pedal stroke, not the bottom. almost sounds like you're running out of pedal stroke and bottoming out the master before reaching full line pressure.

    then again, if these are all new parts and you haven't driven the truck in decades, it could also be pads that aren't bedded in yet. If the truck feels like it's at least stopping safely, go bed the pads for 50-100 miles.
    50-100 miles? Cant wait to hear the update in another 10 years!
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    Sick 660r's Avatar
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    I'm running the same calipers with a smaller MC and I don't have an issue with the volume or stroke. I think he has a brake pad issue.


    Quote Originally Posted by BluRT00 View Post
    Part your red sport out and buy a gen 2. Problem solved.

  22. #22

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    stop the bullshit and just go hydro boost, problem solved
    "the vast majority of the people on this website are such tight asses that they could probably squeeze out diamonds - but they'd never spend the money to buy the coal' - Steve F. 2012

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    Quote Originally Posted by dakrt23 View Post
    50-100 miles? Cant wait to hear the update in another 10 years!


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    Quote Originally Posted by Hugh Jassole View Post
    stop the bullshit and just go hydro boost, problem solved
    I don't think that would solve it. Plus getting the pedal ratio right is not something I want to do. After talking to Richard he believes you have to make a new pedal assembly, otherwise you need a contraption of some kind. I believe there to be some tweaks possibly in eliminating the combo valve and hooking the fronts up direct to the mc and a prop valve for rear circuit. For now it stops fine, prolly as good or better than stock so I will just live with what I have until the rest of the laundry list is completed.


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    hydro boost for the ram is next on the mod list. I like the increased pressure, sure. But my goal here is to eliminate the huge booster. It makes getting to the back 4 plugs on that side a bitch. that and the booster is going, it makes a funny wheeze noise when you step on the brakes now. hell, that piece has over 150K miles on it. It doesn't owe me a thing. Using ram 2500 parts this should be pretty close to a plug & play swap
    "the vast majority of the people on this website are such tight asses that they could probably squeeze out diamonds - but they'd never spend the money to buy the coal' - Steve F. 2012

    "Don't be obsessed with your desires Danny. The Zen philosopher Basho once wrote, "A flute with no holes is not a flute, and a doughnut with no hole is a Danish" - Ty Webb, 1980

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