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Thread: Hydraboost or 13 inch disc to upgrade braking

  1. #21
    Registered Member chevynut's Avatar
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    Quote Originally Posted by Rick_L View Post
    Thing is, the pedal ratio you can achieve without creating binding in the linkage is limited. On a 55-57, a flat mount booster or a manual setup is a setup that works well both with the geometry and with potential brake line pressure with the stock 6:1 ratio. An angled mount lends itself to a 4:1 ratio.
    That's probably true, but maybe Bill's simplest fix would be to simply change the booster mounting angle and go to a higher pedal ratio. That's why I asked where it is now.

    100 pounds pedal force is a lot. I think this is panic stop territory, not normal driving territory.
    Yes it is quite a bit for one leg. But I think what Bill is trying to do is address those panic stops since he's trying to lock up the tires. At least that's what I understand. He said the MAXIMUM pressure he can get is 800 PSI. I'll bet he's applying a lot of force to the pedal to get that.
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension

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  2. #22
    Registered Member chevynut's Avatar
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    More info....the C4 spec I quoted of 1250 PSI with 100 pounds of pedal force is using a 3.5:1 pedal ratio and a 7/8" bore master cylinder with a 9.4" single diaphragm booster.

    That means the force on the MC piston is 1087 pounds. The force on the pedal pushrod is 350 pounds. So the vacuum booster is providing over 3X boost.
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension

    You can see my 56 Nomad build here http://www.picturetrail.com/chevynut

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    56 Chevy 210 4-door sedan
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    2003 Chevy Silverado 2500 HD Duramax

  3. #23
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    Quote Originally Posted by Rick_L View Post
    Thing is, the pedal ratio you can achieve without creating binding in the linkage is limited. On a 55-57, a flat mount booster or a manual setup is a setup that works well both with the geometry and with potential brake line pressure with the stock 6:1 ratio. An angled mount lends itself to a 4:1 ratio.

    You also can work with master cylinder bore size to optimize this. More pedal ratio = more line pressure but more pedal travel. Smaller master cylinder bore = more line pressure and more pedal travel. This for a given caliper bore.

    100 pounds pedal force is a lot. I think this is panic stop territory, not normal driving territory.
    How does one validate "100 pounds of pedal force", calculation or with an instron?


  4. #24
    Registered Member chevynut's Avatar
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    Quote Originally Posted by NCW View Post
    How does one validate "100 pounds of pedal force", calculation or with an instron?
    You could put some sort of scale between the pedal and your foot...like a bathroom scale or something similar that would fit and goes to 100 pounds. Or you could put a 2x4 on the pedal with a bathroom scale on top of that and sit in the seat and do a bench press. Maybe a hydraulic jack could be used pressing on the seat.
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension

    You can see my 56 Nomad build here http://www.picturetrail.com/chevynut

    For affordable C4 Corvette Suspension conversions for your car, visit http://www.classicedgedesigns.com

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    56 Chevy 210 4-door sedan
    57 Chevy 210 4-door sedan
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  5. #25
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    You guys are right, it's not an easy deal to get real data on if you want to do it the hard way.

    But you can get real data on the brake line pressure, and knowing all the other variables you can come up with something on a non-boosted system. This would take the boost out of the situation, which is a variable that's harder to nail down.

    My logic says that for you to put 100 pounds on the pedal with your foot, you need to use all or most of your strength, and you have to apply a similar reaction force to apply this force. Sitting in a driving position, this means you have to pull on the steering wheel with that same 100 pounds of force because there's not much else to react to that 100 pounds from your foot. Yeah you can do it, but you probably can't sit in the shop and do it every time unless you're a big strong guy. The 125 pound wife can't.

  6. #26
    Registered Member Bihili's Avatar
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    Quote Originally Posted by Rick_L View Post
    Yeah you can do it, but you probably can't sit in the shop and do it every time unless you're a big strong guy. The 125 pound wife can't.
    She doesn't drive it that much but the brakes are the reason why.
    On a side note, my second 57 project (cruiser) is a cheaper build but has the 11 inch disc and hyrdoboost with the LS engine but it is 3 or 4 years from completion.
    I could rob the hydroboost from it but CPP has a sale on their 13 inch disc brakes this weekend and I may go that route first.
    Bill 1957-427-177-6-410

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