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Thread: Do disc brake kits need power assist?

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    Do disc brake kits need power assist?

    It would be interesting to hear from members who have personal experience with any of the disc brake conversion kits that are available for Studebakers like Turner and Hotrodandbrakes. Most modern cars with disc brakes have power assists. The few times I've heard talk about cars with factory disc brakes and no power assist it has sounded like the pedal pressure required was very high. What is the feeling from people who have used the kits? I know the stopping power is much improved, but is the pedal pressure something that might be a deterrent perhaps to your wife or teenage daughter? And what have users done to convert the disc systems to power assist? Thanks.

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    I have had both. The short answer is no, not at all. Going from non-power drums to non-power discs is still a good step in the right direction. It takes a bit more input from the right foot, but it is not at all a problem if the master cylinder is big enough. I also have a 70's Porsche which has 4 wheel disc brakes without power assist from the factory and it stops better than anything else I own.

    The lark has been converted to 4 wheel power disc brakes, which works very well, but I think it's actually overkill. I have to be rather mindful of how quickly I apply pedal because it will lock up all four on gravel without effort.

    Hope that helps.

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    Quote Originally Posted by hitbyastick View Post
    I have had both. The short answer is no, not at all. Going from non-power drums to non-power discs is still a good step in the right direction. It takes a bit more input from the right foot, but it is not at all a problem if the master cylinder is big enough. I also have a 70's Porsche which has 4 wheel disc brakes without power assist from the factory and it stops better than anything else I own.

    The lark has been converted to 4 wheel power disc brakes, which works very well, but I think it's actually overkill. I have to be rather mindful of how quickly I apply pedal because it will lock up all four on gravel without effort.

    Hope that helps.
    I have to disagree. Not a Studebaker, but I converted my '59 Sprite from drum brakes to front discs, no power boost. The pedal effort went way up, perhaps double. I was able to reduce the pedal effort by going to a smaller (3/4" bore) master cylinder from the original 7/8" bore. A larger bore master cylinder increases the pedal effort.

    Disconnect the vacuum boost on any modern disc brake car, and you'll need both feet on the brake pedal.

    Factory original is a different animal. Those cars will have the correctly proportioned cylinders.

    Locking up on gravel is meaningless. If you can't lock up on clean, dry pavement, your brakes are not good enough.

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    Yes, No, Maybe. It all depends upon:

    1. The pedal used; the power brake pedal is different than the manual brake pedal.
    2. The friction material used. Since essentially all OEM disc brakes today are vacuum or hydroboost assisted, a harder friction material is chosen for longer wear and reduced fade. It's difficult to find the old-school softer pads and shoes.
    3. The diameter and weight of the tires and wheels. Larger diameter wider tires have more rotating inertia. Takes more effort to whoa them down.
    4. Disc/drum or four-wheel-discs?
    5. The size/weight/strength of the driver. We have a member here who's a fine figure of a man and has driven without power assist for years. Take a more lightly built female or a member who's getting way up in years, he/she won't be safe without power assist.

    jack vines
    PackardV8

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    I’ve wondered about this modern disc brake stuff. I found a Turner brake setup at a swap meet about fifteen years ago. I bought it to install on my son’s 63 disc brake GT Hawk. I was told you didn’t need the booster which intrigued me as his booster was acting up. Have never installed the setup but eventually will. I think it used Mustang or Chrysler pads? I know the surface area of the pads was at least larger by a factor of two or more.

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    President Member Colgate Studebaker's Avatar
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    I'm going to use the Turner 4 wheel disc system on my '64 GT Hawk. I am also adapting a suspended pedal (Lark) and adding a power booster. At this point I don't know what master cylinder I'll use, I need to talk to Jim Turner about it. I want it to be easy for my wife to drive and the power assist will make us feel more confident about it's safe operation. Bill

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    President Member Xcalibur's Avatar
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    It depends on what you are replacing and the master-cylinder it used if you are going to continue with that m/c. If you have a m/c that required a booster to work originally, it will continue to do so with almost any conversion. All the best.

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    President Member bensherb's Avatar
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    Quote Originally Posted by PackardV8 View Post
    Yes, No, Maybe. It all depends upon:

    1. The pedal used; the power brake pedal is different than the manual brake pedal.
    2. The friction material used. Since essentially all OEM disc brakes today are vacuum or hydroboost assisted, a harder friction material is chosen for longer wear and reduced fade. It's difficult to find the old-school softer pads and shoes.
    3. The diameter and weight of the tires and wheels. Larger diameter wider tires have more rotating inertia. Takes more effort to whoa them down.
    4. Disc/drum or four-wheel-discs?
    5. The size/weight/strength of the driver. We have a member here who's a fine figure of a man and has driven without power assist for years. Take a more lightly built female or a member who's getting way up in years, he/she won't be safe without power assist.

    jack vines
    Jack is exactly correct here.

    There are a LOT of variables to be considered. I changed the drum brakes on my VW to four wheel disks with no power, using the same master cylinder, and it stops great! Easily 200% better with just a tiny bit more required pedal effort. It doesn't always work out that way though. About 30 years ago we put disk brakes (no power) on the front of my dads '53 Coupe using a kit from Dave Leveque. He is and has been very happy with them since. I had not driven his car until a couple years ago, and I don't know how he can get it to stop. He still says it stops great, and he's over 80, 24 years older than I. I can't drive his car, it takes way more pedal effort than I can muster for more than a couple stops. My stock '62GT no power drum brakes required FAR less pedal effort and will stop the car in FAR less distance than I can stop his car in. I still found the GT's stock brakes to be barely adequate for driving in today's California traffic. I swapped them for the entire 4 wheel power disk system from a 2004 Mustang. The two cars have the same weight bias and overall weight (actually the Hawk is a little bit lighter).

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    President Member Rerun's Avatar
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    I installed the Turner front disks on my '64 Daytona HT without a booster. The resulting pedal effort was just about the same as the drum brakes had been. Unfortunately, i don't recall the M/C diameter that I used.
    Jim Bradley
    Palmyra, VA
    '78 Avanti II

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    OK Hijack time.... Does anybody know what that pad material is called that some folks are using? it's supposed to be much better at stopping non-power discs.

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    Golden Hawk Member DEEPNHOCK's Avatar
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    It is a question of hydraulics.
    What pressure do you need at the caliper to obtain the braking effort you need.
    How do you mechanically create that pressure based on pedal effort?
    There is some mechanical multiplication done at the pedal pivot level.
    But most of the pressure creation has to do with master cylinder piston size/stroke as it relates to caliper piston size/stroke.
    Change one thing, it changes everything else.
    Keep your quest simple and do
    not try to skimp when it comes to brakes.
    HTIH (Hope The Info Helps)

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    Golden Hawk Member DEEPNHOCK's Avatar
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    Quote Originally Posted by Mrs K Corbin View Post
    OK Hijack time.... Does anybody know what that pad material is called that some folks are using? it's supposed to be much better at stopping non-power discs.
    A legitimate question.
    The answer is as clear as marketing mud.
    But... In basic terms...
    The more aggressive the brake pad/shoe material, the more aggressive the braking will be.
    The tradeoff is disc/drum life and brake noise. The softer the pad/shoe, the smoother the braking effort is, and the longer the disc/drum life will be.
    Usually the softest pad/shoe lining is the OE initial install. The OE's major concern is customer satisfaction and getting through the warranty period.
    HTIH (Hope The Info Helps)

    Jeff


    Get your facts first, and then you can distort them as much as you please. Mark Twain



    Note: SDC# 070190 (and earlier...)

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    President Member Michidan's Avatar
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    I only buy Callahan brake pads. The warranty on the box makes me feel good.

  14. #14
    President Member Michidan's Avatar
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    To add some serious content, I do run non-power disc front and drum rear on my Studebaker. But there is nothing Studebaker in the entire system so not sure how relevant my experience would be. I read up on pressure and pedal ratio a lot first, so tried to engineer it properly. I don't mind the brakes, but it does require a pretty heavy foot. I used a pedal from a power brake truck, then relocated the hole to get a better ratio. It's still not ideal but better.
    I never once considered brake pad material, but after reading this thread I might now.

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    President Member Colgate Studebaker's Avatar
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    To K. Corbin, the pads you are asking about are EBC "Green Stuff" per prior threads on these pads. Supposed to be very good, and I intend to find them for my Hawk when the time gets here. Hope this helps you, Bill.

  16. #16
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    NO...no system "needs" a booster.
    One just needs to do their, do diligence and do a little bit of study on what needs to be used where.

    As long as the proper master cylinder piston size is used vs. caliper piston size, no booster required.
    I have two Stude wagons that can easily prove that.
    Very easy pedal.

    Mike

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    Quote Originally Posted by jnormanh View Post
    I have to disagree. Not a Studebaker, but I converted my '59 Sprite from drum brakes to front discs, no power boost. The pedal effort went way up, perhaps double. I was able to reduce the pedal effort by going to a smaller (3/4" bore) master cylinder from the original 7/8" bore. A larger bore master cylinder increases the pedal effort.

    Disconnect the vacuum boost on any modern disc brake car, and you'll need both feet on the brake pedal.

    Factory original is a different animal. Those cars will have the correctly proportioned cylinders.

    Locking up on gravel is meaningless. If you can't lock up on clean, dry pavement, your brakes are not good enough.
    I'm going to itemize my response here:

    1) When you changed to disc/drum did you add a proportioning valve? Also the brake contact area is important. It's not exactly apples to apples, but the short answer is still no, you don't absolutely need a power booster.

    2) Why would you disconnect a power booster? A poor comparison as the entire system was designed with the booster functioning. As I had mentioned, I have a car with discs and no power and it stops just fine with great pedal feel.

    3) Again, the factory would have set things up as a system. I don't see what you mean by "correctly". Anyone can add an adjustable proportioning valve, or one from a disc/drum car. They're not expensive and will greatly influence how the car responds.

    4) I was stating that I'm locking up on gravel with (large) power disc brakes on all four corners with very little pedal input, implying that my I don't need as much braking as I have.

    Regardless, as stated below, there are far more variables at play and I'm stating my own experiences having both built custom brake systems and upgrading stock systems with aftermarket components.

  18. #18
    Silver Hawk Member 53k's Avatar
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    Quote Originally Posted by dstude View Post
    It would be interesting to hear from members who have personal experience with any of the disc brake conversion kits that are available for Studebakers like Turner and Hotrodandbrakes. Most modern cars with disc brakes have power assists. The few times I've heard talk about cars with factory disc brakes and no power assist it has sounded like the pedal pressure required was very high. What is the feeling from people who have used the kits? I know the stopping power is much improved, but is the pedal pressure something that might be a deterrent perhaps to your wife or teenage daughter? And what have users done to convert the disc systems to power assist? Thanks.
    Not exactly an engineering report, but some years ago I bought a '64 GT that had been sitting for at least nine years, part outside and part garaged, without running, It was a four-speed with power disc brakes. I winched it onto my trailer and took it home. When I got it home and started checking it I found that the hydrovac was in the trunk, but the lines were hooked up in the engine compartment, no booster of any sort. With some fresh gas and a new battery the GT started up very readily and ran beautifully. I decided to try it on the road even though the brakes were not boosted at all and I found that it was no trouble at all to stop. It just felt like conventional brakes to me. I got bolder and took it on the highway- still no problem. I have no idea if the master cylinder was different from original.
    I sold the car at the next York.

    Paul Johnson, Wild and Wonderful West Virginia.
    '64 Daytona Wagonaire, '64 Avanti R-1, Museum R-4 engine, '72 Gravely Model 430 with Onan engine

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    Quote Originally Posted by hitbyastick View Post
    I'm going to itemize my response here:

    1) When you changed to disc/drum did you add a proportioning valve? Also the brake contact area is important. It's not exactly apples to apples, but the short answer is still no, you don't absolutely need a power booster.

    2) Why would you disconnect a power booster? A poor comparison as the entire system was designed with the booster functioning. As I had mentioned, I have a car with discs and no power and it stops just fine with great pedal feel.

    3) Again, the factory would have set things up as a system. I don't see what you mean by "correctly". Anyone can add an adjustable proportioning valve, or one from a disc/drum car. They're not expensive and will greatly influence how the car responds.

    4) I was stating that I'm locking up on gravel with (large) power disc brakes on all four corners with very little pedal input, implying that my I don't need as much braking as I have.

    Regardless, as stated below, there are far more variables at play and I'm stating my own experiences having both built custom brake systems and upgrading stock systems with aftermarket components.
    Responses to your points/questions

    1. & 3. I did not use a proportioning valve as the factory used none on the later cars which had discs on the front. I DID use the 3/4" master cyl as did the factory on front disc cars. The change from 7/8" to 3/4" reduces pedal effort by (calculated) 27%

    2. I have not disconnected a factory booster. The factory used none on the disc brake cars. What I was saying is: if a factory booster were removed, the pedal effort would be much higher.

    4. I don't see how being able to lock the wheels on gravel is relevant. If you can lock up on clean dry pavement with reasonable pedal effort, then, no, you don't need a booster. However if you are 6', and weight 200#, then you may be okay with un-boosted brakes whereas someone older, smaller or of a different gender might not be.

  20. #20
    President Member BobWaitz's Avatar
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    I added a Turner kit to a '53 Commander, using the dual master and the proportioning valves. The rear end was upgraded to a 8-inch F*rd. While it requires more pedal effort than a modern power disk setup, there is never any question that you are going to stop.

    I added a power-disk setup to my M5 (259 V8, Nova rear end) and it is just like driving a modern car.

    I'm completely OK with either.

  21. #21
    President Member Jerry Forrester's Avatar
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    [QUOTE=jnormanh;The change from 7/8" to 3/4" reduces pedal effort by (calculated) 27%
    [/QUOTE]
    But doesn't that mean the brake pedal has to move 27% farther?
    One needs to be sure that the master cylinder push rod has the required clearance and the master cylinder bottoms out (or almost) at the same time the pedal hits the floor.
    Jerry Forrester
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  22. #22
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    Quote Originally Posted by Michidan View Post
    I only buy Callahan brake pads. The warranty on the box makes me feel good.
    THAT WAS HILARIOUS ! ! ! ! One of our favorite movies. And one of our favorite movie quotes.
    But... I used a conversion to disc brakes decades ago which used Ford Galaxie rotors and Chrysler calipers. So the brakes were huge. 12" ventilated rotors with calipers from a 5000 lb Chrysler. I used the stock master cylinder under the floor and never had an issue with pedal pressure being too great. It tracked straight and I swapped out the rear wheel cylinders to get an even activation on the lock up of the tires when braking hard. Like others, I never thought to catalog everything back when I did the conversion, but I drove the car for 30 years with that setup on it. I never had an issue in any regard.
    sals54

  23. #23
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    Quote Originally Posted by Jerry Forrester View Post
    But doesn't that mean the brake pedal has to move 27% farther?
    Yes, of course. On this particular car the maximum pedal travel is bout 4", The brakes are full on at about 1.5" That's one of the benefits of discs, they self compensate for wear, retracting only as far as the rotors push them. Of course modern drum brakes incorporate a ratchet and star wheel or other mechanism to self adjust. It's activated when stopping in reverse.

    In days of yore, one would have to manually adjust drum brakes, usually via a star wheel, but I think the last of those were phased out in the 1950s.

    Change the oil, grease the chassis, flush the radiator, replace the anti-freeze, clean the plugs, file the points, tune the carburetor, adjust the valves, and adjust the brakes. Back when "Service Stations" did more than sell gasoline.

  24. #24
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    A few years back, I installed The Turner disc brake kit on our 63 Lark, 2 dor and the brakes worked great without power assist. It did require a little more effort, but I ever had to stand on the brakes to stop. I have since installed a power booster but mainly because I had a new old stock unit I bought years earlier. Just be sure your master cylinder is in good shape and be sure the master cylinder is bled thoroughly and you should be good to go.

  25. #25
    President Member bensherb's Avatar
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    Quote Originally Posted by jnormanh View Post
    In days of yore, one would have to manually adjust drum brakes, usually via a star wheel, but I think the last of those were phased out in the 1950s.
    My 1962 GT had manually adjusted drum brakes, no self adjusters. One reason for my swap to disks, they worked reasonably well but needed constant adjusting to do so, was something missing?

  26. #26
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    Quote Originally Posted by bensherb View Post
    My 1962 GT had manually adjusted drum brakes, no self adjusters. One reason for my swap to disks, they worked reasonably well but needed constant adjusting to do so, was something missing?
    Perhaps the part that keeps the self adjuster from moving on its own.
    Gary L.
    Wappinger, NY

    SDC member since 1968
    Studebaker enthusiast much longer

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