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1939-47 Job rated 1/2 ton truck brake upgrades


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I'm wondering if anyone out there is driving a 1939 - 47 Dodge or Plymouth pickup with upgraded (front  discs / rear drums) brakes? A couple years ago I installed a Borg Warner S10 T5 trans behind my Flathead and a 1986 Jeep Cherokee 3.55 differential along with it's drum brakes and that all went OK. I also installed a Master Cylinder from the same 86 Cherokee in my original bell housing location. It sorta worked, but too much pedal travel which I believe is due to the smaller (.9375) M.C. bore? The original M.C. had 1.375 bore.  I'm now considering converting the front drum brakes to disc. The Rusty Hope setup has my attention, but I'm hoping to talk to someone that may have done this before. The more I read about brake engineering and about the myriad of issues others have had modifying brake systems, I'm hesitant to start buying any parts. Not wanting to offend any purists, I have gone to great pains to keep my truck visually original and have all the parts to go back if I wanted to. I'm hoping to make it a bit safer stopping now that it goes a bit faster at lower rpm. I want to keep my original wheels as well.  I've been reading for days on several sites trying to find trucks similar to mine with the brake modifications and how they perform. No luck so far. Perhaps I'm not searching correctly but haven't found much regarding 39-47 dodge / Plymouth pickups. Any advice would be much appreciated!

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Attached is a pdf explaining the installation of a Rusty Hope kit on my 1941 PT125 June 2019.  The only difference is that I replaced the master cylinder with a double outlet MC for safety.  The MC was a corvette type which worked with a homemade adapter plate and the stock push rod.

P1120727.jpg

P1120730.jpg

Rusty Hope Disc Brake Install.pdf

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2 hours ago, PT81PlymouthPickup said:

I'm wondering if anyone out there is driving a 1939 - 47 Dodge or Plymouth pickup with upgraded (front  discs / rear drums) brakes?

I am driving a 1941 Plymouth truck with Rusty Hopes front disc kit and Dakota rear end . I am using the stock master cylinder and everything works fine with perfect pedal free travel . I have no experience with the other modifications that you have mentioned . 

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Thanks Campton 1941 and thanks Jerry Roberts

 

Are either of you guys using combination, proportioning, residual or metering valves of any kind to address bias?

Also, were you able to mount your original 16 inch wheels without interference?

Question for Campton: Would you know the piston diameter of your Corvette master cylinder?

 

Very much appreciated your responses. 

 

Steve

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3 hours ago, Campton1941 said:

Attached is a pdf explaining the installation of a Rusty Hope kit on my 1941 PT125 June 2019.  The only difference is that I replaced the master cylinder with a double outlet MC for safety.  The MC was a corvette type which worked with a homemade adapter plate and the stock push rod.

P1120727.jpg

P1120730.jpg

Rusty Hope Disc Brake Install.pdf 254.36 kB · 3 downloads

How did you identify which MC (they've made a lot of vettes)? Also are those flex lines for the fluid?

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"  Are either of you guys using combination, proportioning, residual or metering valves of any kind to address bias?  

Also, were you able to mount your original 16 inch wheels without interference? "  If you are going to use Charles kit he says that you can use your original rims if I remember correctly . Contrary to popular opinion , I am using the original master cylinder with the existing residual valve intact . I also bought the commonly used 2 and 6 pound residual valves and didn't need them , they have been sitting on my garage shelf for about 2 years .  

 

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On 11/11/2019 at 7:47 PM, MarkAubuchon said:

I have the rusty hope conversion, added jeep dual MC, proportioning valves  help with pedal travel when the MC is below the calipers and you have disc and drums. 

* residual pressure valves keep the drums from retracting the prop valve keeps the rears from locking up 1st

Edited by Radarsonwheels
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On 11/11/2019 at 7:47 PM, MarkAubuchon said:

I have the rusty hope conversion, added jeep dual MC, proportioning valves  help with pedal travel when the MC is below the calipers and you have disc and drums. 

Mark, could you tell me what year and model jeep your dual MC and prop. valve came from?  Am I correct, that you do not have a booster? Are you happy with your braking? Can you lock them up if needed?   Steve ?

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On 11/10/2019 at 9:56 PM, Jerry Roberts said:

If you are going to use Charles kit he says that you can use your original rims if I remember correctly . Contrary to popular opinion , I am using the original master cylinder with the existing residual valve intact . I also bought the commonly used 2 and 6 pound residual valves and didn't need them , they have been sitting on my garage shelf for about 2 years .

Jerry,  Yes, just about everyone tells me split master cylinder with Prop. valve in order to be safe with disc / drum brakes.  Does your truck stop well? Can you lock up the brakes? (Please don't go and test on the highway) I would think with the original master cylinder (1-3/8" dia. bore) you would have to stand on your brake pedal?  Steve :)

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6 hours ago, PT81PlymouthPickup said:

Jerry,  Yes, just about everyone tells me split master cylinder with Prop. valve in order to be safe with disc / drum brakes.  Does your truck stop well? Can you lock up the brakes? (Please don't go and test on the highway) I would think with the original master cylinder (1-3/8" dia. bore) you would have to stand on your brake pedal?  Steve :)

 Steve , It stops very well , I have locked up the brakes twice as there were dogs running loose in the street . One little dog was actually running towards me . Full brake pedal too . I don't have to  stand on the pedal and obviously a power assist isn't needed . I did occasionally have to stand on the pedal with the original shoes , even though the shoes were new and making full contact . I always would wonder if something was going to break when applying so much force on the system with the original shoes .  I don't know the bore size of my original master cylinder off hand . If my cylinder bore size is important to you , let me know and I will look it up in my records . 

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10 hours ago, Jerry Roberts said:

 Steve , It stops very well , I have locked up the brakes twice as there were dogs running loose in the street . One little dog was actually running towards me . Full brake pedal too . I don't have to  stand on the pedal and obviously a power assist isn't needed . I did occasionally have to stand on the pedal with the original shoes , even though the shoes were new and making full contact . I always would wonder if something was going to break when applying so much force on the system with the original shoes .  I don't know the bore size of my original master cylinder off hand . If my cylinder bore size is important to you , let me know and I will look it up in my records . 

 

Thanks Jerry for your reply! Please don't go to any pains, but it would be interesting to know your mc bore dia. I have been reading incessantly about brake systems and the mathematics involved only to become more confused.  When I ask the companies who are selling the conversion kits, none of them seem willing to recommend a master cylinder and prop.valve? I do know for certain that a dual mc split system is safer if a brake line or hose should rupture you still have some braking.   So far of the kits I've looked at, Charlie's (Rusty Hope) looks the best to me. The one thing I'm uncertain about is the inner bearing spacer. It appears by spacing out that inner 1.250 I.D. bearing, it may not engage on the spindle completely? Might you recollect? Do you have any complaints about the Rusty Hope setup?  Did you have any issues with the retaining nut and cotter pin?  Sorry for all the questions. Regards, Steve

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6 hours ago, PT81PlymouthPickup said:

So far of the kits I've looked at, Charlie's (Rusty Hope) looks the best to me. The one thing I'm uncertain about is the inner bearing spacer. It appears by spacing out that inner 1.250 I.D. bearing, it may not engage on the spindle completely? Might you recollect? Do you have any complaints about the Rusty Hope setup?  Did you have any issues with the retaining nut and cotter pin?

Steve ,  Have you read Charlie's instructions ?   If not , check his web site or you can probably find them with a google search . On my master cylinder diameter ;  When I had my master cylinder sleeved , the guy who did the machine work sent a note that the bore was 1 1/4 inch . Also you could verify by checking the bore size for Raybestos master cylinder kit MK1 as I used that kit . My list also says that NAPA kit #1 is the correct item . In Charlie's instructions  he mentions that sometimes you must ' stake ' the spindle so that the spacer fits tight . I don't have any complaints at all . There was a discussion on this forum about Charlie's various recommendations for securing the retaining nut and the cotter pin . Some people had strong feelings . I am OK with his methods . 

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14 hours ago, Jerry Roberts said:

Steve ,  Have you read Charlie's instructions ?   If not , check his web site or you can probably find them with a google search . On my master cylinder diameter ;  When I had my master cylinder sleeved , the guy who did the machine work sent a note that the bore was 1 1/4 inch . Also you could verify by checking the bore size for Raybestos master cylinder kit MK1 as I used that kit . My list also says that NAPA kit #1 is the correct item . In Charlie's instructions  he mentions that sometimes you must ' stake ' the spindle so that the spacer fits tight . I don't have any complaints at all . There was a discussion on this forum about Charlie's various recommendations for securing the retaining nut and the cotter pin . Some people had strong feelings . I am OK with his methods .

 

Jerry, I have not been able to locate Charlie's instructions yet. I'm hoping to find them which would be helpful in my decision. You are correct about the master cylinder bore. I rechecked mine and it is 1 1/4". I measured incorrectly the first time. Are you using DOT3 or 4 fluid?  I was using DOT5 silicone and have had some weird things happen. I'm planning on returning to DOT3 / DOT4 after I upgrade the brakes.

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