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Re: New disc brake thread
Tony292 #1384117 Wed Nov 11 2020 12:51 AM
Joined: Jun 2019
Posts: 21
C
'Bolter
Heres my thoughts when I went down the path of trying to convert to disc brakes..

The original disc brake thread can be quite confusing.. at least at the time it was for me. I did end up finding the correct P30, big 5, front axle but have yet to machine the sleeve spacer (I think thats what it was?) and install.

Mostly because I also wanted to convert to hydroboost at the same time. I've got a hy-power (hydroboost) unit and master cylinder from a GMC 7000 that I thought I would use. However, a member on the 67-72 forum tried this setup and noted that the brakes were pretty stiff. I guess the pedal ratio of the old setup did not match up for the hydroboost master cylinder. If I recall, the brakes worked but not great. Maybe one day I'll figure something out myself.

If I could go back and advise myself, I would recommend to go with Randy as he has said he uses common parts. That and hes in Indy


1971 Chevy K10
1968 Chevy C50
1966 GMC 4000 Tilt Cab
Re: New disc brake thread
Tony292 #1384126 Wed Nov 11 2020 01:40 AM
Joined: Jun 2011
Posts: 4,192
E
'Bolter
What does he mean by ‘pretty stiff’? If you mean hard to push, 7000 hydro boost might give different pressures the pickup hydro boost? Also, like you said pedal ratios enter into the picture.

Does he know if the pump was putting out required pressure?

Ed


'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires.
'47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle.
'54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed.
'55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
Re: New disc brake thread
Tony292 #1384183 Wed Nov 11 2020 08:14 PM
Joined: Nov 2020
Posts: 3
D
Moderated
I know you have been talking disc brakes for a long time. I just joined and i have a 1937 1-1/2 ton. i desigend my own kit. I liked it to look original but needed brakes in the mountins.My objective was to put it togeter so that i can revert back to origianl. I attached some photos of the conversion. Its not very hard to design and install. I'm not familiar with different years or models what would work or not.

Anders

Attached Files
Brake front disc 3.jpg (224.31 KB, 297 downloads)
Brake front disc 2.jpg (257.26 KB, 300 downloads)
Brake front disc 4.JPG (206.25 KB, 294 downloads)
Brake front disc.jpg (169.79 KB, 293 downloads)
Brake parts.JPG (321.51 KB, 277 downloads)
Re: New disc brake thread
Tony292 #1384196 Wed Nov 11 2020 11:41 PM
Joined: Jun 2011
Posts: 4,192
E
'Bolter
Anders,

Nice job, are the discs willwood, too, what OD are they? I might like to come see your setup sometime. Do you still have the original engine?

Thanks,

Ed


'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires.
'47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle.
'54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed.
'55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
Re: New disc brake thread
Ders #1384208 Thu Nov 12 2020 01:37 AM
Joined: Nov 2010
Posts: 613
R
Shop Shark
Originally Posted by Ders
I know you have been talking disc brakes for a long time. I just joined and i have a 1937 1-1/2 ton. i desigend my own kit. I liked it to look original but needed brakes in the mountins.My objective was to put it togeter so that i can revert back to origianl. I attached some photos of the conversion. Its not very hard to design and install. I'm not familiar with different years or models what would work or not.

Anders

Anders, That looks like a nice conversion. Very nice to keep the old backing plate. Any idea what diameter the rotors are? They look pretty small. My kit uses a 15" diameter rotor with a dual piston caliper and a dual circuit vacuum boosted master.


Randy Domeck
Indianapolis Fabrications
rdomeck@me.com
Indianapolis, In. 46254
317-258-0039

Re: New disc brake thread
Tony292 #1384216 Thu Nov 12 2020 02:53 AM
Joined: Mar 2019
Posts: 1,292
G
'Bolter
Way cool. Good job. I also like the backing plate still there. Looks funny without the wheel cylinder in there. thumbs_up

Re: New disc brake thread
Tony292 #1384973 Tue Nov 17 2020 05:56 PM
Joined: Dec 2008
Posts: 402
F
Shop Shark
I've done the P30 swap just a couple months ago. Yes the spindles are hard to find. I got mine out of a 1985 Grumman stepvan. Had the kingpins and bronze bushings installed and now I have a good axle with disc brakes. They're big brake parts too so I feel comfortable with how they will stop. Here's my set up.

https://i.imgur.com/btIKcyE.jpg
https://i.imgur.com/rkkgoVg.jpg
https://i.imgur.com/BjqP7UC.jpg
https://i.imgur.com/NYTIJN1.jpg
https://i.imgur.com/bUoH4Dx.jpg
https://i.imgur.com/LPGOwti.jpg
https://i.imgur.com/H1bgIje.jpg
https://i.imgur.com/uytGhtV.jpg


1956 Chevy School Bus Superior Body
In the Stovebolt Gallery
More pix in Photobobucket
Re: New disc brake thread
fclaridge #1384990 Tue Nov 17 2020 07:39 PM
Joined: Oct 2019
Posts: 298
T
Tony292 Offline OP
Shop Shark
Originally Posted by fclaridge
I've done the P30 swap just a couple months ago. Yes the spindles are hard to find. I got mine out of a 1985 Grumman stepvan. Had the kingpins and bronze bushings installed and now I have a good axle with disc brakes. They're big brake parts too so I feel comfortable with how they will stop. Here's my set up.

https://i.imgur.com/btIKcyE.jpg
https://i.imgur.com/rkkgoVg.jpg
https://i.imgur.com/BjqP7UC.jpg
https://i.imgur.com/NYTIJN1.jpg
https://i.imgur.com/bUoH4Dx.jpg
https://i.imgur.com/LPGOwti.jpg
https://i.imgur.com/H1bgIje.jpg
https://i.imgur.com/uytGhtV.jpg

What year is your truck and what rims are you using? One problem with the P30 conversion is that at least on my 1940 1.5 ton, I’d have a different bolt pattern than before, necessitating the need to run different rims in the front than the rear. Mine is a 10/5 lug 4.75 center circle with 7.25 spacing. So if I wanted to go the P30 route I’d have to swap the rear axle in as well to be able to run the same rims all the way around.

Last edited by Tony292; Tue Nov 17 2020 07:49 PM.
Re: New disc brake thread
Tony292 #1384994 Tue Nov 17 2020 08:18 PM
Joined: Dec 2008
Posts: 402
F
Shop Shark
I have a 1956 short school bus. 5/10 7.25 with 5.25 bore. I am on 22.5" aluminum Alcoa wheels with adapters. I have a later model Dana 80 rear axle with the same lug pattern as my 56 axle had, but with disc brakes already. So getting the front disc conversion has been high on my list to get done. Here are some pics of my bus and my adapters. You could also put in a spacer ring to make up the difference of the hub bore too.

https://i.imgur.com/VnBQfyu.jpg
https://i.imgur.com/1eV1qlU.jpg
https://i.imgur.com/shpYXLT.jpg
https://i.imgur.com/w5LuNKH.jpg
https://i.imgur.com/L8712x9.jpg
https://i.imgur.com/amDY4xM.jpg
https://i.imgur.com/PQKqe5j.jpg
https://i.imgur.com/5opESyg.jpg
https://i.imgur.com/RYmDC7u.jpg
https://i.imgur.com/eTahsUW.jpg
https://i.imgur.com/uuzHXH2.jpg
https://i.imgur.com/o1CseUm.jpg


1956 Chevy School Bus Superior Body
In the Stovebolt Gallery
More pix in Photobobucket
Re: New disc brake thread
fclaridge #1384997 Tue Nov 17 2020 08:50 PM
Joined: Oct 2019
Posts: 298
T
Tony292 Offline OP
Shop Shark
Originally Posted by fclaridge
I have a 1956 short school bus. 5/10 7.25 with 5.25 bore. I am on 22.5" aluminum Alcoa wheels with adapters. I have a later model Dana 80 rear axle with the same lug pattern as my 56 axle had, but with disc brakes already. So getting the front disc conversion has been high on my list to get done. Here are some pics of my bus and my adapters. You could also put in a spacer ring to make up the difference of the hub bore too.

https://i.imgur.com/VnBQfyu.jpg
https://i.imgur.com/1eV1qlU.jpg
https://i.imgur.com/shpYXLT.jpg
https://i.imgur.com/w5LuNKH.jpg
https://i.imgur.com/L8712x9.jpg
https://i.imgur.com/amDY4xM.jpg
https://i.imgur.com/PQKqe5j.jpg
https://i.imgur.com/5opESyg.jpg
https://i.imgur.com/RYmDC7u.jpg
https://i.imgur.com/eTahsUW.jpg
https://i.imgur.com/uuzHXH2.jpg
https://i.imgur.com/o1CseUm.jpg

And you’ve just highlighted one very big reason that the P-30 disc conversion isn’t a good solution for many of us. It’s great if you have a later model advanced design big bolt with the 5.25center circle, but it’s not a good solution at all for the earlier big bolts with the 4.75 circle. If I went with the P-30 solution in my 1940 1.5 ton I’d end up with 19.5 radials in the front and 20 inch bias ply dually in the back. So for many of us swapping spindles isn’t such a simple solution as the old thread makes it out to be.

Yet the ten year old thread with 15 plus pages and 240,000 views peddles this “solution” as a solution for all big bolts... it’s not. That’s all I’m saying. It’s time to split the solutions to what works for the early vs AD trucks... not just peddle one single solution for one set of trucks as a solution for all 1.5 ton trucks. The alternative is we just split the entire big bolt forum into early and a late sub forums.

Last edited by Tony292; Tue Nov 17 2020 09:37 PM.
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