1970 front disc brake conversion

[picklito]

It's time to do the front swap to discs. It's a 70 GMC big block 2wd 6-lug with power drums. Want to keep the 6-lug and stock height. I'm finding MANY shops selling kits and parts, and the Brothers kit is currently on sale. Does anybody know how large the discs are in the various kits? I'm seeing 12" from McGaughy's. How large are the Brothers, CPP, POL, ECE, etc? How large is a stock GM setup for comparison?

I don't want to go with one of the "big brake" kits, I just want a sufficient size "OE" style replacement.

Any "must avoid" kits out there?

Thanks!

[70 shorty]

I'm interested in "OE style replacement" disc conversions too, but with a dropped spindle. I"ll be keeping an eye out here. I want OE style bc I like my stock 6 lug truck rally wheels.

[picklito]

Yes, I just bought new tires for my 15" rallye wheels! Would like to keep them.

[ksbrktracer]

Mcgaughys does a stock height or drop spindle for the 63-70 with a stock size (12") rotor. they also do a 13" rotor kit. I can get them in 5-lug or 6-lug in 12" or 13" . I can also get a 12" 6-lug rotor to fit the 71 and newer spindle with 1.25 rotor.

[hugger6933]

I am also wanting to go to disc on the front of one of my 70's [the other is gonna be 5 lug] and already have the stuff to do the swap where the use of the 88-98 C2500LD spindle ,rotor and caliper and be used. I haven't given any thought to weather or not my 15 inch rallys would fit it. I'd better give that a try before going much farther in that direction. Thanks for bringing that to light for me guys. Jim

[mmiddle]

Ridetech 11349300 spindles 2" drop. See Rob at NoLimits
1992 LD 3/4 ton rotors (6 lug) and calipers/pads.
1973-87 1/2 ton ball joints and outer tie rods.
1972 bearings and seals
This will give you 11.6" rotors

Doing this will give you replacement peace of mind should you ever need to replace the rotors or calipers.

[mmiddle]

Originally Posted by hugger6933

I am also wanting to go to disc on the front of one of my 70's [the other is gonna be 5 lug] and already have the stuff to do the swap where the use of the 88-98 C2500LD spindle ,rotor and caliper and be used. I haven't given any thought to weather or not my 15 inch rallys would fit it. I'd better give that a try before going much farther in that direction. Thanks for bringing that to light for me guys. Jim

The only issue you might run into is the original steel wheels are made for
1/2" or 7/16" stud and the 1988-9* 3/4 ton rotors are 9/16" stud. Therefore you likely will need to drill out the lug holes by 1/16".

[picklito]

Guys! This is awesome info! Yes I have the stock 7/16" studs on 15" rallye's. mmiddle this is what I was looking for, some stock swap parts. I can go with a kit but you don't know what you get till you have it.

[mmiddle]

I've been doing quite a bit of research on this because I don't car for the unknowns of the kits offered. My original desire was to adapt 99up front brakes so that I had a modern system with ABS, but the spindle/hub configuration is a little more than I want to tackle for now. I have a mill and lathe in my shop and SolidWorks software, but it will take a lot of engineering and modifications to get all this to work properly. And honestly the ABS on 99up trucks is a 3 channel system that is all but worthless.

I still plan to make caliper brackets to utilize the 2 piston calipers from a 99up rather than the single piston units from the older trucks. I am also going to work on fitting the rear disc/Pbrakes from same generation on my truck.
However, it will be months before I start working on these solutions. Right now my focus is rust repair before mechanical.

[hugger6933]

MMiddle they are 14x1.5 METRIC yuck, but I was thinking possibly about a 99-07 rear as well so it would have that size studs as well. Well not to 07 just to 04 cause 05-07 were drum again. MMiddle, in your parts list you list the 3/4 ton rotor and caliper, you also list ball joints from 73-87 won't they not fit in the control arms? Are the spindles you speak of designed to take the later rotor with the earlier ball joints? I haven't given any thoughts going this way until about 3 min ago when I read the above post. I do have all of the other stuff to go the other way and hadn't made plan to lower any. Jim

[picklito]

That sounds like a great project. I've been out of trucks for a while, so my memory of parts and swapping is a little rusty.

I did have a 77 2wd and for my use brakes like that would be fine. Is there a reason I can't get 73-87-ish spindles onto my stock control arms and then just use all stock single-piston calipers, dust shields, etc.? Aren't those 11.5" discs?

[hugger6933]

Pick, I think the reason most people change the control arms as well is the ball joints are a fraction of the price of those from 63 to 70. Some change the whole crossmember and are really happy with that swap as well. It is only a matter of drilling a couple of bolt holes and you in like Flinn. Jim

[mmiddle]

All the control arms are the same, the difference is the steel or rubber bushings. 73-87 ball joints will fit our control arms. You have to match the ball joints to the spindle. According to Rob at NoLimits those RideTech spindles take 73 up ball joints (the stud length is different).
From 88-92ish the studs were still SAE 9/16" fine thread. The 14mm is the same size and interchangeable.

I plan on using modern (99up) wheels on my truck so I have to turn the diameter of the hub flanges down to match. Also have to do this to get the modern rear rotors to fit our axles.

There is a tremendous amount info on ball joints and tie rod ends here on the forum.

[mmiddle]

Originally Posted by picklito

That sounds like a great project. I've been out of trucks for a while, so my memory of parts and swapping is a little rusty.

I did have a 77 2wd and for my use brakes like that would be fine. Is there a reason I can't get 73-87-ish spindles onto my stock control arms and then just use all stock single-piston calipers, dust shields, etc.? Aren't those 11.5" discs?

Yes you can do this, but you will be 5 lug, unless you redrill the rotors.

using the 88-92 3/4 ton 6 lug rotors retains the well... 6 lugs.

There are a lot of options that we have thanks to GM's mastery of standardization. The kits offered are a great way to go because everything is new and in one box. But if you are ok with used parts and or sourcing everything individually then the parts are all of the shelf stuff. The advantage to the 6 lug kit offerings is that the studs are 7/16" rather than 9/16"/14mm. The down side is, if you trash a rotor they are more than $100 and have to be ordered plus shipping. But then again rotors can last the life of the truck.

The cost is about a wash either way. It all really depends on what is best for you.

[ksbrktracer]

Originally Posted by picklito

That sounds like a great project. I've been out of trucks for a while, so my memory of parts and swapping is a little rusty.

I did have a 77 2wd and for my use brakes like that would be fine. Is there a reason I can't get 73-87-ish spindles onto my stock control arms and then just use all stock single-piston calipers, dust shields, etc.? Aren't those 11.5" discs?

This can be done with all oem parts ,ball joints etc, no modding wheels , factory rallys fit just like they are supposed to, Can also get a 6-lug rotor to replace the 5-lug, YES you would have to order it if you ruined one ..... but when was the last time you did that , I just measured factory 1.25" rotor and it measure 12" across. 6-lug (12" accross ) rotor uses stock caliper, wheel bearings, seals etc ...... NO odd or hybrid parts. The only piece you couldnt walk into Oreillys and get would be the rotor and the last time I needed those was when the truck had 180,000 miles.

I like the bucks down approach ..... nothing wrong with it ...... BUT I like beig able to just bolt it together and go the most ....