Disc Brake Upgrade Reference Thread

[rain_man]

so is it true that if you swap to disk brakes 6/5 lug that your organal wheels wont work any more?
if this is true why not just go to 5?
thanks

[Captainfab]

Thonly way you could use those '91 8 lug parts is if it is the Square body style. The Suburbans, and Crewcabs, ans possibly a couple other models were still the Square body thru '91. If it is the '88 and up body style, the only thing you might be able to use would be the rear differential. I'm not sure on the width of the 8 lug rear differentials of those years. I know that the 5 lug differentials are too wide to use in the older trucks. One other thing that you could use from it if it is a newer style truck, is the brake booster, master and prop valve, with one of my booster brackets. That will bolt right up to your '64 GMC.

Originally Posted by karlbenz

wow, this is a lot of info. I am confused(which usually doesn't take a whole lot) I am wanting to put 8lug on my front end of my 1/2 ton 64gmc. I have a 91 8lug truck sitting here that I can use for parts. can I use anything off it?

I have not done it, but I'm thinking that the C10 shafts and bushings would fit the C20 LCA's. But yeah if it were me I would upgrade to the '73-'87 control arms with the rubber bushings. I would also recommend upgrading to the larger LCA shaft U-bolts used in the '73-'87's.

Originally Posted by ChiefRocka

So....could I just use my existing C10 crossshafts on the C20 arms ?

Or, does it have to be '67-'86 in order to bolt to my 63' c10 X-Member ?

I think I would prefer to use newer style rubber bushing style arms anyway...keeping it 6-lug

[Captainfab]

If you have original style 6 lug wheels, they won't work with disc brakes. Some guys have aftermarket or later model 6 lug wheels that are disc brake compatable, so switching to 6 lug discs will allow keeping your wheels. Plus you wouldn't have to change your rear differential, or change the axles in your existing one, if you went with 6 lug discs up front.

Originally Posted by rain_man

so is it true that if you swap to disk brakes 6/5 lug that your organal wheels wont work any more?
if this is true why not just go to 5?
thanks

[rain_man]

thanks capt

[jocko]

Wow, what a thread. This is a very helpful one. Have seen several comments that discs will not fit the original 6 lug steelies. A couple questions -
1. Can a spacer be used to make the original 6 lugs work with a disc set-up (i.e. I've not tried it yet - where does the interference actually occur between the caliper and the original 6 lug wheel? is it a wheel diameter thing or backspacing thing, etc)
2. Captain Fab, you mentioned aftermarket and later model 6 lugs would work. Which later model 6 lugs? (all 88-up 1500's?) and what company makes stock-appearing steel wheels that will fit discs? (I've looked at stockton and a few others, but seems their stock looking wheels are not quite stock looking - they are missing the air gaps in between the wheel center and rim, at least on some of the wheels I've seen. Seems later model 6 lugs (88-up) were 16 inch rims? So are you saying that aftermarket steel wheels would also need to be 16 inch to work?

I've got 15 inch truck rallies also in addition to the stock steelies, and I'm pretty sure they will work - but I'm going to a bit of effort to just run steelies and poverty caps - looking for the simplest to keep that look yet eventually upgrade to front discs.

Thanks a lot folks, great thread.

[SCOTI]

Originally Posted by jocko

Wow, what a thread. This is a very helpful one. Have seen several comments that discs will not fit the original 6 lug steelies. A couple questions -
1. Can a spacer be used to make the original 6 lugs work with a disc set-up (i.e. I've not tried it yet - where does the interference actually occur between the caliper and the original 6 lug wheel? is it a wheel diameter thing or backspacing thing, etc)
2. Captain Fab, you mentioned aftermarket and later model 6 lugs would work. Which later model 6 lugs? (all 88-up 1500's?) and what company makes stock-appearing steel wheels that will fit discs? (I've looked at stockton and a few others, but seems their stock looking wheels are not quite stock looking - they are missing the air gaps in between the wheel center and rim, at least on some of the wheels I've seen. Seems later model 6 lugs (88-up) were 16 inch rims? So are you saying that aftermarket steel wheels would also need to be 16 inch to work?

I've got 15 inch truck rallies also in addition to the stock steelies, and I'm pretty sure they will work - but I'm going to a bit of effort to just run steelies and poverty caps - looking for the simplest to keep that look yet eventually upgrade to front discs.

Thanks a lot folks, great thread.

If your plan is steelies w/dog-dish (poverty) caps, the bolt pattern of the wheels won't be distinguishable.

I did a disc swap on my 68 & ran poverty caps on OE 5-lug truck wheels up front w/poverty caps on the OE 6-lug wheels for the rear for several months before swapping the rear axles to 5-lug.

If the concern is a spare that fits all 4 corners, Wheel Vintiques, Early Classic, & Stockton each make an OE appearing steelie in various sizes (they don't have to be 16's).

[jocko]

Thanks Scoti, that's good info. Good point about the 5 and 6 / front and back - not a big deal visually (but that spare thing..... I better find a jack too, I keep forgetting to pick one up - then I can worry about tires). Also, thanks for the 15 inch info.

[raycow]

To add to the wheel discussion, you might want to look at factory wheels from a 71-up K-10. These trucks had disc brakes with 6 lugs, and at least some of them had 15" wheels.

Ray

[jocko]

would it be the correct bolt circle? that's a great idea, had not thought of that, but they would clear discs. You might be onto something there.. Seems most of them had rallies on them that I have seen, but I think that's because folks PUT them on afterward in many cases - I know I've seen some K10s with steelies.

[SCOTI]

Originally Posted by jocko

would it be the correct bolt circle? that's a great idea, had not thought of that, but they would clear discs. You might be onto something there.. Seems most of them had rallies on them that I have seen, but I think that's because folks PUT them on afterward in many cases - I know I've seen some K10s with steelies.

Yes, some later model 4x4's came w/6-lug steelies (lots of military Blazers did)..... They are very elusive though as more than one board member has searched for months trying to find them w/o luck. When they do pop up, it becomes a timing thing. Or, you can buy them new from the aftermarket when you're ready.

[ozman3803]

I've looked this over a couple times and maybe still missed it. My 70 2wd has 6 lug disc. On the part swap from 6 to 5, what thickness of 5 lug rotor (1 1/4?) is needed and will this work with the current disc brake caliper?

[Captainfab]

If your '70 has 6 lug discs up front, they aren't original. They could be either aftermarket rotors for the '71-'87 spindles (I believe those are the 1 1/4" rotors) or they are the '88-'98 light duty 2500 series rotors, spindles and calipers. In light of those possibilities, I would suggest taking a few pics of what you have (particularily the calipers) and post them here, and we can determine which front disc's you have. The parts are not interchangeable between the two options I listed.

Originally Posted by ozman3803

I've looked this over a couple times and maybe still missed it. My 70 2wd has 6 lug disc. On the part swap from 6 to 5, what thickness of 5 lug rotor (1 1/4?) is needed and will this work with the current disc brake caliper?

[ozman3803]

Cool, I figured they had just use a 71+ front end. I'll try to get some pictures up soon, thanks for the help.

[laid_out_70]

got some c20 questions. i have a 70. what is the required to swap to disc up front and would like to run drop spindles. would just rather swap to 1/2 ton specs but i dont want to search for a rear end. thanks in advance

[SCOTI]

Originally Posted by laid_out_70

got some c20 questions. i have a 70. what is the required to swap to disc up front and would like to run drop spindles. would just rather swap to 1/2 ton specs but i dont want to search for a rear end. thanks in advance

Front is standard swap: Use 71-87 front parts. 73-87's are easier to find in wrecking yards if you plan a budget approach vs. buying a kit from a vendor.

The rear is going to require swapping..... thus some searching for the replacement. If it's a rear coil truck, 71-72 5-lug housings are a direct swap. 67-70 6-lug housings are 1.5" narrower than 71-72 housings & can have aftermarket 5-lug axles/drums swapped in. 73-87 housings are wider like the 71-72's. These will require more effort for the swap depending again on rear suspension type.

[Sick5]

Nice thread!
i have a 84 full front clip i rather just use the a arms and drop spindels from it
and keep the assit power steering.. is it possible? will the 65 tie rods be a issue hooking up to a new drop spindel

[SCOTI]

Originally Posted by Sick5

Nice thread!
i have a 84 full front clip i rather just use the a arms and drop spindels from it
and keep the assit power steering.. is it possible? will the 65 tie rods be a issue hooking up to a new drop spindel

They won't be a direct bolt-up deal. You'll need 73-87 steering parts or the tie-rod adapters previously mentioned to go from 65 to post-73 spindles.

[fryer1979]

Great thread with a lot of excellent info. Bookmarking for reference for my own upcoming swap.

[Sick5]

Originally Posted by SCOTI

They won't be a direct bolt-up deal. You'll need 73-87 steering parts or the tie-rod adapters previously mentioned to go from 65 to post-73 spindles.

If I use my steering parts will still be able to use the assist or will have to upgrade the steering box

[SCOTI]

Originally Posted by Sick5

If I use my steering parts will still be able to use the assist or will have to upgrade the steering box

I can't say for sure. I would guess you'll get better results w/the later model power steering.

[raycow]

Originally Posted by Sick5

If I use my steering parts will still be able to use the assist or will have to upgrade the steering box

If you have an external PS cylinder that connects to the center link and want to keep it, you will need to use the aftermarket tie rod adapter sleeves. The alternative would be to find a machine shop that knows how to properly ream the tapered holes in the center link to accept the later tie rod ends.

Ray

[Sick5]

Originally Posted by raycow

If you have an external PS cylinder that connects to the center link and want to keep it, you will need to use the aftermarket tie rod adapter sleeves. The alternative would be to find a machine shop that knows how to properly ream the tapered holes in the center link to accept the later tie rod ends.

Ray

never mind i rather just oder the plate from
CAPTAINFAB.....

HEy CAPTAINFAB im going to be sending you some paypal cash tomorrow!!!
need the power steering bracket and brake bracket

[ljackson]

My son and I put the parts from an ’81 GMC under the 64 on the original cross member. Everything went pretty smooth. One thing to look out for, when drilling the holes out for the 9/16 U bolts, be sure to keep the bit from wandering toward the cross member. We had 2 holes that we had to wrench because we could not get a socket on them. We used the booster and MC from the ’81. We also reused all of the front brake lines. We disconnected the line on the going to the rear underneath the cab. The lines going to the front brakes will use the oval holes in front of the cross member. We used some new ¼” lines going to the back. 1, 51” long and 1, 12” line and 2 couplers. I bought a ¼ to 3/16 adapter but I did not need it. The original rear brake hose had a 3/16 double flare. The hose that I got from O’reilly’s that was supposed to be for the ’64 had a ¼ fitting. The numbers are: Brake Best BH401640. The box also reads that this number replaces DOR BH36502 and RAY 36502.

The truck sits a little higher now in the front. I suppose due to the old springs sagging. We haven’t done the back yet. Also it turns tighter to the left than the right. Do you know if I have something wrong? I may trim the right stop.

I couldn't find my pics. I'll take more and post them later.

[nomrlz]

so, if this donor 85 truck i have access to has 1" rotors. the front suspension and brakes are useless to me on the 66

[Captainfab]

Not completely, unless you don't want to upgrade the upper and lower control arms. The 1" rotor brakes will still be a big improvement over the drums. Of course if you can find a suspension with the 1.250 rotors that would be the way to go. But if you can't find one, you can install this suspension and always upgrade later on.

Originally Posted by nomrlz

so, if this donor 85 truck i have access to has 1" rotors. the front suspension and brakes are useless to me on the 66