Starting to regret disc brake conversion

[tdangle]

I purchased a conversion kit from POL for my 70 C20. Getting ready to install and preinstall research is making me question my decision.

1. Some say the brake line position at the back of the a-arm is a problem
2. Had to get a new M/C (bore is 1 1/4) and new booster (11" dual)
3. New proportioning valve and will have to make hard lines between M/C and P/V (no one makes a set that works.
4. Figure out brake line from P/V to existing lines as they won't line up
5. Now I find out I'll need new lug nuts for the front and they will be different than the rear.
6. I'll basically be rebuilding the front suspension.

Most of all, everyone sells everything you need for C10, but not C20 and apparently there is some differences.

Hopefully is stops on a dime

[Steeveedee]

I bought the kit for my '70 C20 from POL. Missing parts (vacuum hose), damaged parts (caps and bearing seals), which were never taken care of even after a lot of back and forth. But the major parts were all there for the conversion, when I did it about 5 years ago. It was hard work for this old man to change out the parts, but the truck does stop better.

I did discover that the disc brakes took larger nuts the hard way, but that's no big deal. Just carry a wrench that fits both size of nuts.

[tdangle]

When I did an inventory of the package, everything seemed to be there and in good shape. I didn't buy a M/C booster package from them, because it really wasn't for a C20. I found out the bore is 1 1/4 for a C20 and 1" for C10. Also single diaphragm booster 11" for C10 vs Dual diaphragm 11" for a C20. Guess everything is a little heavier for a C20, The C10 stuff probably would have worked OK.

Have you had any issues the the routing of the brake lines behind the a-arm vs in front as the factory did for the 71-72 trucks.

Hopefully I won't have issues with the 9/16" studs and my aftermarket wheels.

[Steeveedee]

I hunted all over for front flex lines. I ended up buying the '73 up longer flex lines and doing a custom routing. In about 5 more years when those flex lines are aging out, I'll run new metal lines to the front of the a-arms like the '71-'72 model years did it. If the original steel lines develop a leak before then, I'll replace them along with all new brake lines. Here in the desert, we can get away with that.

[Smitty]

Check with Inline tube. See if they are able to help you.

[RichardJ]

No on wants mixed lug sizes. Some go ahead and switch the rears to 9/16" and I understand that. I took the easy route and switched the front to 1/2". I didn't want to buy 16 or even 32 lug nuts for the 16.5" slotted mags when I knew I would eventually switch to 17" and hub-centric wheels was a priority. 1/2' lugs are more than adequate with hub-centric wheels.

Using '73 and up disc, MC, brake lines and combo-valve is a no brainer in my opinion.

There is a brake line connector in the frame rail, under the pass side seat. That coupler is the same for '67-'72 and for '73-'90.

Everything from that coupler forward on my '67 GMC 3/4 came from a '76 3/4 GMC. If I need any replacement brake or suspension parts for the front, I go to the parts store or truck catalogue and get '76 parts.

[lil hoodlum]

Not for a C20 but for a 1968 C10 that I own, I did the disc brake conversion but kept it 6 lug manual disc... I also kept the hard brake lines on the back of the crossmember, haven't run into any problems in the 15 years or so.

My 1968 C20 that I bought in November of last year was already converted and so very thankful for that. The hard line are still in the rear of the crossmember though and 8 lug...

I used McGauphy's for the brake parts for the C10.

[Accelo]

"Have you had any issues the the routing of the brake lines behind the a-arm vs in front as the factory did for the 71-72 trucks."

I believe you could go either way, in front or in back of the cross member.
The easiest way is to use the rear lines like factory drum brakes.
One important reason to use the rear lines is your cross member doesn't have the clips needed to retain the hose in the front. To go with the front lines you need to add this clip. You need to purchase the lines and installing them under the motor mount is no easy job with a motor installed.

Most conversion kits would reuse the existing lines. (If indeed they planed anything). From the factory the 3/4T truck required longer flex lines than the half ton. I went through three sets of hoses till I found one that would work and not rub. And yes I PURCHASED A KIT that came with lines. I swear unless you purchase a high end kit like Wilwood's Bolt-On and Conversion Brake Kit it's going to take some work and some luck.

I see you have read and commented on the post about the rear studs.

The job is a PITA but it's worth it. The job is lots easier with quality kits.

Rick

[firedemon]

once you have everything installed and working properly it will all be worth the trouble . stops better ease of maintenance cheaper to maintain . every project has those unexpected little costs

[tdangle]

Originally Posted by Smitty

Check with Inline tube. See if they are able to help you.

They actually say they do not have anything for C20 only C10's

[Big Kev-O]

I tried to use the hard lines kit that Inline Tube sells for C20s and it was totally wrong. The lines that connect the C20 master cylinder to the proportining/metering valve were not correct. I couldn't get any of the hard lines in the kit to fit. I ended up bending my own lines to connect the master cylinder to the prop valve and made new lines to connect the prop valve to the existing hard lines. My caliper flex lines are connected to the factory hard line in the rear of the cross member. I bought a used MAC brand double flare tool of ebay for $30. After a few youtube videos I was making decent flares.

It was a PITA but was a huge improvement.

[Reddeye]

I ended up finding hard lines that fit my '72 C20 made by Right Stuff at Jegs https://www.jegs.com/i/Right-Stuff/965/TKT7107/10002/-1 and braided stainless steel flex lines that were actually long enough at Speedway https://www.speedwaymotors.com/DOT-B...-20,36151.html