3/16 or 1/4 in brake line for all drum brakes?

[64stpside]

I getting ready to start replacing the brake lines and have seen conflicting reports/opinions and brake line size. As Ive stated in other threads about my brake system, someone put a disc/drum booster, mc and prop valve from a early 70s truck on it. I had 3 different size brake lines on this truck.

Do I:

1. Install all 1/4 in lines?
2. Install all 3/16 in lines?
3.Install 1/4 in lines back to the rubber hose, then go to 3/16?
This is what I think is correct as I want to do a front disc conversion at some point and I believe the front lines need to be 1/4 for a disc system, unless a all drum system need the same size lines through out....

[chevy_mike]

Typically the rule of thumb is, disc use 3/16" and drums use 1/4". On my '65 Panel, the factory lines with 4 wheel drums was 1/4" to the front and 3/16" to the rear.

In either way, you must have the correct MC for your app. If you have 4 wheel drums, you need a drum only MC. If disc and drums, you need a disc/drum MC. 4 wheel disc, you need a disc only MC. That is three different MC depending on the application.

That said, if you know you are going to a disc/drum setup, I would run 3/16" front, 1/4" rear but still swap MC for the correct application. When you do your disc conversion, swap MC again.

[jocko]

Originally Posted by chevy_mike

On my '65 Panel, the factory lines with 4 wheel drums was 1/4" to the front and 3/16" to the rear.

just wanted to confirm - you had 3/16 going to the rear in a 65? My 66 had 1/4 all the way around (all drums), which is what I expected. I thought 3/16 line didn't come into play until disk/drum combos came into chev trucks in 71(?) Interesting.

Concur - gotta have the correct mc. I'd recommend do the whole thing all at once, even if it takes a little longer (i.e. to include front disk conversion now, rather than later - IF you plan to do one). That will guide your mc and line size choice. If disk/drum combo - 3/16 to front and 1/4 to rear is correct. If you're going to stay all drums forever(!) I'd personally do 1/4 lines all the way around (and a new mc for all drum systems - 67 impala mc is a good choice for this), power or manual depending on whether or not you have a booster, there is a difference in the mc's for power vs manual and 4 drum vs disk/drum).

[chevy_mike]

Originally Posted by jocko

just wanted to confirm - you had 3/16 going to the rear in a 65? My 66 had 1/4 all the way around (all drums), which is what I expected. I thought 3/16 line didn't come into play until disk/drum combos came into chev trucks in 71(?) Interesting.

I don't know if Panels are different than trucks but it surprised the heck out of me. There was the 1/4" line running across the crossmember and when to a tee. The pass front line was a 1/4" to the flex line. The rear line coming out of the tee is 3/16" and runs back to the rear flex line. Lines on the axle are 3/16". I don't know if they did this for a different brake bias due to more weight of the panel or what. Definitely different then my '68 which had 1/4" all around.

[frankslagoon]

Originally Posted by chevy_mike

I don't know if Panels are different than trucks but it surprised the heck out of me. There was the 1/4" line running across the crossmember and when to a tee. The pass front line was a 1/4" to the flex line. The rear line coming out of the tee is 3/16" and runs back to the rear flex line. Lines on the axle are 3/16". I don't know if they did this for a different brake bias due to more weight of the panel or what. Definitely different then my '68 which had 1/4" all around.

My 63 c10 is the same way. I,m pretty sure that's one way to keep the rears from lockin up before the fronts. I think we could run all 1/4 in and put a proportion valve to the rear also.

[61K10]

some have said on here that it doesn't matter what size. my 61 had 1/4 to both fronts and 1/4 back to the rear tee, then 3/16 to both rear wheels. drum brakes stock. I have added disc to the front, (with power booster and dual master/manual P-valve) and have 1/4 to the disc and 1/4 to the rear. stops perfect