Brake line size going to rear, does it matter???

[firecatwilson]

I have two questions I'm hoping to get answered... I'm replacing all my brakes and brake lines in my 1971 Nova build. Currently swapping everything, lines (3/16 Copper/Tin), master (ACDelco 18M974), booster (Tuff Stuff), C5 Disk's all around.

First is, I noticed I have bigger line (7/16th's?) going to the rear brakes then splitting to 2 lines which are 3/16th's, one for R and L. They used to be drums, swapping them for a KORE3 disk kit. Would the correct way be to replace them with the bigger line? Or can I just run 3/16th's all the way back like I have on the fronts and then split it?

Secondly, factory lines have the big curly cues in the lines by the master. I noticed on many build's no one does that anymore. What is the reasoning behind it and why should or shouldn't I do that now.

Thanks.

[Motorcitydak]

That coil is for some wiggle room when installing and also in case the master flexes any when the brakes are pushed, the hard line is less likely to crack if it has all that length to spread the movement over. To an OEM it's a good way to avoid huge lawsuits from failed brakes. On these cars the lines are made to custom fit usually and hopefully inspected regularly for any issues.

As for size, drums use more fluid that discs I believe so the size may be larger for that but it really does not matter or make a difference. 3/16 line and -3 fittings are the norm and really no reason to use anything different

[firecatwilson]

Thanks Steve.

[ixfn]

Yes; pressure vs volume. I'm would guess many that change from drum to disc don't bother changing the line size and get by just fine, but ideally you would want to replace the 1/4" line to 3/16".

[Apogee]

Six of one...half dozen of another. The advantages to the 1/4" line is that it's already there, but if you're replumbing the car anyway, then I would go 3/16" everywhere. Line size doesn't impact pressure or volume, as that is determined by the master cylinder and calipers. The only thing line size determines is fluid velocity based on the volumetric flow rate required, and as mentioned above, discs generally require less volume than drums for actuation. An added benefit of going with 3/16" lines is that they're slightly less compliant, meaning they expand less under pressure, than a similar material and wall thickness 1/4" hard line because their circumference is less.

Tobin
KORE3

[firecatwilson]

Sounds good Tobin. Thanks again for all your help.

[ixfn]

Sounds good Tobin. Thanks again for all your help.

Yes, thank you, Tobin!