Hardline brake size, it matter?

[ZZ4Blazer]

Upgrading to C6Z brakes on the front of my truck, 94 s-10. Stock front hardline is standard 3/16", 1/4" going to the rears

How much does the hardline size matter? Should I redo the front lines with 1/4" as well?

Im gonna be running a hydroboost booster, rear brakes are LS1 discs.

Im gonna have to redo my brake lines, once I decide which master cylinder to use, so now would be the time to redo the front lines if its needed.

Any thoughts?

[chicane67]

Line size does matter... very much so. However, I wouldnt do a 1/4 front line size... I would keep it 3/16. If you were to change anything, I might consider 3/16 for both front and rear... but only if you change out the rear's to the matching caliper units from the C6 Z06 package. 1/4 in the rear is ok for the small PBR single piston calipers used on the LS1.

FYI... The C5/6 and Z06 use the same line size front and rear. The LS1's do not.

I am running an upgrade to the factory C6/Z06 from APRacing ( 14" six/four, front/rear). The kit was specifically made for the existing brake system of the C5/6/Z06, to include the correct pressure to volume ratios associated with the factory system. That is what needs to ba paid attention to. You need to maintain the correct PV ratio for proper and safe operation. So in other words... the 3/16 front and 1/4 rear will work for your application and it now comes down to master selection... and the factory C5/6/Z06 master would do just the trick... even with the use of a Hydroboost. You will however, need to run an adjustable proportioning valve to the rear line.

You might want to look at this, which is available thru Doug Rippie Motorsports. It is made for the PV ratio C5/6/Z06 and has been set up for use with an adjustable valve:


With my brake selection, I wanted to mimic the factory set up and keep the correct PV ratio intact... so I had a rear line made in 3/16 to replace the factory 1/4 the chassis came with. This way, the master cylinders and other associated components from a (the) donor chassis, in this case the Y-body, are readily available.

I think you could get away with the 3/16 front and 1/4 rear as is. It all comes down to the master. I think it would be in your best interest to call Paul at Hydroboost and get his opinion as well.

[ZZ4Blazer]

Thank you much. I just happened to be browsing around, looking at different c5/6 brake stuff, and had saw that master before.

Although, $600 seems a bit steep for a master cylinder. I've only got $700 into the brake set up. I already have an adjustable prop valve plumbed into the rear line, and just my line lock in the front.

I would assume, using mostly corvette brake stuff, to match it with a corvette master. But, I've been wrong before. How much does chassis design and weight come into play, and effect the brake set up?

[Rick Dorion]

Tom, are you running hydroboost or a power setup?

[CarlC]

I had the stock 1/4" soft-steel line on mine using '93-'96 LT1 / Baer rear disks. With an adjustable proportioning valve I could not make the rear brakes lock. After changing to a self-bent stainless 3/16" line with AN fittings the rear brakes would lock.

Line pressures for stock early cars are about 2/3 that of modern C4/5/6 needs. 1/4" x 0.028" wall vs. 3/16" x 0.028" wall stainless tubing, 3/16" has +25% higher rated pressure rating.

If you are going to run a modern caliper and need a new brake lines, IMO the best bet is a 3/16" line.

[Bow Tie 67]

Ok, I have no idea why my head spins when I read this brake info. Is it safe to say I can use 3/16" line on the entire brake system? My system consists of Baer track ( C4 front calipers / rear pbr C4? ) C5 power master, and an adjustable proportioning valve. Will I also need a residual pressure valve for the rear?

[chicane67]

Tom, are you running hydroboost or a power setup?

Manual... with dual, individual masters.

Is it safe to say I can use 3/16" line on the entire brake system?

Yes.

Will I need a residual pressure valve for the rear?

No.

[Bow Tie 67]

Thank you, now can you send some warm weather to Chitown?

Matt

[MonzaRacer]

AS a tech I see lots of cobbled systems come in and then have to make it work without trashing a lot of parts. The big problem is a lot of people want to use the 1/4" line thinking you have to move more fluid, you dont, you have to build preasure quickly. Most people forget that brake pads only have to move thousandths of an inch where a drum brake set up needs a lot of fluid to move things hence the need for 1/4" line.
Most people really forget that disc brakes require preasure fast preasure response. When I was doing some diagnostics for GM while a line tech on an aggresive rear brake problem me and a brake engineer talked a lot. The othe tech thought thecars needed recalled for line replacement to smaller lines.So we got approval to replace all the 1/4" with 3/16" to the rears and it made for some crappy brakes.
So we put the originals back on and then, just for kicks I go buy an aftermarket shoe set and install them and then we found that the drums were over size from the factory. So we got the car braking properly then we broke it down and sent parts back to GM for inspection and testing. We got a response we figured after going over things, the lines were good , the shoes were WAY to aggresive a mix for the car. Line preasures in driums have to rise slowly ,were in a disc system they have to rise fast.
I have also learned that there is no performance difference between steel line and stainless line except that stainless wont rust or corrode, tends to be lighter, slightly, and has a benifit off being new over old stock stuff. The cost is the reason why the OE doesnt use it much.
Now braided stainless lines DO help as they dont flex under preasure like rubber lines.
Another thing is ,especially on pro touring cars, bleed your brake regularly. I know a few guys that bleed brakes before every race. Even when they use expensive high performance race fluid.
Probably some of the most economical high boiling point fluid I have ever use was from Performance Friction.
Another thing I found was that a lot of racing teams used to (way back when) have several master cylinders sleeved to different diameters to raise or lower the response from the system. While ballance was dependent on brake bias and tires and such they could taylor the pedal effort to the track condidtions. I usedthis on a Camaro that I help set up once we could not get it to work right and didnt have access to lots of brake info, WE had converted it to 70's Corvette brakes and hung the old 'Vette IRS under it too (talk about fun getting half shafts made) and used the 'Vette master cylinder too. WE had lots of problems with it so we bought a new master,, found it bored oversized and it really made a difference. We never had the formula till later on and then I figured out that the 1/16" difference in size dropped the preasures enough to tame the beast ,so to speak.
Then after talking to an old road racer told me why they did that and it makes very good sense, and works too.
The last i saw the Camaro it had some newer calipers and rotors but the owner couldnt get a master cylinder to make it work good(he had not changed the proportioning of the system or tires, just added newer parts)so I told him about our findings and he druagged the old master out ,had it rebuilt and it went back to working.
We figured the car didnt want the faster preasure rise time the smaller master cyl gave.
Just some info for the record. I have even helped set up old full met drum brakes for racing use and they did work very well and had to stop some very heave cars on very crappy tires.
One of the things that would help the newer trucks and cars would be getting some stainless flex lines installed and I have found the big reason why GM brakes feel crappy is because of the OE pads more than anything. Up gradeing the pads and properly refinishing the rotors on car go a long way in helping the braking capabilities.
A friend had one of the last Firebirds and we found some aftermarket pads that made the car stop on a dime. We put the same type of pads on his Tahoe and it made the same difference in braking. he just got done putting the new wheels and ART on the truck THEN we added brakes and he could actually drive it into corners a lot harder cause it would actually stop.
good luck and be safe when working on brakes.
Lee Abel
AFTERMARKET PERFORMANCE

[chicane67]

Thank you, now can you send some warm weather to Chitown?

Matt

Its in the mail.......