Brake line size?

[Master X]

I just bought a dirt stock car and I noticed that the brake line running to the rear brakes is bigger than the front lines. Also the dual masters are 1" bores. Rear brakes are disc, does this sound right? I had some body tell me that this will give me more front brake than rear?????

Any help is appreciated!

[DaveBauerSS6]

I just bought a dirt stock car and I noticed that the brake line running to the rear brakes is bigger than the front lines. Also the dual masters are 1" bores. Rear brakes are disc, does this sound right? I had some body tell me that this will give me more front brake than rear?????

Any help is appreciated!

Front master should be 1 in and rear 7/8 in, with metric calipers on front and rear.

[SRXSRULE]

to answer your question about the line size and pressure.... Yes, larger dia rear brake line will reduce rear brake pressure and give the car more front balance.

Anytime you change caliper piston size, line size, master cylinder size you will change the pressure in the system. Eric

[Dirt Knife]

http://www.stockcarracing.com/techarticles/scrp_0412_race_car_brake_bias/viewall.html

[twizted]

I was just curious how a larger steel brake line lowers hydraulic pressure?

[Racer96m]

I was just curious how a larger steel brake line lowers hydraulic pressure?

More Volume = less pressure. Less volume = more pressure.

Dave

[harris44]

Easy way to explain is the garden hose affect! Put your thumb at the end of the hose and make the hole smaller you get more pressure, same with brake line.

[twizted]

Not meaning to sound like a a know it all but but in school I was taught Pascal's law and it says basically that pressure in a confined space is equal and undiminished in all directions. It's been a while since I was in a hydraulics class but everything they taught us in school says if you apply 100lbs to 1"piston on one end 100lbs of force will be present at the other end.

However your saying there is a noticable drop in pressure from say a 1/4" if you move up to a 3/8" thats very interesting. Think I need to request some of my money back from college and have them remove Pascal's law from the text books if it's wrong. Do you have a formula for the loss of pressure as the size of pipe increases? This info I need.

If you reduce piston size in the rear that would reduce pressure applied to the pads.

[twizted]

I know Jeff I thought about you as I was hitting the enter key but if i'm wrong I am gonna have a long talk with at least one teacher!

Side not saw a few clips of you in texas there was another car similar to yours I thought that was funny but looked like you were fast but you got tangled up in something or hung on the outside. Gonna step away from the keyboard now.

[return to dirt]

like twizted said, the m/c will displace x amount of fluid, the caliper piston will move y amount of distance regardless of line size. however too small a line may act as a restriction and slow down the rate of movement by the caliper piston but the final pressure at the caliper will be the same.

olin

[Egoracing]

The larger line size will transfer more volume to the rear than the front. Used to see it alot with drum brakes on the rear. You can use the amount of fluid transfer to adjust bias. Pressure being equal on the master cylinder end the line size will slow down the rate at which the pressure is applied. Larger will transfer more and a smaller line will transfer less.

[SRXSRULE]

My first statement can be missleading. dual master cylinders also effect this. If your running a single master and no bias you can tune the brake system with different size line. I have a brake pressure test kit that has two seperate gauges that will either thread into a bleeder to measure pressure of go in place of a brake pad. I used this tool to "adjust" the brakes on my IMCA hobby stock where no brake bias is allowed. It was done with different size line. This was on disk front, drum rear. Eric

[craigerdesigns]

Not meaning to sound like a a know it all but but in school I was taught Pascal's law and it says basically that pressure in a confined space is equal and undiminished in all directions. It's been a while since I was in a hydraulics class but everything they taught us in school says if you apply 100lbs to 1"piston on one end 100lbs of force will be present at the other end.

However your saying there is a noticable drop in pressure from say a 1/4" if you move up to a 3/8" thats very interesting. Think I need to request some of my money back from college and have them remove Pascal's law from the text books if it's wrong. Do you have a formula for the loss of pressure as the size of pipe increases? This info I need.

If you reduce piston size in the rear that would reduce pressure applied to the pads.

I think you are looking at the problem the wrong way. Don't look at it as force applied, it is the resistance to flow. A 1 inch piston moves 3 inches. This displaces a volume of fluid....about 2.36 cubic inches. This fluid is going to move through the brake line to the piston on the caliper. If the line is a bigger diameter it will take less pressure to move the same amount of fluid. It took less pressure to move that 1inch piston 3 inches. We did not violate pascal's law, it is applying that law.

[twizted]

Craiger, not exactly sure I understand you responce to me? I dont think anything in my post implied I was try to work outside pascal's law? I was basically listing info we learned in basic hydraulics. You can put 5" hard lines but you will still have the restiction at the connections at master and slave. These holes will usually be smaller than any line in system I am sure. These holes will act like an orfice tube in the system and limit/slow speed or flow but will still not limit final pessure. Have you ever looked at the size of hard lines on auto lifts? We have a older challenger and the hard line from the pump is aprox 3/8" ID and that feeds both cylinders to lift 8000 lbs. Aslo one note if ever want to know which line is suction and which is pressure to cylinders? The small line will most always be the high pressure line runnnig 2000lbs.

Anyway before anyone starts fitting 1" brake lines made from black pipe to there car go to youtube and search pascals law or hydraulic principals i am sure you find alot of good info. Like I said if you think a AN-4 line will lower pressure look into the outlet port of the master at the size of the hole. Anyway i'm done here and going back to what we do every night TRY TO TAKE OVER THE WORLD!!!! dont listen to me google it!

[Egoracing]

You can get lines that have a smaller inside diameter than the fittings on the master cylinder so the MC fitting is not the restriction.

[craigerdesigns]

Craiger, not exactly sure I understand you responce to me? I dont think anything in my post implied I was try to work outside pascal's law? I was basically listing info we learned in basic hydraulics. You can put 5" hard lines but you will still have the restiction at the connections at master and slave. These holes will usually be smaller than any line in system I am sure. These holes will act like an orfice tube in the system and limit/slow speed or flow but will still not limit final pessure. Have you ever looked at the size of hard lines on auto lifts? We have a older challenger and the hard line from the pump is aprox 3/8" ID and that feeds both cylinders to lift 8000 lbs. Aslo one note if ever want to know which line is suction and which is pressure to cylinders? The small line will most always be the high pressure line runnnig 2000lbs.

Anyway before anyone starts fitting 1" brake lines made from black pipe to there car go to youtube and search pascals law or hydraulic principals i am sure you find alot of good info. Like I said if you think a AN-4 line will lower pressure look into the outlet port of the master at the size of the hole. Anyway i'm done here and going back to what we do every night TRY TO TAKE OVER THE WORLD!!!! dont listen to me google it!

I wasn't thinking about the orfice, but in my stock master cylinder application with 3/16 lines I run a bushing on the master to reduce to my 3/16 line. What I am focusing on is that a 3/8 line is less resistant to flow than a 3/16 line. I know there are other factors but if everything else is the same it will take less force to move the same amount of fluid through a bigger line than a smaller line. The only way to know for sure is to set up a real world test, which is what one guy on here said he did. According to him it did make less pressure with the bigger line.