What do you guys run for brake hose diameters? AN -3 or -4 ?
I know some run the factory lines which is fine but for those who have fabbed their own lines when are you running?

 

-3

 

I mentioned I was planning to run -4 (bigger is better, right???) to a respected racing brake pro, He looked at me like I had 3 heads.... Once he quit laughing, he explained that you don't need much volume, and that the larger diameter of -4 gave more leverage on the line making it feel softer...

Everybody knows that :-)

 

3 for reasons above. It's not the diameter, it's the stiffness that matters . . . .

 

The corollary to that is all lines should be hard line except the shortest possible line needed that is ss braided line like to the calipers. Watch out for single flare hardline which is no bueno and ss lines that do not meet DOT standards but need not be DOT approved. DOT standards are quite extreme and not that easy for ss braided line to meet while rubber lines can easily for example the "whip test."

 

I used -2 lines on my race bike. I am kind of surprised that aren't used on cars too.

 

You using it on your car?
I tried -2 on my bike and did not like it at all, to stiff.

 

I misremembered. I used -2.5 lines (2.5mm I.D.) from Galfer on my race bike. I loved the -2.5 lines on my race bike. I had great relationship with Sandro from Galfer and always had custom 2 into 1 -2.5 lines made for whatever bike I was racing.

I have no idea what is on my race car. I would guess -3. Whatever they are, my brakes work great and I would not change them from what they are now.

 

AN -3 line is roughly 4.8mm in diameter. Most commonly used sized for fabricated lines in automotive that we have seen.

 

I have never seen -4 lines used for high pressure hydraulic lines on a purpose built race car.

From Formula Ford to GTP to 3-liter F1 (and every GT car, too).

Besides, the -4 is often lower pressure rated, elastomer tubing under the braid suitable for oil/fuel whereas the -3 is rated for MUCH higher pressure and uses harder Teflon tubing under the protective metal braid.

 

Disappointed. Thought my comment was very clever. Thank goodness I amuse myself.

On a serious point AN stands for "Army Navy" and was the mil spec developed for aviation. The number is 1/16s of an inch ID of the tubing. It's always a trade off of pressure resistance vs flow rate but for brakes, there is precious little flow, just transmission of pressure through relatively incompressible hydraulic fluid. A smaller diameter line is more rigid and less likely to swell. I did not know motorcycles had AN2 available, but makes sense. Lighter, stiffer and given what I bet are smaller volumes and surface areas in calipers due to small mass of the bike, even less need to accommodate flow. I wonder if any of the small sports racers or formula cars use or could benefit from AN2 lines?