SS Brake lines

[mack]

Whats the outer diameter of the lines you guy's are using?

[DiverRay]

The outer and inner diameter DOES NOT MATTER!!!! Brakes work by using a master cylinder to push fluid to a caliper. The lines just transfer the force from one to the other. GO WITH THE FORCE LUKE! the diameter or volume of the line does not matter, as long as they do NOT expand with pressure.

[b.walker5]

The outer and inner diameter DOES NOT MATTER!!!!

Hmmmm... I agree that outer diameter doesnt matter, but I wonder if maybe, the inner diameter does to a degree.

Note that the figures used here are guesses, but for example if your brakes are, say, half worn and the caliper piston requires maybe 20cc's of fluid to push the piston out far enough, and you only have 1/8" lines then the master cylinder has to overcome the line resistance as well as fill the caliper which must increase the required lever pressure, whereas, say, 3/8" line would have much less internal resistance and require less lever pressure to pump the same 20cc's from the master cylinder.

A smaller line is still going to transfer the same amount but a larger line is going to do it quicker with less effort, I think ????.... not that i'm any kind of expert in hydraulics, but try filling a bucket with a 1/2 inch garden hose and then a 1/4" tube. Still gonna do it but a lot slower. Does that make sense ?? or am I rambling ??

[psycoreefer]

Thing is your not filling a bucket because once the brakes are bled the whole system is "full" of fluid, your only using the fluid to transfer the pressure (force) generated by squeezing the lever to the brake pads, and that doesn't require moving much if any fluid, maybe .1cc's, not enough for the friction inside the line to matter.

[mack]

Feel

Ya, I just don't like the response I'm getting. It's been so long since I've ridden this but I don't remember having to pull the lever this far to feel the action. The SS lines are new but I was wondering if the size I have isn't better suited to a single caliper rather than a double. I understand the mechanics of how it works but I also believe that the diameter of the lines and the push volume of the mc would make a difference. I got a speed bleeder and I sucked a full quart through both sides and didn't see any bubbles.

[petejw]

Hi Mack,
Have you adjusted the lever with the adj screw?
that can make a big difference to the lever action
if theres to much free play?

[bikerphil]

Also, air bubbles can get trapped at the banjo bolt end of the MC if it's tilting upward when mounted on the handlebars. Cure for this is to remove the MC from the bike, point the banjo end down, and compress the caliper pistons a little to force those air bubbles back into the reservoir. Cover your gas tank before trying this, brake fluid eats paint. Might not be your problem, but it was for me.

[Incubus]

I cannot join the discussion about hydraulics without sounding stupid, so I won't. I can, however, say that I changed my 10.25mm OD stock rubber brake lines with 8mm OD braided steel brake lines with an equivalently smaller ID and improved my braking power immensely.

It took a while to g the new front lines to bleed properly, but once I did I have very good lever travel. I could not squeeze it to the handlebar if I wanted to.

What is the OD of the lines you installed, Mack?

Patrick

[shutchis]

-3 SS Brake Lines

Hi guys, I replaced my XJ11 stock rubber brake lines with -3 (3/16") universal stainless steel braided brake lines. I could tell a big improvement over Yamaha's '82 design; it was a good investment, both in time and expense. I made this modification in '05 so I've got a few years on the system and it's still working strong. I'll check my records and see if I can provide more details. Stay safe. Stan H.

[cywelchjr]

Brake fluid works much like a hose with water. If the line diameter is larger, then your moving more fluid to move the piston at the other end. If them line is smaller then your moving less fluid, but in application with brakes I don't believe enough fluid is being moved to have the inner diameter of the brake line matter, as others have said, it's having the line now swell under pressure that makes the measurable difference. Now, if you change the size of the piston on the other end, the game changes more. Remember that much of this is done by providing leverage, both by length of the lever pressing the upper piston (the MC) and the sizes of the pistons in relation to each other (a larger piston being motivated by a smaller gives more pressure but requires more motion of the smaller piston) it works like a fluid version of gears. My floor jack does the same basic thing, it uses a small piston to push fluid into the chamber of a larger diameter piston through a check valve to allow multiple pumps, brakes are the same without the check valve so you get on the amount of motion from a single pump, but then modern disk brakes actually have very little motion involved in providing braking power to the wheels.

[RS Thornton]

1/4"

Mack,
I think that is what you wanted to know. That is the OD of the ones from the splitter down to each front caliper, pretty sure all the pieces are the same size line.

For the other thread hijack let me add something:

GEEK ALERT!


While area is important to flow (Q=VA) so a lower area increases fluid velocity to achieve same flow (Q) and friction losses are increased with velocity increase, but this does not apply to brakes. Brakes are a pressure device not a flow device, F=PA, so force on the brake pads is related to system pressure and area of the caliper. Hence SS brakes are good because they are more rigid and do not expand as much under pressure, so more of the pressure created at the master gets transmitted to the calipers than with OEM rubber lines. I have no thesis on it but the danger on larger diameter brake lines is they would have larger min bend radius and could be more difficult to route.

Ride safe,
Scott