Fitting braided lines

[RedexRobB]

I bought one of these

http://cgi.ebay.co.uk/Mityvac-One-Man-B ... dZViewItem

No idea why the other doesnt need clamping, its how i do mine and they work 100%.

[Scott221]

If your on a budget you could always use one of these:

http://cgi.ebay.co.uk/HENRY-HOOVER-HVR2 ... dZViewItem

[deviant]

just out of interest, why is it better? I've wondered why before but never come up with any obvious explanation.

I can only assume that its due to less restrictions thanks to omitting the splitter therefore reduced losses.

That doesn't really make sense to me from a fluid dynamics point of view. Or rather it might make sense from a fluid dynamics point of view but I don't consider this a fluid dynamics situation.

Putting the brakes on you aren't really moving a significant amount of fluid a significant distance, and once the pads contact the disc you aren't moving any fluid, just applying pressure using a basically incompressible fluid as a medium. I don't see how a splitter could introduce any pressure differential between master cylinder and caliper.

I'd also assume a splitter is basically rigid under the sorts of pressure you see in a braking system, whereas I expect even braided hoses expand a bit (and std hoses do a lot). If you assume you can apply an equal number of pressure at the master cylinder regardless of your hose setup. So surely a twin line setup that has 33% (ish) more hose length than a splitter setup would experience more losses due to hose expansion?

[RedexRobB]

Im only supposing here, but wouldnt there be more pressure in the line from the M/C to the splitter? Since its compressing fluid to go into both lines, it must be under twice as much pressure to deliver the same pressure to each line? So if you have two line setup the fluid pressure is distributed imediately to each line rather than two lines worth of pressure going through one line if the splitter were in place. If thats true then maybe most of the loss is in the line from the M/C to the splitter? I think that makes sense

[deviant]

Im only supposing here, but wouldnt there be more pressure in the line from the M/C to the splitter? Since its compressing fluid to go into both lines, it must be under twice as much pressure to deliver the same pressure to each line? So if you have two line setup the fluid pressure is distributed imediately to each line rather than two lines worth of pressure going through one line if the splitter were in place. If thats true then maybe most of the loss is in the line from the M/C to the splitter? I think that makes sense

'fraid not.

One of the fundamental principles of hydraulics [1] is that the pressure at any point in the fluid is the same[2], if it's not flowing anywhere. If it is flowing at a significant rate, then you will have less pressure at the end than at the start, because of losses in the pipe, but unless someone can convince me otherwise I don't think that is relevant to brake systems.


[1] Pascal's Law - http://en.wikipedia.org/wiki/Pascal%27s_Law
[2]Ignoring any effects due to height differences between various bits of the system, insignificant in this case.

[RedexRobB]

Hmmm, I was looking at it from an electronics point of view. For the same current to flow in two branches with equal resistance (the lines to each caliper from the splitter), twice the current exists before the branch (from M/C to splitter).

[rene]

reason why you dont use a spliter..

1.Its cheaper to have 2 long lines insted of 3 lines
2.Keep It Simple, why make it more complicated than it needs to be?

[Gemini]

have i started a debate?!

basically the last braided line set up i had was two lines straight from m/c.

if its a good enough set up for bike racers, its good enough for me

gem

[deviant]

Hmmm, I was looking at it from an electronics point of view.

I know. Bloody sparkies.

Actually the analogy holds (sort of) true, but again only if the fluid is moving at a significant rate. Current is after all a measure of flow rate.

If you took an electric circuit that represented a splitter, put 12V in at the 'master cylinder' and grounded the 'calipers'; then yes, while current was flowing you would have twice the current in the top section. And all other things being equal you would (probably) have more losses in your electrical circuit because it varies with the square of the current but only proportionally to the resistance[1].

However if you take your system and break the circuit so no current is flowing, then you don't care about the resistances in the various 'hoses'. All you know is that you have 12V between your master cylinder and your caliper. This is where the analogy doesn't hold between electronics and hydraulics.

[1] I'm assuming a uniform resistance per length of 'hose', so more total resistance in the 'two hose' setup. Despite that I think it would be more efficient electrically.

reason why you dont use a spliter..

1.Its cheaper to have 2 long lines insted of 3 lines

That's about the only convincing reason I've seen.

[Jamz]

Yup - cheaper and easier to have two lines!

In theory becasue there's more pipeage in the twin line kit, it's a disadvantage and more likely to have a bit of give in it. I doubt it would ever be a mesurable factor though.

Only advice I'll give to get a bit more bite after bleeding:

Lock tie your brake lever back to the bar and leave the top off (or at least open slightly) your reservoir overnight.

It can make the world of difference because however good your bleeding kit, the fluid could still drag some air down and the only way to get it out is to wait until it rises to the top!

It's an easy job but really -ing annoying! :smt013

[Gemini]

yeah i did that last time jamz and it took the spongy-ness out of the lever.

i also heard someone on here say they hold their calipers in the air when they bleed their brakes as is obvious that air rises

gem

[deviant]

i also heard someone on here say they hold their calipers in the air when they bleed their brakes as is obvious that air rises

gem

I did that with the GPz last time cos I had the whole system off the bike. Not so practical if you are bleeding them in situ!

[wonderpupp]

Braided lines - absolute doddle -

1) Ride into bournemouth kawasaki
2) tell them you want braided lines on by lunchtime
3) ride out on their ZX10R demo bike
4) Forget to drop it back till the next day - was so busy at work I couldn't take a lunch break...


He he he heeee.

[rene]

how much did they set you back getting them to fit them?

one of the best bits of advice i can give for bleeding brakes is get a syringe, put it on the bleed nipel, suck the brake fluid though then presurise with the leaver SORTED, honestly a completly new/dry system took no more than 5 mins from start to finish with it

[Scott221]

Well ive just pulled off a little trick that works nicely, if your brakes are shite, unscrew the MC cap and rest it over the cyclinder in a way that air can escape, Zip tie yor brake leaver as far back as you can and leave it over night. I did it to mine last night and they were hard as nails this morning! Now i have brakes!:D