Serious question.

[Evil636]

The lines from the master cylinder to the calipers, how much free play is actually needed in the lines? Serious point, with the bike in a free state I.e suspended with front forks at full reach and the l8nes from the master cylinder reach the calipers without any intrusion then they are fine correct? They don't physically do anything more than up and down to that same point. Even when turning the master cylinder and forks etc are all in the same place regardless of lean or turn. So if a new set of lines is a nice fit (not stretched or any strain on the lines or joints) just without as much brake line donating or hanging free than normal then they are fine. Am I correct? I know I am mentally but why is the norm to have so much free line just hanging there? I'm asking because my new brakes are exactly as stated and I know in my head they are fine but it made me question it that's all.

[WizzBang]

Just a thought, but maybe it's to do with how they react when the forks compress.

[Evil636]

Good point. But if at there longest reach they aren't tight then surely when they are compressed from braking etc then they will just flex like a long line would. So theoretically it makes no difference.

[David W]

As long as there is zero tension in them when the forks are fully extended, and you can turn them lock to lock, you're alright.  Places to check are at the banjos.  Just make sure the hose is coming out of the banjo nice and straight before it naturally flexes.

[Andy M]

As long as there is zero tension in them when the forks are fully extended, and you can turn them lock to lock, you're alright.  Places to check are at the banjos.  Just make sure the hose is coming out of the banjo nice and straight before it naturally flexes.

this.
think a wheelie for example, fast unloading of the forks, you don't want the quick stretch of the line to cause any pressure at all on the banjo. a fairly rigid line for example, whilst having some free play to full extension, could pressure the banjo before the free play of the line stretches out enough (an extreme example but possible, and if it happens say several times could the banjo leak?)
there is also a top out spring in there which will extend the unloaded forks another 20mm or so which most people forget about when measuring for static and rider sag. I would go with full extension of forks, plus 20mm plus extra depending on how flexi the brake line is. Would add a bit more for a braided line over standard.

[Evil636]

Cheers for the info guys. Will keep it all in mind when I come to final fit everything.

[WizzBang]

Good point. But if at there longest reach they aren't tight then surely when they are compressed from braking etc then they will just flex like a long line would. So theoretically it makes no difference.

My thinking was.....if a standard length line bows outwards when static, it will bow out further once the forks compress.  If a short line has little or no natural bow when static, where does it flex when the forks compress (maybe in towards the wheel ?)