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Rob Frankham wrote: ↑Thu Jun 17, 2021 5:30 am Earlier (pre Mono) machines have two seperate flexible lines, once to each caliper, which to my mind is a much better arrangement. I'm very tempted to retro fit a similar arrangement to my 'Mono

Rob

I don’t think I’d go that far.
Properly anchored, a steel line is much more durable.
A flex line requires periodic replacement.
And even with steel braided lines, there is some line expansion reducing braking power. With 2 long lines like on the R90S, you have double the amount of line expansion and chance of line failure.
A better alternative is to fabricate a steel line that goes over the fender. Yes, more of a hassle taking the fender off and doesn’t look as clean, but safer without the loss of braking feel or effectiveness.

Seth wrote: ↑Thu Jun 17, 2021 10:34 am

Rob Frankham wrote: ↑Thu Jun 17, 2021 5:30 am Earlier (pre Mono) machines have two seperate flexible lines, once to each caliper, which to my mind is a much better arrangement. I'm very tempted to retro fit a similar arrangement to my 'Mono

Rob

I don’t think I’d go that far.
Properly anchored, a steel line is much more durable.
A flex line requires periodic replacement.
And even with steel braided lines, there is some line expansion reducing braking power. With 2 long lines like on the R90S, you have double the amount of line expansion and chance of line failure.
A better alternative is to fabricate a steel line that goes over the fender. Yes, more of a hassle taking the fender off and doesn’t look as clean, but safer without the loss of braking feel or effectiveness.

I have twin lines on the /81 RS and it has never been an issue. Can't say it's something that I'd worry about...

Rob

Seth wrote: ↑Thu Jun 17, 2021 10:34 am

Rob Frankham wrote: ↑Thu Jun 17, 2021 5:30 am Earlier (pre Mono) machines have two seperate flexible lines, once to each caliper, which to my mind is a much better arrangement. I'm very tempted to retro fit a similar arrangement to my 'Mono

Rob

I don’t think I’d go that far.
Properly anchored, a steel line is much more durable.
A flex line requires periodic replacement.
And even with steel braided lines, there is some line expansion reducing braking power. With 2 long lines like on the R90S, you have double the amount of line expansion and chance of line failure.
A better alternative is to fabricate a steel line that goes over the fender. Yes, more of a hassle taking the fender off and doesn’t look as clean, but safer without the loss of braking feel or effectiveness.

Simply insuring that the stock in-between line is properly secured (inside or outside the fender) and periodically inspected should suffice. The 2 separate flex hoses is definitely NOT a better arrangement in any sensical way. Getting rid of the two hose system and installing a rigid in-between line would make sense. Less flex. Better feel. Less perishable parts.

I can't agree with that. A brake made up of only rigid lines (all else being equal) would be extremely 'wooden' and wouldn't improve the brake at all. To give a good progressive feel at the lever, you need some movement in the system. A 'wooden' brake is very easy to lock. Of course, 'feel' is somewhat subjective but I would go for a little movement ever time.

In practice, of course, a second good flexible brake line won't make a detectable difference in movement at the lever, will eliminate the vulnerable under mudguard pipe (without a visuall offensive pipe over the mudguard) and result in a system that is easier to bleed. It's one of the things I intend to do on my Mono RT (but not highest on the list since the current system works OK).

Rob

Rob F said:"A brake made up of only rigid lines (all else being equal) would be extremely 'wooden' and wouldn't improve the brake at all."To give a good progressive feel at the lever, you need some movement in the system. "

Disagree.
A brake (system) made up of only rigid lines (all else being equal) would be IDEAL.
The ONLY reason flexible lines even came to exist at all in hydraulic brake systems is to allow steering and suspension movement. Period. No other reason.
I can think of no example where 'more flex' has been deliberately 'engineered' into a hydraulic system to enhance 'feel'.
Quite the opposite. Engineers and manufacturers presently go to every extreme to totally eliminate flexing in their hydraulic systems; reinforced braided lines, radial mount calipers, and so on. Flex is simply an unintentional by-product of engineering and manufacturing shortcomings.

The feel, braking power and operator effort of any system are the combined results of many things: the ratio of the master cylinder bore vs. caliper bore, and actuator pivot and leverage points, friction materials and (unintentional) flex.

If you are not comfortable with how hard (or wooden) your brake lever feels, or if it is too far away from your handlebar to modulate precisely while braking and you personally feel that more more 'flex' or 'sponginess' is the solution(???) for you, don't add more flexible hoses. Just don't bleed all the air out. Air compresses, fluid doesn't. You'll get the same effect.
And air is free.

Adjustable levers (some with variable pivot points) exist so brakes can be 'tuned' for the individual rider, depending on their hand size and strength. I haven't seen any direct fits for our relic airheads.

As far as the rigid line between calipers, the very few actual failures (or near failures) I have seen were caused by sloppy wheel or caliper servicing. I've never seen one damaged by road debris or outside projectiles.

Wellm we're going to have to disagree on that one... All I will say is that the stock set up on a mono RT already has about 2 feet of flexible hose and it works fine... The twin brakes on all pre mono airheads have twin flexible hoses and work just fine. Most bikes with twin front discs have twin flexible hoses and they work just fine... all of these engineers who go to such great lengths to 'totally eliminate flexing in their hydraulic systems' must work elsewhere than in the bike industry.

Rob

They work "fine" is a very subjective statement.
Rob F said: "All I will say is that the stock set up on a mono RT already has about 2 feet of flexible hose and it works fine... The twin brakes on all pre mono airheads have twin flexible hoses and work just fine. Most bikes with twin front discs have twin flexible hoses and they work just fine..."
When I was a kid I had a Rupp mini-bike, with only a rear brake. It was a pedal activated metal plate that rubbed against the back tire. It worked fine.
All kidding aside, all our old bikes have really lowsy brakes compared to what's out there now. A bit more flex here or there won't really affect our lap commute times. It's purely academic.
Two fingers exerting very little pressure on the front brake is all that's needed to 'stoppie' any modern sport bike.
Grab a fistful and you'll flip over forwards....but overall, they work fine.

Rob F said: " all of these engineers who go to such great lengths to 'totally eliminate flexing in their hydraulic systems' must work elsewhere than in the bike industry.
Brembo has many qualified (the world's best?) engineers in the bike industry. For decades they have been striving to eliminate flex, not introduce it.

gspd wrote: ↑Sat Jun 19, 2021 6:34 pm
Two fingers exerting very little pressure on the front brake is all that's needed to 'stoppie' any modern sport bike.
Grab a fistful and you'll flip over forwards....but overall, they work fine.

Basic Hydraulics... the pressure applied at the lever the the master to produce a given pressure at the slave and, therefore, a given braking effect is not affected, all other things being equal, by the amount of movement in the lever.

Also, I'm sorry if it offends your sensiblilties but I don't class a brake that will cause you to 'flip over forwards' as a good brake that works fine.

Rob

Rob Frankham wrote: ↑Sun Jun 20, 2021 5:14 am Also, I'm sorry if it offends your sensiblilties but I don't class a brake that will cause you to 'flip over forwards' as a good brake that works fine.

So, in your opinion, every new sport bike has brakes that don't work fine?
These super-brakes do not cause you to 'flip over forwards' per se.
Hamfistedness and lack of experience cause that.

I don't 'fit' on sportbikes well, too cramped, I'm too tall for their ergonomics.
But all of you really should expand your horizons and do yourself a favour and at least test ride a S1000rr or something similar just to experience what they're like. I think you'll agree afterwards that it was one of your life's most visceral experiences.
Two finger pressure carefully applied on the front brake lever will predictably and safely lift the back wheel even at triple digit speeds.
The front lifts just as easily at will while accelerating at any speed you choose. These damn things reach 100mph (in first gear) in about 6 seconds.. and all this can be done with relative ease if the electronic traction and wheelie controls are activated. My main concern when riding them is losing my licence.

That said, after a few miles on a rocket bike I'm happy to get back to the comfort of my 'John Deere Lazy-Boy' PD tractor.
Maybe I'm getting too old.