Firmer than expected front brake lever after Spiegler installation

[FJ_Hooligan]

I've seen this discussion many times.  My main question is: What is the forcing function that's pushing air/water INTO a closed system?

I can maybe see a bad seal on the master cylinder gasket allowing ambient air to somehow find its way into the reservoir.  There is on outside pressure forcing moisture passed the seals into the system.

If anything, the pressure generated during braking should work to force fluid/moisture/air out of the system.

I can see where an H2O molecule is smaller than an O2 molecule, but it's not like they are constantly attempting to push themselves into the braking system.

I don't intentionally ride in the rain but have been caught in it numerous times with no ill effect to my hydraulic systems,

Just providing my long term observations and experience with DOT5.  I've had it in my '85 since about 1987.  When I got my '93 in 2000, one of the first things I did was convert all the hydraulics to DOT5.  I did have to put new seals in the front calipers several years ago, but unless Joe Berk has changed it back or flushed it recently, that original fluid is still in the rear brake and clutch.

Maybe with DOT3/4 being hydroscopic, they attract moisture.  DOT5 being hydrophobic doesn't "pull" moisture into the system

[fj1289]

Once again, such an easy lead in for Klavdy ....

[FJ_Hooligan]

I've seen this discussion many times.  My main question is: What is the forcing function that's pushing air/water INTO a closed system?

I can maybe see a bad seal on the master cylinder gasket allowing ambient air to somehow find its way into the reservoir.  There is no outside pressure forcing moisture passed the seals into the system.

If anything, the pressure generated during braking should work to force fluid/moisture/air out of the system.

I can see where an H2O molecule is smaller than an O2 molecule, but it's not like they are constantly attempting to push themselves into the braking system.

I don't intentionally ride in the rain but have been caught in it numerous times with no ill effect to my hydraulic systems,

Just providing my long term observations and experience with DOT5.  I've had it in my '85 since about 1987.  When I got my '93 in 2000, one of the first things I did was convert all the hydraulics to DOT5.  I did have to put new seals in the front calipers several years ago, but unless Joe Berk has changed it back or flushed it recently, that original fluid is still in the rear brake and clutch.

Maybe with DOT3/4 being hydroscopic, they attract moisture.  DOT5 being hydrophobic doesn't "pull" moisture into the system

edited

[FJ_Hooligan]

Once again, such an easy lead in for Klavdy ....

How's that?

[fj1289]

Once again, such an easy lead in for Klavdy ....

How's that?

"Firmer than expected..."

[Charlie-brm]

While we've got you on the subject, does the brake lever mount on to the FJR master differently? I have a new set of levers on a stock FJ1100 clutch and brake, and it would nice not to have to lose the use of them.

No reason to buy new $$$$
Buy them used on FleaBay....they are plentiful and cheap

For example FJR https://www.ebay.com/itm/FJR-1300-Front-Brake-Master-Cylinder-from-2004-Yamaha-/353069289269

FZ1: https://www.ebay.com/itm/2006-Yamaha-FZ1-front-master-cylinder-lever-/273177297614

I think you will like the smaller 14mm m/c off the FZ1 the best.


If you are worried about buying used...buy a rebuild kit and replace the seals...and call it a day.

Cheers

[Pat Conlon]

Apples to oranges. IIRC years ago someone tried buying the adjustable FJR levers to use on the stock FJ m/c's and reported that they would not fit...
If you are getting a FJR or a FZ-1 m/c, I don't know why you would even consider using the stock FJ lever when the FJR/FZ-1 levers are adjustable.

[2big]

No reason to buy new $$$$
Buy them used on FleaBay....they are plentiful and cheap

For example FJR https://www.ebay.com/itm/FJR-1300-Front-Brake-Master-Cylinder-from-2004-Yamaha-/353069289269

FZ1: https://www.ebay.com/itm/2006-Yamaha-FZ1-front-master-cylinder-lever-/273177297614

I think you will like the smaller 14mm m/c off the FZ1 the best.


If you are worried about buying used...buy a rebuild kit and replace the seals...and call it a day.

Cheers

Hi Pat, are you saying the smaller the diameter the better the feel? I thought in this instance more is more?

I tried to fit a 19mm Nissin radial calliper off a GSXR 600/750. Looked awesome but the brake line fixing bolt came out the bottom and fouled the bar riser; meant I had to rotate it back - not good ergonomics for wrists.

Im dropping the ABS - I want a calliper that looks conventional but gives the strongest brakes (2 finger stoppies!) , in conjunction with blue spots, braided lines and new wavy disks?

[Pat Conlon]

Hey Jan, yes, the smaller the piston in the m/c 1) the longer the lever travel to move that same amount of brake fluid and 2) the smaller piston pushes harder with the same lever pressure (all things being equal)
I say "all things being equal" meaning a comparison between m/c's that are the same design and have roughly the same pivot ratio on the lever.

FJ's, FJR's, FZ-1's use old school axial m/c's with internal reservoirs.
Radial m/c's are a different breed. They come in different piston diameters and lever ratios to fit whatever application you choose. Entirely possible to have a radial m/c 19mm piston with a softer feel because the lever ratio is different.  Like you, I am not a fan of the urine cups on a radial m/c...
*but*
There is no doubt that they are a superior design to the axial m/c's.

IMHO the best value and sweet spot for 2 finger braking on our FJ's is the 14mm axial m/c, Spiegler lines and R-1 mono block calipers with HH pads. It's really quite nice.

Of course, there are better brake systems available out there. I would love to try a radial m/c on my '84.
Perhaps with a polished aluminum urine cup?

Cheers

[Millietant]

I'm with Pat on this, I love the brakes on my FJ, set up pretty much the way Pat describes - Spiegler lines aren't really available over here, but Earls Performance do great lines at decent prices - They're based at Silverstone Jan (just outside the track) and with a phone call, you can arrange to ride down and collect (if they're open through lockdown).

[2big]

Cheers Chaps
Makes sense - any particular models to source from? Fazer, FZ1 /6, FJ1300 - any preference for Brembo or Nissin?
How about a Rizoma 'pot' - same as your mirrors Pat. Lush CNC billet machined quality and fits the FJ with a discrete black anodised finish
https://www.rizoma.com/universal/fluid-tanks/ct027/en

[Pat Conlon]

I think the best axial m/c 's I recall were called Cobapress, made by a French firm called Beringer. They use a special roller bearing that enhanced the feel of right angle lever action.
You can spend thousands of dollars on your system.

Practice practice practice....and practice some more.

[FJ_Hooligan]

Hey Jan, yes, the smaller the piston in the m/c 1) the longer the lever travel to move that same amount of brake fluid and 2) the smaller piston pushes harder with the same lever pressure (all things being equal)

Sorry Padre, I'll have to clean that up a bit.

Force is applied at the lever and is converted to a fluid pressure by the master cylinder piston.  The pressure comes from applying the lever/piston force (lb) over the area of the m/c piston (sq in).  Thus the pressure (lb/sq in). 

If more lever force is applied, the pressure increases.  If the piston area is reduced, the force is applied over less area and the pressure also goes up.  This comes at the loss of total fluid delivery so you have to watch going too far or the lever will come all the way back to the bar.

Opinion:  I'm not a big fan of "2-finger stoppie" brakes.  Because even though I practice, practice, practice braking skills, I can't practice my response to surprise.  I don't want grab a full handful of 2-finger brakes and through myself on my face. 

Yamaha also moved away from the 14mm master cylinders.  The new bikes (FZ, FJR, MT) all appear to have 15mm masters

[Pat Conlon]

...Yamaha also moved away from the 14mm master cylinders.  The new bikes (FZ, FJR, MT) all appear to have 15mm masters

The new bikes also have ABS.....For non ABS I still think 14mm is best.

Thanks for the clarification amigo...I remember we had a long discussion on this topic a decade or so ago...

[JMR]

IMHO the best value and sweet spot for 2 finger braking on our FJ's is the 14mm axial m/c, Spiegler lines and R-1 mono block calipers with HH pads. It's really quite nice.

That's exactly what I ran and it is an excellent set up. Trying to introduce air into the system is not the way to go. I am sure an engineer from Brembo would agree.