Blue dot calipers

[1tinindian]

Radial master cylinder, not calipers.

I enjoy the look of the so-called 'urine cup'. But yes, that's your prerogative.

Why have a radial master cylinder and NOT radial calipers??
My research can not verify your claim.

Leon

[Pat Conlon]

Leon, a radial m/c vs a axial m/c is a separate issue from a radial mounted caliper vs a axial mounted caliper.
The two are not related.
IOW you don't need to match radial with radial and axial with axial.

Radial m/c's work just fine with axial mounted calipers and vice versa.

[1tinindian]

Leon, a radial m/c vs a axial m/c is a separate issue from a radial mounted caliper vs a axial mounted caliper.
The two are not related.
IOW you don't need to match radial with radial and axial with axial.

Radial m/c's work just fine with axial mounted calipers and vice versa.

Understood Pat, but is that how Yamaha built the R6??
That is what is in question.

What makes a master cylinder "radial", if it came on a bike from the factory with NON- radial (axial) calipers?


Leon

[rktmanfj]

Just to clarify some for the OP who, no doubt wants accurate info to do this upgrade:

• Some here are using the OEM FJ m/c with the blue (or gold or silver) dot calipers, and it reportedly works fine.
• Using a 14mm axial m/c (urine cup or not) is an upgrade in power and feel compared to the OEM FJ m/c.
• Jon Cain has reported in the past that a 19mm radial m/c is an upgrade compared to the two options above.
• Certain combinations of m/c and blue dots can be installed with the old brake lines reoriented.  The blue dots with the outside line are different, IIRC.
• You can use radial m/c with conventional blue dots.  The calipers cannot see and do not care what is pushing the fluid to them.
• Despite assertions to the contrary, the '02 R6 m/c is not radial, either in my recollection, or in Yamaha's parts list: https://www.yamahapartsandaccessories.com/parts-catalog/parts/street-mcy#/Yamaha/YZFR6_-_YZFR6P_-_2002/FRONT_MASTER_CYLINDER                            It may be a 14mm axial, but if the one Fintip has is a radial, it's not OEM to the '02 R6, or likely not 14mm.  IIRC, it's exactly the same part as the three R1 m/cs that I have here in the garage.

I was going to leave this alone, but it seems that there was enough going on here to muddy the water for anyone who might be contemplating this swap.

[Derek Young]

I put black ss brake lines on my 86.  Two separate lines from the master cylinder to the calipers. Here is the link to the post about the lengths.

http://www.fjowners.com/index.php?topic=6771.msg60752#msg60752

Derek

[jscgdunn]

 

[fintip]

Well, I guess that means the guy I got mine from had upgraded his?

Went and checked some more... You're right, I should have realized from the aftermarket coloring of the lever that it might be changed. It is hard to tell looking at pictures, as these radial MC's don't have a lot to look at, but the banjos on mine bolt on with a screw going vertically through them, instead of horizontally, as it does on the stock R6, as far as I can tell.

So after some tricky sleuthing, I found out that some R6 owners have been known to update theirs by converting to an '07/'08 Honda 600RR Master Cylinder, which seems to be what mine has, based on visual confirmation:



Mine:




Bonus, mine comes with this fancy-as-shit adjustable/folding (to prevent break in case of crash) lever:

https://www.denniskirk.com/folding-roll-a-click-brake-lever.p574092.prd/574092.sku

And the size? 17.5mm, it seems. (here).

Which strikes me as odd. If a 19mm radial M/C works with the stock calipers, 17.5mm isn't that big of a difference... That should work too, right? I was presuming, since I thought it was 14mm, that it was just too small of a piston to drive enough fluid to get mine to work (wheel won't lock up until 1.5 strokes of lever, almost no braking power until at 60% through with first stroke), but maybe it does need a rebuild kit and it would work?

Moot point now, since I'm going to be getting a '90 and putting blue spots with it. Guess if it gives the same symptom with the blue spots, I'll know for sure. Pretty sweet bonus, though. The lever alone is worth $130 new, and the M/C is worth some money as well. Not the most aesthetically pleasing unit in terms of having some scratches and such, but should be excellent from a performance perspective.

[FJ_Hooligan]

Okay, I'll type this real slow.

The radial master cylinder has a short distance between the lever pivot point and the piston.  An axial m/c has a greater distance between the pivot and piston.

The radial produces more force on the m/c piston for a given force pulling the lever.  This generates more pressure.  So the radial is more efficient at producing brake fluid pressure for a given input (compared to an axial unit).

Having the lever pivot so close to the piston also means that the piston doesn't have as much stroke as an axial unit.  Less stroke means less fluid movement; therefore, it needs a larger piston to compensate.  This is the problem you are having.  The 17.5mm piston does not have enough stroke to deliver enough fluid to create pressure with one full pull.  After your second pull, you move enough fluid to get pressure and then get to see the benefit of the higher efficiency of the radial design.

Unfortunately, this will never be an acceptable solution for the calipers you want to use.  

You need a 19mm radial or a 14mm axial

[Pat Conlon]

Well explained Hooligan..... Even I understood that...

[fintip]

Okay, I'll type this real slow.

The radial master cylinder has a short distance between the lever pivot point and the piston.  An axial m/c has a greater distance between the pivot and piston.

The radial produces more force on the m/c piston for a given force pulling the lever.  This generates more pressure.  So the radial is more efficient at producing brake fluid pressure for a given input (compared to an axial unit).

Having the lever pivot so close to the piston also means that the piston doesn't have as much stroke as an axial unit.  Less stroke means less fluid movement; therefore, it needs a larger piston to compensate.  This is the problem you are having.  The 17.5mm piston does not have enough stroke to deliver enough fluid to create pressure with one full pull.  After your second pull, you move enough fluid to get pressure and then get to see the benefit of the higher efficiency of the radial design.

Unfortunately, this will never be an acceptable solution for the calipers you want to use.  

You need a 19mm radial or a 14mm axial

There's no reason to be demeaning; I understand all of that. My point was that if a 19mm radial M/C works, it doesn't sound likely that a 17.5 would just *not* work. These aren't 'the calipers I want to use', just the calipers I tried to use. Likewise, one does not 'need' a 14mm axial unit, and a range of piston sizes are possible. 15.875mm (5/8") Seems to be the stock MC piston size. The difference between 15.875 and 14 isn't so different from 19 to 17.5.

So yes, it's possible. But until you actually show me some math, it seems possible that the seal of the rubber inside is weak, as well.

No slow typing needing...

[Tex]

Received the Blue Dots today. They look in great shape. Cleaner them up a bit. The pistons compressed with two fingers. Now I have to wait for my Galfer SS lines. They wont be here until the end of next week.  New pads will be here as well. EBC HH. Let the waiting begin.

[the fan]

There's no reason to be demeaning; I understand all of that. My point was that if a 19mm radial M/C works, it doesn't sound likely that a 17.5 would just *not* work. These aren't 'the calipers I want to use', just the calipers I tried to use. Likewise, one does not 'need' a 14mm axial unit, and a range of piston sizes are possible. 15.875mm (5/8") Seems to be the stock MC piston size. The difference between 15.875 and 14 isn't so different from 19 to 17.5.

So yes, it's possible. But until you actually show me some math, it seems possible that the seal of the rubber inside is weak, as well.

No slow typing needing...

No reason the master you have shouldn't work. The stock 05+ R6 and 04+ R1 masters are 16mm units (not sure on lever measurement). If you cannot get pressure with the set up you have either the caliper pistons are stuck, they are poorly bled, or the master needs to be rebuilt.

Bleeding the system is pretty easy with a auto part store "1 man bleeder kit" and the master you show has a bleeder it the top for bleeding the master. It wouldn't be too difficult to disassemble and clean the master as old brake fluid can leave deposits in the system if it has been sitting for a while.

[fintip]

The system is definitely fully bled, I used two different suction devices, so I find it likely that it isn't in optimal working conditioning. A rebuild will be in order.

[FJ_Hooligan]

There's no reason to be demeaning; I understand all of that. My point was that if a 19mm radial M/C works, it doesn't sound likely that a 17.5 would just *not* work. These aren't 'the calipers I want to use', just the calipers I tried to use. Likewise, one does not 'need' a 14mm axial unit, and a range of piston sizes are possible. 15.875mm (5/8") Seems to be the stock MC piston size. The difference between 15.875 and 14 isn't so different from 19 to 17.5.

So yes, it's possible. But until you actually show me some math, it seems possible that the seal of the rubber inside is weak, as well.

No slow typing needing...

Well then maybe you need to read more closely and comprehend.  I clearly explained why that master cylinder will not work with those calipers.  Actually both masters will "work" but the radial takes more than one stroke before it develops pressure.  I would consider that as technically not working for a braking system.

It's not just the diameter of the pistons, it's the STROKE also.  The piston size is only part of the fluid movement equation, the other is the stroke.    

If the m/c had "weak rubber" it would either be leaking externally and you would see it.  Or, if it's leaking internally, it would not generate pressure.

I can't do the math, there are too many unknowns, the biggest being how much fluid does the m/c need to move into the calipers to engage the pads.  

I will do some ratios:
The 17.5mm piston has 85% of the area of the 19mm piston.
The 14mm piston has 78% of the area of the 5/8" piston.
For these pistons to move the same amount of fluid, the stroke of the radial m/c is only 64% of the axial m/c stroke.
Or think about it this way.  For a given movement of the lever, the radial m/c delivers less than 64% of the fluid that an axial m/c would deliver.

I'm giving you sound logic and you reply with what you "think" is happening.
But you go right ahead and rebuild that master cylinder and report back.  

[fintip]

 

I'm not going to keep talking with you because

A) you don't realize that if a 16mm radial works, a 17.5 radial will work

B) you're kind of being an asshole. I don't need the advice of someone who talks like that to me. Chill. And I'm not asking you, so don't feel the need to respond.

Weak rubber won't build *full* pressure, but will expand and develop partial pressure. But the pressure will slowly fade, because it isn't a perfect seal. But it is partial seal. It isn't leaking, it's internal.