Based on my satisfaction with the 1/2 inch master cylinder swap on the clutch side, I bought a used 1/2" bore brake master cylinder to try on the other side. In addition to a reduction in operatiing force, I was looking to gain better modulation and control vs. the "wooden" feel of the stock system. Since the ST11 is so effortless to drive (steering, throttle, etc) once its pushed back from the gate and the clutch is out, it seemed a shame for both levers to require lumberjack forearms (which I lack). Further, the strength of my arthritic hands is going in the wrong direction. So here we go on phase II of modifying the controls to be easier to operate.
The donor on the clutch side was a 2007 VFR800 non-ABS, though the date range of the control I used is alleged to be 2002-2008 VFR800 and VFR800A. The donor on the brake side was a 1998 CBR600F3. The date range of the brake control I used is alleged to be 1993-1994 CBR600F2 and 1995-1998 CBR600F3. The key in both cases if you are looking at salvage parts is to ask for a picture showing 1/2 embossed on the cylinder body.
This is the embossing on the stock ST1100 brake master which shows it to be a 14mm...
This is the donor brake master cylinder...
And this is where it used to live - also a twin disk, twin pot brake system...
Here it is on the ST. Like the clutch master, I also put a rebuild kit and a banjo bleeder bolt in it. eBay salvage parts are a lot like Forrst Gump's box of chocolates - you never know what you are going to get. This one, despite being clean on the exterior was dirty though functional inside. It also had an unknown piece of plastic inside the reservoir and the cover over the compensation port was installed upside-down. Now it is baselined and I know what I have and that it is good.
Finished up installation...
Bled by vacuum through the banjo bleeder, it is good to go...
FIELD TEST: Again I am very satisfied with the result. Lever pressure is much reduced and the brake response is much more progressive and easier to modulate.The downside, as with the clutch, is that the travel required is increased meaning that the lever travels closer to the bar than before. If you are a four-finger braker, it is no matter. However, if you are a two-finger braker, there may be times when the two remaining fingers become bound as braking approaches "panic" level. I am happy with the compromise, but some people may not be. It is easy to retrain to use four-fingers all the time, and to me, the benefits are well worth it. To make the bike stop, you have to do work on the brake fluid. Work is force x distance. If you want to make the force go down, you are going to make the distance go up - just like changing gears on a bicycle. My change went from 14mm to 1/2 inch, which is 12.7mm. A millimeter makes a substantial difference. If you could find a 13mm master, it would have a bit less travel but require a bit more force. Better? I don't know. I have a 12mm Brembo cylinder that I intend to try on it, but I suspect that may be a bridge too far. Brembo does make a 13mm cylinder, but I haven't located a Honda 13mm cylinder. I don't know why they went with inch-sized equipment here, but they did.
UPDATE: I originally reported that the lever travel was just a bit excessive and that there can be finger entrapment in a panic stop if you use two-finger braking technique. I associated this with the 12.7mm cylindere being a bit too small. Recently I changed the almost worn out brake pads and again re-bled the system and this issue is now resolved. There is now no issue of finger entrapment in two-finger braking with teh 12.7mm master cylinder.
If you are looking at the Brembo cylinders, they mark things differently and it could get confusing. This is stamped on the body of my Brembo brake master...
But unlike the Honda marking above, this does not mean 14mm. It is the casting date - 2014. They use the same casting for all of them and bore or sleeve them to the desired bore size. The bore size is given in a laser-etched part number like this one on my 12mm cylinder...
Also, if you are planning on using a Brembo OEM style cylinder like the PS series, you will find that the clamp doesn't hold it high enough off the handlebar to clear the Honda switches. So, you have to either move it inboard to clear the switches (which creates an effectively shorter lever) or you need to find a way to move it away from the bar. Copying the handlebar "flip clip" trick of raising the handlebars by putting an upper clamp half under the bar used with longer bolts, I did an equivalent mod by purchasing another clamp and placing it underneath like this..
The top (black) clamp is a mirror style clamp that came with the cylinder. I bought a non-mirror (silver) clamp for the stand-off. The clamps have an up and a down arrow on them because the two legs are different heights. To make the height differences balance out, the silver clamp is installed with the "up" arrow pointing down. When you are finished, you have the same stand-off height as the stock Honda unit...
Folks who are happy with the stock set-up can save themselves the trouble. But if you have a similar physical limitation to mine, here it all is. Even without the arthritis issues that started me on the clutch mod, I think the finer brake modulation with this mod is a significant improvement.
The donor on the clutch side was a 2007 VFR800 non-ABS, though the date range of the control I used is alleged to be 2002-2008 VFR800 and VFR800A. The donor on the brake side was a 1998 CBR600F3. The date range of the brake control I used is alleged to be 1993-1994 CBR600F2 and 1995-1998 CBR600F3. The key in both cases if you are looking at salvage parts is to ask for a picture showing 1/2 embossed on the cylinder body.
This is the embossing on the stock ST1100 brake master which shows it to be a 14mm...
This is the donor brake master cylinder...
And this is where it used to live - also a twin disk, twin pot brake system...
Here it is on the ST. Like the clutch master, I also put a rebuild kit and a banjo bleeder bolt in it. eBay salvage parts are a lot like Forrst Gump's box of chocolates - you never know what you are going to get. This one, despite being clean on the exterior was dirty though functional inside. It also had an unknown piece of plastic inside the reservoir and the cover over the compensation port was installed upside-down. Now it is baselined and I know what I have and that it is good.
Finished up installation...
Bled by vacuum through the banjo bleeder, it is good to go...
FIELD TEST: Again I am very satisfied with the result. Lever pressure is much reduced and the brake response is much more progressive and easier to modulate.
UPDATE: I originally reported that the lever travel was just a bit excessive and that there can be finger entrapment in a panic stop if you use two-finger braking technique. I associated this with the 12.7mm cylindere being a bit too small. Recently I changed the almost worn out brake pads and again re-bled the system and this issue is now resolved. There is now no issue of finger entrapment in two-finger braking with teh 12.7mm master cylinder.
If you are looking at the Brembo cylinders, they mark things differently and it could get confusing. This is stamped on the body of my Brembo brake master...
But unlike the Honda marking above, this does not mean 14mm. It is the casting date - 2014. They use the same casting for all of them and bore or sleeve them to the desired bore size. The bore size is given in a laser-etched part number like this one on my 12mm cylinder...
Also, if you are planning on using a Brembo OEM style cylinder like the PS series, you will find that the clamp doesn't hold it high enough off the handlebar to clear the Honda switches. So, you have to either move it inboard to clear the switches (which creates an effectively shorter lever) or you need to find a way to move it away from the bar. Copying the handlebar "flip clip" trick of raising the handlebars by putting an upper clamp half under the bar used with longer bolts, I did an equivalent mod by purchasing another clamp and placing it underneath like this..
The top (black) clamp is a mirror style clamp that came with the cylinder. I bought a non-mirror (silver) clamp for the stand-off. The clamps have an up and a down arrow on them because the two legs are different heights. To make the height differences balance out, the silver clamp is installed with the "up" arrow pointing down. When you are finished, you have the same stand-off height as the stock Honda unit...
Folks who are happy with the stock set-up can save themselves the trouble. But if you have a similar physical limitation to mine, here it all is. Even without the arthritis issues that started me on the clutch mod, I think the finer brake modulation with this mod is a significant improvement.
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