Master Cylinder Project

[JW113]

Let's face it: the stock front brake set up on a Shovelhead leaves a lot to be desired. It's amazing that even though they use a massive caliper, it takes an equally massive amount of squeeze force on the front brake lever to get it to work. And it has the classic "wooden" feel, going for slightly grabbing to locking the wheel in very little range of force. A lot of people, maybe almost all, think the problem is the caliper. I, however, place the blame on the master cylinder. Hydraulic brakes work on the concept of hydraulic mechanical advantage, similar to the way a lever and fulcrum, or transmission gears, work. The higher ratio of caliper piston to master cylinder piston, the greater the mechanical advantage, and a corresponding less amount of lever force required to operate the caliper. This is a nice article that explains it:

http://www.vintagebrake.com/mastercylinder.htm

According to the author, for a single piston caliper, the piston to piston ratio should be between 12 and 14 to 1. The ration on a stock Shovelhead (2.25" (57mm) to 3/4" (19mm) ) is 9:1. Terrible.

So, just to check this out, I sent a spare front master cylinder to Apple Hydraulics out in Calverton NY, to sleeve it down to 5/8". That would give a caliper to master cylinder ration of 13:1, right in the sweet spot.

Before:
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After with 5/8" brass sleeve:
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I chose 5/8", since the Shovelhead 3/4" piston is reasonable close in geometery to the Evo era 5/8" piston. The length and O-ring slot are close enough to align with the feed/vent holes in the Shovelhead master cylinder.

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Continued on next post...

[JW113]

Part 2

The one area that did not align was the push rod hole in the piston. The 5/8" was about 0.25" deeper, so I had to make a longer Shovelhead style push rod out of 1/4" steel rod, and a small spacer for the spring perch. I chucked the cut rod in my drill press and made a nice rounded ball end with a file.

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Using a Evo 5/8" rebuild kit, I assembled it. Had to round up a 5/8" internal retaining ring at the hardware store.

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It all went together great, the lever has just a tad of free play, feels basically like stock. I went for a test ride, and sure enough, way less lever force now needed. It did feel a bit spongy, but then I haven't yet bled the system after putting this master cylinder on, was to eager to check it out. Will take care of that this morning.

There was one little hitch, though. I feel like a complete a-hole.
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As I was prying the wires of the brake light switch, I lost grip on the master cylinder and it fell on the front fender. Ouch!! So, one project leads to another, need to get that fixed now.

So was it all worth it? I could have easily just bought a different master cylinder and maybe caliper as well, but I wanted to keep it looking basically stock. So to that end, at least for me, yes it was worth it. Gotta go bleed the front brake and take for another spin, see if that clears up the spongy feel.

-JW

[Ohio HD]

Hopefully it works, nice work.


FYI
I bought these from HD earlier this year when they had a 25% off on accessories sale.

I used to lay old towels across the front fender and tank. They always ended up on the floor sooner or later. These are made to fit, so they stay on.



94640-08




94641-08

[JW113]

Just got back from a little shake down test ride. And the verdict is: Night And Day! It now is able to stop as good as any Harley-Davidson.
 

At least, a whole lot better than a stock Shovelhead with banana calipers. Am very happy with the results.
 

Indeed there Ohio, I need to get a set of those. I had a piece of plastic on the fender, thinking the only thing that might fall on it would be a few drops of brake fluid. Oh well, serves me right, a feeble & shaky old geez like me should be taking more caution.

-JW

[Lew]

Good stuff JW.  I've thought about doing this, but never got to it.  Next time I have to R&R the front brake on my scooter, I'm going to do this.  Thanks for the detailed write up! 

[Ohio HD]

Indeed there Ohio, I need to get a set of those. I had a piece of plastic on the fender, thinking the only thing that might fall on it would be a few drops of brake fluid. Oh well, serves me right, a feeble & shaky old geez like me should be taking more caution.

-JW

I can relate. I drop 99% of the things I pickup....     
I may start working on things from the floor.

Was drilling my oil lines in the S&S cases a week or so back. I laid the cordless drill down. It fell off the bench, I went to grab it as it was falling. I grabbed the 3/8" very sharp drill bit as it slid in my hand. Red stuff everywhere.....     

[76shuvlinoff]

Good work JW.
In my search for real brakes on my FLH I tried a GMA caliper and eventually a GMA master cyl which I think it 5/8 but can't swear to it now, the actual squeeze didn't improve much. Eventually I mounted dual disc forks, a Road King rim with dual rotors and dual 4 pot calipers connected to my GMA front master. This Rube Goldberg assembly gave me a two finger stopper. For me sometimes being lucky is better than being good. 

The rear is also a GMA assembly but the with the 3/4" stock MC it was, as you say, wooden. I acquired a 5/8" GMA MC for that, while not perfect it's much better.


 When the wife gets in the mood for new bath towels the old ones head to my barn locker. Great fender/tank covers.

[JW113]

Hey Mark, yeah I'm sure this set up is certainly not as good as you've done. Heck, I'm still running on 10" rotors! All I can say is that it "works", and better than stock. That's not saying a lot, yes I know. But there is a certain devious side of me that when somebody comes up, checks out the bike, and exclaims 'hey, that thing is, like, stock!', I chuckle silently to myself...

I "fixed" the paint chip in my fender this weekend. Yeah, leaves a lot to be desired, but at least not a big white hole glaring out saying "look at me!".

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-JW

[Hossamania]

For a quick paint fix, that works!

[david lee]

Hey Mark, yeah I'm sure this set up is certainly not as good as you've done. Heck, I'm still running on 10" rotors! All I can say is that it "works", and better than stock. That's not saying a lot, yes I know. But there is a certain devious side of me that when somebody comes up, checks out the bike, and exclaims 'hey, that thing is, like, stock!', I chuckle silently to myself...

I "fixed" the paint chip in my fender this weekend. Yeah, leaves a lot to be desired, but at least not a big white hole glaring out saying "look at me!".

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-JW

touch up paint ?

[JW113]

I found a Honda pearl blue color that matches my paint almost exactly, so bought a touch up bottle. Filled the two holes with paint, were very deep, took like 15 coats, then wet sanded and polished.

-JW

[david lee]

I found a Honda pearl blue color that matches my paint almost exactly, so bought a touch up bottle. Filled the two holes with paint, were very deep, took like 15 coats, then wet sanded and polished.

-JW

your lucky being pearl paint

[flhs90]

Thank u for excellent write-up.

[Fugawee]

Nice Job on the Touchin' Up...looks good from where I'm sitting.

[JW113]

your lucky being pearl paint

Well, not quite. Pearls, candies, metalics, they're all pretty tough to match and blend as they are all base coat with clear top coat. It can be done, but lots of work. If it were a solid color like my turquoise Softail, or HD vivid black, easy-peasy and you would not have been able to tell at all. With the right prep, you can blend them perfectly.

-JW

[david lee]

your lucky being pearl paint

Well, not quite. Pearls, candies, metalics, they're all pretty tough to match and blend as they are all base coat with clear top coat. It can be done, but lots of work. If it were a solid color like my turquoise Softail, or HD vivid black, easy-peasy and you would not have been able to tell at all. With the right prep, you can blend them perfectly.

-JW

thats what i meant you were lucky, you found a similar colour. pearls candys are so hard to match

[JW113]

Ah, yes, that is true. I saw this Honda Civic in a parking lot, and noticed it looked very similar color to my Shovelhead. I then went to the Honda dealership, and parked my bike next to one of them, it was almost indistinguishable, so I ordered a touch up kit. Glad I did, it's pretty stinkin' close.

-JW