Rear Brake Assembly

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Rear Brake

 Even though I like the old stuff I wouldn’t run a drum brake on the rear, mechanical or hydraulic, unless I was doing some kind of restoration project. What I usually use is the pedal assembly and master cylinder from a 73 to 79 FL and a Performance Machine rear caliper.

The master cylinder for the rear brake is mounted on the brake bracket located on the right-hand mounting lug welded to the front motor mount bar.  On custom applications that we’ll cover later it is typically mounted on the frame near the transmission.

Over the years the factory has used two types of master cylinders. The first is a unit made by ‘Wagner’ and the second later units were made by ‘Kelsey-Hayes’.

In the photo above the Wagner is on the left and the Kelsey type units are on the right. There are several variations on the Kelsey type because they’re easy to manufacture and the ‘billet’ outfits went wild for a few years.

The old original Wagner’s were made for use with hydraulic drum brake bikes and had a 3/4” bore. When the rear disc brakes came out in 73 the factory switched over to the small 5/8” bore Kelsey units on some models but the Wagner was used on some bikes up until 1979.

Most folks agree that the old Wagner looks like it belongs on a motorcycle while the Kelsey looks like it might have come off a fancy kitchen appliance.

Thankfully the Wagner can be found in both 5/8 and 3/4-inch bores nowadays to match the caliper requirements for a particular bike.

Unfortunately, all of these master cylinders are now made overseas and every now and then you’ll run into quality issues so having to do a major rebuild on a brand-new cylinder is not uncommon.

Calibrating your braking system which includes master cylinder, caliper, pedal to pivot arm ratio and line sizes is a science into itself and we’ll get to that later but for now just remember that the caliper you select will have a recommended master cylinder bore size.

For the moment we’re just going to describe the front pedal assembly and how it’s mounted, again using factory facsimile parts to keep costs down. The pieces below were purchased on eBay and even though they weren't in the original packaging they are obviously relatively new unused imported parts.

The pedal on the left is a later model, around 73 to 79 that came with the set but the correct pedal for this assembly is the one at the bottom of the photo taken from my parts stash. It's hard to see against the chrome sheen but the old model pedal has two bends in it as it leaves the pivot socket and moves towards the foot pad. The new model pedal only has one bend. These two pedals are not interchangeable and that may be why the set was sold to begin with.

Installation is simple. You can see two bolt holes that are about two inches apart that run at an angle roughly in the middle of the backing plate. These correspond with the two mounting holes on the tab welded onto the front motor mount bar.

Position the plate and use a 3/8-16 by 1" fastener in the lower left-hand hole to hold it roughly in place as shown below. The upper mounting hole is occupied by a 3/8-16 by 2" fastener that goes completely through the master cylinder, so we'll install that next but before we do take note of the snapshot below.

In this view I've inserted a piece of all-thread rod through the two forward most holes in both the shifter backing plate and the brake assembly backing plate. These two holes align with each other from left to right and are the forward mounting points for the stock floorboards if you're using boards.

Back in the day we'd ditch the boards and install our foot pegs made from bayonet handles or whatever was the rage at the time in these mount positions. That's still a popular option nowadays.

Assuming that we are going to be using floorboards the front mounting hole on the master cylinder will be occupied by a floorboard mounting lug as seen below highlighted by the small white arrow.

The easiest way to install the pedal assembly and master cylinder is to loosen the bolts holding the cylinder so it can be moved in and out by about three quarters of an inch. Fit the plunger assembly into the end of the cylinder and then slide the clevis onto the pedal before it is slipped over the pivot shaft. Holding both the pedal and cylinder push both parts back into their 'seated' position at the same time. It sounds more complicated than it is and I'm sure you'll intuitively do it. Go ahead and cinch up the pedal on the shaft with its washer and nut and insert the clevis pin, washer and cotter pin. Don't tighten down the cylinder mounting bolts just yet.

Without spacers behind the master cylinder, it won't line up correctly with the pedal or plunger and in my 'kit' spacers seem to have been retained by the previous owner.

You can see the gap between the mounting plate and cylinder in this photo. It looks like we need a couple of 1/4" spacers, but this will kind of be trial and error since we can't get a good measurement until the rear bolt can be tightened down on a spacer of any kind and get the backing plate fully seated against the frame mounting tab. Camera distortion in this close-up makes things look worse than they are.

I found a quarter inch spacer in a box full of miscellaneous nuts and bolts and it worked just fine but unfortunately there was only one, so I'll have to order another one from McMaster-Carr.

The plunger clevis is easily adjusted. I like to have about an eighth of an inch of free travel before the plunger starts to push the piston. Some people prefer a little more.

This unit didn't require that any fastener holes needed to be cleaned up for the bolts to fit so it was a smooth operation until I started pumping the pedal by hand during the adjustment work and the loop on the pedal return spring broke.

You can't see it very well in this photo, but the loop didn't just bend it actually fractured and is just being held on by the chrome plating on the backside of the break. I'll get a better spring at the hardware store, hopefully one that isn't made overseas.

One problem with the stock brake pedal is its ergonomics as it basically has none. The pedal position, being almost upright is in the worse possible position for easy and 'natural' operation.

Even on new models the pedal is still awkwardly positioned and one of the first modifications most riders make is to install a new 'extended' aftermarket pedal. These units move the pedal pad forward and downward making the pedal much easier to use as seen in this snapshot from Softbrake.

Unfortunately, these pedals are not made for the older bikes so most folks just modify a stock pedal, and this might be one the first things you put on your 'to-do' list.

That's about it for stock foot controls but we'll expand this section as the build progresses and we add the calipers and hydraulic lines.