Vespa Fully-Hydraulic Disc Brake Upgrade

I posted last week that I have been suffering through the first few weeks of 2011 with the semi-hydraulic Grimeca disc on my ’85 Vespa PX failing to bring any bite to the front brake. Making the decision to upgrade the system to fully hydraulic, this weekend – with a ScootRS combination master cylinder / brake lever in hand – I set about the task. Read on for how it’s done.

The job is a full day’s work but with patience and the right tools at hand it’s relatively easy. Remember, I already have a disc brake on my front hub, so this was just a matter of hooking it up to a brake line and installing the new brake lever and hydraulic fluid master cylinder in place of the old cable lever.

First, let’s take a look at the ScootRS solution:

The image above shows three of the four combined components that make up the solution (the fourth is below the unit out of site.) Central to the design is a stock Nissin master cylinder (MC) that contain the brake fluid. This is solidly cast by a Japanese brake company with a solid reputation. The unit also includes a threaded recess for a 10mm wing mirror which you will need if you want a throttle-side mirror, given the installation will partially obscure your regular mounting point.

The second part of the set up is where ScootRS comes in with their proprietary cast bracket that bolts to the back of the Nissin MC with two hex bolts. This is designed to plug into your handle-bar and set the brake at the correct angle for use following some cutting to make it fit. Scooterists who are more enterprising than me could make one of these brackets themselves, but it sure is nice to have it ready to go.

The third part of the set up is a cast brake lever that also includes a cast lip that in addition to pumping the master cylinder operates the fourth part of the set up, a small electrical brake switch bolted to the bottom of the MC. The lever is one of my only small niggles with the set up. I found it a little loose for my taste in up and down play on the bolt. Nothing a thin spacer washer won’t resolve.

Here’s a look at the back of the unit, and in particular the ScootRS bracket. The hole on the far-right is designed to accept your existing brake lever pivot bolt. The hole on the left of the bracket is threaded and requires a new hole to be drilled from the underside of your handlebars to help lock the bracket in place. It’s actually a pretty elegant solution because once it’s done it’s not visible from the top of the scooter. In addition, the bracket is angled to cosmetically fit the existing form of the lower headset on your bike.

Again, only one small niggle here, and that is that the unit didn’t come with a bolt and lock washer for the new hole that needs to be drilled. A trip to the hardware store fixed that, but it would have been nice to have it out of the box. Niggles aside, it’s a nice set up, that you’ll see below it works very well on the bike once everything is in place.

On to installation. ScootRS claims on their website that the bracket requires a small cut to the existing headset on your bike. In reality, that’s a little generous. It requires a size-able cut followed by plenty of filing and finishing and a hole for the new bolt. A Dremel is handy to help remove material if you have one but not critical.

At the very least you’ll need a junior hacksaw, a 1/8″ or so drill-bit and a flat file. Fortunately the metal you’ll be working with is relatively soft and once the set up is complete it looks tidy. It took me about three hours to get the cut I wanted, with a snug fit and a clean finish.

When you order from ScootRS they include a link to a web page that gives decent installation instructions including a clear photograph of what will need to be cut. In retrospect, I recommend that like a plastic surgeon, you reference the photograph they provide and use a felt pen to mark on the bike the area you will be cutting away before making an incision.

Here’s the area you’ll be dealing with and the old brake lever removed. I’ve also removed the top of the headset to get more access but all cuts will be made to the visible bottom of the headset only. That existing brake lever pivot hole will be used as one of the securing bolts for the new bracket so hang on to the bolt and nut you removed from the old lever, you’ll be using it again later:

In the photograph below I’ve made the first cuts. The point of no return so to speak. The metal cuts easily along the existing cast lines with a junior hacksaw. Also, thankfully the angles of the cuts you need are easy to get at without contortion. At this point, take it from me, cover the front-end of your scooter with a shop cloth, or plastic. The metal shavings get everywhere. Here, I’m working on the NYC sidewalk – Vietnam style:

In the photograph below you can see the entire area that needs to be removed. It’s partially filed but not yet cleaned up. Some wet and dry paper will help with the final clean-up.

The yellow line marks where I made a mistake, and should have cut for a tidier finish. It’s something I could have avoided if I had marked on the bike with a pen where to cut which is why I mentioned this above. Instead I kept glancing back and forth at the photograph supplied by the ScootRS tech help.

The brake will install fine either way but cutting along the line would have meant a cleaner looking set up from the top. Mistake or no, the job is a matter of repeatedly offering up the bracket to check your cut and fit. In addition to what you can see in the photograph, there’s a decent amount of material inside the recess that needs to be removed where the original cable outer recess sat inside the headset. I used a Dremel to do this but a file works just as well but naturally requires more elbow grease.

You can also see a scratch where I slipped with the file. Obviously I could have done more to protect the paintwork but unless you are super careful, you’re going to need some touch-up paint anyway. Thankfully much of what you see here ends up out of view once the lever is installed.

Here’s another angle of the same area. It took me about three hours to get this cut the way I wanted it using mostly hand tools. Patience is the key here, again some slips with the tools on my part could have been mitigated by covering the paintwork around the work area. No matter, I knew that I have some touch-up paint available so I knew I didn’t have to be anal about nicks or scratches. I’ll buff these out later but for now I’m keen to get this brake installed:

In the photograph below I’m offering up the bracket to the recess so you can see how the bracket is the secret to the ScootRS solution. You can also see my mistake in the cut to the left of the hex-bolt hole on the top of the bracket. No big deal, but learn from my mistake and measure twice, cut once.

The hole on the bracket just peaking out of the left-hand side will naturally line up with the hole on the headset once the bracket is fully inserted and installed. You can also see how the bracket is angled to cosmetically match the front of your bike:

In the next photograph, I’ve fully  installed the bracket and master cylinder. In the top half of the image you can see how the cast bracket fits in the recess I started with the first two hacksaw cuts:

Below, the yellow circle shows the new bolt you need to drill for and install from the bottom of the headset. On the top-left of the photo you can see the nut from the original nut and bolt you save from the old lever set up.

You can also see where the hydraulic hose feeds through into the throttle handlebar along with a wire I installed connecting to the brake switch (more on this in a moment.) I found I needed to remove yet more material from the headset to get the clearance I needed to feed both the wire and hose through, but again, it’s out of sight in the final set-up. I eyeballed where to drill the hole for the bolt, but making a quick paper template is a good idea too.

With the brake and master cylinder in place, it’s time to talk about the hose that will connect the master cylinder to the brake caliper on the front hub.

I ordered a 125cm stainless steel braided hose from ScootRS along with the lever. It’s nice quality and comes with removable banjos at either end – these are the connectors that form an air-tight seal at both the master cylinder and brake caliper. They’re banjo shaped hence the name. Removable banjos aren’t required with your hose, but given you need to feed the hose into the headset and later through the top of your front fender, they allow you to cut smaller holes just big enough to accept the diameter of the hose.

My only complaint with the hose is that while ScootRS recommend it for their disc brake set up, I found it was a centimeter or two just shy of the ideal length for my existing Grimeca set up. This is because the connection point on the Grimeca brake caliper is at the bottom of the front hub. On ScootRS’ own disc brake set up, it’s on the top of the back. My bad, not there’s. In my final installation it’s a little tighter than I’d like but it does have enough flexibility to allow the front wheel to turn without anything catching and that’s key. You may want to measure your set up before ordering a hose, and add a couple of inches to your measurement because a little slack is not a bad thing.

In the image below you can see how the hydraulic hose feeds inside the headset and down the steering column. Note – it feeds down alongside the front fork, not inside it like the old brake cable, although I suppose it could be wrangled to fit. I added some grease to the hose partly to help feed it through, and partly to keep it lubricated as it rubs whenever the steering column is turned as part of daily driving.

The yellow circle above is where I snipped the old front brake light switch that used to be in-line with the old cable set up. With a short length of lamp cord that I bought from Home Depot I extended the wiring out through the handlebar to connect to the switch under the master cylinder. After this photo was taken I used insulation tape to tidy up the job and prevent shorts. Given I just eyeballed the lamp wire as an appropriate gauge, and no less than nothing about electricity it worked a treat.

Below you can see a nice shot of the brake in place. I removed the horn-cast to help feed the hose down along the fork. You can see where it comes out at the bottom of the horn-cast just above the front fender.

And below is where I drilled a hole at the back of the fender to allow the hose to run from the bottom of the horn-cast, through the fender and down to the wheel. You can see the benefit of a removable banjo here. This is is exactly how it feeds through on the Stellas and the later disc brake PXs.

I added a rubber grommet from the hardware store. Unfortunately I found that because the hose is tight, it keeps pulling the grommet out of place. I’m going to revisit this later with a short length of rubber or something. What I’m looking for here is less about cosmetics, and more that in daily driving you don’t want the twist of the front fender to slice through the hose. Bad news.

And here it is hooked up to the existing brake caliper. As you can see in my set up it’s a little tight, but it does have just enough slack so as to not inhibit any turning. I tested this by repeatedly turning the handlebars to make sure nothing was stretching. I angled the banjo at the bottom to help keep the hose away from the tire during daily riding. If you have extra slack you can add a small bracket to do likewise:

With the brake caliper in place, and the hose hooked up all the way from the master cylinder down to the brake caliper on the disc, we’re nearly done. I cleaned everything up; put the headset back together, and installed my old wing mirror in the recess on the Nissin cylinder.

What remains is something of an art: hydraulic brake bleeding. The master cylinder is a reservoir for hydraulic brake fluid (DOT3 or DOT4 compliant) that is compressed by the brake lever, and passes that compression down through the hose to the brake caliper plungers to push the brake pads on to the disc.

I won’t go into brake bleeding here because it’s been demonstrated elsewhere. Basically not only do you need to feed brake fluid into your new set up but you need to expel any air in the system in the process. Air is your enemy because it can be compressed more fully than fluid leading to spongy brakes or, at worst, brakes that do nothing.

Mostly expelling air is a matter of periodically opening the bleed nipple at the brake caliper but I actually found that repeatedly depressing the lever at the headset not only forced brake fluid into the hose and down to the caliper, but also forced air bubbles up and out of the closed system, through the master cylinder reservoir and pop-pop-pop into the New York atmosphere.

It took me about an hour of expelling air and feeding fluid into the system to get a “good brake.” It’s immediately noticeable when it happens, instead of a slack brake lever you begin to get resistance making it harder and harder to depress the lever. A few more pumps got it nice and solid as the last of the air bubbles blew out.

With the brake now operational, all that remained was to refit the top of the master cylinder and take it for a cautious test drive.

The brake works a treat. It’s like night and day compared to the semi-hydraulic set up, and far better than the original drum brake ever was.

That said, If you’ve got a decent drum brake on your bike I say leave it alone. The drum brakes on my Lambretta for example are very good even if they are old technology. But even with new shoes, I couldn’t get any stopping power so I needed to upgrade to a disc. What I can say after going semi-hydraulic and now fully-hydraulic is that yes – as many others have already advised – if you’re going to go to the trouble (and expense) of installing a disc brake don’t do things by half. Go for a fully hydraulic set up.

I’m very pleased with the ScootRS set up. It’s basically a jury-rigged Nissin brake wrangled to fit a Vespa P-series via their bracket. Once installed though it looks tidy and given the amount of Stellas and later Vespa PXs on the streets doesn’t look out of place on my bike. I’m also pleased with their hydraulic hose even if a couple more inches in length would have saved me some headaches. They also included with the order a 2011 calendar of Vietnamese girls draped over various scooters, something that’s hard to complain about.

Some scooterists recommend replacing your lower headset with one from either a Stella or a later PX when you convert to a hydraulic set up. This will give you the mounting holes needed to fit Piaggio’s Grimeca default master cylinder / lever set up if you prefer not to go down the ScootRS route. If you can find one for cheap, either new-old-stock, or an LML part I say go for it, but the ScootRS solution saved me some cash (and a good amount of time) by not needing to replace the lower headset. Plus removing the lower headset requires the removal of a good amount of bolts, cable, and wiring and is a job in itself.

I’m going to get some touch-up paint to finish the job in the next week or so, but for now off to ride, and more importantly to stop…

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