First-Gen 39mm Dual-Disc Upgrade

Two’s Always Better Than One…

They say approximately 70 percent of a motorcycle’s stopping power comes from the front brake system. Well, maybe “they” must not have tested many early single-disc FXRs and Dynas. That, or riders like myself, who for whatever hapless reasons, came to rely solely on rear brakes (because that’s all most of my first bikes had), and the older H-D front discs seemed better suited for inclined traffic stops anyway, not hard panic braking, let alone constant use. (Even to this day, I still tend to skid-maneuver my rear wheel through the occasional tight spot, but as you’ll read, I’ve acquired a new respect for performance front brakes.)

It wasn’t until a few years back when the rear master on my Road King failed during a long ride home from Northern California. It was a Sunday, there was tons of traffic, and I just wanted to get home—so I purposely kept my right foot on the passenger peg (away from the brake pedal) and used the front brakes the rest of the way. Fortunately, Jeff Holt had just set me up with a new set of floating rotors and sintered pads, so the impromptu brake technique lesson went better than it could have. It also gave me a whole new relationship with—and subsequent reliability on—using the front brakes the majority of the time.

That all pretty much changed when my ’90 FXR entered my life not too long ago. Its front brake was nothing like the Road King’s duals. Matter of fact, whenever I could squeeze enough lever to get it to work, it locked up. My old rear braking “skills” re-emerged for a spell—until I crossed paths with Still Kicking Moto’s (a.k.a. S-K) Juan Munoz.

While many dual-disc aftermarket setups are designed for the ’99–later 39mm lowers, S-K offers a machined billet bracket for the earlier style/offset mounting, which accept the readily available two-piston Tokico calipers that came OE on a variety of Suzuki and Kawasaki 650s (plentiful and cheap on eBay). Being a “floating” caliper, they perform much more efficiently than its fixed predecessor, not to mention don’t have the same inherent squealing characteristics.

So here’s how the basic dual-disc upgrade pans out parts wise: dual-disc 39mm (or just a right side leg), adapter brackets, calipers (that use 10mm x 1.25 banjo bolts, which work with stock H-D brake lines), 11.5-inch rotors, and an 11/16 bore master cylinder. I further added to the parts pile with a pair of Galfer USA Wave floating rotors (with a matched fixed Wave rear), had an all-new brake line set built by Mesa Hose, and threw on a Biltwell bar and riser combo. You can take it even further by adding new controls (S-K offers Brembo and ASV options), but to simply bring your FXR/Dyna up to that 70-percent range as it should be, the basics are all it takes.

First-Gen 39mm Dual-Disc Upgrade

S-K Moto’s caliper bracket adapters accept the popular Tokico dual-piston floaters and 11.5-inch rotors. To complement the calipers, I upped the ante with Galfer USA’s Wave floating rotors (DFP12083), which are made from non-recycled high-carbon 420 stainless. (Note, these are designed for ’00–later H-D hubs and, thus as you will see, require a machine spacer that S-K provides.)

Words and Photos: Rob Fortier

First-Gen 39mm Dual-Disc Upgrade

The rotor bolt patterns are the same, however the later-model centers are slightly larger (2.212-inch versus 1.985-inch). Juan first machined a chamfer on the inner edge of the center ring “spokes” to seat the rotor over his stepped spacer.

Words and Photos: Rob Fortier

First-Gen 39mm Dual-Disc Upgrade

The rotor bolt patterns are the same, however the later-model centers are slightly larger (2.212-inch versus 1.985-inch). Juan first machined a chamfer on the inner edge of the center ring “spokes” to seat the rotor over his stepped spacer.

Words and Photos: Rob Fortier

First-Gen 39mm Dual-Disc Upgrade

Minus the calipers, which can be found on eBay ranging from $20 for used take-offs up to around $100 or so for a rebuilt pair, this is the basic adapter setup from S-K.

Words and Photos: Rob Fortier

First-Gen 39mm Dual-Disc Upgrade

The aluminum brackets are machined for R/L fitment and tapped to mount on pre-2000 Showa 39mm legs.

Words and Photos: Rob Fortier

First-Gen 39mm Dual-Disc Upgrade

Grade 8 buttonhead Allens are supplied to attach the brackets to the fork legs.

Words and Photos: Rob Fortier

First-Gen 39mm Dual-Disc Upgrade

Same-grade cap screws will mount the calipers, as such, which will install once the wheel is in place with the rotors on.

Words and Photos: Rob Fortier

First-Gen 39mm Dual-Disc Upgrade

I’d originally sourced a pair of six-piston Tokico radial calipers (GSXR 1100 type) to use, but they would require that the wheel spokes be machined quite a bit for clearance (the smaller two-piston calipers are more than sufficient). Nevertheless, the brakes also came with the lines and this Nissin junction block, which fit perfectly below the lower tree.

Words and Photos: Rob Fortier

First-Gen 39mm Dual-Disc Upgrade

With the Galfer rotors installed (which require the non-countersunk style hardware), Juan chucked the wheel up in the front end...

Words and Photos: Rob Fortier

First-Gen 39mm Dual-Disc Upgrade

...and threw the calipers on in preparation of having Mesa Hose build a custom brake-line set.

Words and Photos: Rob Fortier

First-Gen 39mm Dual-Disc Upgrade

Since Mesa would be building the lines on the actual front end, in order to get the master cylinder-to-junction line the right length, we had to have the bars and risers installed. I opted for Biltwell’s 8-inch Murdocks with black Trackers (along with the aluminum throttle and Recoil grips).

Words and Photos: Rob Fortier

First-Gen 39mm Dual-Disc Upgrade

The controls shown mocked up are the modified ASVs that S-K offers.

Words and Photos: Rob Fortier

First-Gen 39mm Dual-Disc Upgrade

The Nissin distribution block came with metric banjo bolts; the calipers, as mentioned, use 10 x 1.25mm banjo bolts.

Words and Photos: Rob Fortier

First-Gen 39mm Dual-Disc Upgrade

Both work with standard H-D brake banjo fittings. Mesa also supplied new copper compression washers for the calipers, block, and master cylinder.

Words and Photos: Rob Fortier

First-Gen 39mm Dual-Disc Upgrade

Keep in mind, the Tokico calipers used DOT4 brake fluid—if you’re running them without rebuilding, they’ll need to continue using DOT4 (which will require the master cylinder to be flushed clean of all DOT5). It makes more sense to start with freshly rebuilt calipers and stick solely with DOT5 throughout. The new EBC pads were obtained from Malcom Smith but definitely can be found cheaper online.

Words and Photos: Rob Fortier

First-Gen 39mm Dual-Disc Upgrade

The stock single-disc master cylinder (5/8-bore) was swapped out—ironically enough—the 11/16 master off the very same Road King that learned me the importance of front brakes in the first place. Prior to bleeding the entire front brake system, the master was bled individually.

Words and Photos: Rob Fortier

First-Gen 39mm Dual-Disc Upgrade

If rotor spacers are being used, you’ll need to make sure the left side is notched accordingly for the speedo drive.

Words and Photos: Rob Fortier

First-Gen 39mm Dual-Disc Upgrade

Once the front end was reinstalled on the bike and Loctite was used on every bolt, the front brakes were fully bled. I noticed that even the slightest of air bubbles will cause the lever to be spongy, which is why it’s important to make sure the master is bled properly as well.

Words and Photos: Rob Fortier

First-Gen 39mm Dual-Disc Upgrade

The rear wheel was also treated to a Galfer rotor, this time a solid-mount 11.5-inch Wave (DF682W) with Galfer’s semi-metallic carbon OE replacement pads. After bleeding the rear and bedding (breaking in) the new pads and rotors, my old relationship with prominent front braking was finally rekindled. While all the parts combined completely changed the braking characteristics of the bike, the front setup alone was the biggest performance difference—hands down.

Words and Photos: Rob Fortier

Sources

S-K Moto

Galfer USA

Biltwell, Inc.

Mesa Hose (949) 645-2661