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Improved Braking Systems for the Custom Market

By the Wizard of Custom and Bandit with photos by Markus Cuff and the BDL team

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Belt Drives Ltd. is just about synonymous with belt drives themselves and it’s been that way ever since Steve Yetzke opened the doors and incorporated the name back in 1990. The company is now one of the largest suppliers of primary and final drive belts in the aftermarket.

But the BDL group of companies is growing well past the design and production of those iconic belt drives. All of this fits right in with Yetzke‘s business and life plan. “One of the first machine-shop businesses I had, way back at the beginning,” he says, “pictured boats, hot rods, Harleys and off-road racers on the brochures. All the toys with explosive performance fun across the board.”

“That was the ultimate goal way back when,” Yetzke said, “to be involved in them all.” He’s living that dream right now.

“It’s hectic, but it’s all fun. I’ve grown up around all
this,” he explained. His dad bought a machine shop when Yetzke was 11 years old and before long the eighth-grader was in the center working lathes and screw-turning machines, doing piece work on his own with his dad’s equipment.

“It was boring but educational threading pipe legs for industrial stoves,” he remembers, “making five bucks an hour, big money for a kid back then!”

Pacific Broach, that Yetzke family business, is still very much alive today, now producing impellers for marine water pumps. But by the early ’70s, Steve stepped out on his own, producing all the belt-drives components for Phase 3 of America and Primo, along with drives, pulleys and specialized parts for such notable racers as Elmer Trett, Russ Collins, Mickey Thompson and A.J. Foyt. All that led to what we know today as BDL, Belt Drives Ltd.

Four years ago, Steve moved the entire BDL operation, everything from the CAD design and rapid prototyping studios to the more than 50 CNC mills and lathes, gear cutting equipment and rubber manufacturing facility, into one, large state-of-the-art facility in Anaheim, CA. “We’re one of the few places on the West Coast offering all of that,” he said with justifiable pride. As always, the BDL goal remained clear, to provide customers with the best aftermarket accessories unparalleled in performance and design.

A classic GMA brake caliper on the Bikernet Mudflap Girl FXR by Spitfire, with a Chip Foose designed MetalSport wheel.
A classic GMA brake caliper on the Bikernet Mudflap Girl FXR by Spitfire, with a Chip Foose designed MetalSport wheel.

A few years back, Yetzke took on the entire GMA brake line up, two of the best-known names in the business, GMA and BDL. They still offer the familiar GMA ball-milled/clear anodized finish for those iconic calipers — now called the “GMA Classics.” They’ve added plenty all-new and upgraded components to the GMA line. Everything is available in plain-finish versions, polished, chromed, or black anodized.

The GMA hand controls were updated, too, and a full line of forward controls added. BDL now has yet another company under its umbrella, JAMAR, a top name in off-road racing brakes since the 1970s.

“It’s the perfect addition,” Steve said. “While producing JAMAR components, we folded some of the technology from Jamar into the GMA line.”

Incorporating some of JAMAR technology into the GMA Harley-Davidson brakes was no small deal. “In the serious off-road-truck world, we saw 900-degree brake rotor temperatures in the short-course racing. Punishing stuff,” he explained. “But, we discovered how to make brakes work under extreme conditions. Taking what we’ve learned from off-road circuits, we’ve brought it to the Harley market.”

“Our new four-piston calipers for the late-model Bagger bikes and Softails are great examples. We’ve changed and refined a lot of the internals and switched up piston sizes, among other things. Those calipers stop great, and they totally resist heat build-up.”

Some of the other improvements include lengthening calipers and adding air passages for additional cooling. GMA brakes are manufactured out of higher quality billet aluminum. They raised the bar from 6061 to 7075 and ultimately to 2024. It’s more expensive but won’t flex, which causes heat, or expand as much. This switch alone enhances brake lever action for a more solid and quicker rotor grip.

The JAMAR team developed a bore coating allowing caliper pistons to slide freely and reduce friction, consequently reducing heat. We won’t give any secrets away here, but BDL and the GMA team also developed their own seals with a higher quality material to specifically withstand heat.

The company growth didn’t stop at the addition of JAMAR. Recently BDL became the parent company of BDS, Blower Drive Service, a giant in the performance auto industry since 1969. Now BDL is in the automotive supercharger business. Immediately they introduced brand-new billet superchargers, precision machined three-lobe rotors and many more updates and refinements for those venerable BDS huffers. Of course, they are already developing a blower system for Harleys.

This round, we are going to focus on new GMA braking components. They are refining their rotor materials and pads. Organic pads seem to work best with the popular stainless steel rotor material. Unfortunately stainless isn’t the best rotor material and actually sweats in extreme heat, but riders don’t want ugly ductile iron rotors on their bikes. It is still the best possible material. They are now working on enhanced, sharp looking floating centers and ductile iron rings, to afford sharp looks matched to wheel appearance and performance.

Here’s the rundown to GMA brake components.

Model A Calipers (2 Piston)

Twin piston calipers machined from heat-treated, aircraft quality, billet aluminum. Featuring two 1-5/8-inch diameter, centerless ground pistons, which are hard anodized for long wear and performance. This precision caliper has high-tech looks and delivers outstanding braking power. Each caliper body is clear anodized to protect the aluminum machined finish. The proper bracket is included for each application.

Model B Calipers (2 Piston)

Compact and lightweight describes this modern design’s best features. Two 1-5/8-inch centerless ground pistons hard anodized for long wear and performance. Top quality organic brake pads are featured on each caliper. Clear anodizing seals the aluminum housing for a long life and lasting luster. The proper bracket is included for each application.

A dramatic improvement over the original OEM brakes. Fits front single disc FX and Sportster models 1974 to early 1977. Contains all the necessary parts, including mounting hardware, spacers and bracket. Will require removal of the rotor from the hub and spacing the rotor for adequate caliper-to-spoke clearance. These spacers are included with the kit. A fitting is provided to adapt to the stock brake line.
Designed for wheels 19-inch or smaller.
Kit requires a 5/8-inch bore master cylinder.

Fits all models from late 1984 to 1999. New one-piece design bolts directly to lower leg, eliminating the need for a bracket. Kit requires 5/8-inch bore master cylinder for single disc and ¾-inch bore for dual disc. Will not fit narrow glide 21-inch wire wheel. This kit is designed to accept 10mm (3/8-24) banjo bolt.


A modified version of the GMA B caliper family is designed with the custom builder in mind. This is not a direct bolt-on kit. Removal of the original factory brake mounting tabs may be required. Converts OEM drum brake front end to 10-inch dual discs. Bolt-on dual disc kit mounts to original fender mounts. All mounting hardware and brackets are included. Kit includes aluminum spacers for mounting either the narrow, custom after-market fender or the OEM 16-inch fender. 16-inch or 19-inch wheels only. The kit requires ¾-inch bore master cylinder.

Front Single Disc, FXSTS 1988-1999
Fits Harley Davidson FXSTS springers. Uses factory axle anchor rod and bronze washers (not provided). Kit uses stock OEM master cylinder. Will not fit FLSTS (Old-boy).


This caliper kit is a direct bolt-on replacement, which fits 1984-1986 Softail frames. Includes all mounting hardware, spacers and bracket. The bracket is black anodized aluminum. Uses stock HD* brake line. Will accept stock OEM master cylinder.


This caliper kit is a direct bolt-on replacement, which fits 1987 to 1999 Softail frames. Includes a one-piece black anodized bracket, eliminating the need for spacers. Clean and simple. Uses stock HD* brake line. Will accept stock OEM master cylinder.

Each kit uses the same caliper and bracket. Correct brake line adapter fittings and axle spacers provided. All kits require a 5/8-inch bore Master Cylinder.
GMA 203 Rear Kit for H-D Sportster 1979-1981
GMA 204 Rear Kit for H-D Sportster 1982-Early 1987
GMA 205 Rear Kit for H-D Sportster late 1987-1999


Hand Controls

GMA offers an all-new look for handlebar controls for every possible application. The universal style is intended for those building a custom bike and choosing to eliminate switches from the bars. GMA offers a switches-and-buttons design for both the clutch and brake side. Available in black, polished and chrome finishes.


Handlebar brake master cylinder
5/8-inch bore single disc
1973-2006 Softail fits 1-inch bars


Handlebar brake master cylinder
5/8-inch bore with switch kit single disc
1973-2006 Softail
Fits 1-inch bars


Handlebar hydraulic clutch master cylinder
9/16-inch bore
Fits 1-inch bars


Handlebar hydraulic master cylinder
9/16-inch bore with switch kit
Fits 1-inch bars


Handlebar clutch perch
1984-2006 with OEM style cable
Fits 1-inch bars


Handlebar clutch perch with switch kit
1984-2006 with OEM style cable
Fits 1-inch bars

Next we will cover GMA Forward Controls.

GMA Forward Controls

GMA has designed what we believe to be by far the most streamlined forward controls, taking customizing to the ultimate level. The unique design and features make our controls a must for any stock or custom application. We manufacture our controls with the utmost care for quality and fit.
Offered in polished, chrome and black finish.

The GMA line also includes Brake Pedal Covers
Custom Grips
GMA Floorboards
GMA Pegs
GMA Switch Covers


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