GMA brake kits are designed to use the stock factory brake lines and fittings. Most GMA calipers are drilled and tapped 1/8-27 NPT and the correct brake line adapter fittings are included for a no-hassle fit. Do not screw a banjo bolt directly into a GMA caliper, unless otherwise specified. You will ruin the threads and cause the banjo bolt to bottom out and interfere with proper piston function.

Tech Tip - Bleeding problems

This is the single most common tech problem that we receive. Small motorcycle brakes with multi-pistons are difficult to bleed - especially on rear applications where the caliper is higher than the master cyclinder.We recommend the use of an EZE-bleeder, an inexpensive syringe type bleeding tool that will eliminate all of the problems. Trust us and save yourself some grief. Buy one!

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Tech Tip-Rear Master Cylinders

This falls into two categories:

1) 1973 to mid 1984 - These models use a 3/4" diameter bore master cyclinder and will not function correctly with GMA multi-piston calipers. The bore is too large and will not create sufficient pressure. We have learned from years of testing that it is absolutely necessary to use a 5/8" diameter cylinder on all of these models.

2) 1984 to present - The factory rear master cylinder is a 5/8" bore and will function correctly with GMA rear brake calipers. Wrong bore sizes can result in tipped pistons, improper pad wear and can cause pistons to bind, locking up brakes.

Tech Tip-Stainless Steel Rotors

This is the single most misunderstood part that is installed on HD motorcycles. As compared to ductile iron, stainless steel is a poor choice of material. It has a poorer friction surface, does not dissipate heat as well and will ring like a church bell.

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Tech Tip-General Tip #1

GMA's high performance brakes are designed to be mounted solid. To eliminate vibrating and squealing problems associated with stainless steel rotors, we recommend ductile iron.

Tech Tip-General Tip #2

Hard pedal, No Stop? 5/8" bore master cylinder must be used on single disc, 3/4" bore on dual disc.

When using banjo style brake line fittings, always use OEM style (O-ring) washers. Every time bolts are loosened, washers must be replaced.

Tech Tip-General Tip #4

GMA calipers use organic Kevlar brake pads, which are most compatible with all cast iron rotors. Kevlar pads can cause squealing noises when used with stainless steel rotors. Semi-metallic brake pads may cure squealing problems if you insist on stainless steel rotors.

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© 2008. GMA Engineering.
The words Harley-Davidson or HD are not intended to imply that any of these products are HD original equipment or are sanctioned by the Harley-Davidson company. The words are only used to identify products and models.

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