This guidance is primarily for owners of original-era BMX Freestyle bikes from model year 1986 onwards and concerns the front fork brake assembly and the spindle specification - length and diameter.

Most side-pull BMX brakes from the late 1970s and 1980s used an industry-standard front caliper spindle measuring between 5.35 mm and 5.75 mm in diameter (thickness)and approximately 48 mm in length. This front spindle specification applies to nearly all BMX bikes built from the late 1970s through the mid-1980s, and in many cases, even beyond 1986.

However, as BMX riding evolved and equipment demands increased, Dia Compe introduced a new spindle size for certain higher-specification freestyle OEM factory-assembled complete bikes around 1986. This new design featured a larger spindle diameter for added strength and a “recessed” Bolt/Allen Nut at the rear of the fork. This upgrade eliminated the unsightly nut and, more importantly, ensured riders would not snag their feet during tricks. Some of the bike companies increased the bore of the spindle hole on their high-end model forks to around 8 mm and added a small countersink so the neart allen nut would sit inside.

The Standards and Upgrade Option.

Because most bikes from this era retained the smaller spindle bore even after the introduction of the recessed nut and 32 mm spindle, we have chosen to produce these brake sets with the industry-standard 48 mm-long, 5.35-diameter spindle and nut assembly.

However, we have ordered a small quantity of 32 mm spindles with recessed Allen nuts for customers with compatible bikes, which can be purchased inexpensively and separately. These spindle upgrades can be assembled with the RVBMX X Dia Compe 883 Collaboration brake sets. Customers with Freestyle bikes from the 1985 model year onwards will need to measure the spindle bore in their form to determine if the recessed spindle will work on their bike. If not, the stanrdard version will fit right out of the box.

To Recap

Example A shows the standard spindle: 48 mm long and 5.35 mm in diameter. This is the version included in your Collaboration 883 brake set and will fit most, if not all, BMX bikes from the 1970s and 1980s. This spindle includes the Allen adjustment bolt head at the front of the assembly.

Example B shows the recessed 32 mm long brake spindle with the threaded recessed sleeve - diameter 7.85 mm. This version is for certain high-specification freestyle bikes from around the 1986 model year, built with a fork that has a wider spindle bore hole—approximately 8 mm in diameter. Be sure to check your bike, as only some production runs included this upgrade while others did not.

The Recessed 32 mm Spindle can be purchased as an add-on at the link below if required. Be aware that customers will need to disassemble their purchased set and reassemble it with the new spindle. According to Dia Compe, this spindle does not require the half-moon washer between the front of the caliper and the fork.

Of Note: Redline by Kastan RL 20 II Prostylers built prior to December 2025 do not include the wider bore hole.

EXAMPLE A - STANDARD SPINDLE 5.35MM THICK AND 48 MM LONG.

The standard Nut and Bolt assembly compatible with most, if not, all, BMX bikes built in the 1980s era.

EXAMPLE B - UPGRADE SPINDLE 5.35MM THICK AND 32 MM LONG.

The Upgrade pption featuring a recessed sleeve at the rear of the fork spindle. These are compatible with a small percentage of BMX Freestyle bikes from the 1986 era onwards and have a larger bore hole drilled in the fork. Please check your fork prior to purchasing.