Disc brake mounts

Disc tabs and caliper mounts for BMX Race

This is the small part that decides whether a disc brake kit goes on the bike or stays in its box. A disc brake mount does two distinct jobs: it positions the caliper correctly over the rotor, and it takes the braking torque without flexing. On a race frame, where the dropout is slim and chain tension is adjustable, that fitment is anything but trivial.

The three families of mount

• The frame-specific disc tab: machined for one model and one model year, it follows the shape of the dropout and bolts to inserts provided by the frame manufacturer.
• The axle-clamped plate: sandwiched between the dropout and the wheel nut, with a lug or a screw to stop it rotating. This is the answer for a frame with no original mount.
• The standard or diameter adaptor: it converts an IS fitting to Post Mount, or offsets the caliper to move from a 140 to a 160 mm rotor.

IS and Post Mount: two spacings not to confuse

The IS fitting (International Standard) takes two M6 bolts perpendicular to the plane of the rotor, on a 51 mm spacing; it almost always needs an adaptor to accept a modern caliper. Post Mount presents two threaded holes parallel to the rotor, 74 mm apart, onto which the caliper bolts directly with some lateral centring available. Note the spacing and the bolt orientation before ordering.

How to choose your mount

Four pieces of information are enough: frame brand, model and year; the diameter of the rotor fitted; the caliper mounting standard; and the rear axle diameter, generally 10 mm in BMX Race. A mount designed for a 10 mm axle will not fit a 14 mm axle hub as it is, and a plate drawn for one frame does not transfer from brand to brand: Meybo, Chase, Supercross, Pride and Position One each have their own dropout geometry.

Materials and hardware

Plates are machined from 6061 or 7075 aluminium, often anodised to resist corrosion, with stainless steel hardware. The M6 caliper bolts are generally torqued to between 6 and 8 Nm with a low-strength threadlocker: too little torque produces a squeal at every stop, too much marks the thread in the plate.

Fitting and checks

Fit the wheel and set chain tension before finally tightening the caliper: on a frame with horizontal dropouts, any movement of the axle also moves the rotor within the caliper. Then check that the rotor is centred between the pads, and recheck the bolts after the first few motos, while everything settles.

The BMX RACING advice

Compatibility here comes down to millimetres and depends entirely on the frame. Send us a photo of your dropout with the brand, model and year: we identify the plate or adaptor that suits and, if needed, complete it with the right brake disc, a matching caliper or a full disc brake kit. Dispatched within 24 to 72 hours, you can spread the cost over 2 or 3 payments.