Bolts and Hardware

BMX race bolts: the part nobody thinks about until it fails

One bolt lost at a session puts a whole bike out of action. Yet on a BMX race bike the hardware sees wildly different loads from one point to the next: a chainring bolt does not work like a seat clamp bolt, and the choice of material should follow that reality rather than the colour of the frame.

Titanium, steel or aluminium: what each material is for

• Stainless and chromoly steel: the reliability benchmark. The default choice everywhere loads are high and weight matters little.
• Grade 5 titanium: clearly lighter than steel for comparable strength, and corrosion-proof. The only weight saving that genuinely makes sense at loaded points.
• 7075 aluminium: very light but unforgiving. Keep it for lightly loaded fixings and accessories; never on a chainring, a stem or a brake caliper.

Drives and tools

The 4, 5 and 6 mm hex socket covers most components. Torx, in T25 and T30, is gaining ground: it transmits more torque, centres better and rounds out far less on alloy or titanium bolts. Always use a key in good condition, seated fully home, because most stripped bolts are ruined by a worn tool rather than by over-tightening. A torque wrench remains the best value tool in the box.

The main bolted joints on a BMX

Chainring bolts and spacers, stem faceplate and steerer clamp bolts, seat clamp bolt, brake pad and caliper bolts, tensioner screws, pedal pins, number plate bolts. Each has its own diameter, length and head shape: a bolt that is too long goes through and fouls something, one that is too short does not engage enough thread. Measure length under the head, never the whole bolt, except on countersunk heads. Chainring bolts are ordered as a kit with their spacers, allowing for whether your BMX chainring is a single or double set-up.

Torque figures and good practice

Always respect the torque stamped on or quoted for the component, not the bolt. Tighten in a criss-cross pattern and in successive passes on stem faceplates and chainrings, so pressure is spread over the whole surface. On a titanium bolt running into an aluminium thread, use anti-seize compound, or galvanic corrosion and friction between the two metals will eventually weld the parts together. Low-strength threadlock on bolts exposed to vibration, and never high-strength threadlock on aluminium.

Checks and replacement

Go round the bolts before every moto and after every crash: chainring, stem, seat clamp, tensioners, pads. Replace without hesitation any bolt with a marked drive, a thread that binds as it goes in, or one that has been taken past its torque figure. On a growing rider's bike, use the seasonal strip-down of your crank arms to renew the hardware exposed to mud and the pressure washer.

The brands available

Box Components and Tangent offer complete kits by component, with matching anodised colours. Elevn and Chase cover the hardware for their own parts, which guarantees the right length and the right drive. Insight provides simple references for routine maintenance and young riders' builds.

The BMX RACING advice

Send us a photo of the missing bolt with a ruler alongside it: we will identify diameter, thread pitch and length, and offer the equivalent in the material that suits that location. Browse our drivetrain components too, to group your order. Dispatched within 24 to 72 hours and you can spread the cost over 2 or 3 payments with Alma.