BMX Race Topbolts
Headset loose or fork not sitting tight? The choice between top bolt, star nut, and expander is critical for safety in racing. While steel forks use classic bolts, carbon steerers require special internal systems. Forks with aluminum steerers, on the other hand, rely on proven technology. Here you find the right solution for your material – for maximum safety in the final sprint.
BMX Race Topbolts FAQBMX Race Topbolts Range
BMX Race Topbolts FAQ
What is a top bolt or expander in BMX Race?
These components have two tasks: They preload the headset so that the fork sits in the frame without play, and they additionally secure the stem against slipping upwards. In BMX racing, the material of your steerer tube is decisive for choosing the right part.
Which systems exist and which one do I need?
Attention: The wrong choice can damage your fork! Distinguish precisely:
- Expander (for Carbon Steerers)
- Carbon steerer tubes are sensitive to external pressure and internal scratches. You must never use a star nut here! Instead, use an expander. This clamps gently from the inside against the shaft by spreading out and supports the carbon tube against the pressure of the stem.
- Star Nut (for Aluminum Steerers)
- Many carbon forks feature a steerer tube made of aluminum. Since aluminum is robust enough, classic star nuts are often used here. These nuts are hammered into the shaft and bite into it permanently.
- Topbolt (for CrMo Forks)
- Forks made of Chromoly steel usually have a fixed internal thread welded into the shaft. For this, you need classic Freestyle Topbolts. These are screwed directly in. Check the thread size of your fork beforehand (e.g., M24 or M25).
What materials are used?
- Aluminum (6061-T6)
- Both expanders and top bolts are mostly made of lightweight aluminum to keep the weight at the front low.
- Steel
- Star nuts are made of hard spring steel so that they can securely bite into the wall of the aluminum steerer.
- Carbon Cap
- Some high-end expanders use a cover cap made of carbon for the ultimate weight advantage and racing look.
How do I install top bolts and expanders correctly?
- For Carbon Steerer (Expander): Insert the expander. Tighten the internal clamping bolt with an hex key (observe torque, usually 5-6 Nm) until it sits firmly.
- For Aluminum Steerer (Star Nut): The nut must be driven in straight and deep enough (approx. 15mm). Ideally, use a setting tool to avoid tilting.
- For CrMo Fork (Topbolt): Lightly grease the thread of the Topbolt and screw it into the fork thread by hand.
- Mount the stem and tighten the top adjustment bolt until the headset is play-free. Only then clamp the stem on the side.
What do the specifications mean?
| Term | Explanation | Examples/Available |
|---|---|---|
| 1 1/8 Inch | The standard diameter for almost all modern BMX Race steerer tubes (Pro Sizes). | Standard for Expanders/Star Nuts |
| 1 Inch | A smaller diameter for Junior/Expert forks. Narrower expanders are needed here. | Junior / Expert Bikes |
| Thread Pitch | Only important for CrMo forks (e.g., M24x1.5). Must match the internal thread exactly. | M24 x 1.5, M25 x 1.5 |
