Caleb MorganBy Caleb Morgan

Updated November 2026

A bike fork size chart tells you which fork dimensions will fit your frame, wheel and headset. By the end of this guide you will know the four measurements that matter, how to read them against a chart, and how to avoid ordering a fork that won’t fit. Fork sizing is less about a single number and more about matching a few related specs to the bike you already have.

Know the Four Measurements a Fork Chart Uses

Most fork charts list the same core specs. Learn what each one means before you compare numbers.

Shopping for one? See our guide: 5 Best Road Bike Shoe Size Charts (2026): Expert Picks.

  • Wheel size: The diameter printed on the tire, such as 700c (road), 27.5-inch or 29-inch (mountain), or 20-inch and 26-inch (kids and older bikes). A fork is built for one wheel size.
  • Axle-to-crown (ATC) length: The distance from the axle centerline to the top of the crown, where the fork meets the steerer. This sets how high the front end sits.
  • Steerer tube diameter and length: The steerer runs through the headset. Common diameters are 1-1/8 inch, 1.25 inch and 1.5 inch, and the length must suit your headset stack.
  • Offset (rake): The distance the axle sits forward of the steerer centerline. It affects steering feel and trail, so keep it close to the original fork.

Step-by-Step: Measure Your Current Setup

If you are replacing a fork, measure the old one before you shop. Compare these numbers to the chart rather than guessing from the model name.

  1. Note the wheel size printed on the tire sidewall.
  2. Remove the front wheel and measure from the center of the axle to the underside of the crown. That is your ATC length.
  3. Measure the steerer diameter at its widest point with calipers.
  4. Measure the steerer length from the top of the crown to the top of the steerer, then check the headset stack height if you are changing it.
  5. Check the offset, usually stamped on the fork leg or listed by the manufacturer.

Match the Chart to Your Frame and Headset

Once you have your numbers, find the row in the chart that matches your wheel size and steerer type. Then check compatibility with the frame.

Confirm the headset standard, since the steerer diameter and cup type must match. Check the brake type too: rim brake forks have brake bosses, while disc forks need mounts for your rotor size and thru-axle or quick-release style. If your bike uses a thru-axle, the fork’s axle diameter and length must match exactly.

Frame manufacturers often publish the fork specs your frame accepts. When in doubt, follow their specification over a general chart.

Quick Reference Table

Spec What to match Where to find it
Wheel size Exact tire diameter Tire sidewall
Axle-to-crown Original or frame-specified length Measure or fork label
Steerer diameter Headset compatibility Caliper measurement
Steerer length Headset stack and handlebar height Measure crown to top
Offset Close to original for handling Fork label or spec sheet

Check Tire Clearance After You Choose

A longer axle-to-crown length raises the front of the bike, which can change geometry and steering. A fork that is too tall can also strain the headset. Before you commit, check that the tire clears the crown and the fork legs at full compression, and that brake or fender mounts line up. If you are changing wheel size or tire width, recheck clearance with the new tire installed.

Common Mistakes

  • Matching only the wheel size and ignoring axle-to-crown length.
  • Assuming a 1-1/8 inch steerer fits a 1.5 inch headset, or the reverse.
  • Ignoring disc versus rim brake mounts.
  • Choosing a fork with very different offset, which can make steering feel unfamiliar.
  • Forgetting that thru-axle and quick-release forks are not interchangeable.

A set of digital calipers makes steerer and axle measurements far more reliable than a ruler. View on Amazon

A metal tape measure with a clear fold-out hook helps with axle-to-crown measurements on a bike that is still assembled. View on Amazon

FAQ

Can I use a fork with a different axle-to-crown length?

You can, but a longer or shorter fork changes the height of the front end and can affect handling and tire clearance. Stay close to the original length unless the frame manufacturer approves a change.

Does the steerer length have to be exact?

Not exactly, but the steerer must be long enough to fit your headset stack and handlebar height, and short enough that it does not bottom out. Cut only after you have a final fit, and follow the manufacturer’s limits.

Is the wheel size on the chart the same as the one on my tire?

Usually yes, but check carefully. Wheel sizes have overlapping names, such as 27.5-inch and 650b, so confirm the ETRTO or bead-seat diameter printed on the tire.

Conclusion

A bike fork size chart is most useful when you measure your current setup first and match wheel size, axle-to-crown length, steerer specs and brake mounts together. Check tire clearance and confirm with your frame’s specifications before buying. If you are unsure about a safety-critical fit, consult a qualified bike mechanic.

Ready to choose one?

Caleb Morgan

About Caleb Morgan

Caleb Morgan is part of our editorial team and reviews and edits our cycling for beginners guides, checking product details against manufacturer specifications and owner feedback.