How to fit a suspension fork - MBR


Measure twice, cut once.

Ensure a perfectly cut and fitted fork with our step-by-step guide on how to fit a suspension fork to your mountain bike.

Words: Charlie Collins

  • Time taken: 30-45mins
  • Difficulty: Moderate
  • Allen keys
  • Pencil
  • Mallet/hammer
  • Plastic pipe/crown race tool
  • Hacksaw/cutting guide/pipe cutter/tape
  • Rounded file
  • M6 bolt
  • Star nut setting tool
  • Grease.

You’ve just blown your hard earned on a shiny new set of forks and now it’s time to get them the bike. There are several key points to look out for, so follow this guide to get it right first time.

Before you start, you want to ensure the steerer tube is the correct diameter for your frame. Nowadays, many frames make use of forks with a tapered steerer, going from 1.5in at the crown race to 1 1/8in. Other standards include the straight 1 1/8in and the less common 1.5in, so be sure to check what you need. It’s also important that the forks suspension travel is suited to the bike, within the manufacturers given range.

>>> How to set up mountain bike suspension

The main task to get right is cutting the steerer tube. If you cut it too long you can always take more off. However, too short and it could mean you have a costly error on you hands, as usually the crown-steerer assembly is one piece – measure twice, cut once.

Steps 5-7 show three different methods of cutting down the steerer tube. All will give a top-notch finish, but the guide and pipe cutter will guarantee a straight cut. Steps 9 & 10 show two ways of fitting the star nut. The nut setting tool will provide textbook results, whereas the screw method can be difficult to get perfect. While performing work on this area of the bike, it’s always worth checking the associated parts such as the headset and giving them a good clean! The guide begins assuming there is no fork in the bike to start with.

fit suspension fork

1. Fit crown race to steerer tube. Use crown race setting tool or plastic pipe if not a split crown race.

fit suspension fork

2. With the headset bearings in position, insert fork in to frame. While holding fork in frame slide upper crown race and upper cap on to steerer.

fit suspension fork

3. Slide on required amount of headset spacers. Push the fork up to remove any play and fit stem, nip the stem bolts tight.

TOP TIP: You may want to add one or two extra headset spacers if you aren’t sure of your preference yet.

fit suspension fork

4. Using the pencil, mark a line around the top of the stem, you will be cutting 2-3mm below this line. Now remove the fork and parts from the frame ready to cut the steerer tube.

fit suspension fork

5. Method one. Clamp steerer tube on the excess material. Wrap tape around the steerer to provide a defined guide line. Using a hacksaw, cut the tube following the line as straight as possible.

fit suspension fork

6. Method two. Unwind/open the pipe cutter and fit to steerer. Turn knob until it closes down on tube, make one full rotation of tool. Turn knob a touch more and rotate again, repeat until the excess tube drops off.

fit suspension fork

7. Method three. Fit cutting guide to steerer. Hold down on worktop or clamp in position and cut with hacksaw.

fit suspension fork

8. Clean off any sharp edges using a file, focusing on both on the inside and outside of the steerer.

fit suspension fork

9. Method one. Thread an M6 bolt in to star nut and hold in place over steerer. Tap in to place, adjusting the angle to ensure straightness, about 15mm deep.

TOP TIP: When knocking star nut in place, ensure you don’t damage the bottom of your forks. Sit them on a rag.

fit suspension fork

10.Method two. Thread star nut on to setting tool and knock in to place.

fit suspension fork

11. Grease the headset bearings and races, then slide fork into frame.

TOP TIP: If you want to check the steerer is the right length before fitting the star nut, simply slide the fork back in as per steps 2-3.

fit suspension fork

12. Slide on upper headset parts, spacers and stem. Fit top cap with bolt and tighten until any play in headset is removed.

fit suspension fork

13. Fit the front brake, ensuring the hose runs cleanly down the fork leg. Fit front wheel.

Pro Tool: Park Tool TNS4 threadless nut setter, £29.99

Park’s heavy weight tool does more than press the star nut in perfectly straight, it also sets it to the correct depth so you can have no fear of knocking it too far in. There are cheaper tools available, and certainly worth having one the toolbox.