Whether you’re setting up a brand new fork or just want to get rid of a spacer stack, cutting down a steerer tube is a straightforward process. As long as you have the right tools and are very, very careful, that is.
This process will work for aluminium and carbon steerers on both road and mountain bikes.
How to cut down a fork steerer tube
You will need
- A saw fitted with the appropriate blade for your steerer tube material
- Saw guide
- Degreaser
- Paper cloth
- File/sandpaper
- A permanent marker pen
1. Disassembly
Remove the front wheel and detach your brake caliper and cables from the fork.
Undo the stem top cap with a hex key (usually 4 or 5mm).
While doing this, take note of the parts you have removed and the order they were arranged in — you will need to re-assemble them in the same way.
2. Measure and mark
Decide how long you want your steerer tube to be. This is up to you, but we recommend leaving a spacer above your stem in case you want to raise the bar in future.
Use a permanent marker to draw a line around the steerer tube, above the point where you want your steerer tube to end. You’ll be cutting according to this mark, so you need to be sure you want your stem at this height, or lower.
Undo the stem mounting bolts, remove the stem from the steerer tube.
Remove remaining spacers and headset washers, taking note of the order you remove them.
You should now be able to remove the fork. It may require some taps with a rubber mallet.
3. Fit the saw guide and cut
With the fork removed, place the saw guide onto the steerer tube with the clamp closest to the fork legs.
Line the steerer tube up so you're removing all the pen mark plus 3mm below it. This will give the top cap the space to preload the headset without bottoming out on the steerer tube.
If you have a star nut inside your steerer tube, check that it is fully below the area you're removing. You don't want to cut into it. If you need to push the star nut further into the steerer tube then do so. Just remember that they only go one way; downwards further into the steerer tube.
Align the guide slot with the point where you want to cut and tighten the clamp.
Put the cutting guide securely in the vice.
Saw through the steerer tube until the excess falls off.
4. Deburring
Use a file or abrasive paper to clean up the cut, both inside and outside the steerer tube.
Use a cloth to remove any metal particles created by the cutting and filing process.
5. Re-installation
Put the fork back into the headtube, remembering to reassemble all the parts of the headset in the correct order.
This is a good time to clean and add some fresh grease onto your headset bearings if you wish.
Add the headset spacers and stem in the order you require.
Fit the top cap and wind in gently until it takes up the slack, it doesn’t need to be very tight. Tighten until there is no back-and-forth play in your headset, but not so tight that the headset binds or rumbles when you turn the handlebars.
Refit the brake and wheel.
With the bike on the ground, align the bars and tighten up the stem bolts to the manufacturer's torque settings.
How short should I cut a fork steerer tube?
A good benchmark is one stem stacker above where you currently run your stem. This gives you some wiggle room should you want to raise your handlebar in future.
If you’re on a budget, it’s also worth considering the resale value of your fork; the longer the steerer tube is, the greater the number of potential buyers for your second-hand fork!
