Whether you’re setting up a brand new fork or just want to get rid of a spacer stack, cutting down a steerer tube isn’t as tricky as you might think. As long as you have the right tools and are very, very careful, that is.
That said, new forks will need to be fitted with a crown race before installation, which requires specific and expensive tools and is best dealt with by your local bike shop.
This process will work for aluminium and carbon steerers on both road and mountain bikes, so watch the video here to see James Tennant talk you through it.
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
- Paper cloth
- A small flathead screwdriver
Step 1. Remove and mark
Remove the wheel from the bike and detach your brake caliper and hose from the fork. This process varies depending on whether you have rim or disc brakes, but will usually only involve one or two hex bolts.
Undo the stem top-cap with a hex key (usually 4 or 5mm) and remove any spacers you have above the stem.
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.
Take a small flathead screwdriver and use it to score the steerer tube, as close to the top of the stem as you can. You’ll be basing your cutting point on 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 tube and rest the bars gently on the cables
Remove any remaining spacers and headset washers, again, taking note of the order you remove them.
You should now be able to tap out the fork.
Step 2. Measure and cut
Place the saw guide onto the steerer tube with the clamp side closest to the fork leg. Using a loose spacer as a guide, carefully score a second line into your steerer, about 3mm below the first. This is the line you will cut along.
Usually, you’ll need to reposition or remove the star nut at this point, depending on how much tube you’ll be cutting off. We've put together a video to show you how to do that here.
Align the guide slot with your scored cutting point and close the clamp.
Take the saw and rest it in the cutting guide. Start sawing, remembering that hacksaw blades tend to work in one direction and that smooth strokes will give the best cut.
Saw through the steerer tube until the excess falls off the end.
It’s likely that there will be a burr or two remaining, so use a file to clean up the cut.
Step 3. Re-install
You now need to re-assemble the headset spacers and washers — not forgetting any bearings you may have removed.
Return the top cap and wind in gently until it takes up the slack — it doesn’t need to be tight.
When the headset is tight, you can align the bars and tighten up the stem bolts observing any torque settings printed on the step — this is especially important if the steerer tube is made of carbon.
Return the brake and wheel and the bike should be ready for a test ride.