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How to install a fork with a carbon steerer

CarbonCycles have been in the business of making the best rigid aftermarket forks for a number of years, and we know how vital the correct installation of your new fork is. In this installation guide, we will look at forks with a carbon steerer and take you through the steps of cutting the steerer to the correct size and installing it correctly into your frame and finally attaching the stem securely to the steerer. If you should have a fork with an alloy steerer, then we would suggest looking at the 'alloy steerer' specific installation guide here.

After the step-by-step guide, you will also find a list of frequently asked questions that will hopefully help you fit your new forks.

Tools for the job:
- Crown race setting tool (recommended)
- Compression plug
- Steerer tube cutting guide (recommended)
- Hacksaw with a suitable blade
- Fine grade sandpaper
- Permanent marker or tape
- Torque wrench
- Grease
- Carbon assembly paste

Before you start the assembly, please ensure that all parts are compatible.

1.) Fit the crown race to the steerer tube by applying a small film of grease to the inside and bottom of the crown race and using the crown race tool to put it into place.

2.) Insert the fork into the frame and headset so that all parts of the headset are in the correct place.

3.) Work out the number of spacers you want underneath the stem. Don't exceed 40 mm of spacers underneath your stem.

4.) Install the stem on the steerer and slide it down to sit firmly against the spacers on the top of the headset (if spacers are required). Gently tighten the stem's steerer clamp bolt(s) just enough to hold the assembly in place.

5.) Use a marker pen to draw a line on the steerer tube along the top end of the stem.

6.) Remove the stem, spacers and parts of the headset and slide the fork out of the frame.

7.) As we intend for the carbon steerer tube to go entirely through the stem, mark another line 2 mm above the 1st line, so that the steerer (once cut) is slightly longer than the top of the stem.

8.) Use your steerer tube cutting tool/guide and a hacksaw with a suitable fine graded blade to cut the steerer in the correct position. (Note: To give you a more detailed idea of how to cut your steerer, we have chosen the following video: In this video, you will get some general information about preparing, cutting, and installing your new fork, but we primarily wanted to show you the cutting process and tools needed for the job.)

9.) Use the fine grade sandpaper to smooth off the cut edge.

10.) Check over the steerer's surface for scratches and imperfections, which might affect the strength of the steerer.

11.) Now it is time to install your compression plug. Under no circumstances use a star nut in a carbon steerer as it might damage the steerer.

12.) To prepare your compression plug, make sure that you grease the threads of the bolts in the plug, but do not apply any grease onto the surface that will clamp against the inside of the steerer.

13.) Insert the compression plug into the steerer so that it sits inside the steerer on the same position where the stem will clamp onto the outer part of the steerer later on.

14.) Use your torque wrench (set to 6-9 Nm) to secure and tighten the compression plug.

15.) Reinsert the fork through the frame and headset. Install the number of spacers you worked out in step 3 (don't exceed 40 mm of spacers underneath your stem).

16.) Slide your stem back onto the steerer. You should have approx. 2 mm of the steerer showing above the top of the stem.

17.) To securely tighten down the stem and correctly adjust the headset, use a 5 mm spacer on top of the stem. This will allow your top cap to push the stem down so that you can find the sweet spot between being able to turn the stem/handlebars freely and having no play in the headset.

18.) Once you have found the setting and your stem is in line with the front wheel, use your torque wrench to tighten the stem clamp bolts. When tightening the stem bolts do not fully tighten one bolt and then fully tighten the other bolt, instead tighten one a little and then the next a little, alternating between the 2 bolts until both reach 6-7 Nm.

Frequently asked questions:
Can I use a star nut in a carbon steerer or should it be a compression plug?
You should always use a compression plug in a carbon steerer, as it doesn't damage the inside of the steerer and spreads the clamping load over a larger area. Under no circumstance, use a star nut. They are only for use in alloy and Chromoly steerers.

How long should the steerer be in relation to the stem?
We would strongly recommend that your carbon steerer be approx. 2 mm longer than the line you would draw along the top of the stem when your stem is at your preferred position. You should run a 5 mm spacer above the stem, which will allow you to clamp down the top cap sufficiently and therefore preload the headset correctly.

Should I use grease or carbon assembly paste in the assembly?
You can use grease on the crown race as well as the threads of the compression plug. Do not use any grease in between the stem and the carbon steerer. You can use carbon assembly paste on the clamping surface of your compression plug so that it will increase the grip it has on the inside of the carbon steerer.

How many spacers can I have below and above my stem?
You should not have more than 40 mm of spacers underneath your stem, as it will increase the load and strain on that part of the steerer and might result in damage and potential fracture. Similarly, you should not have more than 10 mm above the stem, to ensure that the compression plug sits in the clamping area of your stem, rather than above it. If it sits above the stem, the compression plug's outward-facing load, which has no contra force normally generated by the stem, could damage the carbon steerer tube.

Where should the compression plug sit in relation to the stem?
The compression plus should sit in the clamping area of the stem. For that reason, we strongly recommend having a maximum of 10 mm of spacers above the stem.

Is a torque wrench important, and what key settings do I need to look out for?
Yes, you should definitely use a torque wrench for the correct installation of your carbon steerer fork. Incorrect torque settings can damage the steerer, rendering it unsafe, dangerous, or deadly to ride. The approx. torque setting for your compression plug is 6-9 Nm. The approx. torque setting for your stem bolts is 5-6 Nm. The torque setting for the top cap should not exceed 5 Nm as it can restrict the headset's free movement and damage the bearings. Please refer to the assembly instructions of the various components to find the manufacturer’s recommended torque settings.

What should I look out for once the fork is installed and in use?
Periodically remove, clean and inspect your fork for damage, cracks or any other damage. Any questions about markings or cracks on the fork should be directed to CarbonCycles immediately.

Please note that our installation guides are only advisory and that we cannot be held accountable for any damage or cost in relation to this article. If you use the information in this document, you take full responsibility for the outcome. If you are at all unsure please have a qualified bicycle mechanic do this job for you. Incorrect installation can lead to failure and serious injury.

by Mikethebike     Tue Feb 16, 2021

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