Hi all, I want to cut my steerer such that there are no spacers above (or below) the stem. Mine is a no name fork that came with my KHS, and it has a carbon steerer. The compression plug and top cap are FSA brand ones and look pretty standard. I read Trek/Bontrager recommend a spacer above and below the stem, but specialized doesn’t make any such suggestion that I found. Specialized has a fancy compression plug though. The question is, do I need a special top cap, or can I just cut it and assemble it? I of course don’t want to end up with a cracked steerer tube.
If you cut your steerer, you’ll may need a new start-nut (compression plug)… or you need to take smaller cuts and hammer the nut down further after you make each cut. I’ve used a special tool to hammer this in so it’s properly aligned and at the correct depth. I wouldn’t want to tackle this without the correct tools. That includes a proper cutting guide as well so you get a clean straight cut.
I installed the Specialized compression plug in a Time Bandit fork that has a carbon steer tube. I use a Bontrager RXL stem that has a solid clamp around the steer tube, so there are no cutouts on the side or back as some stems have. I cut the steer tube to the maximum height just below the top of the stem that allows the regular top cap to clear it when assembled. I’m larger than most. My position places more weight on the aerobars than most. At four years of use there is no indication of undue stress on the steer tube.
Just cut the steerer so it’s a few mm below the top of the stem. A standard topcap/compression plug should work fine. Note that this gives you zero future adjustability. I prefer to cut such that the steerer is 3mm above the stem, and place a 5mm spacer on top. That way I can always flip the two and add 5mm to the stack.
Carbon forks long carried the recommendation of a 5mm spacer above the stem to help reduce the risk of crushing the end of the steerer when tightening the stem. Maybe this isn’t required on newer bikes (varies between manufacturers) but I personally think it is good practice. Spacer below the stem is up to you.
You’ve got some good intel in here (once we cleared up that star/compression confusion). If there was EVER a “measure twice - cut once” situation this is it. There’s no shame in having a 5mm spacer above for added adjust-ability or even resale value. But if you’re in urgent need of stem slammage then get a new 5mm Cobb headset top cap when it comes out and get all they way down there.
Take it to the LBS. I had mine slammed all the way with only an 8mm headset cover and no spacers above the stem (i’m using the TriRig sigma).
It cost me $11 at the LBS… not worth the risk in my opinion to DIY, they do this kind of thing all the time… They used the Specialized compression plug BTW.
With the right clip-on system you don’t have to worry about leaving extra spacers on top for further adjustability. I have the Zipp Vuka Clip and if I want to increase stack in the future I can add up to 5cm in pad & extension risers. Slam the crap out of it!