Disclaimer: This is major elective surgery on your bike. You should also consider either marking and taking your fork to the shop to let them cut it down or, if you’re uncomfortable even stripping your fork, take the whole bike. To proceed, you will need to know how to take apart your front end and put it back together successfully. EVERY time. Also, consider that it’s very easy to remove material from your fork tube. Putting it back on if you screw this up is impossible.
Tools: 4 & 5 mm hex wrenches, maybe a 6 if things get a little interesting. Some masking tape, and a hacksaw.
A couple of my bikes have a stack of spacers above the stem. I am a rare breed of cyclist who is more comfortable with a decent drop from the saddle to the handlebar so I’ve never kept the setup of a delivered bike.
My gravel bike still has the stack above the stem because I wanted to spend some real time on it to make sure I liked the handlebar position. I suppose I’ll probably cut that one down this next week while I’ve got some time off. I love the position I’m in on the gravel bike and if I ever wanted to raise the bar in the future, I can do that with a steeper stem. I’ve also got a big stack on my tandem, but I leave that in case I ever decide to sell the bike to get something a little racier (this is likely once the kids are out of college). My Specialized Venge was the big one. I had a stack above the stem because, again, I wanted to make sure I liked the setup the way it was. Again, it’s real easy to remove fork material. It’s impossible to put it back on. I wanted to be absolutely certain I liked the new setup.
Once I’d ridden the bike for a year in that configuration, it was time to fix that stack of spacers above the stem… I took the front end apart and took it to the shop to have them perform the surgery. Unfortunately, they needed to be one millimeter more aggressive with their cut and after I discovered the problem (it took a while, they were so close), I took the fork apart and took the fork to the shop where I cut the rest off myself. I was a bit chicken, I wanted to do it under the supervision of someone experienced. Now, for those with carbon forks, many mechanics will prefer enough fork to poke above the stem that one needs a 5 mm spacer above the stem. This keeps the stem from clamping to the end of the fork post, putting pressure on a weak point in the carbon fiber. I have no opinion on whether or not this is necessary, I’ve seen it done with and without a spacer but I choose not to risk it:
To perform this surgery is pretty straight forward. First, take off the front wheel. Then, remove the brake caliper from the fork. The bolt end is in the little hole at the back of the fork. Once the brake is off, remove the stem and spacers, leaving all of the cables attached. Set that off to the side without allowing the cables or housings to kink. Kinky cables are bad. Take the steering assembly apart, setting the pieces, washers and bearings, aside in order so you can put everything back together exactly as you took it apart. Finally, remove the stem cap plug from inside the fork post. With a carbon fiber post, this is simple. Screw your top cap bolt into the plug a few turns and give it a tap with a hammer which will release the plug (it’s friction fit with cf forks).
With your fork free, it’s time for the tricky work to take place. With carbon fiber, it cannot be understated how important it is to protect the fibers. Aluminum fork ends are less delicate. So, we know how much fork post we need to remove (leave two millimeters above the stem to allow for that spacer, or you’ll have to cut it two millimeters below the stem [which will allow for the cap plug]). Basically, take your spacer thickness and subtract two millimeters. Incidentally, if you’re dealing with a star nut, there are videos out there to show how to remove or lower them so you can cut the stem – it’s quite simple. So, now we’re going to use that masking tape to mark where we want to cut. This isn’t just a guide, so this step is important – it will help keep the fiber ends from fraying. Then, we take that hacksaw with a new(ish) blade and SLLLLLOOOOOOOOWWWWWWLLLLYYYYY start working our way around the fork tube creating a groove all the way around the tube before we really get into the sawing motion. Take your time. Once you’ve cut the fork tube, sand the edges with some sandpaper to clean up and rough edges – be careful of the carbon fibers here, again. You don’t want to be too aggressive, just enough to ease the edges.
Now, simply put everything back together paying close attention to the torque specifications printed on the parts and you’re done.
Now, as a side note, whenever you lower your stem by changing the spacers around, you should check your cable housings to make sure you’re not binding up anywhere. The front brake cable will be the first to give you problems with too much slack in the system. I had to trim the front brake housing on the Venge when I lowered the bar on it. The rear brake and derailleur housings were still OK.