lineinthewater

My steerer tube (carbon) was cut so that it is exactly flush with the top of the stem. Unfortunately, I rode about 8 miles on it before noticing the play in the headset/fork. Doubt it messed anything up (correct me if I'm wrong).

So, I can either have another 2-3mm shaved off the steerer tube (2-3mm is proper gap, correct?), or put another spacer under the stem (or change the existing spacer to a slightly larger one).

Two questions:

1. Are there any pitfalls to trying to cut such a small slice from a carbon steerer tube? I'm guessing this is a complete non-issue, but wanted to make 100% sure. For such a small cut, is a hacksaw OK, or would a specialized tool be better?

2. What are standard headset spacer heights? Do they come in either 2, 3, 7, or 8 mm?

LesterOfPuppets

Some carbon steerer fork manus recommend a spacer above the stem, so I'd just do that. I've seen 2mm, 2.5mm and 3mm spacers. Mostly 5mm increments above that, but I imagine others might be around.

lineinthewater

Two issues with this:

1. I know many manufacturers and mechanics suggest using a spacer above the stem, to better distribute the clamping force of the stem across it's entire length (on the steerer tube). I have a Cannondale, and they specifically say not to put spacers above the stem. I found the reason is that the top cap actually has a plug that fits within the steerer tube (to counter the clamping force of the stem). Adding top spacers reduces it's effectiveness.

2. Assuming I didn't have a Cannondale, I believe the steerer tube needs to actually extend well above the stem to use a top spacer. In other words, it can't just float on top.

HillRider

Don't cut the steerer because having it supported completely within the stem is desirable for carbon. The easiest thing to do is add a 2 or 5 mm spacer ABOVE the stem to provide the adjustment gap. Common spacers are 2, 5, 10, 20, 30 and 40 mm.

HillRider

I see no problem with a spacer above the stem even if the stem is now flush. When the OP gets the proper headset preload, I expect a thin edge of steerer will indeed be above the stem and will center the top spacer.

Another approach is to remove about 2 mm of spacers from below the stem and add 5 mm above it. That will assure the stem projects above the steerer a small amount.

lineinthewater

This is the headset I have. See the top cap? That lower portion of the cap extends inside the steerer tube. Like I said, Cannondale explicitly says not to put on top spacers.

https://www.ebay.com/itm/CANNONDALE-C...-/120997047347

LesterOfPuppets

Good points. If there is absolutely no lip of steerer above the stem theres a good chance you'll nevere preload the bearings. And yep, some plugs also serve to brace against the stem's compression, so as much plug in the stem as possible is a good thing.

lineinthewater

I want to stick with Cannondale's recommendation (correction, instructions). Given this, do you think the easiest/safest thing to do is add a 2mm spacer (on top of my existing 5mm spacer) below the stem? Is that a good gap? I'm guessing when the headset is preloaded, as Hillrider points out, it will close the gap to 1-1.5mm?

Crankycrank

Maybe I'm missing something here but since they recommend that the steerer plug be located at a certain place in relation to the stem why not just move the plug and add whatever size spacers needed on top of the stem. There is also the option of taking the extra 2-3mm off the steerer with a sanding wheel preferably the motorized on a stand type for accuracy as opposed to a hand held drill. (protect your lungs and wear a mask) I always prefer to have a little extra stem on top for two reasons. First you'll have more adjustment available if you decide to raise your stem at some point and second you give just a little more clamping area for the stem. That 3mm that sits halfway between one of the clamps creates a higher stress spot. Probably not a problem for most setups but why do it that way when a spacer on top takes away the risk.

HillRider

Despite Cannondale's recommendation for no spacers above the stem i can't believe a 2 mm spacer will compromise the steerer's strength. I'm sure they don't want 10 or 20 mm there but 2 can't be an issue.

well biked

+1, and if you want to absolutely stick to their instructions then just put a small spacer under the stem to create a gap at the top so the headset preload adjustment can be made properly. No need to cut the steerer.

ksisler

Recommend looking for them! FWIW, ebay has a million ads of them for sale. Replace X and search on: threadless +headset +spacer +Xmm .... although you should see that there are ads for small sets of them in a range of thicknesses for just a few dollars more than buying just one. Great for when not fully sure which is perfect for your situation.

fietsbob

Since OP did not announce its a Cannondale.. some projecting seems to have occurred..
Over or under the stem is the choice..
not only are there machined Carbon tube spacers, to keep to the carbon fiber thing..
typically, 2.5, 5, 10 mm, ... 20, 40..
but there are also thin metal shim steering tube spacers that are thinner than 1 mm..

MisterK

With the right wheel (not sure what grade wheel for carbon) you could use a wide roller or 4 wheel tubing cutter and it should be able to get a straight cut even if its just a minimal length to cut. I for one have never used it for steering tubes but I've cut all sorts of other pipe (apprentice plumber)
I find a lot of tools work well for plumbing and cycling. A strap wrench will also tighten and remove an external bb aswell as the actual tool does and won't slip or marr edges

HillRider

Right, we didn't find out it was a Cannnondale until the third posting.

fietsbob

OK that is different [not in a C'dale shop] metal steerers have different requirements ..

stem Apparently needs 100% contact on CF steerer forks.. so under the stem your thin spacer must go..

FMB42

The way I see it the "recommended 2-3mm gap" is still going to allow the top cap to support the tube under any stem clamping forces regardless of whether or not you use a 2-3mm spacer on top.

My guess it that C'dale doesn't want you to use spacers above the stem that thicker than say 10 or more millimeters (which could/would negate the top cap's support). I could be wrong tho...

Otherwise, you could simply place a 2-3mm spacer underneath the stem (as others have mentioned) and be done with it.

Al1943

You can easily trim 2 - 3 mm off the top of the steer tube using a flat tile. I would probably use a coarse file first and finish with a finer file.

fietsbob

Carbon fiber dust is not good to inhale.. it stays in your lungs..

HillRider

No, it doesn't. The MSDS for Carbon Fiber calls it a temporary upper respiratory itrritant. Breathing the dust isn't a particularly great idea but it's not long term harmful unless you do it daily.

Al1943

In the words of Bill Clinton, I didn't inhale.

fietsbob

still I'd wear a dust mask when working with the stuff.. maybe a wet one to capture the really fine stuff..

HillRider

Sure, no argument with that but, my point was that carbon dust isn't in the same category as asbestos.

Andrew R Stewart 

Since the top cap is not needed while riding the bike, assuming a properly tightened stem, here's an option not mentioned. You could install a spacer above the stem, well centered on the steerer, install the top cap which now will transfer it's preloading to the stem, adjust the headset, tighten the stem, remove the top cap and spacer and go ride. (Or put the top cap back on so no one says your set up is wrong). Andy.

Greyryder

Keep it simple. Just put a 2mm spacer on top of the stem.