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Cutting my steer tube, two questions:

Road Cycling “It is by riding a bicycle that you learn the contours of a country best, since you have to sweat up the hills and coast down them. Thus you remember them as they actually are, while in a motor car only a high hill impresses you, and you have no such accurate remembrance of country you have driven through as you gain by riding a bicycle.” -- Ernest Hemingway

Cutting my steer tube, two questions:

Old 10-10-11, 02:51 PM
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Cpt.America
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Cutting my steer tube, two questions:

1) what do you guys cut it with? A normal ol hacksaw?
2) is it a good idea to leave one small spacer above the stem?

thanks...!

-cPt.
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Old 10-10-11, 02:53 PM
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A hacksaw works perfectly and yes, a single 5mm spacer above the stem is a really good idea to reduce stress on the top of the steerer where it is most likely to crack.
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Old 10-10-11, 02:55 PM
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Measure twice - Cut once. And buy a guide so you don't mess it up. And imo no.
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Old 10-10-11, 03:06 PM
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You don't really need a guide. Just cut 2-3mm above your mark. You'll more than likely cut at a slight angle and end up that 2-3mm off your mark on one side. Then you can file the high side down to perfection. It's almost impossible to screw it up, but if you think you're capable of botching the job that badly then it might be in your best interest to buy a cutting guide. I don't know how much these cost and I didn't want to make a special trip to buy one.

Again, it couldn't hurt to throw a 5mm spacer above the stem. Just FYI, LOOK recommends leaving the steerer a few mm longer than the stem and using a 5mm spacer on top. It's right in their user manual and they claim it prevents the steerer from being susceptible to failures at the top of the steerer. If anyone knows how to make carbon fiber forks it's LOOK. I'd take their word for it. They even supply a special tapered 5mm spacer with their bikes just for this.
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Old 10-10-11, 03:12 PM
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You might want a small file to tidy up the edges as well. Cutting guide is good because it prevents things going wrong, and you can get carbon specific hacksaw blades. The smaller the teeth the better. And try not to breathe in the dust, it's quite bad for you apparently.
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Old 10-10-11, 03:14 PM
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And cut higher than you initially need to. There's no harm in leaving spacers above the stem, it gives you the ability to change your position without buying a new fork.
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Old 10-10-11, 03:24 PM
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Thanks guys, i appreciate it. I am not worried about botching something like this up, as I am very mechanically inclined and do cutting of these sorts all the time. A guide certainly isn't needed, and any slight angle you put into the tube on your cut can be flattened out with either a file, or some sand paper / sanding block. I think I will follow the recommendation of leaving a single 5mm spacer on top just in case. It just looks a little funny with 5 of them at the moment

Thanks again!
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Old 10-10-11, 03:31 PM
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Make sure your bike is supposed to have a spacer on top. My Tarmac's manual clearly states NO spacers above the stem. So, check first.
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Old 10-10-11, 03:37 PM
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I made a jig to cut them on the bandsaw.

warning: CF sparks when cut with a bandsaw, so disconnect your dust collector, and wear a respirator when cutting CF in any way.
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Old 10-10-11, 03:43 PM
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Originally Posted by garciawork View Post
Make sure your bike is supposed to have a spacer on top. My Tarmac's manual clearly states NO spacers above the stem. So, check first.
Do you use a Specialised multi position stem? The offset top cap of that is supposed to sit flush with the stem for it to work, but I've used them with spacers and a regular top cap. What you don't want is a void behind the top pinch bolt of the stem. That will lead to irregular clamping and damage to the steerer tube more so than having both bolts fastening onto the steerer tube properly.
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Old 10-10-11, 03:44 PM
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The reason for the 5 mm spacer on top is so the clamping force of the stem is squarely on the steerer, not above it. To get the preload on the headset, their needs to be a gap between the end of the steerer, and the top cap. That can be accomplished by the top of the stem being slightly above the end of the steerer tube. ( bad). Or by using a small spacer on top of the stem. (good)

To the extent fork manufacturers say not to use spacers on top (such as C'dale, and apparently from the post above Specialized) is that they want the stem's clamping force to be on the portion of the steerer tube that's reinforced a bit by a sleeve glued into the steerer holding the star nut, not below it.

Thus you don't want to run a lot of spacers on the top in that situation. That does not mean its a bad idea to run a very small spacer to get the headset compression right.

And I'd bet the Tarmac instructions are not talking about a 2-5 mm spacer on top.
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Old 10-10-11, 03:45 PM
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Originally Posted by Grumpy McTrumpy View Post
I made a jig to cut them on the bandsaw.
I just use a spare spacer as a guide.
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Old 10-10-11, 04:27 PM
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Hacksaw for CF steer tubes and a pipe cutter for aluminum.
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Old 10-10-11, 07:02 PM
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A makeshift guide used by a mechanic who cut mine is two pieces of white electrical tape carefully wrapped around the tube above and below the cut mark with about a mm of space between each matched to the mark. He does perfect cuts this way.

Last edited by learnmedia; 10-10-11 at 07:17 PM.
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Old 10-10-11, 07:17 PM
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I saw a picture of a team mechanic cutting the tube while still on the bike using a hacksaw. Have any of you done it this way or do you take the fork off first?
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Old 10-10-11, 07:52 PM
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Originally Posted by Jaymadd View Post
I saw a picture of a team mechanic cutting the tube while still on the bike using a hacksaw. Have any of you done it this way or do you take the fork off first?
the way i do it.
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Old 10-10-11, 08:02 PM
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I used a hose clamp as a guide with a hacksaw and a high toothed blade (36?). Manufacturer recommended against a spacer on top (Felt after-market fork).
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Old 10-10-11, 08:18 PM
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I put the fork on a mandrel in the lathe and part off the excess.
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Old 10-10-11, 08:23 PM
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Originally Posted by Jaymadd View Post
I saw a picture of a team mechanic cutting the tube while still on the bike using a hacksaw. Have any of you done it this way or do you take the fork off first?
I did it this way on my Look 595 and it turned out perfect.
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Old 10-10-11, 08:35 PM
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Just to be clear, this is a direct quote from Specialized's carbon for install (which I was referring to) "WARNING! Do not permanently place stem spacers above the stem (Fig. 3). Placing spacers above the stem defeats the purpose of the expander plug’s ability to support the steerer tube and stem." So, no, they don't like it for some reason.
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Old 10-10-11, 09:32 PM
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Originally Posted by merlinextraligh View Post
I just use a spare spacer as a guide.
+1 Since the top cap isn't resting directly on the steer tube anyway, you'd have to really screw up the cut to get an angle that could cause problems.

As for the top cap, yes if it's a carbon steer tube and not a Specialized shimmed stem. No if it's a Specialized shimmed stem. Your choice if it's an alloy steerer and no shim.
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Old 10-10-11, 11:15 PM
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As other's have stated it's actual hard to mess up because after the cut you can still fine-tune it with the exception of actually cutting it too short of course.

I was paranoid about it all when I did it my first time too - a couple of weeks ago.

I used painter's tape as a guide of where to cut.

Use 32 or higher TPI blade. If your cut doesn't end up square and 90 degrees, file or sand by hand or carefully dremel sand paper bit (I don't know what it's actually called).

I'm sure you also already know this, but the 3mm gap between the top of the steerer tube and the top of the stem is critical. I had headset play no matter how much I tightened my top cap and realized that my gap was only about 1.5mm which gave no room to tighten up the headset.
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Old 10-11-11, 07:22 AM
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Originally Posted by garciawork View Post
Just to be clear, this is a direct quote from Specialized's carbon for install (which I was referring to) "WARNING! Do not permanently place stem spacers above the stem (Fig. 3). Placing spacers above the stem defeats the purpose of the expander plug’s ability to support the steerer tube and stem." So, no, they don't like it for some reason.
They don't like it for the reason stated. They want the stem to clamp where the expander plug is inside the steerer tube.

However, what they're addressing is having a significant amount of spacer above the stem, i.e. enough to move the stem below the expander plug.

If you look at their illustration, they're showing 30mm of spacers above the stem as being wrong.

http://cdn.specialized.com/OA_MEDIA/...n_Guide_r2.pdf

A small spacer on top is going to get the stem to clamp right on where the expander plug is inside the stem, not below it. So a 2-5mm spacer on top of the stem is consistent with what Specialized is trying to achieve.
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Old 10-11-11, 07:36 AM
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Just to add a tiny bit of relevant information: Easton also specifies a 5mm spacer on top.

I figured if one was good, three should be great.

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