Shortening an alloy steerer

carl_p

I want to trim my alloy steerer by about 20mm if not a bit more. This means that the star fangled nut will also need to be hammered down further into the steerer tube. Can I do this with a setting tool or will I need to whack it right down with some other implement and then insert a new nut after the tube has been cut? Basically can the setting tool be used to adjust the depth of existing nuts or are they for new nuts only. Don't want to make any expensive mistakes. Thanks.

thistle_

The setting tool should work fine, the splines on the star fangled nut allow it to be pushed downwards but not pulled out.

If you've got a setting tool then you can use that. If not you can insert an old bolt into the nut and use a hammer to knock it down.

arthur_scrimshaw

The 'tricky' bit with a SFN is getting it started square in the steerer in the first place. As it's already in the steerer you can just tap it 20mm further down and reuse it after you've cut the steerer.

carl_p

Thanks all. I could get away without using a setting tool then. Might get a Park Tools one off Chainreaction though as relatively inexpensive - not a lot more than diesel to bike shop and a tenner to do it.

Barbarossa

Another tip, use a Jubilee clip as a cutting guide to keep the cut square.

Monty Dog

Cutting alloy steer = pipe cutter

Jon_1976

I used the method someone mentioned on here a while ago. Mark where the tube needs to be cut, put the stem and a 'sacrificial' spacer on the tube. Put the spacer on the cut mark, push the stem against the spacer and tighten it. Use the spacer as a saw guide.

Tube needs a clearance gap between the top of the stem (or spacer above stem) to stop the top cap bottoming out.

I also used the method of putting a bolt in the star and tapping it down with a rubber mallet. As mentioned, keeping it square is important. The proper tool would probably make that easier. I noticed mine had gone of out square a tab and the bolt wasn't parallel with the tube. Just gave the bolt a few taps on the side and it squared it easily.

patrickf

As a DIY bodge, to set the SFN why not sacrifice an old bolt and top cap? Would the top cap not ensure that you keep it straight?

bobones

Did this the other day. Fit stem in the desired position and mark the steerer tube at the top of the stem. The cut line should be 4mm below this mark. Insert a suitably narrow screwdriver with a sturdy handle into the SFN and tap on the screwdriver handle until the SFN is below the cut line. Cut the steerer tube with a hacksaw and file down burrs. Use a something as a guide for cutting, e.g. mitre box, light bracket etc. Tap down SFN to final position if required and reassemble. Pretty straightforward and no special tools required.