I have never had to go through this with an alum steerer tube as all my used bikes have had adequate steerer tube to work with. However, my latest ride is requiring a new fork. Found the one I want and here is my question.
Before I cut this one down I want to experiment with some different stem heights indoors on the trainer. Obviously I don’t want to set the star nut at the full uncut length just yet. I figure I can spin indoors on the trainer w/o having the headset compressed with the star nut pressure and just use the stem on top of the spacers and my body weight with the stem bolts tightened down?
The trainer is probably fine for a ball park. But, there are quite a few folks who have trouble holding the same position while on the trainer as they would on the road. I don’t know if it is motivational or what, but that can be the case.
As an alternative, you could probably get one of the expandable type top caps that replace the expander bolt and try it with normal riding. You should be able to get a pretty good ballpark of where the fork needs to be cut just based on the measurements of your old bikes as well.
Not really. If your ride enough with your headset lose, even on the trainer, at some point the bearings are going to be destroyed. The bearings are designed to take the load vertically, when you have a lose headset and the steerer tube is slopping around putting a lot of horizontal load on the bearings.
So yeah, you could get the thing set up with out getting the headset compressed. With that being said, since he posed the question, his first instinct is obviously telling him that this isn’t the way to go. Kind of reminds me of when I get people who bring their bikes in who tried to removed their external bearing bb with a pair of vice grips…will it work, maybe…will it chew the bb to hell…yes. Thanks to these folks though, I have a job
Yea I won’t be on it for much more than 20 minutes or so. I need ~ 2cm more steerer tube, but just want to make sure it’s dead nuts right plus a little extra before I go cutting. And I have no idea why I didn’t think of a carbon expander plug…perhaps b/c my bikes all have alloy tubes and came with star nuts…or I’m a ‘stoopit’. Thanks for the idea! Headset and fork tasks are the last piece of my home wrenching knowledge base to add so here we go…thanks!
You’re mistaken - there is no need for the headset to be loose w/o a starnut. Simply push down hard on the stem to take all slop out of the headset, then tighten the stem. Check for play as normal. If there is no play, good. If there is, you need to loosen the stem more and push the system together more.
The starnut assembly makes it much easier to set up the headset, but is not essential to doing so.
PS - 20 minutes on trainer even with the headset completely loose is not going to trash the bearings.
Here is my exact scenario which I should have laid out before. I want to attempt to do this myself as the only LBS I trust requires 90 minutes each way and if I have to leave it I will be bikeless for a solid week or more:
I am swapping out exact forks: Wolf Classic CL for another. I have a home made hillbilly fork crown race setter my buddy is letting me use. Have watched him use it before and seems awfully simple so feel comfortable with this part(1 1/4" x 18" pvc). I’m going to take off my old crown race and seat it on the new Wolf and then get to work dialing in my spacers…I know the height within say 1.5cm so it won’t take long. Once I get that height confirmed I’m going to cut it so I have 5mm extra on top.
The expander plug seems like a nice way to go, but oddly enough have never used one as I just don’t like the idea of carbon steerer tubes. Might be unfounded, but oh well alum is what I like.
If you can set it up w/o any slack whatever you do is fine. The plug/nut are tools to help take up slack in the headset, but if you can get rid of that slack w/o them just ride it.
Another approach that will work if you have a ton of spacers handy: put many many spacers above the stem, install the star nut up near the end of the steerer tube, and use it to take out the slack. Then when you’re ready to cut the steerer, move the star nut down further into the steerer tube and cut above it.
Have you ever installed a star nut before? This isn’t a problem at all.
Put the star nut in. Ride the bike. If you need to cut more steerer, either drive the star nut in farther before you cut, or cut above it, then drive it in to the correct height and you’re good to go.
You’re making this way more difficult than it needs to be…
