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Lengthening A Steerer Tube

Old 09-16-19, 12:23 PM
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hrdknox1
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Lengthening A Steerer Tube

I goofed and cut my 1 1/8" carbon steerer tube too short. I purchased a cheap fork ($48) off eBay to use as a length of steerer tube. I cut off 6 inches of my steerer tube and replaced it with the desired length of steerer tube cut from the eBay fork. To do this I bought a 1" wood dowel and cut a 4" length. I sanded the length of wood dowel until it fit snug inside the steerer tube ( the tube diameter is slightly smaller than 1 inch). I inserted one end of the wood dowel into the remaining tube and the other end into the cut length of tube and bonded it with epoxy. I now had the desired length of steerer tube, and one I could count on not to fail.

Last edited by hrdknox1; 09-20-19 at 02:26 PM.
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Old 09-16-19, 12:35 PM
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There are probably a lot of people who wood not ride your dowel steer tube. Do you really think its safety is oak-kay?
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Old 09-16-19, 12:46 PM
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Originally Posted by hrdknox1 View Post
and one I could count on not to fail.
I'm not so sure about that. Seems sketchy. Good thinking though.

Originally Posted by ljsense View Post
There are probably a lot of people who wood not ride your dowel steer tube. Do you really think its safety is oak-kay?
That's a pun right?

Last edited by Jicafold; 09-16-19 at 01:01 PM.
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Old 09-16-19, 01:00 PM
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Originally Posted by hrdknox1 View Post
I goofed and cut my 1 1/8" carbon steerer tube too short. I purchased a cheap fork ($48) off eBay to use as a length of steerer tube. I cut off 6 inches of my steerer tube and replaced it with the desired length of steerer tube cut from the eBay fork. To do this I bought a 1" wood dowel and cut a 4" length. I sanded the length of wood dowel until it fit snug inside the steerer tube ( the tube diameter is slightly smaller than 1 inch). I inserted one end of the wood dowel into the remaining tube and the other end into the cut length of tube and bonded it with epoxy. I now had the desired length of steerer tube, and one I could count on not to fail.
love your innovation, that epoxy is strong as mate

I often wondered if you could remove a steerer tube and insert another one, anyone??
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Old 09-16-19, 01:12 PM
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...kind of wondering about the lateral force absorption on a CF steering tube with intact fibrous carbon vs the lateral forces on an epoxied wood dowel. Certainly bicycle wheel rims were made from wood back in ancient times. Still, I think I would be uneasy riding along on such a repair. Not that I would ride this at all.
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Old 09-16-19, 01:22 PM
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Nope.
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Old 09-16-19, 01:38 PM
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not a good idea.... epoxy is not magic, Critical area of bike with bad results if there is a failure. Do only if you have good health insurance and deal well with pain
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Old 09-16-19, 01:55 PM
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Depending on the wood choice, the 1" wood dowel is likely stronger than the thin carbon fiber tube. More resilient to crushing?

Of course considering bonding, and a few other factors.

You could, of course, also sand out a groove around the joint, and bond in some carbon fiber.
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Old 09-16-19, 02:06 PM
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What type of wood? Kiln dried or aged? Do you have the published Ult. strength value for that wood? Someone above said it's probably stronger than the carbon fibre but I am skeptical.

The other problem, aside from strength, is alignment. Did you sand the dowel on a lathe? Because otherwise I fear it would put your bearings out of alignment.

I used to ride an MTB with a fork that had previously had the steerer tube cut too short, and I used a Profile threaded-to-threadless adaptor as an extension, using a piece of steerer tube cut from another old bike's fork as a 22.2-25.4mm shim. It worked fine for years under pretty hard use, but this wouldn't work with a carbon steerer, I am sure (can't use an expander or quill stem in carbon).
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Old 09-16-19, 02:14 PM
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Measure twice, cut once!

Someone needs to say it.

Sorry it doesn't help your current situation. A new fork would likely be in order. Alternatively, if you're exceptionally tall, the fork might have worked for a smaller frame, maybe helping you recoup some outlay for the fork.

Replace the fork for your safety.
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Old 09-16-19, 02:35 PM
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I'd say you made one big mistake: buying a new fork.

You could have just used the part you cut off and spliced that into the middle.

Or left the dowel exposed a bit to make up for the cut. You were probably only off by an eighth inch or so. Wood needs to breathe.

Next time for sure just buy some plywood and sand that into a dowel; it'll be stronger in all directions.
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Old 09-16-19, 02:42 PM
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Originally Posted by ljsense View Post
I'd say you made one big mistake: buying a new fork.

You could have just used the part you cut off and spliced that into the middle.

Or left the dowel exposed a bit to make up for the cut. You were probably only off by an eighth inch or so. Wood needs to breathe.

Next time for sure just buy some plywood and sand that into a dowel; it'll be stronger in all directions.
Pretty sure this is tongue in cheek, but as many people think whatever posted is real..... but making a round out of plywood will not be stronger than a dowell
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Old 09-16-19, 03:06 PM
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Originally Posted by squirtdad View Post
Pretty sure this is tongue in cheek, but as many people think whatever posted is real..... but making a round out of plywood will not be stronger than a dowell
True, but to be fair, it all depends on how you lay it up. There is a lot of knee-jerk reactions against plywood that go back ages -- Frank Lloyd Wright was no stranger to these attitudes. But obviously you're going to want to sand only along the bias, steam it until you can bend the plies into a radial spiral, use marine grade mahogany plywood, and layer in kevlar between the plies as you build your column.
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Old 09-16-19, 03:14 PM
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Originally Posted by ljsense View Post
True, but to be fair, it all depends on how you lay it up. There is a lot of knee-jerk reactions against plywood that go back ages -- Frank Lloyd Wright was no stranger to these attitudes. But obviously you're going to want to sand only along the bias, steam it until you can bend the plies into a radial spiral, use marine grade mahogany plywood, and layer in kevlar between the plies as you build your column.


Obviously
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Old 09-16-19, 03:46 PM
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Since you bought a cheap fork, one might assume you cut a cheap fork too short; however, I suspect your short fork was not cheap. Either way, I would not ride it with the repair. We all make mistakes, so why not just fork over for a new fork that won't fail for many thousands of miles.
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Old 09-16-19, 04:12 PM
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here is example of what would happen if this failed

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Old 09-16-19, 05:02 PM
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That video notwithstanding, I think this is probably ok.

For normal cruising, the weight of the bottom of the head tube will rest on the fork crown race through the headset bearing. Higher up, the joined steerer tube will be prevented from moving around a lot by the stem, preloaded against the upper headset bearing by the stem cap bolt and clamped in place by the stem bolts.

Now if the epoxy fails (seems unlikely) so the dowel can release from either end of the cut steerer tube, then yes the bars would be able to pull up and out. But if OP is a strong enough sprinter to be able to pull that epoxy apart, other people would be paying for his bikes and he wouldn't have to glue them together like this.

See also the Raleigh Technium, which was also epoxied together (though not with wood).

A better solution however might have been a threaded/threadless stem adapter. Saw down the too-short steerer some more, pop the adapter inside, tighten it up, and put a stem on it. Sheldon Brown demonstrated that the ID of a threadless steerer tube is the same as ID of a threaded fork, by adding a 2nd bonus handlebar to a bike using a quill stem inside the threadless steerer.


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Old 09-16-19, 05:08 PM
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Old 09-16-19, 05:09 PM
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also it looks like in that video the failed steerer tube sheared off right at the top of the headset. OP said he cut 6 inches off, so presumably his join is deep inside the headtube.
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Old 09-16-19, 05:53 PM
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1) Wood expands and contracts with humidity, which, I'm guessing will ultimately cause a failure. 2) Despite how careful you were, I doubt that the 2 ends of the steerer tube are concentric. This will lead to bearing problems. 3) Yes indeed, I'd be worried about the safety of the thing.
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Old 09-16-19, 05:58 PM
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You are playing with fire.
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Old 09-16-19, 06:00 PM
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One can purchase carbon fiber tubes on E-Bay, although often thin walled.

There are a few carbon fiber forks with 1" steer tubes that might also work as an insert, or perhaps carbon fiber seatposts.

One can also make one's own custom tubes by wrapping the carbon fiber (or using sleeves) around a dowel or rod, epoxying, compressing, and curing.
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Old 09-16-19, 06:02 PM
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Originally Posted by hrdknox1 View Post
I goofed and cut my 1 1/8" carbon steerer tube too short. I purchased a cheap fork ($48) off eBay to use as a length of steerer tube. I cut off 6 inches of my steerer tube and replaced it with the desired length of steerer tube cut from the eBay fork. To do this I bought a 1" wood dowel and cut a 4" length. I sanded the length of wood dowel until it fit snug inside the steerer tube ( the tube diameter is slightly smaller than 1 inch). I inserted one end of the wood dowel into the remaining tube and the other end into the cut length of tube and bonded it with epoxy. I now had the desired length of steerer tube, and one I could count on not to fail.
Hope you are joking. Remove that fork, cut it in half, and throw it in the trash.
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Old 09-16-19, 06:19 PM
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What would the best way to lengthen a carbon steerer, I wonder? I was going to keep playing along, but whatever -- it brings up a pretty good point: it would be useful to be able to make a steer tube longer.

I was just shopping for carbon 1" forks for a 90s vintage build, and there sure are a lot of them with short steer tubes around.

I'd think the only decent way to do it is with a fork jig and full removal of the old steerer, but it's probably no easy thing, especially if you're dealing with full carbon.
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Old 09-16-19, 06:32 PM
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Originally Posted by ljsense View Post
What would the best way to lengthen a carbon steerer, I wonder?
I've been reluctant to use clamp on tube extenders.

However, within reason, one might use an upward angled MTB stem.

As mentioned in Post 22, I'd probably go with an insert similar to the OP, but design a fairly thick walled carbon fiber insert. Of course, you get something fairly small with the 1" forks.

Move the splice to somewhere mid-head tube. That makes it harder to inspect, but I believe that it minimizes sheer forces.

I'm not sure of tubing source. Carbon seat posts, carbon tubing, used forks, one size smaller, or make a custom carbon tube for the splice. Or, perhaps a combination of methods, for example sourcing a thin wall CF tube, and either building it up on the inside or the outside.

Once spliced, grind down the but joint, and build that up too.

The discussion about plywood above brings up a good point. Fibers running inline with the steer tube are good. Fibers running across the tube help maintain the form, but otherwise don't add strength. So, use a judicious mix of longitudinal fibers for strength, and cross fibers for structure.
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