Help - Crank Bolt Problem!

Hi Guys.

I built my first wheel today with help from a wheel builder. Everything went well until I put KH crank arms on the HK Spirit hub. I tightened the right side screw and the crank arm didn’t seem to go all the way down to the spacer so I decide to take the screw out so I could tap the crank with a rubber mallet. The problem is the screw won’t unscrew! :astonished: It went about one rotation and got too tight. Now it won’t budge. I’ve had a couple of guys try to get it off with a long allen wrench but they couldn’t. I guess I have two options: ride it as is and wait until I want to change cranks to see if I end up breaking the hub and/or bolt or try to get it off now with a longer lever and perhaps break the hub. Is it a problem that the crank isn’t quite touching the spacer?

Any advice? I’m so sad right now.

Oh I forgot to add there is no brake rotor on the crank arms.

This is what it looks like before I messed up.

First of all, very cool wheel Vertigo! Congrats on that and enjoy riding it when you get this straightened out, and I’m sure you will.

It’s tough to tele-diagnose something like this without being able to turn it and feel it in person. With brand new parts, sometimes there’s a sharp edge left on the threads or a little scrap of metal swarf left in the hole that’s jamming things. Your mention of a long Allen wrench is a bit of a red flag though. I’ve never been able to get anywhere close to the 25 - 30 ft-lbs of torque those bolts take without a big ratchet handle with a hex bit in it. It makes me wonder if maybe you just aren’t yanking on it hard enough. Breaking off the bolt in the hole would be a serious drag, but it takes some major force and/or really bad technique to do that with such a large strong bolt.

It’s also possible that it’s jammed because it was been fitted dry. You could try feeding penetrating oil down the threads. If you’re able to turn the bolt back that one turn in the tightening direction, that might help to work the oil into the threads. Heating the hub with a torch could also help to break a stubborn thread, although that’s usually something you’d do with old stuff. I can’t say I’ve ever had to resort to that with newly fitted stuff.

Take your time and think it through. I’m betting that it’s nothing too serious. Good luck!

Hi LargeEddie,

Thanks for the response. Good to see you! Hope you’ve been busy riding.

I sprayed some lubricant and will see if that helps. It moves back and forth a little bit but not much. Perhaps I cross threaded it without realizing it or there was something on the threads before I started turning the bolt. I can’t imagine I could tighten it that much with just a long allen wrench. Three different guys tried to get it loose but gave up. I also goofed up by not putting any grease on it. :frowning: Perhaps an expensive mistake.

Oh, bummer. I had a problem with stuck bolts on my hub. I have a 2015 KH26 and I bent the disc rotor on a ride. When I went to remove the crank to change the rotor the bolt came out part way (with a TON of effort) and then wouldn’t budge. I had to take it to a bike shop and it took them a good twenty minutes to get the bolt out. The bolt was stripped and the hub had to be retapped. The original bolts that came on the uni were M14 bolts and they were replaced with and the hub retapped for M12 bolts. I have no idea if this relates at all to your problem but I thought I’d throw it out there. :slight_smile:

Also, if you take a seat out of a uni you can slip the bottom of the seat post over the allen wrench handle and use it for leverage. Kinda ghetto but totally handy.

Metal can cold weld itself when under high pressures particularly where the two interfacing materials are identical. In particular, stainless steel is notorious for cold welding itself which is why stainless steel nuts and bolts should always be of a different grade.

The most dramatic example I have experienced was the nut on the end of the rear axle of VW Kombi. Both materials were ordinary steel but the nut is huge. A friend had come to me asking if I could help him get one undone.

I said “no problem” and got out my 3/4 inch drive socket set. No movement. I put a four foot pipe on the bar. Still wouldn’t budge so I resorted to heat from the oxy-acetylene torch. Still nothing, so I drilled a row of holes in one face and drove a cold chisel to split the nut.

I put the socket and bar on and my friend went to hand me the four foot extension. I motioned that we wouldn’t need it after splitting the nut. Incredulously it still didn’t move. The split nut still required the four foot extension. It finally released with a bang.

Looking closely at the nut I could see a small section of thread that had folded back on itself. Clearly it had welded to the axle thread and folded back as it began to move.

Always lubricate threads that are under high pressure.

Thanks guys for the reply. It moves a bit so it’s not totally locked up. I’ll go ahead and ride it as is and later decide what to do.

Do bike shops retap hubs?

I’m going to Cannon Beach today and coming back Wednesday. If you have made no progress by then, bring it over and I’ll take a look. If we can’t remove it, the instrument makers in the machine shop at my lab are your best bet and they are better equipped to do it than anyone I know.

Thanks so much Harper. I’m going to ride it as is for a few days and see how it feels before I put more effort into the problem. I’ve gotten the bolt to turn a bit more but hesitate to push it farther for fear of breaking it and making it unrideable.

I just took it around the block for a test ride and was pleasently surprised how easy it is to ride. I feared it might be a bit squirrely at first but it wasn’t at all. It’s so light!

I probably missed it but how long is the Allen wrench you are using?

I’d feel comfortable using a regular 8 or 10 inch ratchet with a bit on it and exerting as much effort as possible without breaking a bolt as beefy as a crank bolt.

I got it out with an old seat post that’s about 8 - 10 inches long. Just put it over a long allen wrench and worked at it for about 20 minutes.

I took the other bolt out, greased it and gently tried to screw it into the hub on the side that is giving me problems. It only goes down about a quarter of the way. I apparently the threads in the hub are too damaged now :frowning:

I remember that from the beginning the bolt didn’t go on very easily. I had to put some force on the allen wrench but I didn’t feel like I was forcing it too much. Perhaps the fact that it wasn’t going on easily was a sign that something was wrong and I shouldn’t have continued. Could the hub or bolt been defective from the beginning? Do these screws ever need any force to go on?

Yeah, gotta be a big difference from what you’re used to. I think you’ll have a lot of fun with it.

OK, well at least it’s out in one piece, so that’s something. It doesn’t seem altogether unlikely that someone in your area/community already has a thread tap to try to clean it up inside there. (Would that be M12x1? Pardon me if I don’t go take a bolt out of the KH hub on my 20" right now and measure it. :)) It looks like a tap would be $30-ish bucks in the event no one does, which is still cheaper than another hub. And then someone would.

Using a tap to “chase” the threads on new parts before assembly is never a terrible idea. Or at the very least, put a few drops of oil in the hole and run the screws in all the way without cranks on to make sure they go freely. I’m telling you this a bit late, I know.

I’d replace the bolt, but a little spot missing from the internal hub thread after it’s cleaned up isn’t a showstopper. They’re overkill for what it does and steel is pretty forgiving. Just so long as it can be torqued up to spec, it oughta be ok.

That bolt looks pretty messed up. I’d see if the bike shop can retap the threads for you, then get a new bolt and ride.

That is EXACTLY what the damage to my bolt looked like once it came out. Look at the head of the bolt- does it say M14 or M12? My bike shop removed both crank bolts, retapped the hub, and replaced the bolts for something like $20.

I just found my old post about the problem on the FB chat group. Here was Kris’ response:
Sorry to hear about the issue. I suspect the axle bolt hole threads were tapped slightly too short. Probably the assembler installed the axle bolts and slightly stripped the end of the long bolts. That would make them hard to extract. Because the bolts are softer material than the axle, I suspect some bolt material has bunged up the threads. Assuming you can get the bolts out this is simple to fix. Most good bikeshops will have a M12x1 cleaning tap; this just needs to be run through the axle bolt threads. The Spirit hubs come with extra long axle bolts. There is absolutely no need for the longer bolts except to install Rollo disks; the only reason I spec them on the larger wheel unis is that the manufacturer has to make large quantities. So…in sum - if you replace with shorter axle bolts and clean the threads out with the cleaning tap, it should all be good

Thank you MuniCo. Your seat post trick worked. I’ll have to check the other bolt and see if it’s shorter. It didn’t have the same problem. The damaged one says M12.

I’m glad you got it figured out and Kris acknowledged the problem. Perhaps UDC should be checking the bolts before they send them out. I spent a lot of time on the wheel so it would be a bummer to have to take it apart, especially since I don’t have the tools. I put it together during a class at a bike workshop.

Perhaps I should also see if my 2015 KH 26" has this problem. I haven’t tried to change those cranks yet. I’ve only had it a couple of months.

When I bought my 2nd-ever KH unicycle part, I experienced the exact same.
It’s because there isn’t enough threading inside / the supplied bolts are too long.

Were you able to fix it by tapping the hub?

I’ve been to two bike shops today and neither one had a tap that size. The second shop was one of the larger local bike shops. The guy at the second shop was skeptical that tapping it with the same size tap would be a permanent solution.

Whadda y’all think?:

That’s what I’d be getting.

I’m sure they have an M12-1 tap in the machine shop. We can measure the thread depths on each side, too, if you want.

Actually the problem happened twice with the same hub;
initially not super-bad, and so after the first time I debrided the inside and bolt with a brushes, all clean and looking still fine to use.
Then also the 2nd time the bolt went in without any sign of a problem…
until a certain point (much further on than the beginning, more like halfway), where it went so enormous stuck.

I don’t expect that either, but -if not too costly- not too bad to try (oppose sending material linea-recta to the trash - while you still can learn).
The broken thread seems in the middle, and then blocking any rotation.
If the tap would remove the bad section AND could extend the existing thread, you may be OK.
But before doing so, I suggest to contact your vendor about warranty.