profile crank bolt keeps falling out

Unicycles and Equipment
1

about a week ago, I was riding and noticed that the crank bolt on my left Profile crank arm was gone. so I bought another one from the bike store, and put it in. today I was riding, and it’s gone aGAIN. so I’m thinking that it’s probably stripped, which really sucks.
what can I do to make it work? I really really really don’t have enough money to buy a new crank arm. and actually…, it doesn’t screw into the crank arm, does it? it screws into the axle I think. I’m not completely sure, I’m not tremendously good at this. do you think it might fall out because I didn’t use Loc-Tite on it? I know Loc-Tite helps, but I don’t think that it would fall out that often if I don’t use it…
so anyway, this has gotten me pretty freaked out because I don’t really want to ride my trials uni if the crank arm might be falling off. so any replies would be much appreciated. thanks!

EDIT decided to use this thread to ask another question…about my pedals. I have Jim C. Odyssey pedals. on the left pedal, the pins won’t stay in. it’s like they’re stripped too…you screw them in with an allen wrench, and I tried tightening them yesterday but they kept turning and turning, and weren’t getting any tighter. but they were still in. so today while I was riding, the pins were sliding around, and one of them actually fell out so I lost that one. so my question basically is…wtf? and, how do I ix it?

2

The bolt threads into the steel axle. It doesn’t thread into the crank at all. I very much doubt that you’ve damaged the threads in the hub. The steel threads in the axle are very strong. The bolt would break before you would be able to strip the threads.

No Loctite is needed or recommended for that bolt. Anti-seize though is recommended. I grease up the threads with anti-seize then get that bolt as tight as I reasonably can with my hands using a regular allen key. It should stay tight. I’ve never had a bolt come undone like that and I’ve always anti-seized those threads.

If the threads are dry it can be difficult to get the bolt tight enough. The anti-seize will actually allow you to get the bolt tighter because there will be less friction on the threads as you tighten it up. Dry threads are bad for bolts that get torqued down really tight.

So smear anti-seize over the threads and any bits that have a metal to metal contact. Tighten the bolts to a reasonable tightness by hand. The bolts should stay tight.

Those flush mount bolts are expensive. They’re like $15 for a pair. Profile calls the flush mount crank bolts Bitchin’ Bolts. It’s best not to lose them.

3

yeah, I’ve figured that out the hard way…fortunately, since only one fell out last time, I do have one extra. so I guess I’ll try antiseize, and hope that works…thanks john!

4

Something to check. Do you have enough spacers on the hub to keep the bolt from bottoming out? If you don’t have enough spacers the crank will too far onto the axle and the axle will protrude out beyond the crank. The bolt will bottom out against the axle before getting snugged up properly against the crank.

Also if the axle is not centered in the hub then one side of the hub will have more axle showing than the other side. The long side will need more spacers. If the axle is more than a few millimeters off center then you should look into getting the axle pressed back in so it is centered.

If you tighten one side of the hub really tight while leaving the other side of the hub undone you can actually end up pulling the axle off center in the hub. Threaded bolts can generate a lot of pulling force. When tightening up the Profile cranks (or any of the BMX style splined cranks) you should thread the crank bolts on both sides till they’re lightly snug. Then tighten each side evenly. Don’t just tighten one side really really tight then move on over to the other side. Otherwise you can literally pull the axle out of the hub. Tighten one side a bit then flip over and tighten the other side a bit then flip over and tighten the other side a bit, etc. till both sides are tight.

5

I’ll check that too, thanks…it’s a big relief to know that the axle isn’t stripped, because that would have been VERy bad I think.

so, does anyone know anything about the second question? my pedals?

6

If the threds are striped than i would say that sucks. You could drill holes next to the ones that are there and tap them but this would be alot of work. If there not striped therd lock would keep the from coming louse

7

The pedal is probably stripped. The pedal body is aluminum and aluminum threads can get stripped a lot more easily than steel threads.

If you keep the grip pins tight they will be less likely to strip or otherwise destroy the threads. The grip pins should also be Loctited. Low strength Loctite threadlocker is strong enough for the pins. You just want to keep them from vibrating loose. Loose grip pins can damage the threads.

8

The pedals definitely have stripped threads; if the pins spin but don’t go anywhere that’s a tell-tale sign. If you’ve a machinist at your disposal (or a really well-stocked hardware store) take an existing pin and ask for some set screws that are slightly larger… re-tap those holes to the larger screws and you’re good to go.

If you’re not totally concerned about changing the pins again, you could just find slightly larger set screws and jam them in, although you might break the hex key in the process… dunno if this is a good idea, but it’s the easiest.

You could take unicyclepa’s advice and re-drill the pedals, but that would be quite a bit of work.

If you’re stuck trying to find new set screws PM me and I can take a look in my shop at school… we’re pretty well stocked!

9

I had/have the same problem with my Profiles.
I have the $16 bolts also. They are flush.

My bolts used to fall out a lot, or get loose even riding paved.
I think it is because I used anti-seaze.

I took flour, put it in the axle and screwed the bolt down several times. This allowed the anti-seaze something to stick to. I kept doing it until I had a dry and clean surface inside.

Next, I put lock-tight on the nut generously. If I screw the bolt down pretty tight and let it sit over night it will hold for quite awhile.

Eventually, it comes loose again - but slowly enough for me to notice and tighten it. Before, I would look down one moment and it would be there and gone the next - like you described.

10

I was just visited by the Profile bolt gnomes (cousins of the underpants gnomes) and I’m feeling a little burned. The bolt (on the left side) has been coming loose regularly, and I’ve been tightening it regularly, but obviously not enough… I’ve now a hole in the left side of my axle where once a bolt was.

So in all my three clicks of searching, this thread seemed to have the best advice: to use antiseize on the threads to achieve the “tightest tightening”. But there’s a nagging voice in the back of my head that says use Loctite… a $1.00 tube of blue goo is a cheaper fix than a new $10.00 bolt after it falls out again.

For those of us that are, well, thick-headed… can someone clarify why this statement is true? ('cause we all know Childs speaks only the truth)

Even though Drew’s a smart guy, I know he’s a bit of a ham :stuck_out_tongue: , and I have to question this method… does this fix make sense? Will it compromise the effect of the anti-sieze, and would it offer any “holding power”?

Thanks for your collective wisdom!

11

Related question: can you get replacement Profile bolts which have a more realistic allen key size? A good 6mm would be a lot better than the one that comes on there.

12

Just use some temporary Loc-tite for now. If the problem worsens later, get a new hub.

13

I was being serious.
I took the advice of using anti-sieze first.
That left the threads “oily” and the bolt still was able to unwind easily.
The unwinding comes from vibration that eventually works the bolt loose.

To get the anti-seaze OFF, soap and degreaser did not work well.
I used the flour to bind to the anti-sieze and that worked very well.

After the flour gets the anti-sieze out, I used soap and water to get the flour out.
Then, I applied lock-tight to the “clean surface” and it works well.

Hope that clarifies the method that I used.

As far as John Childs’ claims go . . . I can only say that I have gotten better results using Locktite than anti-sieze.

“Recommended use” or not, I only care about results.

14

wow, this thread is ooold…

15

Yes and no. As far as I know, the profile hub uses american threads (hence the Imperial spec. bolt) unless they are little punks and use a metric thread bolt with american keys. This would have to be custom made… Anyways, you can find bolts of that type in some catalogues. Check what the thread dia. and pitch is… I think it’s 5/16 NF, but I’m not sure (NF=national fine). Then check in either a well stocked hardware store or check MSC Industrial, Enco (use-enco.com) or mcmaster-carr for the correct fasteners. Regardless, so long as you can get more of those cone washers, the bolts should NOT be $16. I would guess around $4 a pop, max.

You’re not going to find 6mm bolt with an american thread on it. You could buy one oversize and machine it down to the correct bolt, but this is a waste of time.

The anti-seize is to keep the bolt from seizing, not to help retain it. It’s not going to keep your bolts from falling out. The other use of the anti-seize is to help you get the bolts tighter, because it means less turning force goes to overcoming friction.

Here’s a trick I use in my shop and on my hub for getting bolts tight: Find an allen key with only one purpose; to tighten these bolts. Chop it down such that there’s almost none fo the short end of the L left, just enough that it fully engages the allen bolt head. Now use it, and always remember to fully insert it. When you need it super tight, you have two choices: Put your wheel up against a wall, and stand ont he wrench. I do that, adding a few “stomps” to get it super tight. The other way is to use what’s known as a cheater bar. Take a piece of pipe (1/2" is good) and put it on the allen key. Now you have a much better lever to torque it down with. Please, don’t combine these two methods, as it will easily strip the bolt (or hub, however more likely the bolt, since the hub is hardened chromoly and the bolt’s just mild steel).

I get the feeling the reason profile uses bolts with such small heads is they don’t want dumbass bike mechanics stripping stuff, however if u look at the regular bolts they are gigantic hex heads. BTW, I make no guarantee that profile will be willing to warranty a stripped axle if you use one of the methods I described. Many a fools have broken vises using cheater bars, and stripping a 5/6" NF thread with a 12" cheater bar is not unheard of.

Whew, long post, hope some of it helps.

16

The anti-seize should be enough to keep it tight. I suppose that there may be enough variation in some bolts being undersized and some axles being threaded oversized that some combinations of parts have more chance of working loose on their own. I’ve just personally never had a problem with that bolt getting loose.

I’d go with the anti-seize first and see if cranking down with the lubricated threads will keep it tight. If not then you’ll have to go through what Drew did to remove the grease/anti-seize from the bolt and hub then try the Loctite.

The important bit is to lubricate the threads with something before cranking that bolt really tight. Otherwise you risk damaging the threads. Anti-seize is a good lubricant for threads. Loctite when wet will act as a lubricant so the threads will be lubricated when you tighten it up. Just use enough Loctite to get effective lubrication. The problem with the Loctite is that once it dries it is no longer a good lubricant. So you’ll need to reapply when you retighten.

17

One last thing: If enough people need them, I might be able to make a small run of 25-50 of those little cone washers for around $1-2 each. Don’t quote me on that, though, since I still don’t know if that material is aluminum or stainless steel. If it’s stainless, the cost of those stupid little bolt combos is justified, both in material and cutter costs for machining the little bastards.

18

I’m pretty sure that the bolts are steel.

I did not ride for several weeks (while replacing my frame).

After that, I tried to removed the nut, but it was difficult.
I found that the bolt had actually rusted in place despite the Locktite?!

Had I left it alone, I am sure the bolt wouldn’t have gotten loose again.
I remove my cranks regularly to “rotate the tire.”

19

From the feel and weight, I think the bolts are steel but the washer thingies are aluminum.

20

Ok, thanks, that’s what I was thinking, aswell. I’ve always thought the washers were al. and the bolts to be mild steel.

Drew, I think the bolt could be reacting with the axle material. I forget what this is known for, but this is exactly why we use anti-seize. I doubt it was rust, being as it’s awfully hard for water to get into the threads, espexcially with as much pressure as they are under.