I’ve got an older SS bike (which I use for commuting) with a square spindle for the crank arms. The left crank has a 10mm allen bolt holding it in, which is normal threaded (not counter-clockwise). I also notice that the larger opening is threaded, but I have nothing to put there. Right now, no matter how tight the allen bolt is, I can’t go more than a minute or two before it starts to loosen. I’m guessing I’m missing some sort of lock ring which would screw into the crank arm itself. Any advice? Is this what I am missing? What would I call such a piece? And better yet, where would I find one?
Your crank arm tapers are toast. There really is nothing you can do about it. Once you ride on a loose square-taper crank arm, there’s not remedy.
That really is the ONLY flaw in that design.
The outer threads are for (1) dustcaps (which I never put on mine) and (2) the crank arm extractor (which you don’t need on this one – it self-extracts).
+1 to what the other poster wrote. A couple of other possibilities if this were a new build,not sure in your situation - the bottom bracket axle is too short for the frame/crank and you are bottoming out the crank bolt because the crank contacts the frame before the bolt can get too tight or using the wrong square taper crank on the wrong square taper bottom bracket, almost the same situation.
Tighten it hard and then release/remove the bolt.
How does it look?
Does it come loose right away?
Is there a gap between the face the bolt pushes on and the end of the axle?
It could be that the bolt bottoms out on the axle before it touches the crank.
If not, try greasing the square taper to get more ‘squeeze’.
Also, try heating the crank before rapidly bolting it real tight.
Last resort is to start filing the tapered hole in the crank…
FSA Gossamer. Cheap, decent quality. Won’t win any weight weenie contests, but I’ve got 3 of them on various rigs, and they’re pretty solid.
Funny you should post this, I was looking for info on Gossamer vs Shimano earlier today and apparently the FSA’s were good enough for Cancellara to use in 2007:
Thank you ST collective. Within minutes I had answers.
While it’s not a high end bike (duh), it did come assembled, so I’m gonna presume the BB is correct for it. I took the crank arm off. It looked like perhaps it could go just a little further. So I took the BFH (big f. hammer) to it and pushed that crank arm on as tight as I could get it. Then put the bolt back in. I just went for a quick 1 mile ride of start/stop (so as much torque as I can put on the crank), and everything stayed tight.
And nope, I’m not worried about the weight weenie aspect. It’s a steel frame, and I could stand to lose more than a couple of grams myself before worrying about the bike. Plus, this is a SS that is for fun, not my race or even training bike.
Locktite on the bolt and check it every once in a while. If you hear a squeck it may be coming loose. Also a hex head bolt vs a allen bolt will allow you to tighten more.
The outside threading, I believe, is for a crank puller. If you now have it on tight, then ride a bit with it and retighten the crank bolts again after a few miles and after a few hundred.
Try removing the crank arm (using the self extracting bolt already installed) then clean everything really well with mineral turps or degreaser. Specifically all threads, inside and out.
Before you re-install, check crank arm clearances as another poster suggested.
Check that the BB itself hasn’t come loose also (unlikely but possible) Tighten the drive side snug, but the non drive side (that might be plastic) shouldn’t be reefed on.
Also check that the self extracting bolt isn’t too long and bottoming out in the hole. (screw it in, without the crank arm to see if it keeps going in any further) You could take some cut ali can and pad the crank arm with some on 2 adjacent sides of the square crank taper. This will take up some slack and also set the crank arm outboard a little as well, if there are any clearance issues
Yout could try some sort of lock washer on the bolt (between the bolt head and the crank arm., but not likely to be needed. Once you’ve got it sorted, then apply a little locktite, but not the permanent kind, just the regular, so you can actually remove it later if need be.
Good luck and if nothing works, might be time to upgrade, and that’s never a bad thing, excpet for your wallet!
Just to make sure I got this right… You’ve ridden this bike before with no problems, and just recently it was getting loose (and wouldn’t tighten back and stay there), and you haven’t replaced any of the parts in the mean time? Or has this bike always had this problem?
First option. I’ve owned the bike for a few years, but it has very limited miles (a few hundred probably). My work schedule now allows me to ride to work at least some days, so I dusted it off and used it. On my first day commuting, the crank arm came loose after about 10 minutes. The rest of the way to work and home it was loosening as fast as I could tighten it.
Thinking back tho, this happened about 2 years ago too. I had no tools with me then, and got to do a one leg drill all the way home on a single speed with platform pedals.
Even tho it seems to be working now (after a short ride), I suspect there is still a problem. I may still look to upgrade to a cheap octo. I’ve at least wrenched them before and I understand them a bit better.
Okay, yeah, given that, I’ll stand by my earlier diagnosis. The unfortunate thing about square taper is that unless you can torque that bolt down pretty tight, it’s gonna loosen. And then if the tapers are damaged, it won’t matter how tight you get it, it’s gonna rock its way loose again. If this were an issue that had happened since day one, then I might think the bolt was bottoming out before it got the crank tapers to bind up. Wouldn’t really prevent the damage to the crank tapers though. Aluminum crank against steel BB spindle… doesn’t take long to make them beyond repair if it’s loose.
