Bolt Slippage/Threadlocker?
 

Hey so the little bolts that hold the crank to my new 48 tooth chainring keep loosening themselves.

This is a SuperMaxy crank and chainring that I cannibalized from a touring bike (ie, there were two smaller inner chainrings that I removed). The large chainring is held on to the crank by its own set of bolts.

http://bikeforums.net/attachment.php...hmentid=137655

I'm guessing that they keep loosening because it was meant for touring use and not designed for the stress/strain of fixed riding? Anyways what should I do? Should I just find a one-piece chainring or should I try cementing the bolts in place with some threadlocker?

And no, those arent the original bolts. I know its super ghetto, but I got the 'ring and crank for basically free so I want to ask whether its worth trying to make this work or just get a proper crank and chainring.

thx

You shouldn't have to use thread locker, make sure your tightening them down properly, the threads should be properly lubricated and you will most likely need a special tool that hooks onto the reverse side of the bolt, they should be fairly tight ~5nm for steel bolts if memory serves but I'm doubting you have a torque wrench so I won't bother looking

Make sure the bolts are short enough so they are bottoming out against the chainring not themselves, if this is the case you need new chain ring bolts and no amount of threadlocker will help, infact if your having problems with it threadlocker would probably only make your life much more complicated

A torque wrench? Jeez... Yea i know what special tool youre talking about, but I only had to use that for the bolts that held the smaller chainrings to the larger one. These bolts (and the one original) holding the crank and ring together are regular hexagonal nuts.

And every time I tighten them down I do it to the point where I cant go tighter without stripping the heads. They just keep coming loose 30 minutes into riding.

Jeez for a torque wrench?

So the other things I said?
did you lubricate the threads?
Are the bolts too long?

Edit: I somehow missed your picture, so disregard the bolts being too long option, did you lubricate them?
I have an TA crank that uses the same set-up and I've never had the bolts come loose on me.

Edit again: Now that I understand what bolts your talking about I Might consider thread locker if I was in a jam but if you have the money to upgrade certainly do. The fact that you "do it to the point where I cant go tighter without stripping the heads." tells me either those bolt won't work for that application if they're comming loose in 15 minutes

no the threads arent lubricated. does lubricating them help keep them tight? seems counterintuitive...

theyre not even the original bolts so maybe i should just get other ones.

Lubricating threads does seem counterintuitive doesn't it? but what it does is reduce the friction created by the threads so you can get them tighter before they will strip, most all metal on metal contacts should be greased/lubricated on a bicycle.

I would spend some time investigating, when you get them tight if they are actually tight against the chain ring, or are they tightening against themselves?

I'll have to see how things go once I get some proper lube (is WD40 ok?), but im sure the bolts arent bottoming out on themselves, cause they are threaded the whole length of the shaft. When I tighten the bolts, im sure its tight against the 'ring, cuase theres no play or slippage between the ring and crank. After they come loose, then the ring and crank start to seperate and its just the bolts themselves providing the torque, not the contact of friction between the ring and crank.

WD-40 is not okay its not a lubricant no matter how bad it wants to be.
so is the chainring/spider threaded or is it a nut and a bolt? I've been assuming a nut and bolt
Thinking about it more and more I'm thinking theres a bigger problem than lubricant at play here, the first step if your really serious about keeping the crank would be to go see if you can find the right bolts for it, while your at the lbs if they don't carry them they might be willing to look it over, it could be somthing really obvious when in hand. (at least to a pro)

Based on the age of that crank it may be best to just get a new one, the correct bolts may be difficult to find (unless I'm overestimating that cranks age due to the design)

I would get some lock threads, or use lock washers.

Mine did that once when I put it on the inner part of the spider, then I re-tightened it and never happened again. Do you tighten it in a star pattern? I don't know if that's how you're supposed to do it but I would think so.. tune my drum that way.

Makes no sense +1

If you aren't using the correct bolts you'll have nothing but trouble. Even a tiny bit of play will force them loose, as you've seen. WoundedKnee is right, you must tighten the bolts as you would a drum, not in a consecutive fashion.

Remove all the bolts, put them on using just your fingers. Tighten #1 just a little, then skip over to #3 or #4. Tighten just a little then to #2, then #5; tightening each bolt a little at a time so the chainring is pulled to the spider evenly. If they still come loose, you need new bolts. Or worse, the spider holes are wallowed out. If you ride a lot with loose bolts, that can happen.