turning a double ring crank into a single ring
 

Hey guys. I'm turning a bike into a fixed gear and in the interest of saving money, I removed the small chainring. When I bolted the big ring back to the crank, I noticed that the rear of the bolts vary in the amount they extend away from the crank and toward the frame. They're all really tight, and I've tried to tighten it more, but they won't compress anymore. None of them are contacting the chainstay, but some come close. If I could take good pictures of it I would. Anyway, I was wondering if it's a bad idea to ride on this crank with the varying lengths of the bolts in the back. Again, it's still strong feeling, I'm just not sure how ok it would be to ride on. Any help would be appreciated! Thanks!

you either need crank spacers or BMX/Track/Single Chainring bolts. You ***COULD*** grind down your double bolts, but it is easier, safer, and faster just to buy a new set.

Ok, so my next question is this: Why can't you just use the double ring stack bolts? I mean, it's essentially clamping the ring against the crank right?

Because they are too big. A double stack bolt holds together 3 pieces of metal: the big ring -- the crankarm spider -- the small ring.

When you run one chain ring, you eliminate one of the pieces of bread in that sandwich. And your bolt is too long. Which you've found out yourself.

I suppose you could McGuyver yourself a fix with some washers or something. Or you could get a set of single stack bolts (just $6 or 7 at your LBS or online) you get the parts that fit just right and save yourself a huge headache. That was my experience anyway.

Cool. Thanks!

Haha, that's exactly what I did! And I needed to grind down one side of the washers to do it.. all because my LBS said they don't make chainring bolts any smaller than what I had. So all that fit at my LHS (local hardware store) were nickle-plated ones and now they're rusting because I ground them down.

So really, get a bunch of nice short-stack bolts (made out of steel if you're really classy), paint 'em whatever you want.. and apply liberally. One can never have enough single-purpose bolts.

Flip the chainring. It probably has recessions for the bolt heads for the "right" way to mount it. If you filp it, the bolt can't sink in, and you'll get a few extra mms of tension. I did this on mine with double-size bolts and haven't had a problem in over a year.

oooh, nice touch rugen. That didn't occur to me at all.

Watch your chainline. The big ring on standard doubles is usually about 46mm from the centreline if the frame. Standard hub / cog combos give a 42mm chainline. Well, they're supposed to, but check Sheldon Brown's chainline article to be sure. Or just measure.

If your chainline is off by 3mm or more, you'll want to correct this by either mounting your ring on the inside or getting a BB with a shorter spindle. The first method may not work, as the chainring may hit your chainstay. The second method may necessitate grinding off the shoulders of your crank (i.e. where the inner chainring would go).

I still have the double chainring set up on two of my fixies :) have even swapped the inner and outer rings around to change the gearing :)

You can just see in my Falcon's pic the smaller ring on the outside 42/46
http://i94.photobucket.com/albums/l8...s/000_0266.jpg