[mtncycle]

I recently built up a beater for riding around the city and to the bar, and wanted to keep it simple, so I set it up single speed. For cranks, I slapped on an old pair of suntour triple-ring cranks I had laying around, using just the big ring (46) and 14 in the rear (the chainline was perfectly straight, btw). On the second ride, while coming up a hill, the big ring just folded over and I nearly went over the bars.

Since it's a beater I didn't want to put much cash into it, so I found a brand new pair of shimano alivio cranks on ebay for cheap. Since the big ring was only 42, I thought maybe these would work. Third ride, same thing happened. WTF? I see guys on track bikes with way harder gear ratios -- are single speed rings thicker than regular rings? Or is it just that the rings on the cheaper cranks are a softer metal? I mean, I'm a fairly strong rider and all, but come on -- I've been riding mountain bike for over ten years and have never seen rings fold over like that before. Anyone else ever experience this? any suggestions?

 

[sanjuro]

I would check your chainline. I used my middle ring and the chainline is pretty good. I suppose could put your big ring into the middle as well.

But you are exerting much more force in that one gear. It seems odd, but it sounds like you are using the cheapo stuff. Try getting a stronger chainring and see what happens.

 

[zebrahum]

I agree, I think getting a single speed chainring will help a lot. The shift ramps can tend to let your chain move around while under stress, so getting a ring without ramps will probably help.

 

[Arsbars]

As mentioned the whole chainline thing. I've also found that over 36t if you run a smaller geared chainring they will bend depending on what bolt circle diameter (bcd) you are using. I love Salsa chainrings, and if you have a dime to drop the Boone Ti rings will last you a life time.

The Salsa rings are normally around $25 depending on what size/color you are going for.

hope that helps