Critique my chainline
 

I posted this picture (along with a few of the rest of the bike) on the "SS/FG Photos" thread. A comment by dddave said "the chainline on that gitane looks like sh*t."

http://farm3.static.flickr.com/2621/...fb507937_o.jpg

Just looking at the photo, I can't entirely disagree, but I can't put my finger on what looks wrong. A while ago, when I first put this cog on, I got down under the workstand and put my eye to the crank and concluded that it looked very good. I'm now trying to convince myself that whatever is going on in this photo is just optical illusion, but I don't know if I buy that.

I asked dddave to elaborate on the other thread, but then I decided to solicit more opinions, not being sure how much traffic the photo thread gets.

So, what do you think? And don't just say it sucks...be specific please.

My chainline is the same way. Almost looks as though the cog and the chainwheel are at oblique angles instead of parallel.

looks like the crank spider or chainring is bent.

Ride it. If it doesn't fall off or make a bunch of noise - leave it!

never take pictures of mechanical parts close up with a wide angle lens.....try using a normal to mildly telephoto lens next time from further away.

That said the top of the chainring does look bent

Just measure the chainline if you really want to know. Photos often suffer from perspective issues that make it impossible to know.

It's easy to check whether you chainring is bent -- it should be obvious by eye as it rotates, or you can pull it and lay it down flat.

This picture was taken with a relatively normal lens -- the built-in on my Canon PowerShot S2 IS. I was just happy that it decided to focus on the chain and not the tire. :)

I'l take a closer look at the chainring. It is the stock ring from my cheapo Origin8 crankset. Somebody here said the rings on those were criminally unsafe or something like that. I hadn't really noticed, but it wouldn't surprise me too much if it's bent.

it's fine, man. Just ride it. It's not as bad as others I've seen.

If your ring is on the inside of the spider, you could try putting it on the outside, it might help a bit. I really doubt your chainring is bent like the others say. more likely your chain is going inward at an angle and then once it hits the chainring it straightens back out, making it look bent.

Now that part is definitely an illusion. The hub here is a Formula flip-flop with a 42mm chainline (measured), and my chainring is on the outside. Within the margin of error of my measurement, it's just about perfect. Of course, the measurements assume the frame is straight. But I think it is. I've checked that.

In the picture, it definitely looks like the chain turns outward at the front of the chainring and inward at the bottom of the cog. I looked closer this evening, and neither of these things seems to actually be the case. The chainring doesn't seem to be bent either.

I guess it's just my photography that's sh*t. :p

So maybe my question should have been, how do you take a good chainline picture?

its satisfactory.

A good way to see if your cog and ring are aligned is to use a straight edge.

I like to use a three foot level. With the chain off the cog and chain ring, lay the straight edge on the face of chainring. I rest it between two legs of the spider. It must be flush against the face. Then rotate the crank/level down until you get close to the cog.

This will not tell you your chainline but it will tell you how close your cog and chainring are. Which is what you really want.

The lenses in compact cameras are notorious for distortions in this kind of photo--you won't notice it in a lot of snapshots, but take a picture of anything straight, or get too close while you're zoomed wide, and you'll almost always see it.

If you'd taken this photo with a Canon L-series lens, it might be a different story, but I'm betting the problem here is your lens and the perspective, not your chainline.