Singlespeed & Fixed Gear - newb question: chain tension/ gear alignment?

sorry if i make no sense i am new to building fixies and bikes.

my chain keeps falling off even though I have plenty of tension. It looks like the chain is is being pulled to the side and the gears are not aligned. how do i check to make sure the gears are aligned/ spaced properly? is their a cheap and easy way to get the proper spacing/ alignment so my chain doesn't fall off when at tension if they are out of alignment with out having to buy a new wheel?

If your chainline looks off, it is off. You can either purchase a bottom bracket with a shorter spindle (if crank clearance allows for it), or you can re-space and re-dish your wheel to bring the cog closer to the dropout.

Replacing the bottom bracket is easier, re-spacing the wheel is cheaper (assuming you do the work yourself).

i know i don't have the clearance for the bottom bracket, how do you re-space the wheel?

i know i don't have the clearance for the bottom bracket, how do you re-space the wheel?

Let's see some photos of your rear wheel to better advise you.

Here it is

http://i262.photobucket.com/albums/ii107/csbaxter/IMG_8971.jpg
http://i262.photobucket.com/albums/ii107/csbaxter/IMG_8972.jpg
http://i262.photobucket.com/albums/ii107/csbaxter/IMG_8973.jpg
http://i262.photobucket.com/albums/ii107/csbaxter/IMG_8974.jpg
http://i262.photobucket.com/albums/ii107/csbaxter/IMG_8976.jpg
http://i262.photobucket.com/albums/ii107/csbaxter/IMG_8975.jpg

rad.

Yeah, new BB in order. Just eyeballin' but about 15 mm shorter than what is there.

After seeing that Scott in the background, any way we could work up a photo of your library?

im sorry if this question sounds stupid but im new to working on bikes. what is BB?

The scott is my wifes, i also have a marin bobcat mountain bike (with studded tires) which the fixie is replacing for my commute to work.

never mind the question. the bottom bracket can't some in any closer or it will hit the bike.

can i get a new rear wheel that will push the gear out far enough?

never mind the question. the bottom bracket can't some in any closer or it will hit the bike.

You'd be surprised.

EDIT: meaning, my track bike is balls to the "bb" or bottom bracket. The crank arms are right up on the shell, but chainring and all spin freely. Granted, this has a different geo, but I'm confident a shorter BB would give you enough clearance.

Easily measurable, divided by two.

never mind the question. the bottom bracket can't some in any closer or it will hit the bike.
Once you move your chainring back to the outside position of the crank spider, then you'd have room.

Could be the angle of the picture, but it looks like the dish of the wheel is off. Looks like the rim is way off to the non-drive side, almost hitting the chain stay. Juggling axle spacers will get the wheel centered and bring the cog more in line with the chain ring.
Have you measured the chainline at the crank and cog?
http://www.sheldonbrown.com/chainline.html

I had the same problem when I was building up my current bike. Before I got a new BB, i lined up the chainring and rear sprocket simply by putting a spacer on the non-drive side of the wheel. Its important to be patient

I may be imagining it, but it also looks like the cog may be on backward. To my eyes it looks like the tapered side is against the lock ring instead of against the hub.

That hub looks like a standard loose ball cup and cone type, such that the spacers on the right side can be moved to the left and the axle readjusted to be centered. Then the rim needs to be re-centered on the hub so that it is centered in the frame. That will move the cog outward considerably, which should help a lot if not completely solve the problem. Your chainring is hitting the chainstay, because that frame was designed for a double chainring crank, such that the inner chainring is much smaller. You may need to get a smaller chainring to make this work.

I may be imagining it, but it also looks like the cog may be on backward. To my eyes it looks like the tapered side is against the lock ring instead of against the hub.

I think you are absolutely correct. That is just making the situation that much worse.

Is that a suicide hub?

Is that a suicide hub?

Difficult to tell for sure from the picture angle, but it certainly looks like it.

Da plot thickenz.

Da plot thickenz.

Idk if its just me but imagining you saying makes me laugh..
http://www.bikeforums.net/attachment.php?attachmentid=204581&d=1307134076

I may be imagining it, but it also looks like the cog may be on backward. To my eyes it looks like the tapered side is against the lock ring instead of against the hub.

I came here to say this, now that Scrod has edumacated me on the correct orientation of a cog :thumb:

http://img.photobucket.com/albums/v166/scrodzilla/BF/plot.png

Lolz thank you scrod now we can all laugh

So, unscrew lockring + cog. Flip cog.

Put the chainring on the inside of the crank arm if it isn't already.

Stack washers on the non-drive side of the axle... not more than half cm or so worth.

and a front brake and foot retention

thanks for the advice, let me see if this works.

so after care full inspection the bike chainring looks bent and i think that might be contributing to the chain falling off. also the cog was on backward. got that switched.

.