mashedpaters

I tried searching but couldn't find any luck, please forgive the n00bness.
In a nutshell, with one pedal in the down position the chain is snug and good, though 180* later with that same pedal now up, the chain is much looser. I have not noticed the issue before but I cannot get the chain on tight and snug without making it too tight for part, or part of it is tight and the other half of the pedal is loose.
Is my rear wheel not true, bent, chain messed up, crankset (brand new), etc?
Thanks in advance.

xkillemallx16

your chainring is not perfectly round.

531phile 

Spin the cranks and see if there is any side wobble, the crank may be loose or not seated all the way in. A poor chainline coupled with a crooked crank could cause this, I'd imagine. An oval chainring will definitely cause this. Are you using a crankset meant for multispeed bikes??? They have ramped and/or irregular teeth. Some are shorter than others. This could possibility be the issue. Ask the big brains in the Bike Mechanic forum.

If none of these solves your problems. Sounds like a half-link is what the doctor would order to get better tension.

prathmann

Or, more likely, the chainring is not centered quite right. There's usually a little play in the bolts that attach the chainring to the crank. See the section on "Centering Chainwheels" on this page:
https://www.sheldonbrown.com/singlespeed.html

mashedpaters

I just took off the chainring and put it on the back (rather than the front) of the spidering-looking crank side to even out the chain line as my spindles are a tad long. I read the sheldon brown thing, and just to confirm, I'm supposed to loosen the bolts that hold the chainring on the crank, then tighten them like the lugs of a car?
Thanks guys, you're crazy quick, I appreciate it.

531phile 

Most of the times you can use just your fingers to hold the nut in place while you tighten it with an allen wrench and it will tighten fine. But sometimes you can't get one bolt fully tightened because it would spin round and round. There's a special tool that Park makes that has three prongs that you insert to the end nut so it doesn't spin. Maybe your chainring is loose because you can't get one bolt all the way tight???

And use a Star pattern when you tighten it. Don't tighten it going around. I normally tighten them all few threads at a time in a star pattern, get it all seated and then go to town again in the star pattern to fully tighten them.

mashedpaters

I will definitely check the chainring cause I just held it with my finger, but it seems like a relatively thin flat head screwdriver would work to hold the back piece in place.

Ken Cox

All chains have tight and loose spots.

The more money you spend on frame alignment, bottom bracket, crank, chain ring, cog and hub, the more even your chain tightness.

All the tiny increments add up; all the out-of-roundnesses and misalignments can periodically conincide in one big tight or loose spot; and, they can all cancel each other out.

You can chase it forever and you'll never get it perfect, but you can make it better.

I can't prove it, but I think having prime numbers for both the cog and chain ring can help (47 X 17).

mashedpaters

that makes a lot of sense, thanks bud. I think its worse now and I'm really noticing it since I put on my new chainring and didn't do with the chain on, and didn't tightened them like the lugs of a car for even-ness's sake. side note, I just went from 52-17 to 46-17, so I'm almost there with ya.