Singlespeed & Fixed Gear - question about slack in chain/"play" in cranks

hi, just got my bike finished up last night (old schwinn road frame and various junkbin parts), and went on the "maiden voyage" this morning on the way to work. lots of fun. i dig the simplicity and lightness of my new bike (beats commuting on a big ol mountain bike). but i noticed one thing:

there's a little bit of "play" in the cranks. by this i mean that if you push up and down on the pedal, or forwards and backwards, you can move the crankandpedal a little bit w/o moving the wheel. it's just a little bit. it's like there's a little bit of slack going from forwards to backwards. just a little. is this just because there's a little slack in the chain?

and i'm no physicist or anything, but couldn't the slack create more of a force on the rear wheel and cog than if it was perfectly smooooth(is perfectly smooth even possible?). is this bad?

sorry for all the probably assinine questions.

dan

A little slack is ok. You can tighten up the chain more, but if it makes noise then it is too tight.

Getting just the right chain tension can be tricky depending on how good your chainline is. Just make sure it isn't too loose.

Matt

Thanks for the post guys... AS a newbie, it was helpful for me.

if you have a real fixed gear hub w/reverse threading than it shouldn't be a problem. When I was using a converted hub and I had too much slack it was a big problem. Usually you can feel your cog slip a bit and fix it before a catastrophe. and if you're skidding on a converted hub then you're braver than I; which isn't saying a whole lot. keep those lockrings tight.

jeff

I give about 1/2" max total slack. Just grab chain with your fingers at midway point and pull up & down.

I give about 1/2" max total slack. Just grab chain with your fingers at midway point and pull up & down.

ok, so is there any reason for doing this? does it help if the chainline isn't perfect? is it a convenience thing?

i do in fact have a true fixed hub w/ reverse threads and a lockring and all that. so if i'm not doing any harm to the hub and there's no(or little) risk of things breaking there, my next question is:

is the slack possibly bad for the knees?

thanks for all the help so far.

dan

the trick i used to get good chain tension on a fixie conversion is this:
pull the wheel as tightly back as you can into the drops. i then would push the wheel crooked against the chainstays on the non-drive side and tighten that side. i would then push the wheel back into the center of the stays, hold it there, and tighten the drive side. if the wheel was a little crooked still, i would slowly loosen which ever side the wheel was pointing towards and it would then sort of pull the wheel into center, then of course tighten it back up. i absolutely love my chain tensioners for the track ends on my iro. it makes life so much easier.

is the slack possibly bad for the knees?danIf you're worried about your knees, just keep your gear inches low.
A 1/2" chain slack as I mentioned earlier is not noticable while riding. The only time I notice the very tiny amount of 'play' in my cranks due to chain slack is when I'm trackstanding, but this is not annoying.

George

thank you everyone. some very good advice. i will try your method isotopesope. sounds like a good way of setting the rear wheel up.

thanks again all.

dan