Skelleyfixie

In between jobs right now and looking to replace my crankset(there is some play going on) on my fixed gear in a relatively inexpensive way. Curious whether the amount of teeth need to be the same as well as the arm size as the current one. And if there are any specs that I should focus on as well.

I currently have a square taper, 44t 8in arms

found these on ebay, any input would be greatly appreciated

https://www.ebay.com/itm/290771941042...84.m1423.l2649

https://www.ebay.com/itm/400343021933...84.m1423.l2649

Airburst

Play would tend to indicate an issue with your bottom bracket bearings, not the crankset. If you have a cartridge bottom bracket, it needs replacing if it's got play. If you have a cup-and-cone one, you can disassemble, service and adjust it so it runs with no play. Your crankset is probably fine.

If you do replace the crankset, there's nothing to say you need the same number of teeth on the chainring - if you have fewer teeth, you'll get a lower gear, but you'll probably have to shorten your chain. If you have more teeth, you'll get a higher gear, but you'll probably need a new chain, as your current chain won't be long enough.

If you get a crankset with different-length arms, you'll have to adjust your saddle height, but nothing else should change. Technically longer cranks give a slightly lower gear, and shorter ones a slightly higher one, but the effect is minimal.

The main issue with replacing a crankset is chainline - how far out the chainring is from the centreline of the bike. If you don't match the chainline, your chain will run noisily, or it won't stay on. Different cranksets will have different chainlines with the same bottom bracket spindle.

Skelleyfixie

Thanks for the breakdown! Very helpful.

I have taken my bike in to the local shop(s), one in Dallas then one here in Florida, the one in Dallas said it was the BB but the guy here told me the BB is fine and my problem lies with the crankset bc the connection b/n the arms and the chainring is loose

Andrew R Stewart 

Not that this is likely but a "loose" crank arm could be a worn spindle hole. This would require the replacement of the crank arm. But this is easy to check for. Andy.

Airburst

Ah, right. That is indeed the crankset, I was assuming you had a higher-end crankset that had the chainring bolted to the crank. Cheaper cranksets with the chainring(s) swaged onto them can indeed fail as you describe. If there's no play when you try and rock the crank arms left-to-right, it's not the BB. You should be able to see the play in the chainring/BB joint if that's where it is.

The two cranksets you linked to won't fail in the same way, as they appear to have what's known as a spider as part of the right-hand crank forging which the chainring bolts onto.

Dependingon where your wheel is in the dropouts/track ends on your frame now, you might be able to get away with switching from a 44-tooth to a 46-tooth chainring, or if not, you can replace the chainring with a 44-tooth one of the same bolt circle diameter.

Also, some cranksets have the spider swaged or pressed onto the right-hand crank, and the chainring(s) bolted to that. The swaged joint can still fail in the same way, but if you're lucky enough to have one of those, you may be able to reuse the chainring off your old crank.

pierce

the first one you linked has a steel chainwheel, while the 2nd one has an alloy chainwheel. steel chainwheels might last longer, but are a bit heavier and also sometimes noisier in my experience. The alloy one has 130mm "BCD" (Bolt Center Distance), which is probably better for a fixie application, but means the smallest chainwheel you could put on it is 39T, while the 110mm spider would take a smaller chainwheel (not that you're likely to want smaller on a fixie).

those are both 170mm long arms, which is the 'standard' size. you might look on the back of your current crank arms and see if there's a number like 165, 170, 172.5 or 175 (those are the common crank arm sizes). longer arm gives you a little more leverage, but means your knees travel farther up/down. its all a tradeoff. short legs prefer shorter crankarms. shorter crank arms are easier to 'spin' (pedal at high cadence), while longer arms tend to promote 'mashing' (pedaling with high force).

Airburst

The difference in crank length between 165 and 175mm is obviously 10mm, or as about 6%, in other words very little. I've always suspected that any actual difference in "feel" between crank lengths in between those two values is mainly down to expectation - a rider expects them to feel different, so they do.

pierce

a 175mm crank makes your knees move up and down 20mm or almost an inch more total than a 165mm crank. when you're spinning at 90 or 120 RPM cadence, that inch is a fair amount.