The bike: Stock Schwinn Trailway.

The primary goal: Extract and service (replace) the bottom bracket, which is making a clunking or popping noise

The secondary goal: Expand my toolkit

Seems simple, but I am confused about a few details. The questions:

1) How on earth do I find out what size BB these bikes have? I found out that they're "Square Taper" types, but looking up replaces leads me to a prompt for sizes.

2) What specific tool would do the extraction? I know what it looks like, but I don't know which one is exactly right.

Thanks!

M.

OK accepting that they're square taper, then your Schwinn would have a threaded 1.370 x 24tpi BSC, (now ISO) BB. The main variable would b spindle length, but you can measure that anytime once the cranks are off.

Removing the crank requires a crank remover, but be careful, they come in 2 basic types, the older version for square taper, and the more recent version for OS splined spindles. The difference is in the pusher pad, and you need the right type.

Once the cranks are off, you can work on the bottom bracket, which requires different tools according to construction.

hard to say w/o pics. you could take the bike to your LBS and i'm sure they would be more than happy to expand your tool box. OTOH if you take a pic, there are a lot of people here who, i think, would be post advice.

I'm not sure how you looked up bottom bracket without coming across Sheldon's the or Park Tool sites, both of which have very full explanations with pictures of bottom bracket specifications, tools and adjust/repair procedures. There's no need to repeat everything here, so just Google (replace/overhaul/adjust/fix) bottom bracket and hit the YouTube option for videos.

As for size, you don't even know if you need to replace anything until you disassemble, at which point you have the parts in your hand to measure or take to a shop.

Forgot about the thread! Thanks for the feed back. I read Sheldon's site but I'm afraid I might not have gotten it the first time through. Happens sometimes.

FBinNY: Is there any way I can tell by looking which specific one I will need to pull the cranks off?

M.

Since you probably have this bike:
https://www.target.com/p/schwinn-men-...y/-/A-13241180
I am 99% sure you will need these tools or something similar:
https://www.parktool.com/product/cran...-cranks-ccp-22
https://www.parktool.com/product/bott...et-tool-bbt-22

Here's the Park page on disassembly and reassembly: https://www.parktool.com/blog/repair-...e-spindle-type


Since you describe that the crank is making a clunking or popping sound, it could be that one of the crankarms is a bit loose, or the bottom bracket is slightly loose in the frame. You might get away with simply tightening everything up. The best way to tell is to derail the chain off the chainrings and spin the cranks slowly. If they turn smoothly you're probably OK with simply tightening everything. Note that the bolts holding the cranks to the bottom bracket need to be very tight- 25 to 35 foot-pounds of torque. Not getting these tight enough can allow a crankarm to work loose, ruining it.

Remove the arm retaining fastener, usually a 14mm nut/bolt or a 8mm Allen headed. Look at the now exposed arm/axle interface. Is the axle/arm contact in the shape of a square almost a 1/2" across or is it a "round" shape with many small splines? The square shape is the traditional tapered square type. the larger around with 8 or 10 notches/splines is the newer splined type. the tapered square arm pulling tool has a smaller end pad (which will fit inside the arm's square hole to push on the axle end). The splined type puller has a larger pad, to fit against the larger around axle end. Otherwise both pullers have the same general design. Their description should state which is which. Andy.