Singlespeed & Fixed Gear - Upgrading crankset noob questions

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I wanna change my crankset to one of those 5 arms spider cranks. Leaning towards eightinch or origin 8s. I started reading up on how to do it and dayum its getting kind of complicated. I would appreciate some advice please.

I think I have some old skool bb. Bike bought from bikes direct affiliate on ebay for mad cheap. It just lists my bb as euro cartridge bb. Looking at it, its a square taper with lock ring on non drive side. Chain line is about 44mm. I messaged the seller to ask for the measurements of the bb but haven't heard back yet.

With that said, do I have to buy crankset that matches my bb so that the chain line isn't wacked out alignment? Or if I buy a crankset and a matching english(?) Bb with a spindle length different to what I have now, will it disalign my chain line? For example, if my current bb is 110mm, and I buy origin 8 crankset and the 107mm bb that it requires.

Thank you.

The BB is different based on the cranks offset. So crankset first then the BB to fit the frame in question.

Did you know that England is in Europe?

When you remove the bottom bracket, the spindle length will be marked on the cartridge body, or on the spindle itself if it's cup and cone style.

Also, keep in mind that you need at least two special tools to do this kind of work yourself. You'll need a crank puller to get the crank arms off, and you'll need a bottom bracket removal tool to get the BB out. Expect to spend 30-40 bucks to purchase those tools at a LBS.

As an alternative, you could get the LBS to do it for you. You'll probably get charged 20 to have them do the work. I'd also recommend picking up a chainring bolt spanner so you can get chain tension dialed in.

60 for the eighth inch track crank
30 for assembly tools
30 for new BB
5 for chainring bolt spanner

Looks like you're up to about 125 to do the job. How much did you spend on the bike?

Is your crank broken?

Yeah I'm taking into consideration the costs and the crank is not broken. I guess I'm just using this as a learning experience. This is my first ever bike and learning as I go. Eventually, il build my own bike. Or just upgrade bit by bit until I have a totally new bike.

So basically, a crankset with its matching bb will have a good chain line on any standard single speed frame?

Yeah I'm taking into consideration the costs and the crank is not broken. I guess I'm just using this as a learning experience. This is my first ever bike and learning as I go. Eventually, il build my own bike. Or just upgrade bit by bit until I have a totally new bike.

So basically, a crankset with its matching bb will have a good chain line on any standard single speed frame?

Yes.

I recently replaced my BB/crankset with Brev M chainring and a Grand Cru Threadless BB (103mm spindle length). I had a similar concern, but the only problem on installation was that the pedals were dangerously close to chaffing the BB.