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Currently I'm building a new Surly Cross Check, and it needs a 68mm BB (english threaded).

Furthermore, I plan to use a cheap $15 shimano BB with JIS square tapered interface, nothing special.

Do I need to bring my frame to a LBS and ask them to chase the thread? or I can just use a toothbrush and some soap to clean the thread?

EDIT 1:

Is Chasing necessary? or is it an optional process to allow the BB fits better?

EDIT 2:

picture:

The ink splat is because there's a hole for dérailleur cable hanger.

enter image description here

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If you don't chase when you need to, you'll have a very tough time threading the bottom bracket in, and as a result, it may creak or wear out somewhat faster than it would otherwise.

The same goes for facing the bottom bracket shell.

This is what I would do (and have done) if I were in your position, only for square taper, cartridge bottom brackets*: Since you are using a square taper bottom bracket, your BB will likely have one fixed and one free cup (or whatever its called). Take the free cup, and thread just that into the shell without using any tool besides the driver (example), only finger tightening it. If you can thread that all the way in until its outer flange is flush with the shell, then your frame is "good enough" as it is. Unthread the free cup, and install the BB properly and you should be good to go.

If you can't get the free cup all the way in without using tools, then I would have the threads chased out.

I used this method on my Surly Cross-check frame in 2007, and the threads were good enough then, and I haven't had any bottom bracket troubles whatsoever.

And cough up the extra cash to get the better bottom bracket, it will last longer, and every time you have to take square taper cranks off, you wear them out much quicker.

*Hollowtech and other outboard bearing systems are more sensitive to the threading, and especially the facing of the shell. If using those systems, always have the bottom bracket faced, and at that point you might as well chase out the threads.

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No, usually you don't. That's something that should have been done at the factory.

If the threads do need chasing, then you'll have to take it to a shop. The point of chasing is to remove paint over-spray - you can't do that with a toothbrush. A chasing tool probably costs more than a Surly frame, so doing it yourself isn't practical.

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  • Do you mean chasing is not necessary? I'm trying to find an answer in the internet, but people are generally divided into two: chasing or not chasing. Does it mean if the thread is chased the BB will fit better and prolong the quality of the bike?
    – azer89
    Mar 26, 2015 at 2:40
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    Funny, the Park BTS-1, the tool for the job, is almost the exact same price as the CC.
    – whatsisname
    Mar 26, 2015 at 4:18
  • @azer89 - Chasing is usually not necessary. It's necessary if there's enough crap in the threads to keep the BB from screwing in properly - otherwise it's a waste of time. See the answer by whatsisname.
    – Mike Baranczak
    Mar 26, 2015 at 5:48
  • @whatsisname - I've also heard of people making a homemade chasing tool from an old BB cup. I don't have an illustration, but the idea is to simply cut a chunk out of it, like you would cut the first slice of a cake. I've never done it, so I won't endorse this method - just throwing it out there.
    – Mike Baranczak
    Mar 26, 2015 at 17:50
  • @azer89: whether you need to chase or not will depend on each individual frame or maker. Obviously, if you already have the tools, there is no downside to always chasing, but it isn't always totally necessary.
    – whatsisname
    Mar 26, 2015 at 18:23
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I find that after painting a bicycle frame, and after removing the masking tape over the bottom bracket, that some after spray enters the bottom bracket. I clean the overspray with acetone and lacquer thinner with a q-tip, then wipe off; repeat several times. This usually cleans to the point that thread chasing is not required.

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