3 chainring to 1 chainring

[Aaron09]

I am going from a 3 chainring to a 1 chainring. My current BB is 68mm with the spindles measuring 122.5. I am looking to get a new bottom bracket, but I am unsure what size. Any thoughts? The original chainring was 48/38/28 teeth and the new one will be 39t.

 

[dabac]

To me it wouldn't make sense to replace a 38 with a 39 unless the 38 was due for replacement anyhow.
It's a 2.6% difference, far less (say 1/3) than the regularl difference between gears in a cassette rear.

If you find the big and the small so horribly disturbing, why not simply pull them off, switch to a shorter set of chainring bolts and call it done?

 

[Aaron09]

Unfortunately, the bike I have doesn't allow me to disassemble the original chainrings. That was my initial plan.

 

[dabac]

What are you hoping to gain from the switch, reduced weight, style points?
Do you have the tools required to remove the current crank and to remove and install a bottom bracket?
If not, having a shop do the switch will cost about the same as the tools. Better have a shop order the parts and do the switch for you. Then they'll figure out what parts you need.

 

[Aaron09]

I have the tools and currently have the crank and bottom bracket out. Bottom bracket housing been cleaned. I am wanting to do this since all of it needed to be replaced and I wanted to try a different setup.

 

[Aaron09]

This is before I pulled the crank and BB to replace. All the other work I had already did.