Hi all. I am working on a design for my first carbon fiber frame. I have some experience on carbon before, so have pretty good idea on making the frame. However, I have very little knowledge on bike parts.

Here what I have so far:
Geometry similar like Specialized Roubaix with some modification. I keep the head tube and seat tube angle 72 degree.
Fork: I may end up buying some generic fork.
Gear rear 8-10, and front single. (don't know brands and sizes yet)
I like the horn style handlebar with time trial gear shifter. (don't know brands)

which BB should I choose? 68x41 or 73x41, threaded or no thread.

Space between rear drop out?

Head tube diameter? I guess depend on steer tube.

Hopefully I can get some advice before making fatal mistake. Thank you.

Your method of executing the chosen design will be of more importance than what specs you settle for. Are you making tubes and bonding them or a foam core with the fiber laid on top of it?
130 is pretty standard rear spacing and 1 1/8 HT , 68mm BB.
You will need to source the metal parts and make sure you do your homework on prepping and bonding them into carbon.

I would read THIS thread. Lots of good info on the carbon build process.

Hi Canaboo
I will make most of the tubes first, then bond them together. I don't like the foam technique. As far bonding aluminum and carbon, I done that before. Ok then I will start with 68mm BB. Threaded or not?

Thanks for the link seankanary.

The larger bearings and shell size of BB30 and PF30 threadless bottom bracket systems are perhaps a bit more optimized for carbon frame construction, but you will then need to select a crank, bottom bracket and shell that are designed to be compatable with eachother. paragon offers some of these shells;
https://www.paragonmachineworks.com/c...&category=BB04

If you are using a conventional threaded british/ISO bottom bracket, then use a threaded 68mm shell;
https://www.cycle-frames.com/bicycle-...TTOM-BRACKETS/

Thank GrayJay. I have not choose the crank set yet. I just want to get a single speed for the front gear. I prefer work on the frame first and worry about the components later, but I am afraid that would be impossible. Mainly selecting the right BB/crank, and HT/Fork.

Most people prefer to do as you say, and it makes about as much sense as saying that one will work on the frame first and sort out the rider fit issues when the frame is done. I get that people don't want to commit to the extent of buying a bunch of stuff for a project they probably won't finish (most big projects are less than 1% completion rate, not sure what it is in bikes). But first, your parts need to fit, and with carbon, it doesn't cold form that well. second, for newbies (all been there), it can mean building a bike before one even really knows what goes where and how. Also, it is hard to get perfect specs, being able to measure a wheel with an inflated tire on it is a lot more accurate than any number of rules of thumb.