Bottom bracket fitting - modern content- photos added

OK - I know this is a retrobike forum but I guess that some of you guys also tinker with modern bikes and I need the benefit of your experience!

I have a custom ti frame that was made in China by XADC that I'm currently building up. Nice frame and bike is looking good.

However fitting components to the frame is exceedingly tight - I had every 27.2 seatpost out in the LBS before finding one that would fit.

And now I think may have the same problem with the bottom bracket which I can't get to screw into the frame. Now this may be my inexperience - it's the first time I've built a bike completely from scratch. The bottom bracket will engage with the threads on the fame and turn so far but then comes to a complete halt just as it feels like it should be going in nicely! I'm pretty certain I'm not cross threading it as I am starting it off by hand.

I've booked in into the LBS for later in the week to see if thery fare any better but I'd be interested to know if anyone else has had a similar experience.

Thanks

Carol

Its not a 68mm and you have a 73mm ??

Do you know the non drive side is left hand thread ?, if it's a Shimano BB the loose cup goes in the non drive side, a 73 will fit a 68 shell just the non drive cup will stick out 5mm.

There is a different threaded shell known as Italian (i think ?), dont know how this differs from the conventional threaded shell, dont think it's common either, mainly on older road bikes i think.

How many turns do you get before it becomes stiff? If a couple it may just need the threads chasing out at the LBS.

A dealer called me last week with a similar problem, which came from an "imported titanium" frame.

Wonder if it was someone with same brand of frame.

Seatpost tolerances can be very tight - but usually seatpost is a bit too small, not a big too big.¨

Interested to see what outcome of this one is.

Re: Bottom bracket fitting - modern content

CAS":2ho7lk5q said:

And now I think may have the same problem with the bottom bracket which I can't get to screw into the frame. Now this may be my inexperience - it's the first time I've built a bike completely from scratch. The bottom bracket will engage with the threads on the fame and turn so far but then comes to a complete halt just as it feels like it should be going in nicely! I'm pretty certain I'm not cross threading it as I am starting it off by hand.

Click to expand...

I had this problem with my Saracen Kili Ultra Ti. All I did to correct it was to run a BB thread cutting tool through it. I was amazed at how little metal it removed - just tiny flakes that looked like dust. I didn't think that it would be any different, but the BB went in perfectly after that.

I think it just boils down to tolerances. Mass produced, or cheap, frames usually have less accurate tolerances (either too tight or too loose) than the more expensive frames. You do get what you pay for.

stevek":1khmikbd said:

How many turns do you get before it becomes stiff? If a couple it may just need the threads chasing out at the LBS.

Click to expand...

I get several turns before it suddenly stiffens up.

Don't quote me, but you might want some advice from a person who works with ti.
Sure it'll be fine, but as it's a nice frame, it's worth asking first.

chris667":3mb4dr4u said:

Don't quote me, but you might want some advice from a person who works with ti.
Sure it'll be fine, but as it's a nice frame, it's worth asking first.

Click to expand...

Is there anyone on the forum who fits the bill?

jimi are you certain of that

rh is the left hand thread wind . tightens anticlockwise to the rear

use your thread gauge to check the shells threads . you do have a thread gauge dont you ?

cover the threads in the shell with grease so it looks smooth and butt the bb up against it and rotate the wrong way until it clcks so you know the threads are aligned , screw in until you feel the resistance and then unwind . look at the point were the grease was removed and where it still is and look for any sign of galling of the threads or any other possible reason it becomes difficult at that point

if its made in japan itl have the correct threads

if you cant see any reason why it wont go in take it to a lbs you trust and see if they will chase the threads for you but they might be reluctant as its ti