Built Frame with Bottom Bracket Backwards - Is it ok to thread cups backwards?

As a new frame builder, with no formal training, I've learned some lessons the hard way. I'm just finishing frame #7 and went to thread the BB cups in and realized the BB was backwards. What is really mind blowing is that up to this point I've never considered which way the BB should go...just put it in the jig and built the frame. I can't believe I just got lucky on the first 6 frames, but somehow they all ended up with BB in the right direction.

OK, what should I do? Just reverse the side on the BB cups and tread in the reverse direction? Try to reverse tap the threads (seams like a dumb idea)?

Is it yours? Just run it. Normal threads are made to loosen if the bearings seize. If your BB goes yours will tighten. If its for a paying customer you need to start over.

You could also tap it Italian.

Thanks for going easy on my stupidity. No paying customers on frame #7. I think I'll take your advice and just run it (it's for me).

What would be involved with tapping it Italian?

What direction is the BB supposed to be? I'm about to start my first build and have been thinking about that exact same thing but too embarrassed to ask.

Depending on who manufactured your BB shell, it may have an identifying marking telling you which side is the left-hand-thread side (if English threaded.)

example: www.paragonmachineworks.com - BB00011500x685mm

I would recommend against tapping it Italian. Assuming you're running an external bearing bottom bracket, it shouldn't matter at all as far as crankset alignment. If you're running square taper/cartridge, you'll need to make sure it's a symmetrical BB so it doesn't screw up your chainline.

This is definitely one of those 'measure 3 times, cut once' things. I actually physically thread a BB cup into the shell to verify thread direction, then mark the shell.

Sean, this only applies to lugless; the shell should be oriented so that the lefty-tighty cup is on the drive side assuming british threading.

Quote:

---

Originally Posted by mjbabcock

Is it yours? Just run it. Normal threads are made to loosen if the bearings seize.

---

The normal explanation given is that the thread directions prevent the cups loosening due to precessive forces.

In this situation, blue loctite is your friend.

Quote:

---

Originally Posted by echelon_john

Sean, this only applies to lugless; the shell should be oriented so that the lefty-tighty cup is on the drive side assuming british threading.

---

Thanks. I purchased the bb shells from Nova and there are no identifying marks.

Quote:

---

Originally Posted by seankanary

What direction is the BB supposed to be?

---

The easy mnemonic is BBBB: For British thread, Bottom Bracket is Backwards. Right hand side is left hand thread (and vice versa).

I just think about turning the cups towards the axle. I guess there are a lot of ways to remember it though.

Quote:

---

Originally Posted by thomasauction

Thanks for going easy on my stupidity. No paying customers on frame #7. I think I'll take your advice and just run it (it's for me).

---

You will not be able to use a SRAM GXP BB, though. The non-driveside bearing is smaller diameter.

Outstanding, Thanks fellas =)

--Sorry to hijack your thread Thomas.

"I guess there are a lot of ways to remember it though." < The threading is the opposite of the pedals.


"You could also tap it Italian." < Italian Cups are larger so if you try to retap an english cup italian it takes out too much material and could destroy the cup entirely.
Italian shells are larger diameter, all other size cups fall right through, threads will not engage. - sheldon brown

I would recommend working in a high volume bike shop as a mechanic for a year or two at least. It will get you acquainted with the mechanics of bicycles and help you answer alot of questions that you might come up with when building a bike. not to mention you will likely test ride a few hundred bikes at least, and that will get you familiar with design versus handling issues. Plus you can get real familiar with components without paying for them.

Good luck building!

This is why I have a drive side bottom bracket cup on hand that lives with my frame jig. I check this constantly so it's oriented correctly. Paragon's bb's have a stepped groove on the drive side (another check point and why I only use Paragon's bottom brackets).

that's smart. i'm picturing it hanging on a silver chain that you also fabricated! ; )

Quote:

---

Originally Posted by fortyfour

This is why I have a drive side bottom bracket cup on hand that lives with my frame jig. I check this constantly so it's oriented correctly. Paragon's bb's have a stepped groove on the drive side (another check point and why I only use Paragon's bottom brackets).

---

Quote:

---

Originally Posted by seankanary

Thanks. I purchased the bb shells from Nova and there are no identifying marks.

---

I am currently building with a Nova BB shell. The drive-side (left-hand thread) has the inside diameter cut larger at the outer most edge before the threads start. That is their identifying mark.

I've had Nova shells with the other side cut larger. I think keeping a cup on hand to check and confirm is the best route.

The other thing I've starter doing with lugless is confirming the orientation of the shell, then immediately drilling the vent holes for the ST, DT and chainstays. Then you've got the holes there to idiot proof multiple fitups and eventual brazing.

Quote:

---

Originally Posted by RyanHeller

I am currently building with a Nova BB shell. The drive-side (left-hand thread) has the inside diameter cut larger at the outer most edge before the threads start. That is their identifying mark.

---

Quote:

---

Originally Posted by fortyfour

This is why I have a drive side bottom bracket cup on hand that lives with my frame jig. I check this constantly so it's oriented correctly. Paragon's bb's have a stepped groove on the drive side (another check point and why I only use Paragon's bottom brackets).

---

I had a scare on my first frame (woke up in the middle of the night and ran out to the garage to check the bb shell) so I set up my fixture to use a modified steel bb cup to center the drive side of the shell on the end of my bb post.

Attachment 51211

I built a frame this way by accident once and found that like someone up thread said, blue locate (or red) is your friend. Also with square taper bb, a phil in my case, once the bearings started to fail there was basically no keeping the cups tight for more than about 20 minutes of riding. I still ride that bike regularly though and with good bearings in the bb it hasn't been an issue even when it was set up as a single speed.