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

[Nate Zukas]

No go on the Italian threading, 36mm diameter. English is smaller, just a little over 34mm. Use a shimano external BB set or the FSA external BB or pop out and switch the bearings from their cups if using a Sram external set up. It will take years of riding to wear out one of those bearings. I woudn't sweat it if its for yourself!
NATE

[steve garro]

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!

Ding-ding-ding-ding!!!!!
Thank You!
I was a pro mech for 14yrs before I ever thought I knew enough to try being a builder.
I personally can't imagine it anyother way.
Just add "race bikes as much as possible, ride everywhere, cover as many trails as physically possible, bike tour the world, and wear out bikes before you have an opinion on them."

But yeah - if it's yours rock it.
If not, chalk it up to experence & hang it on the wall.
Bet you never do that again, huh?
- Garro.

[Jim N]

I did this once and it's a mistake I won't be making again!

Now I check after drilling the vent holes, using a set of old BB cups marked "right" and "left", or just check that the drive-side is the normal thread (not that hard to remember).

I've been riding the bike with the backwards bottom bracket now for a couple of years. I did use Locktite and the cups so far haven't come loose.

[Tom Gagliardi]

Ding-ding-ding-ding!!!!!
But yeah - if it's yours rock it.
If not, chalk it up to experence & hang it on the wall.
Bet you never do that again, huh?
- Garro.

Yeh, I will not make this mistake again. I'm still blown away with my luck on the first six frames. 50/50 and I got lucky on all of them. I'm going to ride it. I already have two of the first six on the wall :-)

[Andrew R Stewart]

My still being a shop wrench (since 1973) influences my building. Most often in how a route cables and place braze ons. I am constantly dissappointed with what the big manufactures do for this. Cable loops far too short for their curves, rack mounts that are blocked by current brakes, fender eyelets that make the frame get scratched if you sandwich the stay with a couple of washers, and the list goes on. What ever I can do to make my bikes easier to set up, work better and be able to be worked on easier is my goal. Andy.

[Johan]

Just want to clarify that the reason cups are threaded the direction they are is "precession". It has nothing to do with what happens if the bearings freeze up.

[shand]

Now I check after drilling the vent holes, using a set of old BB cups marked "right" and "left"

I don't understand that ^^. If you check after drilling the vent holes, it's too late.

...or just check that the drive-side is the normal thread (not that hard to remember).

erm... are you sure about that??

[benson]

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.

Unless you are using Truvativ/SRAM GXP which has diffrrent left and right bearing IDs, or Campagnolo.

[benson]

I would probably braze up the threads with nickel-bronze and recut them.

[steve garro]

I would probably braze up the threads with nickel-bronze and recut them.

Having come from the thread cutting era i would love to sit back with a 12-pack & watch this process.
- Garro.

[zetroc]

KISS

Loctite the cups and ride it, or hang it up. Learn from it and keep going.

[Jim N]

I don't understand that ^^. If you check after drilling the vent holes, it's too late.

It's too late because you've wasted a bottom bracket shell, but you haven't built the whole thing yet.

erm... are you sure about that??

Oh, god...

[EricKeller]

this is a perfect job for thread milling, need to get that cnc machine in the basement running so I can fix old stripped bb shells.

[rellis]

It is possible to do a visual inspection of the threads and see which is left and right, just as it is with bb taps. Hold a tap vertically in front of you, which way do the threads slant up toward, left or right. Slant up to the right = right hand, slant up to the left = left hand threads. Every new mechanic we break in in the shop has to be able to get this right before they can touch any bb taps. The threads inside the bb shell are opposite from the taps in visual inspection. I use Paragon shells with the groove on the right face for most of the lugless frames and that does eliminate the issue.

[GrayJay]

If BB shell orientation goes wrong, you can always configure the bike as a singlespeed with the chain looped in a figure 8 between the cog and chainring. Pedal backwards to move forwards and the BB thread precession forces will again be in cosmic alignment.

[newellbt]

If single-speed, build a Left Hand Drive bicycle, use a GXP BB.

[back40]

I did the same thing exactly once. A little Loctite 242 on clean threads and it stayed in place no problem. As other have mentioned, I keep an old BB handy, thread in in part way then punch a small "D" on the shell so I never do it again.

[Will Outlaw]

Not for nothing, but kudos to the OP for posting this up so folks could learn from it.

#s 1, 2 and 3 have all been lugged so the orientation of the BB shells haven't been an issue, but I can assure you that I wouldn't have even thought about it on a non-lugged shell until I read this thread. It's now not a mistake I'll make in the future.

This place continues to be a kick-arse resource for even the most seemingly mundane details.

So, seriously, thanks. I'm smarter for it.

[MiWi]

Glad to hear I´m not the only "stupid" guy in this universe.

First frame lugged, no issue. Second frame TIG-welded, never spend a second thinking about BBS orientation, I just was lucky and didn´t even notice it.
On the third frame it happened. Couldn´t believe I was so dumb to never think about that....

I used Hollowtech bearings and mounted them with blue loctite. No problem, the bike is running for one year now.

Since Bike Nr. 4 I always mark the drive-side with a punched "d", too.
It´s also easy to check the thread direction by eye. I always double check both when I insert the seattube/BB assembly into the jig again. As you all said, I did this mistake once and I think it will never happen again.

[Jonathan]

My method, and this is not original, it's borrowed, is I stamp the bb shell with a number almost as the first step in the build. when I stamp the serial number, I install a bb into the bb shell to aid clamping into the vise and to keep the shell from deforming. I stamp the non drive side, it's easy to see which is which because of the cups. Using the stamp as the reference is easy after that.