View Full Version : BB - Which way round ?

Big Bunny
10-10-2014, 03:42 AM
Hi Folks,

I hope this is not a stupid question. :)

I am working on the BB for the Fox recumbent and have come to fabricating the BB mount. Problem is I took the BB apart months ago and now I have come to use it. Which way round does it go ?

If I orientate the BB frame such that the two holes where chain stays were mounted are towards me. The thread on the right tightens towards me.

The BB cartridge is threaded on one side, with a threaded plastic collar for the other.


The BB cartridge has "L <- D NL -> R" printed on it. But have have not been able to find what this means.

Does the BB fit as shown above ? But if I fit it this way, peddling forward is in effect the right way to unscrew the BB.

Don't want to fit this and then find I have fitted it wrong way around.

Thanks all,

10-10-2014, 04:31 AM
Best way to do sanity check is to compare it with another bike.
L and R means :cheesy: Left and Right (looking forward) and that's how you fit it - fixed (R) part on the right (with chainwheels) and the adjustable (L) part (just the crank) on the left.
Like so:

To confuse you totally L side has right hand thread and R side has left hand thread, so that both sides tighten "towards you".
Precession is only really applicable to pedal threads. For bottom bracket is only a small part of the load.

ps are you sure it is "plastic" on the left?

10-10-2014, 04:58 AM
It will only screw in one way round, and the L & R sides are annotated on the cartridge so it should be pretty easy to resolve.
Once you have determined which side of your BB that the fixed thread screws into mark your BB shell <-L & R-> to match the cartridge remove the cartridge and mount the BB to your boom.

As Bambuko says they rarely come undone even if put on the wrong-way round, especially with a bit of thread-set in the threads.

Hope the build goes OK.

10-10-2014, 04:58 AM
I always refit the fixed cup loosely(rh) so l know which way round it is
Regards Emma

10-10-2014, 05:36 AM
...It will only screw in one way round,..
Yes, but you can fit/weld bottom bracket shell either way...
Main load on the bottom bracket comes from the chain btw (hence BB threads tightening towards the rear of bike)

easiest way to remember is to observe that everything is arse about the face - i.e. RH side of the bike has LH thread (and LH side of the bike has RH thread)

10-10-2014, 07:50 AM
Not the greatest video, but does show how to remove and install a sealed bottom bracket. It looks to me like the way you're parts are pictured is the correct way for a Japanese-threaded bottom bracket. (Crank side threads are backassards and tighten by screwing left or CCW).

10-10-2014, 08:47 AM
...Crank side...
there are two cranks in a crankset on the bicycle :rolleyes4:
so which side is "crank side" in your book? :1eye:


10-10-2014, 09:18 AM
LOL. I don't know where that came from, probably my arse. :taz:
I meant the chain ring side, or chain wheel. Back OT, the diagram you JUST posted is perfect, and is the orientation I was referring to for the OP direction. (If I haven't missed something else). It looks to me that BigBunny has already positioned it correctly in his first post.

The other way could also work out, just not typical.

10-10-2014, 09:28 AM
The wrong way
But in this case once I fit the thread less bottom bracket assembly it does not matter
http://s8.postimg.org/md1sh2nqd/likethis.jpg (http://postimg.org/image/j678xg3a9/full/)
pic host (http://postimage.org/)

10-10-2014, 09:53 AM
...It looks to me that BigBunny has already positioned it correctly in his first post...

It depends on establishing beyond reasonable doubt the orientation of his picture.
It is entirely possible that this is what he has in mind? (the only argument against it is the description of bb screwing in towards the rider, which wouldn't apply in this case):


and if so, this is not the correct way :(

Having said so, as both you and Twinkle point out the chances are you would get away with it.

10-10-2014, 10:21 AM
Remember this thread where I thought churns70 had the chain set on the wrong side?



Most of us put the chain set on our RH crank side. It could work on the LH side like churn70's project. Just not as common. Pls tell us which side BB? Unfortunately, my error was to assume.

Neil B
10-10-2014, 02:26 PM
My wifes bike, which came from the tip, really threw me for a while, when I was refurbishing it. I was made with the bottom bracket the wrong way round. It hasn't come loose, so, does it really matter which way round it is?


10-10-2014, 02:58 PM
Most of the time no.
Especially if you allow it to fix itself with rust etc.
it might matter if you are very powerful, and on DF it might affect chainline position in relation to C/L of bike (not a concern on majority of recumbents, especially LWB).
3/4 of load on BB fixing comes from a chain pull hence the idea of using LH thread on chain side to lock it in (like RH thread on freewheel at the other end of chain pull)
On the other hand it is such a simple thing to take care of (unless one is having another senior moment...) :surprised:

10-11-2014, 01:00 AM
I have only used a sealed BB once. Cannot remember which way it went, and did not need to know which way it was meant to go--why? Because once the thing was screwed in tight there was no way it was going to come out on its own!!
Steve G

Big Bunny
10-11-2014, 03:10 PM
Thanks all for your replies, very much appreciated. The diagram was a great help and the You Tube link as well.

Onwards I go .. :)

10-11-2014, 08:01 PM
Hi Big Bunny,
If your name is Robin, PM me!
Steve G,