I have a new Merlin G2X Gravel frame, I'm trying to install an SM-BBR60 68mm bottom bracket. On the drivetrain side I'm following the arrow for tighten, which is anti-clockwise. After just a couple of turns it gets really tight that I'm concerned about damaging the thread, is this normal for it to be tight the first time fitted to new frame?
Fitting a bottom bracket to new frame
- Thread starter Alma
- Start date
-
- Tags
- bottom bracket fitting
Page may contain affiliate links. Please see terms for details.
Ming the Merciless
There is no mercy
- Location
- Inside my skull
Turn the opposite way till thread engages then turn back. You should be able to do it by hand most of the way. Threads may need a clean with a wire brush.
Is there thread lock on the cup threads ?
I have recently fitted a new BB to a new frame, like you I was concerned as it was tighter than anticipated, I cleaned everything, and made sure I wasn't cross threaded, it was still tighter than I was happy with, but went in using the spanner, it was a bottom twitching moment.
I have recently fitted a new BB to a new frame, like you I was concerned as it was tighter than anticipated, I cleaned everything, and made sure I wasn't cross threaded, it was still tighter than I was happy with, but went in using the spanner, it was a bottom twitching moment.
I like Skol
A Minging Manc...
- Location
- Sunny Ashton-under-Lyne
Probably some paint/overspray in the threads of the BB shell. Ideally running a tap of the correct size to chase out any muck would be the best option. I have a couple of old steel cups that I use as an alternative if I find it necessary to clean up the threads for any reason.
Cycleops
Legendary Member
- Location
- Accra, Ghana
I think you mean sphincter twitching moment
battered
Guru
I'm having a problem with a BB in my hybrid rebuild. It was a plastic one, square drive. Of course the thing refused to unscrew and had to be extracted by heat and cursing, which of course destroyed it. I did all this and cleaned up the threads before sending it for powder coating. It's back and I have again cleaned all the threads. The BB I have, from a MTB, is marked BO 1.37-24 tpi and is 110mm axle length. It has a conventional thread on the non drive side and the usual LH thread on the drive side. So does the frame. The new BB will go on 1 turn only and then sticks as if cross threaded. I don't think it is, I've done the usual trick of backing it in until you feel the thread start. Is there a different square drive standard? It's not Italian, it's LH thread drive side and both sides just seem as if they have the wrong thread pitch.
rogerzilla
Legendary Member
Is it an old Raleigh frameset?
battered
Guru
Looking at it there is a Stronglight JIS BB, it fits 68mm BBs (which I have) and has the same plastic cups that unscrew with the Shimano spline tool. Is the JIS identical to the BSA that I have (1.37 x 24 tpi) or is it slightly different? I'm also thinking that with plastic end cups I can wind it in and it will find its own thread without damaging the (ally, so harder) frame. Might be an option. The steel BB doesn't want to know, whereas on the MTB it winds in easily by hand.
battered
Guru
Aah! light dawns! French standard is 1.37 x 1mm pitch, ie 25.4. This would account for it starting and then jamming 1 turn in. I'll get a thread gauge on it. I haven't got a 24 tpi gauge, certainly have a 1mm though.
battered
Guru
We have a winner! Careful poking around in the frame with a thread gauge indicates 1mm pitch, which is why the 24 tpi BB won't fit. So, a French BB, in 1.37 x 1mm. Where the hell do I get one of *them*?
Edit - it's LH thread on drive side though, the original French was RH thread, no?
Edit 2 - LH thread drive side and 1.37" x 1mm pitch = Swiss standard.
If only there was an international standards organisation, you could call it ISO or some such.
Edit 3 - there is a threadless solution for damaged frames or those with weirdo threads. The threadless BB screws one side to the other and squeezes the frame between without touching the threads. The standard square taper ends poke out in the usual fashion. Seems the most expedient solution. Not expensive, seems £15 up gets one. Anyone used similar?
Edit - it's LH thread on drive side though, the original French was RH thread, no?
Edit 2 - LH thread drive side and 1.37" x 1mm pitch = Swiss standard.
If only there was an international standards organisation, you could call it ISO or some such.
Edit 3 - there is a threadless solution for damaged frames or those with weirdo threads. The threadless BB screws one side to the other and squeezes the frame between without touching the threads. The standard square taper ends poke out in the usual fashion. Seems the most expedient solution. Not expensive, seems £15 up gets one. Anyone used similar?
Last edited:
rogerzilla
Legendary Member
They were still using French threading 15 years ago? I thought it died in the 70s. If the frame's not too valuable, I'd run a set of BSC/ISO taps through it. Works fine for converting 26tpi Raleighs.
