On ya bike - Bottom bracket help needed

[jondc]

During this lockdown and not needed to sue my bike on a daily basis, I have been doing some maintenance. The bike is a 2007 Giant Terrago. I am currently trying to change the crankset and bottom bracket (BB), as the original items was well worn. The original crankset has a IS-IS drive connection and the bottom bracket a 68mm shell and 118mm axle.

I saw a Shimano Deore LX FC-M571 crankset for sale, using the Octalink V2, so I order that as a replacement and, as the original BB was 118mm, I ordered a 118mm Octalink 2 BB.

However, on offering it up the chain-line seems out, it looks too far out but I have not fully pushed the crankset on, as I fear getting it off again if not right.

Was I wrong in ordering a like for like axle length and should I have gone for the 113mm?

Thanks in advance.

 

[tijuana taxi]

I did a lot of bike building around that time and used Octalink BB's when they were the latest greatest
Seem to remember V2 had longer splines than V1 so the chainset pushed further on the axle
BB model numbers were something like ES-50/51 and XT were ES-70/71, still got one of these on my old Stumpjumper
Later ones had plastic cups, be very careful putting them in and even more so getting them out
They tended to get literally welded in and had to be cut out in segments, horrible things

Its the chainset that determines the BB axle length, as a rule the 113mm gives a chainline of 47.5 on Octalink V2
Sometimes bikes with a large diameter seat tube needed a longer axle to give the correct chainline measurement
Any idea what the chainline distance was on your old set up?

 

[jondc]

Its the chainset that determines the BB axle length, as a rule the 113mm gives a chainline of 47.5 on Octalink V2
Sometimes bikes with a large diameter seat tube needed a longer axle to give the correct chainline measurement
Any idea what the chainline distance was on your old set up?

Unfortunately, due to inexperience, I did not measure this before stripping down and now no longer have the bits to put back and check.....
I have tried to g oog le the chainline but have not found the answer yet.

All I know is, the original bottom bracket was a FSA BB-8420 coupled with an FSA CK-300A DYNA Drive crankset.

 

[tijuana taxi]

If you have a larger diameter seat tube that will push your front mech out further I would try the 118mm
I used the 113mm on steel bikes like a Kona Explosif which have smaller diameter seat tubes
It helps to grease the splines to get the chainset on, but do not grease the BB cups if they are of the plastic type

 

[jondc]

If you have a larger diameter seat tube that will push your front mech out further I would try the 118mm
I used the 113mm on steel bikes like a Kona Explosif which have smaller diameter seat tubes
It helps to grease the splines to get the chainset on, but do not grease the BB cups if they are of the plastic type

Thanks for your help.

The seat post seems to be 30.9.

Comparing the exposed spline, protruding from the bottom bracket on the drive side, the original one protrudes less than the replacement Octalink, by a few mm. Also, whilst the crank will push on a bit further, there is a fair gap from the inner most chain ring to the frame, so can easily accommodate being closer.

Maybe I just order a 113mm and see......