Bottom bracket sizes

ricktabor1

Hi,
I just bought a new chainset, 105 double (Octalink)...actually here's a link

http://www.chainreactioncycles.com/Mode ... delID=2647

I need to buy a bottom bracket. I've worked out that the BB width is 68mm but there three spindle length options: 113mm, 118mm and 121mm. Does anyone know what I need and why the different lengths?

I would understand two spindle lengths, one for a double and and for a triple maybe but the fact that there are three confuses me.

Can anyone help?

redvee

A double c/set needs a 109.5mm bb axle

http://techdocs.shimano.com/media/techd ... 612168.pdf

andyrr

Probably depends on the c'set, some doubles will need to be offset to the right more than others.
Only way for sure might be to get the old BB out and measure / check markings of that one. Alternative is to see if you can find a note of what your bike is normally fitted with : what is it ?
You can take the crank off and measure the axle width - bit tricky but do-able.

moonshine

if there is a BB in the frame, it will most likely have the BB width stamped on it.
the shimano octalink BB have. can you take it out?

a double 106 octalink BB is 109.5. I bought & changed one recently

keef66

http://www.chainreactioncycles.com/Mode ... odelID=906

so here's the matching BB. English thread, 109 for a double, 118 for a triple

moonshine

keef66 wrote:

http://www.chainreactioncycles.com/Models.aspx?ModelID=906

so here's the matching BB. English thread, 109 for a double, 118 for a triple

thats the very one..... 8)

ricktabor1

Thanks guys.

The problem i have with measuring the curent bottom bracket is that it has a hollowtechII triple mountain bike chainset XT on it.
The bike is a specialized tricross sport 2006. I bought the bike second hand and it had this chainset on it (put on by the previous owner). I want to put the XT chainset on my mountain bike and put a double on the Tricross sport.

Seems like the link to the one at CRC is the one to go for .

moonshine

ah.... i see.....

try wiggle and parkers too - i think i paid £15 for the 105 octalink 109.5mm english BB just before christmas - i canit

make sure it is the 105 BB (5500) you get as there is a mtb version (octalink V.2 iirc) which has sifferent spline depths.

check wikipedia octalink ref for more details.

the one on CRC previously identified is the correct one for a double road chainset.

ah there we go....
http://www.wiggle.co.uk/p/cycle/7/Shima ... 000000771/

ricktabor1

Thanks Moonshine - looks like that's the bad boy.

Cheaper in Wiggle than CRC, i'm surprised. Excellent stuff.