Bottom Bracket Advice

princdragoncok

Hi, it's time to replace my bottom bracket, but I've never done it before.. Can anyone confirm from this picture if I am dealing with an ISIS splined bottom bracket? and if so are they any major issues I may want to consider before replacing it myself..


I am about to purchase an ISIS compatible crank extractor and hopefully a suitable bb to match..
Can anyone tell me the best way to measure the size of the bb required? Is it as simple as measuring the distance from the inside of the left crank arm to the inside of the right arm and then the diameter of the entrance point of the bb into the crank arm? Any advice greatly appreciated, thanks

below is an example of potential bb
http://www.chainreactioncycles.com/Models.aspx?ModelID=23245

dev100

Google your bike specs and see what that comes up with or ring a dealer to find out size and then purchase off CRC

kona

If its shimano its ISIS all right.

The size of the BB is printed on the shell.
You need a special crank extractor to remove ISIS cranks it needs to have a larger head than one for removing a square taper.

Holyboy

kona wrote: »

If its shimano its ISIS all right.

The size of the BB is printed on the shell.
You need a special crank extractor to remove ISIS cranks it needs to have a larger head than one for removing a square taper.

Tut,tut,tut Kona, if it's Shimano it's Octolink,to the OP....if I were you I would consider upgrading to outboard bearings and a new chainset, it will cost a little bit more but will last a lot longer, ISIS and Octolink are just about a thing of the past as the bearings just don't last because the manufacturers had to make them smaller to allow for the over sized axle, in short it was all pants!!!
Invest in a Deore or Tiagra chainset,depending on your bike.

kona

Holyboy wrote: »

Tut,tut,tut Kona, if it's Shimano it's Octolink,to the OP....if I were you I would consider upgrading to outboard bearings and a new chainset, it will cost a little bit more but will last a lot longer, ISIS and Octolink are just about a thing of the past as the bearings just don't last because the manufacturers had to make them smaller to allow for the over sized axle, in short it was all pants!!!
Invest in a Deore or Tiagra chainset,depending on your bike.

I knew it didnt sound right!

doozerie

Holyboy wrote:

to the OP....if I were you I would consider upgrading to outboard bearings and a new chainset, it will cost a little bit more but will last a lot longer, ISIS and Octolink are just about a thing of the past as the bearings just don't last because the manufacturers had to make them smaller to allow for the over sized axle, in short it was all pants!!!

My experience of the ISIS BB's on my wife's hybrid is that you are doing well to get 2 years before the bearings are shot. I've tried different brands and the quality varied but about 2 years was the best.

By comparison I don't find the Octalink in my own MTB nearly as bad, My BB is currently biting the dust after, I'd guess, about 4 years of use. Still not great by comparison to some square-taper BB's that I'm still using after 10 years or more, but not too bad for as long as replacement BB's remain available.

If I were buying a chainset now I certainly wouldn't choose an ISIS or an Octalink one, but at the same time I'd be reluctant to take on the expense of buying a brand new chainset just to get rid of an Octalink one in particular.

doozerie

Forgot to mention that some BB's come with an adaptor (fancy name for a lump of metal with different diameter on each end) that allows you to use a regular extractor (for square-taper BB's) on ISIS and Octalink BB's. Think the one I have came with an FSA ISIS BB. It works very well and saves the expense of having to buy a dedicated extractor tool for ISIS/Octalink.

rob1891

w.r.t. measuring your bottom bracket. You need to know the shell width, which is the part of the frame your BB screws into, usually either 68mm or 73mm and the axle length, which is usually 108mm for a road double (off the top of my head). You won't be able to accurately measure the axle length without taking off the crank first. It might be documented in the original tech. specs. of your bike.

You will get a good lifetime from an SKF or Crankbrothers ISIS BB. It is a false economy to buy anything other than one of these, other manufacturers never solved the problem of small bearings in the ISIS BB and they wear out too fast.

Don't forget to check which tools you need to remove your old BB and install the new one.

rob1891

rob1891 wrote: »

w.r.t. measuring your bottom bracket. You need to know the shell width, which is the part of the frame your BB screws into, usually either 68mm or 73mm and the axle length, which is usually 108mm for a road double (off the top of my head). You won't be able to accurately measure the axle length without taking off the crank first. It might be documented in the original tech. specs. of your bike.

You will get a good lifetime from an SKF or Crankbrothers ISIS BB. It is a false economy to buy anything other than one of these, other manufacturers never solved the problem of small bearings in the ISIS BB and they wear out too fast.

Don't forget to check which tools you need to remove your old BB and install the new one.

Just saw your crank is a MTB triple. In that case the BB axle is probably 113mm if the shell is 68mm.

Holyboy

A deore chainset with outboard BB will cost about 95 eurons from a shop probably cheaper online and when the BB wears out in a few years theyre only about twenty quid! I think all the crank brothers ISIS BBs come with a five year warranty but they are expensive and dont come in many lengths,i think SKF have gotten around the problem by making the axle thinner where it fits through the bearings defeating the whole purpose but at least they last longer!