Isis bottom bracket

[babyrasta]

Hi there everyone, I'm new around here, so I hope this is in the right section,
Could anyone recommend an Isis bottom bracket that is compatible with shimano cranks ?
Riding a Trek FX 7.5 and the BB has lost all lube and is making a horrible noise, it is a sealed unit so I just want to replace the whole thing but all the ones I can see online are not compatible with Shimano or dont specify, I dont really want to have to send it back so would appreciate some help.

Thanks for looking

 

[RecordAceFromNew]

Could anyone recommend an Isis bottom bracket that is compatible with shimano cranks ?

AFAIK no Shimano chainset can be used with an ISIS BB.

Shimano's splined BBs are called Octalink. There are two types (I and II and which are not interchangeable) of various spindle lengths and available in different models (ES 25/30/51 etc. with the higher the number the higher quality/lighter).

 

[Lee_M]

I think hes right

 

[Flossyrockstar]

Yep, he is, just ripped mine out and replaced chainset and bottom bracket with shimano ultegra hollowtech, I had the fsa carbon compact chainset on an Isis bb and it was complete pooh, within two months I had shave a few thou off the Lhs as the crank arm was flapping about in the breeze, within six months I was doing the same the the crank side .

 

[babyrasta]

AFAIK no Shimano chainset can be used with an ISIS BB.

Shimano's splined BBs are called Octalink. There are two types (I and II and which are not interchangeable) of various spindle lengths and available in different models (ES 25/30/51 etc. with the higher the number the higher quality/lighter).

 

[babyrasta]

So it seems I want Octalink, rather than Isis ? I was told by a mechanic the BB was an Isis fitting so I was going on that info, had a look online and they do seem similar !

 

[PatrickPending]

Nice photo here, should help......
http://www.lfgss.com/attachments/12674d1248323034-bbsx4-labeled.jpg?stc=1

 

[RecordAceFromNew]

So it seems I want Octalink, rather than Isis ? I was told by a mechanic the BB was an Isis fitting so I was going on that info, had a look online and they do seem similar !

If your chainset is Shimano and needs a splined BB then whatever you do make sure you get the correct Octalink type/version. A mix up there will damage the chainset irreparably.

 

[Blue Hills]

Anyone got any views on how good Isis bottom brackets are? I've had a certain amount of trouble with them on a Dahon Speed Pro - until I began to understand more about bottom brackets I thought it was a Dahon issue (they can be very,er, wobbly) but am wondering if it's the basic spec. Any truth in an idea I may have picked up from the internet somewhere that the bearings are smaller than many types and therefore wear faster?

 

[MontyVeda]

I've been running an ISIS BB for a decade... can't complain about it.

 

[Tanis8472]

According to Trek website, they are Square taper cranks and FSA Vero are also square taper.
So they will be JIS Square taper surely

 

[RecordAceFromNew]

Any truth in an idea I may have picked up from the internet somewhere that the bearings are smaller than many types and therefore wear faster?

This is a somewhat simplified history of what happened: traditional square tapers used 11 off 1/4" balls each side, which were reduced to 7 off ~4.5mm balls in the UNxx series cartridge BBs. But the balls had to be further reduced in size substantially when they started using larger hollow splined spindles (like what you have in ISIS and Octalinks) to save a few grams. Then to solve or partially solve that teeny tiny fast wearing bearing problem they moved the cups outboard (e.g. hollowtech, gxp etc.) to create more space for them, which created the new problem of left and right bearing cups being no longer rigidly connected by a perfectly manufactured stiff BB casing, and with the use of cartridge bearings must instead rely on the frame's BB shell being stiff, faces perfectly parallel, and cups impeccably installed etc. to avoid rapid wear.

Call me a cynic, but what better way can you devise to make your customers buy more BBs let alone expensive chainsets huh?

 

[Blue Hills]

Many thanks for the reply, but do I gather that you don't think ISIS systems are particularly weak?

 

[Deleted member 1258]

Anyone got any views on how good Isis bottom brackets are? I've had a certain amount of trouble with them on a Dahon Speed Pro - until I began to understand more about bottom brackets I thought it was a Dahon issue (they can be very,er, wobbly) but am wondering if it's the basic spec. Any truth in an idea I may have picked up from the internet somewhere that the bearings are smaller than many types and therefore wear faster?

I had ISIS on my fixed when I first brought it, The one that came with the bike lasted 11 months, the replacement lasted 10 months, I then changed the chainset and put in a UN54 square taper BB, that one is still sweet after more than three years use.

 

[RecordAceFromNew]

Many thanks for the reply, but do I gather that you don't think ISIS systems are particularly weak?

Fwiw I do believe ISIS BBs are generally not robust. Most have teeny tiny ball bearings.