Converting from Low Profile Square Taper BB to Normal.

[Lou Carpenter]

Hello, I'm upgrading my crankset from a '99 Alivio, that uses the low profile square taper BB, to a '99 or '00 LX that uses the normal square taper profile. In an effort to avoid buying a few BB's to see what worked I was hoping someone may have some experience with this. Are the cranks going to sit a different distance out from the frame? I was thinking if I bought the same spindle length then with the different taper the LX crankset would end up further inboard and so may cause clearance issues with the frame. Any help would be appreciated, thanks.

 

[M_Chavez]

Are you sure '99 Alivio is low profile?..
I would have thought that Alivio would use the bog standard JIS of all things.

Sheldon says low-profile was a Dura-ace feature.

 

[Lou Carpenter]

Yes 100% certain.

 

[d8mok]

What model code Alivio are we talking about?

I’ve had many many sets of Alivio cranks whilst stripping bikes and all have used a normal JIS BB in varying lengths.

 

[M_Chavez]

Are you running an alivio crank on an old dura ace bb?
Or did the previous owner put an "Alivio" sticker over Dura ace cranksies to prevent them from getting nicked?

Just spitballing ideas here.

 

[Lou Carpenter]

Seeing as you don't believe me here are the Shimano datasheets for my MC-18 cranks.

 

[Mickeyspinn]

I think you'll have to mooch about on Shimano tech docs to find your chainline for current gear set up then with new cranks buy the corresponding BB to give that chainline.
I really wouldn't advise mashing different tapers together....that's square peg round hole malarky!

 

[d8mok]

I

Seeing as you don't believe me here are the Shimano datasheets for my MC-18 cranks.

I must be missing something. Which part are you referring to here?

I see a normal BB needed.

 

[Mickeyspinn]

I

I must be missing something. Which part are you referring to here?

I see a normal BB needed.

It's either iso or jis taper....contrary to some people not really compatible!

 

[d8mok]

It's either iso or jis taper....contrary to some people not really compatible!

Yes I understand about JIS and ISO. Shimano is JIS usually always as far as I’m aware?

So are we suggesting that Alivio need a shorter ISO Bb?

Maybe I’m heavy handed but I’d just bang a 110mm UN52 in it and be done. We are hardly talking about precision high tech machinery