Converting from Low Profile Square Taper BB to Normal.

[Mickeyspinn]

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

It appears Shimano decided for alivio that year to do a different taper...so depending on how hard you bang it on or wind it up you won't really know where chainline will be. So yeah correct BB to suit new chainset and taper and off you go

 

[M_Chavez]

ISO has nothing to do with this.

It's JIS vs Shimmy's proprietary Low-profile JIS that is shorter than standard.

Why on earth they would use that on their low-end chainsets I do not know. Wow. Never underestimate the greed of bike manufacturers.
I'm eating my hat.

LP tapers are shorter, so regular cranks bottom out on an LP bb.
If you use a JIS bb with a JIS crank, you'll probably get the similar chainline as LP crank with LP BB?

Alternatively, look up the chainline in the spec docs for old and new chainsets.

 

[d8mok]

So we are talking about JIS Low profile as attached ? Never heard of it being a mtb rider and no mention of it other than dura-ace.

I suspect if it was used on Alivio 90% of bikes with those cranks are now using a normal JIS.

Anyway , I guess it’s somewhat irrelevant as really all you need to do now is find out what width spindle you need for your frame as the LX cranks will use a normal Bb. What frame is it?

 

[Lou Carpenter]

Yes I hadn't heard of low taper profiles before either until I tried putting the LX crankset onto the BB I had. It bottoms out straight away with no resistance. At the time I discovered this I did a google search and I think there are a few cranksets out there that use this low taper profile. Maybe it was a new "standard" that companies tried out on cheaper groupsets around that time? Sugino for example used it as well.

Anyway thanks all for the idea of matching chainlines, sadly I didn't get anywhere looking for service instructions for the Shimano LX FC-M570 cranks I'm trying to put on. I did however look in the frame manufacturers spec sheets and it seems for the higher groupsets they still specified the same length spindle. So I'll try that first. Thanks all.