JIS Crank ISO Spindle. Recipe for disaster?

[ljamesb]

Has anyone ever tried using a JIS taper crankset on an ISO tapered bottom bracket?

From my research into the actual physical dimensions of ISO and JIS spindles, I think that the two should be pretty interchangeable. If you use a JIS crank on ISO spindle, you need a spindle size about 4-4.5mm wider though. It seems that a lot of people on forums say it won't work, but I think most haven't tried it.

I need a new BB anyway, but also figured that while changing it, I want to save some weight on the part. My current BB is 350g. My Team Marin is hovering just above the 9kg mark and a lighter BB would get it under :twisted:. I'm considering these two which are a bargain for the weight:

This Neco one. I'm unsure yet whether this is JIS or ISO, but have messaged the seller to ask. 223g

This Tifosi one

There was one made by token which was 113mm JIS, but unfortunately it's been discontinued.

Is this a bad idea? If it helps, I don't plan to be removing the chainset very often at all. My crankset is a Deore LX M563 Triple.

 

[mattr]

If you have the the wrong combination the crank will pull all the way onto the spindle and bottom out the bolt before it goes tight. Then you'll kill the crank as it wobbles.

Worst case is *almost* tight enough. As you'll not realise until a lot of damage has been done.

(I have seen this done, or at least the aftermath. The bolt was torqued up hard against the end of the spindle, the crank flapped around like a flag....... Mate couldn't understand why tightening the bolt up didn't make the crank stop moving......)

 

[foz]

Why would you want to specifically buy an ISO BB for a JIS crank? Most BBs are JIS - it's only campagnolo that uses ISO for square taper, and they haven't made MTB parts for years. If it's not campagnolo and not specified as ISO, then it's 99.9% certain to be JIS.

 

[ljamesb]

Why would you want to specifically buy an ISO BB for a JIS crank? Most BBs are JIS - it's only campagnolo that uses ISO for square taper, and they haven't made MTB parts for years. If it's not campagnolo and not specified as ISO, then it's 99.9% certain to be JIS.

I obviously don't specifically want to use an ISO BB for JIS crank just for fun . Can't find any lightweight JIS type BB's at the size I need which aren't ludicrously expensive (i.e more expensive than a set of ISO cranks and new lightweight ISO BB combined).

Just wanting to know if anyone had any first hand experience mixing JIS cranks and ISO BB. I read through an absolutely massive email exchange between Sheldon Brown and others on the topic. It seemed as if anyone who had ever tried it for themselves had absolutely no problems. Many who had not tried it just assumed it would cause problems.

So basically just wanting to see what people's experience has been in actually doing this before I go out and buy a new part.

 

[ljamesb]

If you have the the wrong combination the crank will pull all the way onto the spindle and bottom out the bolt before it goes tight. Then you'll kill the crank as it wobbles.

Worst case is *almost* tight enough. As you'll not realise until a lot of damage has been done.

(I have seen this done, or at least the aftermath. The bolt was torqued up hard against the end of the spindle, the crank flapped around like a flag....... Mate couldn't understand why tightening the bolt up didn't make the crank stop moving......)

Do you think that was definitely because of ISO and JIS mixing? I had the same thing happen to me on my first racing bike, but it was just because of worn cranks. Very bizarre feeling I can tell you suddenly losing a crank arm while cycling through traffic!

 

[foz]

What size do you need? Token and shimano both still make decent BBs, or you could look for a decent used one on here, there are usually some about.

 

[mattr]

Do you think that was definitely because of ISO and JIS mixing?

Brand new build. With the wrong parts, so unlikely to be anything else.

 

[xxnick1975]

neco is made in Taiwan so certainly will be JIS

Love the fact this is all around saving 100 grams!

 

[ljamesb]

neco is made in Taiwan so certainly will be JIS

Love the fact this is all around saving 100 grams!

He he. It all adds up .

Found a newish Shimano UN55 BB (68-110 JIS) in my parts bin which I didn't know I had . Weighed it and it's 240g! The carbon ones I linked to (token, tifosi velospace, neco) are all about 230ish for 68-113ish size. Another example of supposedly ligher stuff not really being any lighter. I can live with that 10grams.

All sorted now! Cheers.