Bottom bracket - ISO or JIS

lastpubrunner · Jan 21, 2010

I have a Stronglight 80 chainset (Double, NOT triple) for which I require a bottom bracket.

A well known bike shop has recommended that I fit either a 118mm ISO or a 115 JIS bb.

Which should I go for and why ?

Thank you for any comments/advice.

Elev12k · Jan 21, 2010

According to VeloBase they are for ISO

They are from the 80s, what to my knowledge means they are post Stronglight specific crankpuller era

pigman · Jan 21, 2010

I have successfully mixed and matched different cranks and axles. In the past some forum posters (might have been here or not??) recommended not to do this, so you takes your chance ...
The difference is that there is a slight difference to the taper angles. I'll give an example. On one mountain bike I have a shimano cartridge BB. I have tended to run this with a 42/53 campag chainset. When I switched to a shimano 42/53 chainset, the ring ended up touching the chainstay, so I needed a longer axle for it to work. What the shop is saying is use either, but recognise that with one, the chainset will slide on further, so get one with a longer axle.

hamster · Jan 22, 2010

The issue is not the taper angle (which is the same), but that ISO ones are thinner. So a fat Shimano (JIS) BB will have an ISO crank only just fitting (around 5mm)

IF you have a worn JIS crank, then fitting it onto the ISO BB can give it a new lease of life and works very well

My personal experience is that ISO cranks on JIS leads to misery. Whether you decide to fit is your own matter, but don't say you weren't warned!

Bottom bracket - ISO or JIS

lastpubrunner

Retro Guru

Elev12k

pigman

Old School Grand Master

hamster

Retro Wizard

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