JIS Chinese Titanium Bottom Brackets

Canuckbiker

Old School Hero
I am lucky enough to own three sets of Race Face Turbine cranks. One set has a Race Face Turbine RS Bottom bracket with a 107mm spindle lenght, no surprise, it fits like a glove and chainline on my RockyMountain Vertex (68mm shell) is bang on. I also have a set of Turbines on my Cannondale M800 (1993) and have been using a 113mm spindle Syncros Titanium Bottom bracket. It works but not very well, the cranks are very far from the frame. I tried/tested a Shimano BB-UN300 (JIS) 107mm unit I have on a another bike and due to it's JIS standard square tapers it does not sit close to the frame like it would with an ISO standard unit (bit better than the 113mm unit though).
Now to my question noted in the title: what if I ordered a 103mm JIS Chinese titanium unit from the Bay? Very light, $60 CAD. Looking for opinions of mixing old school IOS cranks with JIS units more common today.
Also worth noting: I am using the Shimano BB-UN300 with ISO XTR M900 cranks on my sons bike with good results but it could sit closer to the frame. Also, are the Chinese Ti BBs comparable quality? Any try them?
Thanks for any help!!
 

Woz

Old School Grand Master
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I can't answer about the Chinese Ti BB, but the XTR cranks are most certainly JIS BTW.
 

Canuckbiker

Old School Hero
Are you 100% sure? Velobase identifies them as JIS while someone called "shivn" states "Incorrect Content, Those cranks has ISO BB, not JIS. I bought them and JIS shimano BB doesn't fit, but campy ISO fits perfectly"

I guess my big question is Race Face Turbines with JIS BB, I read somewhere else they are their own standard between ISO & JIS
 

sam_white

Retro Guru
I'd be surprised if any Shimano cranks were ISO, I don't recall ever seeing an ISO bottom bracket from Shimano that would also be needed in that case.
 

Tootyred

Senior Retro Guru
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Xtr are jis. Xtr on iso your more likely to bottom the crank out especially with wear, but on a new taper, it may end up closer as there is less contact ( in theory) internally due to ( again in theory) a smaller far end. Ie the same torque would pull it on further as there is less interruption.

Race face is neither jis or iso. They had their own standard between the 2! Useful hey!

In theory, in a new socket (very important as wear, fitting torque, pattern fitted to and grease all effect the longterm fit) would mean a jis bb would move the chainset outwards slightly.

Its very confusing, as raceface specify in their older instructions fitting to jis shimano bb's......although they dont actually fit exactly.

Its why they produced their own bbs, and why yours fits perfectly with one, but not on others.

I only know because i went through this entire saga with a set of prodigy a few years back.

To get the right chainline i ended up with 107 jis, but then they were worn inside by fitting to repeated jis bbs.
 

Canuckbiker

Old School Hero
Thanks all for the info everyone. I've been a bike geek since the 80s and never was aware of the JIS vs ISO question until recently.

Ended up pulling the trigger and ordered a Chinese Ti unit 103mm long and it just clears everything so best chainline possible I figure using Race Face Turbines. Did notice a slight amount of play but very minor, no way to remove it with the design so I'll keep an eye on it. 159g so super light and only $65CAD.
I'll report back on quality/durability if anyone is interested
20210623_020631850_iOS.jpg
20210623_020639241_iOS.jpg
 

Canuckbiker

Old School Hero
Update, I cannot recommend this BB. That is unless you are okay with spending a lot of time modifying it so it works the way it should. I have only done a couple rides on mine so can't comment on long term durability, it's held up so far, yup, very light weight.
I mentioned mine had a bit of play but minimal, I don't notice anything while riding (so far). I'm just finished a 93' M800 restoration for my 17 year nephew (he noticed my sons rigid Cannondale and realized how great bikes of this era can be). He also wanted to shave as much weight off the stock 25.5lb as I could without breaking the bank, I got it down 2lb, I purchased one of these Chinese Titanium units for his build as it is a very good gram loss vs dollars spent ratio.

This second unit I bought has a lot more play. There is no way to adjust bearing play with this design. The bottom bracket shell has to be bang on and the BB has be match exactly, bad design. I spend a fair bit of time fashioning a fender washer to fit inside the non-drive side cup to take up the slack being careful it does not introduce any drag, couldn't tighten the cup all the way down so used some blue lock tite. Not the best but should hold up (hopefully).

I think the modern Shimano BB-UN300 is a safer bet, still much lighter than the older Shimano units (around 260g)
 
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