Here’s the problem:
Just installed some Superbe Pro track cranks on one of those 109mm “ProType” sealed bottom brackets. These are marketed as ISO taper, to suit Sugino 75 cranks etc.
Both crank arms now sit 4.5mm further outboard than they should. I have a 46.5mm chainline instead of 42. No good. My chain is making some unhappy noises.
Must be the old JIS vs ISO mixup, you say. Not so fast, me wee laddy.
The actual taper type of Superbe Pro parts is shrouded in some mystery, but regardless there’s still something fishy going on.
Assuming the new BB is in fact ISO taper:
If the SP cranks are ISO, they should fit perfectly on the ProType BB.
If the SP cranks are JIS, they should sit 4.5mm further in than usual. Not so - they sit further out.
So, either:
the cranks are actually an even smaller size taper than ISO - more ISO than ISO? I’d be surprised.
or
the ProType BB is in fact JIS (a logical explanation). In this case I should probably get in touch with Ben’s Cycles.
Does anyone have any light to shed on this? I’m interested in whether anyone else has used the ProType BB and checked their chainline.
Also interested in what BBs people are using for SP cranks. I have another set on a matching SP BB that give a standard 42mm, but don’t really want to unbolt them right now to test different options.
SP is closer to ISO than JIS. Hence you can run SP on sugino 75s or campy and it’ll sit fine. For the best fit you need a superbe BB/Spindle as it has a different taper. I’m just waiting for my superbe BB to arrive and then I can take some pics of their comparison for you.
From lots of reading/googling JIS and ISO run 2degree tapers but at different parts, superbe is supposedly 1.8. I’ll try to confirm all these figures in the next day or so as its been something I’m really keen on solving.
I’m now pretty sure the problem lies (mostly) with the bottom bracket.
I have two friends using the 109mm Protype BB. (I did a bulk order from Ben’s.) One has fitted Sugino Grand Mightys, the other Dura Ace 7600. These are both ISO taper.
Both have a ended up with a chainline 3mm too far out. So it looks to me like the BB isn’t actually ISO, but part way between ISO and JIS.
The problem is made worse with Superbe Pro cranks, since as mr horse says, they seem to be very close to ISO, but probably 1.8 degrees instead of 2.
Anyone else using a Protype BB?
I’d like to be sure before I tell Ben’s their products aren’t quite what they’re labelled.
hey a little off-topic but you obviously know what you’re talking about.
i’m having significant amounts of difficulty working out whether Dura Ace 7600 cranks are officially ISO.
i fitted my DA cranks to a Sugino 75 Super Lap BB (definitely ISO) and they were further out than they should’ve been, resulting in not great chainline. (they were installed by Shifter so the job was done properly)
Jams - you’d think it’d be straightforward with something as common as Dura Ace, but it’s not.
I did a whole lot of internet searching for my mate’s bike with the 7600s, and found people out there using either JIS or ISO. Since the difference is so small, people often often use the wrong taper without ever realising. We went for the ISO BB, and found them to be off by 3mm, but the Sugino Grand Mightys were the same, so who knows.
I’d like to test some of these cranks with a Hatta BB, since that’s what most Keirin bikes with Dura Ace/Superbe Pro use, but that’s a very expensive test.
I have a hunch that there are actually shades of grey between ISO and JIS, with Sugino operating at either end of the spectrum, and Shimano/Hatta maybe somewhere in between.
I guess the bottom line is to match like with like.
yeah, it’s kinda ridiculous when half the people/forums are saying dura ace is ISO and the other half is saying JIS. wonder if anyone’s ever called Shimano to find out?
Haha, yeah, i’d like to see if S75 cranks will work out to be the right chainline but like you said, these experiments are expensive…
just get some white board marker and paint the sides of the taper and then put your cranks on. depending on the engagement you’ll figure out if you have the right taper or not. If you put superbe on JIS you’ll only get engagement at the top. if you put superbe iso there’s better engagement. and iso on iso is pretty much cleans off the marker. I haven’t got any JIS cranks so can’t do the check on my SR Sakae spindle.
On the cranks side of things…you probably know this already but all NJS stamped cranks – be it Sugino/SuperbePro/DuraAce/Campy are absolutely ISO…everything else out of Japan is JIS…and likewise with BBs.
In reference to the Protype ISO BB in question, I know the Bencycle specifications indicate that everything measures up equally, but in reality my guess is they don’t due to abnormalities in production cost/quality of said part and the fact its being matched with NJS specific cranks.
I’m not in any way suggesting the NJS component is of superior quality, but the production quality of the BB spindle must surely be questioned.
Just my 2 cents and it may be an oversight on my behalf.
fusen - I agree. I’d expect anything with an NJS stamp to conform to a standard, that’s the whole point. For that reason I’ve always thought the mysterious “Unique Superbe Pro taper” was a myth based on marketing in the 1980s. Still, Suntour did some funny stuff sometimes, due to the lower production runs compared to the bigger companies. The ProType BB is definitely not quite ISO though.
^ I think you’re right - all 3 of the bottom brackets I bought must have come from a bad batch, with a tiny increase in the spindle width.
I fixed the problem today by borrowing a friend’s adjustable Miche BB. 107mm, shifted 1mm to the right, was perfect.
I’m sure a 109mm spindle with actual ISO taper would have been fine too. As far as I could tell, the Suntour cranks did seem to suit ISO taper.
I guess it makes sense for a tiny fraction of a millimetre difference, on a 2 degree pitch, to cause a 3 or 4mm chain offset. It sucks, because that was enough for my chain to struggle to land on the chainring.
i’m looking at getting a new bb for a pair of 75’s i have too. cup and cone is no good for a work bike so i’m thinking phil wood but looking at them they don’t seem to have ISO only JIS. they advertise campy bb’s so i’m assuming they are ISO? true?
You can’t go wrong with a Phil bottom bracket. Like the Miche one, the bottom bracket cups don’t clamp on the outside of the shell, they just sit inside, so you can adjust them to anywhere you want. So you can remove that half mm difference and achieve Ultimate Chainline Nirvana.
Unlike the Miche one, that BB will probably last for a thousand years. Or something.
)