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OK, building up a bike for a friend - an Open 0-1.0 (v light XC. carbon frame) which has a Bright bottom bracket (79mm wide, with the extra width on the non-drive side allows for not only more room for tires and shorter stays, but also better bracing of the left chainstay. The extra diameter, 42mm on the inside, allows for larger bearings and a 30mm bottom bracket spindle).
Have a Rotor 4630 bb installed.
Got a spare set of Race Face Turbine cranks, from an old Whyte 905 (boost wheels) ...
but when I fit the cranks, I must have >12mm of space to take up even with the preload collar adjusted fully out ... that's a lot of spacers!
Am I just mismatching stuff, or is there a technique with RF cranks?
Any help much appreciated!
What length is the crank axle? There are several widths, 134mm for older stuff, 136mm for boost and 143mm nominally for super boost (but also handy if you have a wide rear end. It is printed on the axlev in the middle. There are spacers that you use to take up the excess.
I dont know the specifics but if you think about it, your BB shell is 79mm, and the 4360 BB will add maybe 4mm to that. The old BB shell would be (effectively) 73mm, with 10mm each side min, so 93mm+ wide. you have 14mm+ to fill.
Unless Im missing something of course.
With the larger diameter BB do the bearings sit inside the 79mm width? That could account for some difference Vs a 73mm BB shell plus the thickness of two external BB cups (1cm each?).
That’s a roadie BB standard isn’t it? If so, I think you could swap in a different/shorter axle from, say, some Easton cranks. Assuming the chainring won’t then smash into the chainstay.
ISTR Cotic did it the other way round with an Easton crank on a RF axle to get the wider chain line for the Cascade.
I think the axle is 134mm or 136 - the Whyte it came off had boost wheel set, but 11 speed Shimano drive chain.
The bb bearings sit inside the 79mm width - compared to the Whyte frame that had a RF bb, bearings sitting outside the 79mm width, its total bb width was nearish 90mm compared to 80ish on the Open.
Is it OK to take up 10+mm of slack with spacers?
And yes, beginning to think it's a road equivalent bb - seems the Rotor 3D+ cranks fit, which seem to be road/gravel based...
Yes, 10mm of spacers isn’t a problem - I have 20mm on my fatbike as I run 120mm cranks with a 100mm BB shell. Start with the chain line measurement you need - if you go too narrow the chainring might not clear the chainstay. There is a guide on the RF website where it shows you all the BB shell width, chain line, spindle lengths, spacers needed etc. You have Cannondale (Magic Motorcycle) to thank for inboard bearings - a great idea when you machine things to a high tolerance, less so when you try to achieve precision fitting with general machining tolerances
Thanks all, becoming clearer!
Is this what I need?
https://www.wiggle.co.uk/race-face-cinch-bb30-pf30-conversion-kit
This would be better
many thanks, ordered
Is it definitely a 79mm BBright? I thought the last Open 0-1.0 I worked on had a 84mm BBright BB that only Rotor made cranks for at the time (another standard that never took off)
If the crank is too long spindle spacers are easy (as long as chain line is ok).
https://bikerumor.com/first-look-open-mountain-bike-1-0-29er-photod-weighed-ridden/
https://www.bikeradar.com/news/cervelo-boss-launches-open-mountain-bike-brand/