Originally Posted by
Bob Dopolina
When BB30 first went mainstream there was a lot of resistance from frame factories as it pushed the tolerances onto them. With BSA they could make the frame with the cups bonded in and then machine the threads in perfect alignment. With BB30 the placement in the mold had to be spot on and the amount of work that both could be done and was needed to be done was problematic.
I think PF30 is a step in the right direction but there are still production issue that didn't exist with BSA. The problem here is that these issues don't become apparent until after the bike is built and ridden.
Most issue are caught during production but, as with anything manufacturered, there will always be a small percent that fail I the field.
Speaking of manufacturing Bob, some of the ardent supporters of BB30 claim that part of its performance advantage over English threaded aka external bearing BB is...co-axiality of BB30 bores can be held tighter than the threading of the cups used in an English threaded BB. If you think about it, the bores themselves of insert molded English threaded cups first have to be held as tight as BB30 bores...but then you have to roll a thread into those English threaded cups. This increases tolerance and makes the argument for threadless BB30. As you say it always comes down to process...a manufacturing control plan and quality control. Same argument you make for good versus bad carbon. Process, process, process.
A further note. 'In theory' PF30 is good because it comes down to the 'cylindricity' of a 46mm ID hole in a carbon shell if this can be controlled to a tight tolerance. It could be argued that a PF30 hole can be controlled tighter then two insert molded bearing cups...but probably not a single one if both bores are shared. In the case of PF30 it really comes down to the 'process' of the crankset installer if subscribing to the use of adhesive to pressed in Delrin bushings. If pressing in Delrin bushings and NOT immediately installing the crank and adjusting preload...if you use say epoxy or Loctite, now the bushing bores centers are misaligned and bearing drag will be increased if the adhesive sets up prior to installing the crank which aligns cups and bearing bores. The corollary to this and counterpoint to using adhesive is....if you don't use adhesive and the bores are misaligned which they will be based upon a given tolerance....then the crank will align them and the bushings will dislodge at some level. This is precisely why Specialized changed their narrow PF30 what they call carbon OSBB installation procedure I linked...too many Delrin bushings lost their seat and support which causes them to squirm and lose their shape and fail...what happened to the OP's Foil.