Digger90 wrote: ↑
Wed Feb 21, 2018 8:04 pm
themidge wrote: ↑
Tue Feb 20, 2018 10:40 pm
BB30 is not an inherently poor design, it is a very good and efficient one if done properly. If both the bearings and the frame are manufactured properly so they are round, straight, etc. then BB30 is great. It's light, it's stiff, it has a low Q-factor. Buuut... If the bearings and the frame are not round or straight or of good quality then you'll get creaks and accelerated wear and all those things. It's all to do with manufacturing methods. Things like drilling from each side of the frame rather than all the way through from one side, or not using accurate molds for the shell, soft or not round bearings, all make BB30 a nightmare, when if those are all done properly, it's great.
tl;dr BB30 is great if you do it properly, and rubbish if it's not.
Raoul Leuscher has some great videos on the subject.
You're right - the engineering theory
is great- but the real-world application
of it has been a total and utter disaster. Frankly, Cannondale should hang their heads in shame for unleashing such a disaster on the world.
BB30 and all it's press-fit derivations have been one of the worst 'innovations' the cycling industry has foisted upon us consumers - and according to several people who've sampled production frames Cannondale has one of the poorest track records in the industry. (See the first Hambini video linked below - for just one example).
Cannondale's accountants (allegedly) invented press-fit BB's to cut manufacturing costs - and then Cannondale's Marketing dept 'sold' us all on the benefits of press fit. And there are a few advantages - larger BB shells mean wider axles, larger diameter axles, beefier DT/chainstay/ST areas etc. Also, supposedly gerater longevity (ha ha ha ha ha).
But in far too many cases manufacturers cut corners, don't manufacture with sufficient precision for tolerances, don't have sufficient QA testing, plus many other sins.
The result has been awful experiences of creaky, squeaky bottom brackets, many of which have worn out prematurely, some of which have ruined frames, and very, very few of which have ever delivered on the supoosed 'benefits'.
Hambini Engineering's and Leuscher Teknik's videos on this topic are very insightful regarding poor QA, poor fit, parallel misalignment, angular misalignment and a multitiude of other manufacturing issues with press-fit:
In bold above. Just to be clear for anybody here that buys into Hambini videos who is standing on a nickel because he makes bottom brackets....his analysis is downright limited and misleading and Leuscher Teknik who is a bit more credible but the devil is mired more in the details which he doesn't go into with his 'light gloss' videos...any good engineer who has worked in this field...I have....understand's that Hambini...a great circus name btw....does a dis-service with his pseudo analysis. It is highly flawed. His measurement technique and analysis doesn't take into account the entire tolerance stackup of not only BB30 bearing misalignment, but their true position in respective bores but most notably lack of accomodating bearing tolerances which by design account for bore misalignment and also crankspindle relative to bearing bore I.D's. Evaluating or comparing BB30 bore misalignment in a vacuum as he does is basically irresponsible.
I know this is well beyond the scope of this forum but in summary, the engineers that design the top frames from the top bike companies understand this. Are all bikes shipped from the top factories perfect? No. Are almost all buildable and ride well with proper BB set up? Absolutely. If not they should be returned to the mfr for replacement frame just like for any mfg defect like poor paint quality.
As to the picture shown with ovalized BB. If this came from the factory like this, than of course it is a rejected frame that should be returned for a replacement frame. But pictures like this posted on the internet are abused frames with unknown background. Reality is...if a BB30 bike has a seized bearing due to neglect or abuse....unlubricated bearing subjected to a lot of poor weather riding....the bearing will seize and can ovalize the BB bore. An ovalized bore is many times accompanied by insufficient bearing preload....a condition lost on many that set up BB30. In particular this is a common issue with Shimano cranks that are among my favorite because of their mechanical preload. If preload is misadjusted...either too tight or too loose and non angular contact bearings are used, and the bearings aren't lubricated properly to repel contamination from the environment...and even add it a higher watt rider, you have a perfect storm...a high side of tolerance BB30's will aggrevate this as well. So few understand the true dynamic at play. They only know, they end up with an ovalized BB and don't know why. Virtually all if not most can be avoided with proper set up and good bearing selection and adequate maintenance. This can happen even in degree over time.
PF30 is even more sensitive to this with carbon bores. So is BB90 what Trek makes who uses a metal bearing on a carbon bore and unserviced bearings...or common lack of bearing pre-load causes bearing motion in the bore and elongation to the bores aggrevated by poor abrasion resistance of carbon. BB30 is not only better in abrasion resistance of bores compared to BB90 but have better bearing bore alignment with CNC bore machining.
For those interested, there is a great level of misunderstanding about press fit on the web. The vast majority don't really understand the design, how its manufactured, what the engineers responsible for it evaluate to ensure its performance etc. Yes, some press fit designs are better than others. Even PF30 can now be tamed by conversion sleeves from the aftermarket or now integrated bearings into cups. Early PF30 bikes had separate delrin cups and bearings and those that worked on them or owned such a bike know what an unmitigated disaster they were...and yes a sad commentary that companies from the aftermarket, saw the flawed designs being promugated and foisted upon the bike riding public from top bike brands and these aftermarket companies created a better mousetrap...in effect, a highly engineered kluge...to bail out these top brand bike makers to make their flagship bicycles more reliable. A sad commentary indeed. But among all of press fit in all its permutations out there, BB30 is among the most reliable if set up properly with Loctite. And for those who don't like to glue metal bearings to metal bores to ensure 0 creaking with proper crank preload often missed, then the aftermarket has come forward yes again...companies like Wheel Mfg and Praxis with their sleeves with integrated bearings which work nicely as well. Of course, all needless when a threaded 68mm shell with threaded outboard cups with integrated bearings aka Shimano, works pretty flawlessly. In summary, pick your frameset of choice carefully. Pinarello and Specialized moved away from their version of PF30....Pinarello in their wisdom, all the way back to 68mm BSA for their most expensive Dogma bikes which are excellent and won the TdF now 3 times.. for a reason after too long.