Originally Posted by
seb1466
A wise old Owl once told me:
AC bearings can last longer in BB30 applications because they have higher load ratings than radial ball bearings. This is down to the filling method of the radial balls (look up Conrad filling method). So an AC of the same size will have more balls and a higher load rating than a radial bearing. So basically nothing to do with axial loads and/or preload. AC has slight rigidity benefit too as the 'effective centres' of the bearing are further apart. Forces are applied to the bearing where a line drawn through the contact angle bisects the axle centreline. However AC is only effective with fixed mechanical adjustment (e.g.screw thread). If your BB is preloading the bearings with a wavy spring then it wont be an AC under a radial load..
Originally Posted by
WizardOfBoz
Bikes do not require 0.002mm runout. Even if you are racing. They do require fairly low runout and to get this for AC bearings is not hard. We successfully preloaded AC bearings in decades of very fine BB and wheel AC bearings. Think Dura Ace and Campagnolo. Think Eddy Merckx. I have my old paramount BB from nearly 40 years ago and it's pristine.
AC bearings are much easier to adjust and more tolerant of improper preload than deep groove radials. AC bearings are MEANT to resist angular force. The design of DGR bearings make them very susceptible to wear if they experience side loads (or too-high a preload).
ACs are better bearings for BB service, and are easier to adjust and are more tolerate of improper adjustment that DGRs. Look at Enduro's warranty record. I believe them.
Sor forgive my ignorance as I try to understand the angular contact points being made in above two posts. Is the point of the bold text piece of the [MENTION=507890]seb1466[/MENTION] post that I can use AC bearings with cranks that don't have mechanical preload adjustment, because as [MENTION=419049]WizardOfBoz[/MENTION] points out, preload needs are minimal anyway and AC bearings are tolerant of misalignments, but I will lose the advantage that AC bearings offer in terms of higher load ratings? I am running a pristine 80s Suntour BB on my Paramount and am perfectly comfortable adjusting preload via the adjustable cup because I can feel changes in spindle play and ball bearing movement. With my SRAM cranks, there is no such mechanical adjuster (There is an adjusting collar but I can’t say that it effects bearing load in any way).