SHIMANO BB-RS500 BSA-Innenlager (Lagerschalen) // Tiagra, Sora

Product Information

Other notes Analogous to BB30 above, but uses pressed cups (with identical bearings) for relaxed manufacturing tolerances OSBB (Road) First used on the brand’s SuperX ‘cross bike, the standard works in exactly the same way as BB30A, but sees the shell ballooned out to 83mm wide, improving tyre clearance and, supposedly, stiffness. How companies decide to go about that — and precisely what design features they want — is the real issue, because everyone seems to have their own ideas on how to achieve the same goals (less weight, more stiffness, and lower manufacturing costs). The road standard has an 86.5mm shell width (hence BB86) whilst the mountain bike standard has a 91.5mm shell width. A number of other shell widths may also exist, though they all use the same bearing cups.

Pros: Claims of improved sealing and durability, compatible with major BB standards, cross-compatibility for DUB cranksetsCranksets with 24 mm spindle diameter are the most versatile and, with the right BB, or adapters, can fit almost any frame. Compatibility Originally designed for 24mm spindles, but some BBs that fit a 30mm spindle are available

Crank designs that will fit: Standard 24mm external type (Shimano Hollowtech II, SRAM GXP, Campagnolo Ultratorque and Powertorque, FSA MegaExo, Race Face X-Type, etc), square taper, ISIS, BB386EVO, BB392EVO many others. Crucially external cups that fit 30mm spindles do exist. And here's where my problem is, I have no idea whether a BB I'm considering will fit the bike or not. Our] Hollowgram SiSL2 crank with SpideRing weighs 484g. By comparison, Dura-Ace 9000 weighs around 678g [we recorded 637g in our review – ed]. In addition to weight, another BB30 advantage is stiffness. By increasing the spindle diameter, you increase its resistance to twisting, which is where the bulk of the deflection in a crankset comes from. Roughly 70% of total deflection measured at the pedal comes from axle twist.” Because the crank arms are straighter, we can make them lighter than BB30 ones,” he says. “But because the BB386 EVO spindles are longer than BB30 ones, they aren’t as stiff. Total stiffness is not a measure of crank stiffness alone, though. When you factor in the stiffness gains from a wider shell, the overall stiffness will be highest when BB386 EVO frames meet BB386 EVO cranks.”Note: crankset for mounting on externally screwed in bearings, with a hollow axle 24 mm in diameter, is compatible whichever manufacturer produces it. So: Race Face X-type, FSA MegaEXO, Truvativ/SRAM Giga X Pipe (GXP), Campagnolo Ultra Torque – they are all compatible with Shimano Hollowtech II standard, so only Hollowtech II will be named in tables and remainder of the post. The idea is simple, by moving the bearings outboard of the shell, you can then use a much larger spindle. Currently, 24mm is the accepted norm compared to square-taper’s relatively minuscule 17mm diameter. If the frame has a press-fit BB shell (without threads, threadless), then you need quite expensive, special tools to install and remove/change BBs. If not using such tools (like a bearing press), bicycle frame can be damaged.

BB30’s larger 30mm-diameter spindle, compared to the standard 24mm size, allows the use of lighter alloy Immediate Media Other names PF41 (Hope – refers to BB shell diameter), PF24 (Chris King – refers to spindle diameter) So it’s mostly eyeballing and trial and error. Some very rough guide (what I often try with first) would be: Unfortunately, it’s difficult to know upfront which length will be the optimal choice. For all I could try, it still boils down to trial and error. I make sure to always have the entire range of lengths in the shop and am happy to do test-mounting to confirm, starting with the length I expect to be the optimal choice first.The need for a heavier metal interface looked like a limiting factor for mass-produced carbon bikes, but with a manufacturer like Trek on now on board (as mentioned above, its 2020 Domane features a T47 BB) that could all be about to change. If the importer->brand connection were that strong or forced then you'd expect Genesis to always be using all Shimano componenets. But for several years (not sure if they are still doing it) Genesis were punting out frames with press-fit BB's but with FSA cranksets plugged into them*, (likely also 50p cheaper OEM than using Shimano). PF30, OSBB, BB386EVO if it matches the spindle length, BB30A if the crankset has spacers on the left side Other notes OSBB for Specialized Road bikes appears to just be BB30. An older Pressfit 61x46mm BB appears to be obsolete OSBB (Mountain) This system is not without its issues however, with shells becoming oversized (due to wear) being a relatively common problem (leading Trek to release the very slightly oversized V2 bearings to compensate).

However Shimano advertise that SM-BBR60 & BB-R9100 use 'small ball bearings'. This is not necessarily a good thing, in that smaller bearings are weaker. However there are more of them. Still it would be reasonable to assume that the RS500 will be DIFFERENT in durability from the other two, but not necessarily worse. Specialized uses PF30 for its high-end mountain bike, confusingly also calling it OSBB though it is a different standard to the OSBB standard found on its road bike.

SHIMANO BB-RS500 BOTTOM BRACKET BSA *

As it stands, this new standard may just become the hot new thing among smaller manufacturers of metal bikes. Cons: Metal-on-metal interfaces can be prone to creaking; requires a separate bearing puller and press for service; requires high manufacturing tolerances; bearing seats can’t easily be faced post-manufacturing; not all BB30 cranks will fit Crank designs that will fit: BB386 EVO/BB392 EVO specific, standard 24mm external-type (can be adapted), BBRight, BB30 (axle width dependant), Other notes Matches the wide bearing spacing of a BSA external BB with a large 30mm spindle BB392EVO