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9

Carbon is the dominant frame material in performance bicycles. You can't thread carbon. There are two ways to get bottom bracket cups into a carbon frame: bond (industrial-strength glue) an alloy sleeve into the shell, or use a press-fit system. You are potentially adding several manufacturing steps by adding a threaded sleeve to a carbon frame, and the ...


4

The reason I have always heard justifying PF bearings vs outboard bearings is that PF bearings allow the frame to be wider and stiffer in the BB area without increasing the Q-factor of the bicycle. PF is also lighter because it does not require a metal threaded insert. I have two bikes with PF bearings and I suspect PF frames are a lot like gnocci. When ...


4

Money. Threading holes is a process that has to happen during manufacturing. Both sides have to be concentric and parallel, and the taps used to make the threads have to be pretty good, so they wear fast. By comparison, the bottom bracket holes on a carbon fibre frame can be made in the layup process, and (in theory) should come out the right size ...


4

BSA refers to the diameter and thread pitch of the threaded bottom bracket shell in the frame. Square Taper and ISIS refer to the crank interfaces on the ends of the axle of cartridge bottom brackets (that fit in BSA threader shells). See this Sheldon Brown page for info on cartridge bottom brackets (pictures near the bottom). A quick look at the Cyclone ...


3

The spacing is the only difference across the SRAM/TRUVATIV GXP line of BB's, so yes, you can use the 68/73mm left/right cup set on your frame. Just reuse the center seal/spacer from your existing BB, especially if you're riding a lot in the winter or rain. Funny enough I've seen cheaper prices for the less widely used 100mm than the far more common 68/73 ...


2

The parameters involved are as follows: Your frame’s bottom bracket shell, which is BSA threaded. The spindle type, which is where you ran into trouble. Shimano specifies a 24mm diameter spindle. SRAM’s GXP is a 24mm spindle that tapers to 22mm on the left crank. I don’t know if there’s a substantive reason for this, or if it’s just to avoid any patents ...


2

BSA or 'English' or ISO standard refers to the the thread in the bottom bracket shell (1.37in x 24 TPI). Both cartridge and external bearings fit in this these shell threads. There are several standards shell widths: 68mm for road bikes, 73mm or 83mm for mountain bikes. There is no such thing as a bottom bracket chainline offset chart. Each bottom bracket ...


1

With threaded bearings the actual bearings first have to be pressed into the threaded aluminum cups. They are then screwed into the frame. This is quite unusual, usually bearings are directly pressed into wherever they are needed. However, for metal frames this is more or less okay. You have the additional weight of the aluminium cups, with the advantage ...


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In the first picture it looks like the holes are simply machined to decrease the weight of the adapter without compromising strength. My only concern with the frame and adapter would be tolerances because you wouldn't want it to fit too loose. The second picture definitely looks like a bb30 frame but without calipers it's impossible to know the diameter and ...


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