Hi all,

Sorry if this has come up before. I can't find it in the search.

I've crashed my Foil 20 so I'm buying a Scott Foil Premium and DA Di2 groupset to go with it.


The groupset i purchased comes with a standard external BB shell and i will need to purchase a BB86 BB that will work with the 7900 DA crankset (24mm O.D. spindle).

Shimano makes a BB86 adaptor for the DA7900 crankset but it looks like it's made out of plastic. It's called the BB91-B.
I've used a similar (plastic) BB86 adaptor for a Sram Red crank and it was crap.

My questions are,
1. Can anyone confirm that the BB91-B BB made from plastic?
2. Can anyone recommend a better BB that works on a BB86 BB shell and a DA7900 crankset?

thanks guys

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2012 Scott Foil Premium

1. Yes, it is made of plastic.

2. Better... Hard to tell, the Shimano is working flawlessly (but those BB86 BB may need loctite to prevent creaking). There are options from Enduro (XD-15), which is made of alu if I am correct. I think FSA is an option too.

I've run the Shimano pressfit (plastic) and the Endura ceramic on my BB86. The Enduro is lovely and smooth, and well made, but actually creaks a tad more than the Shimano, as the internal surfaces are metal.

The shimano product works well. It is made of plastic, so is your frame.

The problem with these BB30 and other type of huge BB bearings that you press into the shell is that they are very prone to massive creaking noises when the bike flexes. The old steel skinny-tubed bikes of the past never had as many issues with BB creaking due to flex of the BB/downtube because the older cartridge bearings were housed in a singular unit with cups that were pressed into the frame. These newer huge BB30 and other bottom brackets press the bearings right into the frame. Big difference.

Thanks for all the replies guys.

I've just realised that the TokenBB i have for my Sram Reds will work with the DA 7900 crank.
Sram cranksets has a tapered axle which go from 24mm on the drive side to 22mm on the non-drive side. The Token BB uses an alloy shim to make that reduction. If i don't use the alloy shim the BB will be 24mm on both side, which is what i need.

The biggest problem that i had when i used a plastic type BB on the Reds was serviceability. I found it really hard to remove without damaging it in one way or another.

If i had to buy one i would probably just go with the BB91-B just because it's cheap and may help with unwanted creaking.

Thanks to the weight of Di2 i've given up on being a true WW so no ceramic bearings for me.

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2012 Scott Foil Premium

Can you adjust the chainline with BB86 the same way you could with the older English-threaded BBs?

I'm not sure you can adjust them. Mine sits flush against the frame. You might be able to use spacers out side the BB too move the crank left or right but I would think you'd want the crank against the bearing.

not if you are running a singlespeed or fixed gear bike. You want the chainring to match up with the rear cog.