Am I understanding this BB90 stuff correctly?

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jspaceman
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by jspaceman

So Trek sent me a new black/blue Domane 6 frame & fork as a warranty replacement for my deceased Trek 5200. The frame arrived at my local Trek dealer last week and I picked it up. I wasn't going to build it up until the fall/winter, but it looks so nice that now I kind of got the urge to buy a Dura-Ace 9000 build kit for it and start riding it before the summer ends.

I'm a little confused about bottom bracket standards. I know Trek uses their own BB90 standard. The Domane came with a zip-lock bag that had the headset bearings and bottom bracket bearings in it. I take it that I will have to get the bearings pressed into the frame, they can't just be pushed in using your fingers? If I were to order a Dura-Ace 9000 build kit would I need any special adaptors to get the crank to fit into the BB? Or, once the bearings are pressed in, can I just slide the crank spindle into the BB, attach the left crank arm and it's done?

Thanks.

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grover
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by grover

Yes you will need to get the bearings pressed in. As they're going straight into the frame best find someone with the proper tools.

Assuming Trek sent you the Shimano bearing kit not the SRAM bearing kit then once the bearings are pressed in any straight 24mm spindle crankset (such as the DA 9000) will slide straight in, no adaptor required.

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FIJIGabe
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by FIJIGabe

If the bearings go in without being pressed (ie: you do it by hand), take the frame back to the shop and have them order the correct - oversized - bearings. This is mainly a problem with the older Madones, and the issue seems to have been cleared up. However, the bearings do need to be pressed in (you can make your own press, BTW, it isn't hard, and shouldn't cost more than $3, even in Canada).

The BB90 standard is a Shimano compatible standard. You need no adapters, the bearings are 24mm on both sides, and they aren't specific to one side or the other (you can put them in on either side, in either direction).

One piece of advice: if you plan on riding in the rain, or have bottles that sweat, you will want to head to a marine supply store buy MARINE GREASE. The reason for this is that the design of the BB will actually cause water to channel into the bearings. Even though Enduro does a good job of packing the bearings with grease, the grease isn't very water resistant, and will eventually wash off. Repacking is very easy. Using a very small screwdriver or pick, pry the bearing cover off and flush out the factory grease (I like to use WD-40 for this). Let the bearings sit for a couple of hours, to let the degreaser evaporate. Once that is done, you can put a small amount of grease on your palm, and push the bearing onto the grease, so it coats the inside of the bearing (you can YouTube "packing hub bearings" for an example of what I'm talking about). Once the bearings are nice and greased, replace the seals. It's a little messy, but works wonders to extend the life of the bearings.

jspaceman
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by jspaceman

Cool. Thanks for the tip.

I checked the BB bearings that came with the bike and they are for Shimano cranks.

If I wanted to get a SRAM build kit with a SRAM Red crank I take it I would need SRAM specific BB bearings? What type of SRAM crank would I get, GXP? BB30?

NiFTY
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by NiFTY

Yeah you need to replace the left hand (non drive side bearing) or get a shim kit for the non-driveside to fit a SRAM crank. You can only fit a GXP crank, The BB30 spindle is too wide and not long enough. The reason for this is BB90 is designed around a 24mm diameter spindle, shimano is 24mm the whole length. SRAM GXP crank width is 24mm at driveside, stepping down to 22mm at nondriveside.
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FIJIGabe
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by FIJIGabe

As NiFTY said, BB90 bottom brackets (and for that matter, BB92 and BB95) are not compatible with BB30 cranksets. Don't even try it.

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Tinea Pedis
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by Tinea Pedis

Sorry for the grave dig, but you can make GXP work? Just a 2mm spacer on the non drive-side is required to step it correctly?

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bikerjulio
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by bikerjulio

Tinea Pedis wrote:Sorry for the grave dig, but you can make GXP work? Just a 2mm spacer on the non drive-side is required to step it correctly?


I think you are misunderstanding GXP. Or perhaps it's the incorrect nomenclature.

The NDS bearing needs to be 22 mm ID. In the early days you would find a sleeve pressed into a 24 mm ID bearing to reduce it to 22 mm. Now I believe a different bearing is used. In either case the OD is the same and it should press right in.

Between the shoulder on the spindle and the NDS crank, the assembly grips the inner race and firmly locates the crankset preventing side-to-side movement.

GXP was invented in the age of threaded BB's, so the concept worked. It's not as good with a pressed-in bearing because side forces on the crank are working to loosen the NDS bearing. So it needs to be very firmly located.

Or use Shimano.
There's sometimes a buggy.
How many drivers does a buggy have?

One.

So let's just say I'm drivin' this buggy...
and if you fix your attitude you can ride along with me.

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Kayrehn
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by Kayrehn

No problem, I'm using Sram cranks on my Madone, you just need to use a wavy spacer that comes with sram specific bb90 kit.

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by Weenie


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