Won't work. BB90 is for 24mm spindles, BB386 is for 30mm. There are adapters for BB30 frames but not vice versa.

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What's your CdA?

Bad news. It won't fit a BB90. Welcome to Trek's proprietary nightmare. (I've been there. I unloaded the Trek in order to use the components I wanted to use.)

Short answer, they won't fit, return the cranks.

However, if you are technically inclined and have no other option. There's the possibility that you can use these bearings to make them fit http://www.the-climb.net/...quad-bb90-part1.html . This will allow 30mm spindles to fit in your BB90 shell. I am not sure if the spindle will fit in width wise (a BB90 shell is wider than a 386evo shell). However the bearings are too small, not sealed, and won't last long. If none of this paragraph makes sense to you. Just return the cranks or sell them.

Thanks for those replies. I was hoping for some obscure way out but your answers confirm what I was thinking. I should get a full refund less postage for the return.

Why wouldn't you get a full refund?

I agree with the previous poster that even if there was an adaptor available you wouldn't want to use (bearing would be too small). You would be creating a constant maintenance and cost headache with the risk of permanently damaging the frame from the continual replacements.

I think so too Scott and so does my bike mechanic

 I think I should Jim and I believe I've got strong grounds. I was thinking that if they insist after lengthy argument they insist that I pay postage I might have to as a matter of commercial reality pay that. Alternatively since I got it at a hefty discount and its sold out I might be able to sell it locally. It might be quite expensive to ship it back to England from Australia.