The old P2 or new P2. I have one of each.

I would suggest 150mm crank arms.

Old, 2008 I believe

I'm definitely open to giving that a try. Is it as simple as finding 150mm crank arms or do the various makers have different screws or measurements that would not be compatible with a cervelo?

What type of bottom bracket interface does your frame have?

You'll be looking for a Shimano 24mm, FSA Mega Exo, SRAM GXP, Rotor 3D+ or BB386 EVO. All of which will fit the BSA bottom bracket standard.

There are some others that will fit but those are the ones I've dealt with

Edit: You'll need the corresponding Bottom Bracket for those. I think your bike came with a MegaEXO. I had a 2009 that came with it.

I'm not sure how to tell.

BSA

English threaded.

You should be able to look at the frame's bottom bracket and tell what it is.

Thanks!! perfect!

This is a pretty good article about bottom bracket standards

https://www.bikeradar.com/...m-bracket-standards/

On Monday call Rotor at 801-393-4822, you'll probably get Joel, Tell him Ian Murray sent you. Explain what year, make, and model bike you have and that you want to get a set of 150mm cranks. He can provide the crank and bottom bracket needed. Now you still have 2 more choices to consider...
1) gearing - if you training and race is the most ridiculous steep mountains and all you want to do (care about) is keep a nice cadence on the climbs then you could consider a 50 tooth big ring and a 34 tooth small ring. But let's be honest this bike isn't really designed to do that sort of riding and most triathlon courses are relatively flat so... a 52/36 is far more logical especially considering it's a 650 bike. Since it's a 650 bike an argument can be made for a 52/39 if you are all about riding and racing on flat and you just LOVE any and all opportunities to go downhill at 40+mph. If you don't have a feel for any of this now then count the number of teeth in your current big ring, small ring, big cog, small cog and when you call Joel ask his advice (mention it's a 650 wheel size).
2) Power meter - if you're gonna do new cranks and you don't currently have power on the bike via pedals or hub then at the very least have the conversation with Joel about getting 150mm cranks with the rings you want/need with and without power - it'll all come down to budget.

After you get 'em get back to us all here and we can discuss changes you'll need to make in your seat height and handle bar elevation.

Ian

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Ian Murray
http://www.TriathlonTrainingSeries.com
I like the pursuit of mastery
Twitter - @TriCoachIan

Thanks Ian! I'll be sure to do that. I live in the swamp (southeast louisiana) and training for IMIN and IMTX, so both courses are not hilly. This was helpful as I have been pulling my hair out the last hour or two looking for 150mm cranks by the manufactures listed above. I do have vector pedals, so the power meter situation is already handled. Thanks again! This was really helpful!

In my 17 years of riding 650C bikes, I felt the 52/36 was the best gearing.

Riding a 52 on a 650C bike is like riding a 48 on a 700C bike. The 36 on a 650C bike is like a 33 on a 700C.