Buy that bike. It should be a good fit. I am 5' 8" and I love my 51 cm P3. You are more normally proportioned than I. You will fit the bike even better as a result.

Greg is this your measured inseam or the size of pants you buy? Sorry to ask this but some newbies don't measure correctly and I don't know if your a newbie.
I ride a P3 size 54 It fits so good. I'm 5'10" my inseam is just short of 31" . I have some spacers between the stem and headset so I can still go lower.
If you can get to the bike and get fit on it ( even if you have it shipped and have to ship it back)

Greg- I am also 5' 8.5" with a 32" inseam. I spent a long time gathering fit information on the P3. I could have went with either the 51 or 52, but found a good deal on 51. It should be a good fit. One note, I had to use a stem with a good deal of rise to get a usable drop between the seat and aero bars.

sweet

I thought Dan always said that the length of the top tube is the most important. Instead of comparing jut inseam I would also compare torso length.

I have exactly the same height and inseam measurements as you do, but my LBS recommends the 54 (in mycase P2) either the 51 or 54 would fit depending on the position of the seat post. The key measurement was the top tube lenght and how you want to ride it, most of the time. I can give you more information later today as I go for the 1st fitting on the 54 this morning. I suspect your torso measurements are going to be more of a factor in sizing than inseam.

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Simple Simon
Where's the Fried Chicken??

Just got back from my first fitting session on a P2 54. I have no idea what the numbers are the owner of the LBS said ride and feel, make adjustments, dont worry about numbers. I followed advice. Aside from seat height, aerobar angle, the main issues we dealt with was fore and aft. There was approximately 3cm of spacers.

Initally set up with the post flipped forward, seat 2/3 back on the rails, then I asked for it to be flipped (backwards) where the seat was positioned foward on rails almost to the end of the rails.

I chose to ride it flipped forward (steeper) and seat 2/3 back wards on the rails, the first postion. The difference between the two positons with those seat placements was very marginal and I could have ridden both but found the more forward a little more comfortable, at least for now.

He also said dont tinker with it, ride it for a month, then tinker with position. So hopefully I can go for a second fitting tomorrow and ride it at the weekend. Cant wait!

As I said previously I am the same height and inseam measurements as you, and inital impression was the 54 fit good. But having said that I can see the 51 working too, possibly with the seat flipped backwards. I ride a 52 Trek (53 top tube, 75 angle, with a 12cm stem) I suspect that the position I have chosen is a bit less than a 53 (with a 90cm stem) but I dont have the numbers. If you have more questions email me.

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Simple Simon
Where's the Fried Chicken??

Thanks for the info. I was going to email you but you have no email in your profile.

I am definitely going to buy the frame. Besides, even if it did fit poorly, it's not too hard to sell a used P3!

I was planning on riding a slacker seat angle... maybe 75... so it sounds like the 51 will be ok for me. With the smaller frame I can probably move the seat forward, and my girlfriend, who has almost the same inseam, but a shorter torso, could ride it too! Hmm.. or do i want that? ;)

Hey G sent you an email.

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Simple Simon
Where's the Fried Chicken??