beginner question about a bike size

Height is a poor indicator of bike fit, but it's very likely a 56cm P1 is going to be too large. I'm 5'9" and the closest P1 would be 54cm for my fit.

Now, that being said, bike fit is highly individual as you need to take in consideration not only body measurements (upper/lower body, arms, etc. etc.) but also flexibility, core strength, current/prior issues/injuries, athletic background/riding experience, type of rider you are, and all this before you even get to external factors such as distance, types of races, terrain you race/train in etc.

Then add that a 56cm from one brand can be vastly different than a 56cm from another brand, some times even between models... A 56cm can be about the same as a medium, a 54cm, a 53cm, a large, a 58cm, etc. etc. etc. etc.

Thanks I haven't rode it yet but I used to have a road bike about that size that was big for me and I rode it for a year. I could out both feet on the ground but again made do.

Sounds like a very bad idea... a road bike is a bit more flexible in fit than a tri bike... if it doesn't fit you well, you can end up quite a bit slower than on a well fitting road bike. Just keep that in mind since budget is important (wouldn't want you to waste the money)

Thanks I'm going to go ride it, he leaves an hr from me, and see how bad it is. I figured it's worth a shot to see.

At best you'll be forcing it. If be shocked if a 56 would fit you at 5'6" unless you have some really funky measurements. Being able to sit on it and reach the ground is a far cry from having a bike that fits.