New Bike: What frame size?
 

So I've pretty much decided that my next bike will be a Cervelo R3 with Rival which I plan to pick up later this week, but I'm not sure what frame size would fit me best.

I currently ride a 56cm Scott CR1 and have test rode a 54cm R3 (and a couple other bikes in 54 and 56). While I do notice a slight difference in fit between the 54's and 56's, they both feel pretty equal comfort wise (on the short test rides I've done at least).

I'm quite new to road cycling (and cycling in general), so I don't really know what "proper" cycling form is supposed to feel like so in terms of a proper fit, I can't tell which size is actually correct. When I asked various LBS's what size would fit me best (including when I got my CR1 fitted), they all just took a look at their generic sizing chart and said I was between sizes (and would lightly push whichever size they had in stock). I gave Competitive Cyclists' calculator a go, but other than top tube length, I really don't know how the numbers correlate with Cervelo's geometry chart. I am looking for a more aggressive bike/geometry as I may decide to give racing a try when/if I get in shape.

Here's my measurements and the calculations made with Competitive Cyclists' calculator:
http://img15.imageshack.us/img15/3329/ccfit.png

And the Cervelo R3's geometry chart for reference:
http://img35.imageshack.us/img35/2876/r3geo.png

If you can't tell by riding different sizes, How would we know?

If you are looking for a more aggressive geometry, size down, maybe longer stem. The handlebars will be lower compared to the seat than the larger model. Size up if you are looking for a more upright seating position at a more reasonable pace. Or get the one that just feels better. That should be the ultimate deciding factor. For a bike like that, an hour test ride should not be unreasonable for the shop to allow.

The CC fit calculator says your virtual TT length is 56.6 - 57cm for the first two fit styles. The virtual TT on the 56cm R3 is 56.4cm. That's the one you want. Overall height is bad to rely on, but it gives a good guestimate of where to start. If you are taller than 5'10" but less than 6" and have normal proportions, chances are you should be on a 56cm frame.

I am 5'10.5" with normal proportions and just recently sold a 2011 R3. It was 56cm and fit perfectly.

*edit* You might even be in between 56cm and 58cm. Why were you looking at a 54cm?

I think my proportions are a bit off as my inseam is only 28" and I'm slightly under 5'10". I did a google search to see what people around my height were riding and their inseams were more in the area of 30-33".

IMO go with the size down, as you can tweak with stem options and saddle setback to fine tune your fit. Initially, you can go with a slightly shorter stem with a touch of rise until you get your fitness and comfort on the bike, then go with the racier position to begin training.

Post a picture of your current bike - stem length, saddle setback, bar drop are of interest.

I think the Cervelo's run a teeny bit smaller than their ETT's suggest, because the seat tube angle is so slack.

Sight unseen, I would put you on the 56.

Out of curiosity, what's wrong with the Scott? Are the bars slammed & the stem flipped, and it's still too tall? (I just bought one)

Thanks for the input and sorry for the late response, been a bit busy. I was originally planning on picking up the bike today, but looks like I won't have the chance to do so for another week or two.

Nothing is particularly wrong with the Scott as far as I can tell, but do I really need a reason to buy more toys? :P

The reason I ask the question on frame size now is because I pretty much bought the Scott on a whim (they only had it in 56). I rode down to my LBS with my hybrid...and rode home on the Scott. However, now that I know I enjoy road cycling, I'd like to purchase a bike that I've put a bit more effort into selecting.

Here's a pic of my Scott just for reference (it's been pro-fitted):
*Excuse the dirty bar tape, I plan on changing the tape to a darker color when my new bars get delivered.
http://img28.imageshack.us/img28/6677/img1068d.jpg

Any reason why you can't do this with the Cervelo????

this is what i do as well. im also in between sizes and go with a the smaller size for a more aggressive fit. my long ride "comfort" bikes are a size up.

from the looks of your CR1 i would say go with a size smaller.

^^ maybe... but if he doesn't want more saddle-bar drop, a size smaller is going to yield a stack of spacers, especially since the R3s have shorter head tubes than the CR1s.