springs

Specialized does not spec stack and reach on their web site. Does anyone have measurements for these two dimensions for the Roubaix 51 and/or 54?

tia,
springs

Unagidon

You can get an approximation of reach by looking at a company that publishes reach (trek, cervelo), then compare a similar sized bike, looking at the top tube numbers. For each degree of steeper angle vs the comparison bike, that approximates to 1cm longer top tube. Then use the reach and the top tube number you have - do the division and use that as a ratio to multiply the guesstimated top tube length and voilà - a reasonably close reach number.

Re specialized, in general they have pretty long reach numbers on their small bikes due to really steep seat posts.

Stack - that's a hard one to guess. You can look at the headtube length and standover to get an idea of how much you'd have to drop from the seat.

DaveSSS 

There are only a few companies that list the stack and reach - Cervelo (the orginator), Trek and C'dal are among them. While the stack value is great, since it eliminates any difference in fork length, the reach values are easy to misconstrue. Reach values can only be compared at the SAME stack height. A lot of people compare the reach of a 51 and 54cm frame, without correcting the reach so it is measured at the same stack height on both frames. The result is the reach difference that is published is about 6mm less than acutal (3mm for each 10mm of head tube length difference).

You't just as well off comparing the TT lengths and making the correction for any difference in the seat tube angle. Each degree that a STA is steeper adds 8-10mm to the frame reach.

springs

When you say "steeper", I'm confused. Isn't 73 steeper (more upright) than 72? If so, doesn't this shorten the TT?