BlackPaw

Okay so i took measurments on the popular bike fit calculator from competativecyclist and i got these results



then i got aproximation of stack and reach from ridley



then i chose the bike i want to buy which is the specialized allez e5 sport with the frame size of 56



and now I am confused since there is big discrepancy in the suggested seat tube length... also i find it difficult to figure out which of the suggested dimensions from the calculator correspond to which dimensions on the specialized allez.

Any help would be greatly appreciated.

rm -rf

The best way to compare frames is by stack and reach. Most bikes have similarly angled seat tubes, and you can get different setbacks on the seat post, so the position of the saddle is quite flexible.

I'm kind of surprised that the CC fit calculator doesn't show stack and reach. It's "saddle setback" number, 7.9cm-8.3cm, is the setback distance from the nose to the bottom bracket. I don't like that measurement, since saddles are different lengths (but that saddle nose to handlebar measure is good for recreating your own bike's saddle position if you swap out seatposts, for example). The fit numbers aren't all that usable, I think.

The CC fit calc has "top tube length", which seems to be the horizontal equivalent length = 555 to 559 mm.
The Ridley shows the horizontal top tube = 549mm. That's pretty close.
Using an angle/length calculator, a change in the seatpost angle from 73 to 73.5 degrees would change the effective top tube by about 3-4 mm. That may be part of the difference.

The Ridley calculator says
Stack 573
Reach 392

The Allez has:
Stack 574
Reach 392

An exact match.


Stack and Reach
Stack and reach, which is measured from the center of the crank axle and the center of the top of the head tube.

PepeM

Specialized? I'm guessing you're getting it in a shop, right? Go test ride it.

69chevy

Measure your legs again.


Your thigh, plus your lower leg shouldn't add up to 30cm more than your actual inseam.

ptempel

+1

Also the virtual top tube length looks pretty small as compared to the seat tube length. Unless the OP has a short torso and long legs?

69chevy

Even if his legs are long, his inseam can't be 12 inches shorter than his lower leg plus his upper leg.


He measured wrong, for sure.

WhyFi

Without getting in to whether or not you measured wrong, it's a seat tube and it's not terribly important... as long as your seat post is long enough to position properly (while satisfying the min insertion length) and as long as you're not crushing your gonads on the top tube, you're good to go (at least as far as ST lengths are concerned). With a compact or semi-compact frame, ST is generally the least of your worries.

spectastic

the only metric that's really important to me is reach and/or effective top tube, and head tube. reach is easier to work with than effective top tube, because it's a function of eff top tube, seat tube angle, and head tube angle, and directly correlates with how stretched out you'll be. even as far as reach goes, you can get within 1-2 cm, and tune the reach with the stem length/angle, and handlebar reach/drop. the head tube length is important to me, beacause I have a relatively high saddle to handlebar offset. a lot of bikes these days have long head tubes, too long. I'm riding on a cannondale, and I still have to slam my stem all the way.

so don't pay too much attention to all the numbers. The only numbers you really need to worry about are the reach, and head tube length (or stack.. I think they're the same for the most part).