I can only speak for myself. I need a longer TT than normal geometries. You can get this in three ways, longer TT, seat back, longer stem or bars with more reach. If I size up with a larger frame to get the longer top tube, the bike feels too large and I have a hard time getting enough bar drop. If instead, I size down, the frame is lighter and stiffer, handling is quicker, I get better drop, but I have to slide the seat back and/or lengthen the stem.

Here is what mine looks like from an older shot.




Obviously the OP's set up really looks extreme (and probably wrong IMO), but in general, longer torso's can result in setback seat and or longer stem.

You should never adjust the seat to get a longer TT length. Any fitter will tell you the first thing to do is get the saddle position right based upon your hip, knee, leg and foot position to the pedals. Then you make stem and bar adjustments for reach after that. If that doen't work, you need a different frame.

How the hell did you get the bike to stand by itself for that shot?

Back on topic. I got 2 words for you - compact geometry aka sloping top tube. It all comes down to being able to fit 4 different sizes of riders on 1 size frame. So that being said sizing up and down framewise shouldn't matter in bike performance that much, especially if you are in the middle between 2 sizes. Additionally when you size up down your OWN body measurements do not change so you need to adjust seatpost height,/stem etc accordingly. If you have to go to extremes (min insertion mark,140 or 70mm stem, etc.) the frame size is not for you (too big or too small).

-Carcinogent

+1 qft!

I disagree. 58, saddle in middle of rails. 56, saddle farther back on rails. This gives you the exact same position over the pedals. Unfortunately, 58, head tube too tall so too little drop. 56, good drop. You can achieve correct hip, knee, leg, and foot position if you are between sizes (like me) by moving the saddle up or back. The larger constraint is head tube height as I now run a -17 degree stem to get even more drop on the smaller size frame.


Carc, the bike is so light I just put a dab of rubber cement on the tires and stick it to the concrete and it stands on its own. Otherwise, it would float away.

This sounds ridiculous but I think you guys are buying the wrong bikes. You want a S3 but obviously could find other bikes on the market with more suitable geometry for you (longer top tubes, shorter head tubes, more standover, whatever)

You seem to counterdict yourself about your own bike. Your bike is one size down? Don't think so. If anything it is big for you.
Why? Not much seat post...but because you have a short stem on. You say you need a long top tube and size down and yet you have what...a 90-100mm stem on your bike?
Seems completely contrary to what you wrote.

i was thinking the same exact thing. it actually looks like an 80-90 to me.

Nope, that was a 110 mm -12.5 degree stem. I have since changed to the following stem (110 mm -17 degree) to get more drop. As you can see, my saddle is pretty far back and 110 is on the longer end, bars have pretty good reach. This is my current build.



To go a size up would have hurt drop, etc. To go a size down would have meant even further back saddle and even longer reach stem. There isn't a lot of seat post because I have a longer torso, shorter legs as previously mentioned.

those two stems are the same length? that picture is EXTREMELY deceiving then. The smallish computer on the first one barely fits on that stem.

Moral of the story: Get fitted BEFORE you buy a bike!

I am not criticizing your fit...you look well fitted...but you aren't one size down by any stretch. Also, you pushing your saddle back is by choice. Some run in front of KOPS with a straight post.
You would have the same fit with a straight post and 130-140mm stem on the same frame...your CG would be farther forward is all with more weight over the pedals which some racers prefer.
Point is...fit is largely a choice and not an absolute. Some may prefer their saddle back to take weight off their hands but with a 110mm stem you have ample room to move your cockpit more foward and preserve the same reach.
Very nice bike btw.

The Zipp stems are very fat ... makes them look short.

I think the point is there is a fair amount of flexibility withing geometries. You do not have to put your saddle in the middle, use a normal length stem, and keep switching bikes till you find a matching geometry. You can adjust a reasonable amount and get a good fit by adjusting saddle position, stem length/drop, and bar reach/drop.

IMO the OP could be pushing things too far, at least on that saddle as it may be outside the normal mounting range. Also, since he has the bars raised quite a bit (head tube height was not an issue), I would think he would do better on a larger frame.


I agree Campag, I was just saying I was between sizes when fitted and could have gone either way.

And don't blindly follow online calculators. From snippets of the OP's Trek in other threads, it looked like it set up pretty normally, but he let an online calculator tell him he needed a smaller frame, and hence all the discussion here.

Didn't read through the whole thread. How small is the bike pictured above? It looks like a little mini-Cervelo. 50cm? 52cm?

Love Cervelo but really don't like the look of that crank. I assume it's Dura Ace 7800. I personally prefer the more open, aggressive look of the SRAM Red crank. Love the black color too.

Whoops...sorry...like the crank above...not a fan of the OP crank...

That makes perfect sense and I agree. But your orginal statement that you can get a longer TT length by moving the saddle back is misleading.

By the way, nice looking bike! Looks almost like mine.

Is yours an '11? It looks like all of their frames (now at least) either have a 73 or 76 degree seat tube angle (you can choose the angle on any size). I think on most bikes there isn't much difference in seat tube angle throughout the line.

When you're being fit to a bike your saddle to BB distance should be already set. Since the seat tube angles are all the same, the only difference between a smaller and larger frame (at least in terms of setback) would be how much seat post is sticking out of the frame. With a smaller frame you'd have more seat post sticking out, but that seat post would the same angle as the short seat tube. With a larger frame you'd have less seat post sticking out, but your saddle would end up in the same position. Your BB to saddle setback and height would be the same regardless of the frame. The only time a bigger frame wouldn't work is if you bottom out your seat post before reaching your proper seat height.

Whether you got a 56 or 58 your seat post would end in the same position, you'd be in the same place on the rails of the saddle either way. Now if there's much of difference in seat tube angle, it'd be a different story. I don't think the difference in the angles would be so great that you'd need to do much more than a slight shift fore/aft.

The only thing that matters (in respect to fit at least) in a geometry is Top Tube length, everything else can be adjusted (unless the frame prevents you from setting the seat low enough or high enough than a minimum insertion line on the tallest seat post available)

What are those things above and below the chainstays?

+1

I disagree. Unless you want to take a saw to the head tube, you may not be able to achieve the drop you want. TT and head tube have to be considered together. I agree with the rest of what you said though.

Polar power pickups.

I guess that's true too, but not too many people have their stem on right on their head tube. (not to take away from your point) I guess it's just frustrating to see people saying that you need a setback post because you have a long torso. I have a relatively long torso and people keep saying my frame is the wrong size because I don't have much seat post, it just means short legs relative to my horizontal top tube.

Oh well, hopefully the OP has a good fit, because it's a sick looking bike

I just shattered in tears.

My case is plain and simple - LBS did HORRIBLE job. Not only they didn't fit me properly but they also forgot to tighten stem bolts (!!!!!). Rear derailleur was not properly adjusted. This is the first and the last time I went there. Going to get a proper fit at reputable place on Monday.

Some adjustments and you'll be fine.