Singlespeed & Fixed Gear - Frame Sizing ~ Center To Center vs. Center To Top

Hey there!

I currently ride a 53cm Bianchi Pista (measured center to top) yet I was interested in picking up a De Bernardi track frame, a 53cm (yet measured center to center). Would they be extremely close in size? The De Bernardi site is lacking is the needed specs which is why I ask. Would they be extremely close in size?

a 53cm c-c would be close to a 55cm c-t. I think.

The geometry is available here:
http://www.worldclasscycles.com/track_frames.htm

Thanks for the link, they list the top tube measurment but not the seat tube measurment. Where do you think I could find that out?

Thanks for the link, they list the top tube measurment but not the seat tube measurment. Where do you think I could find that out?
The blue bar in that table that says:

A. SIZE (center to CENTER) 51 53 55 57 59 61

is the seat tube measurement
center to center

De Bernardi has a site? what's the URL?

The top tube is what really matters. Old steel bikes were often built "taller" than modern bikes. I have an old Steelman 61 that has the same top tube as a 57 Look. TT affects reach. Seat tube really is only relevant if you can't straddle the TT... but standover should rarely be an issue.

Thanks alot for all your insight!

Seat tube measurement affects more than just standover, though. (I'm trying th think of the right way to say this...) If you step down a size in seat tube length, you'll have to crank your seat up more, making you reach down further for your handlebars, which might make your back uncomfortable. In your case, the opposite, you may not be as aero as you want (if you want that), because your seat will most likely need to be lower than on the Pista.

Does that make sense? Intelligent grammar seems to have evaded me tonight...

top tube length is important but can be adjusted with different sized stems. Most frames are sized by seat tube length. Standover has little to do with it as bottom brackets height will greatly affect that. The important thing is to preserve KOPS and to make sure that you have proper leg extension at the bottom of the pedal stroke. The top tube will be sized proportionally to the seat tube, so only those with an exceptionally long or short torso will have any issues.

All this is a little less important these days when you can get long seat posts and stems. Saddle height, stem height, and stem reach will all allow you to adjust a smaller frame to a larger rider, thus the move to compact geometries.

On the other hand, Bontrager says KOPS is garbage, so who knows? :) http://www.sheldonbrown.com/kops.html

Yes 53cm C/C is 55cm C/T.

Proper seat tube measurements is 1st in my book then all else follows.

S/F,
CEYA!

Oh yeah, and since it's topical, standover on a track frame in particular will be misleading as they have higher bottom brackets. As I've mentioned before, my own Fuji Track splits the beans nicely when I'm standing flatfooted (consequently I only stand over it with the frame cocked to one side or the other), but overall it's quite comfortable.

I think it is a very small difference maybe only 1cm, nothing to worry about. I agree with others who have said the TT length is the most important. I would rather make seat height adjustments to fit a bike rather than stem lenght. With in reason of course.

Yes 53cm C/C is 55cm C/T.

Proper seat tube measurements is 1st in my book then all else follows.

S/F,
CEYA!

Seat tube? There are a lot of backwards priorities here at the fixed forum- must have something to do with the anti-roadie sentiments around here? If you posted this in the roadbike area, you'd receive the exact opposite response: find a TT that fits.

Knock yourself out, but I'd much rather NOT be all cramped in the cockpit- and sorry, but making crazy adjustments with stem length is simply a poor substitute for good bike fit ( crazy like a 52cm frame with a 140 stem, or a 62 frame with an 80 stem). There is a reason bikes are sized in 1 or 2 cm increments... or that people buy custom bikes.

Finally, I guess who really cares about comfort on a track bike? Track events last a matter of minutes by design, unless you are the next Boardman or Obree trying to break the hour record... compared to a roadbike where you spend hours in the saddle, up and down hills...

Say what you will, but there's a reason that frames are measured by seat tube length. There's a reason that back in the bad old days it was the seat tube length that was the variable part of the frame's dimenions. LeMond's sizing formula is also based on inseam.

Is top tube length important? Sure! That's why custom frames are custom. See then you can make sure that you have proper leg extension and positioning as well as a comfortable crouch. That's why proportionally sized frames became popular, we don't all have the same torso length, so as inseam varied it made sense to vary TT length too.

However, when buying off-the-shelf, frames will be sized by seat tube length. It's true that you can adjust your reach to the pedals by adjusting saddle height. On the other hand, you can find just as adjustable stems. There's the Look Ergostem, for example, that will allow you to adjust your reach to the bars. In fact, I would submit that will change more often depending on the type of cycling you're doing (sprinting, racing, randonnée). Your reach to the pedal never changes.

Yes, a grotesque stem on a too short top tube is a poor substitute for proper fit. On the other hand, a too-tall saddle is just as poor and will also require you to extend your stem to bring it back up to a proper height. In the end, the bottom line is that it's better to be to small in either dimension and size up than to have a too-large frame.

There's the Look Ergostem, for example, that will allow you to adjust your reach to the bars. In fact, I would submit that will change more often depending on the type of cycling you're doing (sprinting, racing, randonnée). Your reach to the pedal never changes.



You are absolutely right- reach to the pedal doesn't change, but if you consider that most seat tube angles are relatively standard these days (depending on type of bike), then top tube length does become the key variable. The only reason I even bring it up is because there are so many ways to measure seat tube- to the point it is meaningless. Trek measures to the top of the clamp, so a 58 Trek will be smaller than a 57 Look, for example- and will usually have a correspondingly smaller top tube. Some top tubes extend above the seat tube, and the extension may or may not be included in the measurement, depending on the brand. Others are measured to the center of the top tube. In my experience, the best apples-to-apples comparison involves TT measurement (relative to seat tube angle).

YThe only reason I even bring it up is because there are so many ways to measure seat tube- to the point it is meaningless.

Agreed. Which actually brings us nicely full circle to the begining of this thread. Well done!