Road Cycling - Compact geometry

What is this exactly? I've heard people talk about it, seen manufacturers claim their bike to be it, but have no idea what they are talking about.

ok, this is in no way a "technical" description, but the ompact geo. is a "smaller geo. The toptube is at an angle down to the seat tube. its a slight angle, but ints not level with the ground. to do this, other parts of the frame have been shortened to compensate for this. There are som fitting issues (or so i have heard) but all i can say is that i love my allez, which is a compact!!

-Ross
PS: I'm sure i left some stuff out.. sorry

To add to what spazegun2213 said, the compact geometry is essentially a sloping top-tube. This was done primarily to allow a rider with (relative to "normal" proportions) shorter legs and longer torso to ride a frame with sufficient standover clearance. Mountain bikes went to a sloping top-tube design more than a decade ago because standover clearance is an important factour. With a traditional frame in order to obtain a proper standover clearance, shorter riders had to sacrifice top-tube length and often felt scrunched. Forget all the hype about compact geometries being lighter and nimbler... the difference in those areas are mainly cosmetic and performance negligable. Go with compact if you have fitting problems or like the looks of a sloping top-tube. Stick with traditional if you don't.

BTW, there are also other ways to achieve proper top-tube sizing with sufficient standover clearance than going with compact geometry.

Originally posted by khuon
BTW, there are also other ways to achieve proper top-tube sizing with sufficient standover clearance than going with compact geometry.

by using smaller wheels(650c) or using a standard geo. frame with a slightly sloping TT. BTW, all compact frames have sloping TTs, but only the small size standard 700c frames (47-49cm) has sloping TT's.

Originally posted by dexmax
by using smaller wheels(650c) or using a standard geo. frame with a slightly sloping TT. BTW, all compact frames have sloping TTs, but only the small size standard 700c frames (47-49cm) has sloping TT's.

Or crank the seat-tube back. That's how my Aegis is designed. It's a 700c frame in a 48cm with an effective top-tube close to that of bikes with a 52cm frame.

Originally posted by khuon
Or crank the seat-tube back. That's how my Aegis is designed. It's a 700c frame in a 48cm with an effective top-tube close to that of bikes with a 52cm frame.

i have noticed that on your aegis, i did that too on the last frame i did..

the frame is a size 48-49cm(ST) with an effective toptube as that of a 53-54cm frame..

I love this...
here is a compact geometry bike. And what a bike it is...

And here is the classic "century" geometry of the Vortex!!!! Perhaps I am biased because I own one, but this is a great bike.

The top tube is in fact level. It's just the perspective of the photo that makes it look somewhat sloping.

i will base the geometry of my next project on one of these two carreras. But I have not decided on what..

should i go compact? or standard? hmmmm...

http://www.redroseimports.com/images/car_shield2_b.jpg http://www.redroseimports.com/images/car_aries_b.jpg

both are steel.

BTW, sebring: the one on top uses a compact frame, and the other one uses a standard geometry frame.

hope it helps..

I got it now, thanks everyone. The pictures definitely did help.

The advantage to manufacturers of compact frames, is that they can support a wider range of rider dimensions with fewer frame sizes. This matters in a large mass-production factory, esp where they are producing moulded composite frames, but is not a better solution than a wide range of proper frame sizes.
For the rider the benefits are, allegedly, a lighter and stiffer frame.

These days, seatposts are available in a wide variety of lengths and laybacks, and stems are quick and easy to change, so you can, within reason, adjust any frame to fit your chosen points of contact (pedals, saddles, bars). There are builders who bodge the frame angles to make their frame appear smaller , but as some of the other guys have suggested, the really significant dimension in a frame is the top tube length. You can ride a frame with 4" of exposed seatpost or 8", and be quite happy on either, but if the TT is too long you will never be happy.

Compact or std? its really a fashion statement. The only point I would argue is that its harder to fit a luggage rack on a compact frame, where the seatstay eyelets are below the level of the wheel.