Compact Frame Design
03-28-08 | 07:26 AM
#26
Just call me Chris
Joined: Dec 2007
Posts: 451
Likes: 6
From: Austin, TX
Bikes: 2019 Reven Voltage, 2007 Kestrel RT700 & Univega MB hard front/tail and is 27 years old.
All functional considerations aside, Esthetically, compacts do not work (for me). I can live with the slight slope such as the BMC but the traditional level top tube is the best look.
03-28-08 | 09:04 AM
#27
Sua Ku
Joined: Aug 2006
Posts: 5,705
Likes: 2
From: Hot as hell, Singapore
Bikes: Trek 5200, BMC SLC01, BMC SSX, Specialized FSR, Holdsworth Criterium
He knows that... the post indicates the giant as a compact, the trek a traditional, but is questioning whether the BMC is compact or traditional (since the top tube is almost horizontal - ie: between compact and traditional... where is the line drawn????).
I believe the BMC is traditional.... but who really cares - strictly categorizing bikes in compact/traditional won't change their geometries... just go with the geometries...
I believe the BMC is traditional.... but who really cares - strictly categorizing bikes in compact/traditional won't change their geometries... just go with the geometries...
05-10-08 | 09:42 PM
#28
Senior Member
Joined: Jul 2007
Posts: 136
Likes: 0
From: Maryland
Bikes: Bridgestone '90 RB-1, Giant TCR Alloy, 90's mountain bikes galore.
+1 on the rider being the main source of weight (not to state the obvious but I outweigh my bike by a factor of 10+).
What would affect center of gravity is how my weight is distributed. Since BB height, bar height, and seat height are virtually identical, my center of gravity is virtually identical.
If I took a picture of me on a bike (from the side) and erased all the frame/stem/post bits, I could redraw the frame which ever way I want using the same head tube angle, rake, and bar/seat/crank position. As long as the bike is about the same weight/stiffness, I still have some range of motion, the bike would essentially handle the same. I could be on a frame that resembles a BMX frame (which I think would be ideal for me due to tiny main frame and long front end which matches my gorilla like limb proportions) or one that was standard.
Compact sizing allows a wider range of leg lengths to fit on a given (lengthwise) length frame. In other words, if I wanted to ride a 55.5 cm top tube, I'd have to buy a pretty tall frame (54-55 cm). I have short legs and ride a 52. Therefore I could not fit a "standard" frame with a 55.5 cm tt. But, with compact, I could buy a (for example) size M Giant. It has an approx 50 cm seat tube and I can both stand over it as well as have the seat at the right height. No way I could do this on a standard frame.
Having said that, I first went to a size S Giant (53.5 tt) and then recently I moved to a 52 cm standard (53.5 tt also, but 1 cm shorter head tube).
If I were a team director with a lot of different riders (Slipstream), I'd want spares that fit as many riders as possible using the fewest bikes. A compact frame would allow me to fit more riders onto a frame without compromising their fit too much. For example, if my team had all Cannondales, I'd have to carry around frames like 52, 54, 56, 58, 60 to fit most riders. If my team had all Giants, I could get by with just M and L, maybe XL too. Even if a rider really mangled his primary bike, a mechanic could do a stem swap to adjust the spare bike's fit more precisely (or use an adjustable stem).
Any difference in handling etc has to do with things that have nothing to do with standard vs compact. It has to do with tube specs, stiffness, etc. My compact Giant TCRs are *way* more noodly than my standard Cannondale.
cdr
What would affect center of gravity is how my weight is distributed. Since BB height, bar height, and seat height are virtually identical, my center of gravity is virtually identical.
If I took a picture of me on a bike (from the side) and erased all the frame/stem/post bits, I could redraw the frame which ever way I want using the same head tube angle, rake, and bar/seat/crank position. As long as the bike is about the same weight/stiffness, I still have some range of motion, the bike would essentially handle the same. I could be on a frame that resembles a BMX frame (which I think would be ideal for me due to tiny main frame and long front end which matches my gorilla like limb proportions) or one that was standard.
Compact sizing allows a wider range of leg lengths to fit on a given (lengthwise) length frame. In other words, if I wanted to ride a 55.5 cm top tube, I'd have to buy a pretty tall frame (54-55 cm). I have short legs and ride a 52. Therefore I could not fit a "standard" frame with a 55.5 cm tt. But, with compact, I could buy a (for example) size M Giant. It has an approx 50 cm seat tube and I can both stand over it as well as have the seat at the right height. No way I could do this on a standard frame.
Having said that, I first went to a size S Giant (53.5 tt) and then recently I moved to a 52 cm standard (53.5 tt also, but 1 cm shorter head tube).
If I were a team director with a lot of different riders (Slipstream), I'd want spares that fit as many riders as possible using the fewest bikes. A compact frame would allow me to fit more riders onto a frame without compromising their fit too much. For example, if my team had all Cannondales, I'd have to carry around frames like 52, 54, 56, 58, 60 to fit most riders. If my team had all Giants, I could get by with just M and L, maybe XL too. Even if a rider really mangled his primary bike, a mechanic could do a stem swap to adjust the spare bike's fit more precisely (or use an adjustable stem).
Any difference in handling etc has to do with things that have nothing to do with standard vs compact. It has to do with tube specs, stiffness, etc. My compact Giant TCRs are *way* more noodly than my standard Cannondale.
cdr
I actually bought a used Giant TCR that is a compact medium (50cm seat tube, ~55 top tube). I haven't built it up yet though.
I'm curious, why did you go with a Giant compact small rather than the medium? Thanks.
05-10-08 | 11:52 PM
#31
Senior Member
Joined: Jan 2006
Posts: 1,359
Likes: 2
From: Ruidoso, NM
Compacts are usually a little lighter overall. The seattube, toptube, and chainstays are shorter... the seatpost is longer. The longer SP gives a little more compliance which is nice. The tighter main tubes probably improve the torsional stiffness a bit.
One benefit of compact is that crotch clearance becomes a non issue, and you instead size the frame by height (basically headtube length) and reach.
One benefit of compact is that crotch clearance becomes a non issue, and you instead size the frame by height (basically headtube length) and reach.
05-11-08 | 04:25 AM
#33
Occasionally Here
Joined: Mar 2006
Posts: 316
Likes: 0
From: αιθήρ
Bikes: Secret......
I have mostly ridden traditional. I have a Compact (aggressively compact Giant) and a semi sloping. I rode many bikes in my search. I really like the semi-sloping geometry, I FEEL like I am more part of the bike, less on top of it. These are all my personal opinions, so before you buy read the PDS.
02-21-09 | 11:43 AM
#34
Senior Member
Joined: Jun 2007
Posts: 3,644
Likes: 1
From: Brooklyn, NY
Bikes: 2008 Giant OCR1 (with panda bear on the back!)
I was doing a bit of digging on the differences between compact and traditional, and am bringing this back up for the curious.
I have both a traditional frame (Trek 1000) and a compact frame (Giant OCR1). The compact bike does much better on short rises and gradual inclines; I'm actually going to ride my Trek today for a few miles and see how much of a difference it makes on flats. The compact feels faster though.
I have both a traditional frame (Trek 1000) and a compact frame (Giant OCR1). The compact bike does much better on short rises and gradual inclines; I'm actually going to ride my Trek today for a few miles and see how much of a difference it makes on flats. The compact feels faster though.
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02-21-09 | 03:30 PM
#36
Old fart
Joined: Nov 2004
Posts: 26,345
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From: Appleton WI
Bikes: Several, mostly not name brands.
