's Forum Archives - General

Archive Home >> General(1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 )

Bone-headed question of the day(12 posts)

Bone-headed question of the dayC-squared
Nov 28, 2001 7:06 PM
"Compact Geometry"

What the hell does it mean??

What does it purport to do??

re: Bone-headed question of the dayAllen az
Nov 28, 2001 7:39 PM
The top-tube is slanted down. An example...

(Others might give more detail).

my 1/3 cent. : )
not just slanted top tubeskenyee
Nov 29, 2001 6:21 AM
Some, like the Gios Compact Pro, have shorter chainstays instead...
re: Bone-headed question of the daybikerduder
Nov 28, 2001 7:50 PM
Supposed to 1) decrease weight due to less material used and 2)increase stiffness due to smaller [ie stronger]triangle
One more theory...jtolleson
Nov 28, 2001 9:25 PM
And no, your question isn't bone headed...

It may be designed as a marketing stunt for builders to save money by offering only 3 sizes of frames where they used to offer 5-6 (S, M, L substituting for 50-62).
Ms CynicalGracious
Nov 28, 2001 11:01 PM
and usually in touch with a sense of the truth.
Not so sure...MikeC
Nov 29, 2001 6:22 AM
It's possible that it might have started that way, but that doesn't explain builders like Seven who are currently pushing compact frames. Their compacts are just as custom as their traditional formats.
I must admit, however, that I'm puzzled as to why Seven's top-of-the-line frame, the Alta, has multiple-butted tubes, supposedly to tune the ride to the nth degree, yet has a huge length of unsupported seatpost providing one of the three major contact points between the rider and the bike.
I can't believe that it's all marketing, as their customers tend to be experienced riders with a traditionalist viewpoint.
Why Seven does it...ohio
Nov 29, 2001 12:46 PM
... or other high end companies.

While the long seatpost offsets some (but not all) of the weight savings, what you end up with, is a laterally stiffer frame for out of the saddle pounding, but a nice length of shock absorbing (if heavily leveraged) seatpost. Especially if you use a Ti post. You have to be careful though because that long post puts a lot of stress on the frame, and needs to be thicker than normal since bending moment is proportional to length of the lever. Weight savings probably balances out to zero or close on a well built frame. But you get the aforementioned benefits, plus it might save yer knuts if you slip off your carbon soles at a stoplight.

For Giant, it allows them to sell frames that weigh nothing and fit most people well enough for super cheap... If weight is more important than a perfect fit (you don't mind fiddling with layback vs. non-layback posts, and all different stems and headset spacers, to make your compact frame fit right) than these bikes make perfect sense.
P.S. Check out Cannondale's websiteohio
Nov 29, 2001 12:49 PM
They have thus far refused to use compact geometry (I can see the gory battle between marketing and engineering right now... for the time being engineering is winning). I think there's a long explanation of why on their website.
Compact GeometryC-Sqared
Nov 29, 2001 1:38 PM
Thanks. This all makes sense. I'm riding an aluminum specialized allez comp that I've had real trouble trying to fit me - this explains why I've got sooo much stand-over clearance (in addition to the frame being overall too small for me). Also, I've been getting really beaten up on rides over 70 miles.

Maybe its time to give traditional geometry steel a try....
On the contrary!cyclequip
Nov 29, 2001 3:41 AM
What about the countless builders who custom-make frames with compact geometry? Or those offering compact frames in the usual sizes. Rather it follows on the successes MTB builders had with 1) allie frames 2) 'compact'geometry forced on them by the discipline - and remember MTB's are a relatively recent thing, and 3) new thinking that moved away from traditional frame geometries as new and better materials surfaced.
good for long torso riders....C-40
Nov 29, 2001 3:16 PM
Few people have bothered to notice that compact frames, with their sloping top tubes may provide a good fit on a stock frame for long-torso riders (which you may be). You've posted your height at 5'-6" (bare feet?). With that height, a rider that fit well on a stock frame would have an inseam in the range of 31-32 inches. I'm less than an inch taller than you, with a 32-5/8" inseam, for example. If you happen to have an inseam of only 30 inches, stock frames that you can stand over won't have enough top tube length.

A compact frame like the Litespeed Siena might be just the solution. A 55cm Siena has an advertised standover height of 73.7cm (29 inches), combined with a 73 degree STA, 55.5cm TT and 14.3cm head tube length. The 29 inch standover is more than 2 inches lower than a 55cm Tuscany model. This geometry would be a substantial improvement over that 50cm Allez. The additional top tube length would probably allow you to use a 110 stem and the head tube length should eliminate the need for head tube spacers.