CampioneDItalia

Hi folks

So around 2000, Giant discovered the advantages of compact geometry. They could produce a bike with the "same" fit as a trad bike, using less tubing (saving weight) and increasing stiffness (smaller triangle reduces lateral torsion). The only difference is that the rider would have to use a longer seatpost.

Why then, do manufacturers today produce carbon frames with horizontal top tubes? I'm not getting it, given that they are trying to keep frame weight to a minimum.

iab

Who said that, other than you?

FBinNY 

While sloping top tubes have advantages for more casual riders who benefit from the relatively higher head to seat height, this doesn't benefit racers who prefer lower heads. So a sloping top tube would mean a longer seatpost, and greater stresses because of the increased cantilever. Weight isn't a consideration since bikes are already below the UCI mandated minimum.

fietsbob

Tradition, and UCI constraints.. You can find many pictures of bikes other than that one that look different..

you found one to confirm your bias.

Bandera

That would actually be:

BTW: In what way is >2000 production C&V?

-Bandera

skijor

Perhaps that certain accessories would be rendered unusable, or at least less user-friendly. For example, would a standard large water bottle fit on the seat tube? I know that's a problem for smaller size traditional frames. Also, transporting a bike with a smaller opening to hang on a trunk-mount rack could be rendered impossible. Just speculating.

People like the familiar...especially cyclists.

arimajol

Horizontal top tubes just look better. This is C&V, after all!

fietsbob

Recumbents dont, but they're illegal for UCI, the high profile pro racers every one emulates, and expects to own , are like the pro's ride..

there are carbon fiber recumbents , the fastest human powered bikes are carbon and shaped like a fish.

Lazyass

What Giant didn't say is that compact geometry saves them money because they don't have to make as many different frame sizes. I don't think you'll find many, if any, compact frames that come in 2cm increments. I don't like them.

Bandera

And the award for a total dedication to Off-topic, Non-Sequitur and generally Unintelligible postings once again goes to......

-Bandera

fietsbob

unless they look like they were old school diamond frame, posting on C&V would be a waste of time..

time wasters... Go !

ironwood

Who cares about "modern" bikes anyway?

Salamandrine 

My nickel Mongoose had compact geometry back in the late 70s...

tyrion

That's it. Compact frames aren't lighter when the seat post is factored in, they're a cost cutting measure.

Kontact 

Maybe you don't get something for nothing, and the weight required to make a long post as stiff as a normal post is not actually less than the weight saved by angling the frame tubes?

tricky 

I don't think your premise is accurate. The first page of google image search for "carbon fiber bicycle" is all bikes with sloping top tubes. That's not a scientific survey of all carbon frames, but go look at the frames from Trek, Spec, and even Colnagos. But, yes, @FBinNY is right too. Frames have gotten so far under the UCI minimum that designers can do what they want visually (and with aero) and still need to add lead weight to a complete bike to make it legal to race.

CroMo Mike 

The only material saved by slanting the top tube is about 2" of seat tube and 2" from each seat stay. That much carbon (or aluminum, or steel) tube would weigh next to nothing. All the same lugs, seat tube clamp, etc., are still there. Plus the slanted top tube will be slightly longer. So even before the seat post is figured in, very little weight is saved from the slanted-tube frame.

CampioneDItalia

Why are SOME modern bikes still built with traditional geometry?

I didn't occur to me that I had to use the qualifier "some". The question itself implies that the modern bike uses the "modern" design, and that it is more prevalent than the "traditional" (i.e. non-modern) design. Modern "means" sloped TT, traditional "means" horizontal TT. Obviously we all know that. The question I had was why are there "any" modern bikes with traditional geometry "given" the (possibly faulty) reasoning that sloping results in lesser weight and increased torsional resistance (i.e. it is a better design).

Anyways thanks for all those who gave adult replies.

repechage

Original post was curious in my book too upon reading.
The sloping top tube, S/M/L was fantastic for inventory control, at the distributor and shop level.
When I read geometry, I was thinking about the factors that really matter. A sloping top tube is often not relevant.
Later is has allowed some to have a frame that appears less goofy with lots of spacers below the stem.
Extended head tubes have their place.

iab

Why are some bikes blue?

texaspandj

Why are modern bikes still built with traditional geometry?

If it ain't broke don't fix it.

DMC707

Whether the seat tube is level or sloping, the numbers have been close to the same for decades--
The really haven't been any radical geometry changes with the exception of triathlon bikes getting much steeper

The geometry of Big Mig's Pinarello likely isnt much different than Froome's, although there are cosmetic design differences -----

tyrion

For better strength/weight and some people prefer the aesthetics.

Slanted top tubes allow fewer sizes to fit more people so it's a cost saving design, also more crotch clearance for off-road bikes.

edit: and a slanted top tube with a longer seatpost with some flex can provide a little more cushioning.

Road Fan

Hear, hear!

Bandera

Race bike geometry changed with the road surfaces.
The dirt, pave' and gravel of rural roads, the brick and paving stones of the town centers and the goat tracks of the high mountains in Europe & the UK gave way to tarmac in the post WWII reconstruction. Cross bike geometry and mud clearance were no longer necessary for road racing or time trials on pavement so "new" designs evolved for the new racing environments with the ability retained for racing on the pave' of the Spring classic. By the late 70's the evolution was complete with the dedicated Criterium bike evolved for the unique racing conditions here in the US tightening things up a bit more worldwide. All done & dusted in the C&V time frame w/ changes in materials not design geometry that matter to come, with the exception of the dedicated TT machines. And who really cares about "modern" bikes anyway?

-Bandera