ecp8

Can anyone point me in the right direction for information regarding the benefits of sloping top tubes versus traditional straight top tubes? I've googled and get nada.

Brillig

You'd probably do better googling on "compact geometry" instead of sloping top tube.

https://www.bikeforums.net/archive/in...p/t-42587.html

urbanknight

Benefits of compact geometry: Manufacturer can produce (edit) fewer sizes, making them a larger profit.

That's basically it.

dcvelo

Depends on the individual frame....you can't really generalize (with the exception that you'll have more standover clearance on comapcts, of course). I have one of each and both ride very well.

cuski

"Compact geometry road frames have a lower center of gravity and tend to have a shorter wheelbase and smaller rear triangle, which give the bike quicker handling. Compact geometry also allows the top of the head tube to be above the top of the seat tube, increasing standover clearance, and lowering the center of gravity."

CharlieWoo

Um, you mean "fewer sizes". Ryanf is rubbing off.

CharlieWoo

Yeah, a lower center of gravity without the rider. With the rider in the equation the difference is insignificant.

urbanknight

Thanks. And to think I call myself the grammar police

sirtigersalot

according to salsa at least, it increases the frame stiffness, if you wonder where it says this, its in the description of the campeon (my bike whee)

urbanknight

^ Marketing Propaganda.

Cassave

That's basically it.

I've heard marketing hype like "greater standover clearance" and "a stiffer main triangle"
to justify it but it comes down to simplified manufacturing (read: lower mfg. costs)

waterrockets 

Flat top tubes give you more room for the 2nd water bottle. I've almost got room for two just on the seat tube. They're easier to sit on when standing next to the bike. They're easier to shoulder-carry, and are more vertically rigid.

Compact frames enable a lot of seatpost flex on bumps (if it's round), which mitigates some of the effects of a shorter wheelbase. They're also more rigid laterally, and lighter. The weight savings are partially negated by the longer seatpost required, which has thicker walls than the frame tubes.

merlinextraligh

Hence the development of the integrated seat mast.

dirtypete

i think that any benefits alleged are very negligible.

purely on looks alone i would go for traditional every time, i think the compacts look wrong. there's no beauty there...

tpelle

I prefer the traditional frame because I feel that the compact frame geometry leaves too much of the seat post exposed. Think of the seat post like a lever. When you plant your butt on it you're applying a force that's trying to pry your frame apart.

Avalanche325

On a MTB - standover clearance for the rider.

On a road bike - fewer sizes to manufacture. The other reasons are marketing to help sell compact frames.

There is nothing "wrong" with them. But the "advantages" that the manufacturers tout are BS.

Homebrew01

Yup +1

rickhigbee

+1 I've never thought of it in those terms other than I knew it had to put more stress on the frame using the principle of levers.

Spin Cycle

The compact frames just don't look right - seeing the really long seat posts, makes it look like an adult is riding a kid's bike. Harder to carry on a rack as well.

redirekib

I agree with everything the above posters said, but I like the look of a compact and have an Giant TCR as well as a bike with traditional geometry.

koine2002

It's funny the old thread referenced above, everyone was in love with the compact geometry. Now it seems everyone sees no functional difference between the two. I just find it interesting.

DocRay

That, and stronger and lighter.

The only downside of compact is bottle placement for smaller frames, ...but no one under 5'6" should even ride a bike.

cuda2k

I had to go back to a regular ole aluminum bottle holder on the seat tube of my Flyte to get a 24oz Polar water bottle in/out without struggle, and it's a 56cm and I'm far taller than 5'6". Tried three other plastic & carbon cage designs and all of them were a complete PITA to use while riding.

I'm a big fan of Traditional top tubes, I have 3 steel bikes with traditional design that I love the look of. I can't speak for the differences in stiffness, weight and all that as there are many other factors between my traditional and compact frames that account for far more than the top tube design.

dcvelo

I've never had any trouble with the bottles on my Klein (55 cm). I guess maybe the mounts are positioned a bit differently.

And after three years of trying to pry it apart with my seatpost lever, all I can say is I'm going to have to try harder. It's been holding up pretty well.

Overall I believe that compact design is largely intended to simplify manufacturing but based on my riding experience I don't think it has any significant disadvantages over traditional frames. YMMV....

mandovoodoo

See https://spectrum-cycles.com/616.htm

I thought they looked funny. The compact thing. I got one made of plastic and black cloth in Italy because so many smart riders seemed to like them. I got the smallest frame I could reasonably ride, so I have a 400 mm carbon seatpost and a long stem. Tiny funny looking bike, looks like a toy.

Have to agree with Kellogg. "[N]imble liveliness" would capture the essential difference.

Kellogg: "Our first compact frame (still my favorite frame) was an exact replica of my then current titanium frame in materials and geometry save for the sloping top tube. . . . It was lighter (about 4 ounces) but it was not appreciatively stiffer. . . . The big change came when I stood to accelerate or climb. As I stood up, the bike appeared to loose three pounds. The inertia of the bike as I rocked it back and fourth was reduced so much that I felt as though I was on a twelve-pound bike. Interestingly, when seated, a compact frame feels exactly like a traditional design. The compact design has no effect on handling beyond the increases responsiveness during climbing and accelerating."

I absolutely concur with this assessment. Out of the saddle hard up hills it's great! Otherwise, no difference, except my nuts are happier.