http://static.flickr.com/19/104272616_2353d03058.jpg

i've got a little slope.

This reminds me of a similar argument i had when discussing why some wine bottles moved from cork to plastic, for the cork allowed air to pass through which causes all sorts of problems, from the growth of mold to the distortion of taste. Despite plastics clear advantage over cork, most wine guru's prefer a bottle sealed with cork for it is the wine tradition. This relates to sloping top tupes, for thier lack of acceptance is due to thier lack of following tradition, which, imho, is ridiculous, considering that there are advantages to its shape/geometry, which should be more important than just asthetics, unless you are too much of a poser to give a s**t. I guess thats why my fixie has a slope in the tt.

Now now, let's not sling around 'poser'.

What if, once you balanced out everything, it's still a better solution? Just because the seat post is longer doesn't mean it isn't still a superior solution. Engineering is about balancing trade-offs. There is no such thing as a '100% win', where a change benefits something without hurting something else.

In my original post on the subject, I presented two thoughts:

1) a sloping top tube provides the geometry for a longer head tube, which means more distance between the headset top bearing and bottom bearing, and, intuitively, this seems stronger and allows a lower stand over height for a given head tube length; and,

2) the smaller frame requires a longer, weaker, heavier seat post, and the whole idea amounts to a meaningless styling gimmick.

I tend towards the first thought.
The bike pictures posted in this thread which exhibit a downward sloping top tube have short head tubes and thus very little distance between headset bearings.
This looks obviously weaker than headset bearings spaced further apart.

An upward sloping top tube allows more distance between headset bearings and, at the same time, a lower stand over height.
I think this has relevance for the smaller versions of a given frame.



.:Jimbo wrote the above, I assume, in support of upward sloping top tubes; however, he did not give any examples of "advantages."

Joshr posted a picture of a really interesting looking Bianchi.
Could he tell me something about it?

Post Script:

Regarding joshr's Bianchi, if it didn't have an upward sloping top tube, the top tube and bottom tube would almost meet at the head tube.
This would put much greater stress on the junction of the tubes.

its their new 'San Jose': http://bianchiusa.com/06_san_jose.html

currently bone ass stock and coastable, hoping to fix that soon.

actually, their pic gives you an even better perspective:

http://bianchiusa.com/typo3temp/4ecec55f7e.jpg

yup I'm aware of the tube sizing.
and i've heard that rumor as well.

I agree most with this philosopy when it comes to sloping TT's

except maybe the "stronger" bit

Where'd you get it? I'd love to test ride one of those things.

missing link in berkeley. what size do you ride?

50-52, ideally.

I'll have to drop in and check it out.

as of about a week ago they've had a 52 in the shop for quite some time. bet its still there.

Sloping tops look good on small bikes, meh on short bikes, and fugly on bikes 60cm and larger.

flip that.
sloping TTs on midget bikes make them look like BMX

Case closed.

http://www.ifbikes.com/images2/2005/track-lg.jpg

Baxtefer wrote the above in response to my conjecture that a greater distance between the upper and lower headset bearings would make a bike stronger.
This seems intuitively correct to me, but intuition has led me down the path more than once. :)

I'd like to hear from a certified engineer who presently works for a frame manufacturer.

In all possibility, I could have gotten it right with my second thought:

2) the smaller frame requires a longer, weaker, heavier seat post, and the whole idea amounts to a meaningless styling gimmick.

"And, if you vote for me, I promise a bicycle in every pot and a chicken in every garage."

I'm an engineer. sort of. more like a physicist though.
then again, i haven't touched that stuff in a few years.

anyway.....

1) "stronger" re.. the headtube. I don't think it makes a huge difference. If anything a longer headtube would be weaker due to the longer lever arm.

2) you're pretty much right about the seatpost, re weight. you'll gain more weight from the extra seatpost than you lose with the 3" of tubing. the longer seatpost won't be significantly weaker though.

there's a good discussion about "compact" geometry going on over in the frambuilder's forum. Some good comments from e-Ritchie about the 2 design schools when it comes to sloping TTs.
Personally, I don't buy the stiffness argument, but I'll gladly get a sloping frame to get standover clearance for my dispropotionately short legs, while maintaining a decent handlebar height.

Yep, up-slope top tubes are ugly. Irrefutable.

My favorite bike with a foward slope:

http://i24.photobucket.com/albums/c4...l/9b47a4fe.jpg

****ing sexy.

I'm refuting it. Up-slope top tubes are sexy.

eeeew

crazy ass spoke pattern,
what are they called?

You can't just refute. You have to give evidence, provide an argument. Simply stating your opinion as the alleged "refutation" gets nobody nowhere.

I posted that to point out the sheer idiocy of the original idea. I need to provide no 'evidence' to refute a personal opinion. By nature it's not possible to 'prove' or 'refute' taste or likes/dislikes.

Dura-Ace Wh-7700s