Road bikes. Why in the main is the flat top tube retained?

[Herman Toothrot]

So other than a few manufactures road bikes still in the main appear to cling to the flat top tube. I say cling as back 20 years ago mountain bikes looked like that as well, but being a new idea people seemed happy to mess with tradition and go for practicality, top tubes dropped sloped as much as possible. Result, more clearance, less weight, stiffer and they look way better. Not going to pick on any road bikes in particular but a few people on here have posted pics of their pride and joy massively expensive bikes and I just think they are pig ugly normally due to the steep seat stays demanded by having a flat top tube miles away, just looks crap.

So why?

Just tradition and should be consigned to the history books or is there a compelling reason to retain it?

I was looking at my old Ribble (flat top tube) sat next to my Planet X (big slope) in the garage today and it really highlighted how st the Ribble looks, the Planet X is way more comfortable as well despite the Ribble being fitted and the Planet X simply being a medium off the shelf.

[Herman Toothrot]

TwistingMyMelon said:

I always thought The sloping top tube was designed in to accommodate all the old golfers that switched to cycling when it got popular as they couldn't reach the drops hence the phrase "sportive geometry "

Interesting, I'd not heard that reasoning :-)

Could have essentially the same placement of contact points with either setup, are sloping tube bikes shorter generally?

[Herman Toothrot]

Horizontal / Flat. That's just the thing though, I think the opposite and it just looks wrong / cumbersome.

[Herman Toothrot]

Sloping / Horizonal, why would you want the higher top tube, are there any advantages at all?

[Herman Toothrot]

I agree the Canyon looks dreadful but more due to the hump back top tube, OnOne do a MTB with a similar style frame it's called a Lurcher I presume after Adams family Lurch with the stooping hunched back.

Smaller frames must normally be stiffer, most flex you want to avoid would be twisting pulling on bars and pushing down with leading foot trying to twist the frame. A big open triangle with long tubes is sure to flex more than a triangle with shorter seat tube. Smaller frames have always been sold as the stronger choice for mountain bikes. Try snapping a broom handle - easy, then try and snap the shorter halves left over - really hard. Shorter means less leverage so stronger.

[Herman Toothrot]

upsidedownmark said:

Because the points at which you're flexing it from are 60cm apart, and that doesn't change - the 50cm triangle will have 10cm of extra lever, the 40cm triangle 20cm of extra lever.

Edited by upsidedownmark on Monday 30th March 13:36

But sloped top tube means same down tube and similar length top tube but shorter seat tube, out of the saddle climb or sprint (where you are exerting most force to notice any difference) your contact points are the same and leverage the same, nothing has changed as you are not sitting down. Horizontal or sloped are equal regarding leverage.. The only change is the junction to seat post and no ones levering the seat post at all, surely this makes the frame with the shorter seat tube (within reason not ladies drop) least flexible?

Trust me I'm not being awkward, I asked the question as I don't understand why the different choices are used.

So far I can see and understand horizontal is more aerodynamic for a cutting edge time trial bike, shorter tucked in seat stays are more aero, why curves maybe added. Regular road bike frame I still can't see a good arguement why horizontals used, you did explain why smaller overall may not be as stiff in all ways, but not specifically that horizontals stronger than sloped overall?

Trek Emonde or Madone = Sloped top tube
Cannondale Super 6 = Horizontal

So fashion or one right the other wrong?

Edited by Herman Toothrot on Monday 30th March 18:41

[Herman Toothrot]

gazza285 said:

Now apply the broom handle analogy to the 400mm seatpost on a smaller, sloping top tube frame.

And when you are sat down is when you are putting the least power through the system.