Thoughts about humpbacked top tubes

[bicycletricycle]

My sense of it is that bicycles are very rarely “engineered” in the ways people might expect. Just like how jury’s are disappointed in the lack of forensic analysis in real court cases. Most of the design of bicycles is driven by tradition (fitting in with or reaction against) and aesthetics (fitting into the new style or pioneering a new one). I think most of the “engineering” comes when something goes wrong (won’t pass test, problems field testing, etc.) and is mostly done through simple iterative trial and error testing.

Nobody is starting a from a clean sheet using engineering principles to design the most perfect bicycle. Even more confusingly if someone did we probably wouldn’t like it. Even stranger is the fact that if we aren’t comfortable on a bike, for any reason, it will be a lower performance bicycle.

This leaves the consumer and designer in the dark. They both want something new but not so new that it is “ugly” or confusing. We want comfortable changes that feel justified but don’t look or feel too different from our idea of what we want.

The bowed top tube may or may not have some effect on frame performance, however, that isn’t why it was designed that way and that isn’t why you will buy it.

As an example. People are still arguing about compact frames and that is a pretty simple thing to understand the benefits of.

I have been designing my next bike for a while now and I am thinking of a bowed top tube for basic geometric reasons. I want a small headtube with 2 bottles on the down-tube and a lot seat post showing for free suspension. The bowed top tube will clear the top of the front bottle then curve down for a more compact seat tube. The twin six has a double bottle downtube, maybe they did it for the same reason.

[pasadena]

[Bici-Sonora]

Originally Posted by bicycletricycle

I have been designing my next bike for a while now and I am thinking of a bowed top tube for basic geometric reasons. I want a small headtube with 2 bottles on the down-tube and a lot seat post showing for free suspension. The bowed top tube will clear the top of the front bottle then curve down for a more compact seat tube. The twin six has a double bottle downtube, maybe they did it for the same reason.

Okay, this makes sense. I have 2 top side DT bottle mounts on my Jones and like that configuration. However, with Twin Six, their steel bike, without the bowed TT, also has the two downtube bottle configuration. On big sizes, I think it is relatively easy to get the two bottle on the DT. On smaller frames, the bowed TT might help more.

[bicycletricycle]

Originally Posted by Bici-Sonora

Okay, this makes sense. I have 2 top side DT bottle mounts on my Jones and like that configuration. However, with Twin Six, their steel bike, without the bowed TT, also has the two downtube bottle configuration. On big sizes, I think it is relatively easy to get the two bottle on the DT. On smaller frames, the bowed TT might help more.

Maybe they needed it for small sizes so they just did it for all of them? Also, some bikes with this configuration don’t work with double big bottles so maybe that was an issue? Or maybe they just thought it looked cool.

[Steve in SLO]

All quantifiable explanations aside, from pre-war balloon tire bikes to Retrotec/Inglis and Blacksheep bikes, sometimes arced top-tubes just look great.

[sokyroadie]

Originally Posted by Bici-Sonora

So, if there is no meaningful flex to the TT on account of the humpback, we are back to simple aesthetics: is it pretty, ugly, or an acquired taste?

I like it and ordered a Dean Ti frame with the curved TT.

[bicycletricycle]

100% agree

Originally Posted by Steve in SLO

All quantifiable explanations aside, from pre-war balloon tire bikes to Retrotec/Inglis and Blacksheep bikes, sometimes arced top-tubes just look great.

[Hellgate]

Originally Posted by Monsieur Toast

In case anyone is wondering what the bike in question looks like ...

Bleach

[charliedid]

Originally Posted by Steve in SLO

All quantifiable explanations aside, from pre-war balloon tire bikes to Retrotec/Inglis and Blacksheep bikes, sometimes arced top-tubes just look great.

So true

[happycampyer]

I always liked how the arc the toptube of the Fast Boy TF5 continued down the seat stays:

[charliedid]

Originally Posted by Hellgate

Bleach

So you getting one?

[Bici-Sonora]

Originally Posted by weisan

Thoughts?

I don't overthink, I just ride. It's fun!

A rare sighting of the double humped top tube! Your bike is pretty cool.

I know I'm overthinking this x10, but it is kinda fun on a rare rainy day here. And, I've got the willing help of friendly enablers here.

[Bici-Sonora]

Originally Posted by happycampyer

I always liked how the arc the toptube of the Fast Boy TF5 continued down the seat stays:

Now that you've pointed that out, I really want the arc of the Twin Six to continue down the seat stays! Damn you man!

[William]

If you don't like the curves, then don't check out this thread...

https://forums.thepaceline.net/showthread.php?t=123274






W.

[Hellgate]

Originally Posted by charliedid

So you getting one?

You a funny man. Very funny man.