For the engineers: What is the deal with Bi-Ovalised tubes?

The Merckx leader has them, Chris’ Kypo has them and the Felt TK2 has them… So what’s the deal with Bi-Ovalised tubes? They look pretty damn hot, but do they do anything other than stand out visually?

They are supposedly more aero and stronger than round ones.

These guys might have some thoughts as well

That begs the question: When was the last time anyone heard of a tube buckling under the weight and/or strength of a rider? My way of thinking is that if you really wanted to add strength to a part of a frame that needs it, you’d put some lateral gussets near the BB, thus reducing flex under power.


Not sure about road bikes. However in the mountain bike world, back in the day (90s) when manufacturers had started tinkering with alloy, and a few frames would snap and shatter as alloy does (not as flexible as steel was) many a bike begun sporting the massive Bi-Ovalised triple and Double butted tubes. My 1991 cro mo tequesta frame has them a plenty. Strength and stiffness to weight ratio were the selling points.

Ryan Leech in “Evolve”. Bent his top tube with his balls when he landed on it (not very hard mind you … the landing that is … and no smart arse comments from you CraigC) going for a gap to handrail.


Hardly representative though Des.

Ryan Leech apparently has large solid balls. But you’ll have to ask CraigC for confirmation on that.

I not aware of said ‘balls’, but this guy might know something

this guy has done plenty of experimentation of ‘ball’ whacking top tubes, I would suspect.

Ahhhhh! nutz…(it’s a pun, get it) :smiley:

Not by me. I don’t censor on the grounds of bad taste.

Back to the question at hand, It is just another way of trying to get the right balance beteween strength/stiffness/weight in the tubes and joins.

Thinner walled tubes of the same material need a larger diameter to take the same load, if you horizontally ovalise at the BB, vertically ovalise at the head tube and transition in-between then you achieve the same thing without having to join coke can looking tubes to smaller head tubes and BB shell.

Think early Cannondales for round tubes, very messy. gussets = weight (more material)

the orientation of the ovals also helps the stiffness needed at those joins. like an egg ovals are very strong through their long axis and you also get a lot more length of weld across the BB shell to resist the forces of pushing down alternatively on each side.

how’s that??

Thanks!! My bi[oval]-curiosity is waning.

Mostly it is get extra weld length but Crashdummy has just about covered all the details (most of it is effectively marketing hype). I’d guess that this is part of the reason that headtubes keep getting wider.

Personally, I already rub paint off top tubes, so the currently fashionable bikes with stupidly large top tubes aren’t desirable. Does everybody else pedal like a cowboy or is that balls photo applicable?