Colnago Double Down Tubes?
 

http://www.chariandconyc.net/blog/wp.../dsc_04797.jpg

why?

It's got nothing on this waste of time
http://cdn.mos.bikeradar.com/images/...1p0-798-75.jpg

I nearly bought one off craigslist last year. If that's the same bike I was looking at, it's a titanium frame. They were experimenting with them sometime during the 90's. Very neat, but far from traditional. Not sure what the technical reason is for the double downtube. Maybe they found it easier to form a pair of light/strong thin tubes vs a single, fat downtube?

What's the problem here? The rear stays not being linked to the top tube? I'm not very familiar with FS bikes

Presumably an attempt to make a bike that is horizontally rigid and vertically compliant.

However, the approach is doomed to make a heavier bike (at least for a given amount of stiffness) The whole reason bikes went to larger tube diameters is that you can increase the strength of a tube, and decrease it's weight by increasing the tube diameter, and decreasing wall thickness (up to the point you start having a "Beer Can Effect" problem.

So the dual downtube approach replaces one light tube with 2 heavy ones.

Also, it gives you less space for the weld surface connecting each of the 2 tubes to the BB shell, an area where the dual down tube Ti Colnagos were reported to have failure problems.

Mostly an attempt by Colnago to do something to standout which was not very well conceived or executed.

Look at the other end of the bike.

Hey man, I love my HeadShok, and I've heard the Lefty is even better

No pedals. Ya can't pedal the bike without pedals!

i had this one
http://1.bp.blogspot.com/_I4Snyzw2IM..._carbitubo.jpg

I don't get the point.

Wasn't it called the Bi- Titan? It was cool looking during that time though. Probably ill-concieved,
because no one else did anything like it, right?

Leftys allow you to change tubes without removing the wheel from the bike.

Looks like they just had some left over mixte tubes.

Either that or the Bi Titanio. Tony Rominger rode that frame--possibly during his win in the '95 Giro d'Italia, or perhaps the year that he stood to the right of Miguel Indurain on the podium at the Tour. Possible both, but I don't feel like digging through my VCRs right now.

As a designer Ernesto Colnago had an almost fanatical desire towards innovation, in eliminating power loss due to frame flex. Look at the number of custom proprietary tubesets he had designed and manufactured by Columbus over the years, made especially for his own marque. I know that the Bi Titanio, a frame I lusted but couldn't afford, did for a time have some durability issues. Who knows, it could have been that the double downtube was a strategy to overcome the lack of an easily available variety of appropriate shaped tubing, something that is easily available today but not so much back then? On the other hand, style and esthetics have always been a strong element that he incorporated into all of his top frame designs.

Should appeal to a major segment of the Colnago customer base "biker dentist".

The point on the oversized tubes is the key. manufacturers have tried this with parallel top tubes and had no determinable benefits.

The real test is the UCI. If this is really advantageous then the Luddites at the UCI will ban it in a heartbeat.

Thanks for your indepth review and explanation of the pros and cons. :)

The carbon version, right? Wasn't that his first carbon frame?

Longer suspension travel and decreased friction are the actual reasons.

http://alptown.com/cycling/India.ReinforcedBike.jpg

Pros: Very strong. Handy if you weigh a lot, need to haul a load of bricks or have a bunch of kids

http://alptown.com/cycling/India.HaulingBricks.jpg http://alptown.com/cycling/India.CycleSchoolBus.jpg

Cons: Heavy. Makes everyone think you are a Fred

also in a muddy (read cement mud) xc course, the guy with the lefty was king, as he didn't have to stop and get the mud out of his front wheel/fork crown

http://www.bikesdirect.com/products/...s/IMG_5039.jpg

I don't understand why this is a trend...

The top tube one above the other is just retro chic, see Pashley etc.

The bike I saw had twin toptubes side by side. I'll try to dig up the review. Concluded that the frame was not as stiff as with one oversized tube and for the bling you had to pay a weight penalty.

Lighter, too.

Total Freds right there. Look at that guy with the cart, a Fred WOULD do that.

So it doesn't make it lighter or easier to fix a flat?
Those are still reasons, even if not the primary intention.