what is "colorado concept"? or what exactly do the tubes on a CSI do?

[tylercheung]

Just wondering - there's a lot of talk about "colorado concept" tubing, but nothing that really explains what it is. Is it a sort of internal standard/specification/platform for tubing for serotta steel bikes? Are there any particular advantages over the stuff you can get from columbus/reynolds/etc?

i.e. (ulterior motive... ;) ;) ) for the fancy butted, curvy, tapered, coke bottle tubes on a typical CSI - what exactly is better than, say, another well built lugged frame that doesn't have the fancy tubes? Does it ride dramatically better in terms of being cushier, zippier, etc etc or is it more of a subtle difference?

[Ahneida Ride]

The tubes are tapered ...

That is, the outside diameter changes along the tube.

The thickness of the steel changes too. ( double/triple butting).

Theory is that the tube can be stiffer where it needs to be.

Does it work ? ride one. You decide. ;)

[tylercheung]

I snuck a ride on one at TiDesign's store but I'm not good enough to tell! I need to ride more hours i suppose. It was pretty nice though...

[victoryfactory]

That's right. Back in the days of steel onlythere was very little tube
shaping. If you look carefully at a CSI, the top tube is fatter where it
attaches to the head tube and the seat and down tubes are fatter
where they meet the bottom bracket. The Atlanta was similar but had
a straight TT (cheaper model)

A very elegant design, I think. They still do it on the legend Ti.
I watched the process once at the factory. They jam a tapered die
into the tube until they get the shape they want for a particular build.

Very hands on craftsmanship that most people aren't aware of.

Poured rain all day in Moab, I head home tomorrow.

VF

[Peter B]

I think the intent is to enhance engineered stiffness, particularly at the bottom bracket, hence the larger tube ends at that junction (DT/ST to BB). Butting strategically reduces wall thickness for weight savings and, reportedly, to tune handling/feel characteristics.

I've had two Serottas, an early 90's lugged steel Colorado II (gone now) and a 2003 Legend ti which I still ride as my go to geared bike. Both handle well and are plenty stiff. But bear in mind I am 150 in the saddle.

Serotta makes an excellent bike; just find the one that fits your body and cycling needs/goals.

[Peter P.]

I believe the Colorado Concept came about when Serotta was designing frames for the U.S. Olympic team, back in the 80's.

They were building frames with very short chainstays and needed a solution because riders' heels were hitting the stays. They put that sexy curve in the chainstays and besides providing heel clearance, they discovered it supposedly stiffened up the rear end as well.

The idea later evolved to flaring the downtube and seat tube to their diameters increased near the bottom bracket, imparting further stiffness in that area.

Whether it works or not is for the marketing people and engineers.

It does look cool, though!

[jsfoster]

While riding those 1970's bicycles, hard, I would look down in amazement at the bottom bracket moving left and right as I pedaled. Pedaling standing, uphill, where there is tremendous stress on the bike (and rider), the BB area seemed to go back and forth the width of itself or more. One knows that the power to the wheels goes through a lot of stuff before it gets to the wheels, but to have it just moving back and forth is a obvious waste of energy. The 'Colorado Concept' simply uses material size, in this case tubing diameter, to help keep the energy moving in the direction of the wheels most efficiently. (In a building, the same weight/foot of steel beam will spam a longer distance or carry a greater load if the steel is configured in a more vertical configuration.) This, precise tubing size application is trying to do the same as lots of other builders of the earlier 20th Century using double tubing in different places to increase stiffness. It is a solution which is so obvious that it is difficult to understand why it took 100 years of two wheeling to actually build the bike like that. I am sure it is more expensive and labor intensive, but it makes a bicycle so much more solid, stable and, I believe, more respectful of the rider up those hills.

[bagochips3]

The story I heard was that Ben was flying over Colorado and noticed the trees. The tops of the trees moved relatively freely in the wind, but the trunks remained motionless and stiff. So he got the idea to shape the tubes more like the trees: thicker at the bottom for stiffness and thinner at the top for compliance. I don't know if this story is true or not, but it sounds good to me. :)

[Keith A]

Check out the '89 catalog from Serotta that is available here (http://bulgier.net/pics/bike/Catalogs/Serotta-89/Serotta_Catalogue.pdf). They have some good information in there about their tubing design.

[Spinner]

changing the external diameter of the tubes is called swaging. thinning the walls of the tubes is called butting. the right combination of these metal working options yields a frame that performs exceptionally well and looks cool. it's the tubes, damn it.

[benb]

While you are at it can anyone explain what "CSI" stood for?

edit: That old catalog is great... love the goofy 80s helmets & the ancient macintosh...

[54ny77]

That's such a cool story I'd hope they stick with that one. :)

Sounds a helluva lot better than all the other marketing hype out there.

The story I heard was that Ben was flying over Colorado and noticed the trees. The tops of the trees moved relatively freely in the wind, but the trunks remained motionless and stiff. So he got the idea to shape the tubes more like the trees: thicker at the bottom for stiffness and thinner at the top for compliance. I don't know if this story is true or not, but it sounds good to me. :)

[c-record]

While you are at it can anyone explain what "CSI" stood for?

edit: That old catalog is great... love the goofy 80s helmets & the ancient macintosh...


Colorado Steel Intelligence rings a bell but I may be off.

Yes, the CSI is one fantastic riding frame. Put an F1 on that thing and I wish I had mine back!!

[Mike748]

While you are at it can anyone explain what "CSI" stood for?

edit: That old catalog is great... love the goofy 80s helmets & the ancient macintosh...


I've wondered that myself... since it evolved from the CRL (which maybe meant colorado light). My best guess was Club or Colorado + Sport or Special + something with an i.

[c-record]

We could have a Serotta and cycling history quiz on this forum. I think we've got some pretty sharp tools here and I'd get smoked.