Metal/carbon frames

[rpm]

Seeing Kelly Bedford's new ti/carbon frame reminds me of some questions about frames that combine metal and carbon. Different makers put carbon and ti together in different ways. The Serotta Ottrot has carbon top tube, down tube, and seatstays with everything else ti. In contrast, the Seven Elium has a carbon seatpost and seatstays only. The IF XS just has ti lugs and everything else carbon and costs more than a Corvid. And the LeMond "spine" bikes had ti or steel downtube, headtube, and chainstays with the rest carbon.

What's the logic in all these different combinations? What does the combination of metal and carbon deliver that all-carbon or all-metal bikes don't? Aside from the fork, where would carbon seem to be most effective? For example, I associate carbon with stiffness and ti with compliance. So I wonder why somebody hasn't reversed the spine concept, using carbon downtube and chainstays for stiffness, and ti top tube, seatstays and headtube for comfort.

[cnighbor1]

I say they just combined them looking for weigth loss 1st If it worked that was OK

[SoCalSteve]

Seeing Kelly Bedford's new ti/carbon frame reminds me of some questions about frames that combine metal and carbon. Different makers put carbon and ti together in different ways. The Serotta Ottrot has carbon top tube, down tube, and seatstays with everything else ti. In contrast, the Seven Elium has a carbon seatpost and seatstays only. The IF XS just has ti lugs and everything else carbon and costs more than a Corvid. And the LeMond "spine" bikes had ti or steel downtube, headtube, and chainstays with the rest carbon.

What's the logic in all these different combinations? What does the combination of metal and carbon deliver that all-carbon or all-metal bikes don't? Aside from the fork, where would carbon seem to be most effective? For example, I associate carbon with stiffness and ti with compliance. So I wonder why somebody hasn't reversed the spine concept, using carbon downtube and chainstays for stiffness, and ti top tube, seatstays and headtube for comfort.

I don't have a clue behind any of the physics and/or logic behind why bike mfg's do stuff...

All I know is... I've owned many a bike and the Ottrott is the one I keep coming back to day after day, year after year. It is the smoothest, quietest, nicest riding bike I have ever ridden, bar none!

Oh yeah, and Kelly Bedford designed it, btw.

[eddief]

has an interesting approach as seen when you scroll through his gallery. think he makes a whole bike outa steel and then cuts it up to input the carbon top and seat tubes:

http://www.rexcycles.com/gallery/

i heart the redish one towards the bottom.

[ORMojo]

The IF XS just has ti lugs and everything else carbon and costs more than a Corvid.

Just to be precise, the XS has Ti lugs, headtube, bb, and chainstays. Like SoCalSteve's Ottrott, it is the one I keep reaffirming as my favorite, and I really think the combination of materials is masterfully done and makes a significant difference. (Although both I and my wife are searching for an Ottrott to check it out!)

I say they just combined them looking for weigth loss 1st If it worked that was OK

I think there was/is a lot more to it than that.

[charliedid]

IMO it's a bunch of "because we can" and we like the way it looks going on. If you have ever seen an IF XS in person, the bike is rather striking.

Sometimes it's okay just to build something beautiful and really really cool.

This is that.

[jr59]

So they can sell more bikes!
It gives their customers something to want.

If you think about it. How many custom bikes can you have without duplicating a few?


As some body on a forum said, the only 2 things that a bike can sell in todays market is price and weight.
I would add custom fit, and it seems different combos of Ti and CF.

[rpm]

The Rex steel/carbon frame is interesting. I'm wonder why there haven't been more steel/carbon frames, trying to combine the feel of steel with the lightness of carbon. My CDA has carbon seatstays and it rides very well, but I don't know how much of the ride is attributable to the carbon.

[jr59]

I tend to think Holland's exo-gride has the best of ideas in this.

But there again, I have no idea why I think that!

http://vimeo.com/26685582

[Nelson99]

I have two mixed material bikes. For reference I also have all steel, all carbon, and all titanium bikes.

The two mixed material bikes, a Giant aluminum/carbon frame, and a LeMond Ti/carbon frame both have a very well damped ride, perhaps more damped than my all carbon Spec Roubaix. They are both "spine" designs, with metal HT, DT, and chain stays, carbon seat stays and TT. The seat tube is carbon on top, metal on bottom.

I'm no material scientist, but my understanding is that vibrations propagate very poorly through unlike materials.

As for ride quality, the Giant rides like a bobsled, very stable and fast. The BB is a huge chunk of aluminum. I vastly prefer the ride of this frame to the all aluminum bikes I've ridden.

But, the LeMond is the keeper. Right now it is my favorite bike. It is responsive, nimble, stable, and gives good road feel, but has that magic carpet ride. It's a really nice frame. The only frames I've ridden that come close are my Tommasini Diamanté (rings like a bell, very different feel, but awesome), and my Strong (stiff and razor sharp, but not at all abusive). Another great frame is my friends Litespeed Tuscany. I can only assume a Serotta Ti frame would be even nicer.

At the end of the day, I think that mixing materials gives the frame a very different feel from either material alone. The question is, do you like that feel better?

[rpm]

I'm no material scientist, but my understanding is that vibrations propagate very poorly through unlike materials.


I'm no material scientist either, and I didn't stay in a Holiday Inn, but that idea makes sense to me. If I were looking for a new bike, I'd certainly take a hard look at that Bedford, especially since it's $2,500 cheaper than a new Ottrot.

[fishbolish]

scapin has been doing the mix for years..

[killacks]

MMA vs. MMB showdown :bike:

[Mike748]

The original premise of the Ottrott was to take the great ride of the Legend and improve the torsional stiffness of the frame by substituting carbon tubes in the DT and TT. This also allowed for tuning of the stiffness as the carbon tubes could be varied more than Ti tubes could. At least that's what I remember from the original press release a decade ago.

[Grant McLean]

What's the logic in all these different combinations? What does the combination of metal and carbon deliver that all-carbon or all-metal bikes don't? Aside from the fork, where would carbon seem to be most effective? For example, I associate carbon with stiffness and ti with compliance. So I wonder why somebody hasn't reversed the spine concept, using carbon downtube and chainstays for stiffness, and ti top tube, seatstays and headtube for comfort.

There are a few overlapping reasons for mixed materials, most of them
are related to the legacy of manufacturing, and an approach to design
geometry, not just ride qualities.

It helps to understand the construction mixed material frames as an evolutionary
step from full metal to carbon frames, as the brands doing mixed materials
generally started as metal fabrication, and that legacy has influenced their
decision to include metal for durability sake, to address the shortcomings
of carbon as a material.

Any frame design has to hold the tubes together, as well as integrate the
components to the frame, at the headset, bb, seatpost, and drop outs.
Many early carbon frames had aluminum or ti pieces bonded on, like
inside the head tube. A threaded bb can't be made from carbon, so
an insert is glued in. Where does that approach end? How much metal
is worth it? At some point, joining tubes with metal lugs is not the most
efficient. PF30 bb's don't need a metal structure the way threads do.

As carbon tube to tube construction developed, and the ability to join more
and more complex shapes and higher modulus carbon has become available,
mixed materials frames have fallen behind. There are simply lighter and
frankly better ways to stick tubes together than being restricted to metal
shapes.

It's sort of ironic that's how far carbon has developed, that a
mixed material process was originally pursued because it was that is much
more flexible than monocoque construction, the early alternative. But now,
tube to tube construction allows more sizes and shapes of tubes to be joined
than mixed materials. For certain, made to measure custom geometry
has been a large part of the reason mixed materials has survived as long
in the market has it has.

-g