I'm in the market for a high-end carbon bike. Until now, I've always ridden steel. I mentioned to an experienced rider/racer that I was considering a custom frame made with carbon tubes and titanium lugs. He winced, saying that mixing those two materials negatively affects a bike's handling, as they flex differently. He said I may find cornering squirrelly. Any thoughts?

I wouldn't worry. Mix 'n' match has been done in the past by Cannondale and Trek (aluminum frame, steel fork), Raleigh USA (Technium, aluminum main frame bonded to steel rear triangle, steel fork), and likely others. As long as the designer knows what s/he is doing, it shouldn't matter.

I seem to recall that one of the major makes used either aluminum or titanium internal lugs in their original carbon bikes.

I doubt mixing materials would negatively affect handling at all. What I would be concerned about is how the bonding of the dissimilar materials will hold up over time.

The coefficient of expansion difference (with temperature changes) between the two materials may be significant enough to have an effect on the strength of the bond between the Ti lugs and the CFRP tubes depending on whether it's purely adhesive or is both mechanically and chemically bonded. This has been a problem on some early frames using CFRP tubes and aluminum lugs as the frames have aged.

Nothing inherently wrong with "mixing", but this is pretty esoteric construction for a one-off frame. Are titanium lugs readily available? You (or your framebuilder) would certainly want to be completely up to speed on appropriate techniques and materials for fitting, gluing, etc., particularly bonding techniques between titanium and carbon. I certainly would want to be on a trodden path with this, not doing something for the first time. Lugged carbon tubes have been done occasionally in the past, but seem to have completely fallen out of favor vs. molded carbon.

I'm curious why you want to do this. I would think it would be very hard to match the performance, weight, and durability of any number of off-the-rack molded carbon frames currently being sold.

- Mark

Ti lugs are welded up and then the tubes are bonded in. There are a number of people that make Ti frames that add carbon this way, the idea that it would affect handling negatively is a bit uninformed. It's the kind of nonsense passing for knowledge that drives me nuts about the cycling community. Lots of people love their Serottas that were built this way

Carbon and Ti is the most sensible combo for carbon to metal joining.
Your friend is just speculating. Higher end frame materials are never so different that they clash so badly.
Carbon frames are often built with such differences in wall thicknesses over the frame that for all intents and purposes they might as well be made of different materials.

Handling is a product of the bicycles geometry, and materials. Basically design and engineering. If you are competent in both fields, you can make a great handling bike with any number of materials and combinations thereof. This is just an uninformed opinion (or at least an opinion based on very dated information).

Your friend was mis-informed, and probably should have kept his opinion to himself. Early on there were issues with carbon tubes bonded to steel, aluminum, or stainless "lugs." The problems weren't handling- until the joints un-bonded. Then the frame got a little loosey-goosey.

Are you looking at Firefly's Carbon-Ti roadbike? Drool...

I'm considering the Seven 622 SLX Seven Cycles | 622 SLX My friend is a bike shop owner but also a very experienced racer.

Mostly for fit. My proportions are so unusual that my other custom bikes have a 60 cm seat tube and a 56 cm top tube. My inseam is 34 and my sleeve length only 32. (I don't look freaky, really.) I also do not have great lower back flexibility. I had a Retul fit that confirmed that an off-the-rack bike may be hard to find. That said, a Colnago CX-Zero, its top of the line "endurance bike," has a very tall stack and a short reach that may serve me well.

The problem is, of course, LBS don't stock high end bike like the Colnago, so I have to buy it before trying it. Yet, I'm leaning toward the Colnago because the LBS has said that if I don't like it, he's willing to take it back because the size is one he can sell. In that case I'd go for the Seven, which does have a guarantee that if I don't like it, they'd build me another one until I was happy. I's impossible to try a custom frame beforehand, of course, but with that kind of guarantee, I feel pretty confident I'd be happy. The Seven bike is here: Seven Cycles | 622 SLX

Back in college, the local bike shop had a frame hanging on the wall.
The bikes owner had come bombing down a steep local hill, and on the railroad crossing at the bottom, the CF downtube slipped off the lug at the headtube. The toptube kept the bike in one piece, but it was a really spongey ride.

Just looking at the 622 SLX, Seven has provided a substantial length in their lugs for the carbon tubes to have a very large bonding surface area, so in my mind that's a good thing. There's nothing I've found so far either on the Seven website or in various published reviews that discusses the actual bonding agent, though.

Plenty of outstanding epoxies out there for that type of bond. Many frames have carbon rear triangles glued onto an Aluminum or steel front triangle.
3M DP 460 is a common bonding agent and has outstanding properties for this type of joint.

Other than cost, I don't see how you could go wrong with that Seven. They know what they're doing.

- Mark

If I were in the market for something in the 622 SLX price range, I'd at least consider the Holland ExoGrid which more fully integrates the Ti and CF. The Ti grid also offers some protection of the carbon tubes from impact damage.

Holland Cycles ExoGrid

The glue is less important than the surface prep. Titanium is extremely difficult to bond well unless you have access to specialist surface treatments like plasma electrolytic oxidation.

That is ridiculous. Frame design is all about ensuring that materials flex differently. So triangulation of a frame causes the ends of the tubes to flex differently. More to the point carbon forks, in wide use generally have aluminium steering tubes, etc...

If you need custom, I would probably stick with steel with lighter components, like the a carbon fork. Rob English does some cool stuff, and there are the bolt on carbon rear ends. No experience with either though. I don't think it is the frame material that is holding back most riders. Lighter weight helps of course.

Custom Superlight Road bike V3 | English Cycles

more fully integrates the Ti and CF. The Ti grid also offers some protection of the carbon tubes from impact damage.

Holland Cycles ExoGrid

Coincidentally, my two custom steel bikes were built by John Hollands of Reisterstown, Md. He may not be well know throughout the country, but on the East Coast most frame builders know of him. John Hollands Bicycles | England native named Hollands makes bicycles that do America proud Reisterstown shop a mecca for cyclists - Baltimore Sun

It not only weight but rigidity that has me looking at a new bike. And frankly, living in Florida and sweating as much as I do, steel frames are hard to maintain. Eventually--and usually sooner rather than later, they start to rust. What has impressed me about newer bikes are the big and rigid bottom brackets that help power transfer go from legs to straight line instead of flexing too much.

I'm pretty sure the Seven 622 has Ti chain stays and carbon seat stays.

Poor handling frames at that price level should never have left the Shipping Dock .

Not stainless. At 1650g this 61cm 953 frame is pretty light, too. With OS tubing and the right chainstays, it's plenty stiff.

I grew up in Duval County not far from the beach, so I know what humid salt air can do to a steel frame.

KVA sells stainless tubes in a wide variety of tube diameters. Although cost shouldn't be the only factor, if XCR or 953 bikes are beyond the budget, KVA is less expensive and might work out. I think they have a list of builders on their website.

That's not relevant to my point. One section still has to be bonded to the other.
I wonder if the OPs friend would say that a bike with carbon stays would also be squirrely?