Low end Carbon vs High end Aluminum - Page 2

The LeMond Tourmalet came with mostly Shimano 105 components, right? Those should serve you well even it you start racing. If you want to upgrade a little - maybe a better set of wheels. If you do start racing then you might be glad that you're not on an expensive bike.

If there's anything specifically that you need to change for comfort, like saddle or handlebars then that's a pretty easy thing to do but that Tourmalet seems like a pretty good bike as is. The only thing I find offputting about the LeMonds is the seat angles in my size. I can't get comfy on a 72.5 degree seat angled frame...

It depends just how low the Carbon frame is and how high the alloy frame is.

Generally Carbon would win, it also depends on the gruppo that comes on the bike too (and wheelset of course).

The 4.7 uses Trek's new TCT Carbon which, although is not hand made like it's higher end OCLV and Red carbon, it still rides amazing.

Carbon is stiffer that alloy, more malliable and has a natural ability to dampen road shock. The directional nature of carbon also means they can build in compliance and stiffness into the same bike. Alloy does not allow a frame builder to make a bike laterally stiff while vertically compliant as well as carbon does. You'll see that there is a big trend in carbon bikes now where top tubes are flattened off and are often wider than high. This builds in that vertical compliance along with lateral stiffness. You just can't get that so easily on alloy framesets. Oversized bottom bracket clusters are another thing. How many alloy bikes have over sized b clusters? None that I know off! This is so important for power transfer, along with oversized chain stays.

You can make the thickness and diameter of alloy tubes thicker and bigger to allow them to be as stiff as carbon but that would make the ride too harsh, so they don't.

Alloy will always be a rougher ride than carbon. Carbon absorbs vibration. With the right engineering you could make a bell out of plastic that is as strong as an alloy counterpart. The plastic bell would not resonate so well. That's plastic's vibration absorbing quality. Carbon is similar in that way. Go to your local bike shop and flick the alloy frames and the carbon frames. What one resonates less and absorbs the most vibrations, and also sounds somewhat plasticy?

If it's a choice between an alloy frame with a certain gruppo and a carbon frame with a slightly downgraded gruppo I'd generally choose the slightly downgraded gruppo with carbon frame. If it's a massively downgraded gruppo then that's a different issue.

Also worth remembering is that trek offer a limited life time warrenty and crash replacement programme on all their carbon frames.

I'd say carbon for the win, even TCT carbon.

First off, let me state I am speaking from my own personal knowledge and use of a relatively low grade carbon frame (Pedal Force QS2), low grade aluminum frame (Airborne thunderbolt), mid-high grade aluminum frame (Giant TCR Aero), and high-end composite frame (Cannondale System6).

Ian, you make some broad-sweeping generalities that, in my experience, are not correct in all situations - and I have bolded those above. There are some grades of carbon that are stiffer than the available alloys most frequently used from bicycle frames, but not all. The Pedal Force frame I had was the 2nd most flimsy in the BB area frame I've ever ridden (won't disclose the most flimsy, but it wasn't a household brand).

Are you aware of hydro-forming? There are some pretty amazing things that are being done WRT aluminum shaping. I think it's a bunch of marketing hocus-pocus, but there are many out there that believe in the 'vertically compliant-laterally stiff' phenomenon. Because I'm ~200lbs, I want stiff, with an extra helping of stiffer. The flatter and wider tubing has long been done with aluminum tubing - my Airborne frame has it as does my Quintana Roo Kilo (2001 vintage) TT frame. Further, the Kilo frame is Quntana Roo's low rung frame, so shaped aluminum can be had quite readily.

Oversized BB clusters? Ever take a look at Cannondales????? They started (I could be wrong, but not by much) this business of the oversize BB cluster - and with aluminum to boot! Their downtubes are narrower at the head tube and expand considerably at the BB. Lastly, my Cannondale does not ride "too harsh". How can you generalize for everyone and every body in that manner? You're aware that "too harsh" is a relative statement, right?

"Aluminum will always be a ride rougher than carbon". Ever ride a carbon Kestrel Talon??? Neither have I, but from what I've read about those teeth-rattlers I want one right away! Apparently they have my kind of stiffness!! I would venture to guarantee that they ride rougher than the Giant Aero that I have and its aluminum - go figure...

I'm no expert in metallurgy, or on carbon's physical properties. I speak soley from experience. I felt it apropro to challenge the broad-brushed statements you made about the frame material I prefer - aluminum baby!

yes, you're right. Not ALL carbon is better than alloy. I'm speaking on the most part. But generally bicycle grade carbon is stiffer that alloy. The lay up sched plays a part too, of course!

Yes, I am aware of hydroforming. Scott do this pretty well. I don't doubt that hydro forming is a successfull way of shaping alloy tubing but I still maintain that carbon is much more maliable than alloy. This is why you find all sorts of weird and wonderfull tubing shapes on carbon bikes vs. alloy (on the whole). Bianchi (c2c alloy range) of course use hydroforming too to shape their tubes along with scott but this is only at the front end. The rest is not a monocoq construction, it's welded (this is for both bianchi and scott). To hydroform a full bike would be too costly and un-appealing to the bike market.

I was not aware that cannondale did any BB clusters that were oversized untill their full carbon bikes hit the market (the super six, system six and six range). What model was this on?

I know the range all the way upto their six13 range back in 2005 and only in 2007 did they do oversized BB clusters. That's because they moved into full carbon. They never did this (to my knowlage) on bikes that had an alloy centre tube. Nor have any other brands. You told me that cannondale have down tubes that are wider at the BB end vs. the head tube. That's referring to an oversized down tube (or at least in part) not an oversized BB cluster. And still, to the best of my knowlage this never did this on bikes that had, at least partly, alloy down tubes (six13).

The reason you don't find (and still don't - TO THE BEST OF MY KNOWLAGE) oversize BB clusters on bikes that are full alloy or at least either side of (and including) the centre tube (six13 for example). Is that the overall surface area of the BB is directly affected by the diametre of the alloy tubing that connects to it. It's mighty hard to make a BB cluster that is proportionally bigger that the tubing that feeds it. This would involve some seriouse hydroforming and again is too expensive to be appealing to the market. You simply can't make an oversized BB (without oversize down tube, centre tube and chain stay) with traditional welding. Well you can, but you'd have to weld on extra alloy - pointless?! You'd have to mold it into shape really, that's why you find oversized BB clusters (MORE OFTEN) on full carbon bikes than alloy bikes.

The flattened top tube is engineering basics, vertical compliance vs laterral stiffness is true. It is not a falacy of any nature. It is factual based engineering that is, in turn, governed by physics.

I have been working in the bicycle business for many years, and riding for many years more. I've even had SBCU take me to their head office for a few days to show me their tricks. While I admit this was partly propoganda to tell me how good spesh are vs. other brands I agree with their views on carbon vs. alloy and the shaping of the tubing that is used.

When we're talking alloy vs. carbon. even TCT vs. FGlite alloy then carbon is still better ino.

When I apeak of anything above, I obviously speak in relative terms and on a weight of weight comparison. I assumed that was needless to say. Sorry, maybe I should have made that clearer.

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