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Carbon always stiffer than Alloy?

h14turboh14turbo Posts: 329
edited September 2009 in Workshop
I am interested in getting a carbon frame, but am wondering is a low end-ish carbon frame, i.e. planet x, going to be much stiffer than the frame on my current specialized allez? Cheers

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  • redddraggonredddraggon Posts: 10,862
    No
    I like bikes...

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  • Takis61Takis61 Posts: 239
    Sorry reddraggon, but yes.
    I haave a 2003 Allez & a new Ribble Sportive. Definitely more flex on the BB area on the Allez, also ride quality & smoothness miles better on the carbon.
    One cost me £400, with a later carbon fork upgrade, the other cost £1000 - and it shows.
    My knees hurt !
  • skinsonskinson Posts: 362
    NO

    Oh yes I forgot it's the chief metallurgist to king Philip of spain speaking.
    Dave
  • redddraggonredddraggon Posts: 10,862
    Takis61 wrote:
    Sorry reddraggon, but yes.

    Obviously you know nothing about materials if you say that.

    He asked if CFRP is always stiffer than aluminium alloy, which it isn't.
    I like bikes...

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  • majormantramajormantra Posts: 2,094
    Takis61 wrote:
    Sorry reddraggon, but yes.

    Obviously you know nothing about materials if you say that.

    He asked if CFRP is always stiffer than aluminium alloy, which it isn't.

    +1. Many carbon frames will be stiffer than the Allez but there's nothing magic about the material and the geometry and tube design make all the difference.

    Matthew
  • bill57bill57 Posts: 454
    Funny, people used to think the steel vs. alloy division was bad; they had no idea what was yet to come.
    Why don't you just ride your bikes and enjoy it? This current "stiffness" obsession is just such a load of bollocks.
  • freehubfreehub Posts: 1,447
    My CAAD9 is alloy and feels really stiff, I can't see all carbon frames being stiffer than it, lighter, but not stiffer, maybe a really good one yea.
  • System_1System_1 Posts: 513
    Takis61 wrote:
    Sorry reddraggon, but yes.
    I haave a 2003 Allez & a new Ribble Sportive. Definitely more flex on the BB area on the Allez, also ride quality & smoothness miles better on the carbon.
    One cost me £400, with a later carbon fork upgrade, the other cost £1000 - and it shows.

    Bollocks. I bought a Kinesis KiC2 that's much stiffer than the Prorace carbon frame it replaces and it's just as comfortable and lighter too. Carbon fibre isn't some kind of wonder material that automatically makes a better bike.
  • nicensleazynicensleazy Posts: 2,310
    I see a planet X up close the other day, Got to say, for the money, they appear a great bike and the carbon finish is great!
  • WamasWamas Posts: 256
    Aluminium is stiff than carbon, but the stiffness of the bike is not just to do with the material it is made with, but how the bike is built, designed etc.

    Manufacturers design their bikes for different jobs. Allez are at the lower end of the range, so Specialized have designed these to be more forgiving. The carbon Tarmac however, is designed for racing, so is much stiffer.
  • dennisndennisn Posts: 10,422
    h14turbo wrote:
    I am interested in getting a carbon frame, but am wondering is a low end-ish carbon frame, i.e. planet x, going to be much stiffer than the frame on my current specialized allez? Cheers

    I realize that the big buzz word these days is "stiffness"(in more than a few areas).
    Anyway I think that you have to ask yourself if all this "stiffness" talk is just manufacturer
    hype or the real deal. I doubt that, like many cycling theories, whether stiffness has been proven to be great, good, OK, or of no particular use. Maybe a bike with some flex is a
    good thing(or bad). I don't think much is really known. Obviously you can't have a bike
    that's flimsy and the same goes for one that's as solid as a rock. But I rant on. Sorry.
  • Monty DogMonty Dog Posts: 20,614
    Are you comparing materials or fully constructed frames? One is a valid comparison, the other is far more subjective. Aluminium frames tend to be 'over-built' to compensate for the finite fatigue limit of the aluminium alloy - consequently the thicker tubing can feel very harsh. Some thinner-walled, heat-treated alloys are a bit more resilient. The grade and construction of carbon makes a significant difference too.
    Make mine an Italian, with Campagnolo on the side..
  • rockmountrockmount Posts: 761
    I suppose stiffness may be measured in terms of flexural modulus. Aluminium has a flexural modulus of around 10,400,000 psi. Values as high as 8600,000,000 psi. may be achieved with carbon fibres. Just what this has to do with the price of cheese, I'm not sure. I suppose, if you look at the material of choice in the pro world, that may provide some clues. IME my carbon frame is certainly much easier to sit on all day than my Aluminium one. Is it faster or more responsive ?? I couldn't say for sure, but I don't reckon the pros use them because they are comfy.
    .. who said that, internet forum people ?
  • redddraggonredddraggon Posts: 10,862
    rockmount wrote:
    the material of choice in the pro world

    The material of choice in the Pro world is what ever the sponsor wants the team to have.

    Silence-Lotto rode aluminium in the Spring Classics
    Skil-Shimano ride Koga alloy bikes
    I like bikes...

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  • rockmountrockmount Posts: 761
    rockmount wrote:
    the material of choice in the pro world

    The material of choice in the Pro world is what ever the sponsor wants the team to have.

    Silence-Lotto rode aluminium in the Spring Classics
    Skil-Shimano ride Koga alloy bikes
    Can't wait until Fromageries Bel start a team, should be very entertaining :wink:
    .. who said that, internet forum people ?
  • JesseDJesseD Posts: 1,961
    Used to ride a Carbon CR1 Pro, very stiff and comfort was ok.

    Was given a six-13 for free, now ride that, same comfort and stiffness as the CR1 to be honest, I ride a fair bit and was expecting the difference to be massive but it wasn't :shock:

    I must admit the CR1 is a bit lighter though so I do feel the weight when climbing, but then again I am not exactly a light weight myself.

    As others have said and will continue to tell you, if carbon turns you on then buy carbon, if you want a comfortable bike that rides well and doesn't flex much in the BB etc, then buy what ever rides best and don't worry about what it's made of. In other words buy what will inspire you to get out and ride!!

    That said the PX stuff is basic but does what it says on the tin. I had a PX carbon staelth Tri bike, it rode great, was pretty responsive etc etc, worked for me. I am sure the road bike is a good bike too.
    Obsessed is a word used by the lazy to describe the dedicated!
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