rim question

davecooper
davecooper Posts: 290
edited November 2007 in Workshop
Is there any advantage to using a semi aero rim such as a CXP33 on a 32 spoke wheel, i.e. are the aero advantages of the rim negated by the number of spokes along with the extra weight of the rim? Does the deeper rim add to the wheel strength significantly?

Comments

  • Bronzie
    Bronzie Posts: 4,927
    I think that CXP33 rims are only very marginally more aerodynamic than a standard Open Pro shaped rim - a true aero section rim is 4 times deeper than it is wide, and CXP33's are nowhere near this. A true aero wheel will have a much deeper rim and fewer spokes.

    They are probably a bit stiffer/stronger than an Open Pro rim but this may just manifest itself in a harsher ride rather than making the wheels bombproof. They are marginally heavier than Open Pros as well (470g v 435g).
    It's a Lifestyle! -+-+- Coggan Training Levels
  • davecooper
    davecooper Posts: 290
    Thanks for the advice, the point about a harsher ride is well taken. I am trying to tame a very harsh ride so something like Open Pros with 25mm tyres may be my best option.
  • Monty Dog
    Monty Dog Posts: 20,614
    IME shallow aero rims make very little difference unless combined with aero spokes - research suggest that aero rim benefit doesn't really kick-in until about 45mm depth. That said, I built a pair of wheels using Velocity Aerohead rims and 24h radial bladed spokes and it felt very fast in comparison to something like a Ksyrium. The downside of deeper rims is that they are heavier and can feel pretty harsh too - depends what your definition of 'bomb proof' is really.
    Make mine an Italian, with Campagnolo on the side..
  • maddog 2
    maddog 2 Posts: 8,114
    I'd say the main thing a CXP33 rim has over an OP is strength. It will build a slightly stronger wheel.

    Having said that, build quality and spoke choice always play a massive part in how a wheel performs. A well built OP will take some serious hammer.
    Facts are meaningless, you can use facts to prove anything that's remotely true! - Homer
  • dennisn
    dennisn Posts: 10,601
    davecooper wrote:
    Thanks for the advice, the point about a harsher ride is well taken. I am trying to tame a very harsh ride so something like Open Pros with 25mm tyres may be my best option.

    Rim type and / or spoke configuration have very little to do with a "harsh" ride.
    It is pretty much a tire pressure "problem" if you will . Higher pressure, the "harsher"
    the ride. This is true dispite what bike and wheel manufacturers will tell you about
    their "smooth as silk ride". So, wider tire, less pressure, equals smoother ride.

    Dennis Noward

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