Aerodynamic wheelset.. Front or rear?

Discussion in 'Cycling Equipment' started by willocrew, Aug 4, 2006.

  1. willocrew

    willocrew New Member

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    I'm wondering, if i am looking to get just 1 aeroynamic wheel, would it be better to get the front one first? I've heard that a front aero wheel paired with a rear ordinary wheel is quite effective...

    Any suggestions?
     
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  2. 11ring

    11ring New Member

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    Front is more effective but you will look stupid with a front deep rim and a shallow rear one.



     
  3. Phill P

    Phill P New Member

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    How deep is deep?

    Most people tend to run a deeper rear wheels, but I think this is for handling in cross winds etc.

    It makes sense that a front wheel would be a bigger gain for aero though as it sees the air first, the rear wheel has turbulent air off the front wheel, frame, and riders legs.

    I agree that a much deeper front rim would look odd, simply because it is different. Compact frames were different at one point as well.
     
  4. dm69

    dm69 New Member

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    You can but a TT wheel with 4 bladed carbon spokes on PBK seperate from the rear.

    I suggest you just get an aero front wheel if thats all you can afford. Apparently a recent wind tunnel study found an aero helmet will give you 4 times more of an advantage compared to aero wheels.

    On probikekit you can get an LAS crono helmet for $200 aus. Skinsuits are $100au and shoecovers are $20, the body is 85% of the wind resistance.

    A lot of TT riders I see were baggy clothes and standard helmets without shoe covers yet they have the million dollar aero bike.

    Also put the water bottle on the seatpost not the downtube. There is a thread somewhere around here on the results of the study.
     
  5. sideshow_bob

    sideshow_bob New Member

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    As you are quoting $AU I'm guessing you are in Oz. As far as I'm aware no aero helmets pass the required safety standards testing for Australia. Accordingly you can't wear them in any Cycling Australia event, which is basically everything, with the exception of UCI events as far as I'm aware. Of course I could be wrong.

    --brett
     
  6. dm69

    dm69 New Member

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    thats interseting. I will have a look at that. I may need to save my money ;)

    thx brett
     
  7. willocrew

    willocrew New Member

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    True about the body wind resistance, but i figured the aero position would cut down that figure by quite a bit.

    Yea my bike would probably look unbalanced, but I don't think i'll be too bothered about it as long as there's some logic behind it.

    As to how deep, I'm probably looking at 45mm carbon rims, but i can't say for sure as i'm not buying first hand.

    But what i'm curious is, would there be any dangerous handling characteristics expecially when crosswinds suddenly come into play.
     
  8. mikesbytes

    mikesbytes New Member

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    I read that last night on one of the Sydney bike club sites and now I can't find the link. What it said was that you needed the Australian Standard sticker to be attached to the helmet and it also noted that there are no aerodynamic helmets that have been certified to the Australian Standard and therefor they are banned. So technically if you buy any helmet from mail order overseas from Australia then it does not qualify for racing as it doesn't have the aussie safety sticker.

    That still leaves aero clothing as meeting the regulations.
     
  9. sideshow_bob

    sideshow_bob New Member

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    I had my helmet checked twice last year, as CA had issued a directive to clubs. This year, zero checks. I do know if you don't have the sticker, you don't get to race.

    --brett
     
  10. Phill P

    Phill P New Member

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    why spend a gizillian $$s on an areo bike and clothes and wheels if you then stick a big round non aero drink bottle in the middle?

    I saw Lance and a few others had camelback setups under thier skin suits. Clearly just 1-2L models so they had enough fluid for a 1 hr TT but it was as aero as posible on thier back under the skin suit.

    As to 45mm in a cross wind......I some times feel even a small tug on my 30mm deep zondas, and I have heard people complain about mavics in cross winds. I haven't had the priveldge to ride really deep wheels let a lone in the wind.
     
  11. mikesbytes

    mikesbytes New Member

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    It said that the sticker had to be present, so if you removed it the helmet didn't comply. They didn't check this morning.
     
  12. 11ring

    11ring New Member

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    For optimum aerodynamics you need a rim at least 50mm deep.

    The 38mm varieties are not nearly as effective as the angle is too sharp to keep the airflow attached.

     
  13. kleng

    kleng New Member

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    +1 on the 50mm rims as a minimum for aero advantage, also I don't think your going to be able to ride a 50mm in all windy conditions. I tried this the other day with a loaner Hed Jet 50 and I felt exhausted just reacting to the wind gusts.
     
  14. JTE83

    JTE83 Member

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    I have HED 3s and strong crosswinds make my ride scary.
     
  15. 11ring

    11ring New Member

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    You get used to it, but yes, not every day wheels. I have the luxury of having 50;s and 38's. (got some ZIPP 303;s for free from my ex-girlfriend who "didn't need 2 sets of wheels"



     
  16. rayhuang

    rayhuang New Member

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    I assume then that the rim depth has more to do with aerodynamics efficiency of the wheels than the number or shape of the spokes or if its bladed CF spokes?

    My TT front wheel in 1990 was an aero shaped aluminum 36 hole rim (Matrix??)with 18 (16g) spokes radially and a 18c conti tire. Boy talk about being nervous abut flats and wobbly in the turns!!

    I too want to race a TT next year, but on a standard road bike. Need to try and get it reasonably aero, but not go crazy.
     
  17. Bob Ross

    Bob Ross New Member

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    Recent issue of Bicycling magazine has an interview with the squad leader of the MIT cycling team. Not only do these kids have access to a wind tunnel, they've got the brains to analyze the data collected there.

    One of their observations was that a standard waterbottle on the seat tube is not only more aerodynamic than a waterbottle on the down tube, but it's more aerodynamic than *not* having any waterbottle at all!

    The other observation that caught my attention was that changing from a standard to an aero helmet offers WAY more advantage than "upgrading" to one or two aero wheels.
     
  18. 11ring

    11ring New Member

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    The rim depth is very important to keep the air attached. Also it covers the spokes/reduces their length where they are spinning the fastest. A low profile rim with few spokes will not be very aero at all.

    But generally the stiffer deeper rims let you use less spokes as well.

    Interesatingly there does not seem to be much benefit from going below 20 spokes. And the ovals are maybey better than the blades. (but the blades are heavier and stifer, so you can use less)




     
  19. rayhuang

    rayhuang New Member

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    Thanks for the info. Would I be correct in assuming you can get away with a disc or deep dish rim in the rear in mild crosswinds (but enough crosswind to affect the front).
     
  20. willocrew

    willocrew New Member

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    Usually Discs are used on the indoor tracks, or zero wind days. People go for the trispoke carbon rearwheels in place of the discs in mildly windy days.
     
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