Rim depth
Comments
-
Rock 'n' Roule0 -
i did this to death when looking and didnt really have a budget in mind but I ended up going for some mavic cosmic 50mm and there fantastic. Yes they will make your bike look cool. I live right next to a road that is dead flat and i mean on the gps it varies by 1ft over a 8 mile run then there is a roundabout and then i can come back again. it goes through a natural swap here in mallorca. I have done this road so many times i cant tell you, with my cosmics on i do it about 1 min quicker over a round trip not a huge difference over my Fulcrum 3 but they make a better noise and look cool haha.
I bought mine of ebay got a result they are one year old came with new tyres and got them for 375 quid (bargain) I would go for a set of those of ebay over chinese as they really are bombproof. I dotn notice the extra lbs when climbing but even if they dont make much difference in terms of speed (but they will) they make you feel better about the bike and maybe ride more which cant be a bad thing.0 -
Eyon wrote:FransJacques wrote:You're making a pretty basic assumption with the following:
"Please do not lecture me on why I need Zipps/HEDs/ENVEs over china rims, that is for another thread no doubt."
Your stated objective is aerodynamics however you're assuming that generic and name brand rims are perfect subsititues, which betrays your ignorance. You focus on rim depth rather than shape. There are aero and there are deep rimmed wheels, they are not always the same.
What are your thoughts on the different shapes out there? Which one will help you best? Which one works best with the particular brand of tubs/clinchers you use?
A fool and his money are soon parted.
Thank you for your post, really appreciate it, I was surprised it took so long for someone to tell me that I shouldn't buy from China!
For what its worth, Zipp may spend thousands and thousands testing their rims in wind tunnels, and sure they evidence pays off, but who is to say the Chinese is bad? Their rims are pretty much a strait copy of the Toroidal section used in the current 101/202/303/1080 wheels... OK it might not have the dimpled surfaces which zipp use, but the skin friction drag on a 50mm wheel isnt all that great, so if we take pressure drag as our main source of aerodynamic drag that is all down to shape, and if its a toroidal copy, then, well, I should be fine? Also for this purpose lets ignore wave drag as at 20-25mph I really wouldnt be worrying about that.
I know that's a very basic way of looking at it, but lets be realistic, none of us have wind tunnels, most of us will never use one. I doubt Zipp or any of the big makers will release details on the .cd of their products and as none of us have the ability to test that, it all makes the scientific debate about what rim is better totally irrelevant? Generally speaking surface drag must be less than pressure drag for the rim to worth being deeper. As wheels have such little surface we can almost assume surface drag is not worth thinking about and therefore we worry about pressure drag. Pressure drag is effected by shape and generally speaking the thinner the section in relation to its depth is more aerodynamic, especially in symmetrical section. I know there are exceptions to the rule but for the purpose of this argument we can therefore assume that given a fixed thickness of wheel section, the deeper the wheel, the more aerodynamic, so long as the shape is suitable in the first place.
I might be wrong here, and will happily be corrected.
Therefore I can conclude that yes, I might be a fool, but at least I am only a fool who parts with £250 rather than £2500! Try telling me that the generic wheels are 10 times lesser performing than the expensive stuff?
Awesome stuff, well done.0 -
P_Tucker wrote:Eyon wrote:FransJacques wrote:You're making a pretty basic assumption with the following:
"Please do not lecture me on why I need Zipps/HEDs/ENVEs over china rims, that is for another thread no doubt."
Your stated objective is aerodynamics however you're assuming that generic and name brand rims are perfect subsititues, which betrays your ignorance. You focus on rim depth rather than shape. There are aero and there are deep rimmed wheels, they are not always the same.
What are your thoughts on the different shapes out there? Which one will help you best? Which one works best with the particular brand of tubs/clinchers you use?
A fool and his money are soon parted.
Thank you for your post, really appreciate it, I was surprised it took so long for someone to tell me that I shouldn't buy from China!
For what its worth, Zipp may spend thousands and thousands testing their rims in wind tunnels, and sure they evidence pays off, but who is to say the Chinese is bad? Their rims are pretty much a strait copy of the Toroidal section used in the current 101/202/303/1080 wheels... OK it might not have the dimpled surfaces which zipp use, but the skin friction drag on a 50mm wheel isnt all that great, so if we take pressure drag as our main source of aerodynamic drag that is all down to shape, and if its a toroidal copy, then, well, I should be fine? Also for this purpose lets ignore wave drag as at 20-25mph I really wouldnt be worrying about that.
I know that's a very basic way of looking at it, but lets be realistic, none of us have wind tunnels, most of us will never use one. I doubt Zipp or any of the big makers will release details on the .cd of their products and as none of us have the ability to test that, it all makes the scientific debate about what rim is better totally irrelevant? Generally speaking surface drag must be less than pressure drag for the rim to worth being deeper. As wheels have such little surface we can almost assume surface drag is not worth thinking about and therefore we worry about pressure drag. Pressure drag is effected by shape and generally speaking the thinner the section in relation to its depth is more aerodynamic, especially in symmetrical section. I know there are exceptions to the rule but for the purpose of this argument we can therefore assume that given a fixed thickness of wheel section, the deeper the wheel, the more aerodynamic, so long as the shape is suitable in the first place.
I might be wrong here, and will happily be corrected.
Therefore I can conclude that yes, I might be a fool, but at least I am only a fool who parts with £250 rather than £2500! Try telling me that the generic wheels are 10 times lesser performing than the expensive stuff?
Awesome stuff, well done.
+1 I like this response
0
