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front wheel aerodynamics

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front wheel aerodynamics

Old 03-02-07, 11:50 AM
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front wheel aerodynamics

I was reading some topics earlier which had a link to a site demonstrating what a large aerodynamic difference drop bars make and aero bars make.

I'm going to be getting a new wheelset soon. How much of an aerodynamic advantage really does radial lacing give you versus say 3-cross? How much of an advantage is 28 spoke over 32? 24 spoke? 20?
 
Old 03-02-07, 12:46 PM
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Basically none. The difference would be if you went with a deep (40+mm) rim. Reducing spoke count reduces weight, and with improvements in technology, manufacturers can still produce a stiff and solid wheelset. Granted, if you break a spoke with most of the "boutique" wheelsets as some people refer to them as, chances are you won't be riding home.

I crashed last summer and was running a set of Bontrager Race Lite wheels that came stock on my Trek 5200....a paired-spoke wheelset. I hit a rock in the road at around 23 mph, hit it hard enough that it bent the crap out of my wheel (but didn't break a spoke...only bent it). Ride over. Now...would that have happened with a conventional 32 spoke wheel, I dunno....and I don't feel like trying it again to find out.

I just took delivery of a set of Niobium 30 wheels from Mike Garcia (the man, the myth, the legend), and had it built up with DT Super Comp spokes, 20f/24r spoke count, radial lacing up front with 2x in the back, brass nipples on the drive side and aluminum nipples on the rest....Speedcific Serenity hubs front and rear, and his standard quick release skewers. I had these built specifically for racing; wanted a set of bombproof wheels that were slightly more "aero" than my Race Lites, but also something stiffer. Given the fact that I'm under 150 pounds, I can get away with the lower spoke counts. I then decided to go with the standard steel skewers rather than the Ti ones because Mike said the steel ones are much stiffer than the Ti ones....but nearly twice the weight. The wheelset, including rim tape and skewers, is around 1570 grams, so I'm pretty happy with that.

So....I just paid under $500 for a decent little set of wheels. Will they be as "fast" as say a pair of 58mm Zipp carbon tubulars? No. But, I spent $1,500 less and won't worry as much about trashing a rim.
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Old 03-02-07, 02:43 PM
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Originally Posted by GuitarWizard
I crashed last summer and was running a set of Bontrager Race Lite wheels that came stock on my Trek 5200....a paired-spoke wheelset. I hit a rock in the road at around 23 mph, hit it hard enough that it bent the crap out of my wheel (but didn't break a spoke...only bent it). Ride over. Now...would that have happened with a conventional 32 spoke wheel, I dunno....and I don't feel like trying it again to find out.
i doubt it would have. i also ride Bontrager paired spoke wheels, and while i do like them, they are harder to keep straight than standard spoke wheels because there is so much room between the pairs of spokes. at least that's what a LBS told me...

good luck with the MG wheels, i was actually looking to get a set for this summer, only with titanium skewers...
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Old 03-02-07, 02:59 PM
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the spoke pattern does not have much aero effect, but aero spokes does. years back they had oval spokes. I had a front wheel built with 32 spokes with a semi aero rim. If you just spin a front wheel you can hear the turbulance of from the spokes. spinning my aero spoke wheel is definately quieter than conventional spokes and yes, this wheel is fast. I was able to hit 50 mph with the aero wheel. conventional wheel got up to 46mph.
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Old 03-03-07, 10:42 AM
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Thanks. I'll try a radial front wheel and a crossed front wheel at my lbs (but otherwise as identical as they can be) and see how different it feels.

Does low spoke count have much of an impact on aerodynamics, or is it mostly the rim?
 
Old 03-03-07, 11:53 AM
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Originally Posted by fogrider
the spoke pattern does not have much aero effect, but aero spokes does. years back they had oval spokes. I had a front wheel built with 32 spokes with a semi aero rim. If you just spin a front wheel you can hear the turbulance of from the spokes. spinning my aero spoke wheel is definately quieter than conventional spokes and yes, this wheel is fast. I was able to hit 50 mph with the aero wheel. conventional wheel got up to 46mph.
I concur that 3X vs. Radial should have almost no aero difference; but will add that the number of spokes matter.
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Old 03-03-07, 07:08 PM
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there's some good stuff on this thread:

https://weightweenies.starbike.com/ph...er=asc&start=0

It takes about a page to "clear its throat", but then some interesting posts about aerodynamics start to pop up. The guy called Adrien, who's on the Weight Weenies forum, is the author of some of (or all of?) the aero articles on https://www.rouesartisanales.com/ , such as this one: https://www.rouesartisanales.com/article-4934445.html

This thread also has a few good posts: https://www.bikeforums.net/showthread...highlight=holy

I don't know a lot about aerodynamics, but, to answer your question, both rim depth and spoke count affect aerodynamics: a 15mm rim with 12 spokes ( i hope there's no such wheel ) would have an aero advantages over a 20mm 28-spoke wheel, as would a 100mm rim with 24 spokes. Getting aero isn't just about getting to a certain depth -- which is usually stated as being >40mm -- it's also about any increase in rim depth reducing the spoke count because the wheel is stronger, which then improves aerodynamics. In other words, some would say that 30mm isn't enough to affect any aero benefit, but it is if the 30mm makes the wheels strong enough to drop the spoke count to (for eg) 16 or 18.

eh, more later.....
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Old 03-03-07, 07:31 PM
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I'm not sure, but there seems to be some conflicting aero data out there. The "Great Wheel Test" suggest that there's about 20W difference between a very good aero wheel-set and a shabby one. According to the Kreuzotter calculator, a 20W benefit, at or around 45kph, gives a rider a speed increase of about 0.7kph!!
https://www.kreuzotter.de/english/espeed.htm

This list of "aeroness", taken from a magazine, says that there's about a 15W aero benefit from the total 465W of rider drag, going from normal wheels to tri=spokes: https://www.bikeforums.net/showthread...highlight=holy
This is a pretty big 3.23%.


.....I'm confused:

On the HED site, it says that an average rider creates about 6.5lbs of drag, of which, about 1/4 of a pound is from the wheels (3.8%). They also say, that in a cross/head wind of an angle of ~20 degrees, their HED JET 60 wheel (deep dish, 16 spokes) creates 218g of drag (doesn't add up so far ), compared to 294g of drag from a 28 spoke low profile wheel -- a 25% improvement just with the wheels. So, 25% from the 1/4 pound (3.8%) of 6.5 pound of total rider drag is less than 0.96%
https://www.hedcycling.com/wheels/stinger60.php

0.96% from the total 465W (from the "Holy Cow, Aero..." thread) is only a 4.46 watts.


Is all this just saying that tri-spokes are heaps better than 16 spoke, deep dish wheels?

Last edited by 531Aussie; 03-03-07 at 07:44 PM.
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