# Mixing Aero & climbing wheels



## Christopaul (Jan 27, 2012)

I just got a set of Hed Jet 4's. This morning I just put on the front wheel (which has a 46mm depth). The rear wheel is a Bontrager xxx race lite climbing wheel. This mornings ride was flat (under 1000 ft over 34 miles). I liked being able to spin up fast (thanks to the rear wheel) but the kick was on the little rollers. The real difference was the way I was able to hold speed. I was passing by riders that I usually can only draft. Do others mix wheel sets? Occasionally I'll see someone riding with a deeper profile rear. What conditions benefit using deeper rear? What conditions would justify using a deeper front? I feel one of the limiting factors is my own engine. On this mornings ride, I felt the benefit kick in at 18 mph (& above). On many courses, I would not be able to maintain 18 mph average. What wheel combination would you use on a century with 6,000 feet of climbing (the Tierra Bela in No. Calif)?


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## Elpimpo (Jan 16, 2012)

your bike must look 'interesting' post a pic.

the 'deeper rear rim' people are usually either time trialists or fanboys who want the 'look'

as far as the century, lots of things can happen in 100 mile i.e. cross winds, cross wheel crashes etc..
I'd use the xxx's


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## rruff (Feb 28, 2006)

It's good to see the placebo effect is alive and well...


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## Mike T. (Feb 3, 2004)

Christopaul said:


> I liked being able to spin up fast (thanks to the rear wheel) but the kick was on the little rollers. The real difference was the way I was able to hold speed. I was passing by riders that I usually can only draft.


Sorry Christo but this is anecdotal evidence at its finest. Use two sets of wheels for two seasons (one season for each set) and record your average speeds on "hard" steady solo rides (hard perceived exertion) for the whole year. Then compare average speeds and make a conclusion from your data.


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## Christopaul (Jan 27, 2012)

Elpimpo said:


> *your bike must look 'interesting' post a pic.*...
> 
> 
> I go for function over look.


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## Jay Strongbow (May 8, 2010)

So you could spin up fast because of the rear wheel? Were you popping a wheeley or was the front wheel somehow spinning slower?


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## Christopaul (Jan 27, 2012)

*shouldn't dignify your comment..*



Jay Strongbow said:


> So you could spin up fast because of the rear wheel? Were you popping a wheeley or was the front wheel somehow spinning slower?


I didn't mention it, but the route had lots of stop lights and I caught most of them...The Jet 4 set is about 1700g and the xxx's come in at 1250g. That makes a difference when starting from a dead stop.


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## Elpimpo (Jan 16, 2012)

Christopaul said:


> I go for function over look.


Then just use the xxx's. 
Im not trying to jive you jim.
I'm just saying that having two light-asses wheels on your bike is DEFINITELY better than having an 'aero' wheel in the front and a light-assed wheel in the back.
I'm no weight weenie, I'm just against this whole 'aero' movement.

I am also against mixing different types/brands/size (and probably color) wheels.

Road bikes are secksy to me, and it sounds like you're dressing her up like a hooker.

Thats all.


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## Doolab (Feb 13, 2008)

Elpimpo said:


> [snip]
> Im not trying to jive you jim.
> [snip]
> I'm just against this whole 'aero' movement.
> ...


It's no jive holmes. 
If you knew the difference, you wouldn't be against the "whole 'aero' movement." :crazy:
Ever wonder why TT racers and serious triathletes race with and prefer aero wheels instead of box section rim wheels. :idea:


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## chase196126 (Jan 4, 2008)

Christopaul said:


> I didn't mention it, but the route had lots of stop lights and I caught most of them...The Jet 4 set is about 1700g and the xxx's come in at 1250g. That makes a difference when starting from a dead stop.


Sadly those that 450 gram difference would make a .03 second difference if you were to accelerate from a dead stop and travel 100 meters while pushing an average of 350 watts. That is something like a 1-2 watt difference, which is within the margin of error for the most accurate power meters on the market, which means you are certainly incapable of perceiving a difference between those two wheels while riding. 

The weight means nothing once you get the wheels going on flat ground but the aero profile of the rear wheel will make you a slight bit faster than running the other low profile rim. If you really care about function over looks you could run both deep rims, or a deep rim on the front and a shallow one in the rear. The front aero wheel will have a larger impact on your drag than the rear will, but it could make handling a bit twitchy. If you want to be as fast as possible ride both deep rim wheels. The aero benefit will eclipse the slight weight gain. 

Keep in mind, the speed benefits of the deeper rims will make a difference of a few saved seconds in a TT or a fraction of a meter in a sprint to the line but they will not take you from a 20 mph rider to a 23 mph rider. Your hunch in your original post was very good, speed is almost entirely about the engine riding the bike.


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## Elpimpo (Jan 16, 2012)

Doolab said:


> It's no jive holmes.
> If you knew the difference, you wouldn't be against the "whole 'aero' movement." :crazy:
> Ever wonder why TT racers and serious triathletes race with and prefer aero wheels instead of box section rim wheels. :idea:


"aero" rims, along with low spoke count wheels, are a F'n fad.
They do more harm than good If* YOU* knew what you ere talking about, you'd agree. 

Whats a little piece of carbon glued to your rims gonna do?
The frontal force/resistance that your body creates DOESNT allow for a 'deep 'rim' to help. I'm sorry, its been SCIENTIFICALLY PROVEN (by scientists) that its VERY minimal.

Why would you want to carry an extra 500 grams (or more) for 1-2 watts?!?!?


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## chase196126 (Jan 4, 2008)

Elpimpo said:


> "aero" rims, along with low spoke count wheels, are a F'n fad.
> They do more harm than good If* YOU* knew what you ere talking about, you'd agree.
> 
> Whats a little piece of carbon glued to your rims gonna do?
> ...



You are correct that the rider makes up the majority of the drag while riding but having aero wheels will make that rider faster. Your assertion that the drag created by the rider negates the aero benefit of deep rim wheels is simply bogus.

As for time savings it depends on what you consider minimal. For a quick example, 2008 Zipp 808s will save 14 watts compared to 2007 Ksyrium Equipes. That translates to roughly 50-60 seconds over a 40km TT. Compared to other aero options the 808s would save around 8-10 watts, which translates to around 30-40 seconds in a 40km TT. It is pretty funny that saving 500 grams with box section wheels will cost you more watts than a heavier aero wheelset until you get to around a 7% grade

30 seconds is a big deal in a time trial. I know I wouldn't want to give that up just so my bike is a little easier to lift out of my car


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## Elpimpo (Jan 16, 2012)

chase196126 said:


> 30 seconds is a big deal in a time trial. I know I wouldn't want to give that up just so my bike is a little easier to lift out of my car


1. Keyword TIME TRIAL (as in onTT bike on a flat windless course)

2. easier to lie out of your car and up a hill (as most races)

say what you want, the op asked about mixing rims; I did get off topic, and now were arguing things that aren't pertinent.

OP: Im sorry i don't agree with mixing rims. Use the hed's OR the xxx's just PLEASE don't mix em.


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## Doolab (Feb 13, 2008)

Elpimpo said:


> "aero" rims, along with low spoke count wheels, are a F'n fad.
> They do more harm than good If* YOU* knew what you ere talking about, you'd agree.
> 
> Whats a little piece of carbon glued to your rims gonna do?
> ...


Sadly, you're deluded. In fact, I challenge you to cough up a link to your "scientifically proven by scientists" data. And while you're trying to pull it out of thin air, take a moment to answer this question: How come professional racers in time trial and triathlon races all run on aero wheels instead of opting to save a few grams and ride box section wheels instead?

Anyway, here's a somewhat dated chart from Roues Artisanales but the data is still valid and will be good enough to make my point. You'll notice the best aero wheels are the least power robbing ones on the left, while the least aero wheels tend to cluster around the upper end of the power absorption chart.









And to quote from the conclusion in the rouesartisanales.com article where this data was compiled:


> "Leaving inertia, bearing resistance and lateral stiffness aside for a moment, deep rims bring definite advantages over shallower alternatives. They are particularly efficient
> on flat stages and downhills, where speeds are highest.
> For Time-trial, or flat races, deep rims with a low spoke count are the best option. Actually, for standard road use, this is the best solution. Indeed, the front wheels have
> perfectly balanced and wide bracing angles, meaning a high lateral stiffness. Reducing the spoke count of the front wheel is not really a problem at all!"


:smilewinkgrin:


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## Christopaul (Jan 27, 2012)

Mike T. said:


> Sorry Christo but this is anecdotal evidence at its finest. Use two sets of wheels for two seasons (one season for each set) and record your average speeds on "hard" steady solo rides (hard perceived exertion) for the whole year. Then compare average speeds and make a conclusion from your data.


Data is a hit or miss proposition when it comes to making a purchasing decision. How does one filter all the fantastic claims to the actual experience? I do track my performance and use Strava analytics. When I got the xxx's a couple of years ago, I noticed an incredible improvement over my Mavic Ksyrium ES's. I didn't need two years of recording data to validate that. Yesterday I experienced another positive leap, with the aero/non aero combo.
Today I will continue this experiment on a course with more varied terrain (32 mi with 2200 ft). 

While my experience(s) are not persuasive or compelling for the general public, they are in fact the most compelling truth for me.


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## Mike T. (Feb 3, 2004)

As long as you're happy and convinced that's all that matters Christo. IMO *no* wheelset is an "incredible improvement" over any other. I guess it depends on one's definition or measurement of "incredible" doesn't it?

To me, "incredible" would be a 1mph improvement over a flat-out 30 mile ride. That would be about a 5 minute improvement over that distance (approx) but I know (from my own data) that other variables make more difference than that. So how (without a powermeter) are we going to judge the improvement provided by a set of wheels?


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## Christopaul (Jan 27, 2012)

chase196126 said:


> Sadly those that 450 gram difference would make a .03 second difference if you were to accelerate from a dead stop and travel 100 meters while pushing an average of 350 watts. That is something like a 1-2 watt difference, which is within the margin of error for the most accurate power meters on the market, which means you are certainly incapable of perceiving a difference between those two wheels while riding.
> 
> The weight means nothing once you get the wheels going on flat ground but the aero profile of the rear wheel will make you a slight bit faster than running the other low profile rim. If you really care about function over looks you could run both deep rims, or a deep rim on the front and a shallow one in the rear. The front aero wheel will have a larger impact on your drag than the rear will, but it could make handling a bit twitchy. If you want to be as fast as possible ride both deep rim wheels. The aero benefit will eclipse the slight weight gain.
> 
> Keep in mind, the speed benefits of the deeper rims will make a difference of a few saved seconds in a TT or a fraction of a meter in a sprint to the line but they will not take you from a 20 mph rider to a 23 mph rider. Your hunch in your original post was very good, speed is almost entirely about the engine riding the bike.


I appreciate all the knowledgable responses and input. This helps to keep my expectations in check. The bottom line is that good equipment does make a difference...


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## Christopaul (Jan 27, 2012)

Doolab said:


> Sadly, you're deluded. In fact, I challenge you to cough up a link to your "scientifically proven by scientists" data. And while you're trying to pull it out of thin air, take a moment to answer this question: How come professional racers in time trial and triathlon races all run on aero wheels instead of opting to save a few grams and ride box section wheels instead?
> 
> Anyway, here's a somewhat dated chart from Roues Artisanales but the data is still valid and will be good enough to make my point. You'll notice the best aero wheels are the least power robbing ones on the left, while the least aero wheels tend to cluster around the upper end of the power absorption chart.
> 
> ...


Now that's interesting! Thank-you! It would be great to see more products in head to head comparisons measuring specific attributes. These lists a few and far in-between...


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## rruff (Feb 28, 2006)

Christopaul said:


> When I got the xxx's a couple of years ago, I noticed an incredible improvement over my Mavic Ksyrium ES's. I didn't need two years of recording data to validate that. Yesterday I experienced another positive leap, with the aero/non aero combo


I'm sorry that you came to this site and started asking questions, because the real answer is that you are "suffering" from "new bike part syndrome". In other words the positive leaps (if they are real measured improvements) are a result of your expectations and attitude.

Way back when I was a new rider this often happened to me, too. It never lasted. Now it just doesn't happen anymore. If I'm going as hard as I can... ie coughing blood, going cross-eyed, and legs refusing go around at the end... there is very little variance in my power output... and if I get some new equipment, the benefit is pretty much what I'd expect via physics... ie somewhere between none and a little.

There are several calculators online that allow you to model various riding situations. This one is probably the most widely used: Analytic Cycling, Interactive Methods for Estimating Cycling Performance Parameters. Tom Compton


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## Elpimpo (Jan 16, 2012)

Doolab said:


> In fact, I challenge you to cough up a link to your "scientifically proven by scientists" data.


I was actually referring to the same site you just posted.

Again, very minimal.
According to this chart everyone should be running 808's?
I don't think so.
I am not a time trialist and don't even know where these things are held. For a century, I'd rather have wheels that aide in climbing and reduce cross wind craziness. The world aint flat you know


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## Doolab (Feb 13, 2008)

To the OP, if not getting dropped on fast group rides is one of your goals, or you'd like to push faster speeds as long as you can hold them, then an aero wheelset is something to consider.

And mixing wheels shouldn't be an issue but will only be a compromise of sorts depending on the wheels chosen, with the biggest drawback possibly being that you'd draw some critiques from the bike fashion police. 

To Elpimpo, your conclusion that "everyone should be running 808's" was not made by the Roues Artisanales test report. However, they did say "for standard road use, this is the best solution" , referring to aero wheels in general.

So, even when one just rides centuries with ~5000ft of ascents, on most of the ride besides the shorter climbing portion, one would be either on flats or descending, and both of these terrain types aero wheels can benefit the rider in faster speeds with less effort saving him time & energy. Reread Chase196126's excellent post again for some real insight into the benefits of aero wheels coming from a pro racer.


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## Christopaul (Jan 27, 2012)

rruff said:


> I'm sorry that you came to this site and started asking questions, because the real answer is that you are "suffering" from "new bike part syndrome". In other words the positive leaps (if they are real measured improvements) are a result of your expectations and attitude.
> 
> Way back when I was a new rider this often happened to me, too. It never lasted. Now it just doesn't happen anymore. If I'm going as hard as I can... ie coughing blood, going cross-eyed, and legs refusing go around at the end... there is very little variance in my power output... and if I get some new equipment, the benefit is pretty much what I'd expect via physics... ie somewhere between none and a little.
> 
> There are several calculators online that allow you to model various riding situations. This one is probably the most widely used: Analytic Cycling, Interactive Methods for Estimating Cycling Performance Parameters. Tom Compton


Sorry to hear you're that jaded...but thank-you for this link, someone has invested a lot of time and effort to develop this model. I don't know that I have the necessary data or patience to obtain a meaningful understanding. (I'd rather just ride...) Perhaps with more experience, I can come back to this and see if my conclusions are validated or dispelled...


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## rruff (Feb 28, 2006)

I wouldn't say that I'm jaded... if that was true, I wouldn't enjoy riding and racing as much as I do. It's just that the "thrill" of getting some new bike part doesn't seem to have any effect. On the other hand, *not* getting new stuff doesn't seem to have an effect either.

BTW... you don't have to know a lot to use Analytic Cycling. It is easy to plug in different weights and see what the effect is on speed. For aerodynamics it is probably good to do a little investigation so you know how much different changes effect your drag coefficient.


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## multirider (Nov 5, 2007)

An aero front wheel by itself provides slightly more improvement than an equally aero back wheel by itself, but an aero front wheel has MASSIVELY more negative effect on handling in cross winds. I'm 180 pounds and have no problem running a disc in the back in windy TTs, but my 808 on the front makes the bike a handful and is more likely to be replaced by a non-aero wheel if there are cross-winds. This is particularly true on gusty days. When a gust hits, you have to correct your line by steering which impacts the effect of the wind on the wheel which changes how much steering input is required to correct your line. It can become a dangerous spiral on really gusty days.


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## Duc Hunter (Aug 10, 2005)

So I own an obscenely light bicycle (Cannondale Evo Ultimate). In a size 60cm (big) it weighs only 13.1lbs with pedals , a power meter, etc. I love the bike too, and everyone who picks it up is amazed at its weight. Then I read this article. 

http://www.training4cyclists.com/how-much-time-does-extra-weight-cost-on-alpe-dhuez/

After reading this I did a little math. So in round numbers in this "experiment" they added 1.8 liters of water to the tires of a bike and had the rider go up Alpe D'Huez at 275 watts. Then they had him do the same thing, but removed the water from the tires and replaced it with air. In round numbers this saved 2000g from the wheel set, and at the tire, which is where the weight is suppose to matter most. So I was interested to see how much this helped, especially with the more recent debate that light wheels are substantially less beneficial than aero wheels on ANY terrain. So what happened? 

On an 8.1 mile climb that averages a STEEP 8.1% grade, losing 2,000g from your tires saves you a whopping 2 minutes and 21 seconds......this on a climb that took them about an hour! To me, that is nothing, but let's put that in more real terms to all of us. Moving from my 1519g Zipp 808 Firecrest Tubulars to a set of 1095g Zipp 202 Tubulars saves 420g, which is a huge savings for wheels alone. Based on the experiments results this would save a "HUGE" 25 seconds. 

Based on many recent tests of aero wheels it seems clear to me that even on a ride like SIXGap (6 climbs, 12,500 vertical feet in 105 miles) the aero benefit of a deep dish wheel substantially trumps a set of light weight climbing wheels. Remember too that on SIXGap you are climbing for maybe 30 of those 105 miles, so the aero wheels help you on all of the rest (descents, flats), which give you a lot more energy to use on the hills. So for most people I would say get 303's or 404's (or comparably aero wheels) to ride everyday (which have huge aero benefits), and rather then spend the money on climbing wheel for the mountains take that money and take another trip to the mountains to ride and enjoy yourself.


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## rruff (Feb 28, 2006)

Duc Hunter said:


> On an 8.1 mile climb that averages a STEEP 8.1% grade, losing 2,000g from your tires saves you a whopping 2 minutes and 21 seconds......this on a climb that took them about an hour! To me, that is nothing, but let's put that in more real terms to all of us. Moving from my 1519g Zipp 808 Firecrest Tubulars to a set of 1095g Zipp 202 Tubulars saves 420g, which is a huge savings for wheels alone. Based on the experiments results this would save a "HUGE" 25 seconds.


I remember seeing that. The test was flawed because the water increases viscous losses in a random way... so the effect was greater than it would be from weight alone. Could be wind effects and power normalization issues also...

The effect of weight on a climb is easy to calculate. 1.8kg of weight on a rider+bike that weighs 85kg is ~2% effect on climbing speed... so about 72 seconds on the Alpe. 420g would be ~17 seconds.


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## __PG__ (Jan 25, 2012)

A more aerodynamic front wheel will have a greater effect on overall drag than the same design on the rear. The front wheel operates in the freestream, the rear wheel operates in the drag of the front wheel/frame/rider. So the effective flowspeed that the front wheel operates in would be higher than the flowspeed that the rear operates in.

However, the reason why you don't see riders with disc wheels on their front is due to stability issues (as has already been aluded to in this thread).


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## TomH (Oct 6, 2008)

On the same climb with heavy versus light wheels, I made about the same time. The heavy wheels felt heavy, the light wheels felt faster, but werent. Something *is* happening with lighter wheels, beyond placebo.. its not real speed and time improvements, but theres something there.

Between 1500g wheels, and 2200g wheels, you'll feel it. Something gets lost in the calculation.


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## bernithebiker (Sep 26, 2011)

TomH said:


> On the same climb with heavy versus light wheels, I made about the same time. The heavy wheels felt heavy, the light wheels felt faster, but werent. Something *is* happening with lighter wheels, beyond placebo.. its not real speed and time improvements, but theres something there.
> 
> Between 1500g wheels, and 2200g wheels, you'll feel it. Something gets lost in the calculation.


I would say it comes down to acceleration. At a constant speed, wheel weight means nothing. 

BUT, as soon as you accelerate, F = m * a, and the lighter the weight the faster you accelerate. Simple as that. 

And a bike is almost always changing speed, it is unusual to be 'stuck' at 30kph. 

Every corner, every lump in the road, every time you want to speed up a bit, that is when you feel light wheels.


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## Kerry Irons (Feb 25, 2002)

*Faulty analysis*



bernithebiker said:


> I would say it comes down to acceleration. At a constant speed, wheel weight means nothing.
> 
> BUT, as soon as you accelerate, F = m * a, and the lighter the weight the faster you accelerate. Simple as that.
> 
> ...


Yes BUT for every acceleration there is a deceleration, and that means you "get back" the extra energy that you spent in spinning up a heavier wheel. The ONLY place wheel weight is different than any other weight is if you are braking to scrub speed (like being back in the pack in a criterium and having to brake for corners) or in that single acceleration (like in a sprint). And if the extra weight gives an aero advantage then the weight savings are more than cancelled out.

You can definitely feel light wheels but when you put a stopwatch on them, you find that weight is weight regardless of where it is on the bike or the rider.


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## Mike T. (Feb 3, 2004)

Kerry Irons said:


> Yes BUT for every acceleration there is a deceleration, and that means you "get back" the extra energy that you spent in spinning up a heavier wheel. The ONLY place wheel weight is different than any other weight is if you are braking to scrub speed (like being back in the pack in a criterium and having to brake for corners) or in that single acceleration (like in a sprint). And if the extra weight gives an aero advantage then the weight savings are more than cancelled out.
> You can definitely feel light wheels but when you put a stopwatch on them, you find that weight is weight regardless of where it is on the bike or the rider.


So true. And it's all moot as it's lost in the day-to-day variations due to a multitude of factors greater than any minor weight/aero advantages/disadvantages proved (to me anyway) by my meticulously kept records. I (again) recently went from 24mm deep 1410 gram wheels to 27mm deep 1584 gram wheels with no differences in 1.5 hour to 3 hour ride average speeds. I went from aero (CX-Ray) to non-aero (Comp) spokes too.


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## T K (Feb 11, 2009)

I've often wondered if in say a technical crit one would do well to have a deep section wheel in the front to get the aero advantage and use a lighter shallower wheel in back to be able to jump out of tight corners easier. You'd look funny and get ridiculed, but hey.


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## bernithebiker (Sep 26, 2011)

Kerry Irons said:


> Yes BUT for every acceleration there is a deceleration, and that means you "get back" the extra energy that you spent in spinning up a heavier wheel. The ONLY place wheel weight is different than any other weight is if you are braking to scrub speed (like being back in the pack in a criterium and having to brake for corners) or in that single acceleration (like in a sprint). And if the extra weight gives an aero advantage then the weight savings are more than cancelled out.
> 
> You can definitely feel light wheels but when you put a stopwatch on them, you find that weight is weight regardless of where it is on the bike or the rider.


I agree with this, and a totally valid point.

BUT, consider an day climbing in the mountains. Speeds are low on the climb and the lower weight is a definite help getting to the top.

When you come to descend, any extra weight is not an advantage, as you have to brake for all the corners. And cornering should be easier on lighter wheels too (less weight to force round the bend (turning is a form of acceleration).

But I realize that the above example is only a fine slice of cycling and most people aren't doing that every day.


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## tahustvedt (Nov 12, 2009)

Elpimpo said:


> "aero" rims, along with low spoke count wheels, are a F'n fad.
> They do more harm than good If* YOU* knew what you ere talking about, you'd agree.
> 
> Whats a little piece of carbon glued to your rims gonna do?
> ...


Actually, the science says 500 g lighter rims never give anything more than a negligible improvement, even in an acceleration (because double of almost nothing is still almost nothing).

Aero wheels give an improvement over lightweight conventional rims at all speeds, though negligible at low speed, but help during a slow climb if you have a headwind.

Neither light wheels nor aero wheels are a fad, but aero wheels actually make sense, if you know what you're talking about that is. People "feel" the placebo effect, not the difference.


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## rruff (Feb 28, 2006)

T K said:


> I've often wondered if in say a technical crit one would do well to have a deep section wheel in the front to get the aero advantage and use a lighter shallower wheel in back to be able to jump out of tight corners easier. You'd look funny and get ridiculed, but hey.


Not sure if you realize, but the front and rear wheels both have to accelerate the same amount. Also, if you can stay near the front, there shouldn't be much accelerating except for attacks and the finish. It's the guys in the back who experience extremes.


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## Mike T. (Feb 3, 2004)

rruff said:


> Not sure if you realize, but the front and rear wheels both have to accelerate the same amount.


I was thinking about this on my ride today. I got this scenario in my head of the back of the bike trying to pass the front during acceleration. During steady riding, would the bike get stretched?


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## Kerry Irons (Feb 25, 2002)

*Facts*



bernithebiker said:


> I agree with this, and a totally valid point.
> 
> BUT, consider an day climbing in the mountains. Speeds are low on the climb and the lower weight is a definite help getting to the top.
> 
> ...


Saving 450 grams on the bike/wheels will allow you to save about 35 seconds per hour of climbing a 6% grade at 250 watts. That's a little over a minute for every two hours of climbing.

When you descend, weight is without doubt an advantage. If you are going down something with continuous switchbacks of course a heavier rider/bike will have to brake more but will also accelerate faster out of corners. Until it was made illegal, coaches used to hand up water bottles full of lead shot at the top of mountain passes in the major European races. Of course 450 grams is essentially meaningless, but the effect is there.

Your claim about cornering being easier on lighter wheels (compared to the same weight in the bike or rider) has no basis in science that I can see.


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## bernithebiker (Sep 26, 2011)

All interesting stuff. 

As for cornering on lighter wheels; when you corner you are accelerating, even at a constant speed. So the old F = ma equation comes back into play. More weight = higher cornering forces.

This makes sense; imagine your bike weighed 50kg - getting it round a bend would be tricky. A light bike can be flicked round corners easier. Surely this is why GP motorbikes and F1 cars are made as light as possible?

Personally, I would have refused that lead bottle, unless there were no bends on the way down....(I'm thinking Alpine cols here with hairpin after hairpin for 10km).


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## Kerry Irons (Feb 25, 2002)

*Understanding physics*



bernithebiker said:


> As for cornering on lighter wheels; when you corner you are accelerating, even at a constant speed. So the old F = ma equation comes back into play. More weight = higher cornering forces.


No offense, but you are showing us in repeated statements that you do not understand physics. You are not accelerating unless you are accelerating, and that means changing speed. There is no such thing as "accelerating at a constant speed." Yes, more weight does equal higher cornering forces, but it makes no difference whether the weight is in your wheels or in your water bottle.


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## rruff (Feb 28, 2006)

I agree that he doesn't know what he is talking about... but wheels with lower inertia do alter the feel of the bike when cornering. The rotational inertia has a significant effect on how light the bike feels during those maneuvers. It's debatable though, whether light handling is better than greater stability... and it will depend a lot on the frame and steering geometry as well.


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## OldChipper (May 15, 2011)

May or may not be relevant to this discussion, but I recently used my Zipp 404s for the first time on a local climb that's 7 miles at 2.4% average grade. The Zipps weigh 1662g vs. 1495g for the wheels I normally ride on this climb. The Zipps definitely "felt" heavy, but I bettered all previous times by just over 1 minute. All results are from my Garmin 800 uploaded to Strava and n=8. While that's not the steepest average grade, the climb does have a couple of sections of 5-6% grade. Also not the biggest difference in wheel weight, but overall it convinced me that aero is good, even on long climbs.


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## bernithebiker (Sep 26, 2011)

Kerry Irons said:


> No offense, but you are showing us in repeated statements that you do not understand physics. You are not accelerating unless you are accelerating, and that means changing speed. There is no such thing as "accelerating at a constant speed." Yes, more weight does equal higher cornering forces, but it makes no difference whether the weight is in your wheels or in your water bottle.


No offense, but I have a degree in mechanical engineering.

You are confusing speed and velocity which are different.

This is cut and pasted from Wikipedia 'acceleration';

However, velocity has both a magnitude and direction (i.e. it is a vector), and thus acceleration is also a vector. As such, it describes the rate of change of both the magnitude (the speed) and the direction of velocity.[2][3] This means that an object moving in a circular motion—such as a satellite orbiting the earth—is also accelerating, even though it may be moving at a constant speed.

So, I therefore reassert (correctly), that when cornering at constant speed (not velocity), you are accelerating.

Think about it; it makes sense. When you corner you can feel a cornering force, right?

That's F = m * a my friend.

Someone riding at constant speed and not turning is not accelerating.

Someone riding at constant speed and turning IS accelerating, by the definition of physics.


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## Pitts Pilot (Dec 5, 2011)

I believe that at least SOME of what people are feeling when they suggest that a lighter wheelset makes the bike feel lighter is a reduction in gyroscopic effects from the wheels. If you remove your front wheel - hold it by the axle with your arms straight out in front of you while it is spinning foreward - now abruptly try to LEAN it to the left. The wheel will forcefully TURN to the left, as if the force were applied 90 degrees further along the path of rotation. This is called gyroscopic precession. The greater the mass, the more exagerated it is and I have little doubt that one can feel these forces in situations like standing while climbing - rocking the bike, cornering - leaning the bike.

Since I'm talking, I'll throw in my $.02 on a couple other points.
- When I dropped 400g from my wheels, I couldn't really feel it.
- I do think aero is more important than weight, but both not significant enough to worry about. If you ride alone most of the time (as I do) none of the weight or aero stuff if of much importance.
- I sometimes nearly get blown off the road with my 24mm deep wheels. Deep wheels would have to offer some kind of huge advantage for me to even consider them


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## MShaw (Jun 7, 2003)

rruff said:


> I agree that he doesn't know what he is talking about... but wheels with lower inertia do alter the feel of the bike when cornering. The rotational inertia has a significant effect on how light the bike feels during those maneuvers. It's debatable though, whether light handling is better than greater stability... and it will depend a lot on the frame and steering geometry as well.


I can tell you from personal experience that getting some first gen Cosmics up to speed in a 'street sprint' competition was harder than getting GL330s up to speed in the same competition.

IDK about climbing cause I try and avoid it like the plague

M


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## T K (Feb 11, 2009)

rruff said:


> Not sure if you realize, but the front and rear wheels both have to accelerate the same amount. Also, if you can stay near the front, there shouldn't be much accelerating except for attacks and the finish. It's the guys in the back who experience extremes.


I realize that, but I was going by the theory that the lighter rear wheel would jump or accelerate easier than the heavier deep wheel to get back up to speed. If this is a bogus theory than fine. I won't even pretend to know know a fraction of what some of you guys know on the subject.


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## Kerry Irons (Feb 25, 2002)

*Overthinking*



bernithebiker said:


> You are confusing speed and velocity which are different.
> 
> This is cut and pasted from Wikipedia 'acceleration';
> 
> ...


You are confusing the meaning of acceleration for this discussion. The force generated when turning is centripetal - the mass wants to continue in a straight line and by leaning/steering action you are counteracting that force. The definition of acceleration in the "turning case" is because you are constantly creating new direction vectors - you weren't going in exactly that direction before and so you must be accelerating to get to that new direction at constant speed. Another way to think of it is that the elements of the vector are changing magnitude as your direction changes. 

However, this has nothing to do with the point you are apparently trying to make that wheel weight is somehow different from total system weight when it comes to cornering forces. This is the part of physics that you do not understand or are at least not articulating at all well.


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## rearviewmirror (Aug 20, 2008)

.... omitted.


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## Guest (May 29, 2012)

Pitts Pilot said:


> I believe that at least SOME of what people are feeling when they suggest that a lighter wheelset makes the bike feel lighter is a reduction in gyroscopic effects from the wheels. If you remove your front wheel - hold it by the axle with your arms straight out in front of you while it is spinning foreward - now abruptly try to LEAN it to the left. The wheel will forcefully TURN to the left, as if the force were applied 90 degrees further along the path of rotation. This is called gyroscopic precession. The greater the mass, the more exagerated it is and I have little doubt that one can feel these forces in situations like standing while climbing - rocking the bike, cornering - leaning the bike.
> 
> Since I'm talking, I'll throw in my $.02 on a couple other points.
> - When I dropped 400g from my wheels, I couldn't really feel it.
> ...


The problem with deep dish rims for aerodynamics is they slightly decrease your drag cross section head on, but increase your drag cross section in cross-winds. In a situation such as a climb where ground-speed is low, and there is a strong cross wind, I'd expect aero rims to actually result in a net _increase_ in the amount of drag/ power needed to maintain speed.

I ride mostly solo, and would generally elect for light rims over aero/dish rims (all else equal) becuase of perceptible improvements in handling differences in handling. I agree with your point that the gyroscopic forces are definitely perceptible, even though they're not especially significant as far as saving time on the clock. That said, those minor changes may be worth it for some. 

For example, I ride on a lot of crappy roads with tons of potholes. IME it's a *lot* easier to bunny-hop over crap on the road with a lightweight bike (like my <17lb road bike) than a heavier bike (like my heavy ass commuter which weighs >23 unloaded, with fatter and heavier tires, and weighs much more w/ loaded panniers).

Especially in a recreational riding situation (as opposed to racing), I'd rather have something that gives me marginally better handling / more enjoyable ride, than marginally improvement in speed, since as far as fitness goes it's the effort that counts anyway. 

If I wanted to go faster as a non-racer,IMO it would make a lot more sense to go for non UCI legal aero improvements which are actually significant, such as adding fairings to the bike.


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## bernithebiker (Sep 26, 2011)

Kerry Irons said:


> You are confusing the meaning of acceleration for this discussion. The force generated when turning is centripetal - the mass wants to continue in a straight line and by leaning/steering action you are counteracting that force. The definition of acceleration in the "turning case" is because you are constantly creating new direction vectors - you weren't going in exactly that direction before and so you must be accelerating to get to that new direction at constant speed. Another way to think of it is that the elements of the vector are changing magnitude as your direction changes.
> 
> However, this has nothing to do with the point you are apparently trying to make that wheel weight is somehow different from total system weight when it comes to cornering forces. This is the part of physics that you do not understand or are at least not articulating at all well.


You don't need to explain velocity and vectors to me, thanks all the same!

You said; There is no such thing as "accelerating at a constant speed."

You said; "I don't know what I'm talking about"

You were wrong.

An apology would be nice.

To accelerate from zero to 30km/h requires a force. The less mass, the less force required.

To turn your bike round a 90' corner at a steady 20km/h requires a force. The less mass, the less force required.

Both are examples of acceleration.

Wheel weight IS different from total bike weight because the wheels have a linear AND a rotational inertia whereas the frame and rider is just linear. This creates different equations of motion compared to say a sledge going down a hill (no rotation).

However, I did NOT claim that this is a huge difference. It is minor. 

What I AM saying is that total weight IS an issue in cornering, because every kilo has to be hauled round the bend. Light wheels are part of total weight, whether rotating or not.


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## Kerry Irons (Feb 25, 2002)

*Apologies*



bernithebiker said:


> You don't need to explain velocity and vectors to me, thanks all the same!
> 
> You said; There is no such thing as "accelerating at a constant speed."
> 
> ...


Yes, from a vector standpoint you are correct about how a turning wheel accelerating at constant speed. One term in the vector is increasing while another is decreasing at the same rate.

However this has nothing to do with wheel weight somehow being different than other weight when in turns (or going straight) at constant speed. The total kinetic energy of the system does not change if speed remains constant, and the forces created by turning are no different if the wheel is 400 gm lighter or the body is 400 gm lighter.


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## bernithebiker (Sep 26, 2011)

Kerry, I respect your posts and you clearly have alot of cycling experience. I think there is alot to be gained from going aero, (I run Mavic Carbon Ultimate wheels and I recently bought an aero helmet!) but I still also believe that weight is important whether in wheels or bike or rider. A light bike/wheels feels different to me; I've ridden many bikes, and when I get on heavy one it just feels dead.

If you refer back, I was simply advocating a lighter weight for acceleration and cornering, whether rotating or not. We digressed into whether a basic turn was acceleration or not.

So I think we almost agree; I'm all for going aero, but I won't do it if it costs me too much weight.


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## the_don (Mar 23, 2008)

I personally think the road bike world should adopt some of the Zen that has been acquired in the Fixed Gear side:

1) Style is vital
2) Run an aero wheel upfront with a deep section rim in the back, preferably different colours! Weight doesn't matter, it's all about style, so Aerospokes are just as viable as HED3. 
3) It's not about being the fastest, it's about being at one with the bike. 
4) Playing cards in the rear wheel spokes DO improve a bike.


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