# Does wheel depth affect hill climbing?



## jiajilah (Jun 23, 2013)

Assuming 2 wheels has similar weight and everything else except 1 with 60mm 1 with 20mm, does one actually faster than the other in hill climbing? Which one and why?


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## tednugent (Apr 26, 2010)

The lighter one has less inertia to overcome


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## jiajilah (Jun 23, 2013)

tednugent said:


> The lighter one has less inertia to overcome


Thanks for your prompt response.
I do understand weight affect hill climbing but I believe I made my question pretty clear that both wheelsets has similar weight and everything similar except the depth.
Thank you.


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## ngl (Jan 22, 2002)

jiajilah said:


> Assuming 2 wheels has similar weight and everything else except 1 with 60mm 1 with 20mm, does one actually faster than the other in hill climbing? Which one and why?


I guess it depends on the grade of the hill. With everything else equal, if the hill was steep (and your speed was low) there would be no difference. If the hill was not steep (and your speed was higher) you would receive a very small aero benefit from the 60mm wheels.


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## MMsRepBike (Apr 1, 2014)

show me some 1100 gram deep section wheels please.


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## Mike T. (Feb 3, 2004)

MMsRepBike said:


> show me some 1100 gram deep section wheels please.


Define "deep section". A quick look found 47.5mm deep Lightweight Meilensteins at 1100 grams.

https://lightweight.info/ca/en/meilenstein


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## jiajilah (Jun 23, 2013)

Hi Mike,

Any "fact" to explain to my question?


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## stevesbike (Jun 3, 2002)

your question was already answered by the aero benefit comment. If you want a more quantitative answer go to analytic cycling and plug in some drag numbers. More generally, look at the drag equation/drag coefficient. 



jiajilah said:


> Hi Mike,
> 
> Any "fact" to explain to my question?


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## jiajilah (Jun 23, 2013)

ngl said:


> I guess it depends on the grade of the hill. With everything else equal, if the hill was steep (and your speed was low) there would be no difference. If the hill was not steep (and your speed was higher) you would receive a very small aero benefit from the 60mm wheels.


Thanks NGL


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## tednugent (Apr 26, 2010)

unless you're climbing a hill at 20+ mph, the aero effects are negligible.


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## woodys737 (Dec 31, 2005)

> Assuming 2 wheels has similar weight and everything else except 1 with 60mm 1 with 20mm, does one actually faster than the other in hill climbing? Which one and why?


The 60mm simply because of less aerodynamic drag at any speed through the atmosphere. 

If you are looking for a wheel set that will help you stay with much better riders I think you will not find it makes much difference. Wheels comprise 10-15% of the total drag on a bike. Interestingly, drag between wheels can be improved by 25% or 2-3% of the total drag on the bike. We're talking less than 1 second and/or a meter or two after a long sustained climb (5km at 8%).

Source: analytic cycling


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## MMsRepBike (Apr 1, 2014)

Mike T. said:


> Define "deep section". A quick look found 47.5mm deep Lightweight Meilensteins at 1100 grams.
> 
> https://lightweight.info/ca/en/meilenstein


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## tednugent (Apr 26, 2010)

jiajilah said:


> Hi tednugent, I was actually wondering would 20mm perform better than 60mm on steep hill. I don't know, just feel like 20mm should outperform 60mm, even the weight is same.


the benefit of aero wheels is more realized at higher speeds.

however though, if you're riding in a condition of a heavy cross wind, the 60mm rim will toss you around more than a 20mm rim.


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## jiajilah (Jun 23, 2013)

tednugent said:


> unless you're climbing a hill at 20+ mph, the aero effects are negligible.


Hi tednugent, I was actually wondering would 20mm perform better than 60mm on steep hill. I don't know, just feel like 20mm should outperform 60mm, even the weight is same.


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## Lelandjt (Sep 11, 2008)

jiajilah said:


> Hi tednugent, I was actually wondering would 20mm perform better than 60mm on steep hill. I don't know, just feel like 20mm should outperform 60mm, even the weight is same.


That's because you correctly assume that all else being equal a 20mm rim will always be lighter than a 60mm rim, therefor having less weight to carry up the hill and less inertia to spin up during accelerations. However, in the unrealistic world in which this question is framed the only difference is gonna be aero. That is at higher speeds the deep wheel has an advantage and in crosswinds it will sap some energy keeping the bike on line.

The correct answer is to find some light, aero 38mm rims and use them for everything. I used to have a 20mm wheelset (Maui gets gusty) and a 60mm wheelset. Sold'em both and I'm very happy with my 1300g carbon 38mm wheelset.


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## cxwrench (Nov 9, 2004)

jiajilah said:


> Hi tednugent, I was actually wondering would 20mm perform better than 60mm on steep hill. I don't know, just feel like 20mm should outperform 60mm, even the weight is same.


If the weight of the complete wheels is the same, we should be able to assume the 20mm rim will be lighter than the 60mm rim. If this is the case, they'll require slightly less power to accelerate, but the deeper rim will be more aero and maintain momentum longer once up to speed. The difference are tiny.


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## stevesbike (Jun 3, 2002)

they won't - as for the effect of wind, drag of a really deep wheel in a strong crosswind (effective yaw angle increases with lower speed) is negative (like a jet9), so the wheel is actually helping to move the bike forward like a sail). 

Even if the deep wheel is heavier, it can still be faster uphill depending on the speed. HED Cervelo etc have white papers on this (tipping points for aero vs. weight). 



jiajilah said:


> Hi tednugent, I was actually wondering would 20mm perform better than 60mm on steep hill. I don't know, just feel like 20mm should outperform 60mm, even the weight is same.


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## deviousalex (Aug 18, 2010)

Flo Cycling Blog: FLO Cycling - Aero vs. Weight - Follow Up

Here they claim that weight is almost irrelevant but I don't think they are taking into account accelerating the wheel. No one climbs at a perfectly constant speed.


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## tednugent (Apr 26, 2010)

deviousalex said:


> Flo Cycling Blog: FLO Cycling - Aero vs. Weight - Follow Up
> 
> Here they claim that weight is almost irrelevant but I don't think they are taking into account accelerating the wheel. No one climbs at a perfectly constant speed.


Yes, they claim weight is irrelevant, based on their limitation of their estimates.

A model is only as accurate as its least accurate assumption.


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## deviousalex (Aug 18, 2010)

Mike T. said:


> Define "deep section". A quick look found 47.5mm deep Lightweight Meilensteins at 1100 grams.
> 
> https://lightweight.info/ca/en/meilenstein



View attachment 299516


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## looigi (Nov 24, 2010)

Inertia (and moment of inertia) is only "overcome" in acceleration. Gravity (weight) is what needs to be "overcome" going up a hill, along with some small contributions from rolling resistance and aerodynamic drag. Power used overcoming drag goes as the cube of the speed, so can become vanishingly at the slower speeds typical climbing hills. Also, body position on the bike is the largest variable in total drag. If you climb sitting up or standing rather than in low in the drops, that will far outweigh any wheel or bike aero contributions...


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## Canadian (Sep 9, 2010)

deviousalex said:


> Flo Cycling Blog: FLO Cycling - Aero vs. Weight - Follow Up
> 
> Here they claim that weight is almost irrelevant but I don't think they are taking into account accelerating the wheel. No one climbs at a perfectly constant speed.


Believe it or not, aerodynamics are far more important than weight even when accelerating. I'll paste an article written by Tom Anhalt below that explains the math. In summary, the force required to overcome aerodynamic drag is 49 times greater than overcoming mass. 

Why Wheel Aerodynamics Can Outweigh Wheel Weight and Inertia - Slowtwitch.com


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## ToffieBoi (May 1, 2011)

Canadian said:


> Believe it or not, aerodynamics are far more important than weight even when accelerating. I'll paste an article written by Tom Anhalt below that explains the math. In summary, the force required to overcome aerodynamic drag is 49 times greater than overcoming mass.
> 
> Why Wheel Aerodynamics Can Outweigh Wheel Weight and Inertia - Slowtwitch.com


The example you have is acceleration from 25mph to 30mph. At those speeds you can't deny the advantage of being aero.
We are talking about hill climbs. The acceleration are mostly from 10mph to 20 lets say. In many cases, there won't be a speed change at all. You will just climb.

If both wheels have same weight distribution (same rim weights especially), there wont be any difference I believe. Even with the tiny small aero advantage of deep rim can be ignored since you are too slow and half watt will not give you anything...


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## Canadian (Sep 9, 2010)

ToffieBoi said:


> The example you have is acceleration from 25mph to 30mph. At those speeds you can't deny the advantage of being aero.
> _We are talking about hill climbs. The acceleration are mostly from 10mph to 20 lets say. In many cases, there won't be a speed change at all._ You will just climb.
> 
> *I'm a little bit confused. How is going from 10mph to 20mph not considered a speed change?
> ...


Take care,


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## Canadian (Sep 9, 2010)

tednugent said:


> Yes, they claim weight is irrelevant, based on their limitation of their estimates.
> 
> A model is only as accurate as its least accurate assumption.


Ryan from BestBikeSplit is in the processing of signing up for an account to answer any specific questions on the model.


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## ToffieBoi (May 1, 2011)

Canadian said:


> I'm a little bit confused. How is going from 10mph to 20mph not considered a speed change?
> 
> Aside from that you said, "In many cases, there won't be a speed change at all. You will just climb.". If that is the case, then acceleration doesn't even enter into the equation and aerodynamics are still very relevant.
> 
> It's a common misconception that you need to be going fast to get an aerodynamic advantage. In fact, slower riders save more time aerodynamically over the course. Here is an article explaining the math behind that.


I didn't say that 10 to 20mph is not a speed change. I said, on most of the climbs, there won't be a speed change and you will climb at the constant speed. Sorry for not being clear enough. 

If we talk considering the FLO blog you sent;
as an example, there is a climb near my home in Istanbul, that I have to climb to go back my home. 2.3km, 8% average. 10 minute is my time. 8mph average speed lets say.
With the chart they put, over 40k I will have 250 seconds of savings at that speed.
If I change from Mavic Open Pro wheels to FLO90s, I will save 17.5 seconds. 

Which is quite good to be honest. Thanks for the information.


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## Canadian (Sep 9, 2010)

ToffieBoi said:


> I didn't say that 10 to 20mph is not a speed change. I said, on most of the climbs, there won't be a speed change and you will climb at the constant speed. Sorry for not being clear enough.
> 
> If we talk considering the FLO blog you sent;
> as an example, there is a climb near my home in Istanbul, that I have to climb to go back my home. 2.3km, 8% average. 10 minute is my time. 8mph average speed lets say.
> ...


You're welcome.


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## Zampano (Aug 7, 2005)

Canadian said:


> Ryan from BestBikeSplit is in the processing of signing up for an account to answer any specific questions on the model.


Excellent.


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## deviousalex (Aug 18, 2010)

looigi said:


> Inertia (and moment of inertia) is only "overcome" in acceleration. Gravity (weight) is what needs to be "overcome" going up a hill, along with some small contributions from rolling resistance and aerodynamic drag. Power used overcoming drag goes as the cube of the speed, so can become vanishingly at the slower speeds typical climbing hills. Also, body position on the bike is the largest variable in total drag. If you climb sitting up or standing rather than in low in the drops, that will far outweigh any wheel or bike aero contributions...


I'm not sure about "vanishingly slower". I was reading an article by Ross Tucker who was does power analysis on the grand tour riders to give an indication if they are doping or not. He was talking about the limitations of his model. He stated that even with a light breeze on a 8%+ hill this can change the power output by 4%.

4% can be very significant. Especially if you consider most people calculate FTP as 95% of 20 minute power. So by reducing your power by 5% (so let's say 15 watts for decently trained amateur bike racer) you can hold that same pace from 20 minutes to 1 hour.


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## ergott (Feb 26, 2006)

Pros are also climbing twice as fast as most of us here do. So make that difference less than 2%.


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## Mike T. (Feb 3, 2004)

ergott said:


> Pros are also climbing twice as fast as most of us here do. So make that difference less than 2%.


Yeah TJ won that hill-climb time-trial in Vail a few days ago doing 24.6mph. I can't average that on the flat anymore. He had all the aero stuff in use.


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## scottma (May 18, 2012)

I can easily do 24 MPH+ on hills. Climbing up the other side sucks though.


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## ewitz (Sep 11, 2002)

Simple answer is NO.

You won't feel a difference. If you are riding fast enough for speed to make a noticeable difference on a climb then in all likelihood you are riding in a group so the aero benefit is irrelevant.


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## stevesbike (Jun 3, 2002)

your simple answer is wrong. Aero benefits don't disappear in a group. And he didn't ask if he'd feel a difference. He asked if there was a difference. 



ewitz said:


> Simple answer is NO.
> 
> You won't feel a difference. If you are riding fast enough for speed to make a noticeable difference on a climb then in all likelihood you are riding in a group so the aero benefit is irrelevant.


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## cxwrench (Nov 9, 2004)

ewitz said:


> Simple answer is NO.
> 
> You won't feel a difference. If you are riding fast enough for speed to make a noticeable difference on a climb then in all likelihood you are riding in a group so the aero benefit is irrelevant.


Nope...you definitely don't understand 'how things work'.


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## November Dave (Dec 7, 2011)

ToffieBoi said:


> I didn't say that 10 to 20mph is not a speed change. I said, on most of the climbs, there won't be a speed change and you will climb at the constant speed. Sorry for not being clear enough.
> 
> If we talk considering the FLO blog you sent;
> as an example, there is a climb near my home in Istanbul, that I have to climb to go back my home. 2.3km, 8% average. 10 minute is my time. 8mph average speed lets say.
> ...


You have to be careful with the comparison sites, and make sure the baseline references are the same. For example, you can either state drag figures with or without the drag of the support struts that hold the wheel in place in the wind tunnel. The majority of drag figures you'll see leave the strut drag in (A2 wind tunnel, where we did our testing, calls it correct protocol to leave it in) but some take it out. If you compare one wheel that's had that drag removed against one where it's left in, you'll be shown an unrealistic gain. 

For example, Zipp shows a gain of 99 seconds for an 808 front/disc rear over a 40k time trial. No one has ever accused Zipp of either downplaying the speed potential of their wheels, or choosing fast wheels to make their comparisons against. So a 256 second gain from the baseline for another wheel would imply that the 256 second wheel offers a 157 second gain over an 808/disc combo in the 40k TT. Which would again imply that the 256 second wheel offers a gain over the 808/disc combo that is 1.5 times as large as the gain made in going from the baseline (Open Pro usually) to the 808/disc combo. 

This completely discounts the smaller variances that happen from one test to another. One company's tire may test differently than another company's tire, even though they are the same make/model. 

Fast wheels do make a difference, and if you are like 99%+ of people in the world, when you ride a bike aerodynamics offer more to gain than weight savings, but you have to consume comparisons carefully. 

Drafting categorically doesn't negate the benefit of aerodynamically fast wheels.


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## deviousalex (Aug 18, 2010)

November Dave said:


> if you are like 99%+ of people in the world, when you ride a bike aerodynamics offer more to gain than weight savings


What would you say that 1% is? For example I generally do between 3k and 8k ft of climbing on my rides. Am I part of the 1%?


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## November Dave (Dec 7, 2011)

I would pretty much call the 1% those guys who do those crazy steep English Hillclimb races. One, maybe 2K, at about a 15% average grade


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