Tubs or Clinchers for Climbing - Does rim weight matter?

bahzob

Over here someone asked about aero wheels.

http://www.bikeradar.com/forum/viewtopic.php?p=15282741#1528274

It led to a discussion where the view was expressed that the weight of rims makes no difference to climbing.

This seems contrary to received wisdom however that dont mean its wrong.

Has anybody got specific examples one way or another of whether changing wheels made any difference to climbing results?

Best would be someone who has used clincher and tube version of same wheel with powermeter and got results of same climb

PS Apologies for putting in beginners but dont know where else to put this. Also a beginner in terms of tubs so thats my excuse...

Diogenes

Lighter wheels are generally a good upgrade to a basic machine. Inertia is lower on the lighter wheel so you can accelerate faster and in general anything that makes you / the bike lighter will improve your climbing. This is where the rub comes though, if you are a super fit rider then you may notice the difference and get up hills a few seconds ahead of the competition. If like me you are a weekend warrior then losing a few grams from the bike is not noticeable.

My simple view is that once you have a got a decent machine weighing in a 17lbs (ish) then getting lighter is very expensive and yields little benefit to the weekend rider.

The weight weenies will disagree of course.

D

Smokin Joe

The biggest single factor in determining the performance of any vehicle is the power to weight ratio. That's why Formula 1 cars use expensive materials to get the overall weight of the car as near as they can to the permitted minimum. Now that's with over 700 BHP on tap, so if it makes a difference with that much power it certainly will with the puny output from a human powered vehicle.

How much difference half a kilo or whatever makes is open to debate, but there are times when I've met a challenging climb at the end of a long ride and wished my eyebrows would peel off so I could be a bit lighter. It's all down to how much you are prepared to spend to shave margins off your time, but going lighter certainly won't make you slower.

Diogenes

Smokin Joe wrote:

The biggest single factor in determining the performance of any vehicle is the power to weight ratio. That's why Formula 1 cars use expensive materials to get the overall weight of the car as near as they can to the permitted minimum. Now that's with over 700 BHP on tap, so if it makes a difference with that much power it certainly will with the puny output from a human powered vehicle.

How much difference half a kilo or whatever makes is open to debate, but there are times when I've met a challenging climb at the end of a long ride and wished my eyebrows would peel off so I could be a bit lighter. It's all down to how much you are prepared to spend to shave margins off your time, but going lighter certainly won't make you slower.

If it works for your eyebrows then my "tash" should certainly come off

I have met many of the hills at the end of a hundred miler, thats where a triple comes in, but of course it adds a few grams to the bike.

D

oldwelshman

The most important thing about the rims is not the weight but the stifness for climbing.
Cheeper or less quality wheels flex and rub on brakes and less efficient.
The weight difference for most wheels would not make much difference, same as if you ate a larger breakfast than usual before the climb
As for tubs or clinchers, dont think you would be going fast enough to worry about the tiny difference in rolling resistance
As for the power meter are you saying you would like to see same power input and compare speed to see if it is diffrent?
As I mentioned in mail to you, when I am climbing with the PT you lent me iy fluctuates too much to read it on a climb

Chris James

Lighter weight helps going uphill. However, the weight differences between tubs and clinchers and rims will be minimal compared to the overall weight of the rider and bike.

Wheels are often an area where weight losses are aimed for. This is because rotating weight has more effect than static. This increases radially with the weight of the rim / tyre counting almost double - i.e. 10g off the tyre would count be the same as 20g off the hub.

HOWEVER, this is only the case during acceleration. At constant speed this discrepancy no longer exists. In fact, due to the extra inertia of the heavier wheel it would possibly be better at constant speeds - hence aero rims for time trialling - the weight doesn't matter that much.

Climbing steep hills is a stop / go process as the bike can almost stall in-between accelerations as each crank turns over top dead centre. These are the circumstance that rotating weight counts double.

Make of all that what you will. If one tyre / rim weight 100g less than another then this will count as 200g in steep hill climbing. If you and your bike weight over 100kg combined this is only 0.2% of the overall weight of your bike. And only helps you up hill. Downhill the lack of weight counts against you!

From all of that, I wouldn’t expect miraculous improvements in climbing due to fitting tubs. If you are a pro into marginal gains etc and are doing a hill climb race then you would get an advantage. Otherwise I wouldn't worry about it.

inseine

The biggest single factor in determining the performance of any vehicle is the power to weight ratio.

I'm sorry smokin Joe but that is nonsense, especially when talking about cars! Power to weight certainly helps on climbs and accelerations but power to drag is what makes you go fast, or not.
Everything I've read suggests that aero is more important than weight even at quite slow speeds, though if you change to significantly lighter wheels they'll feel faster.

dennisn

Love reading these debates, about various cycling questions, but I can't help but wonder
if there is anything about the bicycle that is known for sure. Tubs v. clinchers, carbon v.
anything, saddle positions, aero v. whatever, and on and on. Nothing seems to have ever been settled and decided once and for all. It's all still opinions. Sort of weird in a way.

Dennis Noward

Smokin Joe

inseine wrote:

The biggest single factor in determining the performance of any vehicle is the power to weight ratio.

I'm sorry smokin Joe but that is nonsense, especially when talking about cars! Power to weight certainly helps on climbs and accelerations but power to drag is what makes you go fast, or not.
Everything I've read suggests that aero is more important than weight even at quite slow speeds, though if you change to significantly lighter wheels they'll feel faster.

Nope.

Aerodynamics are more important as your speed increases, they have little or no effect below a certain threshold. Stick tri-bars and a disc wheel on and at 10mph they will do bugger all to make you faster, increase your power output by a couple of % and it will.

inseine

I'd hope to be doing a bit more than 1Omph with tri bars etc!
I don't know which tests you've read but I was surprised just how slow you have to go before weight becomes the defining factor.
I totally agree that a couple % of power will help you, but you said it was the weight that mattered and a couple of % of weight would be about 1.5kgs for most people and the difference between tubs and clinchers is much less than that.

oldwelshman

Inseine, it is simple, on hills overcomming gravity due to wqeight is the biggest issue and as smokin Joe rightly points of for climbing it is the pwer to weight ratio which is important.
On the flat it is not the case it is air resistance which is biggest factor.
It is for this reason that in general good climbers have a very good power to weight ratio, but they do not make the best time triallers or sprinters and vice versa.

inseine

So kind of you to point that out oldwelshperson, but also seem to be missing the point.
The question was whether the weight differnce between tubs and clinchers would make a difference whilst climbing. I'm quite aware of which riders climb or time trial better, but that is not the subject. Weight savings on wheels are generally worth less than aerodynamic advantages even on climbs. Google it if you don't believe me or show me the proof otherwise. I'd be interested.
Try reading the OP first.

oldwelshman

I do not need to be told to read the OP, I did and replied previously. I was merely responding to your reply to Joe after he stated the biggest factor for climbing was power to weight ratio ( which is correct) and you replied that it was nonsense.

inseine

I don't want to get into a war, but are twisting the words somewhat here. Joes comment I responded to was that 'the biggest single factor in determining the performance of any vehicle is the power to weight ratio' which I said was not correct.
Back on topic, I'm as guilty as anyone of weight weenying, but I've seen nothing to back up the idea that lighter wheels make any more difference to climbing than a lighter gut, especally when your talking about a few grams and even at quite slow speeds aerodynamics are more important.

bahzob

Just back and to clarify: My specific question relates to climbing at speeds of 20kph or less so I imagine aero drag will not be a significant factor.

From above I find it is interesting that, contrary to my received wisdom, it does seem the case that from pure physics point of view saving weight in terms of wheels does not make much difference compared to saving static weight on bike (or on self).

Smokin Joe

inseine wrote:

I don't want to get into a war, but are twisting the words somewhat here. Joes comment I responded to was that 'the biggest single factor in determining the performance of any vehicle is the power to weight ratio' which I said was not correct.
Back on topic, I'm as guilty as anyone of weight weenying, but I've seen nothing to back up the idea that lighter wheels make any more difference to climbing than a lighter gut, especally when your talking about a few grams and even at quite slow speeds aerodynamics are more important.

Aerodynamics are important on any vehicle as your speed increases, but by a relatively small percentage. Power to weight is much more important. Put it this way, give me Armstrong's TT bike and give him my winter hack and I still would not get even close to him in a time trial. Give me his power output and let him struggle through with mine and I would crucify him.

Hell below zero !

From the pages of High Performance Cycling By Asker E. Jeukendrup. Chapter 10 Bicycle Frame, Wheels, and Tires, by Jim Martin and John Cobb.Final part of conclusion.
For riders who produce less power and cycle at lower velocity differences in bicycle mass (during uphill cycling) and rolling resistance will produce proportionately greater improvements in cycling velocity. For uphill cycling, equipment selection must balance aerodynamic drag area and weight. Riders who produce less power will perform better with lightweight equipment, whereas riders who produce more power will perform better with aerodynamic equipment. For all riders, whether novice or elite, power is limited and speed precious. Therefore, minimizing aerodynamic drag area, rolling resistance and mass is critical for optimal performance at all levels.

inseine

I don't pretend to know the answer, but all this talk of Armstrong on a winter bike proves nothing. Of course if you had double the power you'd be faster but the savings from using a tubular version of a given wheel over the clincher will be worth about 1watt.
The best aero wheels are worth 10 to 15 watts over an standard 32 spoke wheel, admitedly at 30 miles per hour. Whether they help on the hills depends on how long and how fast you're climbing, but rememeber, you usually have to come back down again!

bahzob

Sorry but I am very familiar with general power vs weight and dont need any more advice on this or the subject of aero advantage, so if you want to carry on discussion do it elsewhere.

My question as think was clear from title was whether anybody had practical experience of advantage or otherwise to be gained from using wheels with lightweight rims for climbing.

Received wisdom is that there is benefit, which makes wheels with tubs an advantage.

Interestingly however nobody has yet said they have gained any noticeable benefit from switching wheels.

Anonymous

Ive got kysrium se sl's which are light and make a difference over my mavic carbon sl's on climbs.

Smokin Joe

bahzob wrote:

Sorry but I am very familiar with general power vs weight and dont need any more advice on this or the subject of aero advantage, so if you want to carry on discussion do it elsewhere.

My question as think was clear from title was whether anybody had practical experience of advantage or otherwise to be gained from using wheels with lightweight rims for climbing.

Received wisdom is that there is benefit, which makes wheels with tubs an advantage.

Interestingly however nobody has yet said they have gained any noticeable benefit from switching wheels.

To answer your question, I recently fitted a new front wheel which is 150gm lighter than the previous one and yes, there is a noticable advantage on the climbs.

Alex_Simmons/RST

Smokin Joe wrote:

inseine wrote:

The biggest single factor in determining the performance of any vehicle is the power to weight ratio.

I'm sorry smokin Joe but that is nonsense, especially when talking about cars! Power to weight certainly helps on climbs and accelerations but power to drag is what makes you go fast, or not.
Everything I've read suggests that aero is more important than weight even at quite slow speeds, though if you change to significantly lighter wheels they'll feel faster.

Nope.

Aerodynamics are more important as your speed increases, they have little or no effect below a certain threshold. Stick tri-bars and a disc wheel on and at 10mph they will do bugger all to make you faster, increase your power output by a couple of % and it will.

You really haven't thought about this very hard, have you?

Alex_Simmons/RST

Here's some actual numbers I posted recently elsewhere:

Impact of improved aerodynamics (faster vs slower riders)

1. CdA (coefficient of drag area) is independent of speed (for speeds that cyclists travel at).
2. If a rider improves their CdA (by whatever method, e.g. better position, more aero wheels), then they will travel faster for the same power.
3. Putting on more aero wheels provides exactly the same reduction in CdA, no matter what power the rider can produce or how fast they ride (ref point 1.)

Let's examine the actual differences for riders of significantly different abilities:

Same mass (80kg bike + rider) and same starting CdA (0.27m^2) and Crr (0.005) (coefficient of rolling resistance). Flat road, no wind. Other conditions constant.
Rider A: 350 watts
Rider B: 200 watts
Rider C: 140 watts
Rider 110 watts
Rider E: 90 watts

Here are the speeds for each rider, with their starting set up as descibed above, and then when they lower their CdA by making exactly the same change to their equipment, say an aero wheelset (which for the purpose of this example, let's say it has the effect of reducing their CdA to 95% of previous value - not an unreasonable estimate).

Rider (W) __ Before ___ After ____% increase in speed
A (350W) _ 44.6km/h _ 45.4km/h _ +1.63%
B (200W) _ 39.4km/h _ 40.0km/h _ +1.61%
C (140W) _ 31.5km/h _ 31.9km/h _ +1.55%
D (110W) _ 28.5km/h _ 29.0km/h _ +1.51%
E ( 90W) _ 26.2km/h _ 26.6km/h _ +1.48%

IOW, there is almost no difference in the relative speed gains made from aero improvements by slower less powerful riders than faster more powerful riders. Any argument that slower riders don't gain the same advantage by making aero gains or using more aerodynamic set ups is utter crap.

Slower riders actually get greater absolute time gains over a set distance because they are on course for longer.

Climbing

Now as for climbing, in almost all circumstance, aero trumps weight. Here is another analysis showing how much heavier an aero wheel would have to be over a non-aero light weight wheel (provided the aero wheels reduced CdA by 5% - again not an unreasonable figure):

Take my same 80kg bike + rider as before. Now let's have this rider climb a hill with lightish (non aero) wheels and compare to the more aero wheel option.

How much extra can the aero wheel weigh and still be as fast (or faster if it's less than this mass penalty) than the non-aero lighter wheel?

Let's say he can push 300W up a hill and his starting CdA is 0.3m^2 (sitting up, say) and using aero wheels would reduce overall CdA by 5%* (over the non aero wheel):

Gradient __ Mass Difference - i.e. How much heavier the aero wheel has to be before it's slower up a climb.
__ 2% ____ 2.84kg
__ 4% ____ 0.94kg
__ 6% ____ 0.39kg
__ 8% ____ 0.19kg
__10% ____ 0.11kg

And if you push 200W up the hills:
__ 2% _ 1.77kg
__ 4% _ 0.50kg
__ 6% _ 0.19kg
__ 8% _ 0.09kg
__10% _ 0.05kg

So, what sort of terrain are you riding over?

Now I'm not here to justify what people spend their money on, nor what elements of their preparation will generate the greatest improvement in their time (training, pacing, nutrition etc).

Simply to point out that improved aerodynamics, even when going up hills (and speed drops), is still pretty darn effective and you can even afford quite a sizeable weight penalty to obtain that improvement.

andrew_s

To put that into context, 200g weight difference on a 200W, 6% climb makes a speed difference of about 0.01 m/s, or 50m on an 80 minute climb.

inseine

That's really interesting Alex. Some figures at last after all our waffling!

bahzob

Thanks Alex.

The thing I dont understand is that this analysis seems to run directly contrary to received wisdom that for climbing lighter is better, especially when it comes to wheels.

You seem to be saying that
- even at low speeds (less than 20kph) when it comes to wheels aero matters more than weight
- when it comes to weight saving, there's not much practical difference between saving weight on a wheel or saving weight elsewhere.

That's not to say this is wrong. To the contrary it may well be correct and if it is then I think it should be more widely communicated as I guess the vast majority of cyclists think as I did.

However, given the wide spread belief that wheels do make a difference I'd still be interested if anyone has conducted a test to check the practice matches the theory. e.g. along the lines as here, (which unfortunately was inconclusive).
http://www.training4cyclists.com/how-much-time-does-extra-weight-cost-on-alpe-dhuez/

bahzob

PS. Just for those of us less familiar with CdA could you give a specific example of a saving.

E.g. what would saving be of using Zipp 404s compared to a bog standard alloy wheel?

PPS Does the same hold for other factors affecting CdA when climbing as well as wheels? I've never heard the argument that when climbing you should think about aero factors (by climbing I mean something over 2km long at over 7%, so something more than just a rise on a TT course)

nickwill

I was told by a very well known wheelbuilder that light rims make a major difference with steep climbing. If two sets of wheels were of identical weight, but one had lighter rims and heavier spokes, it would be better for climbing than one with heavier rims and lighter/ fewer spokes. The argument was that the lighter rims were more efficient in terms of rotational mass. He further argued that for this reason many factory wheels with lower spoke counts were less effective weight for weight than good handbuilts on this sort of terrain. On the face of it, this would seem to make sense.

Alex_Simmons/RST

bahzob wrote:

Thanks Alex.

The thing I dont understand is that this analysis seems to run directly contrary to received wisdom that for climbing lighter is better, especially when it comes to wheels.

You seem to be saying that
- even at low speeds (less than 20kph) when it comes to wheels aero matters more than weight
- when it comes to weight saving, there's not much practical difference between saving weight on a wheel or saving weight elsewhere.

That's not to say this is wrong. To the contrary it may well be correct and if it is then I think it should be more widely communicated as I guess the vast majority of cyclists think as I did.

However, given the wide spread belief that wheels do make a difference I'd still be interested if anyone has conducted a test to check the practice matches the theory. e.g. along the lines as here, (which unfortunately was inconclusive).
http://www.training4cyclists.com/how-much-time-does-extra-weight-cost-on-alpe-dhuez/

I am talking about solo rider scenarios and primarily steady state riding. And in those circumstances, aero trumps weight* in all but the steepest climbs and for the least powerful riders. However you can get light and aero wheels.

* of course it depends on how much extra mass we are talking about.

Rim mass does have an effect on the power required to accelerate due to different moment of inertia.

I did another post on that recently (just can't quite recall where) and demonstrated that accelerating a wheelset with 500g heavier rims (same aero) from 15 to 40 km/h in 10 seconds required 5 watts extra for that 10-seconds. That takes into account the extra non-rotating mass as well as the increased moment of intertia (and if the heavier rim is more aero, then that power differential is reduced slightly). Don't forget with such wheels that they don't slow down as quickly either.

Conventional wisdom is nice, if it's right. I like to validate it with data, appropriate assessment and a little rigour. It was once conventional wisdom that smoking didn't harm you (or others).

Nevertheless, different wheels feel different to ride, have different steering characteristics, different relaibility, different costs, different comfort, lateral stiffness etc etc and wheel choice is not always a straightforward matter. But for riding as fast as one can ride, then aero over light is a very strong ROT.

Alex_Simmons/RST

bahzob wrote:

PS. Just for those of us less familiar with CdA could you give a specific example of a saving.

E.g. what would saving be of using Zipp 404s compared to a bog standard alloy wheel?

See here.
Not showing CdA changes but differences in power. But you'll get the idea....
http://www.rouesartisanales.com/article-15505311.html

bahzob wrote:

PPS Does the same hold for other factors affecting CdA when climbing as well as wheels? I've never heard the argument that when climbing you should think about aero factors (by climbing I mean something over 2km long at over 7%, so something more than just a rise on a TT course)

Yes it does. However on a climb of 7% you probably can't hold an aero position, so the largest improvement to be made, which is to your position on a bike, is somewhat negated. If it's not hot, then a skinsuit would be better for instance than a loose flappy jersey.

I recently analysed a hillclimb TT course for a rider who was trying to decide whether thie lighter road bike or heavier TT bike would be better. It depends a lot on at what gradient the rider can no longer maintain an aero position.