Lighter wheelset question

I have a rookie question. By switching to a wheel set that is approx. 275g lighter, how will that affect climbing? A little easier or a lot easier? The question stems from hearing a couple people discussing "rolling weight" saying it had a greater effect on feeling the weight of the bike when climbing. I am curious to weather there is any validity to this concept.
Thanks,
Carlton

The idea that wheels with lighter weight (or more specifically, lower moment of inertia) makes noticeable performance improvements is, well, myth. It's been shown mathematically just how small the performance changes are, even with large differences in MOI.

Our bodies aren't very good sensors and are too easily influenced by non-physical things.

__________________
Sex is horrid
Pain is Fun
I cut my fingers off
One by one

So I would see a negligible difference in climbing and spending the money on a lighter set would not be worth it?

Exactly. Any benefits would be psychomological. That money would be better spent on a PM (if you don't already have one). There are very few short cuts to getting faster; train more.

The difference would be very small, yes. Keep in mind, this is 275grams off of a total weight (bike + rider & gear) of maybe 80-90kg or more, so that's about 0.3% or so. Further, the actual performance benefit of 0.3% less weight will be even less than that, at least if you're going faster than 10mph. On average, you're probably looking at less than a tenth of a percent in performance gain, which is really within the noise of the variability of all the many other parameters that affect your performance.

Whether or not that's worth it is a different question, though. Some people still find those newer, lighter wheels "noticeably" better subjectively, and for some people 1000 bucks is peanuts compared to that feeling...

Well, worth is a personal value. If the wheels get you more excited about riding, then they could be worth it, but don't expect to see big changes on the computer. I had a set of wheels that together weighed 880g. Now I have two wheelsets that weigh in at 1380 g and 1385 g. I can't really tell any difference in performance of the wheels on steep climbs (12%+), even though the difference in weights was 505 g. That's a 1.1 lb difference. The magnitude of the difference in moment of inertia is at least as much between the wheelsets.

If I were going to buy another wheelset (keep in mind there are a lot of mountains to climb 'round these parts), I'd:

1. Get a durable set of wheels
2. Get a set of wheels that really lit my fuse.

Aero wheels are a much better purchase than lightweight wheels.

__________________
Sex is horrid
Pain is Fun
I cut my fingers off
One by one

Thank you very much for your advice. I already love to ride no matter what the wheel set and fully understand climbing will get easier the better my endurance and overall shape. I had just had "heard" my original statement from a couple and wondered if it was valid or people talkin out their azz. Again, thanks for all advise!

Lew Racing Wheels or Lightweights?

... or were you just making that up?

LEW VT-1's.

I have to admit I didn't stay at a Holiday Inn last night. For anyone that thought I did, that story was made up, except for the part about the female wrestlers, the badminton racquet, and the 3-in-1 oil.

__________________
Sex is horrid
Pain is Fun
I cut my fingers off
One by one

mathematically you can accelerate and decelerate faster with lighter wheels. It is proven on cars, and it should apply to on bikes.

This is due to a lower inertia.

But climbing is not about accelerating, but about keeping the pace ... so you would then be better of with some heavier wheels (they are less likely to decelerate ...)

light wheels will only give you a good advantage in sprints.

Mathematically a log 2.000000001 m long is 1 picometer longer than a log 2 m long. Does it matter? Mmmm, no. Just because something is mathematically larger doesn't mean that size difference is significant. When doing science, you have to keep in mind the context, and you have to apply things properly. First, lighter does not equal lower moment of inertia. MOI is a function of mass AND mass distribution. Second, the difference in acceleration between bicycle wheels of varying MOI is very small, even when the difference in MOI is large. Farting might make a bigger impact than a lower MOI.

Mark McM, at Weight Weenies addressed this issue and produced an equation of motion for a bike (a differential equation) that accurately calculates the effects of varying MOI on acceleration. The net result? The differences in acceleration are essentially negligible. Here it is: Weight Weenies • View topic - Rotating Mass... . In his post he applied his model to climbing, but the math is exactly the same with sprinting. If the sprinting is on level ground, you just set the slope term, S, to zero.

In short, the idea that light weight wheels make a significant performance difference is a myth. They can make a big psychological difference, but that's got naught to do with the physical reality.

__________________
Sex is horrid
Pain is Fun
I cut my fingers off
One by one

Sorry, I don't see your point here. The calculation you reffer to says the same as I said.

Heavier wheels can even be better while climbing => check the calculations

There is one important thing to mention if you fall back on the calculations: it is a steady situation = steady pedal rate!

If you would rewrite the calculations to an acceleration-situation, you would see that weight is important overthere...

I've seen in many times on race-cars, lighter tyres give better acceleration times.

__________________

I recently purchased some handbuilt wheels. While weight was part of the equation, I think the following ended up being much more important:

- after a Q&A with the wheelbuilder he learned of my riding style, needs, and we determined what would suit me
- the wheels are well built, will need less maintenance in the future and can take a pounding (they have already, though you wouldn't know it)
- they come with great service (at no extra charge)
- and with regards to climbing, the wheels are stiffer (though not any less comfortable than my previous wheels) and I have noticed an improvement in climbing

Good luck.

Oh? You did the numbers? Really? What did you use to solve the diff eqn? And again, you miss the context and the relevance of the differences. The differences are very small.

Steady state? Really? Do you know someone who pedals in perfect circles, i.e. applies exactly the same force at every point on that circle? No, you don't. Cycliist typically pedal ellipsoidally when it comes to the application of force to the pedals. Therefore, since the force varies around the pedal cycle, there are accelerations. Go back to physics 101 and review the mathematical definition of force. At any rate, none of that matters because.........wait........wait..........wait.................here it comes......................it's an equation of motion! It's valid for steady state and non-steady state situations. Do want to know how to make that equation represent a steady state? See that dV/dt on the left? That stands for.......here it comes again..............acceleration. If you make that 0, guess what happens? That's right! There's no acceleration. It then is an equation representing a steady state! La voila!

To show just how much you don't understand the physics of what you're talking about, answer these questiions:

1. How big is a car wheel/tire combo's MOI compared to a bike's?
2. How fast does a car accelerate (Remember that dV/dt thing?) compared to a bike?

Again, you keep losing a sense of the scale with which is being dealt. Next you'll likely be alleging that if a spoke breaks, wheel pieces fly out in every direction because that's often what happens when a turbine blade breaks in a jet engine.

You haven't even put a number to how much acceleration changes with changes to a car wheel's MOI.

__________________
Sex is horrid
Pain is Fun
I cut my fingers off
One by one

The topic you mention has some resolutions itself in it ...


What are you trying to say here? Is there any cyclist intrested in the accelerations on one pedal-move?

I am talking about accelerating from 0 to 40 km/h or from 35 to 60 km/h ....

The calculations are not ment for that ...

about 12 kg per wheel, and a total mass of around 400 kg (including the driver)

so that will be more or less the same as a bike


Ok, there you have a point, mucht quicker, but it is then also an over-powered system that should have less effect from inertia.


1kg per wheel could be a difference of 0,3 seconds from 0 to 100km/h (2,7s to 3s)

so less than 10 % weight-difference resulted in more than 10% extra time from 0 to 100km/h


BTW the difference only has to be 1 inch to win a sprint ;-)

__________________