Lighter Wheels - Not faster after all!

[Kalahari Vegmot]

Well I learned something new today.....

 

[dave303e]

still not sold on this

 

On my enduro bike moving between tubliss set up and mousses I have to adjust the rebound about 4 clicks between the 2 wheel sets to get the bike to corner the same and handle the braking/acceleration bumps.

 

But I guess that is more a performance thing not an energy efficiency thing...

[DieselnDust]

Well I learned something new today.....

 

 

 

As Hambini calls him "Bellend"...

Although he markets great wheels the simulation that he talks to likely stacked to favour an outcome that promotes the sale of Swissside wheels (which tend to be on the heavy side).

 

My take on it:

Does the weight of your wheels matter?

ANS: It depends. There isn't enough weight in the wheels for the wheels to have any great inertia effect. The Inertia is in the system and that includes the rider. 

 

But he says we spend far more time at constant speed and not enough time accelerating for lighter wheels to be of benefit!

ANS: A wheel is constantly being accelerated because the moment you take the acceleration away from the wheel it will slow down due to drag. Out in the real world (and not the vacuum of space) a rider is constantly having to overcome gravity or air pressure or both. To maintain constantly velocity against a resistive force you much apply at least an equal and opposite force. So the wheel must be accelerated.

 

So where is the best place to remove mass from a bicycle?

ANS: 1 st prize is the rider, 2nd prize is the wheels,3rd prize is the frame..

lighter wheels still have lower angular momentum so they will are able to change direction with less force being applied. That has a positive effect on handling. Wheels (including tyres and tubes) is still the biggest components on the bike where the mass can be significantly reduced e.g. up to 500gr if you chose components wisely.

 

The only thing I agree with in the video is that within the context of the weight of current competitive wheels the weight differences are negligible. So if you have a 1700gr wheelset and want to loose weight on the bike getting a 1200gr wheelset won't have any inertial benefit due to rotational mass reduction but will have an effect on performance due to the reduction in system weight. There will be gyroscopic benefits that can be felt through the handle bars.

I'd rather focus on getting the feel of my wheelset dialed while also keeping a watchful eye on the total weight because 1kg is hard to loose consistently. if a better feeling wheelset is 100gr heavier I'd likely live with it.

[Schnavel]

But he says we spend far more time at constant speed and not enough time accelerating for lighter wheels to be of benefit!

ANS: A wheel is constantly being accelerated because the moment you take the acceleration away from the wheel it will slow down due to drag. Out in the real world (and not the vacuum of space) a rider is constantly having to overcome gravity or air pressure or both. To maintain constantly velocity against a resistive force you much apply at least an equal and opposite force. So the wheel must be accelerated.

 

This is also the case if you are doing a time trial, where it's a constant pace. However, if you have ever done a race, you constantly accelerating, and a lighter wheel definitely makes a difference.

[ChrisF]

....

 

My take on it:

Does the weight of your wheels matter?

ANS: It depends. There isn't enough weight in the wheels for the wheels to have any great inertia effect. The Inertia is in the system and that includes the rider.

 

.....

 

Partly correct.  Actually totally correct, yet not the full story.

 

 

 

TWO situations exist :

 

1) CONSTANT velocity ... well then the rotational inertia is irrelevant to the rider energy input.

 

2) ACCELERATION .... now here the rotational weight (wheels and gear sets) makes a difference.  It takes a lot more effort to accelerate 100g in a wheel than it does to accelerate the same 100g in any non rotational part of the bike ....  Thus a bike with lighter wheels will feel nippier off the mark.

 

 

but there is a lot more to the total experience ....

[The Ouzo]

Partly correct.  Actually totally correct, yet not the full story.

 

 

 

TWO situations exist :

 

1) CONSTANT velocity ... well then the rotational inertia is irrelevant to the rider energy input.

 

2) ACCELERATION .... now here the rotational weight (wheels and gear sets) makes a difference.  It takes a lot more effort to accelerate 100g in a wheel than it does to accelerate the same 100g in any non rotational part of the bike ....  Thus a bike with lighter wheels will feel nippier off the mark.

 

 

but there is a lot more to the total experience ....

and all of these only take into account a rigid road bike

 

Throw a full sus MTB on an offroad course into the equation and the lighter wheels make a bigger difference to the unsprung mass and handling of the bike.

[DieselnDust]

Yes they do make a difference to unsprung mass. And handling. That's why I say the gyroscopic effects have consequences.

 

Chrishf, under constant velocity no losses the rotational inertia have an effect so if the wheel was spinning along on its own.

But in the case of the ridden bicycle the wheels are 1.5kg and the rider is 60kg.... 15 N vs 600N.

 

2%of the total inertia roughly. The losses of air resistance and friction come into play immediately when we stop pedalling suggesting that their magnitude is more significant than the inertia in the wheels.

also our acceleration is pretty small and velocity is low so the rotational aspects are really quite small. The total mass is of more consequence. In a straight line.

But where do we ride in straight lines along perfectly level roads.

just check out your 1s power meter data and you'll see how often you are applying force to accelerate the wheels