Panza

People say that the biggest change you can make on your bike, aside from perhaps the saddle, is the wheels. With entry level rims weighing over 2000 grams, going to a proper performance wheel should make pedaling easier. How much of a difference was it for you guys when you slapped some quality wheels on your ride?

twolegs

i wouldnt say top quality but i got some older mavic MA40's and it made a whole lot of difference.. the bike felt more like a flying carpet with those on .. well worth it

JerrySTL

Not all that much. I could tell during accelerations and thought I could tell when climbing. A somewhat heavier, but more aero, set of wheels seemed to be faster while cruising around. If you could find a lighter, more aero wheelset than you have now, all the better.

However since I no longer race, I only think about buying new wheels when the set I have now are giving me problems. I certainly wouldn't spend north of $1000 just for a pound less.

andr0id

WUT???

Road or MTB?

Please give some examples!

For example a Velocity Atlas, which is a monster rim that is suitable for use on a tandem, is only 620 grams.

LesterOfPuppets

I'm guessing by rims, you mean wheels? Road wheels? Even my olde, cheap rear road wheel is a hair under 2000 with a cassette, rim tape and skewer.

MTB wheels? I'm too poor to loose a pound of wheel weight but on MTBs I can often drop over a pound per wheel pretty easy with a $50 tire investment. And yes, that feels nice.

I used to get Mythos XC for $30 a pair but now I go for the even lighter Kenda Klimax Lites, for $50 a pair.

Kenda Klimax Lite XC 26" Tire | Kenda

fietsbob

between punctures of the superlight tires/tubes? probably fine.

LesterOfPuppets

\

I run standard-weight tubes and Mr. Tuffies. 120-gram per wheel penalty for the Mr. Tuffy, but it's worth it.

cplager

Better rolling tires will make a much bigger difference than lighter wheels.

If you've got crappy hubs, you'll notice replacing those.

Homebrew01

fixed

First, spend a bit on good quality tires, maybe 25mm at 90 psi or so and you should have a nice ride.

cyccommute 

The problem is that many "performance" wheels are just as heavy as entry level wheels. I had a set of Vuelta wheels that I replaced with a set of wheels I built (White Industries T-11 hubs with Ti free hub, Pillar PSR TB2015 spokes and 32 hole Velocity A23 rims). I dropped 2 lbs in weight by going to the new wheels and I can definitely feel the difference on climbs and acceleration. I built a similar set of wheels for my wife and her overall speed has increased significantly as well...and she's mostly a casual rider.

On the plus side, I ended up with superlight nearly bomb proof wheels.

Tire rolling resistance is vastly over rated. Yes, it is there but it's only a tiny fraction of the overall resistance on the bike and becomes a smaller percentage as speed increases. Over about 7 mph, aerodynamic drag becomes a much larger force that has to be overcome. Since mass is part of the force equation, the more mass you have to push into the wind, the more energy you have to put into the system to overcome that force pushing back on you.

andr0id

That depends on your roads. CO had nice smooth roads (at least everywhere there I have been) so any tire will perform well. In TX we have a lot of rough chip-seal and rolling from a smooth paved road onto that will immediately knock 1 or 2 mph off your speed. A wider, good quality tire here makes a more significant difference.

Wilfred Laurier

mass has an affect
but only during acceleration and climbing
it certainly has no effect on aerodynamic resistance
if that is what you were trying to say

Kopsis

Mass isn't part of the equation. Force due to parasitic (aerodynamic) drag at subsonic velocities is 1/2 * air_density * velocity^2 * drag_coefficient * frontal_area. Mass does affect rolling resistance, and (to a much smaller extent) drivetrain loss. It also affects acceleration and gravitational force. But since those factors are proportional to velocity and drag is proportional to velocity squared, at non-trivial speeds drag quickly dwarfs all the other forces. So if the forces affected by mass are 10% of the total force the rider has to overcome, a 1% drop in overall weight is going to net you a 0.1% performance gain.

People notice reduced wheelset weight accelerating from a stop and on tough climbs because in both cases, the bike is moving slow enough that drag force doesn't yet dominate. At 20+ MPH, a couple pounds in the wheels makes very little performance difference. But because riders feel it on the way to 20 MPH, the brain is easily "tricked" into believing that it continues to matter at speed.

cplager

The switch over point is much closer to twice that value.

No, rolling resistance isn't underestimated in importance for anybody doing less than 15 mph. Yes at the high end aerodynamic drag becomes much more important, but for most people here, rolling resistance is very important.

P.s. of course where the switchover point is depends a lot on the individual and her bike. Somebody riding on crappy tires is going to find it much higher than somebody already riding on fast skinny high pressure tires.

cyccommute 

If you are pushing against a force, you are accelerating. That's what force is...mass times acceleration. Newton's first law says that an object will stay in motion except when acted on by an outside force. For a bicyclist, that outside force is wind resistance (and hills but that's different matter). Thus we are always having to put energy into the system through force on the pedals to keep the bike moving forward. Our speed is never steady and, unless you are stopped, you are accelerating...either negatively or positively.

First, you can't talk about any kind of force without taking mass into account. That's the definition of force. "Air density" has a mass component to it as does the drag coefficient. But I'm not talking about the air moving. The air isn't moving, the bicycle is. Force has to be put into the system to keep the bike moving through the air or it stops. That force is definitely related to the mass of the bicycle. It may be small on an instantaneous basis but it has to be integrated over time. The energy costs adds up and eventually the engine, i.e. the rider, runs out of ability to make forward progress.



You've got your units wrong. Rolling resistance and air resistance are equal at about 12 kilometers per hour or 7 miles per hour. See here By 15 mph (25kph), rolling resistance is well on the way to becoming negligible when compared to wind resistance. It's still there but the air is pushing pretty hard by 15 mph. You are having to put out 100 W of power to stay at that speed and less than 10W is need to overcome the rolling resistance.

Kopsis

No, that's a complete misinterpretation of 2nd law. F = ma does not define force. It simply says that F is the amount of force required to produce acceleration a in mass m. You can produce a force without any acceleration. Stand in a doorway, put your arms out against opposite sides and press. You applied a force, but nothing accelerated. Acceleration is (by Newton's own definition) the change in velocity with respect to time (dv/dt). If velocity remains constant, there is no acceleration, no matter how much force you apply.

Yes, the rider has to put energy into the system to produce a forward force equal to all the opposing forces in order to maintain a constant velocity. And yes, it's impossible for instantaneous velocity to remain absolutely constant in real life - but the small positive and negative fluctuations (due to pedaling and road imperfections) cancel making net acceleration zero and therefore removing mass from everything except rolling resistance and drivetrain loss.

cplager

It depends on your inputs. This calculator shows a cross over point at 16 mph, which is 10 mph. But that's with good tires. With a lot of tires, rolling resistance is much worse.

cplager

Yes. This.

Bandera

Assuming that you were riding a wheelset in good nick (true & w/ good bearings & rubber) you might "feel" a bit on acceleration, but that can be a placebo effect.
Where weight does matter is in racing where accelerations/decelerations (big & small) come often and irregularly. The peloton is a lively environment and a good set of race wheels w/ top line tires help to preserve that tiny bit of grunt or spin just necessary to maintain contact or cross the crucial gap. Although there is no substitute for having a cadre of beefy teammates to draft behind aerodynamics make a big difference at pace. A well selected set of race wheels is as light as possible w/o being delicate, aerodynamic w/o being unmanageable in crosswinds and hangs on a hook until the next event. For me the jury is still out on carbon rims.

For solo riding quality hubs well built w/ a reasonable spoke count/ rim height and have at it.

-Bandera

Wilfred Laurier

you are wrong

mass has absolutely zero effect on how much air resistance acts on a moving body
however
it can affect the result of air resistance

a heavier body will decelerate less than a lighter body
if the only force acting on them is air resistance
and all other things being equal

GeneO 

+=1. You have to supply the same opposite force to overcome the wind force no matter what your mass is. Mass only comes into play in acceleration and climbing as Wilfred and others said.

Sullalto

How would you measure your frontal area and drag coefficient? I suppose you could work backwards if you had a power meter+speed+you were a very steady rider...but other than that, how?

wayniac

WOW! You guys are really serious about this stuff. These comments are mind boggling. I can't wait until my road cycling extravaganza develops into my brain thinking about such things. Awesome!

cplager

It's a very good question. There's a program called cheetah that does this (using a power meter and a closed loop track). If you know the elevation well of a hill, you can get it from many GPS tracks on the same hill. Aerodynamic drag isn't obvious at all...

cyccommute 

You may want to go look up Newton's laws and the definition of force. Every definition of force that I've every seen is expressed as F=ma. If you want a more wordy definition, there's this from Wikipedia

Newton's Second Law can also be expressed as

Now your the one that is misunderstanding Newton's Second Law. Look at the Wikipedia quote again. When you push on the doorway (or a house or the world), you aren't changing the momentum of the object except in extremely minute quantities. It's just too big to make a noticeable change to it's momentum to the human observer. But you are changing the momentum of the doorway (or house or the world). You can "feel" it in your arms as you push. That's force. And it is most certainly related to the mass of the object...massive in the case of the doorway, extremely massive in the case of a house and almost incomprehensibly massive in the case of the world...and the acceleration imparted into the object.

Now if you get a more massive object or something to impart more force to push on the doorway (or house or world), you can overcome the mass and get the object moving. If you were to put a hydraulic jack in the doorway and apply force with that you could move the door jamb in the wall. You'd break the door jamb and probably the wall but you would get the jamb accelerated and moving.

Try to "push" on anything without using force. You just can't do it.

Nope. You are moving the bike through the air. The bike has mass. The air has mass. To move the bike, you have to put force into the pedals (push them down) to put force to the tires to push against the air as the bike moves forward. The faster you go, the more the air pushes back and you get to a point, very quickly, where you just don't have enough power to push against the air to gain speed. Drivetrain losses are vanishingly small and rolling resistance quickly becomes only a small part of the problem. If the air itself is moving, the power, and therefore the force, needed to push against the air is even greater.