Lenkearney

I have been told the best thing to do to a bike is reduce the rolling weight., ie lighter wheels, lighter cranks, etc.

Why is that?

what difference would one see going to a lighter wheel set?


I imagine there are multiple threads dealing with this- if you could point me to one I would appreciate it.

Len

meanwhile

Most of what is said is about rolling weight is junk invented by marketing people and repeated by people who know nothing about engineering or physics. Ignore the forum threads and read this

https://biketechreview.com/reviews/wh...el-performance

It's technical in places, but the conclusion at the end is easily understandable:

In summary, wheels account for almost 10% of the total power required to race your bike and the dominant factor in wheel performance is aerodynamics. Wheel mass is a second order effect (nearly 10 times less significant) and wheel inertia is a third order effect (nearly 100 times less significant). The best wheels in terms of performance are the ones that are lightweight, aerodynamic, don’t rub brake pads and are strong enough to get you to the finish line.

cnnrmccloskey

"The best wheels in terms of performance are the ones that are lightweight, aerodynamic, don’t rub brake pads and are strong enough to get you to the finish line"
Really? I never would have guessed

deep_sky

++

Guess it ain't all bunk marketing promulgated by know-nothings if it comes to the same conclusions as that article that is supposed to debunk the notion that lighter wheels don't make a difference.

BCRider

I'm not even going to try to read through the details in that article. All I know is that I took about a pound and a half off my wheels by changing tires from some big fat urban jump tires to some lighter wtree slick type tires. The bike accelerated away from a start FAR more quickly than a mere 1.5 lbs would indicate. It turned it from a slug of a machine that I was going to sell into a spirited errand bike that I decided to keep. So I'd have to say that there's something missing in that article or it's focused on only fast riders that ride at a consistent pace where the effects of mass inertia in the wheels truly would be a distant factor. But for a bike that starts and stops often or that changes speeds a lot lighter wheels DOES count for a lot. That same pound and a half moved to my backpack would mean nothing at all. But taking it off the wheels made a HUGE difference. A difference that was felt with the very first moment of the first ride with the lighter tires.

Like I say, it seems like it's dependent on how the bike is ridden. But for bikes that are ridden in an environment where a lot of starts and stops are made lighter wheels DOES count for a lot.

Jeff Wills

Read that again:
"In summary, wheels account for almost 10% of the total power required to race your bike and the dominant factor in wheel performance is aerodynamics."

Light wheels make 10 times less difference than aerodynamic wheels. If speed is the only requirement, aerodynamic efficiency is 10 times more important than weight.

gremlin76

it's rotating weight, not rolling weight. search for it regarding sport/race cars.

basically, if you remove 1 ounce of rotating weight (wheels), it's equal to removing 3 ounces of non-rotating weight (frame).

tonski 

Yea I guess if you just ignore the other part of the quote this is the case.

Just ignore this part and then buy some sub 1k tubulars.

tonski 

Any math to better explain this or is it one of those 89% of numbers that are made up? Spin up time will be less but not much else, and not by much.

AEO

with the speed differences and the way the wheels and tires are designed, the wheels on cars are not quite the same as the wheels on bikes.

I don't recall the exact math or physics behind it, but basically lighter wheels spin up faster than heavier ones. Lighter parts for anything that rotates in the drive train increases engine response, including the wheels. But this is on a car.

BCRider

Trust me, it works on bikes too. My example of the big fat urban jump tires switching to far lighter and skinnier slick tires really hammered that home to me.

An ounce may not make enough of a difference to tell but a few of them and then double it because there's two wheels and it'll certainly make a difference on a bike that starts and stops a lot. On a bike that runs for an hour at a time on a country back road under a rider pushing to train then aerodynamics will count for a LOT more than a few ounces of weight in the tires and rims.

But for someone like me that does a lot more stopn'go errand commuting I'll pick lighter and smaller box section rims over deep V's anytime.

Ya just gotta pick yer poison!

pacificaslim

I just love how these threads bring out the guys who basically argue that the whole rest of the world is wrong and that we should just trust them that lighter wheels don't provide much of a difference. Ok, dude, we get it: you're the smartest guy in the room.

FrenchFit 

Jeez, read the article. Acceleration from a stop is different that spinning at 17mph. This thread proves that the most important department in any bike company's org will always be Marketing.

deep_sky

No, it proves that there is always people out there like you who like to think they are oh so much smarter than everyone else and that they have the inside track on everyone else.
If aerodynamic properties were effectively the only thing that mattered at speed, then I would expect to see no difference between an aero carbon wheel and a solid steel wheel with the exact same shape and aero properties. The fact that I do not see that during TT's and other speed events (pro or otherwise) lends credence to the notion that weight does make a difference. Does a few grams make a difference? Not likely. Would a pound or more make a difference? I'm suspecting that it does.

BTW Tonski, I would not waste money on tubulars for non-racing applications, nor am I some tiny sack of bones who can actually ride a sub 1kg wheelset. That dog doesn't hunt.

dabac

Thing is, how much of that difference is actual performance, and how much is feeling?
I agree that my commuter with 1.25 slicks feels a lot quicker and more responsive than the same bike with the studded 2.1 winter tires (288 studs each). But if I run them at the same pressure, and at about the same level of effort, then the difference in time over my commute is something like 5-8% - and I've got a lot of intersections to get through.

MarkN

So that could be five minutes off an hour's commute - which is something.

I think I could improve performance on my commute by as much as 50%... by shooting all the traffic lights. But that pisses off motorists and pedestrians and generally gets cyclists a bad name which I'm not prepared to do. However, within the range of what I /do/ feeling is more important than actual performance; I want to enjoy my commute. Lighter, more responsive wheels have definitely added to that.

dabac

Indeed it is. But one has to consider that there's a whopping difference between my summer set-up and my winter set up. I'm trading knobblies for slicks, winter outer garments for jersey and bibs, Full pannier for 1/4 load. Boot-like winter shoes w/ electrically heated soles for almost slippers-like summer shoes. Sanded, gravelly roads for swept ones. Bike light riding vs daylight riding etc etc. Not to mention the huge weight reduction to go from 2.1 studded knobblies to 1.25 slicks. Really hard to say how much of that reduction which is due to reduced wheel weight soleley.

MarkN

Sure - but how about my case; 2 weeks ago I went from standard hybrid wheels with 28mm tyres with some tread, to new mavic open pro/LX hub wheels with 23mm slick tyres - quite a weight loss. My commute remains a common factor. My perception is that getting up to speed takes less effort and my top speed on flat roads is perhaps a little faster, especially now that the tyres are a bit more worn in, though I'm inclined to ride gingerly on very rough roads. The biggest difference seems to be descents, where I feel like I've just been dropped off a cliff - I don't remember going quite so fast on the old wheels. I don't know if all of that can be attributed to the wheels though, as I also flipped the stem and removed some spacers at the same time. In any case, I'm having more fun

NightShift

As long as you know the big difference was weight, as this change obviously didn't involve a difference in air pressure, tread pattern, or anything else that would influence contact patch or aerodynamics.

cyccommute 

Yes. By all means reread the article. Pay particular attention to the methodology. The author is talking, almost exclusively, about a bicycle being ridden at a steady state, i.e. 17mph. At zero speed, aerodynamics play no part in the energy requirements to get the bike rolling. Even at low speeds, aerodynamics play little part in the energy requirements to get the bike up to speed. Even at 17mph, aerodynamics of the wheel would have little effect on the overall system because they aren't the major part of the aerodynamic drag of the system.

In the real world, we bicyclists are constantly accelerating...most often from a stop. From a stop the inertia of the wheels becomes more important than at speed. Light wheels are for starting. Once up to speed, their weight is probably insignificant.

NightShift

Rotating weight matters. It may even matter three times as much as static weight (I know there's a better term for that), but when the majority of your energy is lost to wind resistance it's not the biggest factor.

I hope most folks don't need the help of a physicist to figure that out.

And for anyone who hasn't heard the cliche:

It's the rider, not the bike.

Still, all the top riders seem to choose light weight bikes.
You'll get more benefit from lighter wheels (that don't sacrifice strength to the point of deforming or breaking) than from a lighter frame, and more advantage from a lighter frame than, say, taking a book out of your messenger bag.
This doesn't directly address ride quality, which I regard as far more important.

Better to have an aerodynamic wheel than a light wheel. Better a light wheel than a heavy wheel.
Better a strong wheel than a light wheel that is likely to result in your needing dental work.
Lots of things matter. Just make sure you know what your priorities are.

HillRider

Without going into the detailed physics of steady-state vs varying speed, I expect BCRider's and MarkN's experience are due to more than just tire and wheel weight. Going from heavily treaded, lower pressure tires to slick, high pressure tires makes a big difference in rolling resistance and that difference would be quite obvious.

chipcom 

I am the smartest person in the world. Now that we have that settled, the rest of this thread should be more focused on the original subject, which I am way too smart to comment on myself.

dabac

I'm not arguing with your perception, as I've expereinced the same thing. All I'm saying is that IMO/IME the improvement as experienced by the rider is much bigger than the improvement as being indicated by a stopwatch, speedo or other quantifiable method. What feels like a large chunk of difference to the rider is fractional in reality.

In that case, unless you ended up spending money you really couldn't spare, the upgrade was probably worth it. Nothing wrong with looking for that.
I like my radially spoked front (MTB) wheel, as it lets me run the brake pads tight and still not get any brake rub when honking. The speed lost/gained to that is certainly entirely marginal, but it's still nicer w/o any rub.

tonski 

Everything already says they spin up faster, the point is that aerodynamics plays a larger role than weight (within being reasonable).