Tuesday, December 14, 2010

Wrong About Being Wrong About Weight

Over the past week, the bike-related portion of the internet has bloomed with references to a study in the BMJ which "proves" that a lightweight carbon bike is no faster than an old steel bike for commuting. Now as someone who has logged far more miles on steel bikes than carbon ones, and who is often heard to grumble "you don't need that" in reference to some latest, greatest bit of techno-gee-whizzery, you might think I'd be one of the many joining in the chorus of voices chanting "nah-nah you weight weenies are so damn wrong!" That's not what I'm going say.

What I am going to say is this. The people who think weight doesn't matter are wrong. And the people who think weight is the only thing that matters are wrong. And when you get down to the heart of it, none of us really believes either of those extremes either. The truth lies somewhere between.

Now this study, done by a doctor and published in a medical journal proves one thing really well: People will take one very limited study (sample size of one!) and if it confirms their notions of how they think things are (or should be) they'll point to it as "scientific proof". It's not.

I walk to work these days. The trip is four blocks over flat terrain. I could randomly flip a coin to decide if I'm going to wear sandals, running shoes or hiking boots for my commute. Let's say I track my commute times for six months and they turn out to be exactly the same. From this do we conclude that I'm an idiot for having three different kinds of footwear? Or do we conclude that people who buy sandals are idiots? Or do we conclude that, yes, I really do have too much time on my hands?

Over the years I actually have bike commuted various distances (depending on my jobs my bike commute has been as short as a mile each way to 20 miles each way) and I have found that weight of my commuting bike is one of the least important factors to commute times. On my commutes I've found many factors that matter more than weight. Timing at stoplights, traffic, wind & other weather all have a much greater impact than dropping a couple of pounds off the weight of my bike frame. But in other circumstances, a difference in weight can be an appreciable difference.

Weight isn't trivial. Ounces add up to pounds and when the road goes up you notice those pounds. Ask any experienced bike tourist if weight matters or not. If they've been on the road for a while, the odds are they've sent some things home. And it's not just about speed, sometimes it's about comfort. I'm sure many a tourist has packed panniers and trailer with all the comforts of home only to realized when climbing some mountain pass that those comforts aren't making them very comfortable at all.

It comes down to figuring out how much weight matters to you, in your circumstance. I remember being in my first real road race, more than thirty years ago. It was a hundred-plus mile road race and as we neared the end, I saw one of the fast guys, the guy who tended to win everything, pour the water out of his bottle. "Lightening up for the sprint," my buddy told me. The rest of the peleton took this as a cue and we all started tossing full bottles and Silca pumps into the ditch. I swear I saw the color of at least a few jersies shift to red as the hammer dropped and the sprint ripped the pack to pieces. Weight mattered a hell of a lot in those few seconds.

For commuting and your commute, maybe weight isn't what you need to worry about. Analytic Cycling is a good site for those of us who like to play with numbers to see how various factors relate to bicycle riding. Weight matters a bit and so do lots of other things. At the end of the day we all get where we're going.

Keep 'em rolling,

Kent "Mountain Turtle" Peterson
Issaquah WA USA




21 comments:

Gunnar Berg said...

Yep. What you said about weight.

I like steel bikes and Brooks saddles - probably 'cause I'm old and I grew up with them. I also like equipment that doesn't easy fail.

Within those parameters, the lighter the bike, the better. To believe otherwise is just bullheaded stubbornness.

Bob said...

I just read the article and it sure is some interesting "science". It took him the same amount of time (except when he was chasing a colleague, then his time decreased) with less bike weight. No mention of effort expended. Assuming the gearing was similar and he used the same gears I would not expect a decrease in time.

BTW, no bike would be zero weight, but would take more time for the commute.

The Velo Hobo said...

I’m pretty weight conscious when I tour, but for every day riding, I really don’t think it matters. Okay, it’s not that weight doesn’t matter…it’s that time doesn’t matter. I could shave my eye brows to gain 1/100th of a second, or I could ride a fully carbonized bike and gain a minute or two. But I’m not in that big of a hurry. Admittedly, I ride both a light weight aluminum and carbon bike and a steel bike. I enjoy both equally and while the aluminum and carbon bike may be faster, it’s certainly not noticeably faster. Perhaps if I bothered to “time” a route on both, I might see a difference of a few minutes. But really, what’s a few minutes if you’re having fun.

Now touring, that a different story. Lugging a bunch of gear up one mountain after another and you’ll soon be thinking about tossing that extra pair of socks in the trash or breaking your toothbrush in half. But it’s not about shedding weight to be faster, just more comfortable.

Great post, as always. Jack

Anonymous said...

I think about weight often, I've got a little background concerning weight.

Weight takes many shapes & forms [we all mostly know this, but how much we think about it, I am not so sure]:
A. Real Weight
B. Imagined Weight
C. Physical Body Weight
D. Emotional or Mental Weight

...I am sure there is more out there, but those are the ones that pop into my mind the most often.

The thing with weight is this:
It's only relative to where you are at any given moment, and the increase/decrease of it is gradual and therefore relative to where you were then as well. For instance: folks will tell -not ask- me, "You must feel so different," having shed some weight over the past handful of years, "now that you are so much smaller" and it's odd because they don't really frame it as a question so much as a direct fact. The truth is this though, I don't feel that different... I can react to the Now [or yesterday's ride, etc] and beyond that, if I dig deep into my memory bank, then -- and only then can I reference some type of difference between me then [at 501 pounds riding a bike] and now [at 170 pounds riding a bike]. It's all too gradual to compare.
That said, what I find most odd in the Bike World regarding weight and the endless climb for less of it within bikes & bike gear is this: weight aside, one only goes as fast as their body allows... so to me, it's all moot.

Heavy is stable: when I rode as a heavier person... I felt more stable [perhaps that is one of the reasons that now, as a less heavy person, I elect to ride a Surly Pugsley as my 'Go-Fast' bike?... I don't know].

Skinny people ride bikes loaded down with their possessions and heavier folk, sporting beer-bellies, ride carbon with nothing but a micro tool kit [racers aside, who of course want the most even playing field within gear, the pursuit of less weight is somewhat a mindless endeavor when it comes to bicycles].

Somewhere betwixt those two resides the truth about weight, but I wouldn't really claim to understand either variety of person... because, in the end it's a relative.

I do know this though... people who ride a lot seem to be less absorbed with all this weight stuff. Perhaps that is because they are too busy riding and therefore not reading about the latest gear to care much?

Relative, again.

-Scott Cutshall

Gunnar Berg said...

"Skinny people ride bikes loaded down with their possessions and heavier folk, sporting beer-bellies, ride carbon with nothing but a micro tool kit."

I like that.

Michael R pdx said...

maybe to butcher an Eddie Merckx observation:

Don't buy weight off, ride weight off.

kfg said...

"Skinny people ride bikes loaded down with their possessions"

I'm skinny people. I've been known to self support tour. In the mountains. Frankly, I haven't a clue what people on those Winnebago bikes might have stuffed in all those huge bags, or why.

Old tube ham radios? Gas grilles? Matched sets of white elephants? An IBM 360/85 (this computer came alive) complete with spastic golf ball? Broad spectrum nuclear deterrent capability?

What?

Bob said...

KFG asked "Frankly, I haven't a clue what people on those Winnebago bikes might have stuffed in all those huge bags, or why."

Probably 3 of everything plus anything that might be needed for any contingency plus a bunch of supposed comforts and conveniences. Once when I was backpacking I saw a guy carrying a Duluth pack with a 5-pound bag of potatoes dangling from the bottom.

Marcy said...

As one whose personal weight tends to fluctuate, this is the only weight on the bicycle with which I concern myself. It makes absolutely no sense for me to spend thousands on the lightest bike available only to be carrying twenty-five extra pounds on my person. Of course, I'm also no longer concerned with winning the race, but rather enjoying the ride.

Ride Happy!

Anonymous said...

One thing most folks seem to have lost sight of is that that article was done in a spirit of levity - tongue in whaddaya call cheek, don't you know. It certainly has sparked some discussion, though. For myself, the main distinction is between "functional weight" and "non functional weight." My problem is that I keep deciding that more functions are necessary - I really love the fact that my bike works as a table, bench, storage locker, wardrobe, battering ram, etc. I can ride things that are "just bikes," but I prefer not to. Val

RJ said...

Ride with as much weight as you like-- that's how I feel!

CHEERS!

Also, I'm comin' to town!

http://anadventurecalledbicycling.blogspot.com/2010/12/issaquah.html

Maybe I'll see you around, Kent!

Anonymous said...

I'd like to tour light, but I have to bring all the stuff that the ultralight touring folk neglected to bring and want to "borrow."

Vik said...

The tires you select are far more important to slower speed riding than a few pounds on the frame.

Anonymous said...

If you go to the homepage of the website for the British Medical Journal (), you will see that this article, and many others labeled "Christmas 2010", are written as humor, or at least, they are light-hearted breaks from the usual journal articles. It is a tradition the Journal honors at this time of year. The bike article author seems to be gently poking fun at himself, and other cyclists. He certainly isn't presenting it as earnest research.
Tom Horne

Anonymous said...

As my bike commute is one of the nicest parts of my day, I'm not the least bit concerned if it takes a little longer. I ride my slowest bike and add an extra 3 km to the 7 km minimum distance.

Susan in Vancouver

Dan O said...

The weight argument is an interesting one. Here's my take on it, with a semi-scientific experiment:

I've commuted a few hundred times from Kenmore to downtown Seattle, 17 miles each way, so 34 miles daily. Most of my commute is the flat Burke-Gilman trail, though a few hills are tossed into the mix - Eastlake in Seattle and Simonds Road in Kenmore (I actually peel off Simonds onto a steeper side road).

I commute with two different bikes, both now have 10,000+ miles on 'em (one more like 20,000+). One bike is a '97 Ibis Hakkalugi, steel frame and fork, fenders, etc. I've never weighed it, but would guess 21 -22 pounds or so.

The other bike is a '07 Ibis Silk Carbon, carbon frame and fork, so maybe 16 pounds or so.

I don't time my commutes to the second, but have times hundreds of them to the minute. Guess which bike is faster or slower?

Turns out, it doesn't matter. Yes, the carbon bike feels faster and snappier, but the stopwatch doesn't lie. As a matter of fact, my record time for either commute remains on my older steel Ibis - from a few years ago. Then again, I'm probably getting slower with age (almost 50 now).

Sure, in a flat out sprint or up a steep hill, the lighter bike will have an advantage. What I've found out however, that difference is much smaller the you'd think.

LJS said...

The so-called 'randomised trial' that the cycling Doctor reports in the British Medical Journal article is pretty flaky science, actually. see my post on the subject

ericracesbikes said...

It makes me laugh to see so many people concerned with what someone else is doing or saying. I say if you like something a certain way- more power to you! Go with what makes you feel good.

When I'm commuting I couldn't care less how much my bike weighs. When I'm racing you can bet I pare my rig (and myself) down...acceleration makes a difference in that context. Other than that...to each his own!

Enjoy your ride,
-Eric

Susan Tomlinson said...

Good post.

Andy said...

I think this "study" shows absolutely nothing. The n=1 study could easily mean that the rider went 15mph on both times to arrive at the destination at roughly the same time - though the applied effort would likely be 10-30% more on the heavier bike.

Ride 20 miles around 10mph on flat ground, and you probably won't find a significant difference in time or effort. Then try riding 20mi at 18mph average with some hills, and tell me that a lighter bike isn't worth it.

If you have a short, or flat, or slow commute, than just get a cheap cruiser bike and you'll be fine for getting from A to B. But if you like to push yourself a little while riding, burn some calories, and keep up with traffic downtown, than by all means take the light go-fast bike.

Spiny Norman said...

"The applied effort would likely be 10-30% more on the heavier bike."

You haven't run the numbers, then. The energy that you expend to move a bike forward generally has a lot more to do with frictional losses (wind, bearings, tires, seat padding, pedaling inefficiencies), and bike weight has negligible effect on frictional losses. So even if the ride begins in a valley and ends on a mountain top, a 10% difference in bike + rider weight is unlikely to equate to a 10% difference in time — let alone 30%.