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Weight Weenie pop quiz(36 posts)

Weight Weenie pop quizContinental
Dec 10, 2003 7:57 AM
This is a 2 question pop quiz is for all the weight weenies who insist that removing a few hundred grams from their bikes is essential to their cycling pleasure and performance.

1. Fred, a 160 lb cyclist, rides a 21 lb steel Behemoth. He goes on a hard solo 40 mile ride with 500 ft of total elevation increase. He finishes in 2 hrs 13 minutes 20 seconds. He wants to go faster so he becomes a weight weenie and spends $3000 on a new 17 lb Wonderbike. He rides the same 40 mile course generating the same amount of power. Approximately how much does Bob's time improve?

A. 14 minutes B. 11 minutes C. 8 minutes D. 4 minutes E. 2 minutes F. 1 minute G. 15 seconds

2. There is an adage "a gram removed from the periphery of the wheels is worth 2 grams removed from the rest of the bike." Select all of the riding conditions below where the adage is true:

A. Climbing a steep hill B. Riding at constant speed in a paceline C. Accelerating in a sprint D. Having your weight weenie friend lift up your bike to show off the light weight
re: Weight Weenie pop quizwspokes
Dec 10, 2003 8:16 AM
1. Fred just needs to ride more and in a hillier area...that way after several thousand feet of climbing in 40 miles he doesn't care anymore about anything but eating when done. That way he can invest the 3 grand in a hot tub.

2. When Fred isn't looking, I will drop a couple paper clips in his seat bag, sshhhh, that will add 1-2 grams per clip...hehe...
racing?DougSloan
Dec 10, 2003 8:17 AM
Is this ride a "race"? If so, even if the time is 15 seconds, that could matter. Also, a 40 mile ride around here could easily have 3,000 feet of climbing or more. The steepness of the grade matters, too. If Fred makes a bit less power than his riding buddies, too, even 15 seconds could make the difference between getting dropped or not.

As to question 2, it's very rare that you ride at a constant speed, whether up a steep hill or in a paceline. Riding is a near constant series of accellerations, and each time you do, heavier wheels or an entire bike require more energy.

Now, people can get *too* hung up on light weight, but don't dismiss weight as irrelevant. Under some circumstances, it's not only relevant, but critical. *If* speed matters to you, which may be a big "if", then a lighter bike is beneficial.

Doug
Agree & disagree on wheel weightsbimini
Dec 10, 2003 9:00 AM
I've been in a couple of flat road races where the field did not get broken up and accordian effect was in full swing. Sprint / brake, Sprint / brake these swings were never ending and at every little rise the field would speed up in an attempt to break it up but the the peleton always reformed. Made for some wild crashes. The ambulance drivers stayed busy. It took a lot of energy adapting to all the swings. I hate to guess how much energy I bled out throught he brakes.

In those races super light wheels would of helped over aero since the peleton was so massive that air was all moving with you. A big percentage of the energy was spent accelerating the wheels and bike just to turn around and bleed it out again on through the brakes.

I've also been in hilly races where the field broke up right away and the speeds (or at least effort) were fairly consistant. Being a heavy ride I get dropped at times going up the hill and then have to catch back up again on the down hill or the flat after the hill. My heavy aero wheels help me on these races since I spend a bit of time riding alone playing catchup.

I know this is opposite of the general rule of thumb on which wheel to use where.
of courseDougSloan
Dec 10, 2003 9:56 AM
Light *and* aero and you are prepared for anything. Someone like a Zipp 303 or 404 tubular has no compromise.

Doug
Don't the 404 rims weigh 100 gr more than those in the 303?...TFerguson
Dec 10, 2003 2:46 PM
There's always a compromise.
TF
yes, but 404 still very light-1283g total wheels, 365g rims nmDougSloan
Dec 10, 2003 2:52 PM
Do I go heavy (404) or do I go light ( 303)? nmTFerguson
Dec 10, 2003 3:19 PM
depends on the motorDougSloan
Dec 10, 2003 3:30 PM
If you intend to lead (or do time trials), go 404; if you have trouble hanging with the group, go 303.

Either way, you really can't go wrong. The 404 wheelset and rim is still much lighter than a standard aluminum rim wheelset.

Doug
Both out of my league...TFerguson
Dec 10, 2003 5:05 PM
I would be choosing between my OPs and Deep-Vs.
TF
easycyclopathic
Dec 10, 2003 8:27 AM
#1 G (in reality he'd save less then 15sec)
#2 C.. no wait, def D! it is a Master Card moment
More like a Monty Python and the Holy Grail moment! nmCritLover
Dec 10, 2003 9:23 AM
Always Look On the Bright Side Of Life nmcyclopathic
Dec 10, 2003 10:49 AM
re: Weight Weenie pop quizThe Human G-Nome
Dec 10, 2003 9:07 AM
1. How heavy is your bike and what is the lightest bike you've ridden. Also, although the answer is G, I'll spend a couple hundreds bucks for G in a race every time. 15 seconds could be the difference between the podium and 25th place.

2. My wheels aren't silly light, but on steeper climbs and anywhere when you need to accelerate from a slower speed, they'll make a difference. In a sprint? No. In a paceline? Of course not. But if you're trudging up an 8-12% climb with 2500 feet, you'll feel the difference. And in my world, that's at least once or twice a week even in the off season.
re: Weight Weenie pop quizngl
Dec 10, 2003 9:43 AM
1. Closest to F for me.
2. Order of A,C,D,B.

Your post seems very argumentative, and, you have already made up your mind to your answer. I can't ever change your mind, and, unfortunately I don't think you will be able to change mine. The reason; I don't have any faith in these FILL-IN-THE-BLANK formulas on the WEB because I can't see the how the formula was derived, and, it does not acount for real world conditions ( wind gusts, accellerations, hills etc.). As I said in an earlier post... strap on an extra 2 pounds to your bike and ride the same loop, or, climb that same hill. You will have your answer. As the earlier poster said, there is a whole lot of pleasure to be had when you don't get dropped from that lead group.
re: Weight Weenie pop quizasgelle
Dec 10, 2003 12:41 PM
"Your post seems very argumentative, and, you have already made up your mind to your answer."

Unlike most questions here, these are not matters of opinion where you can make up your mind. Go to analyticcycling.com or another power model, plug in the numbers and calculate the answer.

"I don't have any faith in these FILL-IN-THE-BLANK formulas on the WEB because I can't see the how the formula was derived, and, it does not acount for real world conditions ( wind gusts, accellerations, hills etc.)."

Have you been to analyticcycling.com? They do show the derivation of their model; and though I'm not sure they refer to the article, the model has been validated in the peer-reviewed literature. So they present the physical basis for the model, the mathematical derivation of the equations used, and comparison of the model results to data. What more would it take to convince you?

As for real world conditions, the models at analyticcycling do include all the factors you mention (and more).
God did not write analyticcycling.com (rant, of sort)...TFerguson
Dec 10, 2003 3:16 PM
If read analyticcycling.com as proof positive one more time, I'm going to puke. It is a model. All models make assumptions. Just because the power equation says so, does not make it so.

I'm not trying to put down the work done to provide the site. As a chemical engineer my education was almost totally mathematical modeling. It is a valuable tool; but it just that - a tool. A much better tool than any anecdotal evidence will ever provide, but still just a tool.

Again, I'm not arguing against your conclusions, only against your insistence that if the math model says so, it is so. Sorry to argue with you when you are the only one providing any real data. I guess I'm just too accustomed to the "strap 2 lbs on and ride it again" crap, that I just ignore it. I can't ignore what I perceive as the misuse of real modeling.

TF
I'm a Chem E geek tooContinental
Dec 10, 2003 3:51 PM
And agree with you on the modeling. My point is that the time savngs is about 15 seconds for 4 lbs, not several minutes like many think. Also, the variation in human performance is so large that it would take many replications to prove an actual difference.

Just curious, since you understand some physics, what's 100 grams off the bike worth to you? For me it's worthless.
As long as I’m sitting here a good 30# overweight...TFerguson
Dec 10, 2003 6:33 PM
eating Tostidos and Salsa while typing, anything lighter than your Behemoth is totally for my ego. Unfortunately, my ego has Champaign tastes on a beer budget.

Personally I believe that racing is something on the order of:
45% fitness
25% knowledge/experience
25% mental
5% equipment

Recreational riding would probably knock the knowledge/experience down some and add it to fitness.

That equipment section takes in the whole range from Lances latest trick Trek to the mom's 28 lb comfort bike. As you can see, in my model, a 100 gram lighter wheel doesn't mean squat.

TF
God did not write analyticcycling.com (rant, of sort)...asgelle
Dec 10, 2003 5:39 PM
TFerguson wrote: "I can't ignore what I perceive as the misuse of real modeling."

Could you explain this? I don't see how analyticcycling.com is a misuse of "real modeling." They derive an equation of motion based on first principles, apply force models which have been validated numerous times, develop a comprehensive model and validate it against emprical data which shows that the model is accurate to a within a few percent (2-5%, if I remember correctly).

If you're refering to this application. I don't see the problem either. The model is run for two representative cases to assess the difference between them. The calculation shows the difference to be 15 seconds over the course of an hour riding. Based on this, people are left to decide if the time savings are worth the expense. No one has said the time difference is exactly 15 seconds, but the conclusion that the change will be more than a few seconds and less than a minute is pretty secure. I think this level of accuracy is more than enough to base a decision on whether or not the wheels are worth the expense.

If anyone has data to contradict analyticcycling results I would love to see them, but so far all the data I've seen confirms analyticcyling.
You missed the point entirely...TFerguson
Dec 10, 2003 6:17 PM
You missed the point entirely...

I am NOT accusing the site of anything. They have done an excellent job of modeling and I would believe that they are aware of its limitations.

It's those who misuse the models and quote the site as if it were tablets from the mount that I can't abide. It is a model. Models make assumptions. These assumptions may or may not be correct in this real world situation. When you apply the model (something the author has no control over), you are making these same assumptions plus your own. They may or may not be correct in this situation. This has nothing to do with the validity of the math.

Again, I want to emphasize that you are to be commended for actually presenting evidence to validate your side of the discussion. Most do not get past voodoo. It's just that this is not proof positive.

TF
You missed the point entirely...asgelle
Dec 10, 2003 6:38 PM
Sorry, I misunderstood who you were refering to. I completely agree that the model is a tool and like any other tool can be used well or poorly. I also agree that the model does not provide proof. The model provides data and from data conclusions can be drawn.
God did not write analyticcycling.com (rant, of sort)...ngl
Dec 10, 2003 6:38 PM
I have never read ( nor wanted to read) how this model was derived. I was always amazed at how conservative the numbers seem to be.
When people talk about the differences in wheels ( weights vs aero dynamics etc.) and then you plug in the numbers there seems to be minimal difference. I DO NOT HAVE THE ANSWERS, IN FACT, I AM LEFT WITH MORE QUESTIONS. Based on this model I don't see why LA and the boys use climbing bikes, ADA wheels, light components, etc.

As I said in previous posts ( somewhere) I see a small but measurable difference since I lightened up my rotational weight. IT HAS MADE THE DIFFERENCE OF ME BEING DROPPED FROM THE GROUP VS JUST HANGING ON DURING EACH OF THOSE 4 MINUTE CLIMBS. I HAVE EQUATED THIS TO BE A SAVING OF ABOUT 10 SECONDS OR SO. THIS IS A HUGE DIFFERENCE TO SO OF US. This has made me very happy and it did not cost many $.

Sorry to offend those who disagree.
Not offendedasgelle
Dec 10, 2003 7:20 PM
Not even sure that I disagree. Don't take this wrong, I'm not saying you don't see noticable improvements with the lighter wheels. However, since you changed to the wheels expecting an improvement, it's also possible the difference you see could be from psychological factors (improved motivation, etc). In my opinion, that's the reason you see pro's using the lightweight stuff (also what's an insignificant change to us,1-2%, could be a huge change for them).

You might be surprised how little many pro's know about bike mechanics and especially physics. After all, they're pro's because of their physical, not mental abilities (this was not meant to belittle them, it's like saying baseball pitchers are not chosen based on their batting averages).
Not offendedngl
Dec 11, 2003 4:44 AM
I absolutley agree with you.
My answers and commentsContinental
Dec 10, 2003 12:41 PM
1. G 15 seconds, but Cyclopathic is correct, 15 seconds is a high estimate which gives every possible beneifit to the lower weight including high estimates of increased friction, no recovery of potential energy while decelerating, and no reduction in wind resistance at the slower climbing speeds. There is no way to apply the laws of physics and get a time savings of more than 15 seconds. And remember, this is for a 4 lb weight reduction.

2. C. Accelerating in a sprint. If the wheels are not being accelerated, wheel weight has no more effect on pedal power required than frame weight or rider weight. Light wheels make acceleration and braking very slightly easier and steering slightly quicker. The only way to loose energy from heavier wheels is to apply the brakes as Bimini alludes to. Otherwise, all the extra energy put into the wheels while accelerating is recovered during deceleration.

What's my point? Unless you're racing, cutting a couple of lbs, let alone a few hundred grams, has no significant affect on riding performance. Most riders greatly overestimate the performance gains from lighter bikes and wheels. Why would anyone use lightweight stem, bars, and fork on an every day bike? This is certainly fueled by marketing hype. So the roads are filled with bikers casually tooling along on bikes that have comprised durability, cost, stability, and safety for the sake of style.
Not Enough Informationasgelle
Dec 10, 2003 12:49 PM
Continental:

You don't provide enough information to answer part 1. Over what distance does the 500 ft elevation gain take place. the answer will be different if 500 ft is gained in 1/2 mile and lost over 39.5 miles or vice-versa.
Not Enough InformationContinental
Dec 10, 2003 1:29 PM
You're right, there's not enough information to determine an exact answer, but worst case assumptions show that even 15 seconds is a high estimate.
re: Weight Weenie pop quizFTF
Dec 10, 2003 2:19 PM
There is a fred, in the begining but BOB, is the one you ask about, So what kind of bike does bob ride? More info is need on this bob, that is for sure, to find out time increases. Oh oh yes and don't for get "every second counts" :)
Bob is a Fred until he buys a $3000 bike, then he's a poser nmContinental
Dec 10, 2003 2:34 PM
Bob is a Fred until he buys a $3000 bike, then he's a poser nmngl
Dec 10, 2003 5:02 PM
I agree with you TFerguson. I will not slam the model, but...
Continental, I read your earlier postings elsewhere and that is why I felt/knew we will never agree. I have plugged many numbers in that model, and, I have strapped 2 pounds onto my bike and recorded the difference. For me, two pounds is the difference between hanging on or getting dropped on climbs or being able to stay with the sprinters.

I will not belittle you at all for your thoughts and feelings about riding a 21 pound bike, but, I still don't understand why you have a clear problem with others with their beliefs???

I love my $2500 OCLV and there is a lot more to it than just the weight.

Happy riding.
Agree with that last statementasgelle
Dec 10, 2003 5:50 PM
Not that I love your OCLV, but that there's a lot more to buying decisions than weight (or performance). I don't think I've made myself clear. I believe it is possible to quantify the difference in performance between various pieces of equipment and have cited many examples from analyticcycling.com to back up these conclusions. I also believe claims that a piece of equipment improves performance should be verifiable either through model or empirical data.

However, I do not believe and have never said that performance should be the only criterion on which to base buying decisions. I believe there are many personal factors which go into the choice and I would never challenge anyone's personal decision.
I have no problem with light expensive bikesContinental
Dec 10, 2003 6:37 PM
If they are well-informed purchases. I have a problem with the marketing of bikes, which over-emphasizes weight, especially for non-competitive riding. Unfortunately, many uninformed recreational riders who will never compete and never utilize a few seconds advantage fall for the hype and end up riding bikes and wheels designed for racing, when they could have a more durable and reliable bike.

I can understand how you can love a bike for the beauty of it and the lightness can be part of the beauty for you. For me, ruggedness, comfort, and durability are part of the beauty, and I guess I'm an old fart lamenting the decline of elegant, beautiful bikes built for long term rugged use. I guess I can always go to Rivendell but that makes me wonder why I can't find a bike like that at any LBS in a Metropolitan area of 2 million people, but I could buy a Lightspeed, Merlin, Serotta, or Trek OCLV racing bike tomorrow.
Careful now...TFerguson
Dec 10, 2003 7:12 PM
Rivs aren't cheap and tourists can be at least as elitist as racers. They're just less vocal and less colorful. And, to get my 2 cents in here, I think you would be hard pressed to find a road frame that will last as long or take as much abuse as a Litespeed Blue Ridge.

TF
re: Weight Weenie pop quizDutchy
Dec 10, 2003 6:26 PM
Their figures are wrong. Let me prove it.
I have a hill near my house that is 6.2% for 1.6km. On my old Giant CFR1 that weighs 10kg and has Shimano R535, wheels I can do this climb in 5min 20s (maximum effort). The same climb on a Giant TCR1 with much lighter wheels, Krysiums SSC SL's I can do it in 4min 45secs (maximum effort). A difference of 35 seconds, according to www.analyticcycling.com the difference should be 58seconds. So the numbers are just a guide. Either way the difference is 35 seconds for one very short hill, over 60km the difference is measured in minutes. If you don't have a light bike fine, but don't tell people that a heavy bike is almost as fast, they aren't!

CHEERS.
Mark
Preposterous results, erroneous conclusionContinental
Dec 11, 2003 6:14 AM
You've obviously made a huge error in using the analytical cycling model. You're estimating about a 20% increase in velocity from a 3-4% reduction in total weight. This physically impossible result will not be predicted if the models are used properly.

You're also claiming more than a 10% increase in your test velocity and concluding that light bikes are that much faster. Again, basic laws of physics don't allow a 10% increase in velocity from a 3-4% reduction in total weight, even on a steep, slow climb. Mechanical, physiological, psychological, and environmental factors all contribute to the difference in performace.

Your unscientific and invalid analysis is the type of misinformation that perpetuates the myth that slightly lighter bikes have huge performance andvantages. The bike marketers love you though--they can sell high priced bikes with short design lifes.