johnnygofaster

QUALIFIERS: I understand the weight-centric just like bikes a lot and it's another thing to talk about. And we're lucky to not have to spend our time looking for food and shelter so we can ruminate about how much this or that part weighs. Thus the following are comments on the culture and marketing more than any particular individual. It's a point of dicussion rather than critique.

That said, it just occured to me to find out my weight in grams.
165lbs = 74,843 grams (me)
17lbs = 8618 grams (bike)
TOTAL = 83461

I guess I just never placed it in context like that before. When you start looking at pieces/parts as percentage of total weight, it gets more surprising...

20 gram stem difference: .02% of total weight
500 gram wheel difference: .6% of total weight (ignoring, of course, the physics of rotating mass, etc.)
2 pound frame weight difference: 1.1% of total weight.

CONCLUSION: Marketing is shewd. Who would pay gobs more for carbon fiber if the weight difference was compared to total bike/rider weight? Of course this doesn't consider the "feel" or intangibles like increased confidence, durability, cache, etc. but that isn't how they're often presented anyway.

All that said, I like lifting my "light" 19lb. bike over my 24lb. steel one. Makes me feel faster although it's only a 3% weight .

I have nothing to do this morning. I'm sure you can tell. If you're reading this drivel I guess you don't either.

SDRider

See my steel bike is just over 19lbs with pedals and cages. My lightweight bike is just under 17lbs but I find myself riding the steel bike most of the time.

Dead Extra #2

A one dollar bill weighs .9866 grams (https://www.frbservices.org/Cash/CashQ-A.html#7).

If you spend $2000 on carbon fiber parts, you lighten your wallet by 1973.2 grams. That's a 2.36% reduction in weight. Starting to sound more effective already isn't it? That's not even counting the weight saved by the parts!

oboeguy

3% is non-trivial, IMO. Regardless of one's thoughts on that, how is anybody surprised? The heaviest part of the bike is always the rider!

barba

I'm considering having my bones replaced with titanium.

Weight seems a real issue for racing. 3% is non-trivial if it gains you a minute over the course and you are racing. I don't care if I beat anyone, and I am increasingly trying to measure my success in sustained effort rather than average speed (I did 20 long miles with lots of climbing last weekend that was a vastly slower but a much better workout than my high speed 35 mile loop). Average speed just seems fickle. Getting back to my driveway a minute or two earlier isn't really my primary concern, so I save the money for other things (like other bikes).

jschen

Okay, you made me click on the thread with the thread title. So tell me, exactly how much does your butt weigh? In grams.

jrennie

In a straight line analysis your number are very true but when factoring in resistance and physics, your argument(topic for debate/discussion) dosen't hold true.
170lb rider +15lb bike=185 total weight
160lb rider +25lb bike=185 total weight Looking at total numbers the two should be equal and require the same force to move, but thats not the case.

fmw

Why is that not the case?

Nims

That is not necessarily the case, but it could be. If the bike weight change was solely in non-rotating assemblies, then yes, it would require the same force to move. Although that never happens.

Maxxer

hahaha... that was a good one, made me laugh hard.

But a carbon fiber dick would be stiffer I suggest.

j-dowsett

Obviously however, if someone puts out say 4W/Kg, then an 80Kg rider on a 10Kg bike will be faster than a 70Kg rider on a 20Kg bike.

Nims

Considering the average density for compact bone is 1900mg/cm^3 and the average density for a titanium alloy is about 4700mg/cm^3, you'd be adding 2.8 grams per cc of bone! Way to go!

j-dowsett

Making the next new frame material - bone!

Nims

Assuming a 55cm tuscany in Ti weighs 1265g (2.783lb ), a 55cm tuscany in bone would weigh 511g (1.125lb)

I see the future of cycling.

WhiteRabbit

But what is the specific strength of bone vs. Ti? That is the important question. ;D

Enthalpic

+1 The difference between 1st and 2nd is usually far less than 1%

AlanS

The TDF is about 80 hrs in the saddle.

80 hrs = 288000 sec

In the pro peloton, a difference of 30 sec would be considered significant.

30 sec / 288000 sec = 0.01 %

Thus, if you are a pro rider, you might worry about performance issues down to one hundredth of one percent. In that context, 3% is significant.

Edit: I'd like to know J-Lo's butt mass in grams.

nesdog

Of course, I'll be replacing my butt bone with a Brooks. Weighs more but it's comfy.

Sheldon

rruff

Rotating parts only affect the rate of acceleration... not the steady state speed. It is a trivial effect.

helmets save

Rotational Mass issue!!! We can just leave it at that. As everybody here says and knows, the biggest improvement is found in upgrading the wheels.

As you said, it is found in acceleration, but arnt we alwasy accelerating the bike. There is no one who can keep the bike at a constant speed wiht the same effort when you factor in the terrain.

rruff

True... but a weight difference only effects *climbing* significantly, and it would be less than the amount of weight change. Even then, drafting on a climb would get you more than that 1%... so you'd still be able to hang with somebody who has a slightly higher power/weight ratio.

Nims

I didn't say a word about steady state speed. The comment was regarding the force to "move" the bike. Meaning a change in speed... a.k.a. acceleration.

WhiteRabbit

Even on perfectly flat ground with no wind, no one has a perfectly smooth cadence, so you are always accelerating every time the crank goes around.

asmallsol

No, make sure your compeditor is using a bone frame and carry a bottle full of Coca Cola. Spray that on his frame and by the finish, his bike will be like rubber.

brianallan

consider two riders weighing 165lbs, one has 10% body fat, the other 20%