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Bike Weight vs. Body Weight(11 posts)

Bike Weight vs. Body WeightSolky
Sep 6, 2003 1:46 PM
When discussing with a friend the desire to lighten my 20lbs (with everything but waterbottles) Cannondale R4000 roadbike by purchasing lighter wheels, seat post, pedals, stem, etc., he countered that it would be much cheaper just to lose 3 lbs of body weight.

My friend is a mechanical engineer, so he understands the dynamics of weight, momentum, acceleration. Is he correct that the combined body weight plus bike weight is all that matters? Perhaps, when a rider gets out of the saddle, the bike weight becomes more important with the change in center of gravity? If not, why do riders pay thousands more for for lighter bikes?
re: Bike Weight vs. Body Weightcollinsc
Sep 6, 2003 2:55 PM
yeah, sure hes right, but hes a jackass too.

I would like to make clear to anyone who uses the "cheaper to lose 3lbs of body weight" that not everyone HAS 3lbs to lose. Some of the weight weenies out there are flyweights to begin with, and kidney surgery is NOT cheaper than a lighter bike. Fat @ssholes....

Anyway, yeah, hes right, but that doesnt mean you wont feel a big difference with a lighter bike. Its just easier to throw around less weight. Not going to make you any faster.
Do it all.roadeeforlife
Sep 6, 2003 3:29 PM
I am a weight geek. I own a 14lb 4oz Ghisallo and every once in a while I get a guy in the club that says "its cheaper to loose a couple of pounds". He most likely says this because I have a nicer ride them him or he is tired of me dropping him on every hill. Well, I can counter his snide remark by saying I lost 15lbs within the last two months.
Loosing a few pounds off the body and keeping it off is harder than people imagine, this is why america is overweight. My suggestion is to do them both at the same time.
Loose some weight on you and the bike. It will make you feel faster and better about your self. Start with the wheels then the small stuff. Good Luck to you!!
Bike & Rider is all that matters...C-40
Sep 6, 2003 3:50 PM
I'm another mechanical engineer and I can assure you that it's the combination of bike and rider that is relevant to any potential increase in speed.

Here's an example. Suppose you're a 180 pounder with a 20 pound bike. With a total weight of 200 poinds, reducing the bike weight by 2 pounds will increase speed (or reduce power requirements) by 1% and only during uphill efforts. It will have no effect on a flat road and will actually cause a loss of speed on a steep descent.
Bike & Rider is all that matters...kai-ming
Sep 6, 2003 5:44 PM
I am another mechanical engineer too. Reduce bike/body weight will mean reduce momentum, not just increase speed only during uphill, but make acceleration faster and braking more effective. Reduce weight of wheels will be even better since it is rotational weight,i.e. moment of inertia.
R4000 at 20pounds?Zman
Sep 6, 2003 4:33 PM
Why does your R4000 weigh 20 pounds? My 2001 R2000 only weights 18#3oz at size 60.

I think your scale is off. I own a Jekyll 3000 mountainbike that weighs only 25# 13 oz. Your bike is lighter than 20 pounds.

I also believe that a lighter bike will help you. I also am an engineer by schooling and know the dynamics. This does not take into consideration things like confidence, enjoyment, love, and all that goody goody stuff.

You will be faster on a lighter bike, all things considered. Hey, who wants to lose weight anyway?

Long live beer..........

R4000 at 20pounds?Solky
Sep 7, 2003 5:02 AM
My R4000 is a '99, but you are correct that my weighing methods are probably not exact.

That said, I think the weight culprits are the CXP30 wheels and the Look 286 pedals (plus I have a bike pump). From the advice provided, upgrading the wheels would seem to be the priority.

Thanks to everyone for all the input!
Equating bike weight and body weight...Dwayne Barry
Sep 7, 2003 1:38 PM
probably isn't justified. Afterall, losing the weight from your body has beneficial physiological consequenses that losing bike weight does not. For example, less body mass would lower the load on the cardiovascular system, will help you handle the heat better, etc.
Equating bike weight and body weight...koala
Sep 7, 2003 4:52 PM
Well thought out. I have always thought the same thing. Ride more, lose weight that is fat, increase your power to weight ratio. You cant do that by reducing bike weight alone.
re: Bike Weight vs. Body Weighteclipse1
Sep 7, 2003 1:49 PM
did your friend take into account frontal surface area, also weight (mass) on the pedals. it would be like having 50 pounds on a backpack vs. 50 pounds in a saddle bags. less weight does get up to speed /acelerate faster, but also has less inertia. but go with lighter stiffer wheels.
He's more-or-less right.djg
Sep 7, 2003 5:34 PM
You get some extra benefits reducing rotating weight (rims, tires, pedals) and folks argue about the precise magnitude of this benefit. Let's say, optimistically, that saving a half pound off the wheels is worth a full pound elsewhere and that saving a quarter pound off the pedals is worth a half pound elsewhere. Make your adjustments and add it up--your suggested 3 lbs of equipment changes MIGHT be worth 4 lbs total, but otherwise a pound's a pound. OTOH, losing weight off the body may be accompanied by improved fitness, whereas spending money ... OTOH, light bikes are fun and there's worse things to blow money on.