Lebowski

just curious.

is there a difference between a 150 pound rider and a 20 pound bike

vs

a 145 pound rider and a 25 pound bike

either way its 170 pounds of weight on a bike.

SweetLou

Yes there is. Different bike material can handle different amounts of weight. Different Rims can handle different amounts of weight. Since I will assume that part of the bike weight you mention includes the rims, that can change, though very little.

But, if you are only talking about how much weight can a particular rim carry, then there is no difference where the weight is.

AEO

downhill, no.
price of bike, yes.

Black Bud

The difference with modern bike materials and construction is less in the capability of the bike to handle the weight without suffering structural failure of frame and/or components than the way the weight is distributed and how "stable" it is. For instance, mounted cargo bags and equipment are more stable than a moving rider whose center of gravity is always changing.

A heavier bike is also more "dead weight" that has to be moved, especially from a standing start; the heavier rider has more leverage to push from a standing start (their weight is a stronger "throttle").

A heavier rider is at no disadvantage on the flat, but suffers going uphill;the thinner rider has an advantage going uphill, especially if the bike is lighter (power/weight ratio here).

A heavier bike can survive "abuse" (such as off-road downhill racing and pavement that resembles more rocky doubletrack than blacktop!) than a lighter one due to materials and construction used. As I have seen in a post here, the heavier rider may well also survive "abuse" better if they crash! (More 'padding'.)

All in all, it's the circumstances in which the rider finds themselves which determines when a bike is "too heavy" or not, even if the gross weight of both bike and rider are the same.

SweetLou

I agree with you except for the part in bold. If two bikes are of equal strength, then they can handle the same amount of weight. You're contradicting yourself here. Unless you are not talking about the weight on the bikes, but of the material used. For example, steel has a longer fatigue life than aluminum. So the aluminum will fail before the steel.

Black Bud

In actual practice, the fatigue life of modern bike materials (if they are properly manufactured to begin with), while it indeed does vary, is irrelevant. Most people will end up throwing the bike away as its having become "obsolete" long before the frame fails.

The components fitted to the frame? Fatigue life is rarely that important since it's presumed that any and all components have a very limited life to begin with. Therefore, fatigue life is NOT worth worrying about since these items are going to be replaced from wear, tear and even technical obsolescence long before the materials fatigue and catastrophically fail (break or fall apart).

chipcom 

The difference is, one bike weighs less than the other, one rider weighs less than the other. Any other comparisons are pure speculation based on hundreds of variables.

c0urt

someone also stated the big important variable.
where the weight is
rotating mass makes a huge difference when turning, accelerating, and slowing down. unfortunately there are lots of variables when it comes to bicycles, and weights. and five pounds is a lot of weight in bike terms. Technically 1 pound is.

Tom Stormcrowe

Kind of off topic, but funny still. All bikes weigh the same, 35 pounds
20 pound bike, 15 pound lock to keep it from getting stolen.

XMart bike, 35 pound frame and no lock, because no one wants it.

AEO

I'll take it...
j/k

I left a 35lbs xmart bike outside that didn't work one day with no lock... it was gone within 2hrs.

DieselDan

At the weights you gave, the heavier rider on the lighter bike would probably have the advantage of more lean muscle, assuming both riders are cyclists on road bikes, not bike riders on toy bikes.

Lebowski

well what i was kinda trying to get at (but must have failed) was dealing with people who are obsessed with making bikes lighter. sorry if some of the stuff went over my head i barely passed my introductory physical science class (physics for tards) and i took botany classes for the next three years for my highschool science credits

so my rephrased question is as follows:

what would the difference be if you shaved a pound off the bike or the rider lost a pound? either way the total weight is decreased. if lighter=better performance .... f*** it i have no idea how to phrase what im thinking

huerro

At a certain point losing weight from the rider means losing the muscle that makes the bike go. Personally I don't know what that point looks like, but then again I ride steel tanks.

Also in my just out of college days I lived for about a year in a 6th floor walk up and rode a cheap Giant MTB. 10lbs less to carry up those stairs would have been a delight.

chinarider

I don't agree with that. The more weight being moved, the more work being performed requiring more energy. If the heavier rider is stronger per pound than the lighter rider, that may make up for the added energy costs. But if you take someone who has 10% body fat & faten him up to 20% without changing his lean muscle, his performance will suffer, whether on hills or flats.

becnal

Less muscle mass to move more bicycle. Imagine the difference is tiny though.

JeanCoutu

I'd prefer to be the heavier rider w/lighter bike.
Easier to pop potholes, better body language, etc.

5lbs isn't really all that much tho.

AlmostTrick

Shouldn't a heavier rider be more able to power a heavier bike? Or power a lighter bike at a higher speed than a smaller person could? This is assuming similar body fat percentages of course. If the extra body weight is mostly fat, then it won't help move the bike. Lightweight riders (like me!) are pumping more bike per pound than most bigger riders are.

StephenH

If the two riders are somehow "equal" in their abilities, the heavier rider with lighter bike should have a clear advantage.

If it's a matter of losing weight from the rider or the bike, it depends partly on if the rider is overweight- if so, that would be the place to start. If nothing else, he/she is likely to get stronger in the process of losing that weight. But no reason you can't do both, either.

It also depends on the point of riding. This sort of assumes you want to go as fast as possible. But hardly anyone uses that reasoning to buy cars, so why on bikes?

stevage

I just replaced a heavy bike with a light one. The light one is much more manoeuvrable (easier to swing from side to side under you, hop up kerbs etc), and of course much easier to pick up and carry. I particularly notice that when it's loaded with a pannier. Picking up a heavy bike with pannier was really tough work. Picking up a light bike with pannier is ok.

Steve

Bill Kapaun

So, how about a 70 lb. rider with a 100 lb. bike?

Indyv8a

what if I got like a thousand butterflies tied to the lighter rider, would they be able to add 1 mph by pulling?

madhouse

We keep going off on the tangent of rider’s capability… I believe the original question could be restated… “Seeing that I have an extra 10 pounds around my midline… If I want to get faster, does it make a difference if I spend my money on Weight Watchers or my bike?”

There is an amazing array of variables that affect the answer but most are minuscule in effect. That being said: the amount of potential energy of two objects at the top of a hill, or the amount of energy needed to move two objects up a hill matters only in the combined total weight.

When you throw energy consumed in rotating mass it changes the equation slightly. Your quickest gain in efficiency will be reducing the weight of rotating mass.

Bottom line; dollar/gram you’re better off loosing 5 pounds.

wobblyoldgeezer

Was it Jacques Anquetil who used to move his water bottle from the frame to his jersey pocket before a climb?
And wasn't he a bit successful as a racer?
And didn't a medical research company just announce that expensive placebos work better than cheap ones?

It's all in yer 'ed