Bicycle Mechanics - wheels vs. frame weight

I saw someones thread state 1 ouce off your wheels is equal to 3 off the frame. Is that true or does it just roll off the licker nice.

It's actually quite true........but for dramatic results, a pound off your gut is equal to a pound off your bike...

Thx, time for wheels and no more doughnuts.

One scalpal, one physician, one nose, one skin cancer, and if we don't get rain soon I'm goin' to Seattle

It's actually quite true........but for dramatic results, a pound off your gut is equal to a pound off your bike...

The wheel vs frame weight ratio is pretty close. The body weight vs frame weight is off by quite a bit. It's more like 6lbs off your gut is equal to 1lb off the bike. There is a reason why a road bike that's 2lbs lighter feels so much different, yet when you lose 2lbs you can't hardly feel it on the bike (not like you can when you drop 10-20-30lbs). Although improving the engine will always make the bike ride better!

Andrew

Originally posted by Ajay213
The wheel vs frame weight ratio is pretty close. The body weight vs frame weight is off by quite a bit. It's more like 6lbs off your gut is equal to 1lb off the bike. There is a reason why a road bike that's 2lbs lighter feels so much different, yet when you lose 2lbs you can't hardly feel it on the bike (not like you can when you drop 10-20-30lbs). Although improving the engine will always make the bike ride better!

Andrew

Can you explain?

I read it from a very knowledgable person from an article on some website. And I'd be hard pressed to explain the physics behind it (as opposed to wheel weight vs frame weight). But it does make sense from my experience, as mentioned. When I ride a 18lb road bike I can easily tell the difference between it and a 25lb road bike, and the difference is BIG in just the way the bikes accelerate. Yet I've lost some 20lbs since I've started riding quite a bit, and I notice a difference, but nowhere near that extreme level.

You can do the same thing, ride with a camelback full of water, then ride a bike some 7-8lbs lighter, which feels different? On the same hand it's not unusual for a person's weight to vary 2-3-4-5lbs during the course of a week, do you ever notice that difference? A person's body weight can even change 1-2lbs during the day, do you notice a difference between a morning ride and an evening ride in that regards?

But in either case, as I said, upgrading the engine is always the most important piece of the puzzle. Besides, by losing weight you'll probably save money (Mc Donalds is getting expensive!), therefore you can pick up all the Ti bolts ya want ;)

Andrew

One of the things with losing bodyweight is that it tends to happen gradually - so you don't really notice the day to day changes, it's only when you look back a month at a time.

With bike weight vs. fat-ass weight - I would think that losing 2 lbs from either would probably make the same time difference, but losing 2 lbs from the bike - i.e. 10% of the total weigth - would make the handling feel much more chuckable, something I wouldn't notice taking 2 lbs off my 190lb fat-ass.

Team

Hi,

You all seem to be giving relations, but the most important factor to consider is the design, the bike's geometry and behavior, that will make a real change, that will make a responsive bicycle, while weight is only an obsession for competition and may be helps a bit in mountains, but who cares, really, I mean just for training? I would even say a heavier bike in mountains will result in a better training.

There is real physics involved here but please don't ask me for the formulae. The rolling stock, i.e. the wheels move more than the rest of the bike so keeping their weight low is going to give you reduced inertia (if there are any engineers out ther please don't kill me!). The farther you get from the axle the more the wheel moves so following that line of thinking it is the rims and tires that are really where you want to reduce, the hubs and spokes less so. Get yourself the lightlest tires and rims and don't worry so much about a gram or two in the frame or saddle. Remeber also that about 75% of the energy you put out gets eaten by wind resistance so think about aero rims and spokes while you're at it.

Originally posted by George
It's actually quite true........but for dramatic results, a pound off your gut is equal to a pound off your bike...

How does that work?

If I have a 16 pound road bike, and lose 20 pounds, did my ass eat my bike?

nah, I would wager every 20 pounds on your body is similar to MAYBE 1 pound on a bike.

I weigh 150 wet, and I can feel the difference between a 24 pound bike and a 29 pound bike (although I did get faster the heavier my bike got....). If I lose 10 pounds, I am not going to notice anything. But I get on my buddies 18 pound single speed, and I can flat out move.

Weight on body is relative to the weight of the bike. I can lose all the weight I want, and I'd be faster by dropping a pound off my bike.

Originally posted by George
It's actually quite true........but for dramatic results, a pound off your gut is equal to a pound off your bike...
What if you don't have a gut?? ..Then you might be cutting muscle to lose that lb.

The wheels baby ...it's all about the wheels!! ...definitely!

Here in the UK, a pound from the bike is (at least) 500 from the wallet ;)

That's the good old catch-22.
The order of magnitude for weight changes;
Wheels/rotational mass
Bike
Body

The order of affordability to change those things
Body
Bike
Wheels/rotational mass

Andrew

Big tires definetily change the way a bike handles... I tried putting my friend's 2.7s on my XC bike which had 2.1s (and was radial), and the difference was astounding.

The distance from the axis of rotation (fulcrum) is multiplied against the force to get the torque on the wheel, which is what you feel when u deal with inertia of the tires. So multiply 13" against the force of moving your tire.. adding an ounce to your tires would feel 13 times heavier than adding an ounce to your hub (presuming u added it at 1" from the axle)!

Then just consider that the inertia of the spinning wheel is what provides the gyroscopic effects (makes the bike balance really easy), and think about the rapid change in stability based upon speed (my freeride bike almost instantly becomes hands-free stable past 4mph or so, whereas my roadie slowly increases its gyroscopic balance). Also think about (considering the head tube axis as the fulcrum) the torque in turning the fork.

physics is cool