General Cycling Discussion - a bicycle wheel is a flywheel ( a query re the weight of tires)

Bikeforums.net is a forum about nothing but bikes. Our community can help you find information about hard-to-find and localized information like bicycle tours, specialties like where in your area to have your recumbent bike serviced, or what are the best bicycle tires and seats for the activities you use your bike for.

08-02-02, 06:55 AM
My question is in re the weight of bicycle tires; and whether or not the heavier tire has a beneficial flywheel effect.

I am aware that this query, as all others, will instantly evoke the braying, raucous, amused contempt of the smallminded few for which BikeForums is known. I am prepared to weather that in the hope of a reading a thoughtful, knowledgeable responce.

bicycles A and B are identical.

bicycle A has tires of a total weight of 800 grams.

bicycle B has tires fo a total weight of 1800 grams.

It is generally accepted Dr Newton was correct in thinking that an object at rest tends to remain at rest, and an object in motion tends to remain in motion. (see flywheel explanation)

A bicycle tire is a flywheel of sorts. A flywheel is in essence a mechanical battery - simply a mass rotating about an axis. Flywheels store energy mechanically in the form of kinetic energy. see explanation here http://www.upei.ca/~physics/p261/projects/flywheel1/flywheel1.htm

The rider of bicycle B, with heavier tires (flywheels) must exert somewhat more energy to initally overcome inertia.

Once in motion will rider B have to exert the same, or more, energy than rider A to maintain speed?

On the downhill whizzzzz will rider B realize a benefit of the flywheel effect of the heavier tire?

Over the long haul uphill and down will rider B realize a benefit of the flywheel effect of the heavier tire?

08-02-02, 07:02 AM
Originally posted by vlad
.....I am aware that this query, as all others, will instantly evoke the braying, raucous, amused contempt of the smallminded for which bikeforums is known. I am prepared to weather that in the hope of a reading a thoughtful, knowledgeable responce.

AND JUST WHY DO YOU THINK THAT ANYONE WOULD WANT TO RESPOND TO THIS AFTER WE HAVE ALL BEEN CALLED SMALLMINDED????

Greg
08-02-02, 07:08 AM
Did somebody say smallminded?

I would say as simply as possible, there would be less advantage, in every instance, to having a heavier tire.

Riding down the Alps at 75 miles and hour, more stability would be found with bike B but how many people here would find themselves in that situation?

We are only talking grams here though.

08-02-02, 07:16 AM

if the shoe does NOT fit, do not be so quick to take offence

I wrote

quote

I am aware that this query, as all others, will instantly evoke the braying, raucous, amused contempt of the smallminded for which bikeforums is known. I am prepared to weather that in the hope of a reading a thoughtful, knowledgeable responce

unquote

that means that although there are number of those who bray etc ........ there are also the mature, intelligent, thoughtful who would may respond knowledgeably.

I meant to offend ONLY the smallminded who always instantly respond to everything that I post with braying, raucous, amused contempt while they roll wetly on the floor convulsed.

I really MUST take a course in effective writing.

joeprim
08-02-02, 09:48 AM
Good question!

Humm the gyroscopic stability would be greater. Does that mean it would handle slower?

I think there is a net loss of efficiency of any machine with a heaver flywheel. However some flywheel is need for smoothnes and in two wheeled machines for stability.

Neat experiment to attempt to get tires/wheels that are identicle except for weight in maybe 50 gram increments and determine the optimum for different frame styles ...

Sorry but it does sound like fun

Joe
:beer:

usnagent007
08-02-02, 11:59 AM
A flywheel stores energy.

The Law of Conservation of Energy would say that energy into flywheel equals energy out of flywheel.

At no point cycling uphill or down can I imagine any significant benefit in "delegating" a portion of your energy to your wheelsystem. The wheelsystem has frictional losses, while your body could store and utilize that energy more efficiently? (By "delegating" I mean allowing your wheels to store that energy for you ~ energy that is beyond what could be required to move a lighter wheelset)

Does this make sense, or am I just spinning my wheels? *shrugs

poululla
08-02-02, 01:11 PM
Look no further than the Tour De France for your answer. Weight is everything in professional cycling and therefore the lightest tires are used where possible. The flywheel effect is an antiquated principle that has no place in modern cycling. It belongs to the industrial age along with the steam engine and the spinning jenny!:D

DnvrFox
08-02-02, 01:45 PM
http://www.analyticcycling.com/WheelsConcept_Page.html

RacerX
08-02-02, 02:02 PM
Originally posted by vlad

Over the long haul uphill and down will rider B realize a benefit of the flywheel effect of the heavier tire?

Overall, the lighter wheel will always save you energy over a heavier one.
On a flat course, the slightly heavier wheel may be a good bet. They are faster and keep their momentum up. The downside is that deceleractions and accelerations are slower- so it takes more effort to do those.
Yes, the heavier wheel goes faster downhill but in a race it doesn't do too much for you since everyone is drafting. Uphill, well, lighter is better obviously.
If you want to see proof, just look at what the pros ride; On mountain stages, they ride lightweight carbon wheels- like Jaja's deep-dish full carbon sewups which are around 1100grams.
On flatter races, you will see racers use wheels that maintain momentum; like Cosmic Carbone SSC's (about 1700grams) or Campy Boras (about 1700 grams)

and you shouldnt call people small-minded. only small-minded people do that ;)

LittleBigMan
08-03-02, 10:39 AM
Originally posted by Greg
Did somebody say smallminded? We are only talking grams here...
I resemble that remark.

jmlee
08-03-02, 12:18 PM
If trying to make a practical judgment (i.e. should I use a lighter or heavier wheel for this ride), you have to assess the amount gained or loss by the flywheel effect in relation to other gains and losses from added or subtracted weight.

I suspect that flywheel gains and losses would be quite small in comparison to air, rolling, and slope resistances. Hence, in climbing the added weight would slow you down (although we're talking 200 grams out of say 80kgs (bike plus rider). That might make the climb one second slower over a 5 km 5% grade climb. The amount regained in the descent would be even less, because descending takes much less time to accomplish than climbing. Any gains or losses from the flywheel would be a mere fraction of that

Furthermore, as already mentioned, any energy preserved by the flywheel had to be put there by the cyclist in the first place, which means that it would come out equal, minus efficiency losses (3-5% in a well-lubed drivetrain), both as the energy goes in and as it comes back out.

I think the theory is bogus for the later reason alone. Use of heavier wheels has surely to do with their aerodynamic qualities and not with their added weight for their flywheel effect.

Cheers,
Jamie

P.S. Vlad, no matter how I read it, your comment about the small-mindedness comes across as pretty harsh. BikeForums being "known" for having smallminded participants insults the group no matter how you read it. What good does such a comment serve? Did you think that you'd actually provoke a better discussion that way? Hmmmm....

Richard Cranium
08-03-02, 06:06 PM
Yeah flywheels, that's the way to go.....

It would be cool if you could "windup" a 2 kg disc, mounted in a shell near the chainset on the flats. Of course you would need to go to some impossible speed, say 300,000rpm, and then engage it during climbs to assist the crank arms.

I doubt that such a transmission is possible, but in theory the practice would be a boon to many types of locomotion.

The flywheel idea with wheels or tires is flawed in one singular respect.

The additional energy required to add the inertia to the bicycle using heavy wheels isn't any more efficient in nature or timeliness during a given bicycle ride. In practice, the use of a "pumping action" and crank arms in bicycles makes rotational weight and acceleration critical shortcomings to cycling.

There's no such thing as being "up-to-speed", you continue to "pump" even when you think your spinning.......those heavy wheels would wear you out!

Gear ratios, knees, ankles and feet are no substitute for bearings and a camshaft........... too bad... My idea uses the solid idea of storing energy when under light load and returning it when under great load, weather the load be head-wind or a hill......

usnagent007
08-03-02, 10:52 PM
I realize now that the EE course I took is haunting me. Here is what my teacher would likely suggest:

Imagine a closed circuit, with a battery and a capacitor.
You are the battery.
Your wheels are the capacitor.
Accelerating on your bike is like charging the capacitor.
Coasting, allowing your wheels to spend their energy upon the road, is like the discharging of the capacitor.

What benefit is there in having a capacitor in a simple circuit, anyway? What if you just had a battery--if you were able to expend your energy directly to the road (no wheels in the system)?
~less heat, energy losses---> energy is used more efficiently.
but:
~the moment you stop pedaling (open the circuit) the bicycle stops (because no charge is able to be stored).

The other extreme, having a huge capacitor (wheels, very heavy), would mean:
~slower to reach max charge (acceleration sluggish)
~heat, energy losses (losses due to friction and added weight)
but:
~charge could be released, even after failure of the battery (meaning, you could stop pedaling, and let the wheels do the work of moving you)

This suggests that the weight of some wheels might let you coast further...but you are still exchanging work for work.
:sleep: <---if you have read this far

naisme
08-11-02, 01:57 AM
Grams, hmmm, grams, (snort) Uh, what was the question?

Oh yeah, the old fly in the ointment wheel discussion. The thought of the bike being a capacitor and me being the battery, nice. It explains why on a fixed gear bike going up hill one seems to gain momentum, the circut is never closed, it is always being charged, and the energy is not wasted, for there is no way to turn off a fixed gear, as there is no coasting, so it is always epending energy that is put into it. I knew there was some sort of physics involved.

I suppose if heavier tyres would improve a bike more weight would too. Our friend Lance would be a Clydesdale on a Huffy with phat steel rimms and about 100 spokes. Instead he is anally removing the paint off his bike and utalizing one shifter to drop grams.

Lanc also counts every calorie he puts in so he can get energy out. So in the capacitor scenerio Lance is the capacitor on the bike that is also a capacitor, and the food/his diet is actually the battery.

Lemme get back to the grams

chewa
08-12-02, 01:43 AM
Originally posted by Richard Cranium
Yeah flywheels, that's the way to go.....

It would be cool if you could "windup" a 2 kg disc, mounted in a shell near the chainset on the flats. Of course you would need to go to some impossible speed, say 300,000rpm, and then engage it during climbs to assist the crank arms.

I doubt that such a transmission is possible, but in theory the practice would be a boon to many types of locomotion.

The BBC's science shack program did just that, and it did work. They then moved on to air rockets as lightweight sources of extra oomph!

MisterJ
08-12-02, 11:06 AM
Some related seat of the pants observations (boy does that have a different meaning on 2 wheels than 4). Some of you laughed with me when I related backing over my front wheel while driving to work last week. In order to stay on the road until my new front wheel arrives, I pulled the front wheel off of my wife's road bike, adjusted the front brake and went out on the road.

My rims are 20 year old Ukais with 27 x 1 1/4, 80 psi tires. My wife's rims are Rigida's, of a simliar vintage with 27 X 1, 100 psi tires. There was a noticable and measurable difference. My average speed jumped by over 2 mph (much more than the difference in rolling diameter) and the steering is much more responsive, (to the point of becoming twitchy), especially on slow climbs. Acceleration is definitely faster, both on the flats and downhill, (lessened rotational mass is always better folks).

Now the handling changes may be a result of the lessened tire contact patch, but I really think that it is more a gyroscopic thing. If the Rigida's weren't a little light for my 220# frame, I think I would just go ahead and swap her rear wheel too. She likes her hybrid better anyway.

Oh, what the hay, she'll never notice. I'm riding on the Rigidas. It'll feel like a sports car.

08-12-02, 11:28 AM
It'd be hard to do an apples-to-apples comparison, since the different tires will have other differing characteristics (e.g. rolling resistance). Having the same tire on two different wheels is a different kettle of fish.

In going from MA-2's to Open Pro's I noticed a lot more difference than I would have expected. The heavier wheels are slower to spin up, but I actually liked the flywheel effect when bombing along on flat, open road. (But not enough to keep using them, they became my commuter wheels. ;) )

webist
08-12-02, 06:25 PM
How heavy would tires have to get before the fly wheel argument would falter?

naisme
08-18-02, 08:49 AM
Suddenly this has turned into an interesting thread, as I had this tyre discussion with the mech at the LBS. He said there is an argument for having tyres of 700x25 over the tyres I bought, 700x23s for my roadie. I'd been riding 23s on the fixie, and climbed on the roadie, and felt slower couldn't get out of feeling bogged down on the bike. I thought a new set of rubber would do the trick. I slipped the 23s on the old wheel set too, taking off the Rolf Vectors, just to see.

I seemed to have gotten through it, when the chain broke. Now I'm working the new chain to get the joining links to loosen up.