Troul 

Thanks for the language arts info. Was not wanting to insult anyone by coming off as a young donkey to mark up the words. Now that you explained it, I'm sure you could pinpoint the words ya didn't see in relation to acronyms used.

AndreyT

There isn't a slightest doubt that this is scientifically accurate.

A) It is undoubtedly true that friction between cyclist's body parts produces heat. i.e dissipates energy.
B) It is undoubtedly true that the only possible source of that energy is the propelling force that the cyclist generates.

These two statements are barebone undeniable truth. That's what's given. No need for extra sources.

"Scientific theories" or "scientific sources" might be needed to explain the exact mechanism that links A to B, determine the critical points in that mechanism and so on and so forth. But the existence of that link is immediately obvious. It is an axiom, no way around it.

Yellowbeard

In case anybody's curious, the "magic" at play is just to put a couple bearings between the seat tube and the top tube/chainstay junction in the rear, and between the headtube and the upper headset bearing seat in the front.


Basically so you have an extra flexy carbon seat tube and steerer tube.

Maelochs

re: B.), Yes but so wat? I tis a fact but in no way a relevant fact.

re: A.) This is undoubtedly true .... and wholly insignificant as relates to tire pressure. Unless you plan to quantify the varying amount of energy used By the bodies of riders Passively absorbing bumps .... in all likelihood, human physiology being both as standard and as wildly variable as it is there is no way to compensate for or calculate with this quantity.

Further there is no way to adjust it ... save cutting off limbs or removing connective tissue.

That is why people who measure things like rolling resistance at varying tire pressures use mechanical rigs, not random riders. And the people who actually do scientific studies have found that tires which are too hard, In Real Life, are actually less efficient because they bounce, and because they fight the slight deformation which could keep the tires on the road.

Links to such studies are both in this thread and readily available online. Also, look at the pro peloton---one place where efficiency is a definite goal, and comfort is willingly sacrificed for speed. The pros are no longer rolling on 15- or 18-mm tires at 160 or 200 psi ... in fact, some are using 28s. The wider tires is not designed to increase comfort but to increase contact, to absorb tiny imperfections which would rob the bike of speed (think hitting a wall versus rolling over a gentle speed bump.)

Further studies have shown that the chief aero benefits are found when the tire and rim are the same width, so that there can be smooth airflow, and the rim profile with the tire creates a teardrop shape. Those 18 mm tires which narrowed to a 10 mm contact ridge mounted on 13-mm rims were actually not saving drag.

This is all stuff people can look up.

As for the effect of tire pressure in conjunction with suspension systems---I don't care enough to do the research, and apparently either no one else in this thread does, or nobody anywhere does at all.

However .... it seems sensible to me that the tires and the suspension are doing different tasks.

The tire is going to be as hard as it needs to be to provide stable cornering and prevent pinch-flats, while still being supple enough to roll over minor imperfections without converting every impact into an energy-wasting collision.

On bikes designed for cobbles, there are two more considerations: one is the large, square-edged impacts (referring to the force graph, not the shape of the impacted object) that occur when the tire hits a cobble---no tire in road-racing tire is going to absorb that impact---and the equally important issue of rider fatigue.

The sharp impacts with the edge of cobbles saps momentum. If the bike can flex a little (which also saps some momentum) the hope is that overall, less will be lost because the impact will be smoothed out---think of a rectangle versus a very wide speed bump. The sharp-edged impact saps a lot more force (forward momentum) than the more gradual impact, even if Some momentum is lost withing the flexing suspension parts. On the whole, Less is lost ---think of slamming a 9-inch curb with a rigid fork versus an MTB suspension fork. In one case you go over the bars, in the other case the fork compresses and the bike slows but the bike rolls over the curb.

The other consideration---rider fatigue---is also very real, because the shock is being absorbed Somewhere, in this case by the riders' muscles---which means there is less energy available for pedaling. This isn't "friction between cyclist's body parts," it is the muscles being asked to work in many directions and at many rates of speed simultaneously---flexing and relaxing to spin the pedals while also flexing and relaxing at a very high rate to absorb road shock. On a very rough surface, the muscles are vastly less efficient at propulsion because they are exhausted (use a lot of fuel, build up a lot of waste, tear a lot of cell membranes) by the beating of the high-frequency impacts from the rough roads.

The suspension has nothing to do with the rolling resistance of the tires. Optimal pressure for the tires for maximum efficiency is going to be based on the rider's weight. Possibly the road surface would play a factor ... but the huge hits of cobbles are off the scale. Tire pressure cannot be lowered enough to absorb the shock without compromising both puncture protection and efficiency--hence, suspension.

As I noted in my first post (which contained some truth in all its bad humor) It would be possible to think that because a bike had suspension, the tires should be harder to compensate. This would only work if harder tires were more efficient---and also, as I said above, would negate some of the suspension effect. Basically, pumping up the tires hard because the frame has suspension is the worst of both worlds.

I learned this while riding MTB a few decades ago---a really hard tire (which was 55 psi in this case) was okay for a lot of terrain, but when it hit rocky roads, it would literally bounce the front end off the rocks .... the suspension couldn't react because the initial impact with the rocks would bounce the tire clear of the surface.

Hard tires with big knobs cut through soft surface dirt and grabbed the harder pack underneath, but once they hit the rock gardens, the bike was literally all jacked up. I didn't have to crash more than twice to figure that out.

It is less obvious on a road bike because the impacts are smaller and the suspension travel minuscule ... but it is the same effect.

/rant off

Gresp15C

I suggest an experiment. Fill a thermos with meat. Measure its temperature. Strap it onto the bike and go for a ride. Measure the temperature after the ride. With a little bit of math, you can figure out how much power is lost due to vibration of meat.

Maelochs

Now that is an engineer working at maximum!

DrIsotope

You would have to fill some manner of uninsulated container with meat (or meat analog,) as putting it in a vacuum cylinder would undoubtedly have an effect on the heating/cooling of the meat inside said cylinder. Saddlebag full of meat, perhaps?

TimothyH

FlamsteadHill

[QUOTE=cycloaptrgangr;19903046]Apparently Google is broken in your village. Let me help you out:

Independent Laboratory Wheel Energy Oy - Home[/quote

This company wasn't even started until 2003.


This article was only released in 2012.

Narrow, high pressure bike tires have been around since the '60s.

OneIsAllYouNeed

You're going to need a control thermos filled with an incompressible fluid to account for the heat transfer through the thermos.
After the ride, measure the temperatures of the two things, then fire up the grill and drink your hard cider.

cycloaptrgangr

You're really struggling here.

Myosmith

I'll throw a log on the fire

If you want a smooth, shock absorbing/vibration dampening frame, get butted chrome moly. Of course you still have the argument about whether the springiness (is that a word?) shock absorption robs you of energy over a frame made of stiffer material, or if a good portion of that energy is returned when the frame springs back. Would a stiff CF frame with shock absorbing/vibration dampening components or design elements put you right back where you started with CroMo as far as energy losses?

As I understand the tire pressure issue, the larger, lower pressure tires reduce rolling resistance and save energy by deforming slightly to accommodate irregularities in the riding surface. A hard, high pressure tire must rise and drop for each tiny variation in the surface. Not only is power lost to the vibration of this rise and fall, but also to the loss of traction as the high pressure tire spans rather than conforming to the irregularities of the surface. Decreased road vibration also decreases rider fatigue allowing the rider to put out optimum power for longer periods.

u235

And if you get hungry and created enough vibration..

athrowawaynic

Tartare, now.

Medium rare, 3,217,332,783,872,902 miles.

Well done, 5,023,324,231,257,743,642 miles.

No need to check the math.

FlamsteadHill

I guess I'm getting into shape, as I don't feel the slightest bit tired.

Why were bike tires ever inflated to such high pressures? Maybe the roads were like glass in the old days?

ThermionicScott 

Lemme help. ^^

That said, I see enough TLAs in my usual work, so I agree they weren't completely necessary here. Suffice it to say that fatter tires at lower pressures are easier on wheels, frames, and the human body. I'm sold on the concept.