wphamilton

I've heard that, a lot, about Gator Hardshell tires. I wouldn't dispute their other advantages, but that they're a drag on performance seems to be a pretty solid objection. I dislike the cheap Kenda tires for that reason, although I'm sure they're durable.

dmanthree

Totally agree, and I run the same tires for the same reasons. Except I've mounted the GP 5000 tires for this summer. And yes, while the GP 4 Season is a really good tire, it's not as smooth, supple, or "light" as the GP 5000. But using the GP 4 Season has one advantage: I've never flatted one.

f4rrest

I was just inferring what the underlying model suggests, based on the graph provided.

An asymtote suggests infinite equivalent mass as the slope approaches 0.

canklecat

Loops. The tailwind on one side of the loop offsets the headwind on the other side.

Later today I'll ride a familiar 5 mile loop that's an elongated oval running north/south with only 100 yards or so running east/west.

With today's 15-20 mile wind from the south my tailwind advantage on one side will be negated by the headwind on the other.

Accuracy of the online calculators depends on putting out the same effort on the tailwind side, not slacking off and coasting or piddle pedaling.

Unless I have an exceptional day, I'll average 16 mph and 160 Watts, with a few short bursts of power on the short steep climbs. Pretty much the same on my old steel bike and carbon frame bike.

asgelle

Except it doesn't. You spend more time in the headwind than the tailwind so for constant power, your overall time will be slower in the headwind/tailwind loop than the one with no wind at all.

Racing Dan

Does this assume equal power or equal speed? - The steeper the slope, the slower you go and crr becomes less of a concern.

Spoonrobot 

That's not how it works. You always get less from the tailwind than you give up for the headwind - theoretically your oval course could be such that the headwind side is mathematically short enough to be offset by the tailwind side but your description already rules that out - as well it would only apply at specific headwind and tailwind speeds. This graph and the accompanying linked article and equation therein illustrate why:



https://www.sheldonbrown.com/brandt/wind.html

Side note: I wholly recommend reading the entirety of the Jobst Brandt Archive at https://yarchive.net/bike/ it's really a phenomenal archive and there are tons of things that are still being argued today.

Racing Dan

Sometimes you can shield yourself from headwind and expose yourself to tailwind, depending what loop and what direction you take. It pays to think here.

asgelle

That would be no wind/tailwind, hardly the same as saying headwind and tailwind cancel out.

Racing Dan

I didnt say it cancels.

HTupolev

The only way it cancels is if you're more wind-exposed during the tailwind portions than the headwind and crosswind portions.

Even in a straight out-and-back with a pure tailwind one way and a pure headwind the other, the cost of the headwind will tend to be larger than the benefit of the tailwind. The more crosswinds that get introduced into the route, the worse the situation gets.

Spoonrobot 

Read the post I responded to, that’s not what is being discussed.

As noted - your scenario is no wind/tailwind - completely irrelevant given we are discussing headwind/tailwind and the possibility of one canceling out the other.

I think, perhaps, you may have thought too much.

DrIsotope

The Hardshell sacrifices everything for straight up durability. They last forever. I got 6,500 miles out of my front tire, and it still looked pretty good when it came off. Never got a single puncture.

But they roll like brick, they have sidewalls that are both thin and stiff all at once, the decorative thread on those sidewalls continually unravels, and they're absolutely terrifying on wet ground.

It's a lot of compromise.

canklecat

Thanks, I'll check it out. Sounds interesting. And I'm always open to having my misconceptions disabused.

My best guess, judging from terrain maps, is the rolling prairie terrain funnels wind differently throughout my usual loops and circuits. I seem to get the most tailwind boost on the longest incline. When the wind changes directions, that's also the segment that feels slowest. The flip side of the loop is more sheltered between terrain and tree cover, so any head/tail wind effect is erratic.

And the pavement and traffic hazards vary a bit throughout. On the elongated oval (it runs more N/NW to S/SE than straight up and down), the longest continuous incline of around 2% for a mile feels pretty fast to me in most conditions. But that's because the pavement is smoother, that side of the access road loop is less sheltered from wind in a couple of key places, and there are fewer merging highway traffic hot spots to watch for. The flip side feels slower because the wind seems to funnel more effectively right on the steepest climbs (terrain and tree cover), the pavement is slower (a mix of striated concrete, chipseal, rough seams between paved segments), and there's one high risk merge area from the nearby highways -- not much traffic there any time, but the mix design encourages drivers to go way too fast, whereas the other side of the loop has a traffic calming effect.

It would be interesting to borrow a power meter, or a bike with a power meter, to test my hunches about the terrain, wind, etc. I've just guesstimated based on power meter data from other riders my size, weight, age, etc. Strava and online calculators usually are pretty close to the measured data by folks with power meters. I'm just not motivated to buy such an expensive doodad ... yet. Not ruling it out though. I thought I'd never care about a carbon bike but now I have one -- an old Trek 5900, nothing fancy, but it works and it's fun on climbs.

Anyway, back to the thread topic, for my rides it still seems like aerodynamics are a bigger factor than tire rolling resistance. With physical therapy this year for a couple of wreck injuries (I've been hit by cars twice in 15 years), I'm regaining some flexibility, better able to stay in the drops or stay lower, longer. That, and not wearing flappy clothing, seems to matter more than my tires. That was one of those misconceptions I had for awhile, before checking my data over three years and realizing wind resistance mattered more than tire rolling resistance.

Bah Humbug

Ever watch your wife lose out on a slot to the 70.3 world championships in France by four seconds? I have.

wphamilton

His chart is presented in terms of force (not power), and neither the resisting forces of rolling resistance nor weight going uphill vary much with your speed or power output.

1. Riding uphill the gravitational force is proportional to your total weight. And sine of the angle of incline. That's the whole of it at low speeds. You can derive this from basic physical laws.
2. Riding anywhere, rolling resistance is proportional to the load (weight) perpendicular to the surface (cosine of the angle of incline). Again, that's it for low speeds. This one is not really a "law of physics" since it derives from observation, and not from any base principles. Hence, "it varies".

His chart takes the above two statements and compares the forces, independently of speed or power.

RedBullFiXX

I've got about 6,500 on a Pro-One tubeless front as well, may change it due to weather checking before it shows any significant signs of wear ?
Rears last near 2K mi

noodle soup

Did she get in as an alternate?