Rolling resistance in real world
 

Reading another thread about tires and there was talk about rolling resistance. Got me thinking about it and has it been quantified over a real world course in terms of speed on a fixed course, time passed in a fixed distance, or distance traveled in time allotted?

For example if tire A has rolling resistance of 1.2 and tire B has rolling resistance of 1.5 (being of greater resistance) how does that translate to real world use as described above?

Real-world tests aren't controlled enough to really mean anything in most cases.

http://anonymous.coward.free.fr/watt...direct-cda.pdf read, understand, think

Are we going to be graded on this?

First, we need to define terms. Are you asking about the rolling resistance of the tires themselves, or the total frictional losses with a human-shaped bag of meat on the saddle?

Yes.

Checkout bikecalculator.com. You can enter specifics for a given ride and it will display a very accurate estimate of power and speed. Change the power estimate and it will recalculate speed over the ride distance. It’s quite interesting. It’s cool to enter Strava segment details and find out how much difference a few extra watts will make. Or how little difference. :lol:

By choosing the lower rolling resistance tyre in real world terms it means that your coefficient of flats has increased by a ratio of 1.5/1.2. The average moving speed improvements are more than offset by the increase in time spent fixing the extra flats. But you now have something else to brag about at the coffee shop.

One theory says the increased comfort from "softer" tires may translate to less fatigue and more efficiency over distance.

That's the only theory that seems to apply to my real world riding. Along with improved bike fit and physical conditioning.

Recently I've swapped my low profile wheels with 700x23 and 700x25 tires at reduced pressure (usually 70-85 psi front) to a semi-aero front wheel (30mm profile, flat blade spokes) with 700x20 tire at 120 psi or more. It's a bit harsher and more tiring over longer rides, but may be offset by slightly improved aerodyamics.

The aero wheel and skinnier, harder tire is faster on a couple of 5 mile loops and over 30-50 mile rides but only on smoother roads -- mostly new or recently repaved access roads next to highways. Little traffic and few stops at night so it's easy to compare. But that same wheel and harder tire is a chore to ride long distances on chipseal and rougher roads, which eliminates the slight aero and rolling resistance advantage.

Too subjective to be useful to anyone else.

Bicyclerollingresistance.com does rolling resistance tests on rollers with a bumpy surface, vs. the perfectly flat rollers that were long used. The theory is that this simulates a more typical riding surface for everyone except velodrome racers! They also do testing at various speeds, not just 25 mph racing speeds.

That type of testing has shown that for most non-racers narrower and higher pressure does not always mean lower rolling resistance. In fact, for the speeds I go at and the roads I ride on, narrow tires at high pressure make no sense. At 15 - 18 mph average, the aero factors are minimal - and my gigantic body width swamps the contribution of the wheels in wind resistance by a huge margin anyway.

I agree with the earlier poster about flats - I'll spend a watt or two to reduce flatting on the road to near zero. BicycleRollingResistance also does puncture resistance testing.

This... give it a read and you will be informed.

It matters.

While the CRR and watts on BRR might not be absolute, the deltas are probably pretty good when doing comparisons.

I get tons of miles out of GP4000's, and assume 5000's would also. I wouldn't commute on them. But for training and racing, yeah.

It's not data, but I've put out power PR's on some personal segments by over 40w before only to still be slower overall......because I was on my "gravel/multisurface" setup with Gators on the bike. Wind those days being negligible.

Also, difference when I was TT'ing practice on a tubular Conti sprinter was dog crap CRR compared to a race tire. It can be shocking how much it matters.

The Bill of Rights bans cruel and unusual punishment.

This is why I use wood instead of pneumatic tires. Makes me so much faster.

Let's not talk about tubeless.

Answer to first question is simply Yes, with the proviso that the verb would be "can" rather than "has." See asgelle's post above. Answer to question 2 is more complicated because of the interaction between tire and surface. For each exact surface condition, there will be a fastest tire. Can you figure out which? Yes, given unlimited funds and time. Is it worth the trouble? Well, if you're a pro it might be worth it to pay someone to find the perfect tire/wheel combo for a particular course, but only if you plan on winning enough prize money and have the ability for that to be possible. You hope your team will take care of all that. Talented amateurs will also go to quite a bit of trouble with it. And remember, it's the fastest tire/wheel combo, not only the tire.

If you're an ordinary bloke, you look at power/speed on different surfaces with different tires and pressures. I don't think it's possible to make really fine judgements in ordinary riding, but I think it's pretty easy to tell a high CRR tire from a low one.

I haven't found low CRR tires to necessarily incur more flats. It's more complicated that that, and also more complicated than the BRR puncture coefficient.

Yeah, regarding punctures, I haven't experienced any more punctures at lower pressure than high or max pressure. But I weigh 150 now, which may help. I weighed 175 when I resumed cycling in 2015 after a 30 year hiatus.

Now I tend to split the difference between the max pressure on the sidewalls and the various formulas for low pressure. Usually with 700x23 that works out to 100 psi rear, 85 front, and for 700x25 around 90 rear, 75 front. I could go lower but that feels about right in handling and comfort. I go by the feel over some familiar rough road patches. If it feels a bit harsh I'll stop and tap the valve a few spurts.

So far my only pinch flat occurred when I was pinched between a couple of trucks and couldn't avoid a brick in the road. No pinch flats on normal rough road spots.

I'm pretty sure I ride in the real world, on real courses on real roads.

Watts are watts. Run a Hard Case tire with butyl tubes, then switch to a GP5K with latex tubes and tell me you didn't pick up 2+ mph at the same wattage.

The subject of my post is that "real roads" RR will vary with road surface characteristics and equipment. There's not one number for one tire at one pressure on any rim on every road, nor can your results be extrapolated to another's conditions and equipment. I would hope you'd agree with that.

Edit: all that's necessary is for the tester to follow the procedure in your document.

This makes me wonder if there is a "kitchen table science" way to measure physiological energy produced, since you'd need to know that instead of/addition to power meter measurements.

With C6H12O6 + 6O2 → 6CO2 + 6H2O (glucose + oxygen -> carbon dioxide + water) for aerobic effort, anyone know precisely where all the water goes? I'm thinking respiration mostly, or a definable percentage of it to define a relation with energy. Then are there enough of the "6H2O" respired to be able to measure? Any biologists out there that have done the math?

You'd have to account for perspiration also but surely you could collect it and weigh it, for a few rides anyway.

IME blood volume and tissue H2O storage increases, and then you pee it out over the next day or two if there's been enough riding and effort time to accumulate a serious amount of H2O. And of course the sweat and respiration losses, as you say. That's not precise of course, just IME. There's also the water released by glycogen breakdown, which I think accounts for a lot of that pee.

He did ask about the "real" world.

I ride on practically bulletproof tires that are on the heavy side, plus have liners in them. But I commute and need to get to work reliably. They still roll reasonably well. I don't feel the difference as much on the velo, because it's already 70 lbs, but it's more noticeable on the (recumbent) bike.

Once I get the velo up to speed though, aerodynamics becomes more important, and that's where it really shines. I had some Kojaks on my bent when I was in Tucson, and on the smooth bike trails around town, they were nice and fast, but it seems like on the surface streets, which were much rougher on average, my 'slow' commuting tires were slightly faster (and way more comfortable).

This is all about measuring the glycogen breakdown as I see it. I figured there'd be a blood volume increase and some would make its way to the bladder, amounts which you couldn't really measure very easily. But if say 10% of it exits in respiration, and you could weigh the difference, then those other accumulations wouldn't change the before/after weight and you could multiply by 10. Or whatever the formula might be. We breathe out water vapor for sure, but I don't know if there is a reliable curve relating water produced and water respired.

I don't think tire pressure is going to help in that situation.

Yeah, I'd need wider tires. About 6 feet wide.