GhostRider62

My new wheels with GP5000 TR S tubeless setup seemed a little slow. I have a road that I have measured my rolling resistance Crr using VE chung method. With GP5000 and latex tubes, two years ago I measured 0.0042 and 0.005 with butyl tubes. The pavement was new just under three years ago. Off I went and measured a whopping 0.0066 on my tubeless setup. Same 25 mm width on both and I used the same 89 psi. Temperatures were 73F vs upper 70's two years ago.

I can think of five explanations.

1. I am 30 pounds heavier (Crr is not constant, it is load and speed dependent)
2. The road surface got really bad in 2 years
3. Powertap G3 vs the crank based PM now used
4. These tires are slow
5. 45 ml of sealant is too much?

Is a Crr 0.0066 out of the ordinary for real world, worn pavement? Anyone ever measure? Anyone know of real world tests having been done quantitatively? The only ones I have seen are on velomobiles and 0.0066 is a good number for them and 0.01 is not out of the realm for mediocre tires or misaligned suspension. If this is normal on a road bike on 3 year old worn pavement, I won't chase my tail so to speak.

WhyFi

RChung

Wildwood

I vote #4.
Conti 5000 = the gatorskins of high-end supple tires. IMO, compared w/ Vittoria and Veloflex and Specialized.
Personally, I could care less about rolling resistance comparisons among similar type tires.

I need to lose 10lbs, get stronger, ride more aerodynamically and improve my spin.

Koyote

Such uncontrolled on-the-road testing is questionable, at best. The noise from numbers 1-3 are not the only problems with comparing two different runs from a couple years apart.

More importantly, I'll ask the obvious question: are you racing? If no, then worrying about crr seems a bit silly. If yes, then you should consider how much slower you'd be with a puncture that might've sealed up with a tubeless setup. (And you might work on item #1 on your list.)

bblair

How can you change 5 variables and expect to have anywhere a meaningful result?

Wow, talk about marginal gains! Are you preparing for the Olympics or World Hour Record?

rsbob 

30 lbs is a massive difference. Imagine carrying 3 10 lb babies around full time and then placing them in a trailer with zero friction behind your bike. Now think of the additional pressure placed on your tires and the impact on rolling resistance if you were holding those babies in your arms when you ride. Am not an engineer and it shows.

cxwrench

Trying to compare results with all the variables you have is ridiculous.

Barry2 

I too am interested in rolling resistance, but would never try to measure it on the road.

I use a Mouse to determine rolling resistance (click here)

Barry

RChung

0.0066 is a lot for those tires. How much has the road surface changed? Sometimes I take a photo of the road surface with my phone cam so I can keep track of the surface.

What was the drive train loss you assumed for the crank PM?

30 pounds shouldn't matter -- the calc accounts for changes in mass.

Can you describe the course and your protocol a little more? Were you wearing the same clothes (considering the 30 lb change in mass)? What was the change in CdA? An error in estimated CdA (for example, because of an error in wind estimation) of .01 m^2 is *roughly* equivalent to an error in Crr of .001, so if your estimate of CdA were .02 m^2 too low, it would make the estimated Crr in the ballpark of about .002 too high. You're kinda tall and heavy, aren't you? If so, an error in CdA of .01 m^2 might cause a slightly larger error in Crr.

KerryIrons

How much less could you care? I you could care a LOT less then this must be a very important issue for you. If you could care only a little bit less then maybe not so much. Of course if you meant to say you COULDN'T care less then we might better understand that you don't care at all. Inquiring minds want to know.

Buzzkill53120

I have the solution, but it works only in the case of spherical cows in a vacuum.

Wildwood

Silly wabbit, Tricks are for kids.

burnthesheep

Reduce the variables and create a repeatable protocol. ABAB, or ABBA style. Same power meter, surface, bike, wheels, etc….Then try again.

Love all the BF Freds rolling into a topic like this to express their ignorance with a bunch of “couldn’t care less” and “flying cows” BS.

Contribute or GTFO.

PeteHski

I really don't think so considering the pro races they've won.

RChung

Almost every argument in cycling fora:
1. Only the pros need to worry about that. Are you a pro?
2. The best riders are the best because of what they do so just imitate them.
3. Things I can't see, can't measure, or don't care about aren't important.
4. Things I can see or measure are important, so you should care about them.
5. If I don't know how to do something, it's too complicated for anyone to know how to do.

Wildwood

In the real world -
1. rolling resistance of your tires (within a given category) is an order of magnitude less important than moving the air resistance at speed
1a. Not comparing road race 25mm to hybrid 35s... etc
2. Measuring rolling resistance with uncalibrated devices, years apart and with other variables - to judge a tire is an exercise in useless statistics.
3. You don't always get the answer you want
3a. See post #3. Lose weight (10# for me), get stronger, ride aerodynamically and spin better.
4. Buy tires that you think make your ride more enjoyable
5. If you race, ride what your sponsor tells you
6. If you race and don't have a sponsor - you have bigger problems than tire rolling resistance
7. If you sell expensive tires, worry about RR, esp Forum gossip, totally unfounded.

Don't call me Fred, my name is 'Mr. Wildwood'. Read everyone's posts completely before 'burning' contributors or suggesting someone GTFO.
YRRMV (Your rolling resistance may vary)

asgelle

It didn't take long to validate almost every element of the previous post (#15).

RChung

I wouldn't at all say it's an order of magnitude less important. Effect size isn't the same as importance. It's true that at the speeds we normally ride at, for riders of a normal size and weight, a difference in CdA of .01 m^2 is roughly equivalent to difference in Crr of .001, so the numeric relationship between the coefficients is around an order of magnitude different-- but their importance depends on riding speed and road gradient. However, GhostRider62 wasn't asking about importance, he was asking about the size of the coefficient and whether it seemed to make sense. It's non-responsive to his question to substitute your assessment of importance for his interest in the coefficient.

Wildwood

And Shimano equipment is 5 X better because they are represented in the pro peloton 5 X more than other companies (individually).

and I should apologize..., my Conti 5000s are an early version, before tubeless ready was out. With latex tubes, I have to run 80-85psi in the 5000s to have the same 'supple' feel of Vittoria & VeloFlex at 100-105. If all are 25mm = the one with the lower pressure by ~20psi will absolutely have the highest rolling resistance, tubeless ready or not.

GhostRider62

I use two protocols generally. The half pipe one would be where I would control every variable to the extent possible. For this testing and what I have used to many times is an up the river and down the river of 7-10 miles each direction holding the same power. I averaged around 190 watts and around 19 mph in one direction and 21 mph in the other (a greater speed difference would be more ideal). I used the same Assos S7 white jersey and same Assos T centos bibs as two years prior. The shoes are the same. The pedals are not the Frogs but the ZYZRs. I would do a run up the river and adjust your Crr and Cda figure in GoldenCheetah. I would do the same for the downstream run. I assumed 2% drivetrain losses(my chain was hot waxed in Silca wax 150 miles ago, so, not the freshest but my drivetrain is immaculate, BB and wheel bearings are smooth albeit just high quality steel, no ceramic or anything). i only test on relatively calm days. I do this up and back testing because it gets me some training and for large changes, it usually shows up in the data. For finer or more precise measurements, I do the half pipe on calm days and repeat many times, obviously taking note of temperature, humidity, and barometric pressure.

The road in question is a little used but scenic (Rt 29 in NJ between Frenchtown and Stockton) state highway with a wide shoulder. They use a lot of salt in winter. It looks like the tar portion of the mix suffers. Visually, it is not as smooth but it also does not have any potholes. 2 years ago, it was smooth as a baby's bottom. I wish I took photos.

I actually have the exact wheels that I tested with last time and they still have the same tires and tubes. I am going to do an ABBA test to compare. Maybe the road. But I also did a 200K where my power output should have given me faster speeds.

For those who think I am misguided, I do sometimes race and a few years ago I had my eyes on a 24 hour record. At this time, I just want to be as efficient as possible with randonneuring so that I can sleep. Randonneurs do distances of 200, 300, 400, 600, and 1200km. I am trying to qualify for Paris Brest Paris next year. Saving a couple hours would be used for sleeping.

Wildwood

I'm a slow typer.

HTupolev

What are you comparing with what? Under many circumstances, it's true that the total aerodynamic drag on a bike+rider system is far higher than the rolling resistance. But aerodynamic drag happens everywhere in the system, while rolling resistance can be multiplicatively scaled by changing just the tire setup.

The observed Crr difference that GhostRider62 made the thread over is .002, which is a long ways from nothing. Using the usual force model where rolling is m*g*Crr and aero is .5*(air density)*CdA*(v^2), for example, plugging in mundane numbers gives results like:



Why not do those things and also use a fast tire setup?

GhostRider62

I was asking if others had similar experiences or data.

The reason was I did not want to chase my tail. If it isn't the tires, it is bearings but very doubtful, probably the road. Doubtful the tires. Possibly too much sealant inside. In any case, I am quite confident I can make improvements.

I know how to run experiments. I spent a good part of my career running or reviewing experimental results. I accept large error bars around my Crr 0.0066 point estimate (N =2). I had been suspecting friction somewhere on my bike was excessive. Yes, I have much bigger problems. You all know that. I also accept that. I just want to use as little energy as possible to go long distances. Why do you have a problem with that? I also enjoy optimisation. Why do you have a problem with that? Going as fast as I can on as little energy as possible over many hours is appealing to me. I do not know why but it appeals to me.

GhostRider62

BTW.....weight should not matter. Crr is generally thought to be load and speed independant, although I somewhat disagree with that. I am fat because I have had a lot of injuries. I promise to lose the weight. Weight is taken into consideration and really cannot be much of a factor in the Crr estimation that I provided.

RChung

Hmmm. That's possible, but not guaranteed. Depends on the road surface.