1.2 vs 2.0E motor

[Jeremy McCreary]

Asking your help in estimating 2 key parameters for the OP's bikes of interest:
Bike A = the 26.4 kg Vado 4.0
Bike B = the 20.3 kg Vado SL 2 4.0
Bike C = my 16.3 kg Vado SL 1 5.0 EQ for comparison

The coefficient of rolling resistance (Crr) and the drag area (CdA) are the needed parameters. Rolling resistance is directly proportional to both Crr and gross weight, and air resistance to CdA.

Regarding CdA: This parameter depends on bike and rider size and shape, riding posture, and clothing. Through various means, I estimate my CdA on Bike C in lycra at 0.32. I'm 180 cm and 87 kg. The OP is 91 kg. Bikes A and B are bulkier than C and perhaps a little more upright.

Q1. Bikes A and B likely have larger CdA values than Bike C, but how much larger? Would 10% larger be a fair estimate? That would mean 10% more air resistance at all airspeeds.

Regarding Crr: Testing site www.rollingresistance.com gives Crr = 0.00689 for Bike C's tubeless 38 mm (1.5") Pathfinder Pro tires. No Crr values for the 58 mm (2.3") Pathfinder Sports on A or the 47 mm (1.85") Hemispheres on B.

Q1. These larger commuter tires surely have significantly larger Crr values than the Pathfinder Pros on Bike C. But how much larger? Would 20% larger be a fair estimate? That would mean 20% more rolling resistance.

Thanks!

 

[Stefan Mikes]

Jeremy, not answering your questions, I'd like to tell you about my interesting experience. Nowadays, I'm going on my 50 mile rides with a single battery set (a single ~480 Wh degraded Vado 6.0 battery or SL Main battery + Range Extender, also degraded to some 450 Wh total for Vado SL). The reason for riding 50-milers is the fact it is my gravel racing format. Obviously, the amount of the battery energy used for a ride must be similar in both cases.

• Vado 6.0 feels like a piece of junk at low assistance. The perceived effort is high. The measured effort is, however, low! The average speed achieved on Vado 6.0 is always higher than one achieved on my Vado SL
• Vado SL 1 feels sporty, agile, and easy to pedal at low assistance. I'm putting a considerable leg effort in SL rides! The average speed, however, is always lower than for the big brother!

I even don't want to analyse this. It is what it is!

 

[BlackHand]

@Jeremy McCreary

CdA Q1: all the bikes have 680mm flat bars, though the Vado does have a bit more rise in both stem and handlebars than either of the SL bikes. I doubt there's a huge difference in frontal area, so 10% 'feels' high to me.

As for both Crr and the drag from the bigger wheel/tire combo itself - you're comparing your upgraded aftermarket tubeless to stock options...

I would suggest level the field and calculate using 42mm Pathfinder Pro's on the SL2 and 650Bx47 on the Vado - those have both been tested on BRR. CdA would probably not be hugely different either given the inner wheel size on the respective bikes.

 

[Jeremy McCreary]

As for both Crr and the drag from the bigger wheel/tire combo itself - you're comparing your upgraded aftermarket tubeless to stock options

Correct — mainly because I have some faith in the Crr and CdA values for my SL 1 (Bike C) as is and couldn't find credible Crr values for the other tires.

The OP's only interested in Bikes A and B. Bike C's only there as a somewhat known reference case. For example, it's fair to say that whatever the Crr values are for Bikes A and B, they're no smaller than Bike C's. So if I use the last to calculate rolling resistances for Bikes A and B, we'll at least know that they aren't overestimates.

 

[Jeremy McCreary]

I would suggest level the field and calculate using 42mm Pathfinder Pro's on the SL2 and 650Bx47 on the Vado - those have both been tested on BRR. CdA would probably not be hugely different either given the inner wheel size on the respective bikes.

Per BRR, Crr = 0.00641 for the tubeless 47 mm Pathfinder Pro at 31 psi. But Crr = 0.00689 for the 38 mm version at 36 psi. That's a 7% difference! Unfortunately, need to pay to see the 47 mm Crr at the 38 mm pressure.

So, for lack of better data, I'm just going to do my spreadsheet comparison with Bike C's Crr and CdA values assigned to all 3 bikes.

 

[BlackHand]

And that's the rub - how do you even compare tires of different sizes with so many variables. But comparing at the same pressure would not make sense (you would get an even greater difference in favor of the 47mm). Higher volume tires take lower pressure to reach similar comfort/stiffness. That's why BRR scales the pressures with measured width.

One of my issues with that is they use rims with 17.8mm inner width for tires from 30mm all the way up to 50mm. Modern gravel bikes are going to have rims at least 24 or 25mm or even wider. The 47mm on an SL2 rim would have measured wide enough the BRR would have used a lower pressure for the 'low' pressure. Anyways it's a slippery slope to try to control all those variables and come up with a precise result. At least you're not trying to compare tubed and tubeless tires on BRR - that has its own issues there.

BTW, 30ml of sealant in every tire, regardless of size? That's the right amount for a 25mm road tire. I bet you have 60 or more in your 38mm tires.

 

[Jeremy McCreary]

And that's the rub - how do you even compare tires of different sizes with so many variables.

Thanks for that comparison table and graph. I don't think all those worms would fit in just one can.

I know that in 2025 we're way past all the old rules of thumb regarding Crr and tire width and pressure. But it's still interesting that the 42 mm Pathfinder had a consistently lower Crr than the 38 mm at corresponding pressures. What do you make of that?

Problem is, if there are no good rules of thumb left, and available Crr measurements are also suspect, any hope of quantifying rolling resistance differences between bikes is out the window.

 

[BlackHand]

I agree, there's either a problem with the data, or the tire compound has changed over time. It would help if BRR tested multiple samples of each tire. Also, the 2 older tests were run with tubes and then the tubeless Crr was later calculated when they updated test protocols.

From the BRR conclusion of the 47mm test(2024):
When it comes to rolling resistance, the biggest version of the Specialized Pathfinder Pro falls right in between the 38 and 42 mm sizes. We're unsure if we can draw actual conclusions about the rolling resistance based on our samples. From the looks of it, and because our samples are from 2021, 2022, and 2024, we suspect there to be a manufacturing tolerance, as the numbers just don't seem to make sense.

This is more the type of result you would expect, but these are all from the same recently updated lineup and tested within 10 months of each other

I generally like the pedaling efficiency rig that Cycling News has used better, but it doesn't try to resolve down to Crr.

I guess something like a pinewood derby setup for bikes in conjunction with wind tunnel numbers might get you there but that's not really very practical.

 

[Jeremy McCreary]

One thing's for sure: My Cdh (coefficient of data headaches) just went through the roof.

Sure would be fun to try those 40 mm P Zeros on my SL at 45 psi, but too much offroad around here for routine use.

 

[Stefan Mikes]

Guys, I think you discuss rather irrelevant things We are talking about several watts of difference. How much does affect it us e-bikers? Leave these things to road racing pros!
Rolling resistance is not everything. I have replaced fast rolling Pathfinders with aggressive Rhombus because the traction in rough terrain overweighs such funny things like several watts on asphalt (which are even unnoticeable to the e-bike motor)

 

[Jeremy McCreary]

Guys, I think you discuss rather irrelevant things We are talking about several watts of difference. How much does affect it us e-bikers? Leave these things to road racing pros!
Rolling resistance is not everything. I have replaced fast rolling Pathfinders with aggressive Rhombus because the traction in rough terrain overweighs such funny things like several watts on asphalt (which are even unnoticeable to the e-bike motor)

Sure, you can always motor through an increase in rolling resistance, but at the cost of battery range. On a long SL ride with that smallish battery, those "few watts" can add up to the difference between getting home on your main battery or wishing you'd brought the RE.

 

[Stefan Mikes]

or wishing you'd brought the RE.

Why not?