Modeling a Creo 2 motor in a Vado SL 1: Effect on rider power and battery consumption

[Jeremy McCreary]

What if you put a Creo 2 motor in a Vado SL 1 (SL for short) with no other change? How would battery consumption and rider power requirements compare with those of the stock SL or a Creo 2?

Haven't heard of anyone actually trying it, but these things can be modeled. So I made a spreadsheet model based on (a) official SL 5.0 EQ and Creo 2 Carbon Comp specs, (b) the resistance formulas and parameters in Wilson & Schmidt, 2020, Bicycling Science, 4th ed., and (c) the model of the Specialized power-sensing mid-drive PAS presented here.

Modeled 2 plausible riding scenarios: (1) a 20 mph "dash" on a 0% grade, and (2) an 8 mph "climb" on a 5% grade. Both scenarios assume steady ground speed, constant grade, smooth pavement, still air, cycling clothes, and a ½ hour duration. With 3 ebikes dashing and climbing in all 3 assist modes, I modeled 18 cases in all.

Graphical results

These bar graphs the show the rider power Pr needed to hold scenario speed, with the dash above and the climb below. Blue bars are the stock SL 1 (SSL); red, the modified SL 1 (MSL); and yellow, the Creo 2.

NB: When visually comparing the dash and climb graphs, note that their vertical Pr axes differ slightly in scale.

These bar graphs the show the battery consumption Cu in Wh in all 18 cases — again with the dash above and the climb below.

NB: When visually comparing the dash and climb graphs, note that their vertical Cu axes also differ slightly in scale.

Bottom line
Relative to the SSL, the MSL would save you a little effort in all but the TURBO climb. But it would burn more battery in all cases.

Not much of a payoff. If you really wanted to cut the needed rider contributions in the modeled scenarios, you'd ride the Creo 2 on the drops in both. You'd always use more battery than the SSL on the climb but generally less on the dash.

Other gleanings from the model
1. As expected, the greater the rider contribution, the less battery consumed in all cases. The 2 bikes with the larger Creo 2 motor used more battery than the SSL with the smaller motor in all but the SPORT and TURBO dashes.

2. On the TURBO climb, the needed Pr was greatest for the SSL and roughly equal for the other 2 bikes. In all other cases, the SSL needed the most Pr, and the Creo 2 the least, with the MSL in between. This latter pattern is what you'd expect given the weight, aerodynamic, and motor differences involved. Not sure why the TURBO climb went differently.

3. Both SLs need significantly more Pr and battery in the dash than in the much slower climb, while the Creo 2's needs differed little between dash and climb. The SLs also needed more Pr and battery than the Creo 2 in the dash in all assist modes.

These relationships were driven mainly by the aerodynamics of rider posture. In short, riding the Creo 2 on the drops largely offset the extra power drawn by its larger motor for a given Pr — at least in the modeled dash and climb. By sitting the rider up somewhat, a flat-bar Creo 2 would lose some significant advantages.

4. The MSL used the most battery across the board, but the Creo 2 almost caught up on the climb. The SSL tended to use more battery than the Creo 2 in the dash but always less on the slower climb, where the Creo's lower drag factor did it less good.

Bike considerations
All 3 ebikes would have the same 320 Wh battery and Specialized power-sensing PAS. The main differences would be in their motors, weights, and rider aerodynamics.

The Mahle 1.1 SL motor in the SSL puts out up to 240 W of mechanical power and 35 Nm of torque at a boost factor of 1.8. The stronger, heavier Mahle 1.2 SL motor in the Creo 2 and MSL puts out up to 320 W and 50 Nm at boost 2.3. Go here to see how this data figures into the Specialized mid-drive PAS.

The Creo 2's small but significant weight advantage — especially over the MSL — reduces its tire and slope resistances. Ridden on the drops, as assumed here, the Creo 2 would also have a big aerodynamic advantage over the flat-bar SLs at speed. These differing resistances definitely showed up in the model results.

For assist modes, I used the factory settings in the Universal preset: ECO = 35/35, SPORT = 60/60, and TURBO = 100/100. (Go here to see how these settings work in the Specialized mid-drive PAS.)

Methodogy
For each of the 6 possible bike+scenario combos, I first calculated the 3 main external resistances (air, slope, and tire) using drag factors and rolling resistances adjusted from Table 5.2 in Wilson & Schmidt. From these resistances, I then calculated Pe, the combo's total external power loss.

The power balance needed for steady ground speed means that

Pe = Pd = (Pr + Pm) Ed

where Pd is the net mechanical power delivered to the rear wheel, Pm is mechanical motor power, and Ed = 0.98 is drivetrain efficiency. Here, Pr and Pm are taken at the crank, and Ed is assumed to be the same in all cases. In fact, the dash's smaller cassette cogs would be less efficient, but not by enough to worry about here.

Now, in the Specialized PAS, Pm varies mainly with Pr. The relationship is easily modeled. To enforce power balance in each case, I used trial and error to find the Pr making Pd = Pe. That Pr is the rider power shown in the result graphs.

In each case, the electrical energy Cu consumed over time T = 0.50 hr is just

Cu = Pm T / Ee

where Cu is in Wh, and Ee, the electrical efficiency, is assumed fixed at 0.80. In fact, Ee varies mainly with cadence in Specialized mid-drives, with a peak at 80-90 rpm. Here I've assumed that the rider has the legs and gearing needed to keep the same efficient cadence from case to case.

 

[mfgrep]

What if you put a Creo 2 motor in a Vado SL 1 (SL for short) with no other change? How would battery consumption and rider power requirements compare with those of the stock SL or a Creo 2?

View attachment 191858
Haven't heard of anyone actually trying it, but these things can be modeled. So I made a spreadsheet model based on (a) official SL 5.0 EQ and Creo 2 Carbon Comp specs, (b) the resistance formulas and parameters in Wilson & Schmidt, 2020, Bicycling Science, 4th ed., and (c) the model of the Specialized power-sensing mid-drive PAS presented here.

Modeled 2 plausible riding scenarios: (1) a 20 mph "dash" on a 0% grade, and (2) an 8 mph "climb" on a 5% grade. Both scenarios assume steady ground speed, constant grade, smooth pavement, still air, cycling clothes, and a ½ hour duration. With 3 ebikes dashing and climbing in all 3 assist modes, I modeled 18 cases in all.

Graphical results
View attachment 191860
These bar graphs the show the rider power Pr needed to hold scenario speed, with the dash above and the climb below. Blue bars are the stock SL 1 (SSL); red, the modified SL 1 (MSL); and yellow, the Creo 2.

NB: When visually comparing the dash and climb graphs, note that their vertical Pr axes differ slightly in scale.

View attachment 191859
These bar graphs the show the battery consumption Cu in Wh in all 18 cases — again with the dash above and the climb below.

NB: When visually comparing the dash and climb graphs, note that their vertical Cu axes also differ slightly in scale.

Bottom line
Relative to the SSL, the MSL would save you a little effort in all but the TURBO climb. But it would burn more battery in all cases.

Not much of a payoff. If you really wanted to cut the needed rider contributions in the modeled scenarios, you'd ride the Creo 2 on the drops in both. You'd always use more battery than the SSL on the climb but generally less on the dash.

Other gleanings from the model
1. As expected, the greater the rider contribution, the less battery consumed in all cases. The 2 bikes with the larger Creo 2 motor used more battery than the SSL with the smaller motor in all but the SPORT and TURBO dashes.

2. On the TURBO climb, the needed Pr was greatest for the SSL and roughly equal for the other 2 bikes. In all other cases, the SSL needed the most Pr, and the Creo 2 the least, with the MSL in between. This latter pattern is what you'd expect given the weight, aerodynamic, and motor differences involved. Not sure why the TURBO climb went differently.

3. Both SLs need significantly more Pr and battery in the dash than in the much slower climb, while the Creo 2's needs differed little between dash and climb. The SLs also needed more Pr and battery than the Creo 2 in the dash in all assist modes.

These relationships were driven mainly by the aerodynamics of rider posture. In short, riding the Creo 2 on the drops largely offset the extra power drawn by its larger motor for a given Pr — at least in the modeled dash and climb. By sitting the rider up somewhat, a flat-bar Creo 2 would lose some significant advantages.

4. The MSL used the most battery across the board, but the Creo 2 almost caught up on the climb. The SSL tended to use more battery than the Creo 2 in the dash but always less on the slower climb, where the Creo's lower drag factor did it less good.

Bike considerations
All 3 ebikes would have the same 320 Wh battery and Specialized power-sensing PAS. The main differences would be in their motors, weights, and rider aerodynamics.

The Mahle 1.1 SL motor in the SSL puts out up to 240 W of mechanical power and 35 Nm of torque at a boost factor of 1.8. The stronger, heavier Mahle 1.2 SL motor in the Creo 2 and MSL puts out up to 320 W and 50 Nm at boost 2.3. Go here to see how this data figures into the Specialized mid-drive PAS.

The Creo 2's small but significant weight advantage — especially over the MSL — reduces its tire and slope resistances. Ridden on the drops, as assumed here, the Creo 2 would also have a big aerodynamic advantage over the flat-bar SLs at speed. These differing resistances definitely showed up in the model results.

For assist modes, I used the factory settings in the Universal preset: ECO = 35/35, SPORT = 60/60, and TURBO = 100/100. (Go here to see how these settings work in the Specialized mid-drive PAS.)

Methodogy
For each of the 6 possible bike+scenario combos, I first calculated the 3 main external resistances (air, slope, and tire) using drag factors and rolling resistances adjusted from Table 5.2 in Wilson & Schmidt. From these resistances, I then calculated Pe, the combo's total external power loss.

The power balance needed for steady ground speed means that

Pe = Pd = (Pr + Pm) Ed

where Pd is the net mechanical power delivered to the rear wheel, Pm is mechanical motor power, and Ed = 0.98 is drivetrain efficiency. Here, Pr and Pm are taken at the crank, and Ed is assumed to be the same in all cases. In fact, the dash's smaller cassette cogs would be less efficient, but not by enough to worry about here.

Now, in the Specialized PAS, Pm varies mainly with Pr. The relationship is easily modeled. To enforce power balance in each case, I used trial and error to find the Pr making Pd = Pe. That Pr is the rider power shown in the result graphs.

In each case, the electrical energy Cu consumed over time T = 0.50 hr is just

Cu = Pm T / Ee

where Cu is in Wh, and Ee, the electrical efficiency, is assumed fixed at 0.80. In fact, Ee varies mainly with cadence in Specialized mid-drives, with a peak at 80-90 rpm. Here I've assumed that the rider has the legs and gearing needed to keep the same efficient cadence from case to case.

Holy crap you put some thought into this. Different strokes. I'd just try it and see how it goes in real time. Don't like the results? Go back.

 

[Calcoaster]

What if you put a Creo 2 motor in a Vado SL 1 (SL for short) with no other change? How would battery consumption and rider power requirements compare with those of the stock SL or a Creo 2?

View attachment 191858
Haven't heard of anyone actually trying it, but these things can be modeled. So I made a spreadsheet model based on (a) official SL 5.0 EQ and Creo 2 Carbon Comp specs, (b) the resistance formulas and parameters in Wilson & Schmidt, 2020, Bicycling Science, 4th ed., and (c) the model of the Specialized power-sensing mid-drive PAS presented here.

Modeled 2 plausible riding scenarios: (1) a 20 mph "dash" on a 0% grade, and (2) an 8 mph "climb" on a 5% grade. Both scenarios assume steady ground speed, constant grade, smooth pavement, still air, cycling clothes, and a ½ hour duration. With 3 ebikes dashing and climbing in all 3 assist modes, I modeled 18 cases in all.

Graphical results
View attachment 191860
These bar graphs the show the rider power Pr needed to hold scenario speed, with the dash above and the climb below. Blue bars are the stock SL 1 (SSL); red, the modified SL 1 (MSL); and yellow, the Creo 2.

NB: When visually comparing the dash and climb graphs, note that their vertical Pr axes differ slightly in scale.

View attachment 191859
These bar graphs the show the battery consumption Cu in Wh in all 18 cases — again with the dash above and the climb below.

NB: When visually comparing the dash and climb graphs, note that their vertical Cu axes also differ slightly in scale.

Bottom line
Relative to the SSL, the MSL would save you a little effort in all but the TURBO climb. But it would burn more battery in all cases.

Not much of a payoff. If you really wanted to cut the needed rider contributions in the modeled scenarios, you'd ride the Creo 2 on the drops in both. You'd always use more battery than the SSL on the climb but generally less on the dash.

Other gleanings from the model
1. As expected, the greater the rider contribution, the less battery consumed in all cases. The 2 bikes with the larger Creo 2 motor used more battery than the SSL with the smaller motor in all but the SPORT and TURBO dashes.

2. On the TURBO climb, the needed Pr was greatest for the SSL and roughly equal for the other 2 bikes. In all other cases, the SSL needed the most Pr, and the Creo 2 the least, with the MSL in between. This latter pattern is what you'd expect given the weight, aerodynamic, and motor differences involved. Not sure why the TURBO climb went differently.

3. Both SLs need significantly more Pr and battery in the dash than in the much slower climb, while the Creo 2's needs differed little between dash and climb. The SLs also needed more Pr and battery than the Creo 2 in the dash in all assist modes.

These relationships were driven mainly by the aerodynamics of rider posture. In short, riding the Creo 2 on the drops largely offset the extra power drawn by its larger motor for a given Pr — at least in the modeled dash and climb. By sitting the rider up somewhat, a flat-bar Creo 2 would lose some significant advantages.

4. The MSL used the most battery across the board, but the Creo 2 almost caught up on the climb. The SSL tended to use more battery than the Creo 2 in the dash but always less on the slower climb, where the Creo's lower drag factor did it less good.

Bike considerations
All 3 ebikes would have the same 320 Wh battery and Specialized power-sensing PAS. The main differences would be in their motors, weights, and rider aerodynamics.

The Mahle 1.1 SL motor in the SSL puts out up to 240 W of mechanical power and 35 Nm of torque at a boost factor of 1.8. The stronger, heavier Mahle 1.2 SL motor in the Creo 2 and MSL puts out up to 320 W and 50 Nm at boost 2.3. Go here to see how this data figures into the Specialized mid-drive PAS.

The Creo 2's small but significant weight advantage — especially over the MSL — reduces its tire and slope resistances. Ridden on the drops, as assumed here, the Creo 2 would also have a big aerodynamic advantage over the flat-bar SLs at speed. These differing resistances definitely showed up in the model results.

For assist modes, I used the factory settings in the Universal preset: ECO = 35/35, SPORT = 60/60, and TURBO = 100/100. (Go here to see how these settings work in the Specialized mid-drive PAS.)

Methodogy
For each of the 6 possible bike+scenario combos, I first calculated the 3 main external resistances (air, slope, and tire) using drag factors and rolling resistances adjusted from Table 5.2 in Wilson & Schmidt. From these resistances, I then calculated Pe, the combo's total external power loss.

The power balance needed for steady ground speed means that

Pe = Pd = (Pr + Pm) Ed

where Pd is the net mechanical power delivered to the rear wheel, Pm is mechanical motor power, and Ed = 0.98 is drivetrain efficiency. Here, Pr and Pm are taken at the crank, and Ed is assumed to be the same in all cases. In fact, the dash's smaller cassette cogs would be less efficient, but not by enough to worry about here.

Now, in the Specialized PAS, Pm varies mainly with Pr. The relationship is easily modeled. To enforce power balance in each case, I used trial and error to find the Pr making Pd = Pe. That Pr is the rider power shown in the result graphs.

In each case, the electrical energy Cu consumed over time T = 0.50 hr is just

Cu = Pm T / Ee

where Cu is in Wh, and Ee, the electrical efficiency, is assumed fixed at 0.80. In fact, Ee varies mainly with cadence in Specialized mid-drives, with a peak at 80-90 rpm. Here I've assumed that the rider has the legs and gearing needed to keep the same efficient cadence from case to case.

Your theory and calculations look interesting. The real life experience could be much different, though. There’s a long time creo rider who posts on another site who moved from a creo 1 to a creo 2 and found he had to significantly detune the creo 2 to prevent it from drastically dropping motor power due to its built in heat protection logic. As I recall he rides in fast, long group rides and used the creo 1 at 100% turbo mode. His creo 2 would drop power in half several miles into a ride, leading him to detune it to something like 75% max power in order to sustain its output. I think his solution gave him an improvement over his Creo 1 but not nearly as much as he hoped for. He’s the ebike expert in a specialized store so I think his experience is a very credible one.

 

[Jeremy McCreary]

Holy crap you put some thought into this. Different strokes. I'd just try it and see how it goes in real time. Don't like the results? Go back.

The idea of an SL 1 with a Creo 2 motor has come up many times in SL-related threads. Some thought it could be a dream bike, and rumors of such an update were rife in late 2024. Seemed like a good idea to me at the time as well.

The nuts and bolts of souping up the SL 1 like this have also been discussed. Apparently not an easy or cheap DIY mod to try, let alone reverse.

The net effect on battery range has been debated as well. The model makes clear predictions here: In the 2 scenarios covered, swapping the motor without upping the battery would reduce exertion in most cases but would always reduce range — this in an ebike with limited range to begin with.

So what did I learn from the model? The SL 1's a beautifully integrated package just the way it is. This oft wished-for mod would probably be a bad deal for range-conscious riders.

 

[Jeremy McCreary]

Your theory and calculations look interesting. The real life experience could be much different, though. There’s a long time creo rider who posts on another site who moved from a creo 1 to a creo 2 and found he had to significantly detune the creo 2 to prevent it from drastically dropping motor power due to its built in heat protection logic. As I recall he rides in fast, long group rides and used the creo 1 at 100% turbo mode. His creo 2 would drop power in half several miles into a ride, leading him to detune it to something like 75% max power in order to sustain its output. I think his solution gave him an improvement over his Creo 1 but not nearly as much as he hoped for. He’s the ebike expert in a specialized store so I think his experience is a very credible one.

Good point, interesting complication. Must've been very frustrating to get blindsided by thermal protection like that — especially for an expert.

Of course, all models have their limitions. Lots of potential gotchas in a system as complicated as a Specialized ebike.

 

[Stefan Mikes]

I would say the firmware would not have matched in the first place. Creo 2 batteries are "flashed" with the new firmware to retain the compatibility. What about the TCU firmware? Is it the same on Creo 2 and Vado SL 1?

 

[Stefan Mikes]

As I recall he rides in fast, long group rides and used the creo 1 at 100% turbo mode.

I wonder for how long time and for what distance
36 km and 1 hour? Not much as for a roadie peloton

I had to say that as my workouts with roadies (Vado 6.0) involved 69 km, it was 31.1 km/h average speed and we pedalled for 2 hours and 13 minutes. It was my 500 Wh battery and I had to take two of them to be able to come to and return from the workout On The Wheels. The guy in question has a 320 Wh battery.

 

[mschwett]

Your theory and calculations look interesting. The real life experience could be much different, though. There’s a long time creo rider who posts on another site who moved from a creo 1 to a creo 2 and found he had to significantly detune the creo 2 to prevent it from drastically dropping motor power due to its built in heat protection logic. As I recall he rides in fast, long group rides and used the creo 1 at 100% turbo mode. His creo 2 would drop power in half several miles into a ride, leading him to detune it to something like 75% max power in order to sustain its output. I think his solution gave him an improvement over his Creo 1 but not nearly as much as he hoped for. He’s the ebike expert in a specialized store so I think his experience is a very credible one.

I’m familiar with Ed’s posts. I am not sure that his use case - mid 20mph speeds for an hour or two with <100w rider power - are really very indicative of what almost anyone else would experience on a creo, 1 or 2. really nice guy, but some of his claims about aerodynamics, the relationship of speed and various components on the bike, are kind of absurd.

we know that the 2.3 (vs 1.8) multiplier of the creo 2 will result in more power consumption for a given assist ratio and rider power, along with higher speed. higher speed = less range, often dramatically so. none of this should be surprising, and I have yet to hear anything about thermal throttling from anyone else.…

 

[Allan47.7339]

Ye

I would say the firmware would not have matched in the first place. Creo 2 batteries are "flashed" with the new firmware to retain the compatibility. What about the TCU firmware? Is it the same on Creo 2 and Vado SL 1?

You need to change the motor with the matching Mastermind TCU. I've been told you don't need to swap the battery but it's so easy to do at the same time and keep everything together.

 

[Jeremy McCreary]

we know that the 2.3 (vs 1.8) multiplier of the creo 2 will result in more power consumption for a given assist ratio and rider power, along with higher speed. higher speed = less range, often dramatically so. none of this should be surprising, and I have yet to hear anything about thermal throttling from anyone else.…

In this model, all 3 bikes held the same speed — 20 mph on the flat dash, and 8 mph on the climb. With this restriction, the Creo 2 used less battery (fewer Wh) than the stock SL on the fast dash but the same or more on the much slower climb. The Creo's more aerodynamic rider posture on the drops had a lot to do with this result.

Which brings up a question for you: Based on data in Wilson & Schmidt, I gave the Creo a 19% discount in CdA for its less upright rider. (For anyone unfamiliar, air resistance is proportional to CdA, the drag area.)

These are all rough estimates, of course. Question is, does the Creo's posture discount sound reasonable to you?

 

[Stefan Mikes]

I've been told you don't need to swap the battery but it's so easy to do at the same time and keep everything together.

I've been told you need to update the firmware on the main battery and Range Extenders.

 

[Calcoaster]

I’m familiar with Ed’s posts. I am not sure that his use case - mid 20mph speeds for an hour or two with <100w rider power - are really very indicative of what almost anyone else would experience on a creo, 1 or 2. really nice guy, but some of his claims about aerodynamics, the relationship of speed and various components on the bike, are kind of absurd.

we know that the 2.3 (vs 1.8) multiplier of the creo 2 will result in more power consumption for a given assist ratio and rider power, along with higher speed. higher speed = less range, often dramatically so. none of this should be surprising, and I have yet to hear anything about thermal throttling from anyone else.…

Yes, more speed and higher assist ratio does make for higher power consumption. I know he determined that his Creo 2 motor needs to be held down to its nominal power rather than its peak power rating when used for extended rides. He said using 100/75 (assist level/max power) kept it from the thermal throttling he experienced.

I don’t think many lightweight road ebike riders ride full out for their whole ride. I never even used turbo mode on my Creo. And my BMC (with TQ motor) feels so natural at a lowered eco level I rarely use anything higher.

 

[mschwett]

Yes, more speed and higher assist ratio does make for higher power consumption. I know he determined that his Creo 2 motor needs to be held down to its nominal power rather than its peak power rating when used for extended rides. He said using 100/75 (assist level/max power) kept it from the thermal throttling he experienced.

I don’t think most lightweight road ebike riders ride full out for their whole ride. I never even used turbo mode on my Creo. And my BMC (with TQ motor) feels so natural at a lowered eco level I rarely use anything higher.

it’s fun to ride fast, no doubt, but when that last 100w only gets you 2mph…

i never used turbo either except for short stretches of very steep hills, and one time i bonked after not eating or drinking on an 80 mile ride.

 

[mschwett]

In this model, all 3 bikes held the same speed — 20 mph on the flat dash, and 8 mph on the climb. With this restriction, the Creo 2 used less battery (fewer Wh) than the stock SL on the fast dash but the same or more on the much slower climb. The Creo's more aerodynamic rider posture on the drops had a lot to do with this result.

Which brings up a question for you: Based on data in Wilson & Schmidt, I gave the Creo a 19% discount in CdA for its less upright rider. (For anyone unfamiliar, air resistance is proportional to CdA, the drag area.)

These are all rough estimates, of course. Question is, does the Creo's posture discount sound reasonable to you?

at 20mph i’d say 20% is about right for an aggressively fitted creo. i do see a lot of creos with tall spacer stacks, riser stems, and riser bars, which obviously all works against the theory.

with mission control’s power readout you can pretty easily simulate this, find a flat road and go 20 sitting straight up, see what the rider and motor power numbers look like… then put your hands on the top of the center of the bars, forearms flat behind, chin as close to your hands as you can. your hips will feel strange making power in that position but assuming you can keep it up for 30 seconds or more, you’ll see either an immediate increase in speed or a decrease in power.

 

[Jeremy McCreary]

You need to change the motor with the matching Mastermind TCU. I've been told you don't need to swap the battery but it's so easy to do at the same time and keep everything together.

Do know of anyone who's actually done this SL 1 mod successfully?

 

[Allan47.7339]

Do know of anyone who's actually done this SL 1 mod successfully?

Yes between Creo's. Vado SL 1 is the same motor mount, wiring etc as Creo's. It would make more sense to convert a Creo E5 to a flat bar.

 

[Jeremy McCreary]

Yes between Creo's. Vado SL 1 is the same motor mount, wiring etc as Creo's. It would make more sense to convert a Creo E5 to a flat bar.

The model can also simulate a flat-bar Creo 2 by making its drag area (CdA) the same as the SL 1 and assuming no net change in bike weight in the conversion.

When I do that with the Creo 2 Carbon Comp — the version graphed above — the yellow Creo bars become just a tiny bit shorter than the red bars of the modified SL in all 18 cases graphed. This reflects a gross weight advantage of only 2% for the carbon Creo with an 87.3 kg rider (me) onboard.

That tiny rider power and battery consumption advantage for the carbon Creo 2 would probably be lost with the alloy version, so just read the red bars to evaluate the suitability of a flat-bar alloy Creo 2 for your riding goals.

It bears repeating that the graphs above assume a full tuck on the drop-bar Creo 2. The more you sit up from there, the more the Creo's rider power and battery consumption advantages go away — at least in the 2 modeled scenarios.

 

[mschwett]

it's probably obvious from your work, but does the model take into account the huge difference in tires? something like a 47mm pathfinder has more than twice the rolling resistance at 18mph as a state of the art road bike tire. roughly 44 watts of RR vs 18 watts for a pair of tires (47mm pathfinder vs 28mm GP5000 S TR). and then there's the drag of the knobs, larger frontal area, etc. maybe not as significant as rider position at higher speeds but definitely significant.

 

[Jeremy McCreary]

it's probably obvious from your work, but does the model take into account the huge difference in tires? something like a 47mm pathfinder has more than twice the rolling resistance at 18mph as a state of the art road bike tire. roughly 44 watts of RR vs 18 watts for a pair of tires (47mm pathfinder vs 28mm GP5000 S TR). and then there's the drag of the knobs, larger frontal area, etc. maybe not as significant as rider position at higher speeds but definitely significant.

Taking full advantage of the Creo 2's clearance for 47 mm gravel tires would definitely come at a cost in both rider power requirements and battery consumption.

EDIT: Not so! See my next post.

But for the scenarios graphed above — and for lack of data to the contrary — I gave all 3 bikes the same lowish coefficient of rolling resistance (Crr) of 0.005. Not at all far-fetched, as a Creo 2 could easily run the 38 mm tubeless Pathfinder Pro hybrids on my stock SL.

However, I could just as easily give the Creo its own Crr — say, 0.010 for the 47 mm Pathfinder if 0.005 were correct for the 38 mm. I'll let you know what the model says when tire-related weight and air resistance changes are ignored.

EDIT: The 47s actually test at lower Crr than the 38s. See my next post.

Meanwhile, how did you calculate the power losses from the tire options you mentioned? I sense a learning opportunity here.

 

[mschwett]

...

Meanwhile, how did you calculate the power losses from the tire options you mentioned? I sense a learning opportunity here.

check out bicyclerollingresistance.com ! they have tests on rollers at 18mph for a zillion tires. the results wouldn't apply to rough/gravel/uneven surfaces but are a decent proxy for good california roads.

here are watts of resistance (at two diff pressures, to see more pressures you need to subscribe which is worth it just to read...) for 28mm GP5000 S TR and Pathfinder Pro 47mm per tire at 18mph. you will see a LOT of people claiming that gravel tires (with their solid center block) are "easy rolling" but the science says otherwise.

the very fastest tire they ever tested (the kind of thing that would flat if you looked at it funny) has 5.6 watts of resistance in 25mm at 18mph, and there are well-regarded 38mm gravel tires that are as much as 30 watts per tire. imagine that - 70 watts vs 11.2 watts difference, or the difference between having to pedal with 160 watts of power and almost 220 watts of power.

the disclaimer here is that on rough surfaces, a bigger tire at lower pressure will have less rolling resistance. so they are the right choice for, say, loose gravel, but not for pavement.