Is the theory right about the differences in tires between my bikes?

fooferdoggie

Well-Known Member
ok I started with my bulls bike with a bosch performance speed motor second gen 63nm of torque. I rode it a ton and got a a feel for how the speed verses How many watts I put out works.


then we get the e tandem that uses a bosch performance motor not a speed but same torque


well I always felt I was working as hard on the tandem but my watts output and my heart rate were always lower. but it felt like I was putting the same effort into it.


then comes the trek when the motor goes out on my bulls. it has the 4 gen performance speed motor with 85nm of torque. weight is about the same as my bulls within a pound or so. but for what feels like the same power output I am slower and doing less watts.


on my bulls right now I could average 145 watts on my commute and my heart rate will vary but this time it was 118 average. my average speed was 16.8mph


on my trek it was 15.6mph but on,ly a average of 132 watts. that's about the ma I have managed on the trek. its often slower


I tend to only get around 18mph on the trek but around 20 to 22 on the bulls.


I think this is all do to the bulls with the 1.5" marathon tires at 70 psi verses the trek with 2.5" tires at 50 psi


I cant go by speed on the tandem as its ma on the flat for us is 18.5 right at the motor cutoff. but I am lucky to average 110 watts average. I got 130 watts once but that was a ton of hill climbing. I have peaked at 450 watts going up steep hills on all three bikes,. my bulls I have done 600 to 700 watts peak on short sprints. the trek just wont accelerate fast enough.


so on my bulls it feels like I am working the same but my watts are higher sometimes by a lot. my HR is higher too but it feels the same. this seems like the whole cadence thing where 400 watts peddling at 80 rpms cadence is easier then doing the same at 30 rpms cadence.
 

fooferdoggie

Well-Known Member
I suggest smoking the marijuanas before riding each and see if you still care. 🙃
Your heart rate should be better as well.
riding is fun. this is just an observation. actually my heartrate is higher then it used to be. I used to ahve to average 170 watts to get it to 130 average/ but I am riding in the city so its so up and down. average speed and heart rate suck on city roads. but I have tested this on the same bike path over and over. but on my bulls going that 20 to 22 eats the battery faster then the trek.
I just need to ride by certain houses to get high.
 

mclewis1

Well-Known Member
Region
Canada
City
Fredericton, NB
I think the difference in cadence maybe a bigger deal than you think. Plus are the crank arms the same length? Next up would be differences in efficiency in the motors themselves (vs. the BS torque numbers). Only after all that would I consider the difference in the tires affecting things.

I've got two similar bikes with that same tire difference (38mm at 70psi vs. 55mm at about 35psi) and despite the 55mm tires being heavier I don't notice a dramatic difference in efficiency, but they sure feel different. The bikes have the same motor and control system, and I use the same battery shared between them. There's about 10-15lbs difference in total weight but what seems to make the biggest difference between the two is the gearing ... I have much higher (more gear inches) available on the one with narrower tires and I'm capable of sustaining almost 20% higher speeds over 2-3hrs. When ridden at the same/similar speeds the efficiency difference (in Wh/km) is less than 5%.
 

fooferdoggie

Well-Known Member
I think the difference in cadence maybe a bigger deal than you think. Plus are the crank arms the same length? Next up would be differences in efficiency in the motors themselves (vs. the BS torque numbers). Only after all that would I consider the difference in the tires affecting things.

I've got two similar bikes with that same tire difference (38mm at 70psi vs. 55mm at about 35psi) and despite the 55mm tires being heavier I don't notice a dramatic difference in efficiency, but they sure feel different. The bikes have the same motor and control system, and I use the same battery shared between them. There's about 10-15lbs difference in total weight but what seems to make the biggest difference between the two is the gearing ... I have much higher (more gear inches) available on the one with narrower tires and I'm capable of sustaining almost 20% higher speeds over 2-3hrs. When ridden at the same/similar speeds the efficiency difference (in Wh/km) is less than 5%.
I use the same cadence while riding for all my bikes they all have the same length crank arms even the same seat and about as close as I can the same sitting position. Bosch is pretty consistent on their motors and if anything underrated. but the two regular bikes feel very consistent and the new motor on my bulls feels the same as the old one did. both regular bikes use the same display too it changes over. the thing is with the bulls I have to turn down the assistance on tour so I can keep my watts up or I would have to go faster. the trek needs the default (though I am going to try raising it to see if I can get it to feel more like the bulls) the gearing is the same on both too. the only real difference is the tires. with a little money I can put the wheels on my bulls on the trek and really test it but I don't know if I want to go to the effort.
but the bulls is far more zippy then the trek is even though the motor is not as powerful. its a big difference. once I raise the power at the low end of the speed on the trek it has helped a lot. but I had to raise it a lot to get it close to the bulls.
 

fooferdoggie

Well-Known Member
though the measure 2.75 or so
Bontrager E6 Hard-Case Lite, reflective, wire bead, 60tpi, 27.5x2.4"
@fooferdoggie how are you measuring your power output? there are a lot of variables and vagaries here!
using the nyon to measure it so it should be pretty consistent. plus I have ridden the bulls and tandem a lot the bulls over 14,000 miles in 2.5 years and the tandem 6000 in 2 years. I only have a month or so on the trek.
if I wanted to spend a little money I can put the bulls's wheel on the trek. but the bulls has the center lock discs and the trek has 6 bolts and the magnet mounted to the disc. so I would have to glue a magnet onto the back wheel to make it work. but I jsut did 175 watt average coming home no way I can even get close with the trek without raising the power levels.
 

mschwett

Well-Known Member
Region
USA
though the measure 2.75 or so
Bontrager E6 Hard-Case Lite, reflective, wire bead, 60tpi, 27.5x2.4"

using the nyon to measure it so it should be pretty consistent. plus I have ridden the bulls and tandem a lot the bulls over 14,000 miles in 2.5 years and the tandem 6000 in 2 years. I only have a month or so on the trek.
if I wanted to spend a little money I can put the bulls's wheel on the trek. but the bulls has the center lock discs and the trek has 6 bolts and the magnet mounted to the disc. so I would have to glue a magnet onto the back wheel to make it work. but I jsut did 175 watt average coming home no way I can even get close with the trek without raising the power levels.
wellllll… the nyon displays your power output, but how is it measured? the power “meters” that are part of mid-drive motors aren’t super accurate depending on a bunch of factors. and how accurately is the motor power output measured? torque is pretty much meaningless by itself - it has to be combined with speed to determine power, and the chainring on a mid-drive is disconnected from the cranks. do you have some data which shows how much power the motor is using and outputting over these same ride stretches?

tires makes a difference, but at the speeds you’re talking about aerodynamics are a bigger difference, although the aerodynamics of the tires are a part of the aerodynamics lol.

if you’re putting out 150w and going 20mph, you’re getting around another 175w from the motor assuming a fairly average MTB tire and an upright-ish position. the far extreme from there with the same 325w power, race road tires and a very aero position is only good for 25mph. the difference between the tires you’re describing will be only a fraction of that. according to bikeCalc the difference between MTB tires and tubulars is 2mph at that speed and profile, so maybe the difference you might see is 1mph. something else is making a big difference and i’d guess it’s the motor output. should be easy to verify, log some rides on flat ground (both directions to cancel wind) with the various bikes and chart motor watts vs rider watts vs speed….
 

fooferdoggie

Well-Known Member
I don't expect the exact watt number the bosch is showing me to be exact but I expect it to be consistent. otherwise the bike would not ride well. only the old nyon shows how many watts per mile the motor is using.
but I am slower on the trek and I am in the same position I set it up with the same reach as the bulls. its not wind acceleration on the trek is much less then on the bulls. the trek has the 4 gen bosch motor with 23 nm more torque so it should accelerate better. I may be able to mount the marathon tires onto the trek and really test it. but I ahve seen 2mph drag with less difference in tire diameter on my coasting test on my recumbent with a fairing. I would do the same hill over and over.
the trek is in the shop getting the second battery holder mounted the first commute on the trek and it felt like I should have averaged around 130 watts as I was only feeling ok. but when I looked it was less then 100 watts and the calorie count was less then 200 calories when it is usually 240 to 250 calories.
I get more distance out of the trek battery because I am slower. the difference between 10 and 22mph is a fair mount on battery usage.
 

mschwett

Well-Known Member
Region
USA
again, torque is meaningless without speed. you need to know how much power the trek and bulls are putting down to know whether your difference in speed is based on 1) your own contribution varying or 2) the aerodynamics/rolling resistance of the bikes or 3) the motor contribution. absolutely no way to know without somewhat definitively knowing what the motor is doing. you could have a 200nm motor and if it’s configured to use 100w, it will only speed you up a certain amount. if the nyon won’t tell you this, ride long enough to deplete the batteries a measurable amount (50% would be good) and back out the wattage from there.

your last statement at least suggests the answer. you’re getting more mileage on the trek, which means it’s using less power per mile (doesn’t matter what the peak torque is!), causing you to go slower. higher speeds use more power but more power causes higher speeds ;)
 

fooferdoggie

Well-Known Member
again, torque is meaningless without speed. you need to know how much power the trek and bulls are putting down to know whether your difference in speed is based on 1) your own contribution varying or 2) the aerodynamics/rolling resistance of the bikes or 3) the motor contribution. absolutely no way to know without somewhat definitively knowing what the motor is doing. you could have a 200nm motor and if it’s configured to use 100w, it will only speed you up a certain amount. if the nyon won’t tell you this, ride long enough to deplete the batteries a measurable amount (50% would be good) and back out the wattage from there.

your last statement at least suggests the answer. you’re getting more mileage on the trek, which means it’s using less power per mile (doesn’t matter what the peak torque is!), causing you to go slower. higher speeds use more power but more power causes higher speeds ;)
but I am also going slower.I never go 18mph on the bulls. but it seems it takes the same effort as it takes to go 20 to 22 mph on the bulls. it feels like I am working less on the bulls even though my watts are higher and my heart rate is higher. it feels like I am working as hard on the trek and the tandem but I am putting out less watts and my heart rate is lower. I think its about feel. the bulls accelerates faster it feels faster than the trek and the tandem. I have noticed if I am not feeling great I crank up the assist level I don't feel like its as much work even though my watt output is a bit higher. thats why I think its the tires for the trek and the weight on the tandem because they feel slower. so it fools my body into thinking I am working as hard.
 

Stefan Mikes

Well-Known Member
Region
Europe
City
Brwinów (PL)
@fooferdoggie: Not getting into details related to your specific e-bikes and trips you are taking: Yes, the rolling resistance of tyres affects both the battery use and your effort, and can slow an e-bike dramatically down. I was using all-round tyres on my two e-bikes. My speed Vado had issues to ride faster than 20 mph with reasonable battery use; replacing the tyres with ones of very low rolling resistance brought me at the level of 24 mph instantly. For my Vado SL, I struggled below 15 mph on the all-rounders. Swapping the tyres for low rolling resistance ones brought me to 17-18 mph without any changes to assistance levels.

Yes, the tyre type, brand and model really matters. There is the site:

It lists many tyres, giving the number of watts given tyres "eat" at given inflation pressure. For some types of tyres, especially MTB and fat ones, the consumption of watts is tremendous.
 

fooferdoggie

Well-Known Member
I spent a week back on my bulls while the extra battery hardware was added to my trek. Man the acceleration on my bulls is far better then the trek. I mean its pretty dramatic. even with treks 24nm more torque. I think the thing is it does nto accelerate as fast so getting upto 600 watts on my part takes longer and I run out of steam faster. I need to ride more but it seems to take about 3 peddle strokes before I need to shift where on my bulls it may only be 1 peddle stroke. I think its just the big tires slowing it down. like I have been doing 155 what average on my bulls but I got a record 139 on the trek. but its a lower heart rate too so I donor burn as many calories. overall it may be better now that we are riding on the tandem more so I wont get as worn out.
 

Stefan Mikes

Well-Known Member
Region
Europe
City
Brwinów (PL)
I spent a week back on my bulls while the extra battery hardware was added to my trek. Man the acceleration on my bulls is far better then the trek. I mean its pretty dramatic. even with treks 24nm more torque. I think the thing is it does nto accelerate as fast so getting upto 600 watts on my part takes longer and I run out of steam faster. I need to ride more but it seems to take about 3 peddle strokes before I need to shift where on my bulls it may only be 1 peddle stroke. I think its just the big tires slowing it down. like I have been doing 155 what average on my bulls but I got a record 139 on the trek. but its a lower heart rate too so I donor burn as many calories. overall it may be better now that we are riding on the tandem more so I wont get as worn out.
Any difference in the chainring size for both e-bikes? Just asking.

I had a chance to ride a Giant Trance E+ 2 Pro with a 38T chainring and 27.5 x 2.6" aggressive knobby tyres on a long group ride involving both pavement and off-road. While the e-MTB shone off-road, it was very hard to pedal that e-bike on the pavement, even with the 80 Nm motor. I was always in the tail of the group on-road, and returned from a 95 km ride exhausted. While a similar ride on Vado 5.0 (42T, 90 Nm, fast rolling 2" tyres) would be a pleasure for me. I would even have taken a risk of riding a Vado SL (44T, 35 Nm, extremely fast rolling 38 mm tyres) with that group if I used Range Extenders and high assistance levels (Vado SL is half power of the other e-bikes I mentioned).