Reliability & drivetrain wear on 30mph, 350 mi/wk commute?

mystryda

10 W
Joined
Jul 11, 2017
Messages
69
Location
Germany
Background:
--I currently commute 70 miles per week, year-round on a CAAD4 and I average ~21-23 mph (leg power, including traffic, stop and go, etc.--topping out in the high 30's, climbing in the high teens.) The calculators that I've looked up show my average output as around 300-350W, which seems in line with what I've read.
--I just got a new assignment that's 25 miles away, and I'd like to build an electric bike to help me make this commute in an hour. To account for traffic, I figure that I need to average 30 mph to make that happen. Calculators show that I need around 700W to achieve this, or less than 400-500W average additional power. I plan on cruising in a 53/11 in the flats at 100-110 rpm. I realize that these speeds on a road bike may make some folks nervous, but to me it's just more of the same.


Will reliability and drivetrain wear be a problem with 700W+ coming from a mid-drive (BBS02) 10 hours, 250 miles a week? This will be how I get to work day in, day out, so I need it to be a workhorse. Should I consider a hub motor instead?
 
The chain and 11 tooth sprocket will wear quickly, and you have no redundancy if anything fails in the sprocket/chain subsystem. Many people who put lots of miles on mid drives try to avoid using the smaller sprockets due to high tooth loading and rapid wear.

Direct drive hubmotors are extremely simple and hardy, and provide a mostly redundant drivetrain.

If I were doing what you are planning I would have at minimum two bikes capable of making the commute, and the primary would be a DD hubmotor type. The backup could be something different, but needs to meet at least the nominal requirements for the commute to perform in the backup role.
 
I’m not following you.

How far is your current commute?

Are you talking cruising speed, or average speed? 22mph average speed is not really possible with leg power (unless you are making a living off of cycling). Should I assume you are talking cruising speed? Average speed is typically ~4-5 mph slower than cruising speed.

Same with power – 350 is world class for an average. Even being able to sustain that is extreme. High 30’s in the flats isn’t realistic.

For example, Last night I did a ride with some of the fastest guys in the state. Pushing it to the limit – 300watts, 25mph cruising speed in a pace line. Average speed was 21mph.

So, assuming you are talking cruising speed or peak, and not average speed.

53x14 will get you 30mph. that should work better than using an 11 tooth cog. With your strong legs, a hub motor will be more reliable if you don’t have some serious hills. You just need to avoid using full throttle for sustained time at below 50% of maximum speed.

I’ve done what you are describing, but my cruising speed on the ebike is 25mph. Ya don’t need direct drive – a geared hub motor will work fine.

Keep in mind that the power of the motor falls off sharply the more power you put out with your legs. It’s a bit of a wash there. The problem is that the wind resistance is also increasing exponentially, so it is hard to add to the top speed of a motor at those cruising speeds.

I’m not sure how you are going to feel about adding 25lbs for a motor and battery to your bike. 700 watts is riding in the drops at those speeds.
 

Attachments

  • 25mph paceline metrics.JPG
    25mph paceline metrics.JPG
    23.1 KB · Views: 2,468
An 11t sprocket is something you can use for an occasional burst of speed, not for routine riding. If you use it often, you'll quickly wear out the chain, which will in turn wear out every other sprocket you use it with.

If you go at moped speed every day, a direct drive hub motor is a better choice for you. It will result in a bicycle that is very unpleasant to ride without motor power, but it's the right way to go for riding at speeds a normal bicycle never maintains for very long at a time. A geared hub motor that's rated for 750W or more (I think that means only the MAC) is a more ridable alternative, but noisier, with more wear parts and points of failure. For 50+ miles every working day, I'd definitely be looking to maximize reliability.

If you want to use an electric bicycle that feels and rides like a bicycle, and do it routinely and reliably, you'll need to keep the speed and power relatively modest and the drive chain forces within the range of normal. That means developing the power required for high road speed by using high chain speed, rather than just using higher chain force than is humanly possible to maintain. You can get higher chain speed either by pedaling faster, or by using a larger chainring, or both.

A hub motor bypasses all the pedal drive components to deliver power to the rear tire directly, with reaction forces fed into the frame. That makes it less destructive to the bicycle's moving parts when your usual speed is higher than muscle power allows.
 
chas58 said:
How far is your current commute?
6.5 miles.

chas58 said:
Are you talking cruising speed, or average speed? 22mph average speed is not really possible with leg power (unless you are making a living off of cycling). Should I assume you are talking cruising speed? Average speed is typically ~4-5 mph slower than cruising speed.
I'm talking about average speed. Today I averaged 21 and topped out at 37. My best average on this route is 24.7mph.

But keep in mind that we're only talking about a 15 minute ride, not 60 mile club rides. It's a sprint. I'm only planning on sustaining 200-250W day-in, day-out for the much longer commute than I'll be starting this fall.

chas58 said:
The problem is that the wind resistance is also increasing exponentially, so it is hard to add to the top speed of a motor at those cruising speeds.

I’m not sure how you are going to feel about adding 25lbs for a motor and battery to your bike. 700 watts is riding in the drops at those speeds.
Yep, drag increasing with cubes of speed is a "drag." I'm already accustomed to staying in the drops, but I'm also considering adding a small fairing (Zzipper), which would especially ease the colder months.

chas58 said:
I’ve done what you are describing, but my cruising speed on the ebike is 25mph. Ya don’t need direct drive – a geared hub motor will work fine.
Can I be curious what geared hub motor you're using? From what I've found so far only the MAC in 6T or maybe 8T can get up to 30 mph, but I'm also assuming that the numbers that I'm finding are "loaded" numbers with somebody sitting up and not pedaling, vs me in a tuck and adding a couple hundred watts.
 
Chalo said:
If you go at moped speed every day, a direct drive hub motor is a better choice for you. It will result in a bicycle that is very unpleasant to ride without motor power, but it's the right way to go for riding at speeds a normal bicycle never maintains for very long at a time. A geared hub motor that's rated for 750W or more (I think that means only the MAC) is a more ridable alternative, but noisier, with more wear parts and points of failure. For 50+ miles every working day, I'd definitely be looking to maximize reliability.
Do you have any suggestions of specific direct drive hubs?

Chalo said:
A hub motor bypasses all the pedal drive components to deliver power to the rear tire directly, with reaction forces fed into the frame. That makes it less destructive to the bicycle's moving parts when your usual speed is higher than muscle power allows.
Right. This was my concern. Thank you all for addressing it.
 
Ok, that makes sense. I can hammer pretty hard for 15 minutes. ;)

I use a small Q100 with a high speed winding (see my signature for my builds). The motor has only enough power (at 36v) for 20mph (~350 watts), and has a no load speed of 30 mph.
My e-bike cruising speed is 25mph: it puts out 300 watts, I need about 500 watts, and I put out about 200-300 watts through my legs.
For a 24 mile commute, I average about 15-16 mph pedaling only (probably 18mph cruising speed) and that takes me about 93 minutes.
On the ebike, I average about 21mph (about 25 mph cruising speed) and that take me about 67 minutes.

If you are analytical/engineering – the simulator can answer most all of your questions.
http://www.ebikes.ca/tools/simulator.html
you can play with different bike configurations, hills, throttle, voltage, current, and see how far/fast you will go, when you will overheat, what your loading will be, how fast the power drop off is as you increase speed...

You don’t sound like a direct drive kind of guy (it is much heavier, and has drag when not powered). A smallish geared hub should do fine – like one of these MAC motors you mentioned:
https://em3ev.com/shop/?product_cat=hub-motor-kits-motors

Like you alluded to – most of the numbers you see are for a mountain bike style riding – and at 30mph on a mountain bike – the average person’s pedaling isn’t going to affect speed much. 30mph is going to take 1000 watts. If you have good tires and an aerodynamic position you will only need ~700 watts
(There is a video out there of someone doing 45kph with a small ~350watt motor on a recumbent, if you really want to get aero…)
 
I'm wondering if anyone has any experience with the Sram EX1 group set yet? Been thinking about picking it up for a while now. It's definitely a bit pricey which is why i haven't pulled the trigger just yet... I know this thread is on the side of road bikes but still falls under the "reliability & drivetrain" categories :)

https://www.sram.com/sram/mountain/family/ex1

Edit: or maybe to save money pairing it with a SunRace CSM680 cassette. All steel and would knock $360 off...
 
Warren said:
An 11 tooth, on a mid-drive, is pretty foolish...unless you are selling cassettes. :)

Why is that, just chain wear due to lack of teeth on the 11t?

I've been running my 11-42t SunRace 10s cassette with a KMC DLC chain (overkill, i know) for over a year now and I get into the 11t at least once or twice per ride (probably more). I also use an XTR hub which comes with a Ti freehub body, so far so good. I'll just keep my fingers crossed i guess :shock:
 
11t sprockets have less positive engagement, on fewer teeth, with more articulation per link than larger sprockets. All of these factors result in accelerated wear. With a mid drive, the chain is also under much more tension for more of the time than with a pedal-only drive, and there's a tendency to use the top gear much of the time (when one of the reasons 11t works for pedal bikes is because it's rarely used).
 
Thank you for clarifying! Damn, i love this forum! You guys rock...

What might be the first signs of accelerated wear on the sprockets/chain? Shifting problems? Chain skips? Usually when i'm in the 11t i'm not using more that 15-20A as it's just to maintain speed with a smaller noise footprint.
 
m4k3r said:
What might be the first signs of accelerated wear on the sprockets/chain?

Skipping under heavy load on the most commonly used gears. By that point, most of the damage is done, though. The thing to do is get a chain checker and use it to detect chain wear early enough that you can swap the chain and eke some more life out of the sprockets.

If you swap to a new chain when the old one measures 0.5 percent longer than it started, you can usually reuse the old cassette at least once, sometimes twice.

Shifting among all your gears rather than just one or two most-used ones is a good habit for maximizing component longevity.
 
Chalo said:
If you swap to a new chain when the old one measures 0.5 percent longer than it started, you can usually reuse the old cassette at least once, sometimes twice.

Shifting among all your gears rather than just one or two most-used ones is a good habit for maximizing component longevity.

Awesome, thanks for the tip! I definitely shift between all the gears and only get into the 11t a couple times during a ride. After a year everything still feels like butter and i guess the old tape measure trick might not suffice for checking the chain anymore (exactly 12" pin-to-pin). Time to finally invest in a chain checker tool.
 
cwah said:
Dd mandatory, your bbs will die within few months

I disagree with this. I have 10,000 miles combined (and counting) on three Cyclone 3000W builds, one is a mid-drive C3000W eTrike, with 7000 miles on the clock and 1 1/2 years old now, weighing in at 100lbs, and running 6.5 kW @ 30 mph average speeds commutes with bursts of nearly 60mph... Never had to replace a single BB, still running the original crank freewheel I installed at around the 350 mile mark on the clock (White Industries UHD crank freewheel). On my 2nd chain now.

If you want a mid drive that is reliable and gets 6+ k miles per 10-speed chain then you need to run a high RPM drivetrain, which makes human pedaling impossible, so you'll just be dummy pedaling the bike along. The crank on both my trikes spin at very high RPM, b/c I need that kind of rpm to keep the torque low to achieve the same amount of power without bending stuff, chewing cogs and breaking chains: I am always running either the 42T, 36T or 32T cogs on a 10speed cassette, thus the chain lasts forever.

G.
 
gman1971 said:
cwah said:
Dd mandatory, your bbs will die within few months
I disagree with this. I have 10,000 miles combined (and counting) on three Cyclone 3000W builds, one is a mid-drive C3000W eTrike, with 7000 miles on the clock and 1 1/2 years old now, weighing in at 100lbs, and running 6.5 kW @ 30 mph average speeds commutes with bursts of nearly 60mph... Never had to replace a single BB, still running the original crank freewheel I installed at around the 350 mile mark on the clock (White Industries UHD crank freewheel). On my 2nd chain now.
G.
I think he meant BBS02 mid-drive OP mentioned.
 
silence said:
gman1971 said:
cwah said:
Dd mandatory, your bbs will die within few months
I disagree with this. I have 10,000 miles combined (and counting) on three Cyclone 3000W builds, one is a mid-drive C3000W eTrike, with 7000 miles on the clock and 1 1/2 years old now, weighing in at 100lbs, and running 6.5 kW @ 30 mph average speeds commutes with bursts of nearly 60mph... Never had to replace a single BB, still running the original crank freewheel I installed at around the 350 mile mark on the clock (White Industries UHD crank freewheel). On my 2nd chain now.
G.
I think he meant BBS02 mid-drive OP mentioned.

Good point. Thanks.

However, you could still use a larger chainring, a 52T or larger like that will get you out of the smaller cogs at high speed... :)

G.
 
Hi, I can just talk about my own experiences.

I am commuting to work in Sweden, whole year round, only stopping if we have snow. So far I have done 3000 km in 6 months. I have 10km single trip every day.

I use an older Scott sub 40, a hybrid type of bike, at 48V with a 700c wheel, running my mac 10t at 20A I get around 42km/h with no pedaling. I get even 50 km/h with headwind

The controller is caped at 900W and it is more power than I ever need.

If I would go with an 8t or even 6t winding on the mac I would top out at 60km/h I would guess.

You can see my build here: https://endless-sphere.com/forums/viewtopic.php?f=6&t=85512

I have no issues with chain or gearing, during autumn and winter I clean my bike once very weak, wash and re lubricate, during summer I just re lubricate every week and wash when needed.

Before this build I was using a direct drive 500W rear hub, it was heavy, added drag and was worse for ridding hills, so only thing it added was regen and a little higher efficiency.

If you are choosing between DD or a geared hub motor I would go with the geared, the mac motor I have is so far doing great and I think if I dont push it past 1500W it will continue to do so for a long time.

Just a last remark, when I was ordering there was only one rim available for 700c the alex dm24, that is a very vide rim that needs a 42+ wheel on it. Just something to consider.

I am running "normal" parts, deore for most parts and chain is a KMC x9-93, I dont go more high end than that and the parts last a long time. I hope you got some answers and some ideas on where to go.
 
pomah said:
The controller is caped at 900W and it is more power than I ever need.

If I would go with an 8t or even 6t winding on the mac I would top out at 60km/h I would guess

No. The motor would try to push that fast, but it wouldn't have the power to do it. So it would make extra heat instead.

Am average person on an average bike requires 1kW at the wheel to maintain 48 kph.

The bottom line is that you got exactly the right winding for your application; the power available is well-matched to the load at speed.
 
Well i decided to pull the trigger on a new drivetrain. Went with the Sram X.4 shifter and derailleur, SunRace 11-40t 8-speed cassette (all steel) and KMC Z-72 8sp chain. Grand total of $94.10 and will be here in a couple days. My current setup didn't "need" to be replaced, I just wanted to shift less with a beefier setup, this seems to be a good choice for the price!
 
Back
Top