The biggest problem at 25mph+ is rarely discussed resistance

General Discussion about electric bicycles.
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The biggest problem at 25mph+ is rarely discussed resistance

Post by cycleops612 » Apr 24, 2016 8:59 am

Or so it seems?

So many want more range and speed, but seek answers ~only in more power and weight.

Fairings, lycra, aerodynamic panniers, bigger wheels ... seem treated as minor issues with ebikes, when in fact it is the biggest issue at approaching car type speeds, and increases exponentially beyond a certain point. Then there are days you face a headwind.

Anyhoo, preamble aside, a heretical? suggestion which one would think may suit many who want fast and range, is a simple traditional (post mig welding manufacture seems wise?) road bike with drop bars, 28" racing wheels & tyres ? and a simple front hub motor.

I often had a total load of 100kg (i am 75kg) on my 12.5kg chromoly? racing bike. Never was grip an issue with so little weight.

If you have a long commute, there is the option of; cheap, light, slippery, more effective pedal input, and smaller/lighter/cheaper battery.

Drop bars can seem intimidating, but you get used to the two hand positions. A thumb throttle sounds best to be reachable from either.

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Re: The biggest problem at 25mph+ is rarely discussed resist

Post by gogo » Apr 24, 2016 9:39 am

There are several threads on aerodynamics and the windspeed/power relationship is mentioned frequently here on E-S. Here's a tool that puts numbers to the options: http://www.kreuzotter.de/english/espeed.htm

Fighting headwinds is an interesting topic to me because unlike high ground speeds, it doesn't require a heavy-duty bicycle. Dogman is always quick to point out the need for a headwind allowance in battery capacity calculations.
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Re: The biggest problem at 25mph+ is rarely discussed resist

Post by spinningmagnets » Apr 24, 2016 9:49 am

There were a lot of discussions around 2009 about this. Google:

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Re: The biggest problem at 25mph+ is rarely discussed resist

Post by cycleops612 » Apr 24, 2016 10:33 am

Quite, but technicalities aside and conceding it was discussed in 2009 (i will google it tho :)), we can agree its a big problem that is neglected i hope.

I like cheap ebikes cos its the poor who need them most. cars are not an option for them. mobility is a pre-requisite for a job. Its literally life threatening to be that broke and helpless.

What i propose can be made from ~junk, yet be effective commuting transport.

Consider this twist. By going minimalist, to say 250w 24v, the discards of others upgrading their power, can provide good service - a tired, used 36v bottle battery e.g. would probably work fine and be quite zippy.

One of you two responders was from tornado alley somewhere as i recall. I imagine headwinds there could really spoil your commute. Very relevant.

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Re: The biggest problem at 25mph+ is rarely discussed resist

Post by MadRhino » Apr 24, 2016 12:02 pm

I have made compromises for better aero with my street bike, lower bike with better aero posture made it faster, but I wouldn't go into smaller tires. I have built lighter wheels but still riding 3" low PSI tires, for high speed does require road grip and efficiency comes far behind skin and bones. :wink:
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Re: The biggest problem at 25mph+ is rarely discussed resist

Post by Chalo » Apr 24, 2016 12:39 pm

The easy things you can do to reduce aerodynamic drag all decrease comfort substantially. The more elaborate things you can do all make the bike heavier, more fragile, more expensive in time and money, and a heck of a lot more difficult to live with day to day.

My favorite solution is not to go fast enough for drag to be a big problem. Because it's not just aero drag you get at higher speeds; it's also unpleasant noise, stress, and risk of serious injury.

Even the fastest cars and motorcycles average about 10mph point-to-point in the central city. Ride a 20mph e-bike and you can get door to door faster most of the time.
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Re: The biggest problem at 25mph+ is rarely discussed resist

Post by cycleops612 » Apr 24, 2016 5:01 pm

I agree Chalo, when you consider the benefits you are getting with an ebike, you are still way in front at leisurely speed, as i do.

Dogman said elsewhere, at speed, you are focussed on spotting the next debris or whatever hazard on the road ahead. Take a chill pill and enjoy the surroundings. Similarly, I find weaving a bit to follow the smoothest roadway path helps smoothness a lot.

I feel for outer urban, rural and semi rural folk tho, with their greater distances, not just for work.

I take your point on tyres and wheels, just saying, they are stronger than you think and worked well for me for years humping 100kg.

Racing valves and I never seemed to get on anyway, but they do make sense - the larger valve hole must weaken the rim a lot - i.e. require a much heavier rim for equal strength.

Desireable as options may be, for many, the cash just isnt there for the power needed to effectively commute 20-25 miles using conventional ebike wisdom. As we know, it snowballs. The heavier and more powerful it gets, the heavier and more powerful it needs to be.

Its not just speed per se, its making full use of gravity momentum also. On downhill runs, wind and tyre resistance act as a brake.

I am just saying, its usually constructive to question conventional wisdom, even if you decide to conform in the end.

We agree about moderate speed, but we also know many give it undue priority. Its a legacy we are stuck with from Detroit's marketing, and a congenital primitive instinct to race and have the fastest steed thats imprinted on we mens brains, but petrol is a very different paradigm, so get over it - grow up :)

If you can effortlessly transport yourself at least 3x faster than you could possibly run for only a few minutes, and do that for over an hour, for ~zero $ per mile, thats pretty good, right? Be happy with that America.

Despite 700w+ being legal, I think it a mistake not to lean more to the euro minimalist model. For me, when a bicycle is un-heftable, its no longer a bicycle. Its a motorbike that has to be wheeled everywhere. 30kg all up would be my max.

If my 12.5kg pedal roadbike is ok for a 100kg gross weight, then why not an 80kg guy with 6kg of battery and motor on the 12kg bike? The max speeds are also the same, whether pedal or powered, given wind is the limiter, and the limit can be reached by either means. Why does the ebike need to be different? I think most could pedal out 250 watts of power, briefly anyway, so no real overtaxing of the intended bike limits need occur to spokes etc.

For example brakes. Most would scoff at calliper brakes on an ebike. Well yes, because ebikes are heavy. But this rig isnt heavy, its within the design max load spec, so well maintained, good calliper brakes should be fine.

I am not at all convinced by shocks and they add over 1kg. Smoothness from steel frame and bigger wheels ~compensate for going without.

I stress, just saying, but it sure seemed a big factor in the effortless rolling of my racing bike was those thin, rock hard, 120 psi tyres. I never had a traction problem in many years of using it as my only transport. If you are sensible, they should be safe on reasonable roads at appropriate speeds.

My only grief was the road morons who placed a drain grill with the slots parallel to traffic flow. My thin front wheel disappeared up to the axle in it. I was ok, but really .... Tax payers must constantly foot the bills for compensation claims for such surreal, negligent stupidity.

My educated guess is the worst of the commute is where you are forced to share with speeding cars. Here, a low power and resistance bike is pretty equal to a big powerful one once up to speed on the level, or decline, since its the wind which creates a practical speed ceiling. It takes a lot of power to compensate for the drop bar bikes wind and tyre advantage.

:) I am surprised folk dont improvise fairings more. Surely a large plastic salad bowl strapped to our chests would help? Jousting type body armour for limbs, contrived from slippery used pop bottles? A kitchen tidy lid as a bike nose cone?

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Re: The biggest problem at 25mph+ is rarely discussed resist

Post by Raged » Apr 24, 2016 8:45 pm

cycleops612 wrote:
Anyhoo, preamble aside, a heretical? suggestion which one would think may suit many who want fast and range, is a simple traditional (post mig welding manufacture seems wise?) road bike with drop bars, 28" racing wheels & tyres ? and a simple front hub motor.

I often had a total load of 100kg (i am 75kg) on my 12.5kg chromoly? racing bike. Never was grip an issue with so little weight.

If you have a long commute, there is the option of; cheap, light, slippery, more effective pedal input, and smaller/lighter/cheaper battery.

Drop bars can seem intimidating, but you get used to the two hand positions. A thumb throttle sounds best to be reachable from either.
You've pretty much described by BBS02 Cyclocross.... 29er frame, carbon fork, disc brakes, dropbars with 9 speed STI shifters and 28 or 29er tires ( depending on how I feel). I run a small pack by ES standards ( 5800mAh of 14S1P ) with a total bike weight of 19kg so I can lift it up over logs and carry it on my shoulder if I'm in a pinch. I am however a fairly fat bastard at 95kg.

On your thoughts about thin tires, If you're on a perfect road in race conditions, yeah sure thin tires are fine. On non-perfect roads, dodging doors, cars, debris, going through parklands/fields etc. you want balloon tires. I believe balloon tires do stop better in non-ideal conditions as well.

In regards to disc brakes vs vbrakes, The reason people use discs is not just braking capability ( although that does count a bit ), it's the fact that disc brakes are more reliable in wet conditions. Get a bit of dirt/mud/water on your vbrake and you're in trouble.
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Re: The biggest problem at 25mph+ is rarely discussed resist

Post by Alan B » Apr 24, 2016 8:49 pm

Reduce drag without a lot of clutter and complexity - recumbent bikes. Stop being perpendicular to the wind, or trying to lay forward and break your back while your legs are still perpendicular.

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Re: The biggest problem at 25mph+ is rarely discussed resist

Post by dogman dan » Apr 25, 2016 5:17 am

There is a reason bents are banned from UCI bike racing. Too aero. Start with a recumbent for the best results, then if you like, go for the fairing, tailbox, or even full velomobile.

As for riding really fast, in a city commute on a racing bike, see ya! Because they don't see you, and it's a lot harder to watch out for those suckers in a racing tuck.

I'm not saying aero is unimportant. It just is unimportant compared to survival, and unimportant compared to getting 1000 mpg vs 500 mpg equivalent. 500 mpg is still good enough for me.

They have been trying to kill me for 50 years now, and I have never ever allowed a car to hit me. I will confess though, I did hit a car once, when I was 18. That one entirely my fault, skidding a turn farther than I planned, I hit a parked car.

Whatever you build, if you ride in city traffic, have your head vertical, looking for the next left cross.

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Re: The biggest problem at 25mph+ is rarely discussed resist

Post by LewTwo » Apr 25, 2016 6:17 am

... or just add a mask, sail and tack into the headwind.
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Re: The biggest problem at 25mph+ is rarely discussed resist

Post by cycleops612 » Apr 25, 2016 11:04 am

LewTwo wrote:... or just add a mask, sail and tack into the headwind.
Argh.that be a poiret "mask"aye matey? :)

Fully concur a sailbike is a v exciting notion, and no doubt is a reality somewhere.

~:) - I wonder if one sails a bike in reverse? The rudder is at the back on a boat.

Such a close parallel to a sailboard or para surfer tho. The rider uses his weight to counterbalance the other forces, using the wheels/keel as a pivot. Just a shame about the tacking thing on sadly restrictive roads.

Ice lake sailing? Saltlakes? Awesome speeds i hear.

Being from OZ though, I do wonder if on the right day, it could work in our outback - a car every few days and they radio ahead anyway- saves head on collisions which happen a lot - you just assume nothings coming cos nothing ever does :)

maybe use solar fabric for a sail?

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Re: The biggest problem at 25mph+ is rarely discussed resist

Post by Chalo » Apr 25, 2016 11:20 am

dogman dan wrote:There is a reason bents are banned from UCI bike racing. Too aero.
Also, they don't handle worth a crap and would routinely take out the peloton if they were allowed there. Remember that the peloton is an aero enhancement of another kind, which renders the recumbent both irrelevant and dangerous.

Image

But for an individual running his own non-racing "time trial", recumbent layout has its place. It's a better choice for a suburban or exurban rider than for someone in the city. 'Bents don't like making stops, cornering, maneuvering around obstacles and hazards, or sharing limited spaces.
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Re: The biggest problem at 25mph+ is rarely discussed resist

Post by cycleops612 » Apr 25, 2016 11:43 am

dogman dan wrote:There is a reason bents are banned from UCI bike racing. Too aero. Start with a recumbent for the best results, then if you like, go for the fairing, tailbox, or even full velomobile.

As for riding really fast, in a city commute on a racing bike, see ya! Because they don't see you, and it's a lot harder to watch out for those suckers in a racing tuck.

I'm not saying aero is unimportant. It just is unimportant compared to survival, and unimportant compared to getting 1000 mpg vs 500 mpg equivalent. 500 mpg is still good enough for me.

They have been trying to kill me for 50 years now, and I have never ever allowed a car to hit me. I will confess though, I did hit a car once, when I was 18. That one entirely my fault, skidding a turn farther than I planned, I hit a parked car.

Whatever you build, if you ride in city traffic, have your head vertical, looking for the next left cross.
I love your work so far dogman btw, dunno how to fan and like yet if possible, but yeah, very wise and pragmatic.

re your post

I assume drop bars didnt work for you when you tried them. I intuitively thought the same, but I found the reality was that i rode mainly just as upright, gripping the top of the bars and braking just fine, and having the option of tucking down for fast declines etc. when wind becomes a problem and its all pretty clear sailing ahead. On an ebike i can see this being a very nice option

"They have been trying to kill me for 50 years now" - sums up why you are still around - a very healthy attitude for young uns to adopt. Me too & a similar accident record in almost 60 years of riding, sole transpot for ~10 of those years. I assume they cant see me or dont care, and work back from that. Relying on lights and things is dangerously delusional :). One has to be impressed by modern hivis vests etc tho. Hard to miss :(.

Which is why it drives me mental that folk cant at least even indicate their intentions, whether they think anybody about or not. How hard is that; essential, fundamental, prang risk reducer?

There does seem some contradiction here tho - every man for himself yet a focus on being seen?

Yep, respect to the ergonomic and aerodynamic potential of recumbents, but not for me either. Too creepy being down there in traffic.

Some whimsy on that is re my contention that freestyle swimming is the best workout. Whatever, it is novel in that all limbs and much of the torso provide power output concurrently (water cooled too :)).

Fancifully, what about a freestyle swimming position "recumbent" (chaps missionary position/humpent bikes?) could be devised - the guy uses "arm strokes/leg kicks/body rocking" to work pulleys and cables or pedals.

i.e., the body can deliver much more, but the power transmission mechanisms are too primitive.
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Re: The biggest problem at 25mph+ is rarely discussed resist

Post by WoodlandHills » Apr 25, 2016 11:49 am

Chalo wrote:
dogman dan wrote:There is a reason bents are banned from UCI bike racing. Too aero.
Also, they don't handle worth a crap and would routinely take out the peloton if they were allowed there. Remember that the peloton is an aero enhancement of another kind, which renders the recumbent both irrelevant and dangerous.

Image

But for an individual running his own non-racing "time trial", recumbent layout has its place. It's a better choice for a suburban or exurban rider than for someone in the city. 'Bents don't like making stops, cornering, maneuvering around obstacles and hazards, or sharing limited spaces.
They also aren't much fun over rough pavement: the inability to momentarily rise up on the pedals means your spine gets jackhammered on anything but euro-smooth roads.

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Re: The biggest problem at 25mph+ is rarely discussed resist

Post by cycleops612 » Apr 25, 2016 12:33 pm

The snap in your post looks like a where's wally kids puzzle :)

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Re: The biggest problem at 25mph+ is rarely discussed resist

Post by craneplaneguy » Apr 25, 2016 8:40 pm

What are we looking at in the above pic? How could that bunch of riders join up in such an aero favorable grouping? Intuitive, pre-planned, dumb luck?! A bit more tapered at the rear would have been a bit better....but not too shabby, that is a very cool pic.

In 50 miles of interstate driving today, I spotted 4 of those ass end fairings the big rig trailers are now using. Like the undercarriage fairings, or for that matter the top of cab fairings, they start out kind of rare, then quickly become common, as the drag reduction benefits and cost savings are so great.

A common thing seen in the off airport/back country/bush plane world, which I'm a part of, is rough field landing gear totally unfaired. Lots of round tubing, super draggy, but many say, " it doesn't matter at our low speeds". I call BS, as the low speeds are 80 to 95 mph! My rough field gear is totally faired, as a result I have fuel burns and cruise speeds way below the usual, reducing drag pays anytime it's tried. Semitruck, bike, airplane, I don't care, it's the single most cost effective thing you can do. I remember back when I was flying ultralight aircraft, in the early '80's, we had a lot of 1" aluminum tube out in the slip stream, and somebody came up with a soft foam airfoil shaped fairing that would easily slip over that round tube. We were only flying 35 to 45 mph, so many scoffed at the benefits of drag reduction at such low speeds. I ran my own test, I took a length, 4' long, of round tube and drove down a road at 40 mph, rolled down the window and tried to hold the tubing out in the relative wind, it about dislocated my arm! Then I slipped the fairing on and with moderate effort I could hold the tube at a right angle. The epiphany I had, was that that difference in mechanical force as exerted on my arm bone, was the same mechanical force that was like a damn boat anchor holding me back when I was burning fuel to go forward. I quickly faired every exposed tube I could, and ALWAYS flew further, faster, and used less fuel then others. I do the same now with what I fly, to the extent that I find it difficult to go XC with another pilot, though we fly similar planes, as they will have to stop more often to refuel. Not to mention, that I have the E Montague, and they don't, so they want to stop at a place with "full services" and I can go ride and find "full services." Knowing all that, I was chagrined to realize that I have been guilty of going too damn fast, 30+, on the Montague, I try real hard lately to keep it about 20 :twisted:

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Re: The biggest problem at 25mph+ is rarely discussed resist

Post by cycleops612 » Apr 26, 2016 12:59 am

Good input craneplane guy, thanks

Or simply put, non believers, you should fool around putting your hand out car windows at various cycling type speeds. Its startling as you say, for normally cocooned car passengers, or even cyclists.

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Re: The biggest problem at 25mph+ is rarely discussed resist

Post by dogman dan » Apr 26, 2016 4:54 am

Well, I never said aero is not worth while. I just said riding in an aero tuck on a typical racing frame in the city is dumb. Once out in the burbs where they aren't trying to kill you every half mile, tuck all you want.

I'm not inexperienced with riding in a tuck, when I was younger I wore out a racing bike every two years, till I got through colledge and got both food and motor transport. Back then Las Cruces was not a "city". It was just a medium size town then.

All I really meant about race bars, is don't ride in a tuck in a real city. You need to see them left crossing you sooner.

And you need to put a need for efficiency in perspective. Ask yourself do you need it? On an aircraft,,,, HELL YEAH. On an ebike that needs to make it 70 miles, because that's the distance to the next water, food, electric plug,,,,HELL YEAH. But if you need to go 20 miles on your e bike, do you need to get 15 wh/mi? Not really. With a very small 500 wh battery, you can go 20 miles by getting 25 wh per mile. You can get 20 wh/mile sitting upright, with your coat unzipped flapping away, big ass panniers hanging out on the bike, just by riding 20 mph. Do you need to sweat aero to do that ride? Not really.

Like I said, I don't need to get 1000 mpg riding around town,, 500 mpg is kind of good enough.

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Re: The biggest problem at 25mph+ is rarely discussed resist

Post by cycleops612 » Apr 29, 2016 7:15 am

FYI/recommended:

https://www.google.com.au/search?q=wind ... 4wH2lOM%3A

It shows that, on a roadbike?, above 100w on the flat is all the power that can reasonably be used for actual human body transport. The rest is purely wasted on wind.

This occurs at 25k(~.625 mile)ph. Each extra 100w from there, gains a mere 5kph.

Btw - ( the average human walking speed is about 5.0 kilometres per hour (km/h), or about 3.1 miles per hour (mph). - wiki)

(it should be noted , dont quote me, that a fit labourer outputs about 70 watts on average over an 8 hour day doing physical work. So 100 watts is like shirking on a tandem with a fit bloke.)

So just saying, a humble 2.5kg 36v 10ah (360wh) bottle battery, is good for 3.5 hours running at 25kph - impressive. You could even get 100watts from a; coolish, light (I know they exist), pv panel in good sun? Almost unlimited range for touring etc. Remove panel when not needed for local exploring around a power outlet.

An advantage of being niggardly with power to the motor, is by limiting power to say 100w, it acts like a wind cruise control. The bike isnt allowed to use power unproductively, and the rider can just relax in automatic economy mode.

(a, sadly heavy, standard 24v 250w roof panel annualised average is ~1kw per day at 34 degrees lat. -= 10 hours of 100w power)

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Re: The biggest problem at 25mph+ is rarely discussed resist

Post by gogo » Apr 29, 2016 9:04 am

cycleops612 wrote:An advantage of being niggardly with power to the motor, is by limiting power to say 100w, it acts like a wind cruise control. The bike isnt allowed to use power unproductively, and the rider can just relax in automatic economy mode.
A wind speed sensor could help to avoid unproductive power use. A 100W limit could be unnecessarily restrictive when traversing grades.
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Re: The biggest problem at 25mph+ is rarely discussed resist

Post by cycleops612 » May 07, 2016 8:00 am

gogo wrote:
cycleops612 wrote:An advantage of being niggardly with power to the motor, is by limiting power to say 100w, it acts like a wind cruise control. The bike isnt allowed to use power unproductively, and the rider can just relax in automatic economy mode.
A wind speed sensor could help to avoid unproductive power use.

Its important data for a good economy mode algorithm in normal vehicles too. Have not seen any reference to, let alone actual implementations of them - aenonometers -i like your term better :) . As discussed, the often biggest power drain is ignored. odd.

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Re: The biggest problem at 25mph+ is rarely discussed resist

Post by cycleops612 » May 07, 2016 8:08 am

Maybe its just me & maybe obvious, but it seems on my electric mid-drive MTB, wind resistance is less when my profile to the wind is tall and thin, than when crouched in the pedaling position.

i.e., when i stand upright & twisted slightly side on, knees together~.

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Re: The biggest problem at 25mph+ is rarely discussed resist

Post by spinningmagnets » May 07, 2016 8:33 am

Every frame style has its fans, even recumbents (though they are admittedly few as a percentage of riders). I think the biggest resistance to actually adding a fairing (or partial fairing front and rear) is that it draws attention. We are living in a golden age here in North America, where you can ride relatively un-harassed by police, as long as you "look like" a bicycle, and maybe pedal along with the motor. Although a MXUS H45 using 72V X 50A = 3700W is only a little wider than a Yescom that is using 36V X 25A = 900W...most police don't "see" any difference.

Mount that Yescom at 900W onto a Chinese scooter with pedals? They will stop you because they see a scooter with no license plate (while the MXUS in a bicycle frame pedals on by).

I think the new California law, where you can use PAS up to 28-MPH without getting license and registration (still considered a bicycle) to be very reasonable, so I will stick to a bicycle frame and no aero...

BTW, I think Kingfish is the rider who has most frequently actually used aero on his bikes...

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Location: Sydney Australia, Me: 70kg/154lb. 350w, 22kg ex battery, 24 speed axial mid-drive Bofeili MTB.

Re: The biggest problem at 25mph+ is rarely discussed resist

Post by cycleops612 » May 07, 2016 9:04 am

correct spinningmagnets, stealthis a big factor. So many laws largely honored in the breach already, but the avalanch of new ones only grows.

Bottom line, once the local cops deem your ebike non kosher, its on record, and its no longer really usable. If you have power, you will be tempted to use it, and eventually be spotted.

Ta daah. In my suggested roadbike, you dont have much power, but you dont need it. Road bikes are fast, light, slippery and every pedal turn counts for that much more as a result. One is "credibly fast".

I should say I am from an EU rules country, Oz, 200-250 wat legal max.

with a discrete battery and a rear hub drive (a revision on front hub thanks to your input), it would be hard for a cop to spot its electric at all.

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