wow anyone get many postive comments on there ebike?

[CXRAndy]

Have they got a max speed? Saw a couple flying down a hill on Anglesey, Sagan wouldn't have kept up

There is no upper limit to the bikes speed. Once the bike exceeds the assistance threshold, you're using gravity. Being heavier than normal bikes they pickup more speed

 

[Drago]

As a point of order, that's against the laws of physics. Leaving aside any differences in aerodynamics and rolling resistance, a heavy bike will gather speed due to gravity at the same rate as a lighter one.

The difference is that a moving heavy bike possesses more inertia so may roll further, but it will not roll any faster.

 

[Landsurfer]

My LBC seems to only sell hyper fast E-MTB types thay have no road speed governing but seem to be mostly used on roads ...
Negative comment ? .... A MOTORbike is a MOTORbike ..
My wife loves hers ...

 

[ColinJ]

As a point of order, that's against the laws of physics. Leaving aside any differences in aerodynamics and rolling resistance, a heavy bike will gather speed due to gravity at the same rate as a lighter one.

The difference is that a moving heavy bike possesses more inertia so may roll further, but it will not roll any faster.

But of course we CAN'T leave aside those differences when riding...

When I lost over 25 kgs in weight my speed freewheeling down local descents was dramatically reduced. If I bought a monster bike that weighed 35 kgs I would be tearing down those descents on it.

Absolutely incorrect! The reason that works on the moon is that there is no atmosphere. Once there is air, you get the concept of terminal velocity. The terminal velocity of a feather is very low, that of a cannonball isn't!

The force acting on a bike plus its rider down the slope of a hill is proportional to their combined mass, whereas the main force slowing the combination down is wind resistance which is proportional to their combined frontal area. As a cyclist gets heavier, his/her surface area increases only slightly for large increases in mass, therefore heavier cyclists can naturally go downhill faster. (I'm talking about simple fast descents, not technical ones where skill is required.)

I've been proving that on forum rides over the past couple of years. We have hills round here up to 6 miles in length and I can't keep up with skinny CC riders going uphill but I can often overtake them on descents without even pedalling!

A great example of that was on a holiday on the Costa Blanca a few years back. I was grovelling up a huge hill when a skinny female cyclist shot past me about a kilometre from the summit. When I finally got to the top, I could see her way ahead of me on the descent. I set off in pursuit and caught her up by the time she was half way down. I overtook her at 50 mph, barely even pedalling. I looked back and her legs were spinning round at a ridiculously high cadence and she couldn't get close to me. When the road flattened off, I slowed down and she finally caught up and asked how that was possible. She'd been spinning out in her highest gear. I asked how much she weighed and her weight was 7 stone. I weighed about 13.5 stone at the time...

 

[Grant Fondo]

Back to the original OP... I am in favour of the tech as it may get more people cycling. If the battery gave out into a headwind on a cold winters day, maybe not?

 

[Drago]

But of course we CAN'T leave aside those differences when riding...

When I lost over 25 kgs in weight my speed freewheeling down local descents was dramatically reduced. If I bought a monster bike that weighed 35 kgs I would be tearing down those descents on it.

But that is not your reduced mass making the difference. Its youre aerodynamic coefficient expressed as a ration to your mass that makes the difference. Eat a 50kg barbell (not advisable, you'll likely get the squirts) and maintain the same external size and shape and your peak velocity will be no higher than before.

 

[ColinJ]

But that is not your reduced mass making the difference. Its youre aerodynamic coefficient expressed as a ration to your mass that makes the difference. Eat a 50kg barbell (not advisable, you'll likely get the squirts) and maintain the same external size and shape and your peak velocity will be no higher than before.

Sorry, but that isn't true!

If you take 2 identical table tennis balls and use a syringe to fill one with water, then drop them both from a great height you will soon see that. The water-filled ball will rapidly pull away from the air-filled one.

The gravitational force acting on the balls is proportional to their individual masses. They both have the same size and shape and are made of the same material so the air drag acting on them at the same speed is identical. (Drag is proportional to the square of the velocity, and all other factors are equal.)

An object falling in air continues to increase in velocity until the drag force exactly opposes the force due to gravity - that is the object's terminal velocity.

The terminal velocity of the heavier ball is higher than that of the lighter one.

 

[Ming the Merciless]

Yep the heavier rider + bike combination will accelerate faster downhill than the lighter one. If in a vacuum then apart from dying their rates of acceleration would be the same.

 

[CXRAndy]

As a point of order, that's against the laws of physics. Leaving aside any differences in aerodynamics and rolling resistance, a heavy bike will gather speed due to gravity at the same rate as a lighter one.

The difference is that a moving heavy bike possesses more inertia so may roll further, but it will not roll any faster.

I beg to differ, from actual ride comparison

. When coming down very long straight descent in Tenerife, I mean over a mile long, I sailed by two lighter smaller women riders, whilst on the huds. Other riders mentioned the funny scene of two women tucked aero as possible trying to hold my wheel whilst I cruised in a less aero position freewheeling.

Just watch the heavier professional riders leave the smaller climber types on descents.

 

[Ming the Merciless]

The physics backs it up as well. It’s not just anecdotes

 

[Landsurfer]

As a tall (6’ 2” ), fat, heavy guy ( 110kg + ) .... ...
On the drop from the A9 / B9177 into Inverness the combination of my my mass AND .. my pear shaped, shape, allowed me achieve our highest WIMPS speed of 39mph.
It’s not just the mass, it’s the FPS (Fat Pear Shaped) aerodynamics that count...

 

[Pale Rider]

From 10 years of ebiking, there's no doubt I gather pace more quickly on a freewheel descent than a pushbike.

Given that all other factors are roughly equal it must be the extra weight causing the extra speed.

Tandems are also known to descend like rockets, which again can only be due to the greater overall weight of the rig.

 

[carpiste]

After years riding a regular bike,both road and hybrid, I suddenly found myself old, fat and unhealthy after several surgeries. I got back to cycling by getting on an excercise bike then tried a steady ride on a hybrid. My Dog it was painful!
So I decided to get an e-bike and after 6/7 weeks in the saddle I feel more confident, fitter and more able to take on gentle slopes.
I`ve not been called a cheat and have only had interest about the bikes handling, efficiency and looks! Not one person has commented on the physics.
I got to an age where, even if they did call me a cheat, I couldn`t give a monkeys! I cycle for my benefit not others and without the assistance from my hub motor I`m not sure I`d ever get bck out.
My advice? Forget the physics, ignore the doubters and enjoy

 

[theboxers]

Do not talk to the chopper riders. Under any circumstances…

Especially this one

 

[Boopop]

I can't help but wonder how many people that consider eBikes "cheating" also think ICE/E vehicles are cheating too. To me it betrays what appears to be an opinion that cycling is only a hobby/sport and not a means of transport. Time to take the motor out of the car and go back to the only form of four wheeled transport that isn't "cheating"!