Who needs more than 250W?

Electrically assisted bikes, trikes, etc. that are legal in the UK
peterb
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Re: Who needs more than 250W?

Post by peterb »

I have been told that at the time the EU regulations were drawn up the 25km maximum assistance cut off was thought to be appropriate as most if not all ebikes at the time were utility bikes. I agree that the cut off should be higher for e-road bikes (as I've posted many times). !8 - 20 mph would be appropriate. Of course the trade off would be shorter range. I find it difficult to stay with a club group when the speed drifts above the cut off speed even with the help given by drafting. But I can't see the law being changed any time soon.
Merlin
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Joined: 8 Apr 2021, 8:47pm

Re: Who needs more than 250W?

Post by Merlin »

Sadly I agree Peter.

It does make the things both less attractive and less flexible however whilst in no way increasing danger to any road user. I doubt for instance, that disc brakes were so common place when legislation was brought in.

If you are climbing a long 5% gradient in the Lakes or somewhere, the extra power required to do climb at 20km/h is circa 150 watts - assuming an 90kg bike and rider. That's the Tour mode on something like the Bosch AFAIK. We should all be able to put out 150w without an issue. Less is needed from us in Sport or Turbo mode of course should we apply it.

Climbing at 4 watts per kg. Would have us losing assistance. Climbing an a 8% gradient would be the max output of the Bosch on that hill, with us putting in 200 watts. That's a crazy climbing speed whereas that assistance is not available at normal, flat riding. If my maths is correct (and that's a big "IF" given my condition) you could climb the Alpe in around 40 minutes. I've climbed it in 49 minutes but I was super fit back then and it hurt like hell. One hour is considered a good time for us. That's nothing on an EBike. On the flat we only need circa 75 watts to hit the limiter and lose assistance. It's only really of use for a trip to the shops. I'm 57 years old.

Given the speeds these things can generate on down hills AND the problems with mass and cornering, the current rules are in need of revision when people look at the maths IMHO.
Oldjohnw
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Re: Who needs more than 250W?

Post by Oldjohnw »

How does an ebike particularly generate speed downhill?
John
Blondie
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Re: Who needs more than 250W?

Post by Blondie »

Average speed across thousands of UK riders on Strava is around 15 mph. The cutoff is perfectly reasonable.
peterb
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Re: Who needs more than 250W?

Post by peterb »

Blondie wrote: 1 Jul 2021, 8:01am Average speed across thousands of UK riders on Strava is around 15 mph. The cutoff is perfectly reasonable.
There is a big difference between average and maximum. To average 15mph on an ebike means riding considerable distances at well over 15 mph, without any assistance. No doubt many ebike riders can do this, but for many who are riding for reasons of age or disability this can be difficult.
Jdsk
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Re: Who needs more than 250W?

Post by Jdsk »

Merlin wrote: 30 Jun 2021, 11:16pmGiven the speeds these things can generate on down hills AND the problems with mass and cornering, the current rules are in need of revision when people look at the maths IMHO.
Oldjohnw wrote: 1 Jul 2021, 7:19am How does an ebike particularly generate speed downhill?
And what's the issue about mass and cornering, please?

Thanks

Jonathan
Merlin
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Re: Who needs more than 250W?

Post by Merlin »

Oldjohnw wrote: 1 Jul 2021, 7:19am How does an ebike particularly generate speed downhill?
Weight.

With cornering it's the centre of gravity.

It's basic physics - cornering could be enhanced should the bike have an incredibly low centre of gravity it doesn't of course - hence you have more weight fighting to not turn.

With "average speed" try it by all means. You will find most of the time you are riding at 17-18 mph - unless you are spectacularly unfit in which case a group ride is probably nor for you. Peter's spot on with that.
Jdsk
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Re: Who needs more than 250W?

Post by Jdsk »

Merlin wrote: 1 Jul 2021, 9:40amIt's basic physics - cornering could be enhanced should the bike have an incredibly low centre of gravity it doesn't of course - hence you have more weight fighting to not turn.
I don't know what this means.. is there any current (!) restriction on the mass or position of batteries or motors?

What would you like to be different?

Thanks

Jonathan
Merlin
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Joined: 8 Apr 2021, 8:47pm

Re: Who needs more than 250W?

Post by Merlin »

Imagine trying to take the same corner at the same speed without leaning into it. That's the effect that mass has on cornering.

The position was a hypothetical proposition. BB Height and shape mean that the battery has to be roughly around the middle of the leg and the motor has to be at hub or bb height.

Either way, ride as you would your normal bike and you come a cropper. We've tested it. Given that the brain, over time, seems to develop a reflex with regards to leaning into a corner, the result is that we brake harder so that the ingrained "lean" is suffice to make the corner safely. The ebike is of course also faster on straight descents because of it's weight all other things being equal. That requires more braking too.

All in all, it needs quite an adjustment period if you are going to buy a road ebike IME.
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NATURAL ANKLING
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Re: Who needs more than 250W?

Post by NATURAL ANKLING »

Hi,
If you have a bike which is relatively heavy and is unpowered, you are liable to have a relative amount of experience in handling the bike unless you fall off quite a lot.
E bikes are definitely heavier, this is just one problem with an E bike, the other problem is something I have noticed with my recent work on E bikes is that The brakes might not be up to the job, in other words I feel that the brakes need to be a better quality and or better set up out of the box?
NA Thinks Just End 2 End Return + Bivvy - Some day Soon I hope
You'll Still Find Me At The Top Of A Hill
Please forgive the poor Grammar I blame it on my mobile and phat thinkers.
Jdsk
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Re: Who needs more than 250W?

Post by Jdsk »

Merlin wrote: 1 Jul 2021, 9:55amEither way, ride as you would your normal bike and you come a cropper.

All in all, it needs quite an adjustment period if you are going to buy a road ebike IME.
That wasn't my experience on an Orbea Gain D20. Handling was very similar to an unmotored bike.

But I don't see the connection to wanting (let alone needing) more power than allowed in the current regulations...

Jonathan
Merlin
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Re: Who needs more than 250W?

Post by Merlin »

Just really that I could hit speeds of 80kph quite easily given the weight as I came into town Jonathan. I can overtake all the traffic on the road. Yet I cannot ride at a pace that allows me to ride with others or indeed in many circumstances, allows me to feel safe with other road users. I simply don't see the logic. As I say, the rules were put into place before the advent of disc brakes on road going bikes for starters.

I was just trying to point out the stupidity of the current regulations when it comes to allowing more people to enjoy riding a bike with younger, healthier friends, or indeed efficiently and safely on many British roads.

The BMR (Basal Metabolic Rate) means that we consume 85 watts sleeping. We are going to add another 35 watts to that and call it exercise?
Blondie
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Re: Who needs more than 250W?

Post by Blondie »

peterb wrote: 1 Jul 2021, 9:12am
Blondie wrote: 1 Jul 2021, 8:01am Average speed across thousands of UK riders on Strava is around 15 mph. The cutoff is perfectly reasonable.
There is a big difference between average and maximum. To average 15mph on an ebike means riding considerable distances at well over 15 mph, without any assistance. No doubt many ebike riders can do this, but for many who are riding for reasons of age or disability this can be difficult.
Averages are usually most effected by speeds going uphill. E bikes have a distinct advantage here and my experience is that they will mostly out pace us middle aged folk on normal bikes. Keeping up on an e bike is not a problem unless with fit younger riders.
peterb
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Re: Who needs more than 250W?

Post by peterb »

Blondie wrote: 1 Jul 2021, 10:49am
peterb wrote: 1 Jul 2021, 9:12am
Blondie wrote: 1 Jul 2021, 8:01am Average speed across thousands of UK riders on Strava is around 15 mph. The cutoff is perfectly reasonable.
There is a big difference between average and maximum. To average 15mph on an ebike means riding considerable distances at well over 15 mph, without any assistance. No doubt many ebike riders can do this, but for many who are riding for reasons of age or disability this can be difficult.
Averages are usually most effected by speeds going uphill. E bikes have a distinct advantage here and my experience is that they will mostly out pace us middle aged folk on normal bikes. Keeping up on an e bike is not a problem unless with fit younger riders.
- or with riders of any age who maintain a speed above the ebike cut off speed over more than short distances. A club ride with the ebike rider yoyo-ing off the front on hills and then dropping off the back on the flat is not very satisfactory. Dropping unassisted riders on every hill is a quick way of becoming unpopular. I try and ride with the group in the way I always rode - as part of the group.
Merlin
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Joined: 8 Apr 2021, 8:47pm

Re: Who needs more than 250W?

Post by Merlin »

Image

I'll include this simply for comparison reasons. If the E Bike weighs in at 20kg with gear and you are 70kg then we are in the red...

We can obviously buy road Ebikes now that come in around 12kg and many, myself included, could shed a few ourselves...

So looking at that, you could climb an 8% gradient, maximising the power out put, at 20kph.

Alpe D'Huez would take circa 40 minutes BUT you would have to be able to effectively have an FTP yourself of 250w (in tour mode) or 3.6w/kg for the 70kg guy. You are going to be pretty fit and lithe to have that.

In real life, I managed just under 50 minutes averaging 279 watts.

So it's not the huge difference we all imagine. It just helps many of us ageing peasants with a growing waistline to ride with the full group. There's no way me, as an ageing roadie could put out 3.6w/kg for an hour 8 years on. With an ebike? I doubt it. I very much doubt I would break the hour.
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