A quick question about the 15.5mph assisted legal limit

Bonzo Banana

Esteemed Pedelecer
Sep 29, 2019
388
184
I believe I'm right in writing there is a 10% tolerance for this speed so the real maximum top speed is about 17-17.5mph but this is the absolute top legal limit. It allows for different tyre sizes that would mean different assist speeds.

I'm just curious how is the 15.5mph limit set is it the smallest tyre size for the wheel or is it roughly in the middle of sizes so those bikes with lower profile tyres would actually get less than 15.5mph assistance?

What boost could I expect from going from a 26"x1.25 tyre to a 26"x2.35 tyre?

 
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flecc

Member
Oct 25, 2006
50,851
28,685
I believe I'm right in writing there is a 10% tolerance for this speed so the real maximum top speed is about 17-17.5mph but this is the absolute top legal limit. It allows for different tyre sizes that would mean different assist speeds.

I'm just curious how is the 15.5mph limit set is it the smallest tyre size for the wheel or is it roughly in the middle of sizes so those bikes with lower profile tyres would actually get less than 15.5mph assistance?

What boost could I expect from going from a 26"x1.25 tyre to a 26"x2.35 tyre?

That's correct, the DfT have confirmed that the 10% tolerance applies to all the legal speed limits. Other countries do similar.

Pedelec makers set the limit according to the tyres they are fitting on any given model, but there is flexibility in what they do. For example, German brand Kalkhoff on their first pedelecs in 2007 fixed it slightly low since Germany had a national 24 kph (15mph) pedelec assist limit, very slightly lower than the EU one.

However, later when using a more powerful crank drive unit, they reduced the rear sprocket by one tooth to take full advantage of the 10% with an assist speed limit of 17 mph.

Your query on the two tyre widths cannot be answered accurately since the tread thickness varies by tyre size and/or brand, some tyres being taller than others. Kenda for example.
.
 
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Bonzo Banana

Esteemed Pedelecer
Sep 29, 2019
388
184
That's correct, the DfT have confirmed that the 10% tolerance applies to all the legal speed limits. Other countries do similar.

Pedelec makers set the limit according to the tyres they are fitting on any given model, but there is flexibility in what they do. For example, German brand Kalkhoff on their first pedelecs in 2007 fixed it slightly low since Germany had a national 24 kph (15mph) pedelec assist limit, very slightly lower than the EU one.

However, later when using a more powerful crank drive unit, they reduced the rear sprocket by one tooth to take full advantage of the 10% with an assist speed limit of 17 mph.

Your query on the two tyre widths cannot be answered accurately since the tread thickness varies by tyre size and/or brand, some tyres being taller than others. Kenda for example.
.
I might measure a few tyres to see their overall circumference and how they vary. Many kits don't come with tyres just a bare wheel so I guess they could choose a tyre to base their speed on despite not supplying one. So if you use a tyre like a Schwalbe fat frank 26"x2.35" you will get some bonus speed I assume. The bigger the wheel the more boost you get so a 700c/29" wheel will have the most boost and a 16" wheel the least assuming you fit the biggest tyres.
 
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flecc

Member
Oct 25, 2006
50,851
28,685
I might measure a few tyres to see their overall circumference and how they vary. Many kits don't come with tyres just a bare wheel so I guess they could choose a tyre to base their speed on despite not supplying one.
This is the anomaly that the pedelec law doesn't apply to kits. In law they don't exist since the technical standard EN15194 only refers to complete pedelecs. Universally we assume that if we comply to the law, the authorities will turn a blind eye to kit based conversions and that seems to work ok, so far at least!

To get tyre circumference accurately I place a spirit level across the top of the wheel and measure the distance from the level to the ground, then multiply by pie.
.
 
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StuartsProjects

Esteemed Pedelecer
May 9, 2021
500
286
That's correct, the DfT have confirmed that the 10% tolerance applies to all the legal speed limits. Other countries do similar.
Is that a tolerance where they are saying you are not likely to be prosecuted unless you exceeed it, or does the law explicitly say 15.5mph + 10% ?
 

WheezyRider

Esteemed Pedelecer
Apr 20, 2020
933
506
I might measure a few tyres to see their overall circumference and how they vary. Many kits don't come with tyres just a bare wheel so I guess they could choose a tyre to base their speed on despite not supplying one. So if you use a tyre like a Schwalbe fat frank 26"x2.35" you will get some bonus speed I assume. The bigger the wheel the more boost you get so a 700c/29" wheel will have the most boost and a 16" wheel the least assuming you fit the biggest tyres.

If you are using Schwalbe tyres, there is a handy chart here with circumference info:

 
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flecc

Member
Oct 25, 2006
50,851
28,685
Is that a tolerance where they are saying you are not likely to be prosecuted unless you exceeed it, or does the law explicitly say 15.5mph + 10% ?
It's a tolerance but there is no likelyhood about it. The DfT make the law and to account for inevitable errors in measurement they allow a 10% tolerance in all UK road speed limits which the police have to observe.

And they do it in practice, no-one gets prosecuted for doing up to 77 mph on motorways for example and often more generously. When Gatso evidence was still being checked manually, they ignored anything below 35 mph in 30 limits, nearly 17% tolerance.
.
 

Bonzo Banana

Esteemed Pedelecer
Sep 29, 2019
388
184
This is the anomaly that the pedelec law doesn't apply to kits. In law they don't exist since the technical standard EN15194 only refers to complete pedelecs. Universally we assume that if we comply to the law, the authorities will turn a blind eye to kit based conversions and that seems to work ok, so far at least!

To get tyre circumference accurately I place a spirit level across the top of the wheel and measure the distance from the level to the ground, then multiply by pie.
.
I didn't know that about kits. I assume they are still tested and sold to be EN15194 compliant. I went onto the page here to clarify and I'm more confused;


Just to see what they said and it states maximum power 250W rather than nominal or rated and yet just about every ebike either pre-built or a kit exceeds 250W maximum power. You can spend £12k on a high end Bosch based ebike and despite having a super high torque motor and peaking over 700W its still sold as legal to use on the road. Bosch are renowned for good certification as German certification standards and compliance is very high typically.

It feels to me this would be a lot simpler if they just had a simple rule no assistance beyond 17mph or something like that. Looking at the text below from the site. You only have to have the manufacturer of the motor and the battery voltage on the bike as you are given an option what to put on the bike but that info isn't that useful. On a hub motor ebike its the controller that dictates how much power goes to the hub motor. The motor just gets what it is given from the controller. Also is it the actual manufacturer required or the importer or trade house that needs to be marked on it? There is no information stating that it has to be a pedelec type bike i.e. motor only operates when the pedals are turning. It says pedals that can be used to propel it. Maybe that is because they have simplified it to allow for pre-2016 ebikes which are still legal to use. Maybe they accept the police would find it difficult to tell the difference between pre 2016 and post 2016 ebikes out in the field and that is why they have done that. The only ebikes I have seen that only peak at 250W are those very cheap 20" folding ebikes that perhaps have a nominal motor around 140-180W at 24V and the controller has a peak current of only 9-11A. It reads like 99% of ebikes are illegal because they easily exceed 250W quite a lot of the time.

Laws and standards need to be workable and it just feels ebike legislation is in a very poor state, simplified rules would be much better and then police could realistically police it properly. So kits aren't part of the certification standard either so it just feels like the police can stop just about any ebike and find some sort of legal issue with it or they can just ignore them completely which seems to be the situation most of the time. The police have probably looked at the legislation had a laugh at how stupid and unworkable it is and feel they can't do anything with it which seems to be how they regard ebikes.

My ebike rules would probably be;

Maximum assistance 15.5mph with 10% tolerance
2 brakes that can stop the bike under full load within maybe 20 metres at 25mph, something like that.

I guess the other rules would just be standard bicycle standards.

What counts as an EAPC
An EAPC must have pedals that can be used to propel it.
It must show either:

  • the power output
  • the manufacturer of the motor
It must also show either:
  • the battery’s voltage
  • the maximum speed of the bike
Its electric motor:
  • must have a maximum power output of 250 watts
  • should not be able to propel the bike when it’s travelling more than 15.5mph
 

StuartsProjects

Esteemed Pedelecer
May 9, 2021
500
286
The situation is a bit like the enforcement of vehicle speed limits of vehicles using cameras. The ACPO 'guidance' for enforcement is speed limit + 10% + 2mph.

But the speed limit remains as the legal limit.
 
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WheezyRider

Esteemed Pedelecer
Apr 20, 2020
933
506
What counts as an EAPC
An EAPC must have pedals that can be used to propel it.
It must show either:

  • the power output
  • the manufacturer of the motor
It must also show either:
  • the battery’s voltage
  • the maximum speed of the bike
Its electric motor:
  • must have a maximum power output of 250 watts
  • should not be able to propel the bike when it’s travelling more than 15.5mph
What they have missed out is the word continuous. It doesn't matter what the maximum power is, it is whether it can sustain 250W output without over heating. Peak output is unworkable, as even a tiny motor could output 1kW for a second, but then it would burn out. It doesn't help when official gov websites can't even get it right.
 

flecc

Member
Oct 25, 2006
50,851
28,685
I didn't know that about kits. I assume they are still tested and sold to be EN15194 compliant. I went onto the page here to clarify and I'm more confused;


Just to see what they said and it states maximum power 250W rather than nominal or rated and yet just about every ebike either pre-built or a kit exceeds 250W maximum power. You can spend £12k on a high end Bosch based ebike and despite having a super high torque motor and peaking over 700W its still sold as legal to use on the road. Bosch are renowned for good certification as German certification standards and compliance is very high typically.

It feels to me this would be a lot simpler if they just had a simple rule no assistance beyond 17mph or something like that. Looking at the text below from the site. You only have to have the manufacturer of the motor and the battery voltage on the bike as you are given an option what to put on the bike but that info isn't that useful. On a hub motor ebike its the controller that dictates how much power goes to the hub motor. The motor just gets what it is given from the controller. Also is it the actual manufacturer required or the importer or trade house that needs to be marked on it? There is no information stating that it has to be a pedelec type bike i.e. motor only operates when the pedals are turning. It says pedals that can be used to propel it. Maybe that is because they have simplified it to allow for pre-2016 ebikes which are still legal to use. Maybe they accept the police would find it difficult to tell the difference between pre 2016 and post 2016 ebikes out in the field and that is why they have done that. The only ebikes I have seen that only peak at 250W are those very cheap 20" folding ebikes that perhaps have a nominal motor around 140-180W at 24V and the controller has a peak current of only 9-11A. It reads like 99% of ebikes are illegal because they easily exceed 250W quite a lot of the time.

Laws and standards need to be workable and it just feels ebike legislation is in a very poor state, simplified rules would be much better and then police could realistically police it properly. So kits aren't part of the certification standard either so it just feels like the police can stop just about any ebike and find some sort of legal issue with it or they can just ignore them completely which seems to be the situation most of the time. The police have probably looked at the legislation had a laugh at how stupid and unworkable it is and feel they can't do anything with it which seems to be how they regard ebikes.

My ebike rules would probably be;

Maximum assistance 15.5mph with 10% tolerance
2 brakes that can stop the bike under full load within maybe 20 metres at 25mph, something like that.

I guess the other rules would just be standard bicycle standards.

What counts as an EAPC
An EAPC must have pedals that can be used to propel it.
It must show either:

  • the power output
  • the manufacturer of the motor
It must also show either:
  • the battery’s voltage
  • the maximum speed of the bike
Its electric motor:
  • must have a maximum power output of 250 watts
  • should not be able to propel the bike when it’s travelling more than 15.5mph
It's no use trying to understand the law by looking at government guidance pages. That's because, like you, they are trying to simplify the law and it cannot be simplified.

For example, you said the law should be assist limit of 15.5 mph + 10% tolerance, but that is wrong because you've forgotten that the 10% is a tolerance to allow for speed measurement inaccuracies.

If we did as you said and that was the law, then pedelecs would be designed to 17 mph and we'd need to have the 10% tolerance added to 17 mph to allow for the speed measurement inaccuracies of laser checks or timing over distance.

The law is what it is because that is what it has to be, as StuartsProjects and WheezyRider have shown. It has to be as precise as possible. For that reason it is in various parts:

There's the exemption from being a motor vehicle in law contained in the two and three wheeled motor vehicle type approval law, which sets the 250 watt continuous power limit, the 25 kph assist speed limit and power stopping when not pedalling, the exemption only applying if these are met.

Then there's the technical standards document EN15194 to show how these are achieved and measured.

Those concern design and construction, but then there's the Usage Law, the EAPC regulations which tell the public how pedelecs can be legally used on the roads.

It's actually all very simple, just do what is allowed, nothing more.
.
 

Bonzo Banana

Esteemed Pedelecer
Sep 29, 2019
388
184
It's no use trying to understand the law by looking at government guidance pages. That's because, like you, they are trying to simplify the law and it cannot be simplified.

For example, you said the law should be assist limit of 15.5 mph + 10% tolerance, but that is wrong because you've forgotten that the 10% is a tolerance to allow for speed measurement inaccuracies.

If we did as you said and that was the law, then pedelecs would be designed to 17 mph and we'd need to have the 10% tolerance added to 17 mph to allow for the speed measurement inaccuracies of laser checks or timing over distance.

The law is what it is because that is what it has to be, as StuartsProjects and WheezyRider have shown. It has to be as precise as possible. For that reason it is in various parts:

There's the exemption from being a motor vehicle in law contained in the two and three wheeled motor vehicle type approval law, which sets the 250 watt continuous power limit, the 25 kph assist speed limit and power stopping when not pedalling, the exemption only applying if these are met.

Then there's the technical standards document EN15194 to show how these are achieved and measured.

Those concern design and construction, but then there's the Usage Law, the EAPC regulations which tell the public how pedelecs can be legally used on the roads.

It's actually all very simple, just do what is allowed, nothing more.
.
It seems to have been made less simple by that government site simplifying it. So basically the 10% tolerance is for measuring inaccuracies not the fact that changing the tyre fitted to the bike could increase its speed.

People are actively using very high powered ebikes on the road with little or no risk of prosecution it seems. I guess you could say its because the police are under resourced and have bigger fish to fry but it also could be the state of the legislation currently is confusing.

What easy way can you determine a ebike pre 2016 vs later than 2016 especially if you have converted an older pre 2016 bike with new ebike parts that have a throttle. Is it the bike itself that governs pre-2016 or the motor parts. What if you have replaced motor parts that were pre-2016 with post 2016 parts to keep the ebike running is it still legal to use with a throttle that doesn't require pedalling? I find it a bit confusing. How would a policeman be able to determine the legality of such a ebike. In the real world does it even matter if the throttle works if pedalling or not as long as it keeps to around 15.5mph assistance. In fact you could make the case that you would be more spatially aware of what is around you if you didn't have to pedal in urban traffic navigating and positioning between lots of different vehicles. You could be less tired and more focused.
 

StuartsProjects

Esteemed Pedelecer
May 9, 2021
500
286
I find it a bit confusing. How would a policeman be able to determine the legality of such a ebike.
The same would apply to a car. How would a Policeman be able to determine its legality ? Very unlikley that they could, in detail, so it would go to 'experts' for checking.

The likley scenario is that the rider\driver has to do something worthy of a stop, speeding for instance, and a Policeman may then be inclined to investigate further.
 

jimriley

Esteemed Pedelecer
Jun 17, 2020
347
223
I've read some me where, maybe here, that ordinary plod can't do much, it has to be a traffic cop that pulls you/inspects your bike.
 

flecc

Member
Oct 25, 2006
50,851
28,685
People are actively using very high powered ebikes on the road with little or no risk of prosecution it seems. I guess you could say its because the police are under resourced and have bigger fish to fry but it also could be the state of the legislation currently is confusing.
No, the leg islation isn't confusing to those who wish to stick to the law, which is very simple. i.e. no power above 15.5 mph, power only when pedalling, maximum power rating 250 watts. Nothing complicated about that.

It's only complicated to those who are tryimg to find loopholes.

What easy way can you determine a ebike pre 2016 vs later than 2016 especially if you have converted an older pre 2016 bike with new ebike parts that have a throttle. Is it the bike itself that governs pre-2016 or the motor parts. What if you have replaced motor parts that were pre-2016 with post 2016 parts to keep the ebike running is it still legal to use with a throttle that doesn't require pedalling? I find it a bit confusing.
If the pedelec is pre January 2016, it can have a throttle, either the original one or a replacement if that fails. Judgemnt is according to whether the person repairing was keeeping to the spirit of the law or converting to get around the law.

In the real world does it even matter if the throttle works if pedalling or not as long as it keeps to around 15.5mph assistance.
Yes it does matter. You are once again trying to dodge around what I've already explained. It's only a bicycle in law if all propulsion is by pedalling. If propulsion is possible without pedalling by using a throttle, it's a motor vehicle. THAT is the real world.
.
 

jimriley

Esteemed Pedelecer
Jun 17, 2020
347
223
No, the leg islation isn't confusing to those who wish to stick to the law, which is very simple. i.e. no power above 15.5 mph, power only when pedalling, maximum power rating 250 watts. Nothing complicated about that.

It's only complicated to those who are tryimg to find loopholes.



If the pedelec is pre January 2016, it can have a throttle, either the original one or a replacement if that fails. Judgemnt is according to whether the person repairing was keeeping to the spirit of the law or converting to get around the law.



Yes it does matter. You are once again trying to dodge around what I've already explained. It's only a bicycle in law if all propulsion is by pedalling. If propulsion is possible without pedalling by using a throttle, it's a motor vehicle. THAT is the real world.
.
Yet is it woosh who are having a batch type approved as pedelecs with a throttle?
 

flecc

Member
Oct 25, 2006
50,851
28,685
Yet is it woosh who are having a batch type approved as pedelecs with a throttle?
No, it's Wisper.

They are NOT being type approved as pedelecs. They are being type approved as class 250 LPM, the LPM standing for low powered mopeds, which is a motor vehicle class.

In Britain only the DfT has said that as a concession they will allow them to be used like pedelecs without the bureacracy, a dodge around the law to allow British people to have a throttle since they are so obsessed about that.

Personally I think that was a daft decision, but Britain has always been expert at doing daft. Just look at the current chaos over the Irish border.
.
 

Wisper Bikes

Trade Member
Apr 11, 2007
6,005
1,966
67
Sevenoaks Kent
There is absolutely no doubt in my mind, and judging by the take up of throttle controlled ebikes, that this was a great concession and the right thing to do. Most of the people who have bought these bikes would not have been able to taste the freedom that cyclists enjoy without the use a throttle device. It has made cycling even more inclusive.

All the best, David