Car wiring

[PatrickS]

Hi!

I was wondering if anyone could give some advice regarding wiring instructions for connecting a car's brakes to be towed by another car and to work simultaneously as the car pooled exceeds 750 kg which is the limit for an un-braked vehicle towed.

Thanks a lot.

 

[Robotstar5]

Do you want to operate the towed car's brakes or just the brake lights?

 

[davesparks]

He wants to operate the towed car's brakes as it is over the 750KG limit for an unbraked trailer.

To the OP:
I don't think this is possible, a cars brakes are operated by hydraulics, not electronics.
Your only sensible option is to put the car you wish to tow on a trailer.

 

[Resu]

Hi!

I was wondering if anyone could give some advice regarding wiring instructions for connecting a car's brakes to be towed by another car and to work simultaneously as the car pooled exceeds 750 kg which is the limit for an un-braked vehicle towed.

Thanks a lot.

No need to do this as that rule only applies to trailers. If you are towing any sort of distance it would be wise to borrow a car trailer though.

 

[davesparks]

No need to do this as that rule only applies to trailers. If you are towing any sort of distance it would be wise to borrow a car trailer though.

A towed car is considered to be a trailer and is subject to the same rules.

A special exception is allowed where a broken down car may be towed to the nearest place of safety using a tow rope and a driver in the towed vehicle to operate the brakes etc.

 

[Resu]

Surely it's common sense that you couldn't do what the op asked? Surely the only way round it is to use a trailer (I'm not sure you can even get a braked a frame?).

 

[Barry White]

A quick google on gov.uk revealed the brake laws dont apply to a broken down vehicle (hence the AA and rac use) but the op is correct if its a functioning vehicle the dolly must be braked and also any wheels on the road braked too so as this is technically too hard to acheve a trailer is the way forward
see http://www.direct.gov.uk/prod_consu...n/@motor/documents/digitalasset/dg_200824.pdf

 

[PEG]

If it is being towed,operating the brakes is only part of your problem,how will you operate the steering? and if that is dealt with on a dolly,that is where your braking should occur.:stooge_curly:

 

[UNG]

There are electrical braking units available to allow conversion of a vehicles braking system to allow it's brakes to be operated electrically by a towing vehicle there is even an EU standard for such systems

 

[davesparks]

Unless things have changed recently electric trailer brakes aren't legal for use on uk roads.
Coupled braking systems must be pneumatic or hydraulic.

 

[UNG]

Unless things have changed recently electric trailer brakes aren't legal for use on uk roads.
Coupled braking systems must be pneumatic or hydraulic.

Some buses have had electric brakes for a while although they do have a pneumatic back up

 

[davesparks]

That's busses though, not trailers

 

[Guest111]

This could be the start of something interesting,drive on any motorway these days and sooner or later you'll come across a motorhome towing a small car.these seem to be pretty much the norm these days for the larger motorhome owners,granted they are on a dolly,and they have a lightboard so the lights are operated by the motorhome,however I've never seen one with brakes operated by the motorhome.Has this just become the accepted norm in this situation I wonder,as I can't believe VOSA haven't become aware of it.

 

[davesparks]

The police are aware of it, but as per usual they don't know what to do so ignore it an hope it will go away!

It all depends on the maximum authorised mass of the trailer too.

Up to 750KG - no brakes required.
Up to 3500KG - overrun brakes required.
Over 3500KG - coupled braking system (hydraulic or pneumatic)

Also comes the issue of driving licences, a standard car licence only allows you to tow 750KG or a total train weight of 3500KG.

All weights are the maximum authorised mass not the actual weight of the vehicle/trailer.

So an empty trailer which has 3000KG on its rating plate but only weighs 900KG is still a 3000KG trailer.

 

[UNG]

This could be the start of something interesting,drive on any motorway these days and sooner or later you'll come across a motorhome towing a small car.these seem to be pretty much the norm these days for the larger motorhome owners,granted they are on a dolly,and they have a lightboard so the lights are operated by the motorhome,however I've never seen one with brakes operated by the motorhome.Has this just become the accepted norm in this situation I wonder,as I can't believe VOSA haven't become aware of it.

Some do have some sort of coupling for the brakes as I remember seeing a few in Spain about 10 years ago

The police are aware of it, but as per usual they don't know what to do so ignore it an hope it will go away!

It all depends on the maximum authorised mass of the trailer too.

Up to 750KG - no brakes required.
Up to 3500KG - overrun brakes required.
Over 3500KG - coupled braking system (hydraulic or pneumatic)

Also comes the issue of driving licences, a standard car licence only allows you to tow 750KG or a total train weight of 3500KG.

All weights are the maximum authorised mass not the actual weight of the vehicle/trailer.

So an empty trailer which has 3000KG on its rating plate but only weighs 900KG is still a 3000KG trailer.

I assume you are referring to licences issued since Jan '97 as I and probably a good few others on here have a car licence issued before '97 the GTW allowed is 8250 Kgs

 

[davesparks]

Yes sorry, I meant a current standard car driving licence (Class B)

I have a post 97 driving licence and have can drive a GTW of 7000KG as I've got B+E

 

[PEG]

Some buses have had electric brakes for a while although they do have a pneumatic back up

Those are not brakes,they are "retarders",which can be fitted in the drive-line,and are operated in conjunction with the main braking,usually pneumatic. They lighten the duty cycle on stop/start vehicles braking systems. A "souped up" version of this principle is used on electric vehicles and trains,to facilitate regenerative braking,where the energy dissapated in braking,is fed back into the batteries or power system. I have worked on electric braking systems on large yankee caravans,but because these operate on the bang-bang principle (on or off),the maximum braking applied has to be set way below any risk of locking up,and is therefore only an "assistance" to braking. Any proportional regulating of braking on this set-up would be quite complicated. I was surprised to see an electric braking set-up,on a mates recently purchased small tipping trailer,to go behind his quad. It also had an electric tipping ram,it looked trick,and i wired it all up for handlebar control,and gave it a year before it died...it lasted 3 months...Chinese r&d obviously not including British horse wee irate: