Brake cable fitting guide

September 1st, 2010
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Identifying Trailer brake cables

September 1st, 2010
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Buying a used trailer.

June 30th, 2010

We regularly get phone calls that start I brought have just brought a second hand trailer usually this is a purchase made from Ebay where the customer has not seen the trailer first. This can be a call that can cause the trailer to be scrapped or re sold. A trailer usually holds it value and there is no such thing as a cheap trailer. Usually if a trailer is being sold it has had its life there are a lot of trailers that are not fit or the road or are very tired these are regularly sold for a good high price and some second hand trailers can sell for a similar price to a new trailer. We do take part exchange trailers and we do see some trailers that we cannot accept. We do have a reputation to withhold and we have to be careful then we check the trailers and make sure that they are fully operational and legal before they are sold on, we do have the facilities to take on most work and we do understand the laws. Below I have listed items to check and do recommend that any one buying a trailer does view the trailer before buying and makes sure they are not buying work that is going to cost them large amounts of money or even a stolen trailer.

Please remember that currently anybody can make trailer it does not need to be inspected in any way before it is towed on the road and there is no MOT to check the state of the trailer at any time.
Trailer can kill if not properly designed, loaded or maintained and the person towing the trailer i responsible for it

The most important part of any trailer is its identity. All trailers must have an ID plate on this plate there must be the following information. Manufacturer and serial No. Number of axles, Maximum gross weight, weight per axle, nose weight and date of manufacture. Without this the trailer can be confiscated by the police.

Brakes.

Not all trailers need brakes, trailers designed for none road use or trailers under 750kg gross weight do not need brakes. Make sure that the brakes are all operational as this can cause a lot of expense

Couplings

Unbraked couplings are not usually a problem this as the only problem you can have is that it has play on a towball. This can only be rectified by replacing the coupling this will cost between £12 and £60. If i is a braked coupling there are many parts that can cost a lot of money and a full coupling can cost between £130 and £260.

Wheels and tyres

Always make sure the tyres are not damaged they are all the same size and rated for the weight rating for the gross weight of the trailer as we have seen 2600kg trailers running on 4 ply tyres that only gives the trailer a weight of under 2000kg. This can cause tyres to be overloaded and blowout this will cause stability problems and other tyres to blow out. Remember that some commercial tyres can cost in excess of £100 each.

Suspension

It is hard to see faults on suspension but things to look for are as follows.
The trailer leaning this means that the suspension has been overloaded or is worn out causing the arm to spin this can only be rectified by buying new units or axle unless the trailer has leaf springs which can be replaced but this can cost a lot of money if the springs are available to buy.
A wheel leaning at an angle this is due to a drop arm or stub axle being bent this also needs the suspension to be replaced
Corrosion, An axle or suspension units are made with a box section or with alko a triangular shaped tube check this for corrosion as these can rust through and then will fail when you least want it. Also drop arms on some smaller suspension can be made from a hollow box this can corrode and will also cause the suspension to fail.

Chassis

When inspecting the trailer try and only buy trailers with a galvanised chassis as this will stop corrosion of the trailer. Inspect the whole body and look for welding that has been carried out on the chassis as if there are repairs that have been carried out this usually means that the trailer has been over loaded and or had a hard life this can give away a lot about the general condition of the trailer.

Lights.

Lights are not a major problem as they do no cost a lot of money to replace but there are legal requirements for trailer lights so d check that the lights are legal and work as this can be a reason for you to get pulled over by the police and even get a fine.

We find that a lot of commercial trailers that are been sold second hand are not in a road worthy condition and cost a lot of money to put right. Whereas the small commercially made trailers such as Erde, Daxara, Maypole, Franc, Noval and Camel trailers are a lot easier to look find fault with and repair but due to the cost of the trailers to buy new and the demand for the second hand trailers a second hand trailer will cost almost as much as a new trailer and a couple of problems can mean you can end up paying more than a new trailer.

For more information about trailer parts and laws please read my other articles.

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Trailer tyre load index

February 25th, 2010

With trailers being designed to carry loads tyres are an important part. There are different tyres including Bias ply, Crossply and Radial tyres. These tyres can have different ply ratings. and it can be difficult getting the correct tyre for your trailer.
Most tyres have the maximum weights in small writing on the tyre but this is not always the

 case.
All Road tyres have load index this is a number usually between 60 and 106 for a trailer wheel followed by a letter the letter is the speed symbol, this is normally marked on the tyre next to the tyre size see the image below.

Trailer Tyre Load Index

Trailer Tyre Load Index

The tyre shown above has 2 numbers the first number is for a single axle trailer and the second number is for a multi axle trailer.
Figures marked on this image are 98/96. 98 represents 750kg and 96 represents 710kg. This weight is per wheel.
Please see the list below for a full list of Load index conversions.

60 = 250kg 61 = 257kg 62 = 265kg 63 = 272kg
64 = 280kg 65 = 290kg 66 = 300kg 67 = 307kg
68 = 315kg 69 = 325kg 70 = 335kg 71 = 345kg
72 = 355kg 73 = 365kg 74 = 375kg 75 = 387kg
76 = 400kg 77 = 412kg 78 = 425kg 79 = 437kg
80 = 450kg 81 = 462kg 82 = 475kg 83 = 478kg
84 = 500kg 85 = 515kg 86 = 530kg 87 = 545kg
88 = 560kg 89 = 580kg 90 = 600kg 91 = 615kg
92 = 630kg 93 = 650kg 94 = 670kg 95 = 690kg
96 = 710kg 97 = 730kg 98 = 750kg 99 = 775kg
100 = 800kg 101 = 825kg 102 = 850kg 103 = 875kg
104 = 900kg 105 = 925kg 106 = 950kg 107 = 975kg
108 = 1000kg 109 = 1030kg 110 = 1060kg 111 = 1090kg
112 = 1120kg 113 = 1150kg 114 = 1180kg 115 = 1215kg
116 = 1250kg 117 = 1285kg 118 = 1320kg 119 = 1360kg

Buy Related parts

Trailer wheels and tyres

Related articles

Trailer wheel offset

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Flashing LED lights on trailers.

January 30th, 2010

Modern cars with complicated wiring systems such as Canbus, can have problems running LED lights. The main one we have encountered is where all LED light flash when plugged into the car.

The flashing is caused by the car system sending pulses to the lights so that it can check for continuity, to check that the bulb is fitted / working and then it will give a fault on the dash. LED’s are so sensitive that they flash with the pulses.

We have encountered this problem where Maypole Plug in system are fitted to a Mercedes. We do understand that this can occur on other vehicles such as the Discovery 3, Iveco and the new Mondeo. We have not yet experienced this problem ourselves so we cannot confirm, but the wiring systems for Landrover, are also manufactured by RDM Automotive the same as Maypole systems.
If you were to buy a Mercedes wiring system it is called a smart system this removes the pulses and looks for a load instead this also can cause another problem with LED lights.

Vehicle specific wiring systems should be fitted due to warranty issues, and advanced towing systems, such as fault diagnostic and TSP. However we have found one way to stop your LED lights from flashing is to use a 7 way smart bypass relay. Manufactures of the cars will not recommend this and state that it can invalidate warrantees on electrics on cars if fitted. This is due to the original wiring loom being damaged. We understand that this cannot always be enforced.

We have tried another way around this and that is to fit a 7 way smart relay after the dedicated system this can be done in 2 ways
1. Fit a second socket on the rear of the vehicle for LED lights, this is run through a smart relay. This can be wired into the back of the existing socket and a power supply can be taken from the battery, this means that no damage would be caused to the wiring loom on the car.
2. If the vehicle is fitted with a charging socket either as an additional ‘S’ type socket or a fully wired 13 pin socket, then a smart relay can be fitted to the trailer / caravan or in a box that plugs into the system.

Please note we have only tried to fit a smart relay to 1 vehicle with this problem and it cured all problems but this is only a guide and we cannot be held responsible for damage caused to a vehicle by following these instructions.

Update 01/02/2010

We have now had chance to try this cure on a 2009 discovery 3 and the flashing indicators were cured.

Buy related parts

LED trailer lights
7 way smart Relay

Related Articles

wiring 7 pin N type plug / socket
Wiring 7 pin S type Plug / socket
Wiring 13 pin Euro plug / socket

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Wiring 13 pin Euro plug

December 4th, 2009

The 13 pin Euro type plug and socket is now fitted on a caravan to supply power to all the road lights and give ancillary power to other systems such as fridges and charging systems, in 1 plug with a secure twist lock. In 2008 this replaced the N type road lighting plug and the S type Ancillary plug on all new caravans. Converters ate available to convert either 13pin to 7 pin or 7 pin to 13 pin

Below is the wiring diagram for this plug and socket.

Wiring for 13 pin Euro caravan and trailer electrics

Wiring for 13 pin Euro caravan and trailer electrics

Pin No. Colour Function Cable dia
1 Yellow Left Indicator 1.5
2 Blue Fog Light 1.5
3 White Earth 2.5
4 Green Right Indicator 1.5
5 Brown Right tail / Side light 1.5
6 Red Brake / Stop lights 1.5
7 Black Left tail / Side light 1.5
8 Pink Reversing Light 1.5
9 Orange 12v Permanat power from battery 2.5
10 Grey 12v ignition on (battery charging or Fridge) 2.5
11 White/Black Earth for Terminal 10 2.5
12 White/Blue NOT usually used 1.5
13 White/Red Earth for Terminal 9 2.5

Due to Pin 12 not been used 12 core cable is usually used

Other wiring Diagrams on this site are listed below

7 Pin ‘N’ Type plug and socket
7 pin ‘S’ Type plug and socket

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Trailer wheel Offset

December 3rd, 2009

When purchasing trailer wheels there are a few important dimensions you will require one of these is the offset this is the measurement from the centre line of the wheel to the face that bolts to the hub.

This can cause real problems if you have what is known as a centre nave wheel ( offset = 0 ) with a wheel with an offset this can make the tyre rub on the side of the trailer.

When you have larger weight axles the offset can cause problems with the wheel bearings as when a hub is designed the bearings are designed to accept the centre of the load in a position between the bearings if the offset is incorrect this can put too much load on a bearing and reduce its life.

Some wheels have the offset marked on it as you read the text on the rim you would get an ET and a number this number is the offset distance in millimetres.

if there is no marking this can be worked out quite easily.

Work out your trailer wheel offset

Work out your trailer wheel offset

There are 2 ways to work out your offset for your wheel.

Method 1

(B-A)/2

This is the measurement from the rear of the rim to the hub face – the measurement from the front of the rim to the hub face divided by 2.

100-40 = 60 /2 =30mm.

Method 2

Measure the total width of your wheel on the image above this is 140mm 40+100 (A+B).

Divide this by 2 which gives 70mm then subtract the measurement from the front of the rim to the hub face (40mm)

On the wheel shown above this would come to 30mm

For a large range of trailer wheels please goto our Ecommerce site

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7 Pin ‘S’ type caravan wiring

November 29th, 2009

The 7 pin S type plug and socket is usually used on a caravan to supply power to the reverse light and give ancillery power to other systems such as fridges and charging systems. This has been replaced in 2008 by 13 pin Euro plugs on all new caravans.

Below is the wiring diagram for this plug and socket.

7 pn trailer wiring

7 pin 12 S wiring diagram

Pin No. Colour Function
1 Yellow Reversing Light
2 Blue 12v ignition on (battery charging)
3 White Earth for terminal 2 and 4
4 Green 12v Permanant (Direct from battery)
5 Brown Revesing sensors (usually spare)
6 Red 12v ignition on (Fridge)
7 Black Earth for Terminal 6

Other wiring Diagrams on this site are listed below

7 Pin ‘N’ Type plug and socket

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Maximum trailer towing weights

November 28th, 2009

When Building a trailer the most Important thing to take into consideration is the Gross weight of the trailer as this affects the Suspension, Wheels and Tyres and the coupling, as your trailer is only as strong as the weakest of these parts.

Legal trailer weights

The Maximum Gross weight for an unbraked trailer is 750kg

The maximum Gross weight for a braked trailer with Overrun brakes is 3500kg

Not all Vehicles can tow the above weights please read your Log Book for your cars maximum towing weights

 Please check your driving licence before towing. From 1997 Entitlement to tow trailers was withdrawn from all new Licences.  An additional driving test can be taken.

All the above weights only apply to towing on public highways

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Maximum Legal Dimensions for a trailer

November 28th, 2009

Building a trailer there are a few laws regarding the size and capacity to be legal to use on Public highways.

Dimensions

Trailers on towing vehicles upto 3500kg

Maximum length  :-  7m Excluding drawbar

Maximum Width  :-  2.3m

Trailers on towing vehicles over 3500kg

Maximum length                 :-  12m Excluding drawbar

Maximum Width                  :-  2.55m

Maximum Overall length :-  18m for trailer + Towing vehicle

Maximum Height

Trailers have no Maximum height But it is not recommended to exceed 1.7 x the track of the trailer.

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