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Home / Cardiff and it's Bay / On the Water / Trailer suspension unit – repair / replace

Trailer suspension unit – repair / replace

Trailer suspension unit repair is quite simple if the trailer is constructed in such a way that the unit can be replaced by simply bolting on a new one.

With age the suspension units can sag as the rubber becomes tired and loses its spring often becoming permanently deformed.  Many types of dinghy trailer were constructed with an integrated suspension unit built into the frame of the trailer which can cause a problem.

It is impossible to repair these without destroying the trailer. All is not lost though and there is no need to go to the expense and inconvenience of getting a plate welded to accept a replacement. This can be tricky in itself as welding galvanised steel gives of toxic gases and fumes. So what is the solution?


Trailer suspension unit repair


Well quite simply the replacement unit is constructed in a box section and that whole unit can be clamped to the existing trailer with parts available from Ebay where a vast array of trailer spares are available.

Trailer suspension unit repair - mudguard removal

The trailer suspension unit repair starts with getting access to the trailer axle, remove the mudguards, in this instance they were bolted on with nylock nuts. Then remove the wheels.

Trailer suspension unit repair - original hub

Care should be taken to make sure you get the correct unit. The wheels can be metric or imperial, both are easily available the distance between the studs being either 4 inches or 100 mm. The imperial ones have a grease nipple and the wheel will have a small cut out to accept that nipple.

Trailer suspension unit repair - arial view

The replacement effected here involved the trailer suspension unit repair with the hub housing the bearings. The cost of the whole unit was only a little more than the suspension unit only and it meant that the finished product had not only a new suspension unit but new bearings as well.

Trailer suspension unit repair - cut axle

The whole of the old unit was cut away with an angle grinder, though a hacksaw would also do it but would simply take longer. You can see in these photos how the rubber insert has collapsed and also how the suspension unit works with the rotation of the backward trailing arm squeezing the rubber insert as the load is applied.

Trailer suspension unit repair - worn unit

The replacement unit is the same size box section as the original, in this case 40 mm higher rated units will probably be 50mm, the same procedure can be used.

Trailer suspension unit repair - marking out

In orer for the clamp to pass through the mounting plate on the replacement unit 4 new holes need to be drilled, this is quite easy as the plate is mild steel. Check that the plate wont interfere with the trolley wheels, if it does the you will need to trim the plate a little, in this instance it was a little tight but perfectly acceptable.

Trailer suspension unit repair - drilling

Mark out where the holes need to go by offering it up to trailer, Check to see that the holes that will receive the clamp wont interfere with the mudguard bolts and nuts, its easy to move them a little if they do. You need to drill a pilot hole, as the clamp will be a snug fit over the box section, there is a seam weld where the plate meets the box section, drill the pilot as close as possible to that seam so that when the hole is opened up it is adjacent to the box section.

Trailer suspension unit repair - offering up

Once the holes are drilled assemble the trailer suspension unit with its clamps loosely to ensure everything lines up. Then as long as it is OK you can prime and paint the newly drilled holes.

Trailer suspension unit repair - repainted

The trailer suspension unit repair all hinges on the square U bracket show, this one has a 40mm internal dimension and is long enough with the thread to span both square sections of steel. For additional security it has a closure plate and is nickel plated. Trailer suspension unit repair - square U bracket

Once the  trailer suspension unit repair has been assembled its simply a case of bolting it all together securely remembering to use the washers and nylock nuts to ensure they don’t work loose.

Trailer suspension unit repair - bolted up

Then add the wheel, the wheel nuts have different ends one end is rounded the other flatter, the rounded end is designed to match with the dished depression in the wheel to increase the friction between the nut and the wheel for security.

Trailer suspension unit repair - finished side

The final stage is to replace the mudguards and turn the trailer over of course, note that the trailer sits with hugely increased clearance between the wheel and the mudguard, Remember to add the central wheel caps covering the hub tapping them on with a block of wood between the cap and the hammer.

Trailer suspension unit repair - completed job

This trailer suspension unit repair will mean the trailer sits about 40mm 4 cm higher than previously in its unladen state.

Trailer suspension unit repair - completed with trolley

Finally remember to fully tighten the wheel nuts so that you don’t damage your excellent work losing a wheel and whilst on wheels, check tyres for wear and cracking. Inflate the tyres as they are prone to losing a bit of air and the job is finished.



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