Clive Marsh explains why many trailing sailors may have the wrong type of boat trailer bearings and don’t know what is happening inside their hubs…


Being able to easily trail your little boat to new cruising grounds is a great feeling. Many owners of cruising yachts simply don’t get the time to go far from their moorings and their boats become day sailers from the one location.

But the trailer-sailer can be taken to new haunts around the coast and to inland lakes and waters that are not accessible to cruising yachts.

I like to book into a good hotel or boarding house and day sail. My wife certainly prefers this to being stuck at an angle on a damp mooring up a muddy creek. Since trailer sailing I have got to know many ports and inland waters.

For a working man with just a few weeks holiday each year a fin keel cruising yacht on a marina does not give much opportunity to visit many new places, even if the weather window allows it. So for me you can’t beat a good trailer-sailer.

Now, for a trailer-sailer to be safe and enjoyable the trailer and launching arrangement needs to be well designed for the boat and to work well. Skimp on the trailer at your peril.

Article continues below…

You need a first-class trailer and for this reason even a dinghy with a purpose-built trailer can cost more to buy than a used small cruiser. But the savings in marina, berthing or yard fees enjoyed can be significant. Mooring, harbour or haul out fees and the rest for a small cruiser on the South Coast can easily come to more than £3,000 a year.

Beware wet boat trailer bearings

For lighter dinghies a combination trailer/trolley is often used. This type has a separate launching trolley that slides off the road base. This means the boat trailer bearings on the road trailer will not get wet and will last longer. For heavier day boats, however, it’s normal to launch the boat directly from the road trailer and we now enter the world of wet bearings.

You really don’t want to get your bearings wet, especially in salt water. So to avoid this happening we have invented swing back trailers and break back trailers which might enable the boat to be launched and recovered without the need to immerse the wheel bearings.


Swing cradle trailer

However, there will come a time when a wave gets you or a careless tractor driver immerses your trailer. This is when you need to pay attention to the type of bearings you have on your trailer.

Another word of warning, never assume when you buy a second hand boat that the bearings are OK whatever the seller tells you. He or she may have the best of intentions but I’ve been caught on many occasions and found myself changing bearings on the side of a busy British A-road in the rain.

The best type of boat trailer bearings

For me the best type of boat trailer bearings are the simple tapered variety. I like these because I can easily strip them down and change them on the roadside in just 15 minutes. It really is simple. It is even easier to just replace the hub with new bearings and take the old hub and bearings home to service.


Trailer with easy recovery roller units at rear

The huge advantage of these types of bearings are their simplicity to inspect and service on site with no special equipment other than spanners, pliers, hammer, grease and wheel nut remover and perhaps a bearing puller, although I have never needed to use one.

Another type of bearing is often described as ‘sealed for life’. These are similar to those used on caravans. I don’t think they’re suitable for marine use if there is even a small a chance they will be immersed in water. The reason for this is you can’t easily strip and inspect them on-site.

They’re normally serviced in a garage with a bench press. I thought they’d be fine on my swing back trailer which did not need its hubs to get wet. Unfortunately, the inevitable immersion occurred.

A short time after immersion I got the garage to check them out. One set was completely shot and the other side was well on its way. Salt water had got in through the back and done the damage. So if you have sealed for life bearings make sure you don’t immerse them and if you do find out how they can be serviced.

There is another type of bearing that originated on the Continent. These have a clear cover and are filled with oil rather than grease. With these it is possible to look through the clear hub cap cover and see the oil level and also whether there is water visible in the front of the chamber.

This has the advantage of saving the bother of removing the hub cap to inspect the lubrication level.


Combination trailer/trolley

Boat trailer bearing protection

Then there are things that can be done to help protect your boat trailer bearings such as always letting your bearings cool before launching, keeping the bearings adequately packed and using bearing hub covers. I used the words ‘adequately packed’ because over packing with grease can have unwanted consequences.

Over greasing may lead to high operating temperatures when towing which can lead to collapsed seals. Also the resulting degradation of the grease can result in accelerated wear of components. So, my solution is:

  • Use simple, easily removed and serviced tapered bearings
  • Avoid immersion
  • Check, re-grease or replace if they do get immersed
  • Check regularly depending on mileage even if not immersed

Red hot hub

Probably the worst bearing experience for me was travelling south down major A-roads and across the Dartford Crossing. The seller of my new boat, who I know well and would never knowingly sell a pup, had assured me that the boat trailer bearings were fine and good for the 100-mile journey.

Off I went with my chum, Maurice, riding shotgun and with a supply of spare bearings. Looking in the wing mirror he noticed that the nearside wheel did not look right.


A fin keel yacht being towed. Photo: ZarkePix/Alamy

I pulled onto the hard shoulder to find that the hub was red hot and that the bearings had disintegrated. Removing the old bits of bearing was not easy and parts had become welded to the axle. In order to get the new bearings on required filing metal off the axle.

We hadn’t brought a file but did have a trusty Swiss Army penknife with a nail file. This was a long and slow job mainly for Maurice in the rain and with traffic hurtling past at speed it was dangerous. We managed it and limped home down to the South Coast.

A few years later another seller convinced me that his bearings were fine for the 120-mile journey home and I had a similar experience at night with my wife as passenger who had hoped for a nice day out. Dinner was cancelled.


A boat should be balanced on its trailer with sufficient head weight on the towing eye. If your rig does not have sufficient head weight try moving objects in the boat forward

The one good thing about these experiences is that I can now strip and change trailer bearings of the tapered variety in a few minutes and do so regularly. I always know the state of my bearings. Do you?

Useful trailer sailing advice

If you want advice regarding trailer sailing a good site to join is the Dinghy Cruising Association page on Facebook. Members on here tow and launch all sorts of boats from one end of our island to another and are only too ready to share their varied opinions which you can compare.

This article has concentrated on boat trailer bearings. The website will explain the law regarding towing, if you need brakes on a trailer and what weight you can tow.


Cornish Shrimpers on trailers by the Camel Estuary at Rock, looking towards Padstow in Cornwall. Photo: Photo Cornwall/Alamy

Getting trailer brakes wet is another problem and for this reason I always now make sure that my car/trailer/boat combination is within the part of the law where brakes are not required.

Keeping things as simple as possible means more time on the water and less time on maintenance. The law concerning the ability of a driver to tow has also recently changed and you need to check this out.

Also, make sure your insurance covers you as a driver and also any modifications such as the addition of a tow bar that have been made to your tow vehicle.

Vyv Cox

Vyv Cox

Boat trailer bearing technicalities

PBO expert Vyv Cox on rolling bearing materials

The vast majority of rolling element bearings are manufactured in steel to SAE 52100, containing about 1% carbon and 1-1.5% chromium. Heat treatment through-hardens this alloy to a high hardness, between 60-64 Rockwell C, with very low ductility.

Any impact, particularly during fitting, is likely to result in fracture. The elements, either balls, straight or tapered rollers, are given a slightly higher hardness to improve their fatigue resistance.

Bearings in AISI 440C are produced for more corrosive conditions. This martensitic stainless steel also contains about 1% carbon but the chromium content is increased to 18%.

The hardness achievable is rather less than for SAE 52100, around 58-60 Rockwell C. The load bearing capacity of bearings to this standard is thus somewhat lower. Corrosion resistance is improved over the basic material but not sufficiently for good resistance to seawater.

A third material for bearings is AISI 316, an austenitic stainless steel. This has good corrosion resistance in seawater but, as with all 300 series stainless steels, it cannot be hardened by heat treatment. Its load bearing capacity is thus low and mainly limited to low speed use.

So there’s no easy answer to immersion in seawater, immediate flushing with fresh water being the optimum, although use of AISI 440C may well give benefits.

Why not subscribe today?

This feature appeared in the July 2022 edition of Practical Boat Owner. For more articles like this, including DIY, money-saving advice, great boat projects, expert tips and ways to improve your boat’s performance, take out a magazine subscription to Britain’s best-selling boating magazine.

Subscribe, or make a gift for someone else, and you’ll always save at least 30% compared to newsstand prices.

See the latest PBO subscription deals on