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Why do trailer wheel bearings wear out?

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English Dave View Drop Down
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Post Options Post Options   Quote English Dave Quote  Post ReplyReply Direct Link To This Post Topic: Why do trailer wheel bearings wear out?
    Posted: 01 Sep 08 at 10:59pm

OK, so I've finally got round to doing some maintenance on the trailer. This year it has done a few long trips. Ballyholme to Kinsale (600 mile round trip), Ballyholme to Gosport (1100 miles) and Ballyholme to Galway (400 miles). On the way back from Gosport the left wheel strted to vibrate and a kindly mechanic said I would be lucky to get another 500 miles out of the bearing. Since then I've done another 800 miles but enough is enough and I am in the process of replacing both axle hubs.

But why do they wear out. My car has done 100k miles. Admittedly it has 17" wheels rather than 10" but that's still a lot more rotations than the trailer wheels have done. The loading on the car is higher per wheel than the trailer. The trailer stays dry (ie I don't use it to launch). I keep the tyre pressures good and am generally kind to it when driving. So why does my trailer hubs need replacing when to replace car wheel bearings is almost unheard of?

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Post Options Post Options   Quote Scooby_simon Quote  Post ReplyReply Direct Link To This Post Posted: 02 Sep 08 at 12:35am

cheap trailer bearings vs decent car bearings!

 

 

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Post Options Post Options   Quote laserboy404 Quote  Post ReplyReply Direct Link To This Post Posted: 02 Sep 08 at 9:15am
Trailer bearings need greasing and regular maintenance whilst car bearings are sealed units running bathed in oil.
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Merlinboy View Drop Down
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Post Options Post Options   Quote Merlinboy Quote  Post ReplyReply Direct Link To This Post Posted: 02 Sep 08 at 9:18am
I'm sure i wouldnt be the only person who would buy a better wuality bearing set if i knew where to get them from.  Also what are those Powder coated/ Painted pressed steel wheels all about!!!  They rot in a couple of years!! (unless you take them off or wrap them in bin bags.  I think a trailer company should offer some longer life parts.  They would be worth the extra money as trailer breakages are NOT funny!
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Post Options Post Options   Quote Rupert Quote  Post ReplyReply Direct Link To This Post Posted: 02 Sep 08 at 9:50am

Alloys on your trailer? And a spoiler...

Agree about the wheels, though I suspect decent ones would just make them more likely to be nicked.

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Post Options Post Options   Quote Medway Maniac Quote  Post ReplyReply Direct Link To This Post Posted: 02 Sep 08 at 5:28pm

If the hubs still need greasing, it would at least be nice if they had grease nipples like they used to.

Are we really expected to disassemble our hubs and re-pack with grease every couple of years? "That's hard", to quote Bevis & Butthead, who epitomise the modern approach to such things, after all.

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Post Options Post Options   Quote NeilP Quote  Post ReplyReply Direct Link To This Post Posted: 03 Sep 08 at 12:48pm

Trailers only tend to get very intermittent use. This causes several problems. When the bearings cool down after running, they draw in air, which has moisture in it. In cars with traditional taper roller bearings like a lot of trailers, this isn't a problem as the regular heating cycles tend to drive out the moisture. Trailers sit on the drive or in the boat park for weeks, sometimes months, between uses so the moisture starts corrosion. Trailer wheels are not usually balanced, which puts extra strain on the bearings. Most people don't adjust or clean/repack their bearings so the grease they run in is usually filthy and ancient. Add all that to the fact that most trailers in the UK run on 8 or 10" wheels, so the wheels rotate much faster than your car wheels, and a lot of people tow at stupid speeds, and they are bound to wear out quickly

The next point I have no real evidence for, but I believe that most people run their trailers with far too much pressure in the tyres. Think about it this way: the air in the tyre is there to support the loadand stop the tyre from deforming too much and overheating. An old Mini runs similar size tyres to a trailer with 10" wheels, and runs 26psi tyre pressures. Just on the weight issue, a loaded trailer with say 100 kgs of boat and rig might weigh 200kg, so well less than half of a Mini. Then there's the fact that the Mini's tyres also have to cope with power, steering and braking loads which will put loads more heat into the tyres. I reckon a trailer with the average dinghy on it shouldn't need much more than 18-20 psi for the tyres to work correctly. Anyone have any proper data on this? Don't forget that the pressure marking on the side of the tyre is a maximum at max load, so an absolute limit, not a service value.

If you want better bearings, take your old ones to any bearing supplier and he should be able to pull a set of Timken bearings of a shelf for you.

Neil

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English Dave View Drop Down
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Post Options Post Options   Quote English Dave Quote  Post ReplyReply Direct Link To This Post Posted: 04 Sep 08 at 11:20pm

Great replies - many thanks.

Adding to the problem is that many cat trailers do not a have any identifiable manufacturer markings. Mine has a home made wodden box in the middle (which is fab can carry 2 Hurricane's worth of sails, rudders and even spinnaker chutes. Trouble is that the wheel fit to a 115mm pcd (FGI) and the spindle is 20mm. I have source a replacement hub in England but the suppliers maintain that Trelgo do not make boat trailers. The hub is in a Parcelforce lorry en route so we shall see if it fits.

Maintenance of the hub would be a lot easier if you could remove the hubcap without a lot of difficulty. I have had to hacksaw through the bolts securing the mudguard to remove them in order to get an angle on the hub cap that I can tap with a screwdriver/hammer combo. And if the hub  fails while the boat is on op and your are on the M4, say, it's just not funny.

Interested to hear views on tyre pressure. If memory serves this was a topic on which I first joined the forum. I am an advocate of using hard tyres (30+ psi) to avoid hysteresis in the rubber, leading to tyre failure (also not funny). The suspension units should be able to cope on their own without having the tyre set up as a bouncy castle. However, this is just an opinion, based on my engineering background but without any real practical experiece beyond my own towing stories.

My new hub is costing me 22 + carriage which is for nothing (I'll do both sides if the first one fits). And if you can change it easily, it is worthwhile. The problem is when you run into problems halfway to a regatta with the boat on top. The it become a nightmare

 

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tack'ho View Drop Down
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Post Options Post Options   Quote tack'ho Quote  Post ReplyReply Direct Link To This Post Posted: 05 Sep 08 at 12:47am

22 for a new hub...mmmmmm remind me again how much the same unit for a car would be???

Think the answer may be out there somewhere

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Post Options Post Options   Quote NeilP Quote  Post ReplyReply Direct Link To This Post Posted: 05 Sep 08 at 9:49am

Tre pressures are not an exact science, but running them too high is just as bad for the tyre, just in a different way. If you run them too soft, the edge of the tread and the sidewall will overheat, too hard - and 30 psi IS too hard - and the centre of the tread will overheat, causing premature failure of the structure. Excvessive tyre pressures also transmit more of the shock loads from the road into the bearings, hubs, trailer and ultimately boat. The tyre is part of the suspension system and pressures have a significant effect on overall spring rates. In the days when I was involved in motorsport, we used tyre temperature measurements to determine correct pressures by comparing readings across the tread and adjusting pressures to get them even. 99 times out of 100 we started too high, and given the easy life trailer tyres have in terms of dynamic loads, I still feel most people run them too hard. Just my opinion, though, and I may well be wrong. I've never had a bearing fail on any of my trailers, so I may just have been lucky!

Neil

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