Bearing Dust Cap "Falling Off"

[Bob Miller]

Late last month, while parked in Quartzite, I noticed that one of the bearing dust caps was missing on my 1973 Hunter. The bearing had been repacked about 6 months ago and the cap was driven on tight and was seen in place before heading for Q some 200 miles earlier.

I was able to find a pair of new caps and quickly drove a new on one.

Last week (about 350 towing miles later) I was in Joshua Tree NP and the same cap was again missing. Fotunately I now had a spare and popped it on, again a very tight fit, and drove another 100 miles home.

And YES, the new dust caps are a very tight fit, even tigher than the opposite side that never comes off.

Has anyone else had this experience? Ideas???

[Eddie Longest]

Check your hub closely it could be cracked.
Eddie

[mary and bob]

Is the dust cap deep enough that it doesn't contact the end of the axle. Is the bearing adjusted so that there is not excess play. I would use a prick punch and make several marks around the inside of the hub where the dust cap sets to help keep it in place. This is common practice to correct a loose fit as the pointed punch will raise the metal around the indentation that it makes. I did read though that the dust cap fits tight, so it is a mystery why it comes off. Another solution that doesn't really correct the problem would be to find something like a plastic container that will slip over the hub and put a hose clamp on it. If the dust cap comes off at least it won't be lost and dirt won't get into the bearings. Also does the new dust cap fit deep enough into the hub. I think there are several size dust caps available that are close in size. Excess grease in the hub might build up pressure but would more likely force it out the seal.

[stevebaz]

I would be suspect of something getting hot. Tear down and repack the bearings. Maybe adjustment nut too tight causing heat or brakes dragging if you have them. Eithor way something is amiss.

[David B.]

If after following all the suggestions and still not find anything causing this condition, try using loctite on the cap prior to driving the cap back on.

[Bob Miller]

Good Answers, but here's an update:

New bearings and seals less than a year ago
The cap fits so tight that it's actually hard to get on and off
No brakes
Checked both hubs for heat build up after a 100 mile drive, both cold, no difference
Same wheel threw a new, clip-on, 13" Moon hubcap off in less than 50 miles about 7 months ago.
Tires are new & were balanced, but wheels are ancient. I am beginning to suspect something with the wheel causing vibration.

[Carol H]

Bob, I had one of my caps damaged this summer that needed to be replaced. I had troubles finding the right fit as well. In my effort to replace them I discovered a couple of things. Caps that had slightly rounded top would not go on all the way so it had to be a flat top cap as the original was. I actually had to buy two different sets of flat top style caps to get one that fit even though both brands claimed to be for the correct hub. They all look to the naked eye to be the right cap when put up against the one old cap I still had ..... but with calipers on them they are all just *slightly* different in total width. Even the one I did get on took more effort than the old one so I'm wondering if it was because the old one had been taken on and off so many times over the years it was just worn down a little bit more......

[Bob Miller]

Good point Carol.

I will first measure them and, if they "seem" the same, I will swap the left and right caps and see what happens. Needless to say I will carry a couple of spares during the trial period.

[stevebaz]

Take it for a ride on the freeway in the truck lanes and have someone in another car parallel you and look at the wheels while running. They may see what you cant.

[Thomas G.]

It might be useful to jack up the wheel and measure radial and lateral run out of the tire and wheel. If you don't have a dial indicator, use a screw driver in close proximity to eyeball it.

[Rob and Linda]

Another trick that nearly always works is to stretch a piece of a zip-lock bag over the cap before banging it back onto the hub... even kitchen plastic wrap (think 'Saran Wrap') might even do the trick.

Rob

[Mary Ann in MN]

Where can I buy a new cap/cover for my wheel bearing? I had new tires put on last year. One cap fell off. The guy tapped it back on. It's been covered all winter but taking the cover/tarps off and I started washing it, I see that the cap is gone again. I only made one trip after the new tires so it must have fallen off then. Thanks for any help.

[Carol H]

You should be able to obtain a new hub cab at any RV repair shop or general trailer repair.

[War Eagle]

Once while looking for a pair of "Bearing Buddy" dust covers (the kind you can fill through a grease fitting and a coil spring keeps pressurized grease against the bearings) for a submergable boat trailer, a CarQuest manager explained to me that not all bearing dust caps are created equal, and quality-made caps will list their diameter in 1,000ths of an inch. Bearing Buddys are made of thicker cast metal (less likely to distort if/when hot) and sit a bit deeper into the hub. You might want to mic your hubs and fit a pair of them to your trailer to see if that helps (and make it easier to grease your hubs, too). Problem is, they are more expensive, so if you lose one of them, you've lost a few more bucks. Oh, and if you haven't been already, try using a solvent to clean all the metal surfaces to remove any remnant grease that might be making the contact surfaces slick. Dale

[Jack L]

I carry an extra cap, bearings, grease seal and retainer clip or cotter pin and some grease at all times.

[Glenn Baglo]

Originally Posted by Jack L

I carry an extra cap, bearings, grease seal and retainer clip or cotter pin and some grease at all times.

And a supervisor?

[Borrego Dave]

Does anyone know if Bob ever found the reason for his dust caps falling off?

[Fallon]

Don't use bearing buddies on anything but a trailer that gets dunked.

Bearing buddies (and EZLUBE axles) require a much beefier double lipped inner seal. A normal seal is designed to keep crap out, not keep grease in. If you pump grease into a bearing buddy, the weak grease seal will let grease out & onto your brakes. This happens even on EZlube axles with the stronger double lipped seal if you don't use them right or what not.

[gordon2]

Originally Posted by Fallon

Don't use bearing buddies on anything but a trailer that gets dunked.

Bearing buddies (and EZLUBE axles) require a much beefier double lipped inner seal. A normal seal is designed to keep crap out, not keep grease in. If you pump grease into a bearing buddy, the weak grease seal will let grease out & onto your brakes. This happens even on EZlube axles with the stronger double lipped seal if you don't use them right or what not.

You mean like this?
Of course most of us use what comes with the trailer, be it EZLUBE, Bearing Buddies, etc.

[Fallon]

Originally Posted by gordon2

You mean like this?
Of course most of us use what comes with the trailer, be it EZLUBE, Bearing Buddies, etc.

Exactly. Lubricated brake pads aren't a good thing.

In theory you could use bearing buddies as dust covers if they were tall that fit as long as you never pressurized them with grease. But going with your people just use what was on the trailer concept, that would be a bad idea.