Axle bearing maintenance

With traditional axle bearings that don’t have seals/covers how do you handle maintenance for the best bearing performance and life?

I was told/taught to lube the bearings with tri-flow before each run which I think is pretty universally agreed on. What I’m less sure is between-event maintenance. I was told that after a race weekend to spray/flush out the bearings with brake cleaner, let them dry, then Re-lube with tri-flow to prepare for next event.

Lately I’ve wondered if the brake cleaner is the appropriate thing to do? I will say it flushes a lot of dirt and nasty stuff out but also seems like it’d potentially take more protection out than would be ideal. Would it be better to try to flush with air alone or potentially blast with WD40 and/or aerosol tri-flow?

I’d appreciate any feedback from the experts.

I like to use wd-40 and an air nozzle on a compressor. Spin the axle and shoot wd in while blowing air. You will see grime come out. Keep doing until it starts to run clear. Finish off the same way with tri-flo

Be careful with brake cleaner. Although it is an amazing cleaner, it is extremely dry and can wreck bearings if they aren’t lubricated enough. Bryan is right on with using WD-40 on the bearings. Not too much Tri-Flow or your bearings will pick up every piece of grit and grime. Cheers.

WD40 is barely a lubricant. But on the other hand I’m not sure it really makes a difference what you use in there, within reason. Don’t even start me on spinning the wheels to “test” it :joy:

When I first started I used 3in1 oil.
Now I use lithium spray grease.
I think I’ve even used motor oil at some point :astonished:

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Another reason to be careful with brake cleaner is that it will take the paint of the chassis.

We remove the rear axle and front hubs from the kart. Clean them out with brake cleaner then compressed air. Then I spray them with tri flow unless it’s going to be more than a week before we race again. Then I throughly spray them with wd40. Then the Thursday or Friday night before we race I spray them with Tri flow.

WD-40 is not a full on lubricant. It was primarily made as a water displacement thus the term WD. Works good as a flushing agent but should not be used as a lubricant without something else before going on the track. We used strictly WD when i was a kid, it sure made those bearings spin smooth for a bit but would wear out the bearings very quickly.

Exactly. Like I said how I use it to clean out the grime with an air nozzle then finish with tri-flo or an oil that isn’t solvent based.

Should the rear bearings spin free (my axel is off). I can hear some grinding and am worried that they are either now grimey or I damaged working it off the chassis?

Some day, someone will wise up & make sealed 50mm bearings & cassettes with zerk fittings.

a bunch of 50mm bearings come sealed. most people remove the seals and flush all the grease out.

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Along with lube selection, there’s differing theories on how much it matters that they spin freely… as well as what spin freely means.

That said, grinding is generally not good.

Try cleaning the bearing races out with a solvent of some sort and/or compressed air.

Once they are clean, assuming the grinding noise goes away, check them for play.

I’d prefer them. I don’t subscribribe to the theory that a “free” spinning axle is indicative of any performance advantage. The viscocity of grease is of academic consequence when the wheels are rolling at speed.

I think you are correct with respect to grease. However, it’s worth noting that the greases and oils we use are non-newtonian and their viscosities tend to converge as the contact rate (relative ball speed at the ball-surface-interface) increase. Which is to say that greases are less efficient at lower speeds. The other issue (which may not be an issue for karts) is that sealed-greased bearings do not reject any metal wear particles as well as oil-lubricated, unshielded bearings. I would be interested to see some testing with the various lubes to see how significant (or not) the various trends are.

I know that other motorsports have gained significant efficiencies by changing bearings and the way they’re lubricated - ceramics and fancy engineered lubes.

anyways, most kart retailers have these photos for their axle bearings:



One thing I’ve thought about doing but never have is re greasing the bearings. I’ve noticed on some brands of bearings there are small, just big enough for a wd-40 red straw on the outside of the bearing. Ive used those holes to flush with wd-40 then oil with tri-Flo and reinstall. But what if I could find a needle attachment for a grease gun and shoot in some nice low friction high temp grease. This way you wouldn’t mess up the side covers from removing them trying to reinstall.

You can get ceramic axle bearings for karts too. Opinions vary of course.

I use white lithium spray grease as a lube and just send it.

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I hope this is a related and relevant question, but how tight should the cassette pinch bolts be? Another way to phrase it, how easy should it be for the outer races to rotate angularly in the cassettes?

Mine are just snug enough they don’t back out. Not sure if this is right or not but works for me. I also recheck every few runs also since I don’t crank them down.

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I usually add a little “blue” threadlocker to the bolts and leave the bearings loose enough in the carriers such that they can move around a little with some force.

I’ve never actually tested it. But I suspect when you sit in the seat the frame sags downwards a little, forcing the bearings out of square with the axle. Leaving the bearings some ability to move around let’s them stay square relative to the axle.

The other thing you can do is leave the carrier pinch bolt loose the sit in the kart and lock them up.

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Another thing to look out for when tightening the bearing carriers is bind. The bearings are a tight tolerance and it doesn’t take much torque on the carrier clamp screws to distort the outer race and cause a bind. When I got our used kart last year the axle didn’t spin freely. I thought it was the bearings. But the previous owner had cranked down the screws tight. I backed them off and the bearings spun free.