Acceptable Axle Run Out?

OK technical types!

50mm karting axles.

What would you accept as run out when measuring the axle on furthest outward edge possible?

0.002", 0.010", 0.020" , Other

At what point do you know it will induce a vibration or negative handling characteristic?

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We had a few that were. 008 out and I was advised not to use them. Probably fine for club racing still. Interested to hear what others think!

I’m interested as well. I know my axle is out a little. Still learning, is there a at-home (ballpark?) way to measure without removing?

dial indicator might work

I have all the axles loose and I borrowed a truing stand from SwedeTech Racing. I then have a dial indicator on each end.

If I was to have the axles in the kart, I would use something like this -

I’ll preface this by saying I’m not at all an expert on this subject, but I use a clamp-on dial indicator mount from Harbor Freight, with an upgraded dial indicator. This allows it to be measured and corrected while still in the kart.

If I have axles with a very small bend then I will usually try to get them back to around 0.002-0.003” runout. Pretty low-tech solution, but I accomplish this by identifying the “high spot”, sliding on a long hub, and hitting it mightily (think two-handed Thor) with a dead blow hammer. Pretty amazing how softer axles will respond much more than stiffer axles…

I’ve had axles measure around 0.008” off and they’re ok to use, but I wouldn’t race on anything more than probably 0.005”.


For all your axle bending needs. But in all seriousness .010"-015" of runout at the end of the axle is about as much as I would tolerate. At that point it tends to be a noticeable vibration. Last thing you want is to shear an axle and crash over a couple hundred bucks.



When I asked the person that repairs my axles, he indicated that 0.005” when measured at the inboard edge of the outside axle keyway was the limit of recommended to use.

He said he measures at the inboard edge (where fully round) of the keyway because people have a tendency to smash/mushroom the ends when pounding axles to remove them which will throw off the measurements.


Wow that’s really tight. I’m not sure the concentricity of the hubs bores would be held that tight. We are talking a human hairs worth of runout at 6-8” from the bearing.

I think he was using a tighter measurement since his recommended measurement place is inboard of the hubs. Typically I’m more lazy and just sending them in if I can see a visible wobble or feel it on track.

Thank you for the info Evan.
For those that don’t know, Evan is an accomplished racer and his local track is high speed - New Castle Motorsports Park.

If anyone other than me was wondering what the heck axle runout is:

" Runout is a condition where the centerline of the coupling or shaft has deviated from its true axis of rotation . To measure coupling or shaft runout, it is common to use a dial indicator with a standard magnetic base. … Then mount the dial indicator on the surface to be checked"

Not sure why the photo chosen by Google seems to show a gauge measuring piston gap or something.

So total runout would be high spot minus low spot? Or high spot minus average/true center? Does this question make sense…

When you refer to the concentricity of the hub bores, what are you relating the concentricity to? The bore relative to the shoulder that the wheel aligns on?

Great question. I don’t know the right answer. I write it down as full range or total indicator travel.

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Yes. As they are just mass produced parts most likely coming out of an automated lathe with automated work holding, I doubt the concentric between those two surfaces is held to within a thou or two. Let alone you are taking something with internal stresses and cutting a big slit in it to make installation easier.

Prior to cutting the slit, I would definitely expect those 2 surfaces to be concentric within a couple thou. But like you said, once the slit is cut, it’s definitely going to spring open.

Total “sweep” of the dial indicator, so yes high minus low is the runout.

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The end of the axle sometimes isn’t always round, so I use a hub to measure total indicated run-out (TIR).

I finished a race on 1in runout. I’d say you probably wanna keep it below that

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