MTFCA Forum

I am getting ready to rewood some early wheels and have lined up some rear hubs and clincher rims from my stash to use because I want o keep using my car while the wheels are out being done. My question is how can I determine if the rear hubs that I have are good enough to use. The key ways look fine but I am concerned about the taper. I am hoping to not need shims when I get the wheels back. The axles on the car where the new wheels will be mounted were replaced about 2 years ago so presumably if the tapers on the hubs I plan to use are not worn no shims would be needed. How can you determine if the tapers are worn?

At one time, "Prussian Blue" was used for such purposes. It may still be available. To use it, first clean everything thoroughly, then evenly apply a very thin coat of the Prussian Blue to the axle taper and carefully place the hub on it. Leave the key out, and run the axle nut down and tighten it two or three rounds, then back it off and withdraw the hub straight off the axle. Do not rotate the hub. Ideally, most of the blue will be squeezed out in an even pattern, indicating full or nearly full contact between the axle and the hub. Uneven contact will be shown by bare areas and/or areas with a lot of blue left on them. You could do a similar check by spraying a very light, even coat of spray paint on the axle, then proceeding as above. A good straight edge, like a small steel rule, could also be used to check the axle. Anything applied to the hub and axle should be completely removed before final assembly. How far the hub goes on the axle can also indicate the condition. I think you'd need to assemble the hub and axle on the car and torque the axle nut to check how far the hub goes on the axle.

You can take an old axle end & insert into the hub to use as a rough wear gauge. Mark where the hub & axle meet as a comparitor to a known good hub. The further in the hub it goes, the more wear. Also look @ the taper fit. The test axle should have no wiggle in the hub. Your existing axle tapers may (probably/do) have wear also. Thats a fixed issue unless you are willing to break down the rear end.

Thanks, I did do the Prussian Blue test and got good overall coverage on what appears to be a good axle. My concern was how far on the taper the hubs go. One hub goes about a 1/16th" further than the other on the test axle but I have not torqued them on. They both seem to sit well on the taper with no rocking.

Whatever you do, don't lap them in. If you do, chances are you won't get them off!

I actually have lightly lapped some in before on a couple of my cars but never had a problem getting them off again. I lapped them In just a tad to remove any burrs so I guess I didn't really lap them in to a fine fit. I don't recall, but I may have also smeared a light coat of never seize on the axle taper as well. I guess that is a no no too.

Russ T Fender wrote: ↑

Fri Aug 26, 2022 5:50 pm

I actually have lightly lapped some in before on a couple of my cars but never had a problem getting them off again. I lapped them In just a tad to remove any burrs so I guess I didn't really lap them in to a fine fit. I don't recall, but I may have also smeared a light coat of never seize on the axle taper as well. I guess that is a no no too.

If you keep the compound wet, (well oiled) it wont lock during the process.
Clean off all the lapping compound completely before assembly.

Yes Val, lubrication of a joint which relies on friction to be effective is a no no, but it would make breaking the joint easier when required!

Allan from down under.

I think a lot of the taper issues might be build up in the taper and "choking" caused by the nut giving a false reading of wollered out hubs. I recently went through 16 rear wire hubs with a coarse round file. It is important to only "glide" the file flat on the angle and not lift either end as you do it. "Feel" the small lumps and work the file probably a few hundred strokes carefully as you go around and to only ride it on the surface to remove what is "up". I found a restriction at the small end in most of them that was caused by the nut, and when I was done, the hubs went on further and were tight without rocking. I used a new axle shaft in my vise to fit them. I measured the amount of axle sticking out with each hub for comparison. When I had one that did not go on to the average, it also had a small "rock". I continued cleaning and it went on to the mark. As a result, I am thinking we have been misreading what the fit is.