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I was helping my parents clean out the basement and came across my sisters Ultima. I originally just thought it needed wheels/tires, but it looks like it was used as somebody's "parts car" while I was off in college. During the last few weeks of tearing it down, cleaning it, and building it back up I have come across a few things. I almost have it back together (waiting on some spring collars for the "red" shocks) might post some pictures when I do.

How loose should the rear axle bearing be in the hub? The reason I ask is that I have replaced the bushings (with bearings) and even tried an NOS hub from eBay and the axle hub assembly still seems like it has tool much slop in it. Has anyone tried an modern rear hub (UM519) in the stock swing arm?

Any comments / help is appreciated.

Having had a lot of various cars, cheap to expensive, I can say that the machining between the bearings and axle shafts can be rather sloppy at times. I've even had a cheap basher with tighter tolerances than a Associated B4.2. Soo, I guess what I'm getting at, is to just not worry about it.

The bearings fit snugly in the hubs of all my Optimas (with unmodded rear ends), which use the same rear hubs as the Ultima. I haven't had a slop or too much play issue with any. You might have to break out the calipers and do some measurements, something doesn't seem right there. Did you buy new bearings or are you using some you had lying around? Standard bearing sizes are sometimes very close to Metric, but not exact...is it possible you have Standard-sized bearings that are a smidge undersized? Just a thought...

I did buy some new bearings and they measure right at 10mm. My origional hubs (and my NOS) measure 1-3 thou larger than the bearing, which is why there is slop.

I am wondering if the origional set is work out, and my NOS set was made from a worn out mold. I may buy a new (RB6) set of hubs and see if the bearings fit tighter in those. I am trying not to overthink this but the bearings are tighter in my T.Optima and Icarus and they are 30 years old.

opelgt21 wrote:I did buy some new bearings and they measure right at 10mm. My origional hubs (and my NOS) measure 1-3 thou larger than the bearing, which is why there is slop.

I suppose, since you were running bushings previously, and bushings wear much faster than bearings, this could have caused your hubs to wear prematurely...the bushings might've fit snugly, but as the holes for the axles wore out a bit wider and wider, the resulting axle play could've opened up the bushing holes in the hubs. Bearings wouldn't have worn out like this and the axles would've always stayed tight inside the bearings, and this would help to preserve the hubs. Just a thought.

Rb6 is most likely a total different offset and therefore won't work with your standatd axles or give you a too narrow rear end.
Mark, the rear hubs of the optima and ultima are not the same.

Right you are, my bad. I must've been confusing Optima Mid with Ultima.