Long-term tire wear, and a weird confluence of happenstance

[hobbit]

So I haven't kept up with things here very well recently, as ownership has
been pretty stable and uneventful over the last 40,000 miles or so [as it
should be!]. But over the last few months I had started to notice a kind of
"wub-wub-wub-wub-wub" sound in the cabin, seeming to come from the rear of
the car. My first thought was "huh, am I losing a wheel bearing?" ... but
it seemed to come and go depending on what kind of pavement surface I was on,
and I had been noting its existence for *over 10,000 miles*. A bearing
would have gone critical long before then. So I figured it must have something
to do with the fact that I hadn't rotated the tires on this car for at least
35,000 miles, if I in fact ever did, and cannot remember if these tires got
any attention or were just in the same positions as when I'd bought the car
in 2021.

Anyway, today I finally set to and did the all-around rotate + brake caliper
cleaning/refresh routine, to make sure the slide-pins were in good condition
and the pads would slide reasonably freely. As I pulled the rear wheels off
to cross-move them to the front, I took a hard look at their tread blocks, and
finally understood what was likely going on. It took this many miles to get
to the point of being really noticeable, since I run all four around 60 PSI
anyways and that, plus my general driving technique, always makes any typical
wear take a lot longer for me to manifest.
View attachment 24120
[ higher-res link: http://techno-fandom.org/~hobbit/cars/ev/76rearwear.jpg ]

The Kona comes by default with quite a bit of negative camber in the rears.
Just viewing the car from a ways behind it makes that fairly obvious. For
what reason, I cannot imagine; it's not like anyone is taking Konas out
to Track Day, so why does it get factory-set as if it would be subject to
frequent hard cornering? The inner sides of both long-time rear tires were
clearly feathered a bit, and that's likely what was causing the noise into
the cabin. Those are on the fronts as drives now, which have essentially no
camber either way, so that should slowly work to fix them. Meanwhile, a
short test run already returns that the newly-placed rears run quieter.

This *will* be load-dependent, as the camber adjusting bolts inboard of the
rear suspension members are at different offsets from the car's centerline.
If only one of each rear wheel's pair is adjusted, that will also affect toe,
so to *only* adjust camber, both bolt spacers per side would have to be
moved the same distance. Since it's taken this long with no rotation for me
to notice any effects at all, I'm not going to eff with it. I'm to the point
that I should probably get all new feet for this beast anyways, but the three
crappy factory Nexens + one oddball-replacement still have enough handily
legit tread depth so I can probably hold off longer. Yes, after 40k+ miles.
I don't thrash them...

The second weird event came as I was wrapping up this work; I went to fire
up the car and take a quick test drive to settle wheel weighting and listen
for any differences, but found that the car was *completely* dead when I
slid into the driver's seat. Not even the logo showing the door open. The
12V battery had somehow gotten down to like 5 volts, and wouldn't power up
any part of the car. I immediately recalled all the "dead 12V" InsideEVs
postings and the careful research folks had done. Okay, so a OEM "Rocket"
unit dropped into a 2021 MY car had evidently flown its trajectory and was
already dead in mid 2025, which I frankly don't think is reasonable but we
all know the factory-issue batteries are garbage. So now I guess it's time
to go find a decent replacement.

_H*

 

[michael8554]

Many EV owners run their tyres at higher-than-spec settings, but 60psi, probably 66psi when warm, is way higher than the recommended 36psi.
However that over-inflation would lead to uneven wear in the middle of the tread, not the edges.
I would think the rear negative camber is to reduce oversteer if you accidently hit a sharp curve too fast.
And explains why the tyres need rotating so often.

 

[hobbit]

Heh, well, in my case it certainly wasn't "so often", and now we can see the result.

I'm considering an aftermarket set of rims for when I do go for new feet, that aren't
so heavy and ugly. When I had to replace a tire in the middle of a roadtrip a couple
of years ago, I was astounded that the damaged Nexen weighed almost nothing and
the bulk of the wheel's weight was the rim alone.

_H*

 

[JoeS]

However that over-inflation would lead to uneven wear in the middle of the tread, not the edges.

That was true for non-radial tires. I ran my Gen1 Honda Insights at 60psi for ~150K miles with very uniform tire wear.

With the Kona I'm no longer obsessed with efficiency and wife prefers a softer ride so I keep them ~40psi.

 

[hobbit]

Having done more driving around today, notably to hit my usual Batteries Plus for a 12V
they said they had in stock, I now think I hear the "wooba-wooba" effect more from the
front, and even feel it through the wheel at certain speed ranges. And more prominently
during regen braking, which is probably the most stress on those tires as they're now on
the front. They may never "equalize" back out by the time they're simply done, but at
least I know what was going on.

I did run a bad bearing in the Prius for someting over 1000 miles before I could get it
replaced, and I remember that sounding quite different as wear progressed.

Anyway, good riddance to the ol' Rocket. Bought the new one [some derivative brand from
Duracell, they said], swapped it in the store parking lot, went back in with the old one to
drop on their recycling cart. Interestingly, the rail now runs at 13.3V instead of the old 14.7,
but it's not like the new battery is sucking tons of current [measured by OBD2 queries]. So
I guess the LDC just figures out what it's got connected and handles it.

I also finally learned that the "calcium" plate chemistry is intended to reduce gassing, and
doesn't really have anything to do with capacity or whatever. The guys at that B+ store are
pretty well-informed and enjoy geeking about this stuff.

_H*

 

[KiwiME]

... Interestingly, the rail now runs at 13.3V instead of the old 14.7 ...

There won't be any such major change in the charging regime. After noting the loss of 12V system power when the battery was swapped the BMS does a little test that I assume characterises the resiliency of the battery in terms of volts dropped by amps drawn and the (parked) charging schedule will be refined to suit over the following days.

In the case below after a BMS software update it queried the 12V several times then settled down into a routine the next day.

I've learned to leave the Kona in Utility mode when left at the dealer for service or annual inspection as it gives them a better chance of not depleting the 12V.

 

[hobbit]

Yeah, I guess it tries to be smarter than that, as a couple of days later it's back up to 14.7 or 14.8 volts.

I can also notice the tire vibration now from the front quite a bit more on a *wet* road.

_H*

 

[dcisive]

In some regard guess I'm glad my 2025 Kona Limited is on a 2 year lease. Shouldn't have to worry about any wear factor considering I will likely be putting on no more than 3600 miles a year. The last time I had a VW ID.4 and at 13000 mi the tires were shot. How pathetic.

 

[Ferenc Jakab]

Heh, well, in my case it certainly wasn't "so often", and now we can see the result.

I'm considering an aftermarket set of rims for when I do go for new feet, that aren't
so heavy and ugly. When I had to replace a tire in the middle of a roadtrip a couple
of years ago, I was astounded that the damaged Nexen weighed almost nothing and
the bulk of the wheel's weight was the rim alone.

_H*

I unknowingly wore one rear original Michi Primacy 4 down to cord. At my age and arthritic advancement, it is too difficult to get to a position where it is visible. 2022/23 models came with Michis in Oz. Personally I thought the Prius rim was heavy too.