Uneven break pad wear

Those reported thicknesses seem awfully low for new pads 4,000 miles old. Also, the tech has only given one reading for each corner of the car, not the inboard and outboard pad measurements at each.

Since you clearly have the skills to inspect your brakes yourself, I would do that and see what you find.

 

“6/32” and “8/32” seems an odd way to be reporting brake pad thickness, which is specd by Toyota (and most everyone if I’m not mistaken) in millimeters. New pad thickness for both front and rear is roughly 10 mm (9.5 mm for rears IIRC), and “service limit” (bare minimum) is 1.0 mm.

If I’d made the effort to remove the pads for a check and they were even at 3~4 mm I’d probably replace.

As @ChapmanF says, 6/32, presumably inches, is oddly low for near-new pads, less than 5 mm. And yeah, check them yourself will clear things up.

 

I was too lazy to do an actual conversion between mm and inch/32, rather I just went "hmm, mm is inch/25.4, so inch/32 is smaller than a mm, so 10 mm oughtta be (more than 10)/32, so 6/32 or even 8/32 sounds mighty thin for 4,000 miles of use".

 

What is "state inspection", just a local garage authorized to inspections? It rankles a little to have someone, presumably paid well, spec pad thickness in such an off-hand, unorthodox and incomplete way. On the state goverment's payroll?

Too, have to ask: were you careful with the rear brake caliper piston orientation? Good to verify too, after a drive: raise the rear and see that the wheels spin semi-freely. There's something in my signature on the subject. (on a phone turn it landscape to see signature).

 

Who supplied you with that information? The numbers seem off.

Toyota specs their pad thicknesses in millimeters, not in /32.

When new, Gen 3 front pads are 10 mm (about 13/32 if somebody wanted to say it that way), and rear pads are 9.5 mm (about 12/32).

Front left being down to 8/32 from 13/32 isn't anywhere near "in line w/expectations" for 4k miles. Unless expectations are to use up the pad completely before 10k. Many people have them last ten or twenty times that.

Also, there should be eight measurements total: two for each corner of the car. At each wheel, there is an inboard and an outboard pad. They don't always wear equally.

 

Maybe time to switch to millimeters?

10/32 (presumably of an inch) is equiv to 7.9375 mm. New front pad thickness is 10 mm, and "service limit" is 1 mm.



New rear pad thickness is 9.5 mm, and same minimum thickness:



Again, anything less than 4 mm, if I had them in my hands, I'd be inclined to just replace.

 

True, but who can explain why tread depth on tires must still be expressed in 32nds of an inch? Or why standard tire size designations are a crazy jumble of metric and inch units?

 

Up here everything’s metric first, and often no imperial units, say in brackets. More often than not it’s a product (say a tub of margarine, aka “buttery spread” in the States) originally measured in imperial (ounces, cups, quarts), and the cubic centimetre conversion is some odd conversion, hopeless when you’re standing in a store, trying to cost-compare various sizes, without a spreadsheet.

the “best” units are invariably the ones things are originally designed in.

conversions add countless hours and frustration/complexity in my past profession, structural engineering.

 

Ok, but what numbers are embossed on the sides of tires there?

 

The same mix of inches, millimeters, pounds, kg, psi, and kPa we have?

 

The best way to check is to squeeze all of the caliper guide pins while the brakes are fully assembled and make sure you can squeeze them in and out a bit easily with just your hand. If you can't then it was done incorrectly. I do mine once a year as I have found they effect gas mileage.
If the caliper guide pins have lost their nickel finish and you have the original dry rotted boots i would go ahead and get new sliding pins and boot kits for all 4 corners. Then just get a drill brush and some brake clean, drill brush out all of the caliper brackets to make sure all of the old grease and corrosion has been removed. For reinsertion i use sil-glyde on the pins up to the bushing with a small amount on the bushing and nothing before that on the tip. So you can insert them without trapping air in the cavity.
Past that i also like to use a high temp ceramic grease on the pad clips that grab the ears of the pads and a bit on the piston of the caliper to reduce corrosion to the pad backing plate. Mine are so free i can hear the pads click in and out of the clip because the pad clip fully retracts them out after a while of sitting lol. When doing the thin layer of grease on the pads clips the difference is dry you have to push the pads in and they stay in the inner position. After greasing them up correctly you have to hold them in as the clip wants to throw them out until you get the caliper back on.
When i had the original pins and boots where the boots were broken and the pins had corroded and lost their finish, doing brake lube jobs every 3 years i noticed i was getting a lot of seizing and pads were wearing unevenly. After I swapped to new hardware and lube once a year my mpg went up around 15% back to normal.

Also, for good measure when doing the rears i like to bend the pad retraction springs out a bit to give me a bit more springyness back there for good measure.

 

The jumble of metric and standard was more or less caused by us in the usa swapping to cheap asian manufacturing and thats what they used. So we adopted a lot of their metric standards to make things easy. Now say a new Ford is pretty much all metric as thats what they used to design the car now. But the older ones were a mix of 1/4", 3/8", 10mm, 1/2", 15mm, 16mm, 17mm, and 13/16" lol
It really makes simple jobs on say an old Ford Ranger tough when say a Sequoia pretty much just uses 8mm, 10mm,12mm,15mm, 17mm, 21mm
The tire size thing is confusing until you realize most tire shops still tell people to repace at 2/32."
I can't quite remember the old standard tire width sizing but it was more confusing than the metric way

 

I had a Bronco II, basically a Ranger with no rain in the back, with its Canadian body, German engine, Japanese transmission, and US Borg-Warner transfer case.

Pretty much all the bolts and nuts on it were metric, except for the bolts holding the transfer case to the transmission.

 

I guess if they were marked ACME 20,000 MILE ECONOMY PADS or something, that would be considered right on track.