Black Spots on Rims

I got a 23 TRD OR this spring and have been loving it. I've already done a good number of trails around Colorado this summer. I only recently got an air compressor so I can air down, and I noticed some weird spots on my rims right where the tire meets the rim, after doing my first trail where I aired down (to 18-20ish psi). I didn't notice until after I got home. All four rims have it and all four look similar, where the spots are very regularly spaced. Does anyone know what these are?

 

Does it wipe off?

 

Appears to be corrosion under the clearcoat. Looks like better maintenance needed.

 

Not a lot of detail offered here...as @McSpazatron mentioned, does it wipe off? Have you done anything to try and remove it?

 

Maintainance or not, I’d really hope it’s not corrosion on wheels that are probably less than a year old. It just looks like a dirty wheel based on that picture.

My advice is to work through a clear diagnostic process. I’ll work on developing a flow chart and attach it to this thread in the future. But in the meantime, I’ll outline the basic steps.

1. Wet finger with suitable water-based liquid, such as saliva (water may be used for this step, but not required).
2. Place wetted finger over stained area, push your finger onto the stain with a force equivalent to 5-10psi, and move it over the wheel surface using a linear, reciprocating motion.
3. Observe surface of wheel, taking note of any differences in appearance.
-If appearance is unchanged, re-wet finger (do not place fingers in mouth) and repeat the remaining portions of step 2. If appearance remains unchanged, present results to forum for further technical analysis.

- if the stain disappears or changes in any manner after wetted finger procedure is completed, use any commercially available brush/sponge/rag and water based soap solution scrub entire wheel. This will replicate the effects of step two in a more efficient manner on the entire wheel. Advise forum of results to ensure any useful soap solution recommendations are communicated.







I love how these mystery posts suck me in lol.

 

Thanks, i have copied this and will put this very detailed info in my Runner, and also my wife’s car.

 

As a professionally amateur technical writer, engineer, and astrophysicist, I’m pretty sure you can apply this flow chart to other things. Even non-car related things!

 

Nice! A write-up on how to wipe off a (potential) smudge! You know you're going to be asked to follow up with write-ups on cleaning every other part of a 4R now.

Back to the OP - it is odd how these dark spots are pretty much equidistant from each other all around the wheel...also, the OP seems to have done a number on the sidewall of the pictured tire - seems to be a few curbs rubbed.

 

I appreciate the detailed instructions . The spots come off quite easily with a wet wipe. It is definitely not any type of corrosion. How to clean them isn't my concern; I want to make sure I'm not damaging the wheels somehow. Since the spacing is so regular and it happened on all four wheels, I figured it was likely an issue someone had seen before. But my internet searching was fruitless, so maybe not

The sidewalls haven't met any curbs but they have been introduced to a number of rocks, despite my best efforts to prevent those meetings. A tire upgrade is coming in the near future with some added sidewall beef

 

If called upon, this is a task for which I am most certainly prepared. Considering the smallest details at length, depth, and breadth (important or not) is kinda my thing.

Keen observation. I see a pattern too. But the human mind is made to spot patterns, and sometimes that can lead to seeing patterns that aren’t actually real. The picture doesn’t have enough resolution to be sure of the nature of the dark spots. Are they dirty spots from using a car wash that always misses the same spots? Did the OP damage the wheels on something that imprinted the damage in a repeating pattern? The OP is the only one that can tell us, but only after following a careful diagnostic process

I also wondered if the scrub marks might be related to the pattern, but it doesn’t seem to match the dark spots. Hard to tell, not sure.

One thing is for sure… The OP has been hitting the trails in Colorado all summer …on stock factory tires!!! Those scrub patterns show he was not messing around! serious. This can only mean his bravery and skill picking lines automatically qualifies as him as having Legendary status.

I recently went to Colorado and a young kid with a 4runner on K02 Load C tires pulled up to a neighboring campsite with a flat tire. By morning, another tire was flat from a slow leak. Those trails have tons of embedded and loose rock that is sharp and can be brutal on tires!

And just so the OP knows… sometimes we like to joke around on this forum (at least I do). Welcome, and congrats on getting that 4runner dirty !

 

Ah, you hit send before I did lol. The mystery is solved! At least the part about what those dark spots are.

What would you guess those spots were made up of? Regular road grime, or trail dust, or dark silt?
There’s a possibility it’s the imprinted magnetic field lines caused by an MRI machine, but only if the stains are caused by silt with high iron content, and you park right next to one of those mobile MRI tractor-trailers. I’ll admit, probably a small chance of that.

Otherwise, I’d take a guess that maybe the tires had some sticky residue on them from something like those protective plastic sheets they put on wheels when they ship new cars. If they had tacky adhesive in a pattern that stuck to the wheel, it could have made dirt stick more to those areas.

That, or my car wash idea. Just spitballing though.

 

I saw lots of people on these here forums saying how the stock tires are trash. Luckily my anecdotal evidence says otherwise

Hard to say. It is certainly not dirt. Comes off looking almost like graphite. Here are some additional pictures. The car wash idea is interesting, but I've only gone through a car wash once and that was at least a few months ago (never fear, I am hand washing it).

 

No stock tires are trash, but that doesn’t mean they aren’t worth some miles on. I took my stocks up to a place I go all the time when I got my runner, and as I knew would happen the shale punctured a tire.

 

Yeah I am (mostly) joking that they are good. I am definitely impressed by what they have gone through after reading about them, and the gas milage is nice. But I'll be glad to not be constantly worried about getting a flat on trails once I upgrade

 

Try some Goo Be Gone in an attempt to remove any left over adhesive from the factory plastic covers used during shipping, If any remains.

Welcome to the forum.

 

I put mine back on when I got a bunch of highway miles, sucks to keep changing, but I’m slowly wearing them down.

 

Or maybe get a pet gorilla and use their snot....

 

Thanks for the ideas. I'll try cleaning them well and seeing it pops up again. I'll update if it does

 

Pfft. Rocks are nature's curbs!

Thanks for solving the spot mystery.

 

What is on the tire causing the discoloration if it is not from rubbing a curb or similar suggested?

It seems to me maybe you drove through some water that had a chemical or unusual substance that ran down the tire only to the edge of the wheel. The inner alloy portion looks fine it’s just the edge with the issue.

 

OP stated "The sidewalls haven't met any curbs but they have been introduced to a number of rocks, despite my best efforts to prevent those meetings."