Rusty tires

[Vibeman]

I posted some questions in this forum a couple of days ago about checking the toe in on my 2020 Thor 29M with a 2019 Ford F-53 chassis. While I was crawling around the tires I noticed something strange. Both front tires had a ring of what appears to be rust stains close to the rim but the rear tires did not.
I assume it is rust forming on unpainted areas of the the steel rims being slung out during travel. (I did go through some rain) But why would it be only on the front tires? I believe front and rear rims are identical and interchangeable.
Does anyone have any ideas? I am the second owner of this coach but it has less than 5k miles and all tires are the same and appear to be original. I have attached photos of the front and rear tires.
-Ken

[Winemaker2]

My guess is that's that's not rust but rather the residue of the compounds that come out of a tire when run and heated up. Mfg put it there to act as a protective coating to block UV?
Again a guess but likely the rim gets hot from brake use and that area may be higher temp than rest of tire under some conditions.
I've seen similar brownish blush on larger areas of side wall.

[Chargerman]

That rust ring is burnishing from your simulator wheel covers moving slightly as the wheel rotated while going down the road. It’s from the metal “grippers” on the backside of the simulator.

[Vibeman]

Thank you for the responses.
I'm not sure about the heat theory, but possible I suppose. I check tire temp at almost every stop and tires have never been what I consider "hot".
I will remove the stainless steel wheel covers and look for rusty steel clips. The rears have wheel covers too but maybe due to rear wheels being reversed the clip design is different.
-Ken

[clifford j]

I would agree with Chargerman, movement between the wheel cover and steel wheel. Front wheels (rim's) flex more than rear wheels. A common problem with snap on covers on sedans was squeaking wheel covers from wheel flex. When covers were pulled there was always rust powder around where the gripping fingers were.

CLIFFORD

[vettenuts]

That wheel looks to have a simulator on it, and the wheel itself is steel. The steel wheel rusts around the perimeter and causes the stains you are seeing. My coach has the exact same thing, and every couple of years I will remove the simulators and clean up the rust after which I paint the wheel to reduce the staining.

[George Schweikle]

X2, the rust is from the wheel covers rubbing on the steel rim. My MH has the same condition.

Originally Posted by vettenuts

That wheel looks to have a simulator on it, and the wheel itself is steel. The steel wheel rusts around the perimeter and causes the stains you are seeing. My coach has the exact same thing, and every couple of years I will remove the simulators and clean up the rust after which I paint the wheel to reduce the staining.

[TeJay]

I'm not sure about this either and this is just my theory based experiences and thoughts.

My first thought is if the covers are stainless how would they be involved in rust? the simulator wheel covers have no gripping tabs on the inside. They are held in place using the two special covered bolts.

Standard hub caps that had to be hammered on with a rubber hammer do have these special tabs or grippers so keep the hub cap in place. The simulated covers are very smooth on the inside. There is cover movement against the rim but it's only metal against metal and not against grippers, clips or whatever we want to call them. Why is this not as noticeable on the rears??

I believe posters #5 & 6, when combined, are closer to correct.

"Front wheels (rim's) flex more than rear wheels."

"The steel wheel rusts around the perimeter and causes the stains you are seeing."

The rears are not as greatly effected because they are not steer tires and the side walls do not flex nearly as much as the fronts. The front steer tires have greater side wall flexing and deflection. They move around against the steel rims and tire bead. The rims get wet driving in the rain. The rust forms while setting and as the tires flex the rust exits the bead area. The spinning tires forces the dry rust away from the bead and it sicks to the tire sidewalls. Some of the rust may be forced behind the covers and sticks to the inside of the wheel covers. In addition some of the dirt on the inside cover is from disc pad and rotor wear.

In February we had new tires installed. I watched the entire process and noticed the rust on the inside bead area on the rims. Also the lubricant used very liberally while installing the tires posted on the label of the 5 gallon can. "Special lube designed to reduce the rust which forms on the rims and tires. " The techs didn't know if it actually helped with the rust.

[Chargerman]

Although it looks like rust the fact is it is not rust as rust forms from corrosion. As I mentioned it is in fact “burnishing” which is formed when two steel surfaces rub together until one yields. Is happening only on the front due to the additional stress these wheels are incurring due to the load and steering which is deflecting the wheel slightly and therefor minimally shifting and flexing the simulator. It is not preventable without removing the simulators.

[StephenW]

My front tires and rims do the same thing. I half-decided the rust was caused by dripping water from the front gutter spouts splashing onto the tire and rim, then slung outward when traveling. I do keep the tires covered when parked at home, but not in RV parks. Lots of rain and A/C runoff here in Florida.

I like the idea that the simulators may be moving around, creating rust dust. Something new to investigate!

[TeJay]

If in fact it's not rim rust then I think it should be called brake pad dust. Yes it is the result of the brake pads rubbing against the rotors and that process is called burnishing or breaking in of the pads and rotors. The dust will not stop as long as the brakes are working.

According to a well written (DOT) book on the pad and rotor break in period it takes about 200 moderate stops with cooling off periods to properly break in a new set of pads and rotor. It's only following that process that the pads will be at their best stopping capabilities.

During that period pad material is transferred from the pads to the rotor and vise-versa. That's also another valid justification for machining all rotors when pads are changed.

[rgvtexan]

I think Tejay, gets the Kewpie Doll. It took 11 posts, for the right answer.

My PU was a bear to keep clean. Disc on the front drums on the rear.

[George Schweikle]

Respectfully I have an alternate answer. While, as TeJay says, the wheel covers are stainless steel and don't rust, they do rub on the steel wheels, rub off the paint, and allow the bare steel to rust. I have cleaned the rims of rust and applied duct tape to the inside perimeter of the wheel cover, and the rust disappears until the flex and rub of the wheel cover wears through the duct tape and the abrasion of the wheel begins all over again .

Also, the brake pad dust on my MH is black while the iron oxide on the rims is more red.

Originally Posted by rgvtexan

I think Tejay, gets the Kewpie Doll. It took 11 posts, for the right answer.

My PU was a bear to keep clean. Disc on the front drums on the rear.

[Coarsegold]

But he also said it only appeared on the front tires. So it likely is due to the brake dust because the front brakes do approx 70% of the veh braking, thus rust only on the front. I am sure some is from the wheel covers but not all. My class c did this for many years just on the front also.