How your luxury car’s tires can unexpectedly (and expensively) fail

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Audi A8 front in shop Ian Merriman

My old pal Ian has made a very handsome living seeing what others don’t—whether it’s a way to make Honda’s assembly-line tech work better or a few million dollars’ worth of money wasted in outdated processes and procedures. So it’s no surprise that he saw the “Dieselgate” scandal as a way to score a first-rate luxury car at a bargain-basement price. Last year he added a compression-ignition Audi A8L to his already extensive (and obsessively-detailed) garage. 

The big Audi was everything Ian had expected. Smooth, quiet, and almost hilariously parsimonious at the pump. The front end felt a little out of balance, but he expected that from a four-year-old car with a history of life on the mean streets (and freeways) of Cleveland, Ohio. He had the wheels spin-balanced by his local garage, and judging by the readouts on the shop’s machine they’d needed it pretty badly. Problem solved.

Or was it? I’ll let Ian tell the story from here:

I resorted to taking surface streets to work to travel at lower speeds. The tires on my car are fairly new, with a 2017 date code, and a tread depth of 8/32nds. I thought I may have a broken belt in one of the tires, or maybe something odd happened to one of them, so I looked online for a replacement pair. Upon searching eBay, I got lucky and found a pair of identical model and tread-depth 265/40/20 tires to swap onto my car. They were Pirelli PZero tires, just like the OEM tires on my car, with one critical difference I wasn’t aware of until my next trip to the shop… no foam inserts.

After my used tires arrived, the next morning I took them to be installed. My steering wheel wasn’t shaking, so I expected the vibration was coming from the rear tires. Trip number two, I stopped at J. Nutter Designs, had the rear wheels removed and dismounted, and to my surprise I found that each tire had a series of seven square foam blocks glued to the inside of the tires. A week or so prior, I had been discussing the issue with a technician friend at a local Audi dealer, and he mentioned some models have foam inside of the tires for reduced road noise. He nailed it, and predicted exactly what the issue was. They swapped the rear tires for the ones I purchased on eBay, and I drove it home. The vibration was improved, though not 100-percent better.

I removed the foam from the recently removed rear tires once I got home. The following morning, I took the tires back to have them mounted onto the front wheels. When the front tires were dismounted, foam blocks literally fell out each of them. The passenger side had two blocks loose and moving around inside the wheel, and the driver’s side had six flopping around! The driver’s side had only one block still glued to the rubber of the tire. The difference was night and day for the ride quality; road noise was not noticeably different to me. I was thankful for the cheap fix and happy to not have to replace all four of the fairly new and expensive tires. 

In discussing this with the guys at the shop, they mentioned that they had a set of Tesla tires which they showed me. Tesla also uses a foam insert, though it’s one solid piece and not several smaller ones, as in my vehicle. Had that been the case with mine, I may have never had the issue, or at least not been so pronounced. The foam blocks didn’t seem like much, but they add quite a bit of weight to each tire. 

As you might expect, our friends at TireRack have covered this situation in detail, including showing you how to distinguish insulated and non-insulated variants of each tire. Why did Ian’s tires start shedding their blocks? My guess is that northern Ohio simply has a wider variety of potential temperatures than most of the places in which the insulated models were tested. It’s also a place where the use of winter tires isn’t as common as it could (or should) be. No doubt the tire testers from Continental, Michelin, and elsewhere assumed that people wouldn’t run the same wheels in zero-degree and 105-degree days, thus exposing those tires to a considerable amount of expansion and shrinkage over the course of their lifetime. 

No doubt the tech will improve, but in the meantime, check whether or not you’re running on insulated tires. That knowledge could save you a lot of time and hassle when things get shaky. It makes me wonder why the car’s previous owner didn’t address the issue. Was he trying to save a few bucks? Or was this another case of Ian seeing what someone else didn’t?

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