Q: What is your opinion on run-flat tires? Do you think they have the same longevity, and, more importantly, are they as tough as regular tires? I recently had my 2016 BMW X5 towed, because my Pirelli tire developed a broken “cord” and I didn’t feel comfortable driving 35 miles to the dealership on the interstate. These tires were original and had 46,000 miles on them. They were faithfully rotated every 5,000 miles since purchased new. In all my years of driving I have never experienced this. I have run GMC Yukon’s in the past. I’d be interested in your thoughts. — Lisa C
A: This is a thorny issue! I am not a fan of driving a car not equipped with a spare tire, especially after encountering an unfortunate tire injury in a remote location about a year back. In this case a run-flat tire would have been a blessing! According to the tire industry folks I surveyed, it sounds like current run-flat tires offer similar durability compared to conventional tires, earlier ones perhaps less. A 2013 J.D. Power study found consumers were replacing their run-flats about 6,000 miles sooner than those with conventional tires, while a 2018 survey found run-flat owners were somewhat more satisfied with their tires than conventional tire owners. Run-flats can be identified by a snail-like symbol (flat tire with arrow) on the sidewall.
The main drawbacks are a stiffer ride (often mitigated by the vehicle manufacturer’s suspension tuning), higher replacement cost, and driving on a deflated run-flat in most cases requires subsequent tire replacement, as structural damage is impossible to accurately assess. Additionally, convenient/quick availability of a matching replacement can be sketchy as only about 12 percent of the vehicle fleet uses them.
BMW is a strong proponent of run-flats, believing the safety considerations regarding a hazardous roadside stop and convenience to keep on going make them a desirable choice. I agree that run-flats make sense for folks who travel busy roads, roads with limited pullouts, or remote areas (keeping in mind the maximum range one can drive on one). If a vehicle still has room to properly stow a spare tire and uses conventional tires, that would be my personal choice. I researched and found a compatible space saver spare and compact jack to add to my Volt. They’re well secured, but some rear compartment space is lost. It’s great to no longer worry about being stranded again in my remote driving environment.
Q: I just had a flat tire on my Silverado and was unable to remove the nuts without the help of a person who stopped that had a pipe to put on my tire tool. What is the correct amount of tightness for these? Should I bring a pipe along? — Robbie B
A: It sounds like you were a victim of an untrained impact gun-wielding service person! Typical wheel lug nut torque ranges from perhaps 70-100 pound-feet for a car to 100-140 for light trucks (here’s a great chart). Your Silverado requires 140 pound-feet. Assuming dry/clean wheel studs and nuts this would be roughly 100 pounds of force on the end of your truck’s lug wrench, requiring perhaps an umph with a foot/leg for some folks to break the nuts loose and leaning down quite firmly to secure (almost as tight as an average person can, with arms, with the tool given). Although it might seem helpful, studs and nuts should not be lubricated as the specs assume a dry/clean condition.