In addition, the compensation package for bZ4X owners who wish to keep their vehicles has grown to be quite vast. We’re talking about a free loaner vehicle, reimbursement for fuel for said loaner vehicle, a $5,000 credit on the vehicle, complimentary charging at EVgo stations through 2024, and a warranty extension.
— David Conner (@OutofSpecDave) August 1, 2022 More details on compensation can be found in the above letter, confirmed by Engadget to be legitimate. As for American owners of the bZ4X’s Subaru Solterra twin, they might not really exist yet. The initial NHTSA recall report states that “Subaru has informed Toyota that no Solterra vehicles have been sold to dealers or retail purchasers.” So how did we get to the point where Toyota needed to send a buyback offer to bZ4X owners? Well, it’s a little bit complicated. First, let’s define the issue Toyota’s having with the bZ4X. While “hub bolts” is the terminology most associated with this issue, it’s worth clarifying that the recall has to do with wheel bolts like you’d find on many European cars. Should these bolts back off, the wheel would detach from the hub, rather than the hub detaching from the knuckle. Subaru issued a lovely diagram detailing the issue, which I’ve inserted above. It’s very strange language in an age of bolt-on hub assemblies, but that’s the way it goes sometimes. So how did Toyota find out about this issue? Let’s take a look at the defect information report uploaded to the NHTSA website. Wow, that’s not good. Toyota recalled the bZ4X in late June, which means that we’re more than a month in without any updates on a potential fix. At the time, owners were advised to avoid driving their new electric vehicles, so all affected models should still be grounded for now. It’s more than a little bit weird that Toyota didn’t discover this issue during development. From climate testing to final calibration, development engineers often puts tons of miles on prototypes. Given how early we are into the production run of the bZ4X and its Subaru Solterra twin and how these failures have occurred on low-mileage examples, shouldn’t self-loosening wheel bolts have been caught and corrected? Toyota received a field technical report from the Taiwan market indicating separation of the front left wheel from the vehicle. Toyota recovered the wheels and hub bolts from this vehicle for investigation. Toyota then received two field technical reports from the U.S. market. One of the reports indicated loose hub bolts of the front left wheel and the other indicated a separation of the front left wheel from the vehicle. Toyota reviewed the production process at the vehicle assembly plant and did not identify any abnormalities on the hub bolt tightening history of these three vehicles. Toyota also reviewed the assembly process of the wheel and hub bolts at the assembly plant and did not identify any abnormalities. In addition, although damage was observed on the wheel recovered from the vehicle in the Taiwan market, the damage was believed to be a result of the wheel separating from the vehicle and the cause of the loosening of the hub bolts was not able to be identified. Toyota continued to investigate and conducted a driving test using mass production wheels and hub bolts that were tightened to specification. The testing showed that the hub bolts loosened under certain severe driving patterns.
Weirder still, this isn’t Toyota’s first attempt at using wheel bolts instead of studs and nuts. For instance, current Lexus IS models in non-V8 trim and the Lexus NX 350h use wheel bolts with a part number of 90942-02090. Plus, other automakers have used wheel bolts on EVs without issue. The BMW i3 and Volkswagen ID.4 immediately come to mind. There’s no real reason why the use of wheel bolts might create more issues than a stud and nut arrangement, so the nature of the defect is quite puzzling. As it sits, Toyota doesn’t have a fix for the bZ4X despite the initial defect report having been issued more than a month ago. So what gives? Well, a fix could require new hardware and additional testing, which may push back the timeline for a solution. Plus, if any component changes are required, today’s tight supply chain might affect Toyota’s ability to procure new components. In any case, this recall is a bit of a disaster for Toyota. While the Japanese brand has dabbled in compliance EVs like the Scion iQ EV and both generations of the RAV4 EV, Toyota’s generally dragged its feet on producing a mainstream battery electric vehicle. With an incoming EV offensive, the bZ4X was supposed to be the flag-bearer, but its failure to launch has tainted Toyota’s reputation in EV circles. While a bad reputation in EV circles may not seem like a huge deal to some, it’s worth noting that EVs are often enthusiast vehicles. They may not pack the tire-shredding boisterousness of muscle cars or the poise of mid-engined sports cars, but EV owners are passionate, informed, and often the first point of peer-to-peer EV advice for many potential buyers. This bZ4X wheel bolt recall is on par with Ford Focus RS head gasket issues and likely won’t be good for Toyota in the long-run. We’ll continue to watch the bZ4X recall closely. Hopefully owners who wish to keep their Toyota EVs can find some form of resolution soon. Lead photo credit: Toyota https://www.youtube.com/watch?v=Ii8rC6CPCvM How is it different then the stud and nut that has been used forever in the US? And, why is it different? Airstream recently had a recall due to axle washers in axles provided by Dexter. The washers would break and the wheel would come off. They caught it quick and it only affected 250 trailers (many of which hadn’t been delivered yet), but a few people did lose wheels prior to the recall. Sometimes it’s the simplest thing that has been used for years, but something minor changes, or you get a bad run of parts and it becomes dangerous. A wheel coming off a vehicle is a pretty dangerous situation. Here’s a BMW with a similar setup to what’s being discussed here: https://f87.bimmerpost.com/forums/showthread.php?t=1683573 As for why they did it, there are a lot of possible reasons. Hanging a wheel on a stud and pushing it on is a good way to damage the threads or the wheel. It may give a mechanical advantage to fastening. It is theoretically easier to install different wheel sets onto the same suspension package. Several companies that used to use lug bolts in the past have gone back to lug studs. It just depends on what’s going on internally I can’t comment on any benefits, but as far as negatives, you will either need three hands to put on a wheel so you can hold it with 2 and start a bolt with the third, or you can buy a metal rod that threads into the lug bolt hole to hold the wheel. I use 2 to improve centering. You also can’t reasonably access the back of the hub, so any corrosion or other crud on the tips of the bolts is getting dragged through the threads. I expected more intelligence from Toyota. If you use wheel bolts you do actually have to thread the holes in the hub so it is probably more expensive. As for Toyota, they have form on this with 70 Series Land Cruisers. Especially in their transition to the V8 turbo diesels. Turns out the wheel nuts were too thin and, if the vehicles were operated close to GVM in rough environments (like mine sites or long distance touring), they could come loose. They then offered thicker mine spec wheel nuts with plastic indicators… problem went away. Took many nuts… [Interviewer:] This car that was involved in the incident on the highway this week… [Toyota Spokesperson:] Yeah, the one the wheels fell off? [Interviewer:] Yeah [Toyota Spokesperson:] That’s not very typical, I’d like to make that point. [Interviewer:] Well, how is it untypical? [Toyota Spokesperson:] Well, there are a lot of these cars going around the world all the time, and very seldom does anything like this happen … I just don’t want people thinking that our cars aren’t safe. [Interviewer:] Was this car safe? [Toyota Spokesperson:] Well I was thinking more about the other ones… [Interviewer:] The ones that are safe,,, [Toyota Spokesperson:] Yeah… the ones the wheels doesn’t fall off. So the answer was simple – when you rotate tires you usually just move them front to back and vice versa, I had gotten too smart for my britches and cross rotated the front tires. So fronts went straight back, and the rears crossed as I moved them to the front. Now normally this would not be a problem but in this case I had not noticed that the tires I was running were directional. I crossed the fronts back over and all’s good – lesson learned! I’m guessing that the directional tread set up some sort of sympathetic vibration that caused the bolts to loosen when they were turning the wrong way? We used some heavy duty zinc-plated 12.9 class bolts. We torqued them to spec, left the assembly on a crane overnight and when we came back the next morning half of them were loose. Imagine the face of the dude who saw 8 tons of steel hanged on a crane with half its parts coming off! The torquing procedure was fine, but it turned out the plating induced hydrogen embrittlement in the bolt, causing them to relax when a sufficient load was applied a certain amount of time. Now we recheck every bolt 24h after it’s been torqued. I wasn’t employed there back when this happened, but I believe there has to be a link between the plating and the bolt class as you won’t find a French bolt manufacturer who’ll sell you plated 12.9 bolts while 10.9 and lower are available plated. I can’t tell you how the bolts looked like after this event, I’ve only read about torque issue, not damage but again: it’s not first hand knowledge. Subaru is known for shitty wheel studs Another possibility is that the specific driving condition isn’t an expected behavior of the car, and they’re trying to determine a way to eliminate the behavior, which also takes time. And finally, lawyers are involved.
- edited for family content And Loctite shouldn’t be used on bolts M10 and up. Maybe that’s just something we do internally and not an industry standard. I don’t know precisely of the K factor you talk about, but I presume it relates to the friction losses when torquing the fastener that do not translate to clamping force. I wanted to try and model analytically how torque translates to clamping force accounting for these parameters and bolt geometry but it was more time consuming than anticipated and my work load got in the way. If you’ve got some reference material related I’d be interested Your Mileage May Vary—wildly
