Toyota’s BZ4X Wheels Solution That Can Remove Themselves Is Way More Involved Than You’d Expect
After reports of some of the new electric vehicle (EV) crossover’s wheels coming loose in Japan, Toyota issued a recall notice for its bZ4X back in June. Subsequently, Subaru Solterras were also included in the recall. Because a patch was not yet in the works, Toyota issued a stop-sale order for all bZ4Xs in the United States until a solution could be found to the problem. Now, Toyota has made an announcement regarding its remedy, and it is very involved. Please be patient as we explain the specifics of what led to the problem and how it can be fixed for all global bZ4Xs in general and for models destined for the United States in particular.
The Reason Behind the Toyota’s BZ4X Wheels Coming Loose
According to Toyota, the primary reason for the Toyota’s BZ4X wheels coming off was a lack of clamping force between the wheel bolts (which Toyota refers to as hub bolts but are often widely referred to as “lug bolts”), the wheel hub, and the wheel. The clamping forces that are necessary between the seats of the fastener and the wheel are provided by the threads, which are located on the lug nuts and lug bolts that are found on your vehicle. In order to achieve the desired level of clamping force between the seats of the fasteners and the wheel face, those seats must permit the bolts or nuts to rotate.
This ensures that the threads engage correctly and that the torque may be adjusted to meet the necessary specifications. It turned out that this was the primary concern at hand: the Toyota’s BZ4X wheels’ bolts and wheel seats had an excessive amount of friction, which prevented a suitable clamping force from being achieved.
It’s possible that you’re wondering why, if the lugs are properly tightened, the clamping force wouldn’t be adequate. It turned out that there was just enough room left over to allow the wheel to rotate freely. Over time, the Toyotas allowed enough movement to allow the bolts to loosen (this is why it is necessary to periodically check the torque of your lug nuts or wheel bolts).
This movement was almost imperceptible to the human eye, if it was even detectable at all. It was discovered that the heat cycling of the wheel bolts, wheel, and hub during certain common driving scenarios, such as hard braking, was sufficient to expand and contract those components in such a way as to reduce the friction of the bolt seats and allow the bolts to loosen even more quickly.
This was discovered after it was discovered that the heat cycling of the wheel bolts, wheel, and hub occurred during certain common driving scenarios, such as hard braking. U.S.-spec bZ4Xs wore different wheels that not only had a rougher seating surface than Toyota’s BZ4X wheels (which increased the surface friction even more), but also had inaccurate bolt patterns, which misaligned the wheels to the hub enough to make the clamping force issue even worse. As if those two problems weren’t enough, the misalignment of the Toyota’s BZ4X Wheels to the hub further exacerbated the clamping force issue.
Already, You Need to Put a Stop to That!
Is There Already a Fix to the Toyota’s BZ4X Wheels ?
Toyota has found a solution to the problem now that it is aware of everything. To begin with, the bZ4X has been updated with a new wheel bolt. It is not just a new seat design; it continues to employ a conical seat (which is distinct from the conventional ball seat that is used in the majority of European automobiles), but it is no longer directly coupled to the wheel bolt.
This innovation goes beyond a simple seat redesign. Instead, it is simply a washer with a conical form that faces the wheel, while the wheel bolt itself is ground flat where it meets the flat side of this washer. This washer is what you see when you look at the wheel from the front. No, that is not a Belleville washer; rather, it is a spring that has been bent into the shape of a washer. I’m glad you asked, but the answer is no.
The new design that Toyota has used is comparable to lug nuts available on the aftermarket that have a “floating” seat. The primary distinction lies in the objectives pursued by each: in the aftermarket, the floating seat serves to shield the rims from damage, preserving their aesthetic appeal and preventing scratches on the seat’s surface.
The objective here for Toyota is to lessen the friction that exists between the wheel bolt and the wheel seat in order to provide room for appropriate clamping pressures. Toyota additionally reworked the alloy of the bolts in order to sustain such clamping pressures even over heat cycles. This was done in order to boost the coefficient of friction during such cycling, which in turn resisted any movement of the bolts as they went through expansion and contraction.
These adjustments are only being made for the global bZ4Xs. In addition to these, the U.S. version receives new wheels that are designed to conform to the standards of the hub, ensuring that the lug hole pattern is accurate throughout the vehicle. Even though the new wheel design is different, the seats of the wheels have been improved so that they have a lower coefficient of friction. This helps to ensure that the bZ4X’s wheels have the appropriate clamping forces applied to them, despite the fact that the Toyota’s BZ4X wheels’ design is different.
It Was the Worst Case Scenario Possible for Toyota’s First Electric Vehicle (EV).
The fact that the wheels were coming off during the recall is hardly the most troubling aspect of the situation. Since they hadn’t been manufactured in sufficient numbers to be on the road outside of Toyota’s dealer models and the ones we in the media drove, there wasn’t going to be anyone driving a Toyota bZ4X anyway. No one had seen one in the wild. Toyota recognized the issue, withdrew the vehicles from circulation, and began developing a solution to the problem.
Despite this, it was an extremely damaging blow to Toyota’s public relations, which could not have been any worse. Even while the brand’s millions of hybrid vehicles have made major contributions to improved fuel efficiency over the years, the company has come under fire for its tardy entry into the market for electric vehicles. The sheer bad luck of finally having an electric vehicle (EV) to sell and then having its wheels fall off before it has even started moving is beyond comprehension.
You can bet that Toyota is hoping it can get through this hiccup, as the company is committed to introducing 70 electrified models by the year 2025, including seven full BEVs under the bZ brand and 30 BEV models overall, which will help it achieve its goal of selling 3.5 million electric vehicles annually by the year 2035.