Featured Toyota fixes bZ4X wheel fall-off by using washers under wheel nuts

Details are not clear, but excessive friction (against the bolt head or in threads) would certainly reduce the clamping force. Also unclear, how they messed up something so basic and why they didn't use conventional studs+nuts method of attaching the wheels, instead of mounting bolts going into threaded holes (at least as I understand).

 

Porsche wheel bolts have used conical washers to increase contact between the bolts and the wheels for years ... at lest back to 1997 in my personal experience.

 

I am guessing they used bmw's method of mounting as they are partners and I'm guessing it works well on the toyota supra that uses lots of bmw parts. This makes little sense for toyota on this car. I don't know how this did not come up in testing and get fixed before the vehicles reached customer's hands.

 

Nice to see this moving forward - for the customers sake and so Toyota can continue its path forward on its EV initiatives

 

To save money.

Take a hub, studs, wheel, and nuts, and compare it to hub, wheel, and bolts. You eliminate a part with the bolts. Even if the material costs are the same between the two methods, the bolts eliminate the step of installing of the studs in the hub. that saves money in time, and on the press needed for the job.

It seems not worth the effort on a low production model like the bZ4X, but it sounds like the new Crown is using wheel bolts. If so, we'll likely see all Toyota models shift to bolts in time.

 

European brands have been using wheel bolts for decades. They may have had a technical advantage 'back in the day'. Might have been mentioned in the other threads discussing this.

Replacing a bolt with damaged threads is a lot easier than with a stud. Bolts can make it easier to switch to a different sized wheel for the same reason.

So do the bolts. When you know what you are doing
VW and BMW have been using them for decades. They don't have the best rep for reliability in the US, but I don't recall wheels coming loose because of the bolts being a problem.

 

Apparently Porsche knew wheel bolts could need washers, and Toyota didn't.

Toyota made a decision to save manufacturing costs, and didn't do enough testing to ensure the change would work. This isn't the first time this has happened. In the early 2000's, Toyota engines were having oil sludging issues. To save some on manufacturing, the number of coolant channels in the block were reduced. While things looked good in the limited testing done, it wasn't enough cooling in all situations, and motor oil got cooked. Luckily this time, the problem came to light after a thousand or some deliveries, and not after tens of thousands.

You can damage the stud threads when taking the wheel on and off.

How will the threads in the hub for bolts get damaged? Most likely cause is from installing the bolt wrong. Same can happen with the bolt and stud I suspect the bolts and nuts are softer than the studs and hub, so they will be damaged first.

Assuming damage too great to simply retap the bolt hole, the hole can be drilled out, and tapped for a slightly larger bolt. That can be done without removing the hub. Recutting a stud with such level of damage isn't recommended, as it will make it a smaller diameter and weaker. Taking the hub off and replacing it is the only option then.

 

Reading the OP's link, it's not just the cone shaped bolts that fail to ensure proper clamp load - nor just the "add a washer" to increase clamp load. At least not for USA customers:

Hey - don't forget to put the washers back in, when you change out a flat

I wonder if the new / USA wheels will just be re-worked wheels .... or will Toyota forge / cast totally new product.
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maybe soon we will begin getting reports of the cars performance, charging efficiency etc

 

Or just for the hydrogen fuel cell, hybrid, and ICE versions (I listen to Toyota’s CEO.)

Bob Wilson

 

I hope as I continue to age if I ever get to the point of being sarcastic, closeminded and mean a trusted friend would take me aside and talk to me about it.

 

That is incorrect. We saw quite a number of review drives from the same review vehicles. They drove many miles. In fact, we know of one who depleted the pack entirely. Even their repeated sharp corners and hard braking did not exhibit the problem. There were 3 specific vehicles elsewhere that ended up revealing bolts had loosened and only 1 had the wheel actually come off. Of course, the title of this isn't correct anyway... since the solution also included altering the hub surface and using a different alloy for the bolt itself.

 

Don't expect much. Efficiency isn't a priority for most supposed journalists. They still focus on range. There may actually be something in terms of charging curve software tweaks, but I wouldn't expect much since reports for other vehicles remain limited & vague.

What will be fascinating is the discovery of that infrared heater. Radiant warming is new, something Toyota will clearly have an advantage with. That type of innovation will rub those favoring other automakers the wrong way.

 

I tried that with a friend - just once. He told me to,
"get off my lawn!!"
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