Aftermarket Spare Tire Kit for 2024 Prius Prime

I'm still waiting to hear back from ModernSpare and get their thoughts on this issue, but I don't agree with your statement that all of the shear forces are handled by the studs. That would be true if the wheel was free to slip or rotate on the hub but it is clamped together and the friction force between the wheel and the hub provides strong resistance to shearing forces. I agree that a tight fit at the hub center would be ideal but not sure how important it is for a temporary spare solution.

KH

 

It has been my understanding that the lug nuts on a hub centric vs lug centric wheel are different in design/shape. Is this accurate?

 

After market wheels designed to fit a variety of vehicles are usually lug centric. From Discount Tire:

"While lug-centric wheels are centered around the lug nuts rather than the hub bore, they can be safely installed without worry"

I think the lug centric design spreads the loads across the wheel/hub interface and the studs without the additional load bearing capacity of the hub.

Bottom line is I don't think we have to worry about shear loads when mounting a lug centric wheel from ModernSpare.

KH

 

From Google A.I.:

No, lug nuts are not different shaped on lug-centric and hub-centric wheels, but the way the wheels are mounted to the hub differs:

• Lug-centric
  The wheel lugs center and support the wheel when the lug nuts are tightened, with no support from the hub. Lug-centric wheels are safe to install, but they may cause vibrations at higher speeds and when braking. They also require mounting on a wheel balancer through the lug bolt pattern for accurate balancing.
  
  
• Hub-centric
  The wheel fits snugly against the hub, with support from the wheel lugs and the hub. Hub-centric wheels are better for stability and can be centered correctly on the hub during installation. All original equipment manufacturer (OEM) rims are hub-centric.

It seems there is a chance a lug centric wheel can move slightly on a hub from road forces but I don't think it is a big problem for a temporarily driven spare. I wouldn't do it in a performance application.

KH

 

I knew about the other differences, but for some reason I thought the lug-centric nuts themselves had a slightly different conical/tapered shape that helped center the rim on the lugs.

 

They do; that's why tire shops shouldn't just buzz lug nuts down with their air tools. Once the lug nuts come in contact of the rim, the nut needs to be gently tightened down while wiggling, centering the rim around the wheel studs. Once that first nut is down, you'll notice all the wheel studs will be centered on the rim.
You'll still need to go around with a torque wrench and you'll notice that first nut has loosened up once the rest of them are tightened to specs. That's the rim continuing to center itself onto your axle. I hit all of my lug nuts at least 3 times to ensure everything is tight. There shouldn't be any movement on the second pass. The third pass is just a safety thing I do.

 

Or,,,,,, you can just get the proper hubcentric ring so your rim fits the hub properly.
Glue them in place if they aren't a tight fit, like on a steelie spare tire rim.

 

Doing a little more research I think some hub centric lug nuts may be shaped differently than the conical lug centric types in some applications. Large trucks and trailers for example may use hub centric lug nuts with flanges. The flange type obviously wouldn't seat in a way that helps center the wheel.

KH

 

I just got a steelie spare rim and placed my best old tire on it for a spare. I was wondering if I needed to buy a set lug nuts for it or if the OEM nuts would work. The OEM nuts has a .25-.50 shank but also conical on the ends. I buttoned it down on the drivers front position and gave it a test drive to 65 mph - works fine. FYI....

I wouldn't glue anything in place - if it doesn't fit it shouldn't be spinning a few thousand RPMs on your car, IMHO. It can become a projectile and the hub heats and cools with brake use and weather conditions.

 

Good point. On a steelie the ring could slip out to the outside,, maybe.
The wheels I used them on were alloys and the ring couldn't leave the wheel in that direction. A smudge of silicone sealant kept them where they belong in the wheels. Just makes it easier at wheelset changes.

But then you're using the stock lug nuts on a steelie, without the correct contact area. Spend the big bucks and buy 5 of the proper lug nuts and keep them with the spare tire.

 

^ Stock lug nuts, the one designed for alloy rims, with the washer, also have a tapered end, suitable for the OEM spare rim at least.

General comment: Gen 4's without a spare at least included a scissor jack (crappy one compared to Honda's) and a lug wrench. With each gen they "progress"...

 

Pointless pedantry - the Prius's wheels won't reach a few thousand RPMs.

1000rpm would be about 80mph.

 

I learn something new here almost every day. Like today I learned that Gen 3 Prius with a donut spare has lugs that fit it, I guess if that said Gen 3 came with Alloy Rims, since I don't know if any Gen3s came with regular steelies from the factory.
A lot of posts here leave plenty of room for having to read between the lines or just be happy with the content as presented, mine included for that matter.

I'm not sure I also get exactly what @devnull hehe I mean @NullDev is asking above. And if he's asking specifically about his Gen 4 or rather across all Gens whatever they are equipped with from factory or modded with non OEM rims.
For gen 4 prius specifically, I believe they all came with hub centric alloy wheels from factory. I know that for me when I got a set of steelies for my winter tires I also needed compatible cone shaped lugs for those wheels, since that were going to be mounted for several months out of the year. Frustrating for sure, although in my case just one of the minor addressable frustrations that come builtin to most any car one can find for sale now or throughout the history of cars in general. </rant> I must be in one of those weird moods today.

 

Yeah, I should have explained further in my post rather than just asking what seems like an odd question. I was trying to ask if it was possible to determine OEM lug-centric vs hub-centric by just looking at the shape of the lug nuts.

 

I doubt it would be easy to tell the difference if only looking at the lug nuts or bolts.

 

I found this on Amazon:

 

Finally got a response from ModernSpare about hub centric vs lug centric wheels, etc so we can keep beating a dead horse:

"Hello KH,


So very sorry for the slow response. Members of our design and development team have been out of town, and we wanted to get their technical expertise on your question regarding the nature of hub-centric wheels and the spare.


Bear with us as we get deeper into the technical details on this question and also share with you our plans to alleviate your concerns. First of all, rest assured that the studs ( or lug bolts for some brands ) on any given wheel are not weight-bearing. Although this seems counter-intuitive, the mating surface of what is called the “pad” of the wheel, when properly torqued to the face of the wheel hub, has an incredibly high friction coefficient, and this adhesion is what bears the weight. This is even the case for severe or extreme conditions and road hazards. It is common for a wheel to sustain heavy damage long before that mating surface is compromised. Contrary to what some may believe, a hub-centric wheel that more precisely matches the hub to the wheel’s center bore is not reliant on the vehicle’s hub as a weight-bearing surface.
We must closely adhere to Federal Motor Vehicle Safety Standards for passenger-car wheels and the FMVSS standards do not call for a wheel to be hubcentric.


Some of the wheels in our catalog are actually hub-centric as they allow for a much-improved installation experience for vehicles that use lug bolts and do not have studs to help line up the wheel properly.
All this being said, we would rather our customers not have concerns about the safe use of our spare tires. For the Prius and similar models that use this wheel and that have the typical Toyota center bore, we will be incorporating a metallic hub ring into the kit. This will effectively close that gap in the center bore. These are not weight bearing just as a hub-centric wheel is also not weight bearing; however, the metallic hub ring does comply with European standards for passenger cars, which tend to be a bit more stringent than the US FMVSSs.


Feel free to reply with any questions, and if you would like us to send one of the new hub rings, we certainly can."

I will ask them to send me the hub ring since I paid for the whole deal anyway.

KH

 

I purchased one of the EZ Spare tires for $275.00 and secured it with ratcheting straps:
2024 Toyota Prius Spare Tire&ndash; EZ Spare Wheel

 

Nice, did the aftermarket wheel include a metal hub centric ring?