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.