WTB 04-09 Prius Winter Wheels and/or Tires - Kansas City

I recently got a set of steelies from TireRack.com -15x6 for $52 each plus shipping. I thought about used alloys but they were around $100 each, and that was beyond my budget. I got 4 Blizzak WS-80s for the price of three + $1 from my local Toyota dealer, including fitting, road-hazard ins. and alignment check. Good luck with your search!

 

If you get a compatible Toyota steel rim, chances are it's center hole will be a perfect fit on the hub. If it's a generic steel rim, it'll likely have an oversized, one-size-fit's-all center hole, and will require an adaptor ring. Well, it should have: otherwise, all the load is on the lug nuts; with a close fitting center hole and hub the rim is held much more solidly.

It's not the end of the world to use adaptor rims, all the aftermarket alloy rims require them, just food for thought. I'd think there's a Corolla rim that'll work, but you'd have to check with a dealership or two.

 

??? if the hole is over-sized and one-size-fits-all, I'm not sure that I understand why it will need spacers? (…pardon my ignorance!) My steelies seem to fit nice and snug, and I was careful to check with the experts at TireRack about the need to use the provided lug-nuts rather than those from my summer alloys (just in case)

 

Ideal is when the hole in the rim is a perfect fit with the hub protrusion. This is typically the case when a car manufacturer produces the rim: the rim is locked laterally in position, and the lug nuts only job is to hold the rim.

But if the hole is oversized, and no adapter ring is used, then the lug nuts are also responsible for keeping the rim centered, there's a lot of lateral forces on them. An adapter ring will have outside diameter per the rim hole, and inside diameter per the hub protrusion, basically bridges the gap, and makes it so the hub protrusion is once more locking the rim laterally.

This is a commercial link, but gives a quick overview:

Why you should use the Hub Centric Rings? - HubCentric-Rings.com

 

What you say makes perfect sense, and I must admit that having the face of the bearing surface of the wheel held flush against the hub is better than having it "bridged". I understand that the "coned" shape of the bearing-surface of the lug-nuts helps to keep the wheel centered in the way you describe. I (erroneously) assumed the spacers were simply to correct any misalignment of the hub/wheel geometry¹ caused by using non-OEM wheels. I guess I hadn't though too deeply about it!

¹ see recent threads re. wheel/hub alignment (there was a link posted, but I can't seem to be able to find it…)

 

Yeah, I just became aware of this in the last year or two. If the rim opening is oversized (typical with aftermarket rims) it'll likely be "ok", but there's more stress on the wheel studs and nuts, and there's more possibility of the wheel getting a bit off-centre. Just picture every time you hit a speedbump or pothole: the studs are getting a lateral stress, tensioning on one side compressing on the other.

How much is debatable, but it's good practice with such rims to put in adapter rims. I think tirerack gives you a heads-up when you're ordering, whenever the rim has oversized hub opening, basically all the time with aftermarket.