How do I know if I need hubcentric rings?

[Dashome]

As the subject stated I was curious if there was some sort of rule to be followed or if they should always be used. I figured this would be helpful to me in the future as well as other members.

More specific for my case though, I have an 09 WRX and know the stockers are 17x7 et55 and have a set of RPF1s that are 17x8 et45 and ready to put on. If they happen to be required, does anyone know the size offhand? If not, no biggie.

Thanks for your help!

[brfatal]

Bust out a ruler and measure the hub hole. If you measure more than 56.1mm, you need rings.

[Dashome]

Gotcha. Thanks. It seems like way too many people decide to get a nice new wheel setup, yet feel like cheaping out. So many people don't bother it seems like. I am glad I asked.

[mmiller2002]

My wheels came with plastic rings frm tirerack.com. I actually asked about metal before the sale and was told they were metal, but they arrived with the plastic. Those rings only help line up the wheel to the studs during mounting, correct? Once the wheel is mounted and torqued, they are basically non-functional.

[brfatal]

My wheels came with plastic rings frm tirerack.com. I actually asked about metal before the sale and was told they were metal, but they arrived with the plastic. Those rings only help line up the wheel to the studs during mounting, correct? Once the wheel is mounted and torqued, they are basically non-functional.

No. WRXs use hubcentric wheels, meaning that a majority of the stress is handled by the hub. If the hub bore on the wheel is too big, then the only thing holding the wheels in place are the lugs, which are not designed to handle that. Problems from wheel vibration to lugs breaking and wheels coming off while driving are possible. If the hub bore is too small, you won't even be able to mount the wheel.

[Merk247]

+1 not a good idea to throw on wheels that dont center on hub .

on a side note ive seen many aftermarket wheels with metal rings rott to the hub flange or the wheel i wouldnt use them

[mmiller2002]

No. WRXs use hubcentric wheels, meaning that a majority of the stress is handled by the hub. If the hub bore on the wheel is too big, then the only thing holding the wheels in place are the lugs, which are not designed to handle that. Problems from wheel vibration to lugs breaking and wheels coming off while driving are possible. If the hub bore is too small, you won't even be able to mount the wheel.

How can all that stress be handled by a plastic ring? Doesn't make sense.

I'll have to dig through my emails with tirerack to see what they said when I fussed about not shipping the wheels with metal rings like they originally said when making the sale.

[brfatal]

Tire Rack can give you a better answer than I can. I'd imagine that the plastic isn't exactly soft, and all it has to do is keep the wheel centered.

[lytlec]

Crazy! I was just about to ask the same question...I just ordered 17x8 Rota G force and the hub bore is 56.1mm...this thread just answered my question! I don't need any rings!

[wrx wagone]

The reason the rings are plastic is that they actually don't do much at all. They do help center the wheel and they definitely don't hurt anything, but it is actually the frictional force generated by the clamping for of the lug nuts that provides the forces to balance the forces acting on the wheel both from torque and shear.

The tapered design of the lugs nuts will center the wheel, but you need to make sure the wheel is flat on the hub, and the lug nuts are torqued properly. If you don't think you can do this, then you should likely get some hub centric runs to assist you.

If the hub centric ring was intended to support load, it would need to be a press fit.

[brfatal]

The reason the rings are plastic is that they actually don't do much at all. They do help center the wheel and they definitely don't hurt anything, but it is actually the frictional force generated by the clamping for of the lug nuts that provides the forces to balance the forces acting on the wheel both from torque and shear.

The tapered design of the lugs nuts will center the wheel, but you need to make sure the wheel is flat on the hub, and the lug nuts are torqued properly. If you don't think you can do this, then you should likely get some hub centric runs to assist you.

If the hub centric ring was intended to support load, it would need to be a press fit.

Thanks. Obviously its job is to help secure the wheel centered in it's place, but I figured it was also more load bearing than the lug bolts themselves considering the lug holes in the wheels are larger than the bolts.

[Rodman]

but I figured it was also more load bearing than the lug bolts themselves considering the lug holes in the wheels are larger than the bolts.

This is the only way to get the wheel to align with the bolts true position. Each wheel bolt hole and nut have a conical surface that aligns to the center of the bolt. This is how the wheel is held in place.