Hub-centric v. NON hub-centric spacers

[D.L.]

I would like to buy some aftermarket wheels for my box, but was told I would need 5mm spacers in the rear. I've been looking around a little, and was wondering if somebody could please tell me the difference between hub-centric and NON hub-centric spacers?

If the spacers are for wheel fitment only, is there a significant difference between the two functionally? Any information on wheel spacers or experiences with them would be appreciated. Thank you!

(FYI; the wheel sizes are 19x8.5 et 45, and 19x10.5 et 50. Do I really need spacers?)

David

[MNBoxster]

Hi,

Hubcentric Rings or Spacers are designed to fill in the gap between the Hub of the Car and the Center Bore of the Wheel. Most Aftermarket Wheel Manufacturers design their Wheels with a Center Bore large enough to fit on many different Cars instead of for a specific application.

Therefore, since Wheel Manufactures make their Center Bore large enough to fit most Cars, most Wheel fitments have a gap between the Hub and the Center Bore. This gap usually doesn't allow for the Wheel to fit Hubcentric but rather Lugcentric which can cause vibration. To fill the gap and ensure the fitment is Hubcentric, Hub Rings or Spacers are used.

One thing you might want to consider though, although 19" Wheels may offer the best aesthetics, they are not usually the best performing size rim. For the Boxster, the 18" rims seem to offer the best compromise between Aesthetics and Performance. It all depends on what you're after. Hope this helps...

Happy Motoring!... Jim'99

[mjw930]

You will probably need those 5mm spacers on the rear but in that size they will probably not have a hub centric extension since the wheel should still be able to engage enough of the centering hub already on the spindle to work correctly. You will need longer lug nuts.

[eslai]

Hubcentric is nice because it helps take load off of the lugs, but then they're supposed to be able to support the wheel, so it shouldn't be an issue, although most people will try to tell you that it IS an issue.

Cone-seated lug nuts (which I'm assuming the Boxster uses...I haven't taken off my wheels yet) will usually hold the wheel centered just fine. I've used non hubcentric spacers and/or mounted wheels without spacer rings to make the wheels hubcentric for years without problems with wheel balance on the race track or street. As long as you tighten the nuts in the proper star pattern and torque them down properly, it's all good.

Technically, I'd go with hubcentric stuff all the time, but if you can't get it or it isn't affordable, I wouldn't sweat it. A lot of wheel manufacturers will try to sell you silly little plastic rings for hub sizing. Yeah, THAT'S gonna work...

[mjw930]

I think you all are missing the point, there's no possible way to make a 5mm spacer that also extends the hub (like a hub centric spacer). The center hub that the wheels use to center themselves on extends at least 15mm on the Boxster. Anything short of a 15mm spacer will, by definition, not be a hub centric spacer.

Note the 3 tangs on the center of the hub in the attached picture. Those are the centering tabs the wheels use to center themselves. A spacer would have to be thicker than these tabs to require it's own hub center thus making it a "hub centric" spacer.



BTW, if you decide to mount a wheel that isn't machined with a 71.6mm hub center on the Boxster don't be surprised when the car vibrates the steering wheel out of your hands above 70 mph.

[D.L.]

mjw30,

thank you for the description and visual aid. As mentioned before, I was looking into some aftermarket 19 inch wheels but I'm having second thoughts now....

[eslai]

Originally Posted by mjw930

I think you all are missing the point, there's no possible way to make a 5mm spacer that also extends the hub (like a hub centric spacer). The center hub that the wheels use to center themselves on extends at least 15mm on the Boxster. Anything short of a 15mm spacer will, by definition, not be a hub centric spacer.

Note the 3 tangs on the center of the hub in the attached picture. Those are the centering tabs the wheels use to center themselves. A spacer would have to be thicker than these tabs to require it's own hub center thus making it a "hub centric" spacer.

BTW, if you decide to mount a wheel that isn't machined with a 71.6mm hub center on the Boxster don't be surprised when the car vibrates the steering wheel out of your hands above 70 mph.

No, no--I'm not missing the point, I'm mixing topics really, sorry 'bout that.

I wasn't really talking about hubcentric spacers specifically. I was talking more about wheels that aren't machined with the proper hub center and the things that people will normally sell you to alleviate that problem, being either hubcentric spacers or just hub centering rings.

So I was kind of refuting your final point there--I've had many different wheels on many different cars, both on a race track and not on a race track and even without the proper center bore they didn't vibrate. The cone-seated lugs center the wheel just fine. Any other vibration is usually a wheel balance issue.

But, I don't really know how well that works on the Boxster, all cars are different. I'd never buy wheels for the Boxster that didn't have the proper centerbore anyhow--why would you want to when there are so many wheels made specifically for Porsche, eh?

On another point, I've even raced cars that were using cheapo Pep Boys spacers that you have to kind of "feel" and get as centered as possible. Pretty iffy, but even that can be made to ride and race at high speeds if you're careful enough about it and don't mind the ghetto factor.

[eslai]

Originally Posted by D.L.

mjw30,

thank you for the description and visual aid. As mentioned before, I was looking into some aftermarket 19 inch wheels but I'm having second thoughts now....

Why? It's not unheard of at all to stick 19-inch wheels on a Boxster. If you're worried about the lugs, changing those isn't a big deal.

[mjw930]

Originally Posted by eslai

Why? It's not unheard of at all to stick 19-inch wheels on a Boxster. If you're worried about the lugs, changing those isn't a big deal.

19" wheels on a 986 are not accepted by Porsche and, depending on the wheel/tire combo, can cause problems down the road if they are heavier than the heaviest 18" wheel/tire combo Porsche authorizes.

Besides, the only reason you would do 19's is for looks, they aren't going to improve either the handling or the ride.

Save your $$$$ and buy a better set of 18" tires.

[eslai]

Sorry, I'm a 987 guy, didn't realize that 19's weren't allowed on the 986.

I agree that 19" wheels wouldn't be for any other reason than looks--987 or 986. But at least for 987, there's nothing illegal about it.