The whole hubcentric thing
 

I haven't found a good explanantion. But I've come across many cars riding on wheels where the bore of the wheel is larger than the hub. So it is riding on the lugs, so to speak. Well, people always seem to bring this up with wheel spacers but not wheels in general. If the bore of my wheel doesn't match, within some tolerance, the hub, shouldn't i machine some kind of spacer to fill this gap as I am riding on the lugs? Any experts out there that can clear this up for me?

It's not a problem, some vehicles are even designe to be lugcentric. It's not a problem to have the hub bore on the wheels larger than on the hub. The car is supported by the large clamping force generated by the lugs forcing the wheel and brake rotor surfaces together, the weight is not supported by the hub lip on the inside of the wheel. That's there more to make it easier to put on the wheels and allows you to tighen them with the car on the ground. With a loose fit on the hub just tigthen the lugs with the car in the air and it'll be no problem. If you're still worried you can get hubcentric rings to fill the gap. They should be available at some tire stores, and are available online from several places, Discount Tire Direct for one.

That's what I thought. I would think for the car to be fully supported by the hub lip, the wheel would have to be pressed on. Thanks for the explanation of that.

What about with spacers then? Why a hubcentric spacer? Does it just provide more stability or does it help with the clamping between the rotor surface and the wheel?...or both?

Name one.

Andrew

Complete bologna.

https://www.rx7club.com/suspension-wheels-tires-brakes-20/safe-pics-467209/

https://www.rx7club.com/showpost.php...6&postcount=11

ur wheels may not be completely centered because there is some movement available before you tighten your lugs down...u need to use hubcentric rings or you may experience vibration that you may not even notice at high speeds due to the wheels being off centered..this causes uneven tire wear and is probably dangerous over 120mph

What is the tolerance between the hub lip and the wheel bore for proper fitment? I haven't fit the wheels on yet but I would like to know so maybe I can machine something out later on. I'm assuming the OD would have to match the wheel bore's ID within a couple thousandths?

For a vehicle that's lugcentric I've been told that the late 90's Toyota Tundra TRD model (IIRC) was lugcentric. I've read that the Ford Contour is lugcentric, and the F-bodies.

Do you really expect the entire weight of the car to be supported by a tiny little lip on the hub (high stress), or with friction over a large surface area that's tightly held together (low stress)? The hub lip is there to center the wheel when mounting it, it's not the primary method of holding the car up.

I still use hub rings on my wheels, it's a conveniance thing though. I'll happily remove them and run without them for an upcoming track day, as I don't want them melting. As for vibrations, that's why you tighten the wheel with the wheel in the air. There's more chances for the problems that DamonB's post brought up when spacers are used, but without them, there's not a lot of chance that the studs will be bent to cause an off center wheel.

Hub centric rings are purely for centering the wheel on the hub and has nothing to do with the strength... the best way to center your wheels if you do not have hub rings is to torque your lug nuts before lowering the vehicle on the ground.

My Jeep Wrangler did not have hub centric rims and saw forces at least ten times that of a normal vehicle... and I never once had a problem, neither did any of my other rock crawler buddies

Another data point:

Centerbore manufacturing tolerances are generally tighter than lug hole manufacturing tolerances. So even if both wheels are carefully installed, hub-centric wheels will center more precisely then lug-centric, on average. I got this information from an engineer at a major automaker who deals with vehicle performance issues of this nature on a day-to-day basis.

-Max

The looser tolerances on the stud to hole gap isn't so much of an issue provided your wheels and lugs are concentric, that way they will self center.

IMHO there's far too many vehicles out there running around trouble free that don't have hubcentric wheels (designed that way), or don't have the correct centerbore on their wheels for the predictions of doom and gloom to be anything but false. No offence is meant to those who beleive it and posted to that effect.

I've never experienced any issues with wheels mounted in a "lugcentric" fashion. But I'd like to hear more on the matter. Max, would you know anything about those tolerances, like how tight they are?

Here are a couple quick articles I found using Google. I don't believe everything I read on the internet but maybe they can spark some more discussion. It just seems like putting more distributed weight on the hub as opposed to the wheel studs, which could shear under that stress, would be the better way to go. But there are people here who haven't had a problem with it and there are others who think it's dangerous.

Here are the links:
Hub Rings

Hub Spacers

You misunderstood. The centerbore is manufactured with a tighter tolerance than the stud holes. Say the centerbore was machined off-center (relative to the wheel) by 0.002", and the lug holes were drilled off-center by 0.05". Perfect hub-centric mounting would have the wheel off-center by 0.002". Perfect lug-centric mounting would have the wheel off-center by 0.05".

I don't know the real tolerances (and clearly, it varies within the industry of so many wheel makers). I used numbers in the example above to illustrate what the numbers mean.

-Max

Clearly, there are many cars running fine with wheels that are only lug-centric and not hub-centric. Lack of hub-centricity is not going to make your head explode. But there are also a huge number of cars on the road with various problems like vibrations, brake shudder, worn out suspension parts, etc. Most of them aren't severe enough to cause the vehicle owner to seek a remedy. But cars running hub-centric wheels surely have less of these problems than cars that aren't running hub-centric wheels, on average.

I own three sets of aftermarket wheels. One was manufactured to be hub-centric. I have rings for the other two sets to make them hub-centric. I value hub-centricity. When comparing wheels for purchase, I would prefer the hub-centric wheels, all other things being equal. If the wheel is not hub-centric, I think it is worth paying for rings to make them hub-centric. That said, I am missing one ring from each of the two sets, and one set of rings is plastic (sloppy). :)

-Max

If I don't end up running spacers, I think I'll machine some aluminum rings when the 7 gets going. Thanks guys.

Yea, I agree, hubcentric wheels are good, they're more conveniant and help reduce the likelyhood of problems, I just don't agree that it's necessary. Given the option I'd run (and do currently run) hubcentric wheels. I'm sure the hubs do take some of the load, but it's definetely not the fact that they're taking all the load, or even most of it, it'll be shared by the studs, the friction over the wheel mounting surface and the hub.

I see your point now about the tolerances.

I'd think that most of the problems people encounter with non-hubcentric wheels is due to improper use steming from ignorance (tightening the wheels with the car on the ground).

My Toyota 4runner is hub centric. You have to make sure that the tires are mounted them ballanced on a hub centric wheel ballancer of they use a adapter.
As far as wheel spacers go, I put some spacers on my wheels to try to get them to stop rubbing. The wheels had a terrible shake to them on the freeway. I took the spacers off and the shake went away.

I had a 68 VW bug that had lugcentric wheels.

The hub hole would have to be a perfect match to make any difference. Which it is not or you'd hardly be able to get the wheel on or off. The lugs have a conical surface which makes for a perfect fit when tightened down.

I agree that it seems like it might work this way, but in practice it doesn't really go this smoothly. The hub hole is a good enough fit to substantially improve the centering of the wheel during mounting. The tapered lugs center a bit sloppier than you might expect. The lug holes are typically not manufactured that precesely. And it is not uncommon to have some crud on the lug nut or taper.

-Max