Hub Centric Hubbub: The Argument For — And Against — Using ...

Yasenia says: December 26, 2019 at 2:37 pm

Actually I, and automotive engeneers I know or have talk to, disagree with Mike.

First, I Know this is long, but I feel that this subject needs a good explanation. That could not be made in one short paragraph.

I wish that people who write this sort of stuff said what their quealifications are. I say that because I often read articles that sound impressive, but when I compare what they say with what real experts (engineers/designers) say, it doesn’t always match.

There has been a long debate about centric rings. Some say that the idea behind them is nothing but BS. Nothing but a money making scam from wheel manufactures.

Being a girl, guys often think I have no idea what is mechanically going on in my car or don’t have anyone knowledgeable to ask. This is not the case by far.

I actually been to auto repair school and got my A&P certificate from the FAA. That is right kiddos, I actually went to A&P school and became a Aviation Maintenance Tech. I have worked on everything from skateboards, to bicycles, motorcycles, big rigs, to all the way up to wide body aircraft such as 767’s, DC-10’s/MD-11’s, A330’s, A340’s, and others. The only forms of transportation I have never worked on are boats and trains.

I also throughly educate myself before doing any type of modifications to my car, and I know the people in the auto industry (such as engineer Fujita, a Japanese automotive engineer who designed the fuel injection system for Mitsubishi or Suzuki (I can’t remember) cars in the late 80’s and is now working for GM. As well as Ed Howardstein, a thermal/metallurgical mechanical engineer, among others.

I keep getting guys telling me or I keep reading online that hub’s do not carry any loads. That supposedly the wheels are held in place by the friction created by the lugs.

Well, from all my reading, phone calls, and road trips, I have come to the realization that that is not true. In my research a friend referred to the engineering dept at Katana Wheels. What was said to me on the phone pretty much reflects what it says in their site:

“The other element that affects directly whether a wheel can be bolted onto a car is hubcentricity. Long ago, in the deep mists of time, wheels were located by taper of the lug nuts or bolts. This could lead to all sorts of problems, but they can be summarized by saying centering was liable to be less than perfect, and the sheer stress on wheel bolts or studs could be enormous. We are not aware of any passenger car wheels now made that are not hubcentric.

Hubcentric wheels have a hole at their center that fits closely over a round feature on the hub, serving to center the wheel on the axis of the spindle, as well as bear the verical weight of the vehicle. The wheel bolts or studs then serve simply to hold the wheel onto the hub, and are loaded only in tension, where they are strong. If the studs were required to absorb vertical forces, they would be loaded in single shear, the weakest arrangement for any fastener. Factory wheels are all machined to fit their specific application exactly, and some for the better aftermarket wheels are, too.”

Hmm, knowing what I know about fasteners, such as the metallurgical properties of fasteners and their design, I can say that that makes more sense than any other argument I have read or heard about hubcentric wheels not caring loads.

If one does the math, which I will spare you from, tightening your lugs at 80-100 ft-lbs, would not generate sufficient friction to prevent any lateral movement of the wheel from the center of the hub horizontal axis if at highway speeds one were to encounter anything larger than a small crest or other imperfections on the road surface, extremely hard brakes, and so on. Or even a larger pothole at lower city street speeds could create enough force to give you trouble. And that is only putting the weight of the vehicle at 2,000 lbs.

Specially if you switch from a high profile to a low profile tires. I am sure that we all know that automotive designers do take into account the Free Radius, Static Load Radius, Deflection, Section Height, and so on when designing suspension systems. I am sure we all know that is because tires are part of the suspension system. A tire with a higher Section Height (“profile”) absorb more road “shock” and gies you a smoother ride than a low profile tire. That is basic knowledge.

I am not saying that whatever friction generated by the tightening of the lug nuts don’t help, but to say that that is the only factor preventing vertical movement would be ignorant. Specially if you have a wheel lug lock. I have noticed that most tires shops do not tight those as much as the other lug nuts.

I started suspecting this when I put new wheels and tires on my 2017 Honda Civic. They installed centric rings but where made of polymer. At first there was no problem with the car. Until one night I was doing about 90-100 of the freeway – yes I can be a little speed demon when road conditions are right. Such as on a late Sunday night when LA freeways have less traffic than normal. It was not long after I jumped on the freeway before I started to feel vibrations in the gas pedal and steering wheel. We all know that for us girls vibrations can be good and fun (grin), but not good or fun when coming from the car’s suspension system.

Eventually my friend Fujita called me back. He told me that he’d talked to a couple of guys from the suspension engendering dept. at GM. They told him that YES, the hud DOES carry loads, and to ignore those who say that it does not carry loads.

They added that back in the days they discovered that lugs were failing in part due to lateral load sheering. Many attributed (many still do) solely to over torquing of the lug nuts. But they discovered that that was only part of the problem. You can actually tell what went wrong with the lugs by examining where and how they broke under a microscope or other none destructive testing. So manufactures switched to hubcentric wheels to help ease the lateral sheer off the lugs, among other benefits.

Makes sense to me base on my research and after noticing what I refer to as “compression load damage” on the polymer rings I took off. And when I loosen to lug nuts I used a torque wrench and backpedaled on the torque wrench to figure out how much torque they had used at the tire shop. It turned out that the lug nuts had been over torqued by 11 ft-lbs. But that was not the cause of the damage on the junk polymer rings. It appeared to us that the rings had slight lateral compression damage. Even with the wheels over torqued.

But think about it, there is a reason why pretty much every auto manufacture have switched over to this type of hubcentric set up. Other wise they could just use guide pins or other guiding method to center the wheels when mounting them onto the car. I don’t know about you, but again, that makes sense to me.

But if it doesn’t to you, try the following. Install a lugcentric wheel on your car designed around a hubcentric design. Regarles of how much you tight them they do move from their original location. You can see evidence of this in the lug holes on the wheel. They go out of shape from the stress imposed on the wheels by road loads. I actually have pictures of such wear but can’t post them here.

Charles C. Roberts Jr, PH.D, P.E., (an engineering consultant in the areas of accident reconstruction, failure analysis, structural analysis, heat transfer, fire origin analysis, computer analysis, mechanics, and biomechanics) puts it this way.

“It should be noted that hub-centric and lug-centric wheels are distinct designs with different stress levels at different locations. Substituting a lug-centric wheel in place of a hub-centric wheel can decrease reliability, especially in high wheel-loading and impact- loading environments.”

Hmm, “stress levels at different locations.” You mean to tell me that if I used a lugcentric in a hubcentric setting, the friction created by the tightening of the lugs won’t be enough to keep the wheel from moving around under lateral stress loads? Hmm, who could had guessed that?

But wait, I thought that hubs don’t carry any loads and friction is enough to hold the wheel in place. Not just that, if the center bore diameter of the lugcentric wheel is too large for the hub my car, isn’t that the same as a hubcentric wheel with a bore that is too large for the hub? Neither one will fit snug around the hub. Which means that lateral movement could be possible.

I had to find out if I was right. So I invited my friend Jason (thermal and mechanical engineer) to go with me in a little road trip to a friend’s of a friend’s auto dismantling center in Sun Valley, CA. We looked at after market wheels and discovered that some had signs of wear similar to that one would find in a lugcentric wheel installed on on hubcentric setting. We looked for any hubcentric rings still installed on the wheels or marks that some had been installed previously, but on the wheels with the oval wear none were present. Hmm!

Once I got home I decided make one more call. I called Versus Racing, the manufacture of my new wheels. I poke their brains about the ins and outs of hubcentric wheels and their thoughts on hub centric rings. They pretty much told me the same thing every other qualified person I’d spoken to told me, “the hub IS a load bearing component…”

I don’t know where other people get their information, but based on the answers I got from engineers/designers and the tell tell signs left behind on the used wheels we inspected, and my own experience with my car, I would have to disagree with the idea that hubcentric wheels to do put loads on the hub.

You can believe whatever you want. Hell, you can believe that there is such a thing as a Friction Fairy that magically creates enough friction by the tightening of lugs to prevent lateral movement of the wheels.

As for me, I will go with what more than not engineers say. Give me some good quality metal hubcentric rings that fit tightly (men in particular should know that things that fit nice and snug is usually better than loose, wink wink) between the wheel and my car’s wheel hubs. Oh and while at it, don’t give me none of that polymer or low quality metal junk. Thank you very much! In my car switching from polymer junk rings to high quality metal rings, made a world of difference.

By the way, I think that someone should make and sell stainless steel or other types of metals that are more resistant to corrosion for those who live in area where it snows and they use salt on the roads.

I have a friend in Middletown, Ohio. He also had problems with his after market wheels. I suggested for hin to get rig if the polymer crap and instant food quality metal rings. Bur knowing that it snows in Ohio, I suggested for him to coat the rings in a corrosion preventing material. Iodine or paint. Can’t recall the name of the product he used, I had never heard of it, but I guess in a year or two we’ll find out if it worked. He also told me that he doesn’t mind taking his wheels off once per year and cleaning the area or even replacing the 15 dollar rings.

Anyway, at the end I did the same thing, I took the wheels off my car and removed the junk polymer rings they installed at the shop and installed high quality metal rings and used an actual torque wrench to torque the lugs. All vibrations went away and I haven’t had any problems at any speed.

Let’s imagine that no one, not even engineers (wink wink) knew the answer. Some said that the hub does carry weight, some that it doesn’t. Wouldn’t you rather be on the safe side just in case? Jumping from a second story floor onto concrete gives you a 50/50 chance of surviving the fall. I don’t know about you but I rather not jump unless there was no other choice. Yes is faster than using stairs or waiting for the elevator, but why take chances. Am I right ir an I right?

Be careful where you get your information. There are a lot of people online trying to pass themselves as some expert. Oftentimes they just pass along misinformation they read or heard somewhere and that they accepted as the truth. Being a tire/wheels sales men for years, being a car enthusiast, or even a mechanic for years does not really make anyone an expert. Research what others tell you. Read what well seasoned engineers and other real experts have to say.

Trust me, no engendering dept will spent the time and money designing something just for looks or because they have nothing else to do. Everything on a car has a purpose. Even the body work was not only designed for good looks, aerodynamics is computed into the whole equation.

Growing up around auto and big rig mechanics, and later getting into the automotive repair field, I saw a lot mechanics performing a lot of “Mickey Mouse” work. “You don’t need this, you don’t need that, hell, who needs a torque wrench!” Type of mentality. That’s a luxury, more like a dumb and ignorant way of thinking, that I thank God is never seen in aviation.

In aviation all parts are certified, using torque wrenches are a must just as a hammer is a much to a carpenter. Nothing of the guessing how many in-lbs/ft-lbs you have tighten a fastener. Nothing similar to using a impact drive to tight the lug nuts at the same ft-lbs for all the cars, like they do in tire shops. I never let anyone, in any shop, use an impact gun on the lugs of my car. I always take my torque wrench and make then use it, like it or not.

In aviation we have the FARM – Federal Aviation Regulations Maintenance. In essence is the FAA regulations for mechanics, our bible. In it it says that EVERY time you perform routing maintenance, repairs, or alterations to an aircraft, the aircraft as to be as good or better than new. I cary over that approach onto my car’s maintenance.

The manufacture engineers/designers put wheels on cars with wheel bores that fit the hub like a glove; then any wheel that goes on my car better do the same. And I use the best I can find, including quality metal centric rings. Manufactures don’t put plastic wheels on they cars, why should I put a plastic ring in there to take the vertical load? Oh yeah I forgot, the hud doesn’t carry any loads (wink).

Be safe people, and please don’t just use “common sense” when it comes to your car maintenance. Rather, rely on scientific, engineerical (if there is such a word), and mathematical facts.

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