What is the relation between a hub centric wheel and the hub?

[evo77]

A debate on another car forum is going on in regards to what defines a hub centric wheel. We know that most if not all vehicles today have the center bores of their wheels machined precisely to the diameter of the hub however its unclear as to whether or not the purpose of a hub centric wheel is merely to center the wheel for balancing purposes or to actually relieve stress from the studs and bear the weight of the vehicle or to do both.

Some feel that the wheels do not bear load and that the studs are the ones taking the grunt of it all.

 

[Fabrico]

"Have you seen the Hunter balance machines? They check the wheel, with or without the tire mounted, as if it were in mounted vehicle position but not held onto the balance machine by the lugs...they use the standard balance cones to keep the wheel centered properly. They can also check runout of the wheel at the same time (although not dead nuts accurate)."

No one said the hole was not centered. With that in mind, does'nt it make sense to affix the wheel to a balance machine with 5 different quick-action cones so the machine can accomodate 1,000 different kinds of wheels and 30 different bolt patterns?

By the way, the big truck wheel balancing machines use studs only to mount the wheel.

 

[CapriRacer]

"...With that in mind, does'nt it make sense to affix the wheel to a balance machine with 5 different quick-action cones so the machine can accomodate 1,000 different kinds of wheels and 30 different bolt patterns?..."

If I understand what you are saying - that 5 cones that would lines up with 5 bolt holes and that would be the only centering on the balance machine - then NO!!

First, there are 3, 4, 6, and 8 lug wheels so you'd need more adaptors.

Second, A mechanism to expand to all the bolt cicles used is really prone to misalignment - aggravating the centering problem. I used one once and it was so difficult to use I tossed it.

Third, if the center hole is centering the wheel, then it only makes sense to use that. I am aware that even with center hole piloting that an eccentric lug on the car can cause distortion, but that doesn't change the fact that the lug nuts are mostly for clamping - not centering.

 

[NickE]

No, no, no, the cones are sized to accomodate the different center hole sizes. They dont fit the lug holes. Then you would need lots of combinations for passenger vehicles.

Fabrico -- I'm guessing that big truck wheels are more standardized with regards to bolt patterns. Correct?

 

[Xwheelguy]

I never said the hole wasn't centered either, Fabrico. Just explaining the process of making a cast aluminum wheel in a mass production situation and why the pilot/hub hole should be and is used for centering passenger car and light truck wheels during balance and runout inspection. The center of the bolt pattern has a tolerance in relation to the hub hole that is normally 0.3mm max. If the lugs were used for balancing, then the center of the wheel COULD be off by that amount and possibly introduce inaccurate balance readings, whereas the pilot is closer to center and preferred to use for centering.

The only time that I've ever seen a wheel located by the lugs for any type of inspection other than torque checking is during runout inspection, checking the center of the lug hole pattern to the center of the wheel bead seats (where the tire seats) and the center of the lug hole pattern to the center of the pilot/hub hole.

Tim Flater
Senior Designer
Enkei America, Inc.

http://www.enkei.com

 

[Fabrico]

"No, no, no, the cones are sized to accommodate the different center hole sizes. They don’t fit the lug holes. Then you would need lots of combinations for passenger vehicles."

yes, yes, yes, that right, center hole used for convenience.

"I'm guessing that big truck wheels are more standardized with regards to bolt patterns. Correct?"

Yes, and they only use half the lug holes to hold the wheel, ie: 5 studs for a 10 lug pattern, 3 for the old big 6 lug pattern.

 

[spectreeng]

Tim,

Even if the hub hole is the true center, and the lugs are off by a small amount - wouldn't you still want to balance it to the lugs, since installation dictates centering about the lugs, not the hub hole? In otherwords, balance it the same way it would be installed and used.

Pilun

 

[CapriRacer]

Pilun,

No. If the hub is centering the rim, then the rim is centered on the hub (sic) and the lugs serve no purpose other than clamping.

In reality, though, even hub centric rims get a bit of distortion from off center lugs, but nevertheless, using the lugs to center for balance is only appropriate if the hub is NOT centering the rim.

 

[Xwheelguy]

Pilun,

I personally wouldn't. Why take a measurement by anything other than the intended center?

Tim Flater
Senior Designer
Enkei America, Inc.

http://www.enkei.com

 

[spectreeng]

Tim,

If the subject was balancing OEM wheels, I'd say balance by the hub hole. In cases where people are concerned about hub-centricity, such as the OP, it is because they have aftermarket wheels with over-bored hub holes - and are questioning the function of hub adapter rings (rightly so since there are plastic and aluminum variety). Upon installing these wheels, even with hub adapter rings, it is the conical lugs acting upon the conical lug seats in the wheel that dictate the location of the wheel, not the hub. To my understanding, the adapter rings only purpose is to _help_ installation by getting the wheel closer to center, making the installation of the lug nuts easier and less likely to scratch the wheel on the sides of the lug nuts. Seems logical to balance these wheels that way, instead of by the hub hole which is for all purposes, floating around the hub.

Pilun

 

[CapriRacer]

Pilun,

I think you'd be surprised about how much centering effect these simple plastic and aluminum hub rings have.

But there are a couple of other issues that you bring up:

The adaptor for using the lugs as centering for balancing is a bit of a mechanical nightmare. It's a fairly complex piece and IMHO adds more variation than it eliminates.

Besides, the only time centering is a real issue is when the bolt circles aren't centered. So even if you use the rim lugs for centering, if the lugs on the vehicle are off center, the effort you put into the rim is for naught.

 

[patprimmer]

This thread is starting to remind me of an old joke. It goes like this.

"Mummy mummy, why am I going in round and round in circles?"

"Shut up kid or I will nail your other foot to the floor."

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[GregLocock]

Probably not a bad idea to put this in context

A wheel and tyre assy weighs around 20 kg. A centreing error of 1 mm will give an imbalance of 20000 g mm

Typically you can detect out of balance of say 10g at 200mm radius, so 2000 g mm (probably not customer complaint level)

So, our centreing system needs to reproduce what is on the car to within 0.1 mm.

That's 4 thou, which is rough as guts as a clearance hole.



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[GregLocock]

I've just found a drawing of a hub centric wheel. The centreing is done by a 6mm wide band, with a dimension of 57mm+0.134+0.060, hole grade E9

I don't know what the mating part's dimensions are.



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.