Off Center Boring of Automotive Wheels 3

[CapriRacer]

Does anyone know if any vehicle manufacturer still requires their wheels to be bored off center in order to compensate for tire uniformity?

BACKGROUND: Automotive wheels pilot on the center hole of the wheel rather than on the lugs. Some time back some vehicle manufacturers would have their wheels purposely built off center and marked for the low point (typically the valve hole) and have that matched up with the high point mark on the tire. The result was a rounder assembly.

I don't think anyone does that nowadays. I would like to be able to state that in a webpage I am writing on match-mounting tires and wheels for my website: Link

Can anyone confirm?

 

[TugboatEng]

Some things to consider, the stamped wheel center is tapered and relatively flexible so it can still be locating and it takes very little force to deflect it to fit the register closely.

That stamped center gets mounted on a mandrel prior to countersinking the lug holes so this combination will provide very accurate location.

Mass production has the benefit of process refinement that allows for highly precise stamping and minimal post-finishing. It's another example of demand reducing cost.

 

[SwinnyGG]

Some things to consider, the stamped wheel center is tapered and relatively flexible so it can still be locating and it takes very little force to deflect it to fit the register closely.

The stamped wheel center is relatively flexible - in the plane of the hub. Perpendicular to that plane, where the forces would build between an off-center bore and a set of not-off-center lug holes (which is actually what centers everything anyway) the wheel center is very rigid relative to the applied loads.

That stamped center gets mounted on a mandrel prior to countersinking the lug holes so this combination will provide very accurate location.

The lug holes in steel wheel centers aren't countersunk with a cutter - they are punched and then coined to deliver the appropriate belleville-washer-like shape at the lug seat. The lug seat is coined at the complementary angle to provide the correct lug seating angle - no post machining required. The center bore is simply drawn, typically as part of the first pressing (of a usually 3 stage progressive die) and the as-drawn surface is final.

 

[GregLocock]

I'm talking alloys not steels.

Cheers

Greg Locock


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[CapriRacer]

First, thanks to all for the replies. I am especially grateful for the respectful tone everyone has taken. This could have devolved into name calling.

My original question was "Do they still do this?" The response "They never did this." is a subset of "No!" OK I accept that.

I was hoping I could attract someone working for a wheel manufacturer, but it looks like I haven't. So what did I attract?

What's everyone's background - your area of expertise?

 

[Factoter]

Capri, if this were an “Asche Conformity Experiment” then our engineers have either all passed, or failed. As a conformist, I support the “offset-bore” theory: tires, especially stiff walls of bias-ply and light trucks, are inherently non-uniform, acceptable radial runout might be efficiently employed to counter first order harmonics

I have some experience with balancing tires, having worked for a trade school. The standard bubble-levels, for static balance, were still used until this century. And the balance machines, for dynamic balance, are unreliable —- repeatability factor is nearly always zero, in practice. True dynamic balancing must mimic live-load, on the lugs, not the bore, and this is not standard.

Match-mounting with “built-in” radial runout, would be cheap insurance to my mind, for customer comfort and tire wear. Mechanics may be expected to consistently match-mount, but not reliably correct a problem without part replacement, without increased customer cost.

 

[pmbrunelle]

I work for an automotive (mostly) tier 1 supplier, so I am aware of the need for poka-yokes and the trouble that complicated designs/procedures can bring to production.

I was a child in the 90s, so I don't know much about that era, besides what I've been able to pick up doing maintenance/repair/modification on cars of that era, through junkyard scouring, and what my experienced oldtimer colleagues have told me.

I built my own dynamic wheel balancer, and I use it on my personal wheels, and those of friends and family. Often, I check wheel runout with a dial indicator. If I notice runout in a wheel, it's more because of something like pothole damage. I have not noticed a 1/turn frequency type of runout. That said, my sample size is small; nothing like that of a garage that does this work daily.

 

[GregLocock]

The thing from my point of view is that it may have been a proposed/trialled solution but never made it into mainstream production. Or was tried once, papers were written, and then it was cost reduced out (BTDT). And here's a 2010 paper with references to previous work. I no longer have unrestricted access to SAE papers so I'm not chasing them down.

https://watermark.silverchair.com/1_3298682.pdf

Cheers

Greg Locock


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[BrianE22]

Back in the day I worked as an ME at a company that made testing equipment for the tire and wheel market. One tire company asked us to quote on a tire uniformity testing machine. They were interested in the loads to due to runout and the also the loads due to radial stiffness variation (as you turned the tire). They also wanted it done dynamically (spinning at some speed). We declined to quote when we looked at the stiffness and high natural frequency requirements of the machine. Also there is the problem of measuring small forces in the presence of a large radial load.

Although my memory isn't very good I thought they handled the problem with grinding the tire. They may have mentioned offset wheels but I don't remember that. The problem was demonstrated by a colleague of mine who, shortly after buying a new Camaro, decided to lock of the wheels on the freeway at 60 mph. He ended up buying 4 new tires.

 

[CapriRacer]

BrianE22,

There are standard tire uniformity measuring machines - TUG machines (Tire Uniformity Grader). They operate at slow speeds. But tire uniformity behaves differently at high speeds. I'll bet that machine you declined to quote was a high speed machine as those are generally one-offs.

There's been a lot of work to correlate high speed uniformity to low speed uniformity, but with little success - except to say that tires with good low speed uniformity also have good high speed uniformity. The reverse is also true, but the effect is unpredictable (or at least it used to be!)

Also, in the past, it was common for tire manufacturers to grind a bit of tread off tires to improve uniformity - especially for OE tires. The appearance of the grind was always an issue. Tire manufacturing has improved to the point where grinding is no longer needed to meet OEM specs. So if things continue to improve, the high speed problem is going to solve itself.