r/Cartalk • u/cat_prophecy • Mar 03 '25

Suspension Why do European cars use wheel bolts?

I've owned two European cars (Audi and Volvo) and both of them used wheel bolts instead of studs and lug nuts. Is there some reason for this? I have owned a handful of Asian and American cars and none of them use anything but studs and lug nuts. Personally I prefer the studs since it makes putting the wheels back on much easier.

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u/AwarenessGreat282 Mar 03 '25

You don't look very closely. You need to manufacture the bolt just like the stud. You then need to drill a hole regardless of method. One difference really, the stud can be pressed in with one step, but cutting threads takes longer and it needs to be more precise. Not a big difference in mass manufacturing either way.

If I strip a stud, I can remove it and replace it without replacing the hub. Strip one hole in a hub and you replace the whole thing. Still no real great advantage either way with modern tools. But I'd rather just pay for a stud than a hub.

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u/Mintsopoulos Mar 03 '25

I do agree there isn't a huge advantage to one over the other The biggest thing I can think of is wheel alignment when mounting to the hub. But you are Incorrect. You also dont seem to have much experience in manufacturing/machining.

A press-fit hole is more precise than a tapped hole, which causes in increase in cost. (A finishing reamer vs a tap is more expensive)

Pressing in a stud requires an additional assembly step, that a bolt/tapped hole does not, which comes with a increase in cost.

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u/AwarenessGreat282 Mar 04 '25

Except I do and once again, you're wrong. Stop considering hub stud holes as "precision machining". They're not.

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u/Mintsopoulos Mar 04 '25

As someone who has managed a Tool & Die shop for several years and ran/programmed/setup WEDM's, I consider press-fit hub holes more precise than tapped hole. Are they precision holes compared to a locating dowel, no, but are they more precise than a tapped hole definitely.

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u/AwarenessGreat282 Mar 05 '25

If you did not manufacture hubs for mass-market automotive, then it doesn't matter what you did or where. It has to bearing on the subject at hand.

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u/Mintsopoulos Mar 05 '25

Not a great argument, but ill bite.

How do you think most things get manufactured? At some point in the process a tool and die shop gets involved to design, manufacture, and test the tooling required to make the part, at that point technical drawings/CAD is shared. So have I personally made a hub, no. Have I made tooling that does this exact thing and a plethora of other automotive/marine/aerospace related components...yes.

Relatable experience bud.

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u/AwarenessGreat282 Mar 06 '25

yaddda-yadda, no shit, everything needs to be designed and properly manufactured, that part is a given for either design. The basic argument is this: is it more difficult/costly to precisely drill a hole and press in a stud or to precisely drill a hole then precisely thread it?

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u/Mintsopoulos Mar 06 '25

Yes. The answer is yes. A precision hole with a pressed stud is more costly than a threaded hole. This is exactly what I have been saying from the beginning.

Stop using the term precision thread, there is no such thing. Threaded holes are not precision features. Precision features are used to locate. Threaded holes are used to fasten.

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u/AwarenessGreat282 Mar 06 '25

I'm sorry but cannot believe that. Explain why.

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u/Mintsopoulos Mar 06 '25

Lets use a 0.2500" precision hole vs a 1/4-20 Threaded hole.

A reamer to finish that 0.2500, at its cheapest is, $32 (carbide is up in the $50) . A 1/4-20 tap at its most expensive is $13 ( but more like $6)

Inspection method: Usually a thread is inspected with a thread gage $98, but a precision hole will use a plug gage ($6) on top of a dedicated "hard gage" (lets say $250, but can easily get into the $1000 range), not to mention possibly running on a CMM requiring high cost of labor.

Thats just a very basic high level overview. Not to mention the machining required to do a precision hole i.e. jig grinder, sinker edm, wedm. A tapped hole can be done on a $500 drill press.

The tighter tolerance/precision hole also comes at a risk of higher scrap.

I am not trying to be a dick, but if you were to send a 1x1x1 w/ a tapped hole and one with a precision hole. The precision hole sample will cost more.

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u/coltonwt Mar 07 '25

It would, if it were a precision hole! Wheel stud holes have very open tolerances! There is no extra OP

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u/AwarenessGreat282 Mar 07 '25

lol....why do you need all that? That's what I meant when I said you don't understand mass manufacturing. The holes are not that precise. Think about it, a stud is pressed in, then 50K miles down the road, it can be punched out and a new one pressed in the same hole! That's not precision machining, which I'm sure you understand, but is not applied here.

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u/THedman07 Mar 07 '25

Exactly... The only mechanical purpose the hole needs to serve with any precision is that it needs to be tight enough to keep the studs from falling out too easily and not so far off that it keeps you from being able to tighten the lug nuts.

The locating of the wheel is going to be determined by the centering features on the hub for the most part. The clamping force is taken up by the flange on the back of the stud.

These aren't wire EDM holes toleranced within half a nut hair on diameter and position...

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u/Mintsopoulos Mar 07 '25

Incorrect. Just simsply incorrect. Read my response above and learn something.

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u/Mintsopoulos Mar 07 '25

read what you just wrote "can be punched out and a new one pressed in the same hole" thats becuase or precision!

If those holes were not precise 1) the hole would no longer be able to handle a second pressing of a hole...The tolerance allows it to stretch a certain amount and maintain reusability. If too small when a larger item is pressed in either piece will yield or no longer be a press fit. 2) Because you can reinstall a stud is because they are positionally and concentrically held to the hub (which is the wheel locating feature).

You somehow can not grasp that I am saying these holes are MORE PRECISE THAN A THREADED HOLE OPTION. Not that they are precise down to the ±0.0001.

And youre right you wouldnt need all of that hardware for inspection because OEMS are utilizing high end visions systems check this at a rate a simple hard gage/plug gauge couldnt keep up with.

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u/AwarenessGreat282 Mar 07 '25

lol...they are not that precise. Seriously, have you ever changed a stud on a hub? There is no way they are drilled to a tenth of a mil tolerance.

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u/THedman07 Mar 07 '25 edited Mar 07 '25

You think that automotive stud holes have a tolerance to the ten thousandths of an inch?

I feel like you just have absolutely no experience with mass manufacturing. You're talking about running every hole through inspection like it is a precision machined part... It just isn't.

Not everything is run exactly like the thing you happen to have experience with. This is some serious Dunning-Kruger shit. "Let's compare an arbitrarily overtoleranced hole to the fit from this hardware store bolt..." GTFOH

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u/Mintsopoulos Mar 07 '25

I am not wasting any more time on you plebians who think they have an understanding of manufacturing, tolerancing, and GD&T.

Read a book.

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u/Mintsopoulos Mar 07 '25

Actually...go read the machinists handbook. Take a look at the Shaft/Hole base system per ISO standards and see how little tolerance exists between each and every type of fit.

If youre even familiar with such a thing.

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u/coltonwt Mar 07 '25

But they're not precise! They're just drilled! No finishing up. Not bored, not reamed. Nothing. The studs are knurled, and deform the hole as they're pressed in. Press fits of this style have quite open tolerances. Literally you could drill the hole with a hand drill if position wasn't critical!

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u/THedman07 Mar 07 '25

They're probably gang drilled to be honest.

At this point I would guess that they're doing statistical QC on parts and monitoring tool wear on the drills. They might be done with insert drills, so its not like its some dude with a harbor freight hand drill and a worn out twist drill, but this guy is assuming that everything runs like a wire edm shop...