lug bolts for steel vs. alloy wheels

[JHZR2]

Hello,

My 91 BMW came with steel wheels. I got a set of BBS basketweave OEM wheels a few years back, and have summer tires on them, winter tires on the steelies.

In reading around, it seems that in at least some situations, alloy wheels and steel wheels use different lug nuts.

I know for different vehicles, different lug bolts are used, and is spacers, etc. are used,then longer bolts may be necessary. However, asssume both are OE fit, with identical geometry, thickness, etc.

Is there any reason to have a different lug bolt for an alloy wheel versus a steel one?

Thanks,

JMH

 

[tdi-rick]

In my experience, steel wheels use a taper seat nut, alloy wheels use a flat seat nut with a washer, if they don't have a steel seat pressed into the stud hole with the alloy wheel nut being quite a bit longer thanks to the increased thickness of the wheel centre.

 

[TooManyWheels]

I assume that it is so you can have an intermediate washer to prevent the alloy-wheel lug from grinding into the wheel. Since washers are normally flat, but steel wheel lugs are conical-faced, it means two separate systems.

Also, in my experience, alloy wheels may be designed to center on the shanks of the lug nuts rather than the lugs, therefore the nut assemblies must be designed to at least partially penetrate the thickness of the wheel.

 

[JHZR2]

one question, both posts talk about lig nuts, but I have lug bolts. Is this an issue?

On my 83/85 MB, and my 91 BMW, the bolts for alloy wheels are just one-piece conical seat/ball seat bolts. My saab definitely has 2-piece bolts where the conical seat is a free-rotating item.

Maybe in the 1980s they didnt consider such things as much... I don't know???

The washer, or two-piece design makes sense from the standpoint of not grinding apart a wheel. But that is not the OE fitment on the BMW wheels... looking at the parts for a 91 BMW 318i, there is an alloy lug, and a steel wheel lug, both have the conical seat, both are only one piece, one is black, one is metallic. I have to wonder if the only difference surface treatment to ensure no dissimilar metals... apparently BMW has used the same spec lug bolt for a LONG time. Too bad I can't verify 100% what the real shank length is.

THanks!

JMH

 

[CapriRacer]

JHZR2,

I would not take for "gospel" that alloy wheels have flat lug nut seats. I have seen at least three different arrangements on alloy wheels.

Look at the wheels and tell us what the seats are. It should be fairly obvious. Same thing with the length of the bolts. You ought to be able to determine how much is threaded into the hole - and how much less there would be with the alloy wheels. Putting an eyeball on the situation is going to yield much more info than asking us.

 

[alreadygone]

Originally Posted By: CapriRacer
JHZR2,

I would not take for "gospel" that alloy wheels have flat lug nut seats. I have seen at least three different arrangements on alloy wheels.

Look at the wheels and tell us what the seats are. It should be fairly obvious. Same thing with the length of the bolts. You ought to be able to determine how much is threaded into the hole - and how much less there would be with the alloy wheels. Putting an eyeball on the situation is going to yield much more info than asking us.




AMEN

Bob

 

[eljefino]

I had some aftermarket rims that came with different acorn lug nuts; the taper angle was the same but the aftermarket lugs had a larger diameter-- the OE ones fit all right but didn't interface with the wheel fully.

Having seen OE lugnuts for steel vs aluminum wheels on the same (saturn) car, they were all the same-- likely to help dealer techs from putting the wrong part on etc. Go aftermarket and throw away your preconceptions.

 

[Quattro Pete]

Originally Posted By: JHZR2
In reading around, it seems that in at least some situations, alloy wheels and steel wheels use different lug nuts.

Based on my exeprience with my old A4, both the OEM steel and the OEM alloy rims used the same lug bolts - ball-shaped. But most (if not all) aftermarket rims used conical-shaped lug bolts. I don't think it make a difference as long as you match the shapes (between rims and bolts).