MrMook
Reader
6/26/23 2:02 p.m.
I have a 2021 Ford Transit Connect van, and I'm searching for a second set of wheels.
I thought it would be easy, since the 5x108 specs are an easy swap with most Focus models, and a slew of Volvo cars. But most of those potential donors use M12 lugs/bolts, and the lug holes are ever-so-slightly smaller than the holes for the M14 studs on my 2021 TC.
My biggest question (because I'm an overthinker) is: from an engineering and materials standpoint, is there any reason a narrower lug hole (and potentially narrower lug seat) would cause any adverse stress issues if used with a wider stud? In comparing an M12 steel wheel (Volvo) and my M14 spare (Ford, steel), the OEM lug holes are about 1-1.5mm wider. Seems insignificant, but then again, Ford issued my wheels with wider holes, so there must be something worth considering.
Thoughts?
If the stud fits through the hole and the taper on the lug nut matches and seats fully against that of the wheel, then you're fine. The clearance between fastener and hole is just there to aid assembly and ensure the fastener fits through the hole when considering any adverse tolerance stack ups.
FWIW, I did similar overthinking before getting Subaru wheels (M12 studs) to put on my Golf (M14 lug bolts). I agree with bumpsteer: M12 wheels are almost certainly going to be perfectly fine, but you do still have to check that your specific M14 lug nuts seat properly with your specific M12 wheels.
If you really want to measure something, compare the diameter of the flat on the end of the lug nuts to the holes in the wheels. It's probably bad to use this 0.610 lugnut if the wheels have conical seats with a 0.590 ID (random poached image).
I'll make a comparison to wheel spacers. Neurotic overthinking can come up with all the ways it might possibly be bad to use flat wheel spacers if the car is hubcentric. BTDT. Reality says that flat spacers are perfectly fine b/c mass production wheels are always effectively lugcentric once torqued due to conical lug nuts, design clearances, tolerance stackup, etc. (However I will say that temporary "wheel hanger" studs make life suck less if you have flat spacers + lug bolts.)
Volvos with 5 on 4.25 are largely 14mm.
A long time ago, I had an RX-7 with a stripped thread hole in one of the rear axles. Stock lug bolts are 12x1.5. Being a weenie, I tapped it to 1/2-20 as an intermediate size, then tapped it to 14x1.5, and just had to remember which hole used the 14mm. It was a long time ago, but I recall that I never had an issue with wheels, but I did have to drill out the brake rotor a little bit.
I am sure someone, somewhere, will have an apoplectic fit over this, but I also used to use ball seat lug bolts on taper seat wheels all the time, no problem. I wouldn't go the other way, however.
