altering wheel bolts
 

Hey guys, I've bought a set of aftermarket wheels for my car but they have both a slightly thicker centre boss, and the bolt holes are flat rather than tapered. I feel that chucking my factory wheel bolts in a lathe and removing the taper will allow them to bolt flush against the boss, and extend through it to engage the hub to a better depth

any problems with removing the taper from the factory bolts? likely to weaken them at all? thanks in advance

Why not just buy wheel studs? They press right in by hand tools.

the stock bolts are actually 2 pieces, so removing the taper isn't possible

The wheels you just bought use a totally different mounting system. Instead of the conical seat that the OEM wheels use, they have a flat seat that requires a stud, a different type of lug nut, and a flat washer. I'd contact the place you bought the wheels from for guidance.

Any time you remove metal from a fastener, you're weakening it. Whether or not it's a significant weakening, can be determined either by hairy calculations or even hairier destructive testing - - intentional or otherwise.

As mentioned above, the stock bolts are two-piece, though both the threaded portion and the taper are all on one part. but it's the part that you don't want to weaken.

Always use proper fasteners for safety-critical apps, of which wheels and brakes are the two most crucial.

Areed with the guys above. I can see two problems right off the bat..if the center boss is thicker then your stock bolts might be shorter than you would need in order to be safe, and removing the taper on rhe stock lug bolts is going to be very labor intensive and weaken the crap out of them. For safety and ease of installation just buy new studs and press them in..they are cheap as hell and you can make sure the studs are long enough to be safe.

thanks for the replies guys, I've already bought a set of studs once, and they ended up being too short. As I have access to a lathe and could do the modification for free, I was hoping I could save some money. But I'll look into longer studs

couple of questions though, how exactly do they "press in"? as far as I can see, the wheel hub is threaded - no stud is going to press in there like they do on an normal hub?

also, my bolts are probably fused together with rust, but I really can't see how they're two piece? (without one here in front of me to look at) it looked to all the world like a single lump of steel

The hex part is actually separate from the threads and taper, it's splined and pressed on. I did it so long ago I forget, but I'm pretty sure it's 1/2" knurl studs that will press right in, or you can drill the holes out carefully and use a bigger stud if you need to for your wheels. I pull them through the hub with an extra lug nut, a few greased washers, and an impact gun.

I don't know if this was clear enough, so I added an illustration. You probably have the "Mag Type" Hex Nut, Flat Washer, and Seat. This type of system was developed back in the early days of magnesium (the real "Mag" wheels) because the material was prone to creep with conical seats and result in loose joints. The flat washer distributed the load better and prevented the material creep.

The smooth cylindrical part slides into the lug holes and helps center the wheel, since many of the aftermarket Mag wheels weren't hubcentric.

If you just use a bolt or a stud with a basic hex nut, you will probably have issues with wheel centering, if not wheel retention.

Those type of wheels are commonly used on Toyotas..Matrix, Corolla etc. If you use the Toyota style lugnuts I'm sure they can be used..they might even be the same thread pitch as Mazda..I'm not sure though.