Many years ago, back in high school, my brother and I spent our entire savings ($3,300) to bring a 1968 Corvette with an L79 327 back to life, hoping to make a profit by the end of the summer. One of the tasks was installing all new ignition components, including the cap, rotor, points, and spark plugs. We went to the local automotive parts store, went through the usual process of stating the year, make, model, and engine, and the clerk brought us the parts.

While my brother was at work, I decided to install the new spark plugs and fire it up to see how it ran. Instead of a smoothly purring V8, I heard a crashing and rattling sound and quickly shut it off. When I pulled the spark plugs to investigate, I found that the electrodes on all eight plugs were smashed and bent. I eventually discovered that the part numbers on the new plugs didn’t match those of the old ones, and I was horrified that I might have just destroyed the engine.

It turned out the plugs were meant for a big-block 396 (not our small-block 327) and were much longer, protruding far enough into the cylinder to contact the tops of the pistons. A tough lesson that’s still on my mind 45 years later: always compare the old parts to the new ones!

The happy ending was that there was no piston damage, and everything went well after we removed the broken spark plug pieces and installed the correct ones. We sold the car for $5,500, earning us something like $0.15 per hour!

Jay in Wisconsin

When you change a tire on your new-to-you vehicle for the first time, you may discover the wheel is held on with Lug Studs (wheel bolts) rather than Lug Nuts. Lug Studs were commonly found on models built by American brands (Buick, Packard...) through the 1950s. After that, it was mostly just European brands using Lug Studs. In recent model years, Lug Studs have started to make a comeback, especially on vehicle platforms sold worldwide.

Lug Stud & Lug Nut

Lug Studs may offer advantages such as less cost, less unsprung weight and more consistent torque/rigidity compared to Lug Nuts. On the other hand, Lug Studs can make it harder for a DIYer to change a tire. Lifting a heavy wheel/tire onto studs protruding from the wheel hub is hard enough, but it is then easy to put the Lug Nuts on the hub studs. With Lug Studs you may have to lift the wheel/tire, carefully line up holes in the wheel with holes in the hub and then use your third hand to start screwing in the Lug Studs.

Many wheel hubs have a circular pilot flange in the center that fits into the wheel to help hold it up until you can get some of the studs started. Some car models with Lug Studs include tools such as pilot pins that are temporarily placed in holes in the hub to hold the wheel in place until a couple of the Lug Studs are installed. Check the owners manual, but any tools are usually packed alongside the lug nut wrench, jack or other spare tire gear. An antique car might a have a pilot pin cleverly built into the lug nut wrench or permanently attached to the hub or brake drum.

I just watched a Chrysler video on YouTube showing how to change a tire on a late model Dodge Dart/Chrysler 200. This model must not have come with any original equipment (OE) pilot pins. The video instructions were quite detailed until it was time to lift the wheel up to the hub, line up the holes and insert the Lug Studs. Somehow the wheel just magically appeared in place. RockAuto.com has a Lug Stud Pilot Pin set available under "Wheel" in the "Tools & Universal Parts" tab that provides pairs of pilot pins in the most common thread sizes.

Lug Stud Pilot Pin Set

Since vehicle manufacturers usually stick with a few common wheel stud thread sizes, care must be taken not to mix Lug Studs made for different make/model/year cars. Lexus recently warned shops to not accidentally install the wrong Lug Studs on their customers' cars. A German brand vehicle's wheel bolt may thread in just fine but be too long/short or have the wrong type of seat below the bolt head. A seat (ball, conical...) that is incorrect might prevent the bolt head from mating properly with the surface on the hub. A Lug Stud that is too long might pass through the hub and interfere with some other part. Like Lug Nuts, clean threads on Lug Studs and hub holes allow the lugs to be properly torqued down to the specification in the owners manual.

Various Lug Stud Seats

Some OE Lug Studs have corrosion/swelling problems like lug nuts that are similarly plated. The Lug Stud head (or Lug Nut) is capped with a decorative thin metal covering. Corrosion builds up under and swells the metal covering, making it difficult to get the lug nut wrench on. It is a good idea to replace the Lug Stud (or Lug Nut) before the metal covering becomes a mangled obstacle. RockAuto.com has replacement Lug Studs under "Wheel" for specific vehicles. The replacement parts are often designed to avoid OE problems. For many vehicles lug nut/Lug Stud locks are also available to help prevent wheel theft.

Tom Taylor,
RockAuto.com

To read more of Tom's articles, choose from story titles on the Newsletter Archives page.