Porsche Cayenne Project: Installing The Stud Conversion Every Project Car Deserves

2022-06-25 08:45:34 By : Forrest Huo

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Every home mechanic should replace their lug bolts with wheel studs.

Anyone unlucky enough to have changed a flat tire on the side of a highway knows the frustration of removing and reinstalling wheel lug bolts. And the fact that most cars use lug bolts at all remains confusing because a much simpler alternative exists. My 1998 Mitsubishi Montero left the factory with wheel studs, which makes sense given the truck-based design that helped souped-up versions win the Dakar Rally so many times. But somehow, the 2006 Porsche Cayenne Turbo that I just picked up for a song did not—despite the fact that the Cayenne famously took on the Transsyberia Rally, not to mention Porsche's long motorsport heritage on the tarmac.

Studs make taking the wheels off track or racecars much easier, while simultaneously helping to significantly reduce the likelihood of stripped threads. For race teams, the marginal gains can mean the difference between a win or loss—for home mechanics, performing a stud conversion can translate to loads of saved time and money. And the benefits become all the more pronounced when adding bigger, heavier wheels or tires to a build, like the Toyo Open Country A/T III tires I plan to use on this Cayenne.

Luckily, a stud conversion is an easy job that shouldn't take much more than half an hour. But in the name of safety, make sure to follow all the instructions to a T.

Many aftermarket parts websites sell stud conversion kits that include the studs themselves and various options for lug nuts. Make sure to find the correct thread pattern for your car's hubs, as well as the correct nuts for your specific wheels. In the case of the Cayenne, Rennline sells studs for various Porsche models using M14x1.5 threads, in various lengths with the ball-seat nuts that will fit Porsche factory wheels. But options for conical seat nuts and more remain easy to find.

The tools required for completing a stud conversion with the new Rennline design include only one somewhat special piece, a 5-millimeter hex head socket. Otherwise, a wire brush, torque wrenches covering both 30 lb-ft and 96 lb-ft, a breaker bar, and the appropriate sockets for your current lug bolts and the new nuts (19mm for both on this Cayenne).

Make sure to buy the correct threadlocking compound—Rennline specifies Loctite 272, which can handle the high heat created by wheel bearings and brakes without melting and becoming a lubricant that could loosen the studs.

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Before lifting your car, break loose your lug bolts enough that they will be easy to remove once the wheels might be able to spin freely. On some cars, the emergency brake will hold all four wheels but most will only hold the rears. This may require finding your unique locking wheel nut key—a nice thing to do away with if you live in an area where your wheels probably won't be stolen on the street.

Lift the car up a few inches on a jack, using jack stands as a safety precaution, and then set about removing the existing lug bolts for the last time.

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Lifting the whole vehicle up at all four corners will make this job much faster, though doing one wheel at a time still won't take too long. Remove the wheels and set aside your old bolts. At this point, I discovered that Porsche designed the Cayenne with little hub-centric tabs that make removing and reinstalling the wheels slightly easier when using lug bolts—I'm confident studs will make the task even easier still.

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Next, use the wire brush to clean out any brake dust or gunk from the hub's threaded holes. You want the surfaces to stay nice and clean to avoid compromising the threadlocker's effectiveness. If you're feeling extra paranoid, some rubbing alcohol could further clean the holes, and an air compressor might be a good idea to blow out any remaining dust.

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Using the correct threadlocking compound is a simple safety matter. Lower-spec products can melt at high heat and actively help to loosen your new wheels studs, which could result in the wheels falling off while driving. Nobody wants that, so make sure to buy the proper spec—in this case, I had to go to three different stores to find one small 10-milliliter container of Permatex 27200, which is an equivalent to Loctite 272 and provides just enough for all 20 of the Cayenne's studs. Amazon also sells the same product.

Apply drips of threadlocker to the short end of the studs, then screw them into the hubs hand-tight.

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Next, follow the instructions to properly torque your studs to the hubs. Rennline specifies 30 lb-ft, which feels pretty light. But remember the studs need to stay in the hubs, while the nuts will get torqued down more. Plus, the 5mm hex head can't handle a ton of force.

For wheel studs without the hex head, tighten two lug nuts against each other onto each wheel stud, then torque down using the torque wrench and a socket.

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Tighten each wheel stud until the torque wrench clicks. Then, go around and double-check that you didn't miss one. The hex heads on the studs definitely make this process faster than the old "bullet-nose" design, because torquing down each stud would require tightening the two nuts on and off repeatedly. But the old bullet-nose studs definitely looked better and made it incrementally easier to slide heavy wheels into place than the square ends of the current studs.

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After installing every wheel stud, slide each wheel on and then snug the new nuts in place with a socket and wrench. Don't put too much muscle into them until you've lowered the car to the ground. Once on the ground, get out the big torque wrench and tighten each nut until it clicks—in the case of the Rennline kit, 96 lb-ft is the correct spec. Again, double-check your work to avoid missing a nut or two.

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I went with 45mm studs, though Rennline also sells 35mm and 60mm options. Other companies go even longer, to allow for the use of wheel spacers and thicker wheels. But I want to avoid wheel spacers because I'm already going to be increasing the torque on the hubs by using about 10% larger-diameter off-roading tires. Still, I could have gone with the longer studs in the name of looks, since these are barely visible. Anyone who knows to give the studs a glance will still see them, though.

Hopefully, this process went smoothly. Again, in the name of safety, skipping steps in this job could prove very dangerous. Rennline also recommends retorquing the lug nuts after around 50 miles of driving, just like anytime you take the wheels off your car. Make sure to do so, especially now that taking the wheels off will be much easier in the future.

Sources: toyotires.com, rennline.com, permatex.com, and amazon.com.

Michael Van Runkle grew up surrounded by Los Angeles car culture, going to small enthusiast meets and enormous industry shows. He learned to drive stick shift in a 1948 Chevy pickup with no first gear and currently dailies his 1998 Mitsubishi Montero while daydreaming about one day finishing up that Porsche 914 project. He's written in various media since graduating from UC Berkeley in 2010 and started at HotCars in February 2018.