How Do I Avoid Snapping Studs On My Subaru?

Nick is an engineer from Minneapolis-St. Paul. He came to me with a simple question this week. His buddy just bought a new Subaru. They’re famous for breaking wheel studs—an incredibly frustrating problem. Eager to avoid time-consuming repairs down the line, Nick asked what he could do to prevent the issue.

Around these parts, we love posing questions for Autopian Asks. When Nick reached out to me with his question, though, I realized we’ve never done Autopian Answers before. I figured I’d answer his query as best I could, and let you all chime in with your own knowledge, too.

So, what is to be done? Let’s explore how to best avoid wheel stud failure in a modern Subaru.

@rainbowdefault.bsky.social a buddy just bought a new Subaru and I’d like him to be able to service the wheels without the studs snapping. Is there anything you can do to prevent it? A certain grease or torquing to the right level?

— Nick S (@nottooserious.bsky.social) December 12, 2024 at 2:44 PM

Make It (Not) Snappy

Let’s start with a basic definition of the issue. The wheel stud is the threaded steel part on which you tighten the wheel nuts. On most cars, these are lifetime items that never need replacing. However, Subaru has gained a reputation in recent years for weak wheel studs that snap relatively easily. Our own Matt Hardigree had this experience with his not-too-old Forester and he wasn’t alone.

Head over to the forums and you’ll find all kinds of complaints. “Yeah, those stock Subaru studs are about as strong as pretzel sticks,” says one owner. There are plenty of others out there telling similar stories.

They can be a pain to replace, too. You need to remove the wheel, brake caliper, and rotor to get at the studs, then you need to deliver many good whacks from a sledgehammer to get the damaged part out. This can be easy or excruciating depending on how seized they are. Finally, you need to wiggle the new stud into place and use a stud installing tool (or stack of washers) to press fit it into the hub. This is easier said then done at times—I’ve had to do this job on a Honda Civic, and it wasn’t much fun..

Nick says his friend’s car is brand new, so you would normally expect the studs to last a good couple decades. However, Subaru’s wheel studs have a particularly poor reputation. Is there something especially bad about them?

As it turns out, the experts over at Art’s Automotive have looked into the problem. The Bay Area shop specializes in Japanese automobiles, and found a high number of Subaru studs were failing in the field.

It’s far from the worst job, but it can really put a crimp in your weekend if you’re regularly driving in the Snow Belt.

Their article covers what makes Subaru wheel studs different, and proposes a theory as to their common failure. Unlike other Japanese brands, Subaru’s wheel nuts use an M12 x 1.25 mm thread, rather than the more common M12 x 1.5 mm thread. The second number—1.25 mm—refers to the thread pitch. Basically, the threads are more closely packed on the Subaru studs. If you measure from the peak of one thread to the next, you’d get 1.25 mm (0.049 inch) on a Subaru wheel stud. Nissan uses the same pitch too, but for some reason, weak studs appear to be more of a Subaru issue.

All in all, for two studs of the same nominal diameter, the one with finer-pitch threads is usually stronger in terms of tensile strength. That’s because a larger thread pitch also creates a deeper cut, which reduces the amount of metal able to take load. You’d thus expect Subaru’s fine-pitch studs to be stronger, not weaker, and more resistant to overeager mechanics with impact guns, too. And yet!

The thing is, finer-pitch threads do come with drawbacks, too, as noted by Art’s Automotive. They’re more likely to suffer galling, where small bits of metal shear off the threads and create little balls that can jam everything up. They’re also easier to damage, easier to cross-thread, and more likely to seize due to excess friction during high-speed tightening. There’s the smoking gun—while the finer-pitch threads make for technically-stronger studs, they also make for studs that are more likely to fail when using impact guns or during careless assembly. Of course, it could also be that Subaru just uses cheap lug studs made out of crappy materials, but that’s harder to investigate without a university-spec laboratory on hand.

The Solution

So what is to be done? Well, Art’s Automotive has a simple solution. They suggest using anti-seize or a touch of grease on lug nuts, in order to reduce friction. This should prevent seizing or galling, which is often a precursor to snapping a lug nut. Lug nuts are supposed to be installed dry, but this should be perfectly safe as long as you keep torque to the right spec. Technically, lubricant on the threads increases the total tensile load felt by the stud when tightening to a given torque, but as long as you’re sticking to the proper torque spec, you’re unlikely to hit any issues. Avoiding mechanics or tire shops that don’t use their impact tools safely is key, too.

John Cadogan explains how to safely choose the right torque spec when using anti-seize on your lug nuts. 

Installing the lug nuts more slowly is also a good habit to get into. Our grandmammies and grandpappies couldn’t be doing with all this electric nonsense. They used good old-fashioned tire irons and took their time doing so.

Beyond that, you can always go the upgrade path. ARP makes studs that are well-regarded for their extra strength. I wouldn’t bother pre-emptively ripping out all the studs and changing them, though. Don’t make work for yourself! If you’re doing a brake or wheel bearing service down the line though, that might be a good time to change over.

In any case, if you do snap a stud, you won’t be the first Subaru owner to do so. You’ll get knowing nods from others at the parts store when you go in to pick up replacements. I hope this puts you at ease and helps your buddy have many carefree years of motoring in their Subaru. Not everyone does, of course, but we should always hope for the best!

Images: Subaru, via Youtube Screenshot