Introduction

Installing wheel spacers on a Nissan 370Z is a popular modification that can dramatically improve the vehicle’s stance and, in some cases, enhance cornering stability. By pushing the wheels outward, spacers widen the track, giving the car a more aggressive look and reducing body roll during aggressive driving. However, the choice between 15mm and 20mm spacers involves more than just personal preference—it affects fitment, suspension geometry, and safety. This expanded guide covers everything from selecting the correct spacer type to performing a precise, safe installation. Whether you are a seasoned enthusiast or a first-time installer, following these steps will help you achieve professional results while avoiding common pitfalls.

Understanding Wheel Spacers: 15mm vs 20mm

What Wheel Spacers Do

Wheel spacers are precision-machined plates that mount between the vehicle’s hub and the wheel. They effectively move the wheel outward, increasing track width. On the 370Z, this can improve stability by widening the stance, but it also places additional stress on wheel bearings, suspension components, and lug studs if not chosen correctly. The most critical factor is ensuring the spacer is hub-centric—meaning it centers the wheel on the hub rather than relying on the lug nuts alone. Hub-centric spacers reduce vibration and prevent loose wheels over time.

Differences Between 15mm and 20mm Spacers

The primary difference between 15mm and 20mm spacers is the offset change they create. On a 370Z, stock offsets typically sit around +30mm for the front and +33mm for the rear. Adding a 15mm spacer effectively reduces offset to approximately +15mm front and +18mm rear, while a 20mm spacer drops those numbers to +10mm and +13mm respectively. This can bring the wheels nearly flush with the fenders—or even cause rubbing if the tire width is aggressive. In general, 15mm spacers are a safe choice for cars with factory suspension and stock wheels, while 20mm spacers often require aftermarket wheels or rolled fenders to clear the outer lip. Also, 20mm spacers often come as bolt-on units with integrated studs, whereas 15mm spacers are typically slip-on that use extended lug nuts. Understanding this mechanical difference is essential for a safe install.

Hub-Centric vs Slip-On: Which One to Choose

Hub-centric spacers include a raised center ring that precisely fits into the wheel’s center bore. This eliminates vibration and ensures the wheel is perfectly centered. Slip-on spacers (also called universal spacers) are flat plates that rely entirely on the lug nuts to center the wheel; they are more prone to imbalance and are generally not recommended for daily driving. For both 15mm and 20mm applications on the 370Z, hub-centric spacers are strongly advised. Many brands offer bolt-on hub-centric spacers for 20mm and above, while 15mm spacers require extended thread lug nuts (since the spacer is thin enough that the factory studs protrude through it). Always verify that the spacer’s center bore matches the 370Z’s hub diameter (66.1mm) to avoid vibration.

Choosing the Right Size for Your 370Z

Deciding between 15mm and 20mm depends on your wheel type, tire size, and suspension setup. With stock 18×8-inch front and 18×9-inch rear wheels (or 19-inch variants), 15mm spacers typically clear the fenders without modification. A 20mm spacer will often poke the tire slightly beyond the fender edge, especially in the rear. If you are lowered on coilovers, you may need to roll the fender lips or choose a smaller spacer to avoid rubbing. Measure your current clearance: with the wheel off, place a straightedge across the rotor face and measure to the inside of the fender. That gap minus 5mm of safety margin gives you the maximum spacer thickness you can safely run with your current setup. For most 370Z owners, 15mm front and 15mm rear provides a noticeable improvement without fitment headaches.

Tools and Materials Needed

Having the right tools ensures a smooth installation and prevents damaged hardware. Gather the following:

  • 15mm or 20mm hub-centric wheel spacers (with compatible extended lug nuts if required)
  • Socket wrench with appropriate sockets (typically 19mm or 21mm for lug nuts)
  • Torque wrench capable of 75–80 ft-lbs (and up to 100 ft-lbs for some aftermarket lug nuts)
  • Floor jack and two jack stands
  • Wheel chocks
  • Brake cleaner and clean shop rags
  • Wire brush (optional, for cleaning rust from hub surfaces)
  • Anti-seize compound (avoid on aluminum-to-steel mating surfaces; OK for threads)
  • Breaker bar (optional, for stubborn lug nuts)
  • Torque-to-yield specs for your specific spacer brand (some require higher torque)

Preparation for Installation

Proper preparation reduces risk and saves time. Park your 370Z on a level, concrete surface. Engage the parking brake firmly and place wheel chocks behind the rear wheels. If working on the front, chock both rear wheels; if working on the rear, chock both front wheels. Allow the car to cool completely if it has been driven—hot brakes and rotors can be dangerous. Gather all tools within arm’s reach before lifting the vehicle. Wear safety glasses and gloves. Finally, confirm that your spacers are the correct bolt pattern (5×114.3mm) and center bore (66.1mm) for the 370Z. Mismatched spacers can loosen catastrophically.

Step-by-Step Installation Guide

Removing the Wheels

1. Loosen the lug nuts: Using a socket wrench or breaker bar, break the lug nuts loose while the wheel is still on the ground. Turn them counterclockwise about half a turn—do not remove them completely yet. 2. Jack up the vehicle: Position the floor jack under the factory jack point (a reinforced area behind the front wheel or in front of the rear wheel). Lift until the tire is about an inch off the ground. Place a jack stand under the designated lift point and lower the car onto it. Repeat for the opposite side if doing both axles. 3. Remove the wheels: With the car secure, finish unscrewing the lug nuts and pull the wheel straight off the hub. Set the wheel aside in a clean area, face down to protect the face.

Cleaning and Inspecting the Hub

Inspect the hub flange and the rotor surface. Remove any rust, debris, or old anti-seize using a wire brush and brake cleaner. A clean metal-to-metal contact is essential for the spacer to sit flush. Pay special attention to the center pilot ring area—any dirt there will cause the spacer to mount off-center. Wipe the entire hub surface with a clean rag soaked in brake cleaner and let it dry. Also examine the wheel’s mounting surface for any damage or unevenness.

Installing the Spacers

The procedure differs slightly for 15mm slip-on spacers vs 20mm bolt-on spacers.

For 15mm slip-on spacers: Align the spacer’s center hole with the hub and slide it on. The spacer will likely be held by the factory studs poking through its lug holes. Ensure the spacer sits flat and flush against the hub face. There should be no gap. If using extended thread lug nuts, hand-tighten them onto the factory studs to secure the spacer temporarily—but do not torque yet as the wheel will be installed over them.

For 20mm bolt-on spacers: These spacers come with their own integrated studs. Place the spacer onto the hub, aligning its center bore with the hub pilot. The spacer should press on snugly. Use the provided bolts to attach the spacer to the hub. Hand-tighten these bolts in a star pattern, then torque them to the manufacturer’s specification (commonly 70–80 ft-lbs, but verify). Now the spacer is permanently attached to the hub; the wheel will mount onto its studs.

Regardless of type, never use an impact wrench to install spacers—it can over-torque the hardware and distort the spacer material. Always hand-tighten and use a torque wrench.

Reinstalling the Wheels

With the spacer in place, pick up the wheel and align its lug holes with the spacer’s studs (for 15mm) or the spacer’s own studs (for 20mm bolt-on). Slide the wheel onto the spacer. If the wheel sticks, do not hammer it—check that the center bore aligns. Once seated, hand-thread the lug nuts (or the wheel nuts for 20mm bolt-on spacers) in a star pattern. Tighten them snugly with the socket wrench, but do not fully torque yet—the wheel needs to be on the ground for final torque.

Torque Specifications

Proper torque is critical to prevent wheel separation. For the Nissan 370Z with stock lug nuts, the factory torque is 75–80 ft-lbs. However, if you are using extended thread lug nuts from aftermarket spacers, follow the spacer manufacturer’s torque value—some require 85–90 ft-lbs. For 20mm bolt-on spacers, the spacer-to-hub bolts must also be torqued (typically 70–80 ft-lbs, but check). Use a calibrated torque wrench and tighten in a star pattern to ensure even clamping force. Never use anti-seize on the lug nut threads unless the manufacturer explicitly allows it—anti-seize can cause over-torquing because it reduces friction, leading to stretched studs or broken nuts.

For reference, reputable spacer manufacturers like Motorsport Tech provide specific torque values. Always refer to your product’s instructions.

Lowering the Vehicle

Double-check that all lug nuts are snug (not fully torqued). Remove the jack stands one side at a time. Lower the car gently using the floor jack until all four tires are on the ground and the suspension is loaded. Now, using a torque wrench, tighten each lug nut to the specified torque in a star pattern. This ensures the wheel and spacer are properly seated against the hub. If you have 20mm bolt-on spacers, also re-check the spacer-to-hub bolts after the vehicle is lowered—they may have settled slightly.

Post-Installation Checks and Test Drive

After installation, perform a thorough inspection before driving. 1. Visual check: Look at the gap between the tire and fender on both sides—ensure there is at least 5mm of clearance at full compression (simulate by pushing down on the fender). 2. Lug nut check: Verify all lug nuts are present and properly torqued. 3. Spacer check: For bolt-on spacers, check that the spacer is flush against the hub and there are no gaps. 4. Re-check after 25–50 miles: Drive gently for the first few miles, then re-torque all lug nuts. The clamping force can cause slight settling. It is normal to need a re-torque once after initial installation. After that, check at every tire rotation. 5. Test drive: Drive at low speed, then moderate speed, and listen for any rubbing noises. If you hear rubbing on turns or over bumps, you may need to roll the fenders or choose thinner spacers. Also feel for vibration in the steering wheel—if vibration occurs, the spacer may not be hub-centric, or the wheel may be unbalanced. Re-check centering and balance as needed.

Common Issues and Troubleshooting

Vibration after installation: This is typically due to a non-hub-centric spacer or debris trapped between the spacer and hub. Remove the spacer, clean both surfaces, and ensure the center bore matches exactly. If the spacer’s center bore is too large, use a hub-centric ring adapter (though it’s better to buy the correct spacer). Rubbing against fender: With 20mm spacers, especially in the rear, you may experience rubbing when the suspension compresses. Solutions include rolling the inner fender lip, trimming the fender, or switching to a 15mm spacer. Lug nuts loosening: If lug nuts keep loosening, the spacer may be slipping or the threads may be stripped. Replace damaged studs and nuts immediately. Never drive with loose lug nuts. Rust/corrosion: Apply a thin coat of anti-seize to the hub face (not the threads) to ease future removal. For more detailed troubleshooting, consult the Nissan 370Z Tech Forum at the370z.com where the community has extensive experience with spacer fitments.

Final Thoughts

Installing 15mm or 20mm wheel spacers on your Nissan 370Z is a rewarding upgrade that transforms the car’s visual appeal and sharpens its handling. The key to a safe installation lies in selecting hub-centric spacers, using a torque wrench at every critical step, and verifying clearance after the car is on the ground. While 15mm spacers offer a hassle-free, near-stock fitment, 20mm spacers deliver a more aggressive flush look that may require additional fender work. Whichever size you choose, this guide provides the detailed steps needed to do the job right the first time. Remember, wheel installation affects safety—if at any point you doubt your work, consult a professional mechanic. With proper care, your 370Z will reward you with a stance that turns heads and a drive that feels planted around every corner.