Bora 8×170 vs 8×6.5 Wheel Spacers: Which Bolt Pattern Fits Your Truck?
Walk into any truck parts store and ask for wheel spacers, and the first question you’ll hear is: what’s your bolt pattern? For Ford Super Duty and older GM heavy-duty owners, that almost always means choosing between 8×170 and 8×6.5 configurations.
These two bolt patterns look similar at a glance — both have eight lugs arranged in a circle — but they’re not interchangeable. Installing the wrong pattern can mean stripped threads, wobbling wheels, or a spacer that simply won’t mount. We wrote this guide to show you exactly which pattern your truck uses, how the measurements differ, and what to check before you order.
What 8×170 and 8×6.5 Actually Measure
The first number in any bolt pattern tells you the lug count. Both 8×170 and 8×6.5 have eight lugs, which is why they’re often confused.
The second number is the bolt circle diameter — the distance across an imaginary circle drawn through the center of all eight studs. 8×170 means 170 millimeters; 8×6.5 means 6.5 inches, which converts to roughly 165.1 mm. That 5 mm difference is enough to make the patterns incompatible.
If you try to force an 8×6.5 spacer onto an 8×170 hub, the studs won’t align. You might get one or two bolts started, but the rest will bind or cross-thread, leaving you with a dangerously loose fit.
Which Ford Trucks Use 8×170
Ford introduced the 8×170 pattern in 1999 for the Super Duty line and has stuck with it ever since. If you drive a 1999 or newer F-250, F-350, or F-450, your truck almost certainly has 8×170 hubs.
This includes both gas and diesel models across every generation: 1999–2004 first-gen, 2005–2007 second-gen, 2008–2010 third-gen, 2011–2016 fourth-gen, 2017–2022 fifth-gen, and the current 2023+ sixth-gen trucks. The pattern stayed consistent even as Ford updated axles, suspension, and powertrain options.
One exception: some aftermarket axle swaps or custom builds might deviate, so always measure if your truck has a modified drivetrain.
Which GM and Dodge Trucks Use 8×6.5
The 8×6.5 pattern has been GM’s heavy-duty standard for decades. Chevrolet Silverado 2500HD and 3500HD trucks from 2001 to present use it, as do GMC Sierra 2500HD and 3500HD models from the same years.
Older GM trucks — 1988–2000 Silverado and Sierra 2500/3500 — also used 8×6.5, making it one of the longest-running bolt patterns in the domestic truck market. Dodge Ram 2500 and 3500 trucks from 1994 to 2011 shared the same 8×6.5 spec before switching to 8×6.7 in 2012.
Because GM kept the pattern unchanged across so many years, there’s a massive aftermarket for 8×6.5 wheels and spacers. Our catalog includes multiple thickness options for this pattern, covering everything from mild poke to aggressive track width increases.
How to Measure Your Own Bolt Pattern
If you’re unsure which pattern your truck has, measuring takes less than five minutes. For an eight-lug pattern, measure from the center of one stud to the center of the stud directly across from it — this is your bolt circle diameter.
If you get 170 mm (or about 6.69 inches), you have 8×170. If you measure 165.1 mm (or 6.5 inches), you have 8×6.5. Use a digital caliper or a quality tape measure; eyeballing it or using a ruler can introduce enough error to make the call unclear.
Another quick check: look up your truck’s year, make, and model in a fitment guide. Most reputable spacer manufacturers list compatible vehicles by VIN range, so you can cross-reference without pulling a wheel.
Why Hub-Centric Fit Matters for Both Patterns
Whether you’re running 8×170 or 8×6.5, the spacer’s center bore must match your truck’s hub diameter. This is called a hub-centric fit, and it’s what keeps the wheel assembly centered on the axle.
Ford Super Duty trucks with 8×170 typically use a 125 mm center bore. GM 2500HD and 3500HD trucks with 8×6.5 use a 124.9 mm bore (functionally 125 mm). If the spacer’s bore is too small, it won’t slide onto the hub; if it’s too large, the wheel can vibrate or wobble even with all lugs torqued.
Some universal spacers claim to fit multiple patterns by using an oversized bore and relying only on lug pressure. That setup transfers all the vehicle’s weight to the studs instead of the hub face, which can accelerate stud wear and create runout over time.
Choosing the Right Pattern for Your Build
Getting your bolt pattern right isn’t optional — it’s the foundation of a safe, vibration-free spacer install. If you drive a 1999+ Ford Super Duty, you need 8×170. If you drive a 2001+ GM 2500HD/3500HD or a 1994–2011 Dodge Ram 2500/3500, you need 8×6.5.
Once you’ve confirmed your pattern, double-check the center bore and stud thread pitch before ordering. A spacer that matches all three specs will bolt on cleanly, center the wheel properly, and handle the torque and load your truck puts through the hubs every day.
Common Questions About 8-Lug Bolt Patterns
No. The 5 mm difference in bolt circle diameter means the studs won’t align properly. Forcing a mismatched spacer can cross-thread studs, crack the spacer, or allow the wheel to loosen while driving.
Not necessarily. Both patterns typically use M14x1.5 or 9/16-inch studs, but the lug nut style depends on your wheel. Check whether your wheels need conical seat, flat seat, or ball seat nuts, then match the spacer’s stud type to that requirement.
No. Bolt pattern is determined by the truck’s hub, not the wheel. Aftermarket wheels must match your existing 8×170 or 8×6.5 pattern unless you swap the entire hub or axle assembly.
Most trucks need at least eight full threads of engagement per stud. If your spacer is thicker than about 1.5 inches and uses a two-piece design with its own studs, you’re usually safe. For thinner single-piece spacers, check that your existing studs protrude far enough through the spacer to reach the lug nut’s minimum thread count.
Yes. Torque all lug nuts to your truck’s spec when you first install the spacers, then re-check after 50–100 miles. This allows the spacer to fully seat against the hub and lets any initial micro-settling happen before long-term use.
Only if your truck somehow has different bolt patterns front and rear, which is almost never the case. Ford Super Duty trucks use 8×170 on both axles; GM 2500HD/3500HD trucks use 8×6.5 on both axles. Mixing patterns on a single axle is impossible because the hubs are identical side to side.