Dually Tire Clearance &
Wheel Spacer Gap Calculator
Check the clearance between your dual rear wheels. Prevent sidewall friction, calculate dynamic loaded tire bulge, and eliminate the catastrophic highway "Kiss of Death" blowout risk.
Live Dual Rear Wheel Cross-Section (Top/Rear Axle View)
Proportional diagram showing inner dual wheel, outer dual wheel, spacer, and sidewall gap under load.
SAFE DUAL CLEARANCE (1.85" GAP)
TRA CompliantYour dual tire sidewalls have ample spacing. Under full cargo load or heavy fifth-wheel towing, the gap remains above the safe 1.0-inch threshold, allowing adequate airflow for cooling and stone ejection.
Master Dually Tire Size Clearance Table
Real-world clearances on factory 17x6.5" dually wheels (Ford F-350, Ram 3500, GM 3500) with and without wheel spacers.
| Tire Size | Dimensions (Dia × Width) | Stock Gap (No Spacer) | Stock Status | Recommended Spacer | Heavy Towing Safe? |
|---|---|---|---|---|---|
| 235/80R17 | 31.8" × 9.25" | 1.85" (47 mm) | Stock OEM | None (0") | 100% Safe |
| 245/75R17 | 31.5" × 9.65" | 1.60" (41 mm) | Safe | None (0") | 100% Safe |
| 255/80R17 | 33.1" × 10.04" | 1.10" (28 mm) | Max Stock Fit | None needed (Check PSI) | Safe at 80 PSI |
| 265/70R17 | 31.6" × 10.43" | 0.82" (21 mm) | Borderline | 1/4" to 1/2" Spacer | Light Loads Only |
| 285/70R17 | 32.7" × 11.22" | 0.25" (6 mm) | Rub Danger | 1.50" - 2.00" Steel | Unsafe Stock |
| 295/70R17 | 33.3" × 11.61" | 0.05" (1 mm) | Kiss of Death | 2.00" Steel Adapter | WILL RUB |
| 35×12.50R17 | 35.0" × 12.50" | -0.75" (Overlap!) | IMPOSSIBLE STOCK | 2.00" - 2.25" Steel | Blowout Hazard |
| 37×12.50R17 | 37.0" × 12.50" | -0.75" (Overlap!) | IMPOSSIBLE STOCK | 2.00" - 2.50" Steel | Blowout Hazard |
The "Kiss of Death" Explained
On dual rear wheel (DRW) pickup trucks, the sidewalls of the inner and outer tires must never touch while rotating. When a truck is loaded with heavy fifth-wheel tongue weight, the lower portion of each radial tire bulges outwards.
If the gap between the wheels is insufficient, the tires will contact each other under load. At highway speeds (65–75 MPH), the two rubber sidewalls experience violent friction, generating localized temperatures exceeding 200°F (93°C).
Steel vs. Aluminum Dually Spacers
While cheap billet aluminum spacers are common in the half-ton car scene, **aluminum wheel spacers should NEVER be used on heavy-duty 1-ton dually trucks**.
- ✓Forged American Steel (BORA / Fred Goeske): High-grade steel has identical expansion rates and shear strength to your truck's axle hub and brake rotor. It handles 14,000+ lb fifth-wheel pin weights without micro-flexing.
- ✗Billet Aluminum Hazard: Aluminum is softer than steel. Under extreme commercial torque and heavy braking, aluminum spacers can deform, causing lug nuts to back off and wheel studs to shear completely off.
- ✓Hub-Centric & Wheel-Centric: Ensure your spacer has a precision machined hub pilot ring so the vehicle's weight rides on the axle, not the lug studs.
Frequently Asked Questions: Dually Wheel Clearance & Spacers
What is the 'Kiss of Death' on a dually truck?▼
The 'Kiss of Death' occurs when the sidewalls of dual rear tires touch each other under load, cornering, or lower air pressure. The constant high-speed rubbing between the two touching rubber sidewalls generates extreme friction and heat (exceeding 200°F / 93°C). Within a few miles on the highway, the rubber overheats, the internal tire layers peel apart, and both tires suffer a sudden blowout, often ripping apart the fiberglass fender and causing serious rollover risks.
What is the minimum safe tire gap between dual rear wheels?▼
The Commercial Tire & Rim Association (TRA) recommends a minimum clearance of 1.50 inches (38 mm) between dual tire sidewalls when the truck is empty, and at least 0.75 to 1.0 inch (19 to 25 mm) under heavy towing loads. A minimum gap of 0.75 inches is also critical to prevent rocks from getting stuck between the tires and to keep cooling airflow circulating.
What is the biggest tire you can fit on a stock dually without spacers?▼
On modern Ford F-350, Ram 3500, and GM 3500 DRW pickups with stock 17-inch wheels, the largest recommended tire size without wheel spacers is 255/80R17 (roughly 33.1" tall by 10.0" wide). This 'tall and skinny' tire provides a taller 33-inch stance while leaving approximately 0.90 to 1.15 inches of safe clearance between the duals. Moving up to 285/70R17 or 35x12.50R17 requires wheel spacers.
Should I use steel or aluminum wheel spacers on a dually?▼
You should ALWAYS use forged steel, hub-centric and wheel-centric spacers (such as BORA Steel Spacers) on heavy-duty dually trucks (1-ton and larger). Aluminum spacers can expand and compress under the massive clamping force and 14,000+ lb fifth-wheel pin weights, leading to loose lug nuts, snapped wheel studs, or wheel detachment. Additionally, hub-centric rings are mandatory to transfer the vehicle's massive weight directly onto the axle hub rather than the lug studs.
Do I need to trim my factory wheel studs for dually spacers?▼
If you install 1.5-inch spacers, the factory wheel studs (which are typically 1.65 to 1.75 inches long) may protrude slightly past the mounting face of the spacer. If your outer wheel doesn't have deep pockets between the lug holes, the studs will have to be trimmed. This is why 2.0-inch steel spacers are the most popular choice: they are thick enough that factory studs do not require trimming, making the installation 100% reversible.