1989 GMC Sierra 1500 I (GMT400) Regular cab LWB Wideside Dimensions, Size & Specs

The 1989 GMC Sierra 1500 I (GMT400) Regular Cab in the Long Wheelbase Wideside configuration features a longer bed to optimize cargo hauling capacity, ideal for work and utility purposes. The 'Wideside' designation means the pickup's rear fenders are extended to create a wider cargo bed, allowing for easier loading and accommodating larger or wider items than standard beds. This setup appeals to users needing more cargo space without upgrading to heavier-duty models. Combined with the regular cab's compact passenger compartment, it balances driver space with a large bed. This layout is particularly favored by tradespeople, outdoor enthusiasts, and those requiring a versatile pickup with strong payload capacity.

Given its exterior dimensions—length of 5547 mm (218.3 inches), width of 1951 mm (76.8 inches) excluding mirrors, and height of 1788 mm (70.4 inches)—the 1989 GMC Sierra 1500 I Regular Cab LWB Wideside can fit in most standard residential garages but with limited clearance. A typical single-car garage interior width ranges from 2.4 to 3 meters (94.5 to 118 inches), and depth commonly ranges from 5.5 to 6 meters (216 to 236 inches). The Sierra's length is close to the lower end of typical garage depths, meaning precise parking is required. Taller garage doors with at least 2 meters (78.7 inches) clearance are also recommended to accommodate the truck’s height comfortably. Overall, parking is feasible but users should measure their garage space carefully.

The maximum weight (gross vehicle weight rating) for the 1989 GMC Sierra 1500 I Regular Cab LWB Wideside is approximately 2767 kg (6100 lbs). This weight includes the vehicle’s curb weight plus passengers, cargo, and tow load. The relatively high weight reflects its robust body-on-frame construction, heavy-duty suspension, and reinforced chassis geared toward payload and towing capabilities. The truck’s weight affects handling by providing stability but can reduce nimbleness compared to lighter vehicles. Furthermore, the substantial mass translates to higher fuel consumption especially with the powerful V8 engines typical of the era. Owners should expect moderate acceleration but benefit from durability and performance across rugged terrains and work environments.

The 1989 GMC Sierra 1500 I (GMT400) Regular Cab LWB Wideside typically uses tire sizes 225/75 R15 or 225/75 R16. These measurements denote a tire width of 225 mm, aspect ratio of 75%, and rim diameters of 15 or 16 inches respectively. The taller sidewall (75 aspect ratio) provides enhanced cushioning over bumps, contributing to better ride comfort on rough surfaces. The tire widths give a good balance between on-road grip and off-road traction, making the pickup versatile for mixed driving conditions. Using 15-inch or 16-inch rims allows for a range of tire brands and tread designs, with off-road or all-terrain tires often preferred by users engaging in rugged or unpaved terrain activities.

The width of 1951 mm (76.8 inches) places the 1989 GMC Sierra 1500 Regular Cab LWB Wideside comfortably within the typical range for full-size American pickup trucks from the late 1980s and early 1990s. Competitors like the Ford F-150 and Chevrolet C/K series during this period had comparable widths generally ranging from 1900 mm (74.8 inches) to 2000 mm (78.7 inches). The Sierra’s width, coupled with its Wideside bed design, helped enhance cabin space and cargo utility while still remaining within legal road width limits for easy maneuvering. This dimension strikes a good balance between interior comfort for the driver and passenger and the external footprint suitable for a truck of its size and category.

The 1989 GMC Sierra 1500 I (GMT400) marked a significant evolution from its predecessor, the GMT400 truck generation introduced in 1988, replacing the older C/K series. Compared to the previous generation, the Sierra I offered an overall longer body length of 5547 mm (218.3 inches) owing to the long wheelbase configuration, which improved ride quality and cargo bed capacity. Width and height measurements were slightly increased, with the 1951 mm (76.8 inches) width enabling a Wideside bed design, a feature less prominent in the predecessor models. The updated chassis design provided better weight distribution and improved aerodynamics while maintaining the ruggedness expected of GMC pickups. These dimensional changes resulted in more modern styling and enhanced utility compared to the earlier generation.

In comparison to contemporaries such as the 1989 Ford F-150 Extended Cab and the Chevrolet Silverado 1500 of the same era, the GMC Sierra 1500 I Regular Cab LWB Wideside stood out with its slightly longer length of 5547 mm (218.3 inches), a key advantage in cargo bed capacity due to the long wheelbase. While widths were quite comparable—Ford F-150 models typically ranged around 2000 mm (78.7 inches) and Chevrolet Silverado about 1950 mm (76.7 inches)—the Sierra's Wideside bed design enhanced its utility for hauling larger or wider loads. In terms of height and overall weight, the Sierra matched well with its peers, designed for a mix of on-road comfort and off-road durability. Functionally, the Sierra's rugged chassis and refined suspension improvements gave it a smooth ride for a full-size pickup, balancing power, utility, and driver accessibility better than some rivals.

The 1989 GMC Sierra 1500 I (GMT400) Regular Cab LWB Wideside combines classic pickup truck strength with late-80s advancements. It features a traditional body-on-frame construction offering durability and ease of repair. The extended long wheelbase enhances stability and ride comfort, while the Wideside bed brings a wider cargo area for increased hauling versatility. Typical engine options ranged from reliable V6 and V8 gasoline engines, tuned for both power and torque to suit towing and payload needs. The interior was utilitarian but comfortable, with an emphasis on driver convenience and straightforward controls. Suspension upgrades in this generation improved ride quality over previous models, and overall build quality reflected GMC's reputation for robust work trucks capable of enduring demanding conditions.

While specific ground clearance figures are not provided, the 1989 GMC Sierra 1500 I (GMT400) Regular Cab LWB Wideside generally offered ground clearance suitable for moderate off-road use typical of trucks in its class. The combination of a rugged suspension setup and tire options (225/75 R15 or R16) provided enough height to traverse uneven terrain without undercarriage damage in most situations. This made the Sierra versatile for users who required both highway capability and occasional light off-road utility. However, it was not designed as a dedicated off-road vehicle like specialized 4x4s. Buyers focused on a blend of daily drivability and practical outdoor use would find the Sierra's ground clearance more than adequate.