4PCS Car U-Bolt Roof Rack Mounting Brackets Kit,Sturdy Car

VKQTS 4PCS Car U-Bolt Roof Rack Mounting Brackets Kit is a complete clamp set that secures roof boxes and accessories to crossbars up to 85 mm wide using galvanized U-bolts, plates, straps, gaskets and nuts.

Whether you’re adding a hard shell box, basket or cargo tray, these mounting brackets give a straightforward mechanical connection between your load and the vehicle crossbars. The kit is designed as a universal-style clamp assembly: four U-bolts with matching plates and hardware plus straps and sealing stickers so you can tighten and protect contact points. Built from galvanized iron and weather-resistant ABS components, the set focuses on durable fastening without complex tools.

How does this kit stop a roof box from shifting in transit?

The U-bolt geometry creates a firm mechanical grip around the crossbar while the plates distribute clamping force. Tightening the included nuts draws the studs through the bracket plate, locking the roof box base to the bar and minimizing movement under acceleration, braking and cornering.

• U-bolts provide strong clamping force for secure retention.
• Plates and washers spread load to avoid stress points on the box.
• Rubber gaskets and sealing stickers reduce abrasion and water ingress.
• Straps add a secondary tie-down for extra safety.

Which crossbars and vehicle setups are compatible with these clamps?

Check the crossbar profile before ordering: the clamps fit bars up to 3.35 inches (85 mm) wide and up to 1.06 inches (27 mm) thick. The kit’s U-bolt spacing and plate design suit many round, square and aerodynamic bars, but extremely large or proprietary factory mounts may require a custom solution.

• Maximum crossbar width: 85 mm (3.35 in).
• Maximum crossbar thickness: 27 mm (1.06 in).
• Works with most aftermarket and common factory bars—verify size first.
• Includes spacers to adapt to slightly different profiles.

What hardware is included and how do I install it?

The kit arrives with four U-bolts, four plates, eight nuts, four washers, two straps, sealing stickers, spacers and a simple instruction sheet. Installation is a basic mechanical assembly: position the plate under the roof box mounting point, fit the gasket, slip the U-bolt studs around the crossbar and through the plate, then tighten nuts evenly and secure any excess with the supplied seal strips.

• Included: U-bolts x4, plates x4, nuts x8, washers x4, straps x2, gasket sheet, spacers, instructions.
• Tighten nuts evenly to avoid twisting the box or brackets.
• Use seals to block holes and protect against corrosion.
• Add straps as a backup tie-down if desired.

How durable are the materials for outdoor and long-distance use?

U-bolts are made from galvanized iron for improved fatigue resistance and corrosion protection compared with plain steel, while the bracket plates and fittings use weather-resistant ABS to withstand UV and moisture exposure. These choices make the hardware suitable for frequent use and varied climates when properly maintained and inspected for wear.

• Galvanized iron U-bolts resist rust and bending under load.
• ABS parts provide impact and weather resistance at contact points.
• Sealing stickers reduce water penetration at fastener holes.
• Inspect nuts and gaskets periodically for safe performance.

Who is this kit for? The VKQTS 4PCS U-bolt Roof Rack Mounting Brackets Kit is aimed at drivers who need a reliable, no-frills way to attach roof boxes, baskets or accessories to common crossbars without specialized fittings. It’s ideal for weekend travelers, outdoor enthusiasts, and anyone upgrading or replacing worn clamp hardware, provided the vehicle’s crossbar dimensions match the kit’s limits. If you have very large factory rails or an integrated roof rail system, measure first or consult a professional to confirm compatibility.