So, you’ve installed a shiny new retractable tonneau cover on your truck, but it’s not sitting quite right. The cover might be sagging, difficult to open and close, or making concerning noises. Chances are, the rails need some adjusting.
Don’t panic! With a basic understanding of how tonneau covers work and a few simple tools, you can tweak those rails and get your cover gliding smoothly in no time. This comprehensive guide will walk you through step-by-step how to expertly adjust the rails on any retractable tonneau.
What Are the Components of a Retractable Tonneau Cover?
Before jumping into adjustments, it’s helpful to understand how a retractable tonneau functions. Here are the key parts:
This is the main vinyl, aluminum, or composite panel that rolls up to open the bed. The cover is attached to the rails on each side.
These metal tracks mount along the bed sides and allow the cover to slide back and forth. The cover connects to brackets that move along the rails.
The Tension System
This provides tension to keep the cover taut and in place. A tension block, adjustment bolt, or spring system pulls the cover tight.
This allows the cover to roll up, concertina-style, when opening. The pivot/hinge is located between the cab and the cover.
The Rear Roll-Up Bar
This bar attaches to the rear of the cover and helps it roll up evenly when opening.
Why Would I Need to Adjust the Rails?
If installed correctly initially, the rails should not need regular adjustment. However, over time issues can develop that require tweaking the rails to restore proper functioning. Here are some signs it’s time for rail adjustments:
The Cover is Sagging
If the cover develops visible sagging in the middle, the tension system likely needs tightening. This can allow cargo to push up on the cover.
The Cover is Hard to Open/Close
If the cover binds, sticks, or moves unevenly when operating, the rails may need aligning or lubricating.
The Cover Makes Noise
Squeaking, grinding, or banging noises when opening or closing the cover indicate the need for lubrication or tension adjustments.
The Cover Doesn’t Close Completely
If gaps appear between the tailgate and cover, the rails may need realignment to achieve a tight seal.
How Do I Access the Rail Components?
First, fully open the tonneau cover. This allows access to the underside where the rail components are located. Retractable tonneau covers either open by:
- Manual Operation: Release the rear latches manually, then pull the release strap to roll open the cover.
- Powered Operation: Press a button (usually in the cab) to activate motors that open the cover automatically.
With the cover fully open, locate the rail assemblies mounted to the bed side walls. Be sure to follow all safety precautions in the owner’s manual when working beneath the lifted cover.
Adjusting the Tension
Most retractable tonneau adjustment involves increasing or decreasing the tension on the cover. Here’s how:
For Covers with a Tension Block:
- To Increase Tension: Rotate the tension block to take up slack in the tension cables. This tightens the cover.
- To Decrease Tension: Rotate the tension block opposite to release tension in the cables. This loosens the cover.
Tip: Adjust both sides evenly to prevent uneven alignment.
For Covers with a Tension Bolt:
- To Increase Tension: Turn the tension bolt clockwise to draw the brackets tighter together.
- To Decrease Tension: Turn the tension bolt counter-clockwise to release tension between the brackets.
For Covers with Spring Tensioners:
- To Increase Tension: Compress or tighten the spring mechanism. Some have a bolt to tighten the spring.
- To Decrease Tension: Loosen the spring mechanism. Release pressure on the spring or back off the adjustment bolt.
Aligning/Adjusting the Rail Brackets
If the cover moves unevenly or binds, the rail brackets may be misaligned. Here’s how to realign:
- Loosen the bracket mounting hardware a few turns (usually nuts or T-bolts). Don’t detach.
- Nudge the brackets into proper alignment with the rail channels.
- Tighten mounting hardware once aligned. Test operation.
- Loosen and adjust further if needed. The cover should move smoothly when properly aligned.
Tip: Consult your manual for the torque specs on the mounting hardware.
Adjusting the Rail Stand-Off
Dual rail tonneaus have a stand-off bolt between the rails that sets the width. It gets tightened against the bed wall. Follow these steps to adjust:
- Loosen the stand-off bolt’s jam nut.
- Turn the bolt to press against the bed wall.
- Tighten the jam nut to lock in the adjustment.
- Repeat for both sides, keeping the width even.
Note: Overtightening the stand-off bolt can damage the bed wall.
Lubricating the Rail Channels
If the cover is squeaking or sticking, try lubricating the rail channels. Use a spray or gel lubricant made for tonneau covers. Avoid harsh chemicals that can damage finishes.
- Fully open the cover to access the rails.
- Thoroughly clean the rail channels with a degreaser.
- Apply lubricant to the upper and lower rail channels.
- Manually slide the cover back and forth distributing lubricant.
- Wipe away any drips or overspray.
Tip: Re-lubricate a few times per year to maintain smooth operation.
When to Call a Professional
While most tonneau adjustments are straightforward DIY projects, there are a few cases that call for a professional:
- Broken or severely bent rail components.
- Stripped or damaged tension adjustment threads.
- Major cover damage or loosening that requires removal/reinstallation.
- Malfunctioning electrical components on powered covers.
- Alignment issues where the cover simply won’t sit square no matter the adjustment.
- Any other problem you are unable to diagnose or repair after working through this guide.
Truck bed cover shops have the expertise to tackle repairs beyond basic rail adjustments.
Keeping your retractable tonneau cover sliding smoothly requires getting under the hood (cover) periodically to check and tweak the rails. Following this comprehensive guide, you can dial-in the perfect tension, realign components, add lubrication, and perform any other rail adjustments needed to keep your cover functioning flawlessly. A finely tuned tonneau means years of dry cargo and stylish looks. Just don’t be afraid to get your hands a little greasy in pursuit of truck bed nirvana!