Tonneau Cover

Snotattack · April 3, 2009

I was wondering if anyone else was having this problem. 2007 Chevy Silverado (New Style) I recently purchased a soft tonneau cover and installed it looks great. But on the highway or even sitting in my driveway I notice that there is a lot of air coming into the bed somewhere, especially at highway speeds it balloons up. Frustrated with repositioning it on the bed rails several times, could not fix the problem. So I had a friend close me up in the truck bed and noticed openings on the four corners underneath the bed rails that open up the the entire outer fender. Surprising enough these are not the stake holes, just big openings to the fender for air to rush in. So if any one else has had this problem let me know your ideas on a fix. I don't believe they make anything for this, haven't seen.

Rat4go · April 3, 2009

This probably isn't air finding it's way under the cover, it's the area of low pressure behind the cab causing the cover to lift up.

I'd bet that when you're rolling down the road, the back edge stays down, right?

MikeInCtown · April 3, 2009

This probably isn't air finding it's way under the cover, it's the area of low pressure behind the cab causing the cover to lift up.

I'd bet that when you're rolling down the road, the back edge stays down, right?

This is how my covers have always been. The back behind the cab suck up into the air and the back by the tailgate gets pushed down into the bows.

snarkee · April 3, 2009

when the shop installed the cover on my 04 they used a black putty type product to fill in the areas of the bed where it meets the side panels (the end near the cab). Where the sides connect to that end, there are tiny areas where air can get inside.

I've had 3 NBS trucks and they all do what your are describing. I checked it out and there are areas where air is getting in like on my 04. I just need to get some of that black stuff to plug the holes

You will never elimate movement of the cover because of downforce from the wind, but once the holes are filled it will eliminate most of the ballooning

Bmart · April 3, 2009

exactly what they said! so deal with it, or buy a hard top... not too much you can do about it..

Snotattack · April 4, 2009

I get you you are all saying, unfortunately the openings are under the rails themselves and not something that could be covered with caulk or anything like that. I could see daylight from them while closed in the bed. I did initially think it was air coming up from behind the cab lifting the front edge of the cover but it's not. Although I do appreciate your insights.

mattgob86 · April 4, 2009

I will have to agree with the "vacuum" effect from the aerodynamics of the cab. Even if you did seal up the holes that you are talking about under the rails, the lift that the cover gets from the air coming over the cab will suck air into the cargo box from the tailgate having air able to come in around it.

97SierraGMC · April 4, 2009

http://www.agricover.com/index.php/products/category/C156/

try that

nqabigt · April 4, 2009

http://www.agricover.com/index.php/products/category/C156/

try that

+1 Good product

robertmagni · April 4, 2009

I was considering buying a toneau cover does the ballooning cause any permanent damage to the cover?

rogerf · April 4, 2009

I was considering buying a toneau cover does the ballooning cause any permanent damage to the cover?

No, other than some chaffing over time between the fabric and the support bows. Had a cheap, snapdown cover that was over 5 yrs old and still in decent condition when I sold the truck. Dont worry about it.

66nova · April 4, 2009

I get you you are all saying, unfortunately the openings are under the rails themselves and not something that could be covered with caulk or anything like that. I could see daylight from them while closed in the bed. I did initially think it was air coming up from behind the cab lifting the front edge of the cover but it's not. Although I do appreciate your insights.

As others have said...this is not air getting into the bed. It is a pressure gradient. You have one area of high pressure and one area of low pressure creating lift. This is the same way wings on a plane work. The wings have a curve on the top, speeding up the air (this would be equivalent to your cab and tonneau) and on the under side they are flatter, creating an area of slower air speed(under your cover). This creates a vacuum effect.

This is a simplistic explanation, may be one of the many physics gurus will chime in and give a little more detailed reasoning, but this is the reason your cover is lifting.

Stevens03 · April 4, 2009

No big explanation.. but mine does it too, but no water ever gets in.

I think your fine.

Steven

c4cruiser · April 4, 2009

I don't have that problem with my Access Lorado (same company that has the seal kit in the link above). While my cover came with that seal kit, I have not installed it. Without the tailgate seal, any air entering through the holes in the sides of the bed by the stake holes or drain holes can exit around the tailgate bottomor sides. With the seal in place (assuming the seal covers all of the gaps) then any air entering the bed has no real place to escape.

One thing that I found is that the cover has to be installed and adjusted so that it fits tight. On my cover, the front rail has adjusting bolts at each corner. Those bolts are used to tighten the cover to where you don't see any sags or see the cross bars touching the cover. The cover should be tight enough that you can tap the cover like a drum and hear it.

My cover has 1" wide velcro strips that run the length of the bed and you can hand stretch the cover to the sides to git it tight.

It sounds like the problem is that the cover is not tight enough or maybe installed improperly.