Need Undercover Flex Ultra install tips

mdrew · July 27, 2017

2015 Sierra Denali, 6.5' bed.

Just installed a new Flex Ultra yesterday and ran into some issues. Looking for input on the installation.

The main problem is installing the rails with the type of clamps provided. The bed rails have a slight upward bow in the middle. These rails that come with the Ultra have a lip that rests on top of the bed rail cover. I can hold the rails down (slightly bending them) to maintain contact with the bed rails, but this puts a bit of a twist in the cover rails. Also, when clamping the cover rails to the bed rails, the cover rails want to twist downward, and no matter how I position the clamps or tighten them, I can't get them to not twist. These two issues are causing a double whammy of sorts. I also cannot keep the rear of the cover rails held tight to the bed rail without the tail gate hitting it and not closing.

Any sage advice or tips?

Donstar · July 27, 2017

I have never installed one but the first thought that comes to mind is the one you bought doesn't fit. I'd take it back!

O_J_Simpson · July 27, 2017

Exchange it.

aseibel · July 27, 2017

I'd be calling the manufacturer first. They should know if you're doing it right or of there is a defect.

martha3065 · July 27, 2017

I did not have the rail issues on installing mine on a CCSB, but did have the issue at the tailgate. I don't think that can be avoided based on the design. Tonneau rails are slightly raised off the bed rails on mine to allow clearance for the tailgate to open/close. Its hard to tell though once the cover is on and the rubber trim covers the rails.

mdrew · July 29, 2017

Thanks.

I spoke to an installer and he told me that he will push the cover rails down to the bad rail covers, then snug the cover rails. He also said the cover rails will twist as I have found. He suggested that I adjust the latches. Told me they have a couple mounting screws that can be adjusted. I have not taken a look at them yet.

martha3065 · July 30, 2017

Thanks.

I spoke to an installer and he told me that he will push the cover rails down to the bad rail covers, then snug the cover rails. He also said the cover rails will twist as I have found. He suggested that I adjust the latches. Told me they have a couple mounting screws that can be adjusted. I have not taken a look at them yet.

I had to adjust my latches as well. Weren't wide enough (close enough to rails) to latch at all points.

Imcrazy · July 30, 2017

Have they fixed the water intrusion issues with those covers? I had one a few years ago and it just didn't keep the bed anywhere close to dry...

martha3065 · July 30, 2017

Mine would be 100% waterproof if I would put a seal around the tailgate. Cover itself doesn't let any water in, but it comes in on the sides of the tailgate. Not enough for me to need to worry about to this point.

Silverado Steve · July 31, 2017

My undercover flex is great. The trick i found is dont overtighten the clamps as this is what causes them to want to turn downward. Second, you need to make sure the rails are mounted about 1/8 of an inch from the top of the bed, or the actual cover will end up sitting a bit above the bedside causing leaks. Last make sure the back of the mounting rail is about 1/8 from the back of the bed/tailgate. If you have the mounting rail butted up against the bulkhead of the bed, the back panel will not cover the tailgate and you will get leaks.