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Stretch a Tonneau??

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glemon

glemon

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I have a nice used tonneau cover for my car, unfortunately it has shrunken with age, it is an Amco tonneau. I know they get a little more supple in the hot sun, but that was not enough, is there any way to spray them or soak them with something that helps them stretch back to their original size, I just can't quite fit it as is. Or am I just out of luck.

Thanks, Greg
 
Greg
Just did the same thing. I had an old ( but in good shape) tonneau that I wanted to use. It liked about an inch or more fitting. I put it on as much as it would go. Used cable ties in the front eyes to stretch out. Let it sit in the garage for a couple days, tightening the cable ties daily. It was sunny last week so after a couple of hours in the sun I got it hot enough that I got it to fit nicely on the car. So yes, it will stretch back out.

Marv
 
Well, as you said, heat will do it. You have to heat it and then stretch it while still hot. The problem is applying the heat without burning through. I don't think you can heat it in an oven and then stretch it in time before it cools. I have used Monokote heat guns...from the RC airplane hobby...that work great. It's like a paint stripper gun, only it has a temp control so you dont burn through the vinyl. It only heats about a square foot at a time, so you'd have to work across the tonneau, stretching and snapping as you go. Another option may be a portable heater you can use to blow more hot air.

The only problem...if the vinyl is really old, it won't give much. I've been able to stretch 33 year old tops back out...but have also had 10 year old vinyl rip on me. UV damage over years makes vinyl brittle. But, it sounds like you have nothing to loose in trying...it's not usable as it is...

John
 
I've been trying an experiment over the winter with a tonneau in really nice shape except that it's about 1/4" short to really fit well. It's been hanging like this since last November in hopes that it will stretch just enough for a consistent fit. I'll know for sure when it warms up a bit out side.

Tonneau.jpg


That's a paint can hanging from the bottom 2x4 to add weight!
 
If you do get the tonneau on, put a brick or equivalent on it and let it sit in the hot sun for a day to stretch it.
 
The tonneau on my MGB will be tight too. So I'll do what I've done in the past. Put it in a warm area of my basement near my water heater (not too close) and hang it from something. Let it sit there for a few days and then blow an electric room heater against it for an hour or so before fitting.

Use the brick (or similar weight) that John suggests to keep it fitting. Be sure to add some vinyl protectant to it after heating, since they can become overly dry and crack.
 
Same issue here as well, I attached the rear deck portion and snapped as much as I could up and around the sides to the doors then took cargo ratchet straps and fitted them with male snaps snapped them on the last snap at the A post then put small vise grip on each to keep from unsnapping next found a spot to connect on the wall and began the process of stretching the top. Make sure you put the car in drive w/ emergency brake engaged, I also gave the underside (fabric) a good dose of silicone spray to re infuse the material with some elastic properties.

All of this to preserve cover and the original silver Triumph logo located on the top of the cover at the Passenger door B post.

oh ya it worked like a charm took two days with Spring temps
 
Some good ideas here. I have not tried to fit mine after 40 years but I do remember that it took about all the strength I could muster to get it to the snaps back when all was newish. Tom
 
lbcs_r_fun said:
What about just leaving it on all winter?
Click to expand...

Experiments conducted at HSTRL Soggy Bottom have shown that this causes mold to grow in the interior.
 
Thanks guys some good ideas, I am still not overly optimistic, I can't get it to snap around the convertible top in back, I have not even tried to attach it front to back, but even if I could just use it as a boot cover for my convertible top I would be happy.
 
I had to make a modified version of the front snap plate to gain a quarter-inch.

TonneauSnaps.JPG


I suspect they make the patterns for the replacements using original tops & tonneaus... that have had 50 years to shrink!
 
Lie it out in the hot sun for a while, like on an asphalt driveway so it gets good and hot, then start snapping with the front middle, on the dash. Do all three front snaps first, then go to the rear center snap and get it if you can. If you are able to get the rear center snap, you should be able to work your way around from there, then after they are all snapped, put a brick or something on it like John said and let it sit overnight at least.

You didn't say how much it was short. They are supposed to be tight. I can never get all my front snaps on if I start snapping on the rear.

Dan B
 
Stretching did not work for me so:
I had two short leather extensions sewed to the cover with snaps on the opposite end of the extension. Also added snaps on the cover adjacent to other snaps where appropiate. Did not have to sew them but chose this solution to avoid misplacing those extensions.

Robert
 
I acquired a TR-6 about seven years ago. Among the "accessories" was a tonneau cover. I tried to fit it, and it seemed too small. So, I constructed a wooden frame to stretch the thing. I pinched the front edge between two 1 x 3 pieces of pine using the through holes in the tonneau cover for 1/4 x 20 bolts that tightened the grip, and squeezed the rear edge in a similar fashion with boards in which I bored holes large enough to fit over the snaps and allow the fabric to be gripped by the surfaces of the boards. The two pairs of clamping boards were mounted in a frame of 2 x 4's with some spring-loaded straps. There was probably about 40 to 50 pounds of pull trying to make the cover longer. I made an initial measurement of distance and happily noted an extension of about 1/4 inch overnight. Realizing more time might be needed, I've let it sit in the basement near the furnace and hot water tank. That was two years ago, and it has not stretched any more.

Meanwhile, other projects on the car revealed that the convertible frame had been installed incorrectly and was not folding completely. Suspecting that to be a significant contribution to the previous fitting failure, I released the cover from the stretching aparatus and tried again (after repairing the frame problem, of course). It's still short by something in excess of an inch.

So, presently I'm surfing around trying to learn (a) whether vinyl reasonably can be expected to stretch an inch over a distance of ~6 ft, (b) what magnitude of force might be required, (c) what kind of materials can be applied to vinyl to make it more compliant and (d) what dimensions of snap placements might be for a TR-6 versus other sports cars of the era - after all, I might have a tonneau cover for some other brand or model. If I learn anything significant, I'll post
 
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