To Undercoat or Not to Undercoat....that is the question

[ThatOneZ]

Im right about to get a 280z and i was thinking of undercoating it but i have heard from alot of people that you could trap moisture in and cause more rust. The area where  i live the roads get salted in the winter and during the summer im near the ocean. What are your guys thoughts on undercoating also what products would you use. I have heard that POR-15 is good and zero rust is another one ive heard people use alot.

Edited October 1, 2013 by ThatOneZ

[RebekahsZ]

First, clean and paint any chipped paint. Then undercoat only the area in the back of the fender wells that are subject to rock chips.

[magnum44]

I just finished restoring my 83 turbo zx ...and I did a lot of research and I  went with "por 15" that stuff is awesome at stopping rust and it's expensive too..I would highly recommend it...I paid around 155.00 a gallon... I did the inside as well as the the whole under carriage...

[m1ghtymaxXx]

Rubberized undercoat killed my 83, I would never go that route. It eventually separates and traps water. I'd say a coat of good rust inhibiting paint followed by an oil treatment (Krown, Rustcheck etc.). 

 

Like RebekahsZ said, the rubberized stuff should be fine in wheels to prevent chipping and cut down no noise, I'd check it once a year or so to make sure it's still properly adhered though. 

[RebekahsZ]

I hate all undercoat but I've got to get a plan to stop all the chips in my wheelwell. Wasn't a big problem until I started runni g race rubber which picks up EVERYTHING and throws it at the paint. Would I be better using a tar based product? Looking for advice, maybe even from the racers. I sure don't want to promote rust!

[socorob]

The tar based stuff is probably 50s technology. I just used lizard skin which is water based and seems to be fairly flexible. I will report back in 10 years and let you know how it's holding up! In all seriousness though a chip in the paint starts rust and those occur much faster under there than undercoat cracking does.

[NCchris]

Hi socorob, which Lizard Skin did you use and why? My shell is upside down on a rotisserie after floor and rocker replacement. Now is the time to do it. I'm thinking a coat of epoxy primer and then  Lizard Skin. Anything else?

chris

[johnc]

There are good and bad undercoating materials. Now that I'm working on vintage Porsches (which were under coated from the factory) I see how proper undercoating can preserve a chassis.

 

Nothing from a spray can is effective over the long term because its thinned and diluted with carriers to make it sprayable from a can. We use Wurth Stoneguard which also requires their spray gun or any spray gun that can handle high viscosity material. We shoot it at 60 to 80psi.

[z-ya]

What about using a couple thin coats of urethane bedliner?

[RebekahsZ]

Does the rubberized stuff scrape off pretty easily? If so, I can just consider it a every-two year maintenance task to replace it.

[socorob]

I used both the heat and sound. I painted the bottom of my car with rust shield and ended up having to scuff every inch of it. If i had it to do over I would use epoxy primer with the luzard skin over it. i have no personal experience with it but know some hot rod guys who said it made huge differences on sound and heat in their cars. If you do both under and totally inside the car it seems like it would only gain about 30 pounds  of weight, its fairly light.

[cockerstar]

I have 4 bottles of Wurth Stoneguard and their applicator gun waiting for me to get the underside of my 71 stripped and the Bad Dog rails welded in.