TR2/3/3A To undercoat or not to undercoat

[Member 10617]

Need some expert opinions on this one....

When I purchased my TR3, the front wheelwells had been treated with undercoating, but the rear wheelwells had not. I don't have any idea why one was done and the other was not done.

From time to time, I touch up the front wheelwells with Eastwood Rubberized Undercoating, and it does an excellent job of preventing chips and even provides a little sound abatement.

The rear wheelwells look great painted the color of the car.... but .... I have to sand, treat, and repaint them about each year because of chips and resulting rust. I have just gone through that routine again and am thinking that I don't want to do that any more. I'm thinking I need to treat the rear with the Rubberized Undercoating.

As I said, the wheelwells look GREAT painted.... but...

What would you do? Is there some good reason for leaving the rear wheelwells just painted?

This is not an especially important issue, but once the undercoating is on... it is on...

Any advice?

 

[mallard]

On my TR6 I got some blank sign magnet material from the local sigh shop for almost nothing since it was mostly scraps. I then cut to shape and painted them body color. They stick to the bottom of the car without moving, and protect from any stone damage. Occasionally I hear a dull thud from a rock hitting the magnet instead of the inner fender. Since you've don it in the past you should know where the problem areas are. You just pull them down to clean once a year. Nobody has ever noticed them on the car, and I've had people look inside the fender wells.

 

[Don Elliott]

I finished my total body-off restoration in 1990 and today, when you swing your fingers up under my front and rear fenders, they are as smooth and nice as the outside of my 1958 TR3A. I have never had any rust develop anywhere on the car since 1990 (111,000 miles). If you were to give me a couple of hours and some white spirits, I could have the entire bottom side of the floor pans etc. just as nice all over as they were 23 years ago. All I have is 2-part paint and I have no undercoat. In fact when I bought this TR3A (brand new) in 1958, I paid $35.00 to have it undercoated and that's the worst decision I made. It was like tar and it cracked with age and water got in behind the undercoating and rusted many parts of the body and floor pans right through.

 

[tallguylittlecar]

I would suggest using GRAVITEX PLUS stone chip protector. Sprays on to prevent stone chips and can be topcoated with body color.

https://www.tcpglobal.com/detailsupplydepot/dsd18.aspx

 

[alanjohnturner]

The wet and humid climate of the UK makes it much worse for corrosion than much of the US.

Thirty years ago we are used rubber based "underseal" here.

It works well. But only for about 10 years. Then as Don says the water gets behind it as it looses adhesion to the surface beneath.

The problem is you cant see this happening. The first you know is when a hole appears.

In areas that you can easily see, that get a lot of impact from road-grit, this stuff is OK. But you have to keep checking that its still well stuck on.

Hidden corners where mud and water collect are best left painted, and for Winter use, washed and coated with a waxy product. This will be gone by Spring but this does not mater.

I'd be trying to get the stuff off your front arches!

 

[PeterK]

Have you considered truck bed liner spray? ISTR mention of someone using it on the underpans and it worked out quite well.

 

[Member 10617]

Thanks for all the good ideas. I have always heard about the potential problems with undercoating, and that's one reason I am reluctant to use it where it isn't already on the car.

As for trying to get the stuff off my front wheelwells, there's not much chance of that. The PO treated those areas years ago, and the undercoating is hard as a rock. So, I inspect it from time to time and touch it up with the rubberized undercoating.

I looked into using bed liner, but decided against it for some reason I've forgotten -- something in the instructions that turned me off. I have also thought of spraying two or three coats of clearcoat on the painted wheelwells.

As with Alan in the UK, the humidity here in Virginia is high -- very high this summer -- and anything that can rust, will rust.

For a couple of years I had some thick vinyl shelf padding taped to the exposed areas of the wheelwell, and it worked very, very well. But I was concerned that moisture would build up behind the vinyl and cause rusting, so I removed it.

Tallguy's recommendaton of GRAVITEX PLUS looks very promising. It can be brushed on top of a painted surface. I would probably choose the black color and not paint over it with body color. This way the back wheelwell color would match the front black rubberized undercoat color.

 

[Member 10617]

Don,

I believe you are right. The old undercoating was a tar-like substance. It was a mess, dried out, cracked, was difficult to remove. The new stuff appears to be a rubberized substance. It dries quickly, seems to seal well, and seems to remain flexible for a long time.

That said... I've decided not to undercoat my rear wheelwells. Instead, I'll try the GRAVITEX PLUS. It seems to have a number of advantages over undercoating, including the ability to be painted over with body color, if needed. Sounds good.

The inside wall of my wheelwell doesn't receive any of the grit and stones, so there are never any chips or rust marks on it. So.... as a starter ... I plan to mask off that part of the wheelwell that can be seen easily when the wheel is off and leave it body color. The parts that receive the grit and stones (the outside wall, top, back, and front), and therefore that chip -- mainly unseen unless you look under the car -- I will teat with the GRAVITEX PLUS and leave that black. If I decide that looks odd, I can always apply the GRAVITEX PLUS to the inside wall later.

This is certainly not a very high-tech or critical "problem," and I appreciate folks taking the time to advise me, but it is an area that seems to need fairly constant attention because of chipping.