I tried searching but haven't found any threads (or recent ones)...looking to get some opinions.

I'm trying to figure out the best option for my car's underbody & fender wells. Some of you might have seen my build thread - I have the car torn down to the chassis and I'm rebuilding from there. I just finished painting my engine bay, and now I want to tackle the fender wells and underbody before I start bolting parts back onto the chassis.

Before cleaning:


After cleaning:


I know some people have used rubberized undercoating in these areas (e.g. TwinCharged RX7, muibubbles, David Hayes...) so my first question is for these guys (if they see this): how's it holding up?

I've heard some people use the "Rhino Liner", "Raptor Liner", or "Lizard Skin" liner, which are epoxy based products. Seems people swear by the stuff - but I'm not sure how much weight that type of stuff adds.

Thoughts and opinions? Also post up some photos if you've used any of these spray-on liners.

 

hahha my name was thrown in the mix. yeah i use duplicolors rubberized under coat... its holding up okay... if i were to do it again id use some bed liner stuff. i dont really have a reason why, I just feel like i would have a better piece of mind if i did. i "feel" like the rubberized stuff isnt as tough...... If i did it again, i weight wouldn't play a roll in my decision... just my .02

ps your fenders look pretty good as is..

 

I have rubberized liner on the bottom of my chassis. It holds up ok but is sorta sticky and collects little rocks and stuff. I'm not sure what kind it is but if I had to guess I think it's probably the stuff they line truck beds with. All in all though, I'm pretty happy with it but I don't think I'd apply the stuff somewhere that can be seen. Must be a pain to clean.

 

I'll give you my mini-rap on DIY undercoating, the places on a car it works the best is in areas that don't get hit by rocks and road debris, but it can help there too if checked once in a while and resprayed. If you go into a junkyard that has cars that have been sitting for decades, there is usually one part of the car that isn't rusty, and that is the crossmember under the engine because it is coated with oil that has been held in place by oily dirt. Rust is basically metal recombining with Oxygen. Paint, wax, galvanzing and oil prevent that. Undercoating coats the metal with oil and then covers that with a protective layer to keep the oil from getting washed off.

You don't live in the rust belt where cars get eaten up by road salt, but you want to protect the chassis so it doesn't deteriorate and undercoating is the way to do it.

One great trick is spray lightweight oil on the chassis before undercoating it and to respray oil on top of the undercoating about once a year. People frequently use undercoating to hide rust, but if you have some "before" pictures you can show that's not what it's on there for.

If you're really into it you can buy kits to spray inside box sections by drilling access holes and using long wands with spray heads, then put plugs into the holes. Most undamaged non galvanized body panels rust from the inside out, starting at spot welds.

 

I live in FL so salt on the roads isn't an option. Also the car is no longer a daily driver.

Another spray-on "bedliner" I was looking at is this Line-X stuff.
LINE-X Sprayon Bedliners, Protective Coatings, Truck Bed Coating, Floor Coating, Industrial Flooring

I googled, and it looks like the guys on the various trunk forums are using epoxy-based spray-on bedliner in their wheel wells with excellent results (resistant to chipping, easy to spray off dirt, etc.)

I'm going to keep researching. I have access to an air compressor so the epoxy-based spray on stuff is still an option at this point...would like to hear some more opinions and see if anyone chimes in that has used similar stuff on their FD.

 

I used rubberized liner for the fender wells. Its holding up ok. I second what Supernaut said, its kinda sticky and can collect dirt easily. Higer temps will affect it also. Luckily I live in Canada where its cooler. If I was to do it again I would look into Line-x.

 

I hate the rubberized under coating.

A cadre of car geeks here are in love with the vinyl Duplicolor truck bead liner.

I used it on my stock FD wheels I put on my Mazda3 and it is super durable.

Friend did his front splitter, hood and other parts with it. It resists chips very well.

Basically, I look for excuses to use it.

I think I will do up my PF01 once they start to look a bit haggard from racing.

 

I am a paint and body guy. Just don't put it on plastic pieces. After a while it will start to fade and cleaning it/putting shine to it won't do well

 

How about POR15?

 

Yea, wouldn't POR-15 work well? I think I've seen a lot of people use it for their underbodies too

 

I wouldn't spray the car with anything at all. There is some factory undercoating, is more needed? What for? Cover up the holes that were covered in the frame rail, put it back together and drive it. The fender wells look great. I had a FD once that had undercoating sprayed on at the dealership, it drove me nuts worse yet, they sprayed the suspension pieces and some of the brake lines and ABS wires.

 

I just picked up a car that is totally coated in that stuff,and I wanna kick someone in the Gonads.
When I re-did my first Fc wheel wells,I got them as clean as I can.Then I sprayed Gloss black Vinyl Paint in them.(Krylon plastic paint).That way it adhered to everything in the wheel wheel and actually has held up fairly well considering I am located Way UP here.
Edit: I used the same paint to change the car color.(beater car,so rattle canned.) It turned out real good.Changed the Color from Grey to Black.It's held up fairly well also But I am going for a color change this year.

 

dumb question here, but how did it come new from the factory? Is the 2nd (clean) picture the factory undercoating, or were the wheel wells originally bare?

 

Factory did have a coating in the wheel wells and on the gas tank.

Tom, your coating generally looks good. I wouldn't spend a lot of time and effort on the subject - if there's spots that need a touch up, use a rattle can of some kind to touch up/recoat the surface and be done with it.

I used some rattle can stuff on my gas tank and rear inner fenders a while back just to freshen then up, looks great and seems to be holding up. Some sort of pro stuff that's 2-part and needs a spray gun will be far more durable, but you're spending more time and effort at that point than what the car really needs.

If you had a truck that was frequently going off road and was rock chipping the fender wells with all the crap from off roading, fine. But, a sports car won't have that problem, and a modern sports car with a body that's been rustproofed from the factory. Modern cars don't have anywhere near the rust problems that classic cars did.

Dale

 

From the factory it came with some flat black stuff sprayed on the side (around where the suspension mounts). The rear area and upper area have some kind of wavy/textured finish, but I'm not sure if that was stamped into the metal or if it was somehow applied after chassis assembly.

(Edited to add Dale's feedback / respond): I agree, but my car took some abuse from being up in New York City and I had to really scrape some areas to get tar and asphalt off. I was thinking about just touching up those areas where I could see bare metal, but I would really like to do something even/consistent in all for areas. That way I know everything was re-done at the same time. Since I have the car torn down this much, I really want to make sure everything is cleaned, restored, or improved as things go back together.

So I talked to a local friend yesterday about this subject. He has a dedicated track car that he runs at Sebring a lot. I asked him what he thought would the best treatment for the wheel wells and he said that for his car he used the off-the-shelf Dupli-Color bed liner that you can buy at Advanced / AutoZone. It goes for about $9 a can but they also have another kind with a fancier label thats $12/can (I have a feeling they're the same product...lol). It even says "Ideal for: inner fenders" right on the label.

Dupli-Color :: Truck Bed Coating




From what I understand, it's a "happy medium" between a hardened epoxy bed liner and a softer rubberized coating. It's also removable (using Xylene) so if it doesn't hold up I can always go with something else.

I trust my friend's advise so I'm going to give it a try with the Dupli-Color spray-on coating. I bought a rattle-can of the stuff last night, so I'll mask off and spray at some point today and I'll share results.

 

Yes, thats the stuff my friends and I like as well.

It does adhere to plastic fairly well with some prep compared to most aerosol paints since it is flexible even when thick. It doesn't adhere to plastic as well as a dedicated plastic paint.

For a piece like the plastic fender liner, I second the idea of cleaning it well and if not happy with the appearance- prep the surface and paint it with a black plastic paint.

A friend sanded his urethane bumpers to get the old paint off (it reacted poorly with the bed liner) and sprayed it on. It has held up well for about a year now of daily driving as well as driving for sport/pleasure.

He applied a thin coat over his rocker/lower door panels with no prep and it has chipped off of an area where he sprayed over a decal a bit.

Because it is flexible vinyl it seems the thicker you put it on the less it will chip away, unlike most other paints.

 

Per the note above, how would you spray light oil on the chassis and then coat it? I've never seen a paint-like substance that claims to stick to an oiled substance. The first thing it always says is completely degrease and clean the surface.

 

So I finished cleaning the front passenger wheel well and then gave it a once over with prep spray. Masked everything off and sprayed with the Dupli-Color Truck Bed Coating (same as pictured in my previous post). I'm happy with the results. Now to see how long it lasts...

I did two coats, which took about 1/2 the can, so I'll have to get a second can to do the rear wheel wells. I'm also going to coat the transmission tunnel the next time I have the car on a lift.

Before spraying:


Spraying:


Removing masking:


Complete:

 

I've used the Duplicolor bedliner on my Shine front lip, skirts and diffuser. It has ben holding up well for a couple of years now. Nice thing is when the front lip gets scraped, its easy touch up.

On these fiberglas pieces I cleaned them with dish wash soap, sanded with scotch bright pads, cleaned again with soap then applied Duplicolor adhension promoter before applying the bed liner.

Jack

 

I rolled my car out of the garage again to finish cleaning the rear fenders. Here's another shot of the coating on the front, in the daylight.



And then I cleaned the rear a bit more. Another hour of scrubbing got me here:



Masked off the area and then did a final wipe-down with the prep all spray:



First coat down:



Second coat down and masking removed:





I'm very happy with the results. I still want to do my transmission/driveshaft tunnel...

 

Looks great. I might have to try this out.

 

Peter, you are probably referring to my post where I discussed first using spray oil on the chassis before using a petroeum based undercoating. The advantage of this approach is that the oil seeps into spaces between panels etc before sprayig on the undercoating which helps prevent future corrosion and can also stop the spread of any current rust areas.

A oil prespray would not work with paint, not sure about if it would work with any bed liners and my experience with the prespray is that it can make the application of undercoating a little more difficult on vertical panels, if too much undercoating is sprayed on at one time and/or insufficient drying time is not allowed between applications, it can run or separate.

 

Figured I would post this here as well...

Did the first 1' of the driveshaft tunnel from the firewall:

 

looks good

 

looks really nice. i'll do this eventualy