For the car paint experts

[Boba]

Hi guys, I have a 350z and my rear muffler tip is currently touching and burning off my rear bumper because it is tilted outward diagonally. I'm thinking about trimming my rear bumper thinner with dremel and then repainting the rear bumper two-tone and would like your opinions/advice. Scroll to the bottom for my plan of attack.

This is what I mean, except it's a tilted exhaust tip:




The red highlighted part is the part I want to repaint:



------------------------------------------------------

1. Basically, what I am going to do is dremel the part that is touching my muffler tip down evenly (on the other side as well) and use sand paper to smooth the surface.

2.Then I will use tape to shape out the part of the rear bumper that I do not want to get re-painted, leaving the part I want to get re-painted alone. Of course, I'm going to have to do very precise taping to make it straight and round on the edge that's circled above.

3. Next, when it's all taped up, I will use chemical paint strip to strip the paint.

4. Then, I will lay primer

5. Then off to paint using spray paint.

6. Clear coat the part and wait for it to dry.

------------------------------------------------------

Do you guys think it is do-able? I want to save money by not bringing it to a bodyshop and having them re-paint the bumper. Please let me know if my procedures are correct, and if there is any advice you can give me.


Thanks a lot for reading this long post !

[Eddie6th]

Re: For the car paint experts

I'm not a car paint expert but I can give you a little bit of help here as I've done this about 2 years ago.Unfortunately,I made the opening a little tight and it rattles when i drive,but i don't get any burning. I'm going to redo it,though.

Think carefully about this before you start.If you make a muck up of your bumper,it'll cost you to get it fixed.

First,if you really have to go ahead with this,think about the design.Do you have an art program like www.artweaver.de ,which is free to download? You can try out some designs,without being complicated.

If you manage to get a design which is simple but effective,you will then have to mark this out precisely on your bumper.Even if you make cardboard stencils to get perfect circles,this will help.

A dremmel is a bit small for doing this,but i suppose can be done with the correct attatchment.

The problem here,is that you might have to do some filling and reshaping if you want it to look good as if it were an original part.

You don't need to use any paint removers.It's not advisable.You mentioned repainting two tone....In other words,you want to respray from a can? Possibly black?

It looks like a nice bit of kit! I would recommend you go to a bodyshop and get it done professionaly.I'm assuming that you've never done this before?

Cutting the opening is not the hard part,but it's the filling,sanding and repainting which needs to be precise. I was fortunate enough to know people from a body shop that let me use their facilities and although i did a lot of the work at home,I did a lot of the finishing work at the shop,with thier cooperation.

Go and see how much it'll cost before tackling this yourself.

[the_invisible]

Re: For the car paint experts

I installed a couple of GReddy exhausts on a few 350Z. I believe it is designed with the stock rear bumper in mind. Even with the stock bumper, the GReddy muffler is a tight fit.

I can guarantee you that using a Dremel is a bad idea. The Dremel will cause rugged edges, and those edges will be very noticeable if you make a long trim.

I suggest you use an angle grinder using a blade designed for fiberglass or softer body panels. If cut properly, you can get away without having to repaint the body. I've done it many times in the past on my drift car.

[Eddie6th]

Re: For the car paint experts

I just had another look at your pic. Your rear bumper is not simple. If you were to make the opening any bigger,you will somehow have to reshape and design the 'lip' area.

In this case,i'd definetly go and shop around.See if you can get a good deal from a bodyshop.

[Boba]

Re: For the car paint experts

Thanks for all the advice. Wow it seems a lot harder than I thought it was.
Is it not possible to dremel it to about 1/8" left of my desired size, then sand it down with sand paper and also "reshape" the round edges?

Actually, it is fine as is because the burn isn't really noticeable, but like Eddie said, it rattles when I drive because it's touching the bumper.

Estimate is around $250 to repaint it, and I just think that it is not worth it to repaint the entire flawless rear bumper just to fix such a small portion.

Also, the material is polyurethane. How is prepping work done for PU? Is it possible to sand it at all?

[Boba]

Re: For the car paint experts

I just had another look at your pic. Your rear bumper is not simple. If you were to make the opening any bigger,you will somehow have to reshape and design the 'lip' area.

In this case,i'd definetly go and shop around.See if you can get a good deal from a bodyshop.

Hi Eddie, I'm basically going to make that lip part of the rear bumper "thinner" about 3 cm so my exhaust won't touch it.

[Boba]

Re: For the car paint experts

To Eddie: If I don't use paint remover, are you saying I can just paint over the existing paint?

To the_invisible: If I don't repaint, wouldn't paint start to peel later on?

Someone also recommended me use the Dremmel emery wheel for trimming, and then using a fine metal file to shave off the edges.

Also, here's something I found on the internet. I'm not sure if he is using a dremel though The result was prettyyy smooth:

[the_invisible]

Re: For the car paint experts

You can use a dremel if you are going to use grind down on the rugged edge.

It's hard to say if paint is going to peel off. It will on a metal. But on a plastic that's quite rare.

Maybe it's more cosmetic appealing and cheaper to have the exhaust tip adjusted by means of cutting and welding? Or perhaps an exhaust upgrade?

[Boba]

Re: For the car paint experts

You can use a dremel if you are going to use grind down on the rugged edge.

It's hard to say if paint is going to peel off. It will on a metal. But on a plastic that's quite rare.

Maybe it's more cosmetic appealing and cheaper to have the exhaust tip adjusted by means of cutting and welding? Or perhaps an exhaust upgrade?

My rear bumper is polyurethane material
which leads to my next question.... Is it possible to sand PU material?

[Eddie6th]

Re: For the car paint experts

That is not a dremmel in the picture.That is a proper grinding tool operated by air compressor,typically found in body shops. If you have a compressor..you can buy these.It doesn't have to be top line professional stuff. I bought a cheap one a couple of years ago and came with a lot of grinding stones. Maybe 25$? It's okay here because I'm not using it every day as in a bodyshop....Just now and again.

The problem with the dremmel is that they are a bit lightweight and small for this kind of work. If you try to smooth an arch or circle with it,you might end up making an irregular line.
Basically,the old paint would just be sanded down and then resprayed,so there is no need to remove any paint chemicaly.

Nobody's is trying to spook you here. Just it's a nice kit. So think carefully before you start. Even if you go to a bodyshop for advice. One member here does a lot of bodywork...'Shyneman123'. I'll send him a mail and he'll be able to advise you about this.

[Boba]

Re: For the car paint experts

^ I really appreciate your help Eddie.
Do you have any recommendation for what grinders to buy, particularly what kind of grinder?
I'm in no rush will be having a few helping hands so I'm pretty sure with patience and preciseness, I will be able to tackle this project. However, I heard somewhere that polyurethane materials needs to take more time to prep and paint so that the paint will not peel off.

[Eddie6th]

Re: For the car paint experts

^ I really appreciate your help Eddie.
Do you have any recommendation for what grinders to buy, particularly what kind of grinder?
I'm in no rush will be having a few helping hands so I'm pretty sure with patience and preciseness, I will be able to tackle this project. However, I heard somewhere that polyurethane materials needs to take more time to prep and paint so that the paint will not peel off.

Here's a pic of the grinder that i bought. It was inexpensive. They're okay for hobby usage. I think this one is Einhall,but there will be loads of equivalents out there.
Well,if it's ABS plastic it should be okay.I sanded and primed,painted as normal and the paint is still the same.It hasn't peeled. Again,if you check later,Shyneman will be able to answer that for you.I sent him a message,so he'll probably be on later.

[Boba]

Re: For the car paint experts

Cool, what kind of type of paint did you use? Spray paint?
I think the ones intended for plastic will work right?

[Eddie6th]

Re: For the car paint experts

Well,my paint was resprayed with the original color as I did this part at the bodyshop.
Before you apply any paint,it's very difficult to see how correct your work is. When looking at filler it can be difficult to see sanding marks aswell. They will show up when paint is applied.
Here's the one I did on my car.I had to make a cutaway or the exhaust could not be applied....If you imagine,where the opening is,was full. There are some errors. I made it too narrow and I could have finished it off better.




One other option you might have,which will save you doing any work on your trim,is to simply change the rubber exhaust supports and putting longer ones on,which will drop your exhaust slightly...The only problem is that your car is low down,so bashing your exhaust off of a road bump might be a problem?

[Boba]

Re: For the car paint experts

Well,my paint was resprayed with the original color as I did this part at the bodyshop.
Before you apply any paint,it's very difficult to see how correct your work is. When looking at filler it can be difficult to see sanding marks aswell. They will show up when paint is applied.
Here's the one I did on my car.I had to make a cutaway or the exhaust could not be applied....If you imagine,where the opening is,was full. There are some errors. I made it too narrow and I could have finished it off better.




One other option you might have,which will save you doing any work on your trim,is to simply change the rubber exhaust supports and putting longer ones on,which will drop your exhaust slightly...The only problem is that your car is low down,so bashing your exhaust off of a road bump might be a problem?

I tried that as well as going to a muffler shop to ask for piping modifications. Because of how the GReddy exhaust is designed and the excessive components underneath the vehicle, it's not going to fit at all. If I had to lower the tip, then I'd have to lower it a good 4 inches to get it below the bumper.

Also what's a good grit sand paper to use? I'm thinking 900 grit. Should I go narrower?