Remove factory paint from inside of panel?

More of an art than a science - discuss metalworking and welding here.



Non-Lurker
Posts: 3
Joined: Sat Jun 11, 2022 3:01 am

Country:
New Zealand
PostPosted: Sat Jun 11, 2022 3:19 am
Hi,

I am wondering what thoughts more people might have regarding this.

The government body in charge of vehicle modification safety/certification for my country has posted the following image as an acceptable method of raising rear wheel arches:

Image


I have a question regarding the factory applied (97 Nissan) inner covering on the rear skin. Do people usually remove it where possible? How bad is it to leave it especially as some places are unreachable?

A test piece ended up with the rear/inner looking like this:

Image


I appreciate any insight. Thanks!



Top Contributor
Posts: 6217
Joined: Tue Sep 16, 2008 1:17 pm
Location: Pahrump NV.
Country:
USA
PostPosted: Sun Jun 12, 2022 10:30 pm
I am not sure what you mean?
Are you saying you want to remove the inner wheel well? And leave it that way?

This web sight hosts pics so they can be zoomed in on no charge, Imigur is not a very good image host cant zoom in on pics.

What are you using for a welder?
Dennis B.
A&P Mechanic, FCC General radio Telephone Operator
Line Maintenance A&P Mechanic and MOC Tech specialist.

User avatar

Top Contributor
Posts: 2762
Joined: Sun Dec 16, 2012 4:46 am
Location: Canberra
Country:
Australia
PostPosted: Mon Jun 13, 2022 5:11 am
No Dennis, the photo is not his work, it's an example posted by the NZ Road Transport Authority (or whatever their name is).

Speaking as someone who's done repairs on lots of wheel arches and modifications on quite a few I'd say that there's a lot more to be considered than just a picture of the outside of a wheel arch that's been increased in size by taking a section out and welding the original back on, with about a zillion cuts to accommodate the diameter change. :shocked:

Firstly, this is a rear wheel arch. Usually there is an inner guard that generally is spot welded on to the flange. If you cut the outer then what do you do with the inner? It would have to be attached to the outer and that means quite a bit of beating to create a new flange that can be spot welded to the outer, which, by the way, will now be a different shape due to increased arch radius. Without taking off the quarter this will be a pig of a job. Possible, but difficult and not the way to do it properly. Best practice would be to remove the quarter. make the outer modification including a flange. Then, with access to the inner, create the shape you need so that the two flanges can be spot welded together.

Doing it this way also means that you have access to both sides of each panel, so welds can be properly ground and epoxied/primed/rustproofed. :wink:

I can't see what they've done with the flange in the photo - almost looks like it's no longer there. If that's the case then that's a pretty crappy way of doing it. That wheel arch would have no strength at all, bending if you even breathed on it. And I can't see any evidence of joining the inner to the outer either. Surely not - again would compromise strength and I'd be pretty sure that it would not pass engineering here in Australia. Even if covered up by a plastic wheel arch trim.

I know that NZ follow us in a lot of stuff like vehicle modifications and the National Standards. Nothing I've ever seen looks like this.

The other question I'd ask is why? There's a limit that you can lower the ride height by and that sometimes means that the tyres may contact the guard on full compression. Usually that's dealt with by just flaring the wheel arch a bit to get the clearance. You can do that with a baseball bat (no, I wouldn't do it with a cricket bat either, that would be sacrilege) or there are special tools that cost a lot to achieve the same result. Sometimes you may crack the paint, but better a bit of paintwork than having to pull off both guards and all the panel beating. What is it anyway to warrant even thinking about doing this? 200/240SX? Skyline?
Chris



Non-Lurker
Posts: 3
Joined: Sat Jun 11, 2022 3:01 am

Country:
New Zealand
PostPosted: Mon Jun 13, 2022 5:47 am
Hi Chris,

Thanks for your reply.

The rear wheel arch gets raised to fit a wider tire.

The example picture shows the end result. A segment is cut out of the quarter and then the inner skin stretched, sliced and overlapping the outer skin.

It can be done other, better ways (usually by removing and fabricating a new inner liner) but this is an approved method in NZ to re introduce strength to the rear arch. It's cheap, fast and works. It ends up covered by a wider arch so not visible.

My question is in regards to the heat affected area on the inside of the outer lining but I have come to the conclusion that it's not really a problem and I can scuff it where possible and recoat.

User avatar

Top Contributor
Posts: 2762
Joined: Sun Dec 16, 2012 4:46 am
Location: Canberra
Country:
Australia
PostPosted: Mon Jun 13, 2022 7:24 am
Ok, so at least I understand what the plan is.

So now you have 3 layers around the edge. Better than I thought was only one layer.

How much wider tyre? Don't you guys have similar limits to ours? So you can only go out (increase track) by about 25mm. That means that that edge is poised right over the tyre so has to be cut up high enough that tyre can't contact at full compression. Assume you're lowering at the same time so may not be much suspension movement left.

If the geometry works then all you can do is put some weld through primer on the inside of those panels, then weld it all up. After that there should be some kind of access hole somewhere (even if you have to make one) that you can feed a tube through and spray rustproofing wax all over the inside. Generally the factory dipped rustproofing is fairly good, so don't remove more than you have to, but some may get heat damaged from the welding. From the outside epoxy, prime and paint as much as you can see or spray. Sometimes a Schutz gun may work better to get into tight corners. Won't be a pretty finish but you just want coverage and protection if it's covered by a wheel arch mould.
Chris



Non-Lurker
Posts: 3
Joined: Sat Jun 11, 2022 3:01 am

Country:
New Zealand
PostPosted: Mon Jun 13, 2022 4:42 pm
Cheers.

You end up with 2 layers: the outer skin which has had an arc cut out (including the flange) and the inner skin folded over it. The standards call for a decent amount of metal deposited back into the arch through welding. The overarching guideline is that any strength that is removed must be re-instated.

In NZ you can go 25mm without certification (engineering in AU?) if you stay with the arch. Through certification you can go wider.

I do have some internal access, enough to coat afterwards, but not enough to fully remove the paint. I was concerned about the paint catching fire or chemically reacting in a bad way etc. but it seems pretty common to coat rear sides of patch panels with not only weld thru but also other epoxy primers.

User avatar

Top Contributor
Posts: 2762
Joined: Sun Dec 16, 2012 4:46 am
Location: Canberra
Country:
Australia
PostPosted: Mon Jun 13, 2022 6:04 pm
Understand.

The back of the panel is often a problem with modifications and even repairs since we can't dip it like the factory. That's why I like to give a good squirt of wax afterwards to try to seal it all up in there.

Sounds like a fun project. Post up some pics as you progress.
Chris

Return to Welding & Metal Fab

Who is online

Users browsing this forum: No registered users and 34 guests