How to tub out your rear fenders

Old 07-04-2010, 02:51 AM
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Default How to tub out your rear fenders

Credit given where credit due...I did this project after seeing "Lightfoot"'s rig, but mine is a little different..thanks for inspiration buddy

I started by bobbing by rear fenders(if you don't know what I'm talking about, it means cutting off the part below the rear taillight, there lots of write-ups on doing this). I knew I was going to bigger tires and I never liked how restrictive the rear well openings are, even with a "cut and fold". Heres how you can tap your rear fenders for all the room they can muster

This does involve pulling all the plastic trim in the rear cargo area. It will not fit back in place when this is done

This also involves major cutting and welding on the unibody, including cutting off pinch seams, but this does work and to my knowledge is safe

-Time needed - 8-10hrs per side, having never done it before
-Difficulty - Hard. Lots of cutting and even more welding of very thin metal 24ga, maybe thinner..good welding skill required, not a newbie project
-If your looking for more clearance and don't want to go higher, this is your project.

This write-up is being conducted on a 1990 XJ 4-door

What tools your gonna need:
1. Plasma cutter and/or lots of cut-off wheels
2. Welder, MIG or TIG recommended
2. Good angle grinder with a couple grinding discs and a couple twist knot cup brushes
3. Fan to ventilate smoke out of your rig
4. Tools to pull the rear seat out as well as seat belts, all trim and carpet from the cargo area(if your taking this project on, pulling the plastic shouldn't be difficult at all)
5. Lay out tools(sharpies, straight edges, torpedo level, speed square, measuring tape)
6. Piece of poster or cardboard to make templates
7. Jack stands and a jack
8. Lug wrench
9. Fire Extinguisher

Materials your gonna need:
1. 2 pieces of 12ga steel 7x60"
2. 2 pieces of 12ga steel *x15"(the * number determines how far back you want to stretch your wheel wells) I used 4x15" to gain 4" in my wells, but anything under that will work too
3. comsumables for your welder and plasma cutter, I ran out of sheilding gas half way through..not fun.
4. Can of spray paint or some bed liner to protect your new work

Crank up the tunes and lets get started!

First thing you need to do is remove all the trim inside your Jeep from the center pillar(between the front and rear doors) back. Almost none of it that touches the floor will fit back in, but if your planning on putting bed liner on the inside this is no problem.
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Remove the wire harness and rear washer fluid line from the drivers side(the thing in my hand is from a stock tow package)
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Note: Make sure the washer line is up past the tank of it will siphon itself dry and make a nice mess everywhere I ran it out the drivers window and hooked it on the roof rack.

Now that the cargo area is cleaned out, you can start cleaning your joints for cutting and welding
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Now move outside and remove the stock fender flares down to sheet metal
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Next clean up the inside of the wheel well with your wire wheel, get the entire pinch seam in the center of the well really clean, cause that where your welding later on
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Now grind off the paint around the area of the cut on the outside(just eyeball for now)
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Now gather up your lay out tools and you poster board. What I did, was I figured out where the center cut was going to be and worked from there. Theres a piece of sheet metal above he well that ends right in the middle. Its were the back seat attaches to the body. I then picked a couple of points on the profile of the well to take measurements. We're taking these measurements to transfer to the poster board so we get the same shape outside the jeep as inside. This picture will help
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So the way this works is at center the height is 9 3/4". 2" back from center the well is still 9 3/4". 6" from center(or 4" from the last mark) the height is at 9" even. 10" from center (or 4" from the last mark) the height is 6 3/4". At 15 1/4" from center is the end of the wheel well. Heres what it looks like on paper
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Connect the dots and you can see where this is going
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Now cut it out and see how it fits
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Get it as close as you can, it will keep you from beating your kids..Joking..joking
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To get proper orientation front to back, you'll need to know where the center pich seam ends, but you'll need to know on the outside of the Jeep. Run a square line from the back of the wheel well at the center pinch seam straight out, with a square line going straight out you will have the position for no-stretch(at this location your wells would extend straight out from the center pinch seam. Speed square works great for this, just rest the square on the pinch seam that drops down, right behind the wheel wells. Where the squares edge comes out past the body line, make a mark on the flared edge. sorry no pics.

This step isn't %100 necessary. Now that you got a good template go outside and hold it up, lining the bottom up with the flared edge thats even with the floor in the cargo area. I drew this one to show what I would get with no stretching of the fenders.
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From your no-stretch mark, measure back you stretch distance. In my case it was 4". Realign your template and make a mark.
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The line willn't go all the way across your fender, so theres a little creative drawing that needs to be done. I just continued the line coming from the rear door and let it intersect a "level line"(see below about "level lines") This was on the drivers side
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Note: If you want to make a "level" line on your jeep, do not use a level, instead measure off the body lines or pin stripping

Hop back inside and draw a cut line up the center of the wheel well. This is a little tricky considering your using(i was using) and straight edge to mark a round hole. If in doubt, run your fill strips(12ga 4"x15") a little wide to compensate for slop
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Old 07-04-2010, 02:59 AM
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Beer thrity...Lets take a 5-er and look at what we're doing. Heres a plum line from the no-stretch mark looking down, which just touched my 31's
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Heres a view from the front of the well...not much room..couple inches
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Heres a 4" stretch with a tub out in the back
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And the front
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I'm ending up with 4" clearance on the front and the back and 10 1/4" up travel on 31's..not bad

Ok breaks over, put your rig up on stands and pull the tires. Now lets start cutting! I started by cutting the center center line inside the jeep and around to the back of the well. I then continued back 4", which will line up with the mark I made on the outside of the Jeep(remember?). Now go outside and cut the center pinch seam(inside the well) on the outside part of the well(outside panel)..stay to the outside of the pinch seam, only exceptions are when your cutting the center line inside the Jeep, and when your cutting the rear of the well...the cut that goes straight out! You should now have this piece!!
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Continue cutting the rest out from the outside of your Jeep till you have this. In this first picture I already cut the floor out to make room for the inner well to go back. Not the halved drain hole
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At this point I wouldn't drive the jeep and avoid climbing inside, considering you just removed a fairly large piece of sheet metal, you could tweek something.

Where the well meets the rocker panel, your faced with a decision. Cut around it and leave a 1 1/2 jagged edge in your well or cut the thing off and box the end in with 12ga. I did the later
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Ground smooth for our new tubs
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Take some time now to remove any slag, paint or more importantly the rubber stuff Jeep put around the seams, I think its a anti rattle thing, but it loves to contaminate welds...I know. I found a grinding disc work awesome till it loaded up. Grinding on some scrap will clean it up again though.

Now take the inner well piece you saved and hold the back of it even with the cut in back and try your best to align the side with the previous position of the well. The idea here is to use the radius on the well to make a cut line on the floor of the cargo area 4" back from its previous postion. Cut this little piece out and TACK in the inner well piece

Heres the 7x60 12ga. bent roughly into shape, once again, get it as close as you can! you willn't be able to bend this stuff when its tacked in!
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Note: I found out quick this peice of metal gets heavy when your trying to weld it so I used a floor jack and a piece of wood to hold it up

Get it tacked up and see how the inner fender(the piece you saved) fits if everything is looking good take the 4x15" piece and prebend it to fill the new slot. If everthing fits good weld it up, being careful to not put too much heat into one area or burn through Heres what you should have
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To help beef up the end of the rocker panel I cut some holes with the plasma cutter in the tub for some plug welds into the 12ga. cap
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This part here gave me trouble, so I just hammered this lip down and welded it up
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Finish welding everything up and do the same to the other side. Everything will go easier and quicker,but......things do get a little invloved on the drivers side because at 4" stretch the wheel well will go into the gas tank tunnel by about 1/4". Its not big, but the jeep knows how to use it!

When your cutting near the tunnel either pull you gas tank out or put a wet rag over the filler/vent hoses. I used a wet rag and an old welding coat over that.

Heres whats gonna end up like before the floor inside is cut
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Old 07-04-2010, 03:04 AM
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Its close! Heres the driverside inner well. I cut about 3/8" off so that it would mate up to the tunnel nicely
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Once you have that figured out your golden, weld everything up. I angled the edges a bit at the front and rear and if this was a finish edge, I'd weld a piece of bent pipe or even a piece of 1/2 rod to the outside edge. Mine however are going to be covered by another future project. Till then, I threw some hurculiner at it.
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All in all I had a fun time with this one..Good luck!!
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