Convertible Inner Rocker Repair

How to repair a convertible inner rocker the cheap and easy way. This is due to a door that would not close properly and I later found the reason being the rear inner rocker had deteriorated and car was folding in half with top down. With mega hours into alignment and paint chips I discovered the welding job on my rear inner rockers was not quite up to par.

This looks good you can see a thin scab has been added to this inner. While it looks good its too thin being .040 material and not correct .090” material. Furthermore it is completely rotten underneathe. The function of the rocker and especially the inner is to provide structural integrity by tying the front frame rails into the rear frame rails. Connecting the frame rails prevents the car from twisting when cornering or folding in half when opening doors.

Most of the repairs I have seen done to this area are scabs over top of the rusted component offering no structural integrity or improvement aside from maybe hiding the mess.

This article is written to do on a complete car. The proper way to do this job is to completely remove the interior and get serious about fabricating the missing pieces and weld them into the existing originals whenever possible.

Required tools



   Ear Plugs




   MIG welding equipment

   Disc Grinder


   Screwdrivers wrenches and the usual mechanics’ tools as well as some level of competence and knowledge and use of grinder’s welder’s sheet metal fabrication techniques or a friend w/welder who likes to do jobs like this on a weekend.



Notice half the inner rocker is missing. We see outer and vertical rocker but inner is missing from rust. The inner rocker and all rockers in convertibles are .090” material and are structural components. The point where the leaf spring bolts is supposed to be attached as well to the inner rocker as well as frame rails and rear torque box/floor. You can see that part is long gone from this example.


As the rusted area measures 4” x 2.25” there are several ways to fill this void. One is to bend a piece of satin .090 material into an L and weld it in. I was doing this on a Saturday w/help from a friend so I had to shop at a retail outlet for steel and coincidently was thinking of using some 2x4 rectangular box material already made up I could slide into hole.

What I got was 7’ of 1”x2” rectangular box material (thin wall) and welded all the pieces together to form a stronger than original boxed replacement insert.


Note the different lengths of steel used. The inner rocker tapers at the 16” mark from rear and seat belt bolt hole is about 24” in from rear. The longer outer (closer to center) pieces can be up to~30” in length with differential in place and longer again if rear end is out so drum/axle housing does not interfere w/inserting insert.


Once the end is open and center tab bent away the piece can be slid into rocker. The piece extends to under the door several inches. Note jack stand is below frame rail beside rear torque box and behind Bruce’s hand. Probly best to have both sides off ground letting rear hang expanding the gap on top of door at jamb. You can achieve gain by loosening off the rear shock allowing drop (just enough) for insert to go in. “Just” enough space can also be achieved by loosening the backing plate and axle flange Once its slid in all way there is still ¼” to fill. I recommend 4x4 3/16 angle iron if possible cut down to fill side and underside gap adding even more strength.


There is a tab that locates to where the L bracket is in pic that needs to be secure to rocker assembly. The angle shows the red door pulls I made, lol Note in pic that the small piece of L iron I am using in pic fits against the piece we made and installed earlier and the tab for spring perch locates and is welded to.


The 2x4 piece we made and installed fits exactly to where the original was bent and welded. Be sure to at least undo fuel line brackets and move fuel line out of way to do this job. As well remove back seat door sill interior ¼ panel and any other flammable materials and cloak the entire interior with some non flammable protection against sparks making holes in leather, vinyl, plastic or glass.


A .090” L would work here but I think the four rectangles forming cells is stronger. In my case however as I did not have the material so we used a flat bar 2” x 4” and slid it in beside the four piece box welding the tab for perch and to box.


Center rocker was bent back to cover the ends partially and welded up as well a triangular shaped piece has rotted and required replacement. I consider this a near rust free example of a Canada Cat w/86,000 original.


Next we had to secure the box further down inside rocker so holes were drilled in top and side of rocker from rear seat area and holes were welded thru to new piece. In theory this stops the car from folding fwd and pinching top of doors in door jambs.



This job took a dozen hours but figuring it all out was time consuming as is prep if you do a good job. Much of this job was backyard standard done without sand blaster plasma cutter or spray equipment. The grinder broke in process so none of the welds have been ground nor were we able to gain advantage of completely clean material everywhere. The job requires grinding of the welds some painting of parts and seam sealing as well as all the fun we had already. Not shown is end cap put back in. Finished up at midnight out in drive so pic takin was compromised


1. I would consider using the 2x4 flat bar on inner center (instead of out at tab) as the inner centers are also rotten. Pix here show good inner center due to previous scabbing of material.

2. I prefer to use satin material that does not rust again. The mild steel shown here will rust again but probly not in my lifetime enough for me to have put any paint inside of them. Theory being as it rusts and swells makes the rear box tighter

3. I would go as long as possible on the inner pieces. We are limited to ~16” at angle down of inner inside rear seating area and I think 24” for seat belt hole for sliding a box into but with rear end in place you have to angle the piece in and limits to about 30” maximum (more can be obtained if rear end is not present) however I feel its enough to get a hold on a sagging convertible chassis.