My 1980 450SL has the same tear on both sides. Much worse than yours. It seems to be where this area sits when folded against the edge of the support arms. I think my convertible top is the original and is in good condition other than this with clear windows. I didn't want the expense or work needed to replace the top. I stitched up mine several years ago. Still intact.

 

Yes those tears are usual failures of an aged top.
I patched mine with pieces of matching canvas extending the height of the window, glued to the outside with contact cement. I used no interior patch.
If you are careful not to get cement on the top beyond the patch boundaries, it will be difficult for a blind man on a fast horse to notice your repair. Actually the result was serviceable if not pretty
and got me through another few months of infrequent use.
But accept it: your top is done; splits above the side windows come next. DIY top replacement is an interesting project. There is a long thread by @nobby on the subject.

 

Yes those tears are usual failures of an aged top.
I patched mine with pieces of matching canvas extending the height of the window, glued to the outside with contact cement. I used no interior patch.
If you are careful not to get cement on the top beyond the patch boundaries, it will be difficult for a blind man on a fast horse to notice your repair. Actually the result was serviceable if not pretty
and got me through another few months of infrequent use.
But accept it: your top is done; splits above the side windows come next. DIY top replacement is an interesting project. There is a long thread by @nobby on the subject.

Thank you... the outside patch might be the key.. Mine is OEM top, and so is the one in photo. In both cases, it appears that the original owners never used the soft top so the overall canvas looks great --but with regular usage the brittle old fabric finds a place to tear in these areas, which is probably exacerbated by the window panels on both sides.. I was about to replace mine, but thought I might try to get through another year with a patch

 

^--- what @dugald said. I too tried patching some scrap pieces of canvas. Look pretty good for a while to a "blind man on a fast horse" too Look also for some splitting to occur on the top at the drivers and passengers windows.

 

No experience with convertible tops but I mend both vinyl and canvas tears with a sort of figure 8 stitch and heavy thread used for whipping lines on my boat. Works great and holds up a long time. You basically stitch about 3/8" outside tear coming from inside out. Run thread through the tear and come out again from other side. The stitch forms a figure 8 that supports the fabric from both sides and draws the fabric together at tear. I'm sure any heavy duty thread would work but the whipping is extremely durable. You could probably run some seam sealer from a camping store over entire repair to water proof it. Should hold you over until you replace top. Good luck.

 

I did a post about 11 years ago about a temp fix...here's the link. IIRC it lasted for a year or two.

Temporary fix for ripped convertible top

 

There is a product called Tenacious Tape that is used to repair tents. I put strips of this tape on the back of my new top when I got it on all the areas where the metal frame/cables rub the top. I also fixed some tears with it in the previous top, I think it worked well, but can't remember.

Edit: Now I remember, I had some slash cuts in the top from the previous owner, I cut a strip off a patch, rounded the corners, and stuck it on the outside of the tear. Held up well and blended ok with my black top. It never came off, but I replaced the top after a year or two. You might be able to slide the patch in between the exterior canvas and the liner and hide it, but the tear line will show.

 

There is a product called Tenacious Tape that is used to repair tents.

T Tape looks like pretty good stuff. I would have tried it had I known about it 10 years ago...thanks for posting about it.

 

My original top developed tears (I did too ?? ) I did a short term repair using adhesive backed sail repair fabric. (We were in sail business, so it was what I had (Stick-Back Dacron)). This is something we always carried with us when sailing. We could do a temporary repair and sail would soon be back up. Sails come under a lot of stress when in use, so this was good stuff. But tears always later had to be properly repaired.

The problem I found for top, was that the top is made of a a coarse weave canvas while sails (and tents) are usually quite fine weave. The adhesion as a result, was not as good in this application. It did work for a while.

In retrospect, I think it might have been better to use fabric strips similar to the top canvas and glue it on using the kind of adhesive we use when installing new tops. Hand sewing it as well would help.

 

Hand sewing and tapes may work. I prefer a rubber cement product called BARGE, I recommend the older version not toluene-free. We used it explicitly in prosthetics and orthotics, when used properly it will bond dissimilar materials forever and never harden.