Failed, deloaded, failed
I really suck at chins. I'm doing a modified strong lifts 5x5. For chins instead of amrap i did a set number of reps then increase by 1 next session. i did that till I got sick of it, stuck at about 8 reps then went back to 3 sets of 5 and added 5 pounds each time. I failed at 20 lbs 3 times. Dropped it back to 15 and failed again.
I'm thinking about redoing something that worked for me when I could barely do 5 reps with body weight. Do 10 singles with a given weight, next time do 10 doubles etc until you can do ten x 5. It worked but it was really time consuming.
Is there anything else I could try
I haven't tried it, but there seem to be some good results with the 1/2 + 1 method. Explained here by Sean Hyson
Grease the groove (Pavel's system of doing low-rep sets, for instance half your maximum, throughout the day) worked OK for me. I'm trying Coach Sommer's approach of holds at the top and bottom, plus negatives, in order to ensure soft tissue health and avoid tendonitis.
Switching from 8 reps to 5-plus-weight seems like too little volume to me. I wouldn't add weight until I'm hitting 12 unweighted at an absolute minimum. I prefer 3 sets of 15 before adding weight. When I switched to weighted, I actually got weaker due to reduced volume.
Do the 3x5 pullups but then do 3x10 body rows. Super set the muscle group with an easier exercise and reap benefits for the main exercise.
what do you mean by body rows?
Body rows are the inverse of a bench press, or a push-up.
They can be done with varying degrees of difficulty by varying your foot position, but the essence is that you pull yourself up to your hands in the horizontal plane. (Chin-ups are in the vertical plane.)
I do them with rings, and my feet up so that my body is horizontal. My girlfriend isn't that strong yet, so she keeps her feet on the ground so that she's at a 45 degree angle or so from the ground. Either way, you pull yourself up so your grip on the rings goes into your armpit.
Like this: http://eastsidesc.com/2011/06/21/ring-rows/
They're a fine way for people to work up to pull-ups, or to supplement pull-ups with a similar movement in a different plane that uses slightly different muscles (or the same muscles, slightly differently).