Shimano left shifter ST-5800 shifting between LOW and HIGH TRIM

Question

After removing the shift cables on my left shifter, I was playing around with the trim positions and noticed a weird behavior.

If I start from the HIGH position, I can press the inner lever three distinct times to shift into HIGH TRIM, LOW, and LOW TRIM. This makes sense to me.

However, If I start from LOW TRIM, I can only press the outer lever twice. The first press will go from LOW TRIM to LOW. The second shift always double clicks and goes from LOW directly to HIGH, skipping HIGH TRIM. Is this normal? Or are my shifters busted?

Answer 1

That's normal behavior with Shimano STIs since you want a solid and reliable shift onto the large chainring, jumping to trim position first would affect that rather negatively, in most cases you are probably already further down the cassette so that high trim isn't needed to avoid the chain touching the front derailleur.

If you shift up from small-large, you just need to quickly trim once afterwards, but in real-life riding, I always shift a few cogs up on the rear first and never need trim in that scenario, anyway.

Actually, I think this is indicated by the graphic above: A full click jumps to the large boxes and then you have another click into trim. I didn't know that the innermost position is the trim but it makes sense.