My experience is that there is not a lag on the way down, but there is a lag of at least 15 minutes once you have dropped below 65.
I have multiple strategies for the food that I eat before a ride, and like many strategies, some work better than others, some aren't much more than seat of the pants guessing.
The first thing I do is drop my basal rate drastically. I typically run @ only 10% of my regular rate, and I like to get this going at least 1 hour before riding, frequently 2 hours before. I always do this, but I arrived at it after lots of trial and error using everything between 50% down to 0%..
Next, I like to eat something with some protein along with some carbs too - 2-3 eggs with cheese, a glass of milk, whole wheat bread or an english muffin. I will bolus at no more than 50% of my regular bolus, plus I will try and eat in less than 15 minutes after bolusing.
I always carry glucose tabs, at least two small boxes of raisins (22g carb, each), and at least two Clif Bars (41g carb, each). When I start dropping, I will normally start by grabbing 2-3 glucose tabs, but it all depends on how severely I am dropping, where I am on my ride, etc.
This past Sunday was a great example - I did everything described above, only to see my BG under 65 about 20 minutes into the ride - very weird! I ate two glucose tabs and a Clif Bar. I took about a 5 minute break from riding and started again because I really wasn't feeling the low. My BG bottomed out around 53 and then started climbing back up. After about 2.5 hours into the ride, I was comfortably running in the 130 range, with some hills to climb as I turned towards home. When I finished a 4.5 hour ride, I was just under 100, with a slight downward trend. I went inside and drank a glass of milk (12g carb) and in about 30 minutes I was flat-lining in the mid-80s.
On other rides, I have really loaded up on carbs along with a good variety of protein and fat. Think banana, yogurt, peanut butter, bagel and milk all in one meal. Sometimes this runs my pre-ride BG to well over 200, but the riding brings it down. Last summer, when riding across the USA, I always carried some trail mix and I would have a handful about every hour as a kind of glucose basal rate.
Yes, I did always have my finger-stick meter with me, but these days I find my experience in reading the CGM "tea-leaves" is all I need.
I will also say that I have become very tolerant of lows, so I don't often get the "light-bulb flash-in-the-eyes" effect that @DrBB describes. If you're worried about that and wobbling around/literally crashing, I would try and run a little high during a ride.
I would experiment and get back out there. When I was on the dreaded NPH protocol, there was no way for me to safely ride, but pumping coupled with the near real time CGM feedback has enabled me to go places I never dreamed of.