There are lots of posts about how to do this, but I would test 1 and 2 hours after every meal to see how it affects.your bloods
If you intend to do energy drinks still I would test after those also, you may be surprised how much they hit you.
As a note how long does a 70km bike ride take you to do? I do quite allot of excersise and I don't do any carb loading, I do eat before now but I find something while Wheaty and carby gives me all the energy I need and it's a slower burn. Two shredded wheat is like 60g of.csrbs I think but it takes way longer to digest so I find it doesn't hit my bloods, if I drank 60g of carbs in sugary water I would see a big spike quickly.
With the Libre I get a constant read, and I'm scanning enough now not to miss any data haha
I normally do quite a lot of hills with the riding so not that fast, 70km / 1,000m vertical ascent takes me about 3 hours. I normally average about 22kmh. My last ride was 60km and I had about 60 grams of carbs (4 small Brazilian Cheese breads) and 1 gel and did just fine so think I've been really overdoing it and intend to cut down.
I had thought the exercise would burn it off but clearly I've been overdoing it.
So update on my BS levels today...
Breakfast: small dose of Cheddar
Lunch: Salmon / Tuna / Pesto and a Lemon squeeze
Dinner: Steak with avocado & cream fraiche
My sensor came online at 1030 this morning and my BS has been 6-7.8 and is now dropping to 4.6 after dinner.