Most people who ride bicycles for pleasure do not ride until the warm weather of spring and summery arrives.
Conclusion (probably = opinion)
It's probably more effective to advertise bicycles earlier in the year than the warm parts of spring / summer.
Evidence
Most bikes are bought in the spring, but by the time they are ready to buy, they have already decided what brand and model they're going to purchase.
By then it's too late to change their minds (mostly).
Evaluate
On Main Conclusion and Role, we expect them to try to hide the conclusion the vast majority of the time by either making it the very First Claim or making it some sort of Rebuttal / Pivot.
Is the first claim in this paragraph an opinion from our author? No, it sounds more like a statistical fact about pleasure bikers.
Is the second claim, the one after the "But, Yet, However" pivot an opinion from our author?
Yes! It has the opinion indicator probably in it, and it sounds like it's offering some advice. The argument goes on to support this advice by saying,
Goal
If we correctly found the Main Conclusion, there's nothing left to it but to find an answer that matches the meaning of that claim.
We decided the Main Conclusion is the 2nd sentence, so we just want an answer that says .