A friend who shows me he has principle and yet should I trust him now?

If he's asking to change days for one week, and it's not inconvenient for you to do so, then change days for one week. If he starts to frequently ask for schedule changes on short notice, then you have to choose between whether you'd rather change your schedule on short notice OR skip the weekly dinner for that week.

You mention that your friend has a busy schedule. What is your own schedule like? If it's very flexible, then why not accommodate your friends as well as you conveniently can? But if changing from day to day is a problem for you, let your friend know that it's important to you to have a settled day for your weekly dinners.

Don't deprive yourself of the pleasure of these weekly dinners. And don't sabotage your pleasure in the dinners by dwelling on petty thoughts like "Who does he like better, his bicycling friends of me?" It doesn't matter whether you his #2 priority, his #7 priority, or his #83 priority. What matters is that you enjoy having dinner with him.

If you were "just a spare" he'd have cancelled without rescheduling. If you're free on Tues... go have dinner! If you're not, tell him you'll see him next week.

i also think u re a spare tire. tell him u re busy, grow a pair