More info about the ELO Rating System can be found here, only a teams wins/losses/draws are used when calculating your ratings, a large/small score margin has no effect currently.
A K-Index of 64 is used, starting rating of 1400 and score distribution of 400 is used.
You can challenge teams that are within 250 of your ELO Rating above or below.
Once your team gets to the top 10, you are only able to challenge teams that are in the top 30 places (as well as within 250 rating).
If a team declines or fails to accept a match they do not lose any ELO.
If you win a defending match you are protected for 30m (no one will be able to challenge you).
If you win a challenging match you are protected for 15m (no one will be able to challenge you).
If you lose a defending match you are vulnerable for 30m (you will be unable to challenge).
If you lose a challenging match you are vulnerable for 30m (you will be unable to challenge).
You cannot play the same team twice in a row.
Time given to accept a match: 24h
Team members required to challenge: 5
Players are allowed to be in 1 team at a time