I never bookmarked the actual thread, but I keep this in my server.cfg for reference when I run a dev or game server.
// TIP for setting your rates. This tip is coming from a thread in www.steampowered.com forum. We can't guarantee if it really works.
// In case of LAG issue you can change the following lines.
//
// Maximum amount of bandwidth clients can use (0=unlimited, max=20000)
// Formula : sv_maxrate = bandwidth X 125 / number_of_slots
// Example :
// Assumptions :
// . upload bandwidth = 768 kbps and download = 10mbps. Take the lowest value (768).
// . slots = 10
// So : sv_maxrate = 768 * 125 / 10 = 9600
// Minimum amount of bandwidth clients can use (0=unlimited, 4000=good to keep dialup gamers off the server)
// Example : we want unlimited
// sv_minrate 0
//
// Maximum updates per second that the server will allow. Increasing this value will take more cpu power, 100 is max.
// Formula : sv_maxupdaterate = sv_maxrate / 300
// Example : with same assumptions than above.
// sv_maxupdaterate = 9600 / 300 = 32
Now, needless to say, that thread was for a Counter Strike Source server.
CSS in it's default usage is much less lag capable than Gmod. Though Gmod has come a long way in it's day towards less lag, many addons and just the fact the user can spawn lots of props not intended for MP use can drag down rates.
Experiment with your settings.
I have nothing on cmd rates, sorry.