Tumble bonuses? Do they grant AC?

[Razarr69_ns3]

If I have an item that gives +10 Tumble, would that equate to a 2 pt Dodge AC bonus? Or is it just actual earned ranks in Tumble that grant the Dodge bonus?

As a side not, if it is just ranks that count, why do so many people say:
"take your last tumbling class at 40 so you can max out tumble at 43"?
Kinda stupid if tumble AC bonuses are based on rank alone as you can get 40 (+8 AC bonus) in tumble at level 37. So people should say take your last tumbling level at 37 to max your tumble at 40 unless there are other class benefits that are more pressing than that AC boost.

[Baatazu_ns3]

Only your base tumble ranks add to ac, so yes, you would want to max it at 37th.

[cryodog2_ns3]

every 5 tumble adds 1ac so at 40 tumble you get 8ac. this is base tumble only

[Razarr69_ns3]

Thanks, just wanted to make double sure so I could build appropriately. (and not waste a feat getting Epic Skill Focus: Tumble)