I'm sure I'm not doing something correctly. I've searched here for an answer and no solutions have worked for me. I was use to the stock firmware making a gigabit connection for me, so I'm at a loss here when it comes to having to setup some of the more advanced options. Other than this issue, killer job Shibby and many thanks!!!!
I also have same problem: New ASUS RT-AC66R, last TomatoUSB firmware (115-AIO).
WiFi 5 Ghz shows three options to select: 20 Mhz, 40 Mhz, 80 Mhz. If you select 20 or 40, then you will have the options to choose specific channel after pressing "scan" button, but if you select 80 Mhz, the combo box shows "Auto" and even after scanning, there is no list of available channels to select. If you save 80 Mhz + Auto, and reboot (or not reboot), TomatoUSB automatically switch to 20 Mhz, so I have selected 40 Mhz and select one of the available channels to have at least something. All of us who have experience this problem needs to report, so Michael (developer of TomatoUSB in Poland) will fix it.
I was trying to apply workaround suggested by others, but no luck.
It's needs to be fixed. Ready to pay by PayPal $20 to convince Michael to fix it ASAP. Who will join ?
Original post copied from "bug report" system in tomatoTOCHKAgroovTOCHKApl :
"…. Settings for the 5GHz channel width are 20MHz, 40MHz, and 80MHz, but upon setting it to 80MHz the channel reports it is set to 20MHz. Wireless Network Mode only has options for "Auto", "A Only", and "N Only".
I very quickly switched between all three available firmware and they all display such behavior.
When the 5GHz channel is set to 80MHz in the official Asus firmware and then flashed with Tomato Shibby, the channel reports everything is good and running at a rate of 1300Mbps…. "
I was trying this trick couple of times - no luck :-(