Cisco Aironet 1700 Deployment Manual page 63

Figure 85 Example of a 2-ss Client Bonded at 80 MHz
Notice that the software reports channel is 36 (that is where the channel bonding starts). On a spectrum analyzer, we see that
the actual channels in use are 36, 40, 44, and 48.
Figure 86 Example of a Bonded 80 MHz Channel
For clients to link at 80 MHz, you have to set the channel width to 80 MHz on the AP.
Note
Cisco Aironet Series 1700/2700/3700 Access Point Deployment Guide
Cisco Aironet Series 3700 Access Point