[FrankJ]

Was the robot ever able to climb the ramp? If this is new then look for something wrong. Cims are very reliable, but they can be burned at by extended use at high loads. (Which is beyond their design spec)

Otherwise it sounds like you do not have enough torque. If adding motors in not an option, you can lower the drive ratio by changing the chain sprockets on the wheels. You will lose speed but gain acceleration, turning & pushing ability along with climbing ability. Sprockets are available from AndyMark.

Our locomotion chassis is geared for about 10 ft/s & has no problem climbing the bridge. (long chassis, 6 wheel drive, Simple boxes, 8 in wheels, 1 cim per side.)