EMB ERJ 145 ER/LR
Flight Crew Air Transport Pilot (ATP)
Situational Awareness
Aircraft Equipment Problem Less Severe
Flight Crew Rejected Takeoff; Flight Crew FLC complied w / Automation / Advisory
Aircraft; Environment - Non Weather Related
CA (Captain) and I were set up to takeoff. I ran the before takeoff flow and once I pressed the TAKEOFF CONFIG button we got the aural warning takeoff trim. I looked at the trim and it was set to 8 and in the green band so I bumped the trim down a little bit and pressed the TAKEOFF CONFIG button again. This time we got the takeoff okay aural warning. After running the before takeoff checklist tower clears us for takeoff. Shortly after setting the thrust we get the NO TAKEOFF CONFIG EICAS message. We abort the takeoff and I let ATC know what's going on. They instruct us to turn off the runway and go to the pad next to the runway. Once we get there my CA and I pull out the QRH and do the procedure for NO TAKEOFF CONFIG the TAKEOFF CONFIG button and got takeoff okay aural warning as we did before. We run the full before takeoff checklist again and ATC once again gives us clearance to takeoff. This time no message appeared on the EICAS and we headed to our filed destination. The threat was this event happened in a critical phase of flight which was during takeoff. The error was that I didn't put the carrot on the trim further down to make sure the computer didn't see a discrepancy during takeoff. The undesired aircraft state was the trim showed 8 and in the green band but the carrot was towards the top of the green band and was hanging on the edge of being within tolerances. We probably hit a bump causing the trim to be out of range and putting the aircraft in an undesired aircraft state.
An EMB-145 crew reported receiving a TAKEOFF CONFIG  alert as the takeoff roll began. The crew rejected and determined the stabilizer trim; set at the green band edge; probably moved slightly as the aircraft accelerated over a bump on the runway.