Esteban Gutierrez has revealed that Sauber are having problems with the new brake-by-wire system in their 2014 car.
Sauber have struggled with the new system - which adjusts brake balance electronically in order to facilitate the effective harvesting of energy by the recovery systems - throughout pre-season, which is the reason behind Adrian Sutil's off-track incidents at Jerez and Sakhir.
"As a driver it's all based on the feeling because obviously you need to communicate with the team what you feel and what you need to be more confident and to get more performance from the car," Gutierrez told crash.net when asked about the car's brake balance.
"This is affecting the car balance as well so you need to relate everything to speak about the car balance. You can't just speak purely about the car balance; when you have all these issues on the braking you need to solve the braking issues and then go on to the next step."
However, with less than three weeks before the start of the season and only one pre-season testing session left, Sauber are treating the problem as a priority, the Mexican added.
"It's more complex because you have a system which is working and trying to compensate for something from the recovery system and it has torque variations as well to make in relation to the downshifts. So this is something that we need to put together and make progressive," he continued.
"We are making progress but we have this as a priority at the moment."