Read All the comments u will get the answer. hash4u give u the solution. take the disk brake to KHARADIA. he will tool it till the disks get smoother, so u will not feel bumps. this happens when person is using more brakes , so that pads get hotter than their limits, suddenly if u passes through cold water, the disk get deformed by this sudden change of temperature. this deformity feels in form of bumps buring braking.