Pictured above is the front bumper from a model 500 Roomba.  The discussion about why your 500 Roomba is going slower than normal can also be applied to a 600 and 700 model Roomba as well.  The bumper is resting upon a sensor array that normally sits just behind the front bumper and the sensors look out through the dark opaque plastic lenses.  These sensors perform a very useful function by slowing down the forward speed when an object is detected in front of the robots bumper.  Over time the sensors that are wrapped around the inside of the front bumper become blocked with dust and other debris.  When that happens the sensors send a signal to the Micro Control Unit to slow down the robot.  The problem then becomes apparent since the robot continues to run at half speed ALL the time, not just when approaching an object.  The fix is to flip the robot upsidedown, remove the (10) phillips head screws attached to the bumper retainer, lift it away, raise the main bumper up and away from the robot body and then wipe the debris off of the sensor array.  Now replace the bumper, install the (10) screws into the bumper retainer, flip it back over and you're good to go. 

The new Mod that is offered consists of a front bumper that has had the three opaque plastic lenses seperated from the bumper body, then two 2-56 X 1/4 inch stainless steel phillips head screws are installed into two 2-56 brass threaded inserts on each of the three plastic lenses.

Pictured here is the finished Mod.  Each of the three lenses has been re-attached to the bumper using the two phillips head screws that were installed during the mod process.  Now it becomes just a little easier to access and clean the Light Touch sensors since all you do is remove the three lenses, wipe the sensors, replace the lenses and you're on your way.  You can order this bumper mod for just $40 plus $8 USPS shipping.