I always preffered the A.e springs on the 501x as the car is quite heavy (was using ni-mh cells at the time though) used blue front and silver rear, since going to the 511 though the tamiya springs feel much better and I think give more corner grip on loose surfaces, especially indoor, with the A.E springs on the 511 it felt a little 'snappy' on the rear even using A.E green, the tamiya ones just have a better feel and be a bit more progressive, but the 511 has always been run on lipo with no extra weight so might be worth bearing that in mind
