build a gmaxx and i need help

[Maxxrickard]

okey. 70wt front and 60 in the rear?
but i have the harder spring in the rear?rookie....
if i dont find harder springs is it possible to use longer springs?i will by a set of fron/rear spring and will use the front spring, but if they are to soft in the rear i maybe can use the rear springs in the rear....
will it be more firm if the are longer?