int it obvious, if yer got bigger wheels on , yer have smaller profile tyres. as a fair amount of suspension is yer actual sidewall you in effect take away some of the shock absorbtion by uppin yer wheel size.
this improves cornering , usually, and stiffens up yer ride resulting in more bumps and shocks finding there way through the vehicle body.
if you want to do it properly , when you go up a wheel size you should really change yor springs for slightly bouncier ones