by Malcolm » Mon Feb 09, 2009 11:30 pm
increasing the track width at one end of the car will increase the resistance to roll at that end (by the percentage that you increase width), which will shift your roll stiffness distribution to that end, which will decrease grip at that end, but it'll be f*ck all change.
the change of track width also decreases the total lateral weight transfer, which should increase grip (once again, at the values you're talking about it will be bugger all)
With most suspension systems, adding spacers will also change the motion ratio of the springs/dampers, changing the wheel rates, which would be a larger effect (it'll soften it at the end you increase the width at).
There will also be an effect if you add spacers at the front, not specifically on the performance but on the steering feel. The effect will depend on whether you have a negative or a positive kingpin offset (scrub radius), but it'll either decrease or increasing steering effort and feel. On my MR2 there is a negative scrub radius and increasing the track width (through different offset wheels) decreased the steering effort and feel.
To answer the question of whether it's better to do with spacers or suspension - if you have double wishbone suspension then it would be nicer to do it with new wishbones, but it's way easier to do it with spacers/offsets if you're happy with the effects that has on the steering feel.