The MGB's standard suspension bushes are made from rubber, and their flexibility absorbs a good degree of vibration from the road, which is good. Unfortunately this flexibility also allows a good degree of movement within the suspension geometry, resulting in adverse handling characteristics, which is bad! Replacement of these bushes with polyurethane ones will have a positive effect on your handling whilst still maintaining the ride quality of a flexible bush - the best of both worlds! They also last considerably longer than the standard ones, making them more cost effective in the long term!!