Lads I've an E46 318ise running OE M-sport springs and shocks.
It still has SE ARBs, the front SE bar is actually thicker than the sport but the rear is thinner at a mere 15mm, I think the sport one is 18mm.

I'll be doing the rear diff bushing soon which will involve removing the rear ARB and I was planning to replace the ARB bushes while I have it off.

Am I likely to notice much difference in the handling with a thicker rear bar? I could pick one up cheap enough in a breaker I guess.

I realise it would make the car a little more biased towards oversteer than my current setup but is it worthwhile?

Cheers.