I've autocrossed with my front bar disconnected and a stock rear bar; I've also autocrossed with an aftermarket rear bar.
With the front bar disconnected you can put power down really well. The front wheels never lift, and you can get on the gas pre-apex with no wheel spin at all. It's cool in that respect. However, because we have struts in the front, all the body roll that results from a disconnected bar end up reducing grip severely. You end up being able to use the gas pedal a lot more, but carrying so little speed through turns that it doesn't help you overall. It also makes steering response feel like garbage, although that would be something you could easily drive around if it were the only downside.
A stiffer rear bar, on the other hand, has the same benefit as a softer front bar -- more front grip, you can use the gas more aggressively -- without the downsides of disconnecting the front bar. You have less body roll overall, and because you're keeping the front suspension in a less bad part of it's camber curve, you get more grip overall. Technically you lose a bit of rear grip, but we have such an abundance of rear grip in these cars that it's really no problem to trade some rear grip for some front grip. You retain a good steering feel too.
It's interesting what a difference there is with the front bar disconnected actually. It's a good lesson in suspension tuning. The stock front bar isn't particularly beefy, but because so much of the cars weight is on the front wheels, small changes to the front end have big impacts. Disconnecting that flimsy little front bar results in huge amounts of body roll.
Another thing I think needs to be said is that, while it's true in this case, body roll and soft steering response aren't necessarily bad. Body roll is bad for us because of our strut suspension, because the strut suspension doesn't gain camber under compression; when the body rolls, it puts the wheels at a bad angle to the ground, reducing grip. On the other hand, an a-arm suspension gains gamber under compression, so you can sometimes remove the front bar to get more grip in the front. You'd still get more body roll, but it wouldn't reduce grip nearly as much as it does on our cars.
I mention this because one of the biggest lessons in suspension tuning is that what feels fast and what is fast may not be the same. Don't get into the trap of over-simplified thinking like "body roll = bad" or "soft steering response = bad". That thinking happens to lead to the right conclusion in this case, but it's poor logic.
Last edited by ckingsley; 05-14-2013 at 10:41 AM.