I just rescentl bought a 1986 V6 Firebird.....and it seems to have a weird combo of swaybars.

I measured the front one, and it comes out to a 34mm swaybar.

The rear comes out to about an 18mm or 19mm. Never heard of an 18mm swaybar so I am guessing its a 19mm bar.

Now, should I upgrade the rear bar? The car seems to handle nicely right now....so what would a bigger rear bar change?

 

Less bar in the front is supposed to induce more understeer, less bar in the rear is supposed to induce more oversteer. Alot people here tend to use what the factory offered as a means of upgrades on their own cars, such as the 34/24 combo, or the 36/24 combo. The auto x guys and road racers tend to mix and match bars depending on what they wanna do. Mine is 32/22 on my 83Z. Your application is rather wierd, I always thought that v-6 cars were 29/18(or something like that) I would say upgrade the rear but leave the front be.

 

I upgraded both my bars, 36/24 and love it. Don't forget the wonderbar, and I opted for greasable poly bushings. Cheap and helps

 

Depends on what your planning to do with the car, & the budget you have to work with. Everyone here has a diff. preference, so it all depends on what you want out of the car.

 

That's probably a bit of "over-assumption" right there...

Somebody probably just changed one out without any attention at all to what it was. Hard to say which one.

Just create an actual "setup", as opposed to an "accident", that gives the characteristics you prefer.

As stated, "balanced" bars tend to make the car neutral; more front bar than rear, makes it understeer (push); more rear than front makes it oversteer (loose). Keep in mind though, the spring rates affect it too. Mismatched springs produce a similar effect.

A good balance in these cars for most street use is the springs at 700 #/in front and 160 #/in rear, and the 34/24 stock bars.

 

If you like it, don't change it unless you think you'll like the 36/24 (or some other combination) better. If you do, change it, but keep what you have so you can go back if you don't like it more.