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Effects of a stiffer rear sway bar (other than mid-corner balance)?

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323
318
Exp. Type
Autocross
Exp. Level
20+ Years
So Cal
I love Carroll Smith books.
Indeed. It's important to note that his conceptual ideas weren't correct from a physics point of view, but that's really not all that important. He produced an early race car vehicle dynamics model which allowed him to get consistent results from his changes and he was one of a very few who was willing to put his ass on the line by publicly by explaining his model. He was right on enough of it that the stuff he wasn't we can kind of set aside. It's hard not to be impressed with a guy that can figure out all that he did with little more than pencil and paper. I wish we could have gotten Maurice Olley's math and Carroll's practical experience together on just one project of that era. As long as we're at it, let's throw Rem into the mix to keep those two nerds in line.
 
323
318
Exp. Type
Autocross
Exp. Level
20+ Years
So Cal
Understeer on turn in and mid corner. Trail braking helps a lot, but I wanted to go further and experiment with the rear bar.

I'm a little concerned at if it would drastically change the car's balance during aggressive corners like T1 @ Sonoma or T6/T9 @ Laguna though - understeer is much better than oversteer in these cases
This is my opinion, so take it with the appropriate dash of salt.

I don't find the RARB to do much on turn-in. The initial turn-in of the car is much more controlled by the front end of the car. The rear bar only takes effect after the chassis has developed significant body roll and that doesn't happen immediately.

As RES says, the front bar will have the effect of giving an increase in response to the initial point of the nose (the steering geometries produce a twist in the bar before the chassis has time to roll, which is why its effect happens earlier than the rear's). I also agree that this increase in response will often be followed by an increase in steady state understeer.

The effects I've felt from changing the front bar is more of a increase in mid-corner stability rather than big balance shifts. I suspect a feller' could make and run a front bar significantly stiffer than the over-the-counter models. Having said that, I don't think your issue has anything to do with bars. I think you're lacking front spring rate. For me, increasing the front spring gives a massive benefit to corner entry, because it allows me to load the front end of the car so much better with my feet. With a softer front end, I find tiny variations in braking make such a dramatic pitch change to the car that's it's really tough to find the correct trailing-brake balance. If you don't put enough pitch into the car, you get U/S and if you get too much pitch in the car, you get O/S. Finding the happy medium is tough. BMR has a 300# front spring and Steeda has a 350# front. I think either of them would be an improvement over the 250# spring you're running. Ride quality is subjective, but I'm on 450's and completely happy with them in terms of ride.

If you'd like to make a quick and easy test to see if this is a path you'd like to investigate, then just buy a spring rubber and throw it in your front coils next time for a test. They take about 30 seconds to put in/pull out. It will stiffen your front spring and raise your front ride. Give it a run and see what you think. Remember, it's not just roll couple. If you are able to make the car more stable on entry so you can be more aggressive with the wheel and be able to get to the apex with the car at a better angle, the increase in front roll couple might be a completely moot point in terms of balance.
 

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