Aspire sway bar in a BP Festiva

[FB71]

The aspire rear beam shifts weight to the outside rear in a corner, reducing bodyroll and allowing the inside front tire to do more work. The combination of reduced rear traction(one tire is doing more of the work) and increased front traction(more even work load) balances the understeer built into the festiva. With the aspire rear beam and sufficiently stiff springs the bodyroll is minor enough to have no effect on the suspension, increasing overall grip compared to a stock suspension. Stiffening the front swaybar will off balance the car, causing more understeer and reducing the overall grip of the car.

You might feel quicker turn-in, which would definitely make the car feel faster.

ok, you did your homework! I stand corrected!

[FB71]

Alot of FWD AutoX cars do NOT run a front bar at all... Just some food for thought. -Kyle

good point! The Mustang Cobra in '99, when IRS was introduced, used a 3mm smaller diameter front swaybar than the GT, and was capable of higher turning G's.

[FestYboy]

Originally Posted by oxbrain
The aspire rear beam shifts weight to the outside rear in a corner, reducing bodyroll and allowing the inside front tire to do more work. The combination of reduced rear traction(one tire is doing more of the work) and increased front traction(more even work load) balances the understeer built into the festiva. With the aspire rear beam and sufficiently stiff springs the bodyroll is minor enough to have no effect on the suspension, increasing overall grip compared to a stock suspension. Stiffening the front swaybar will off balance the car, causing more understeer and reducing the overall grip of the car.

You might feel quicker turn-in, which would definitely make the car feel faster.


nope, still backwards... read it carefuly again and you'll see the mistake

[FB71]

I think he might be right, Arty...

But then again, I'm not really a suspension guy. I'm an engine, trans and EFI guy.

[FestYboy]

well as i read it, if you induce more weight transfer to the outside rear, you'll also incure more likelyhood of oversteer due to overloading the outside tire. now once the outside rear starts to slip and the rear comes out, the chassis can then become more nutral BUT it can also reset mid turn and cause chassis undulation, making the car feel nervous.

upping the torsion rate of the front can augment the outside front spring durring compression AND force the inside to sit lower thus allowing the inside to do more work. to augment this further, start by upping the rear spring rate to keep the rear outside from squating and keep the chassis more level (less incured twist mid-corner).

[oxbrain]

Shifting weight to the outside rear can reduce the overall grip of the rear end, depending on the tires you're using. With 70% or more of the weight on the front end, shifting the whole rear to one tire still leaves it with more to spare than the front. Our track cars lift the outside rear a couple inches at the limit and they'll still understeer first.

I've never noticed undulation in the chassis. If the rear is breaking loose the car rotates so fast that the corrections mask any weirdness from the rear. A better driver might notice something though. :dontknow:

Cornering under acceleration there is a lot of shimmy from the rear beam moving in the bushings and the trailing arms flexing. It happens right in the transition from turn-in to steady state, the rear beam takes a half second extra to get settled in. It feels like a slight increase in steering input, or a pushing from the outside rear.