Driving Impressions: Lower Stress Bar

[insite]

Originally Posted by Lil bastard

Is there any data supporting the addition of the side bars? I can see the necessity of the lower stress bar side-to-side (Camber), but there is already significant bracing against fore/aft (Caster) movement.

I've dismantled the rear suspension when I did my tranny work and personally, these side bars appear to be overkill in all but the most extreme track use (I do not incl. Auto-X or DEs).

I have the Mantisport 'Ernie' bar and noticed improvement (not extreme or significant, but definitely improved), + Fr/Rr. Strut Tower braces.

Can someone show me some data that this area requires additional bracing, because I'm not convinced that the side bars are a necessity, or even a positive addition. There's no benefit to over-strengthening something which is already strong enough to do the job.

it is my opinion (as an engineer) that the side bars are not necessary. anti-squat is adequately addressed by the diagonal links. longitudinal flex at that portion of the subframe is tensile and is adequately addressed by the shear plate.

the reason the cross brace (ernie bar) is so helpful is because there are compressive forces between the left and right halves of the subframe that a shear plate cannot resist. because of this, the distance between the lower control arms was actually dynamic under hard cornering loads. the stress bar hard locates the lower control arms (and in turn, camber), picking up where the shear plate leaves off.

[Lil bastard]

@insite - Thanks for the eloquent explanation. You lend credence to, if not confirming outright, my suspicion that these side bars are a redundancy.

Lord knows, I'm not against spending money on improvements. But, I don't wanna do so on things which offer no real benefit.

[Topless]

Well I got my lower stress bar (Bristol Bar) yesterday and installed last night. Installation was a snap with good instructions. The hardest part was chocking the wheels and jacking the car.

I then took her for a quick spin over my local test road. This is a public road so I wasn't really pushing it but I got in enough spirited cornering to feel a difference. Definitely more planted and precise at the rear wheels, especially over uneven road surfaces. Track days are coming soon so I will know more over the next month.

As an added bonus I noticed an absence of creaking noises from the top while slow cornering through rain gutters and up my sloped driveway that normally cause a little chassis twist.

Thanks to insite for discovering this little gem and Kirk for your product development.