Scottish Elises

hiscot · Post by **hiscot** » Fri Mar 09, 2007 1:07 pm

if i was to lower the car what effect will this have on the arb as adjustable ones will act as shorter/longer droplinks
i have fitted shorter bmw drop links so the status quo should remain but if i had replaced with std will the arb be less stiff ?

woody · Post by **woody** » Fri Mar 09, 2007 5:06 pm

No effect at all AFAIK

Lowering the car will have no effect on the stiffness of the bar.

mac · Post by **mac** » Fri Mar 09, 2007 5:12 pm

It will have an effect - I'm just not bright enough to tell you what the effect will be

Given that one end of the arb is fixed to the tub then the force is applied by the arb is a function of the distance between the fixed point and the drop link. changing the ride height in relation to the fixed point in the tub will give different arc effectivly altering the lenght of the arb - if the loaded arb is below the fixed point before changing the ride height then moving it will soften the effect of the arb - the opposite if it's above.

Chances are that the effect will be un-noticable though.

Mac (doing moment distribution at college faction)

mckeann · Post by **mckeann** » Fri Mar 09, 2007 5:16 pm

my understanding (so probably wrong) is that the ARB resists roll by twisting. so if the car is lowered, it will make no change to the stiffness of the bar, as both ends are lowered by the same amount.

this is just a guess, i would wait for robin or lawerence to give you the correct answer

woody · Post by **woody** » Fri Mar 09, 2007 6:43 pm

mac wrote:It will have an effect - I'm just not bright enough to tell you what the effect will be

Given that one end of the arb is fixed to the tub then the force is applied by the arb is a function of the distance between the fixed point and the drop link. changing the ride height in relation to the fixed point in the tub will give different arc effectivly altering the lenght of the arb - if the loaded arb is below the fixed point before changing the ride height then moving it will soften the effect of the arb - the opposite if it's above.

Chances are that the effect will be un-noticable though.

Mac (doing moment distribution at college faction)

It's not fixed to the tub though. It's able to rotate in it's mounts.

Your right about the moments though - hence why the LSS/motorsport ARB has five holes at the ends in order that the lever arm length can be adjusted. The bar its self acts against (to compress) the opposite wheel/suspension on the same axle as the wheel being effected by the cornering loads. i.e RH corner, LH suspension in compression > the LH wheel acts to compress the RH suspension through the ARB in effect stiffening the LH suspension.

Full write up on this very issue in this months evo mag letters page - but i'm too lazy to type it here

ETA: The shortening the lever arm has the same effect as stiffening it - both mean more force is transfered from one side to the other.

hiscot · Post by **hiscot** » Fri Mar 09, 2007 7:35 pm

thanks woody i shall get evo mag tomorrow
but although its able to pivot in its mounts if the chassis inc its mounts are lowered then the angle / relationship to wishbone alters
but i havent a clue if it changes anything

woody · Post by **woody** » Fri Mar 09, 2007 7:43 pm

bUT ITS one wheels relationship to the other's that counts. If (as should be the case, and within a few mm) there is no difference in ride height accross the axle, then nothing changes.

The angle has nothing to do with it, and in reality there is no change in the relationship.

wiki link if it helps:

http://en.wikipedia.org/wiki/Sway_bar