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Tom Garrison 09-12-2002 09:40 PM

What are results of larger sway-bars?
Own a 1993 300E. Would like to reduce the roll of the car in corners without excessively changing the ride quality over varying surfaces, e.g. railroad tracks. Am considering adding the Sportline sway-bars that Mercedes Shop sells with their Sportline Kit. While the result of putting larger sway-bars on the car seems obvious, just wanted to confirm such with some folks on this forum. Would appreciate comments as to whether putting larger sway-bars on the car will reduce the roll of the car through turns without changing the height of the car nor any other driving characteristic(s). If the larger sway-bars will change some other driving characteristic(s), what would they be? TG

bobbyv 09-12-2002 10:50 PM

larger sway bars have no effect on pairs of wheels that are moving up and down at the same time, e.g., while moving over railroad tracks at the same time. And unlike stiffer front springs, swaybars do not have any effect on brake dive.

the obvious effect of sway bars, as you already know, is to increase roll resistance.

What is not so obvious is that the tuning of the front vs rear swaybars (among other things) has a big effect on handling:

- A stiff front swaybar tends to increase understeer (Porsche 911s have stiff front swaybars to compensate for the rear's tendency to oversteer; that's why you see pictures of these cars doing extreme cornering with the inside front wheel lifted).

-To reduce understeer, one would increase the stiffness of the rear swaybar. This is usually done for example on front-wheel-drive cars, and it is not uncommon to see them lifting the inside rear wheel during hard cornering.

I believe that swaybar tuning for a front-engine, rear-drive car is tricky: such a car would normally understeer because of the heavy front, and one would normally increase the rear swaybar stiffness to counteract this. But using a stiff rear swaybar would reduce the grip of the inside driven wheel during hard cornering while accelerating.

While one would tend to use stiffer swaybars for performance-oriented driving, there is a point of diminishing returns: for example, if the swaybars were so stiff that the left wheels do not move up and down relative to the right ones, during a hard lefthand corner, the vehicle would still roll because of the laws of physics, but the left wheels would completely lift off the pavement (or just reach that point when they are about to do so, at which point they lose all grip), and all your grip will be limited to your right tires.

on F1 cars for example, they reduce rollbar stiffness when it is raining, to increase mechanical grip. And they vary the front vs rear stiffness as they use up fuel.

yhliem 09-13-2002 03:19 AM

Yep...that about sums it up.

Tom Garrison 09-13-2002 09:15 AM

Thanks much. TG

400E 09-15-2002 08:28 AM

From what I've heard, the trick is to only go up one notch in diameter/stiffness -- i.e., if you have a 300E, go to 400E sway bars. I have a 400E and went with 500E sway bars and they do indeed reduce body roll significantly, and the ride quality seems better, if anything ...

ke6dcj 09-16-2002 01:13 PM

Excellent write-up. I would add that when upgrading swaybars, to upgrade both the front & rear since they work together as a system.

Case in point- I upgraded the front swaybar of the wagon to a SportLine, and left the rear stock. Understeer!

Upgraded the rear to a 500E rear swaybar (about 1.5mm thicker than SportLine rear), and now the car behaves more neutral (less understeer).

:-) neil
1988 360TE AMG
1993 500E

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