Originally posted by 20 SMOKE
how about the spacers on the rear upper links on top of the hubs
Rear Camber Links
Changing the length and position of the rear upper link changes the roll characteristics of the car.
The following generalizations apply in most cases.
· An upper link that is parallel to the lower A-arm will make the Roll Center sit very low when the car is at normal ride height, hence the initial body roll when entering a corner will be big.
· An upper link that is angled down will make the Roll Center sit up higher, making the initial roll moment smaller, which makes that particular end of the car feel very aggressive entering the corner.
· A very long upper link will make that the roll moment stays more or less the same size when the chassis leans over; and the chassis will roll very deeply into the suspension travel. If a lot of camber is not used, this can make the tires slide because of excessive positive camber.
· A short upper link will make that the roll moment becomes a lot smaller when the chassis leans; the chassis won't roll very far.
In general, you could say that the angle of the upper link relative to the A-arm determines where the roll center is with the chassis in its neutral position, and that the length of the upper link determines how much the height of the Roll Center changes as the chassis rolls.
· A long, parallel link will locate the Roll Center very low, and it will stay very low as the car corners. Hence, the car (well at least that end of the car) will roll a lot.
· An upper link that's angled down, and very short will locate the Roll Center very high, and it will stay high as the chassis rolls. So the chassis will roll very little.
· Alternatively, a short, parallel link will make the car roll a lot at first, but as it rolls, the tendency will diminish. So it will roll very fast at first, but it will stop quickly.
· And a long link that's angled down will reduce the car's tendency to roll initially, but as the chassis rolls it won't make much of a difference anymore.
In terms of car handling, this means that:
· When the link is angled down the most (highest Roll Center) gives the most grip initially, when turning in, or exiting the corner,.
· With a lower Roll Center when the chassis is rolled gives the most grip in the middle of the corner.
· If you'd like more aggressive turn-in, and more low-speed steering, set the rear upper link at less of an angle.
Now you might ask yourself: what's the best, a high Roll Center or a low one? It all depends on the rest of the car and the track. One thing is for sure:
· On a bumpy track, the Roll Center is better placed a little higher; it will prevent the car from rolling from side to side a lot as it takes the bumps, and it will also make it possible to use softer springs which allow the tires to stay in contact with the bumpy track.
· On smooth tracks, you can use a very low Roll Center, combined with stiff springs, to increase the car's responsiveness.