PDA

View Full Version : Learn me the importance of caster & camber



4thgenceli
03-21-2011, 09:32 PM
You may remember a while back I was thinking of buying a set of Megans coilovers for my st162. While they don't make them for the st162, the st182 appear easy enough to fit with slight modifications to the chassis.

From st162.net however there is a seller in Australia that builds custom coilover kits that are comparable to Megan. The only difference really is they do not come with caster or camber plates. They can be purchased at an additional cost, however are not included.

I understand the importance of camber, but not so much caster. Can someone learn me why caster plates are necessary and not just camber?

Luni
03-21-2011, 10:03 PM
Im pretty sure the strut itself has nothing to do with caster on a macpherson strut setup.

Caster is related to steering tension. The more caster used, the more the wheel resists turning forces, providing stability. Too much caster makes it very difficult to steer, and causes the tire camber to change significantly as the wheel is turned. Not enough caster results in the front end "wandering," or trying to turn on its own.

Camber is the angle the tire leans into or away from the car. Usually camber is controlled by camber plates on the coilovers, or by using camber bolts which are lobed, that push out or pull in on the steering knuckle where the coilover (strut) attaches to the steering knuckle assembly.

Caster is usualy adjusted (if its adjustable) by the strut rod itself. Not on the actual strut.

KoreanJoey
03-21-2011, 11:15 PM
Rob, that's not exactly correct.

Caster is the angle of rotation of the hub on the vertical axis viewed from front to back. Positive caster does two things, steering feel and camber on cornering.

The higher the positive caster the heavier the vehicle wants to keep the wheel straight, increasing steering feel. On the same note the increased positive caster will increase camber under cornering, good for performance but needs some tinkering in order to get what you want vs roll. Most McStrut vehicles don't have any provisions for adjusting caster but it is possible. Some manufacturers make a camber/caster adjustable plate; adjustable fore and aft (caster) along with inboard and outboard (camber).

alltracman78
03-23-2011, 03:03 PM
The easiest way to "see" caster is to look at the front forks on a motorcyle.
"Cruisers" have more positive caster, while sport bikes have very little.

It's basically the verticle axis that the front wheels pivot on when you turn the steering wheel.
Squat down on the side of your car, facing you front wheel.
Draw an imaginary line from the center of the lower ball joint up to the center of the strut mount. That line is your caster.
If you move the strut mount further towards the rear of your car you'll have more positive caster.
If you move the strut mount more towards the front of the car you'll have more negative caster.

Increasing positive caster will make the vehicle want to stay in a straight line while rolling [harder to turn, more stable in a straight line], it will also increase camber when turning.
Lowering postive caster will make the vehicle less stable in a straight line [will want to wander] but will make it easier to turn quicker, just like the less positive toe your wheels have.
Which is why a bike made for cruising down the road has lots of positive caster, so you can relax and chill, while a sport bike has much less postive caster, so the bike is more agile and can turn quicker.

cms-gt4
03-28-2011, 07:22 PM
On the note of 16x caster, whiteline offers a caster bushing. It will not work in 18x models, but it is an option. Gtfour77 built a his own lower a-arm and used spacers to change caster. Different methods of building lower a-arms allow for caster change. He also built his own suspension system all around, include roll center adjusters.