Caster on rear independent suspension
Caster on rear independent suspension
(OP)
I spent ages asking questions, reading and learning how to design independent suspension geometry (thanks again to Greg Locock from this forum who helped a lot), I started with the front and modelled it all in Solidworks and suspension analysis software. Then I just duplicated the same for the rear..... and then moved on to other things. It's just dawned on me though, I can't see why the rear would need any caster? Or would it need some, but less caster, just to reduce load on suspension links? From what I understand the caster is mainly/purely for self centering the steering?





RE: Caster on rear independent suspension
RE: Caster on rear independent suspension
Otherwise, offsetting the wheel to the back or the front could be to make place for drive shafts etc.
RE: Caster on rear independent suspension
RE: Caster on rear independent suspension
RE: Caster on rear independent suspension
It was normally level-ish, and clearly intended to provide rear roll understeer.
Mike Halloran
Pembroke Pines, FL, USA
RE: Caster on rear independent suspension
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Caster on rear independent suspension
RE: Caster on rear independent suspension
In particular, sudden steering inputs can result in small oscillations at the rear due to tire compliance. This is most apparent with a stiff suspension. If two of the lateral links in a 5 link system attach to the upright at vertically aligned points this establishes the equivalent of a king pin axis. Then the third lateral link can control rear toe and can be compliance mounted and tuned to eliminate the oscillation, leaving a smooth step response.
RE: Caster on rear independent suspension
RE: Caster on rear independent suspension
So I don't get a lot of the complex stuff in this thread, but basically I'm understanding "no need for caster at the rear". My plan is to make the rear geometry same as the front, so that the front and rear aren't doing different things. Except at the rear there won't be any caster.
RE: Caster on rear independent suspension
I'm nowhere near an expert, but I'm thinking different front and rear camber curves, toe in curves etc may have been used to advantage on vehicles with any weight bias, whether going straight or cornering.
RE: Caster on rear independent suspension
Common arrangement: MacPherson or double-wishbone front with little or no camber gain with body roll, and beam-axle or some variant thereof in the rear that keeps the rear tires more square to the road with body roll.
You can still do this with double-wishbone front and rear (I presume this is what the original poster is doing); there's nothing saying the attachment points to the chassis have to be the same front to rear, and there's nothing saying you can't design in some roll understeer and/or compliance understeer in how the rear "steering arms" are attached.
RE: Caster on rear independent suspension
RE: Caster on rear independent suspension
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Caster on rear independent suspension
I'm not obligated to use the same parts at the rear, they have to be different as the differing castor will result in different sized wishbones. Plus being at the rear, the rear wishbones would be a mirror of the front ones.
On the same topic. I'm using 40mm scrub on the front in order to get some feedback from the road. This is probably also not necessary at the front so should I switch to centre point at the rear so that the kingpin goes through the centre of the tyre contact patch?
RE: Caster on rear independent suspension
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Caster on rear independent suspension
RE: Caster on rear independent suspension
You asked once before in another thread of mine ツ
I am using a lot of parts such as wheel spindle and driveshafts from a Mercedes commercial vehicle because they are low cost and strong. The uprights are going to be simple custom ones similar to these: