platypus

iTrader: (1)

so I've gotten myself some MRT camber/caster plates for the front and rear of my car. I think i understand a bit about what changing the front caster angle will do (altering the contact patch of the tire in cornering/under load). What affects will altering the rear caster angle have?

I'm not able to find much on this anywhere...

dropkick_muppet

iTrader: (4)

it's going to change the angle at which the trailing arm sits, and it'll also rotate the lateral links along with it i'd think. since the lateral links are where the sway bar end links mount, i would think it would affect how quickly the swaybar would be brough into action. depening on whether you added positive or negative caster to the rear (i think negative would rotate the rear lateral links counter clockwise, positive would be clock wise -- looking at the assembly from the side) you could either soften or tighten the rear.

the other thing that it might do, would be to slightly change the effective wheelbase of the car, from contact patch to contact patch. i'd think you'd need a lot of caster in the rear to do that, but i suppose it could happen.

platypus

iTrader: (1)

http://wildhobbies.com/news/default....&articleid=302

interesting article on front caster vs camber i just found...

platypus

iTrader: (1)

thinkin about this more...

The caster plate is going to alter the angle of the rear strut. The other attachment points for the rear hub are the trailing arm and the lateral links. By moving the top of the strut, you'll be causing the hub to pivot around the trailing arm attachment point, so what I should see is the hub should be rotated slightly up and to the rear if I move the top of the strut forward (increasing positive rear caster). This would ever-so-slightly lengthen the wheelbase of the car and lower the rideheight by a little bit as well.

dropkick_muppet

iTrader: (4)

that's stated a lot more eloquently than i put it, but thats exactly what i was thinking. i finally got my head straight and realized that the caster would be coming from the top of the strut moving, not the bottom pivot ala the whiteline alk.

i'm curious, is there any particular reason that you went with plates on the rear as opposed to adjustable lateral links?

what sort of caster angle changes are achieveable with the MRT plates?

finally, a technical thread amidst all this noise....

oh yeah, and the link times out.

platypus

iTrader: (1)

the plates I went with to be able to get caster adjustability in addition to camber adjustments. I have no idea if I'll ever actually want to change the caster angle, but I'm just the sort of geek that likes to have the ability to change stuff.

I'll eventually get adjustable lateral links in addition to the c/c plates, but I believe that the lateral links will get me more adjustability in the rear toe in/out than necessarily the caster adjustability.

As far as the angles achievable with these units, I'm not sure. The plate allows about 4 inches of movement, so it'd be a math excercise to see the exact angle chage you could get. (I'm too lazy to do that.)

I currently have the front caster plates setup for maximum positive caster, and when I get the rear plates on this weekend (gotta use the spring compressor over at MPJ) i'll set those up for moximum positive caster as well, just to see how it feels.

The nice thing about these plates is they make changing your camber/caster settings so darn easy!

dropkick_muppet

iTrader: (4)

i completely understand, i'm the same damn way.

i'll be interested to see what kind of angles you're going to be able to run, and how it'l affect the cars handling. all i've been able to find on caster is that it can either make the car more stable, or make it undriveable (not too helpful), though i'm sure that there is a middle range.

oh yeah, is this setup primarily for gravel or tarmac?

platypus

iTrader: (1)

I'll mostly be using it for gravel, as it is on the rally car after all, but one of the nice bonuses of this sort of a setup is the ability to really quickly change the setup for different conditions.

platypus

iTrader: (1)

bump - we've just got to have some serious suspension gurus reading the board...

Gary Sheehan, where are you???

dropkick_muppet

iTrader: (4)

i don't think that many people actually read the suspension forum, most of them just post questions about how to drop their cars for aesthetic purposes.

what is your alignment set at on the car right now?

Steppin Razor

iTrader: (5)

changing caster in the front will have a far greater impact in the front due to the fact that it changes the rate at which front camber becomes more negative as steering input increases.

as for the rear, i would have to guess that caster wouldn't do much of anything since there is no steering input to change the toe settings. unfortunately, that doesn't mean a damn thing because i've no experience with rear caster in real life.

if anything, i will hypothesize that moving the rear struts any further away from vertical than they already are will decrease their ability do dampen the motion of the wheels. as such, rear caster would be one of the last things I would play with in the search for more speed. and that's what we're doing here isn't it?

platypus

iTrader: (1)

Heh, I suspect you're right, but I'm trying to at least get a little technical traffic in here.

Quote:

what is your alignment set at on the car right now?

Right now I'm running -1 degrees of camber on the front, and the max positive caster that the plates will let me get, but I haven't measured it so I can't tell you what the actual angle is.

On the rear, I'm running -1.4 degrees of camber and the stock caster angle (since I still haven't gotten the silly rear plates on the car yet).

platypus

iTrader: (1)

thinking about it, the rear caster angle would affect the suspension travel as the car hits bumps and gets airborne. If I were to stand the rear struts more upright, the travel would be more vertical, potentially allowing the shocks and springs to be more effective.

Quote:

if anything, i will hypothesize that moving the rear struts any further away from vertical than they already are will decrease their ability do dampen the motion of the wheels. as such, rear caster would be one of the last things I would play with in the search for more speed. and that's what we're doing here isn't it?

I'm not sure what effects it'll have, but it'll be fun finding out!