sscottttt

iTrader: (4)

I wanted to start a discussion to find out peoples thoughts on adding caster vs. adding camber to the Evo. Everyone seems to talk about camber with caster hardly ever being mentioned. There must be some combination of both but I think caster should be more prevalent and the effects better understood.

From all that I've read on suspension design/geometry I don't see many downsides to increasing caster, you don't need to run as much static camber so you can maintain better straight line braking performance but when you go into a turn and crank the wheel you get the camber you need to get the most out of the tires. The focus when getting the Evo to turn is on keeping the outside front tire working at its maximum potential but unless the inside front tire is lifting then it's helping the car turn and caster helps to keep a better contact patch on that tire as well where extra camber would hurt. Caster can make the steering wheel harder to turn but with power steering this shouldn't be a factor.

I'd like to hear from some of the suspension guru's out there to get their thoughts on the subject. Is my logic off-base, is there some major disadvantage to running lots of caster?

GTWORX.com

iTrader: (35)

You're absolutely right....caster is something that IMO is lacking on a stock EVO and something that most people neglect to pay attention to. I've tried to get people to rotate/cant their camber plates so they can add caster too but so far I don't know of anyone that has done it.

The difference on a stock WRX going from +3.5 to +5 or even +6 degrees of caster is phenomenal and the effect is similar on an EVO.

EDIT: thank you for starting this thread!

- Andrew

ForcedFedRS

iTrader: (23)

I wish the Evo had far more caster. Wish it had something similar to the RX-7 front suspension, you can get crazy caster out of them.

GTWORX.com

iTrader: (35)

Here's a good read:
http://www.iwsti.com/forums/gd-suspe...-analysis.html

- drew

nils

iTrader: (56)

when we added caster to my car with the k-mac camber plates my turn-in felt alot better, crisper.. if that makes sense.

goofygrin

iTrader: (5)

Ya that makes sense.

I'm trying to get more camber with the lower bolts on my X. I might rotate the camber plates toward the rear to get more caster after reading some of that above thread.

Poor man's Vorshlag camber/caster plates?

RaNGVR-4

iTrader: (4)

There is no downside to added caster for a road-going car. I never have understood why mitsu designed in so little caster. Add caster however you can, its as simple as that. as you stated, you gain more camber on the outside wheel when turning, with added caster, so you can run slightly less static camber. I really dont think there is a downside at all, other than possible toe changes while turning.

goofygrin

iTrader: (5)

More caster = increased nose dive when breaking (according to that STi discussion).

Damn. I'm going to have to take apart my car tonight aren't I?

sscottttt

iTrader: (4)

You're welcome! I haven't seen one of your suspensions discussions in a while so I thought I'd start my own. General consensus seems to be that caster is a great thing with very minor drawbacks .

Nils I'm wondering if you also reduced your static camber since you wouldn't need as much if you have more caster. It would then make sense that your initial steering response would be stronger.

I think this only applies to adjusting the caster by changing the angle of the lower control arm (also known as anti-squat). Moving the top strut mount rearward should not have any effect on this.


Thanks for all the responses guys, I guess my next question is what is the best or cheapest way to get more caster, what set up will get you the most caster and is there a more affordable way to get this adjustment than expensive plates (Whiteline, K-mac) or offset bushings (Perrin)?

madmax199

iTrader: (20)

Scotty, adding caster up to a point can help greatly for all the reasons mentioned. However, the more you add, the steering will start to feel numb(kind of like driving on bias ply slick with low pressure and you have to anticipate a lot to compensate). The easiest/cheapest way to add caster would be to slot the top mounting holes like I did on my car, I don't know if you ever paid attention to that but I doubt that it would be legal in anything but prepared classes. Are you coming out to Tobay beach(MNY PCA) this saturday it's the only good lot we have in the Island?

goofygrin

iTrader: (5)

Has anyone used the camber bolts? Whiteline/spc 81260/whatever in order to increase camber at the knuckle?

They are reasonably inexpensive (<$30), but since the bolt isn't as thick it won't be as strong as the OE bolt and that concerns me a bit since the car is a daily driver as well as autocross and track toy. Of course, my other option is to notch the strut until Stance gets me new lowers with offset holes (they have said they are working on it).

Bryan at JRZUSA

Caster is track dependant

sscottttt

iTrader: (4)

Hey Max! So what you're saying is the more caster the harder it is to feel through the steering wheel that the front tires were breaking loose. I've never seen the slots on your car (to think of it I don't think I've ever seen you car with the hood up!) but I'm not ready to start cutting up my shock mounts quite yet. I wish I could make it out to Tobay this weekend but I've got a lot going on plus I won't have my new tires until sometime next week. I ran there for one event last season and that lot is really nice, well anything is nicer than the coliseum lot. So have you got a car back together yet?

I've been looking into camber bolts as well especially after reading the info from that subby thread that Andrew posted up. It looks like adjusting the camber to the max at the bottom of the strut and keeping the strut as far out at the top will yield the best steering geometry. The only problem with this is that it brings the strut closer to the tire so if you're running big rubber or wide wheels without an aggressive offset this may cause clearance problems (which i will probably find out since I ordered a set of 17x9.5" wheels with only a +35 offset).

Bryan could you elaborate on this at all, I'm wondering what factors help you determine the amount of caster you want to run is it track layout (more tighter slow speed corners vs. high speed sweepers?) or is it just driver feel and if so how does caster make the car feel different to the driver? From what I can tell so far you lose some feedback in the wheel to gain initial steering response.

goofygrin

iTrader: (5)

This isn't a huge problem for me because I run fairly skinny tires on my street wheels (stock X 18x8.5+38 with 245/40/18). I think I'll be ok on the track too since I'm running a fairly aggressive wheel (18x10.5+15).

Don't hate me because I have room under my fenders .

madmax199

iTrader: (20)

Scott, it's hard to describe but with more caster the car's response to steering inputs was kind of delayed a bit altough grip was increased due to the camber gain associated with it.

In transition you'd have to anticipate the delay or you'll be clearing the cones by a foot(remember I couldn't stay away from cones when driving your car, I was steering way too early especially in slaloms because I got use to the effect of the added caster).

I wouldn't suggest you to slot your holes because not only it's illegal for your class but it takes quite a bit of fabrication to get the fatory strut bar to bolt to the firewall. I'll be driving a project EP that I'm building(low budget, low weight, low power but real slicks and lots of fun to drive). Give me a call, I cant run the EP car at the NC(too bumpy) so I'll be doing more PA and DC event this year including the the DC pro.