Caster, SAI, Steering and Camber

[Bristecom]

Good stuff. So in simpleton terms, is our stock front suspension setup good enough for aggressive street driving with only grippier tires? Would it be entirely beneficial to add more camber via the OEM camber bolts? Are there any adverse effects of doing that (aside from potentially a little less braking traction)?

Also, do you think there is any advantage to this McPherson strut design (aside from less/lower down unsprung weight) compared to other McPherson and double wishbone designs?

[Wepeel]

Originally Posted by Bristecom

Good stuff. So in simpleton terms, is our stock front suspension setup good enough for aggressive street driving with only grippier tires? Would it be entirely beneficial to add more camber via the OEM camber bolts? Are there any adverse effects of doing that (aside from potentially a little less braking traction)?

Also, do you think there is any advantage to this McPherson strut design (aside from less/lower down unsprung weight) compared to other McPherson and double wishbone designs?

IMO the stock suspension is quite good, easily good enough for anything on the street. It's even good for autocross and tracking, feel-wise, but there are things you can do to it (stiffer, more camber) to make it faster on the clock. More camber will increase front cornering grip and with small amounts the OEM camber bolt provides it shouldn't affect braking performance. I don't see any downsides to it - tire wear shouldn't be an issue as long as toe is in alignment.

I don't think there is anything novel about the BRZ strut design - it's pretty straightforward, simple - definitely not as complex as some other front strut arrangements I've seen (BMW, Ford, ...). I think the handling ability of the BRZ is more due to being low weight, light weight, low polar moment, etc, rather than suspension wizardry.

[DrDuquette]

I'm still a little confused on Caster. Is this what we need? .5 more degrees?
I'm trying to read and figure it out, but this stuff is a little over my head right now.

http://www.whiteline.com.au/product_..._number=KCA434

[DriftEightSix]

This thread hurts my head and I don't know how I should have the car setup :'(

[DrDuquette]

Originally Posted by DriftEightSix

This thread hurts my head and I don't know how I should have the car setup :'(

Yeah the more I research the more I just want to make the car look good than handle amazing. Haa haa.
Lets just "Bag It" and call it a day!!


Sent from my iPhone using Tapatalk

[Wepeel]

Originally Posted by DrDuquette

I'm still a little confused on Caster. Is this what we need? .5 more degrees?
I'm trying to read and figure it out, but this stuff is a little over my head right now.

http://www.whiteline.com.au/product_..._number=KCA434

More caster will certainly help, to a point. Based on what I've tried on my previous strut cars, getting up to an additional 0.5-0.75 deg of caster from stock helped, but anything more than that made the steering feel a little odd.

[Manji]

Interesting read, thanks.

It would be great if someone with coding experience could put together a SAI and scrub radius calculator, with variables being wheel/tyre size, wheel offset, camber adjustment at tophat, hub, and LCA. Similar to the wheel fitment program that was written.

I've changed my wheel offset from +48 to +16, and I'm interested in knowing how much I should be increasing SAI to counter the offset change and subsequent increase in scrub radius. I'm thinking that I'll then need to run a positive camber setting at the hub, to offset the excessive neg camber from increasing the SAI.

[sunset_blvd]

Originally Posted by 7thgear

not to take away from what you have said, i would just like to point out that we all shouldn't be using F1 cars as examples because those cars rely on speed for grip. As that guy from top gear showed us, if you drive an F1 car slow, you'll spin)
.

That's only because of how much grip comes from the downforce. The basic suspension geometry rules still apply.

[sunset_blvd]

Originally Posted by DriftEightSix

This thread hurts my head and I don't know how I should have the car setup :'(

I'm still learning the car after switching from the Porsche world, but my feeling is as follows:

-1 to -2 degress of camber all the way around
add a little bit of caster
correct roll center proportionally for any drop in ride height.

[sunset_blvd]

Originally Posted by 7thgear

as you can see, the outside wheel not only has to deal with the geometrical movements of the suspension, but also the relative re-positioning of the chassis pickup points in space..

Really good point. There really are a fuckload of variables to consider.

[cdrazic93]

Its hard to limit what changing caster will do to just camber, there is an almost infinite amount of stiffness you can increase or decrease from the chassis along with spring rates, LCA's and toe.

It would be interesting to see if anyone could stick in some alternate caster settings into the proper suspension model sticky.

[cdrazic93]

@Racecomp Engineering @plucas @Shankenstein

I wonder if you guys have anything to add?