You say I'm wrong, but offer no counter points.


I'm simply stating what I have (mostly) learned/observed from setting up my offroad car, and helping set up other offorad cars, and what I observe with setup changes on friends' Evo's.

 

Our theories may be wrong, but they are working, I guess. My car pushes = more rear bar = car comes around, be it due to less grip in the rear or more in the front. My softer spring rates work wonders for tire wear and the car seems to handle well. The guy that recommended my settings knows more about setting up an Evo than I do... I suppose that's why he make a living at it.
Despite what the internetz says, I'll listen to him.

 

There are lots of ways to skin the cat here and you should be doing what gives you results that you are happy with! No questions about it!

But, when you write sentence like the one quoted above, it shows just partial understanding of what is going on. For example, it does'n not explain why stiffer bar in the front of the stock EVO gives more grip on that end and improves overall balance, does it!

 

Nope, It doesn't for me. Any time we've upped the front bar and left the rear, the car pushes (spring rates and tires remaining constant). I haven't experienced the car driving better with that setup so i gotta take your word for it.
That sentence was somewhat facetious, by the way Too much Rockstar today.

 

my car is definitely pushier after adding a FSB lol.

 

It is because of the 60% front weight bias, mac strut suspension, the car is AWD, it has a terrible front roll couple, and the large bulke of the weight of the engine and trans is ahead of the front axle center line.


Increasing weight on a tire has a diminishing return on grip. The Evo overloads the outside front tire and has camber loss with bump when lowered (and even more due to the excess body roll), which all induces understeer. An FSB helps more evenly distribute the load between the two front tires, reduces roll and bump (which reduces camber loss), which increases grip, in this fairly isolated case.

Your must have had enough spring to begin with then, or are you on the stock rear bar?

 

Why you so mean to my Evo??

 

I feel like it's 2007 again and it's Robi Vs Muller lol. End of the day practice what you preach ON the track, not in spreadsheets or based off of 5 years of EvoM compiled opinions. We're better here in the MS section cause we DO it, not slap it in others faces to satisfy our Internetz status (although admittedly fun sometimes)

 

I agree. I'm no professional driver, but the car is fast and does really well. I must have done something right. 😂

 

I'm just trying to have a conversation, and I'm simply getting told I'm wrong, and drilled with questions.....

 

I've been following all the discussion and it's been great info.

I posted my setup here in this thread several weeks ago and I'm kind of second guessing my decision to get a stiffer 25mm adjustable rear sway bar. I have coilovers with 10k F 12K R setup and will have my rear sway bar in a weeks time. I intend to set it on full soft and see how the car does. I've also gotten the English ACD ECU tune and did an autocross last month with the stock rear sway bar. My new coilovers paired with the ACD ECU made the care feel nothing like it was before, which only makes sense. Prior to the coils and ACD tune my car was on stock struts with lowering springs and was very loose at times in autocross. With these new updates and testing set ups I hope to pick up some faster times.

 

I'd imagine you should be okay. Give it a shot. I was on 8/9k and now up to 9/11k going down to 9/10k, all on a 25mm RSB. I THINK I'm on the middle setting. I'd have to look. The car works awesome, though. And I agree that ACD tune is amazing and makes the car even BETTER.

 

Ohlins 8/10, WL rear bar on soft, Tanabe FSB in front, and the appropriate WL bushings.

2014 season: ohlins, stock bars, WL bushings. Car was very pushy. Added ER ACD tune, which helped turn-in tremendously, but still some kind of mechanical pushiness.

2015 season: purchased ciro caster plates and whiteline RSB to fix the push. Turned out the shop installed the coilover springs at 10/8 instead of 8/10. Added all of those and corrected the spring rates, and the car was extremely loose, biting me mid slalom.

2016 season: Added Tanabe FSB, new tires, and cranked up the shocks. Car is now much more neutral. Tanabe FSB added more push, particularly in tight corners. Car still feels unstable though in slaloms, but overall way better. At the end of the season I increased the front camber from -2.7 to -3.3, which helped mid-corner grip a good deal.

Looking forward: Will go from 17x8 to 17x9.5, and 255s from 245s. Expect it will increase push, so I'll decide at the time how I want to adjust.

The ER ACD Tune & Cusco 1.5way rear diff have been two of the biggest impacts on how my Evo handles. Originally I had just added the Cusco 1.5way, and while the rear diff added a TON of power-on oversteer, I experienced increased off-throttle push on turn-in due to the aggressive nature of the diff. The ER ACD tune completely wiped that away - it added an eagerness and easiness to the turn-in, without adding oversteer/big yaw angles (unless I want it). Actually, prior to the ACD tune, I was considering looking into decreasing the rear diff aggressiveness (less springs, turn some plates) because of the slight binding feel I was getting on turn-in - that is now totally gone with the ACD tune.

Worth noting since the start of 2014 I've run 94 autocross events with 629 autox runs, mostly in the Mini but a significant chunk in the Evo, and 3 track days. Driving has improved vastly, and while I'm not nats level I can hop into any car, any setup, and stay in the top 20 in my region. I mention this as driving is still the biggest impact to how the car behaves.

Long answer to a short question, but hopefully it can give people insight/ideas on setup adjustments. For me, I did add the Tanabe FSB to increase push/decrease oversteer, and it worked as expected.

 

Weight transfer doesn't depend on spring rates. Increasing your spring rates doesn't reduce weight transfer, ignoring minor dynamic changes in center of mass height due to suspension articulation.

When you hit the brakes and the car decelerates, load transfer to the front occurs even in completely rigid suspension setups (e.g. karts). For acceleration/braking it's a function of acceleration, wheel base, vehicle mass, and center of mass height. Stiffer springs result in less compression for a given deceleration, but only because the stiffer spring compresses less for a given load. The load transfer is still there even though you don't see as much suspension compression.

This is also incorrect: In steady-state cornering, lateral load transfer is a function of the lateral acceleration, track width, vehicle mass, and center of mass height. You can't reduce that load transfer with stiffer springs or bars (again, ignoring dynamic center of mass height differences).

However, you can influence how that lateral load transfer is distributed between the front and rear wheels by adjusting the relative balance of front and rear roll resistance. Increasing the rear roll resistance relative to the front will make the rear outside tire bear a larger portion of the overall lateral load transfer. The net lateral load transfer isn't changed, though, so that means the front outside tire now bears a smaller portion of that lateral load transfer. The opposite occurs on the other side of the vehicle, with the front inside tire bearing more load and the rear inside bearing less load (or even lifting up in the air).

The Evo is a front-heavy platform, so the front outside tire is naturally heavily loaded in a turn. Increasing rear roll resistance (springs and/or bars) relative to the front is therefore helpful to shift the responsibility for some of that lateral load transfer away from the outside front and toward the outside rear tire. Net grip is increased, not decreased.


TL;DR: Spring rates don't change load transfer. Carefully distributing lateral load transfer between the front and rear outside tires is important for optimizing lateral grip in the front-heavy Evo. Suspensions are difficult.

 

^^ What he said. Only way to decrease weight transfer is lower, wider, or lighter. You need suspension to prevent roll and dive and how much is dependent on geometry.