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Car is 3 wheeling, Stiffer swaybar or up spring rates?
Hey All.
So i got sent the below still from somebodys onboard footage from one of our races. I had numerous people come up to me and go damn your really spinning the rear RH wheel out of the hairpin just past this photo. smoke was just pouring off it. I noticed it seems worse on RH turns.
Sooo my question for the guru's is. Is this a matter of sway bar being too smaller diameter or too soft on the front. Or do i need to add some preload to the bar on the front left side? The sway bars have been neutralised so have no preload currently. and i have the 3 way adjustable mounts on the front for the stock sway bar. its currently on the soft setting. i have ordered a larger diameter whiteline bar. but im not sure if this is going to sort the issue.
The car has never been cornerweighted. just have never had the chance to do it. ive considered maybe upping the preload on the spring on the front left corner of the car or even both fronts as i know it dives quite alot on left hand turns too but i dont think it picks up the inside wheel. im just a lil concerned about mucking all the ride heights up if i start winding preload into the springs and i dont really know how much to wind them. the springs were all dyno tested and set up by a suspension technician when i last had them rebuilt and i havnt touched them since.
Ideally the car probably needs to be cornerweighted but we just havnt got the time at this stage between rounds to do it.
So whats my options.
Also link to the full video: think i appear around the 8 minute 30second mark from behind him as this was a handicap race.
If you're lifting off throttle, thats plenty ok, good even. If you're lifting past mid-corner then you got something funky going on. If you're just spinning the inside rear coming out of corners, then you need more rear diff lockup. Is yours just OEM 8plate?
On the topic of tire lift:
General direction would be raise front RC, increase front springs, decrease rear swaybar. What works for you would have to be determined by you for your needs.
On the topic of spinning inside rear:
Assuming its not just odd setup issue there are a couple things that really helped us. 1st, if the diff is OEM then more lockup is probably needed.
2nd part is less intuitive. If you get the front to do more work, the inside front will spin less and ACD locking up trying to make things 50:50 will overwhelm the rear less. Improving front came from running less camber (fix camber loss issue on lowered Evo geometry), increase caster, and then moving to a 1way clutch diff.
With these changes we went from 1/4" toe-in and med rear bar and still struggling to manage power oversteer in 2nd to 0-toe and big rear bar with the car just hooking and going out of corners. This is with 500whp and 2nd gear with hoosiers. Before the changes, corner exit required much more caution.
tein mono flex coilovers
16kg 14kg spring rates.
sway bar front is stock with the multi hole end brackets that cusco do. On full soft.
rear is whiteline standard diameter on full hard.
has most of the whiteline catalogue fitted on suspension incl RCA and bumpsteer kit. Only a couple bushings r stock eg the spherical on the front A arm. Cusco camber arms rear.
If you're lifting off throttle, thats plenty ok, good even. If you're lifting past mid-corner then you got something funky going on. If you're just spinning the inside rear coming out of corners, then you need more rear diff lockup. Is yours just OEM 8plate?
On the topic of tire lift:
General direction would be raise front RC, increase front springs, decrease rear swaybar. What works for you would have to be determined by you for your needs.
On the topic of spinning inside rear:
Assuming its not just odd setup issue there are a couple things that really helped us. 1st, if the diff is OEM then more lockup is probably needed.
2nd part is less intuitive. If you get the front to do more work, the inside front will spin less and ACD locking up trying to make things 50:50 will overwhelm the rear less. Improving front came from running less camber (fix camber loss issue on lowered Evo geometry), increase caster, and then moving to a 1way clutch diff.
With these changes we went from 1/4" toe-in and med rear bar and still struggling to manage power oversteer in 2nd to 0-toe and big rear bar with the car just hooking and going out of corners. This is with 500whp and 2nd gear with hoosiers. Before the changes, corner exit required much more caution.
so from the footage it appears the car is tipping on turn in and thru the apex. Out of the hairpin it was only just touching the rear right down on corner exit.
my diff is factory JDM spec AYC so i dont think u can just re do the clutches like u can with the USDM ones. Ultimately it needs a cusco rear diff thrown into it or a full RS conversion.
its prob worth mentioning it has a wavetrac front diff also.
My general train of thought from looking at pictures also of the front diving on turn in that i need to increase spring preload on the front? But the question is how much do i increase it by and do i increase it then lower the whole strut down to keep approx 20mm front rake?
Only way to correct the geometry really is to put aftermarket hubs in isnt it?
the cars got 650hp at the wheels so more than enuf power but the handling setup is the achilles heel
tein mono flex coilovers
16kg 14kg spring rates.
sway bar front is stock with the multi hole end brackets that cusco do. On full soft.
rear is whiteline standard diameter on full hard.
has most of the whiteline catalogue fitted on suspension incl RCA and bumpsteer kit. Only a couple bushings r stock eg the spherical on the front A arm. Cusco camber arms rear.
Hey, im certainly not the suspesion Guru, but wonder why your spring rates are swapped heavier front vs rear. Wonder what would happen w/the 16K's in the rear & the 14K's up front
Stock FSB sounds right. Dont need any more rate up front
Also, not many of us track guys running: Tein mono flex coilovers? I stopped my rear tripodding when I went to the Fortune Auto 510's 10K/12K (Swift springs)
Hey, im certainly not the suspesion Guru, but wonder why your spring rates are swapped heavier front vs rear. Wonder what would happen w/the 16K's in the rear & the 14K's up front
Stock FSB sounds right. Dont need any more rate up front
Also, not many of us track guys running: Tein mono flex coilovers? I stopped my rear tripodding when I went to the Fortune Auto 510's 10K/12K (Swift springs)
Dallas will have some better feedback on this
spring rates always been heavier from front to rear as far as im aware? as thats where more of the weight/COG is. even when u look up say a factory set of tein suspension the stiffer spring is in the front. so guess thats where it comes from? Besides the spring only really works in compression doesnt it. so therefore when the car dives thats when the spring counter acts. so the stiffer spring in the front the less the cars going to dive in the front.
Yea be nice to upgrade the mono flex's to some 2 way adjustables some day its def on the cards haha.
I personally am not aware of anyone tracking an Evo that runs more spring rate in the front than the rear, always the complete opposite. I have the same set-up on my car as MinusPrevious, 510's and 10/12k swifts.
I would try swapping those rates around and see how it reacts
spring rates always been heavier from front to rear as far as im aware?
Our EvO's, due to the lever point of the rear shock connection, needs to have the heavier or same rate in the rear vs front. Most all of us run the heavier rate in the rear due to that mechanical advantage w/the rear shock connection point
Also, your rates are definitely on the high end for track work so would not recommend any more sway bar rate front or rear
My .02
Last edited by MinusPrevious; Mar 21, 2018 at 09:31 AM.
Yeah, a more typical setup for stock suspension geometry (or limited change like whiteline RCK) has the rear springs anywhere from 15-25% heavier than the front. Stock springs are right around 20% stiff in the rear vs the front IIRC.
I'm in the same boat as everyone else, got 10k/12k Eibach springs on my Ohlins.
Really though, I'm amazed you're running such a basic suspension on your car. I don't mean it in an offensive way or anything but if I were in your shoes I'd have two (or three if money wasn't an issue) way adjustable suspension before throwing big power or a sequential trans at a car. Good suspension setups are what make or break a racecar.
I don't think I've ever seen a CT9a NOT lift a tire. I run softer springs (10k/9k), Robispec RSB set second to softest, and stock FSB. The car drives great. The tire lifting is just a necessary evil, due to the way our cars are built. I don't mind.
I do have a 12-plate rear diff, though. I didn't wanna deal with peg legging.
thats interesting to hear u all have a heavier spring rate in the rear. everybody down here tracking evos has the heavier in the front. I might have a chat to Ralliart NZ about it see what they recommend.
I dont quite get the logic behind it when most of ur weight is in the front. not saying u guys are wrong it just doesnt make sense to me to have a stiffer spring in the rear when the front is already diving?
ayoustin i hear you. we need a sequential gearbox due to the Kaps gearbox breaking every round. it doesnt appear to be up to the task of handling the power going through it i guess. and Kaps dont want to know about it. so im not really prepared to keep pouring money into a product when the company isnt even interested in supporting you and wants to play the blame game instead of working out their faults. But we wont go there
Its a matter of yes its on the to do list but theres other more important things on the list above the suspension and its on the would be nice to do but whats in there will do the job for now haha. an LSD Rear diff upgrade is also on the nice to have list.
Im confident we can get the car handling better with the struts that are in there its just working out what it needs and getting the setup right. We are in a fortunate position to be in the top 3 fastest cars in class as the car is with a bit of time to play with still so im more interested in refining what ive got for now.
Really interested in hearing some solid evidence and philosophy behind having a stiffer spring rate in the rear when every set of adjustable suspension you buy off the shelf come with a heavier spring up the front?
Its the motion ration of the shocks. In the front, the strut is mounted to the spindle, it's just about a 1:1 motion ration. In the rear, the shock is mounted a few inches up the arm making the motion ratio about 1.2:1, which makes the spring less effective. By have the rear springs about 20% stiffer than the front the effective rate that is acting upon the car is actually the same.
And I know it's all been a long while since most of you have driven a stock evo, but they handle really really well with the rear springs being stiffer than the front. You'll probably have to take a little different approach with your swaybars if you decide to try changing springs rates.
That being said, the car will likely still lift the inside rear
Mar 19, 2018, 05:45 AM
