Dallas J

iTrader: (1)

Car should be going under the knife this weekend to cut fender. Got behind making parts for everyone else then had to put a bunch of time in making the rear uprights work to test them this last weekend (They are EPIC). Rear uprights had some interesting lessons I had to learn but everything overcome-able with a few custom parts and lots of grinding. But holy ****, its good.

Going back on stands this week and pulling springs to articulate things. Then marking, cutting, welding, sealing all happening Saturday.

V.8MR

iTrader: (6)

I saw your FB post about the rear upright testing. Can you elaborate on how the cars manners changed for the better with these? Also is there anyway to mount up Evo X rear brakes with these? Or maybe put evo 8 front brakes on the rear of the car?

Dallas J

iTrader: (1)

I changed a couple things this winter so I cant say 100% the benefit was all in adding the rear uprights, but I think the rear uprights played a major role in how things changed.

Last year I tried a bunch of things to make a setup work without the front swaybar but it seems I just fought the car all year to handle well. It just never wanted to turn well, especially when it came to higher steering angles. When we did get the car to actually rotate, it would never maintain any amount of yaw. Instead we got some slide but then just grab which is not what we want. I tried 900/1100, 900/1200, 900/1450, and 900/1650 all with a WL 26mm rear bar. It took basically the 1650 to get the back of the car to start moving but at that point it felt super numb. Both in steering and rotation I just didnt feel that connected to the car and it felt like it had way less spring than the rates would indicate. Not awesome at all.

So I came to the conclusion that it appears you really need some amount of front bar to make the rear bar more effective. Hard to explain completely, but its at least what my gut is telling me. I went back to the math and looked at old good setups and came up with a plan for spring/bar balance. I decided on around or just under 3hz front, about 10-15% higher in the rear. And bar stiffness would account for 15-20% of total roll up front and 30-40% in the rear. I would leave the front mostly alone if I was happy with roll angles, and adjust rear swaybar based on corner Mid-exit and rear springs based on corner entry-mid.

Rear uprights made a difference in RC height of about 1.5-2" (not a ton overall) and reduced the camber curve back to under 1deg/in. If you lower the rear of an Evo down to the top of tire flush with the fender, the ramp rate of camber gain is getting pretty steep and the rate of that rate is climbing fast. I moved it down as far as I could (only 1.25" because axle becomes a clearance issue) but that puts us in a much happier place.

Ok, so how did it all work. I went out on first run with the intent on not being too aggressive but looking to get a feel for where the balance was. By the first real turn I was completely shocked. Front of the car absolutely darted in on steering and back of the car swung reaaally wide. I completely expected the opposite on cold tires (It was about 32 deg outside). But I just countersteered and stayed in about half throttle and carried through on line into the slalom. Average person would have considered it a big slide but in this case I just powered through like it was NBD. The rest of the event was just getting use to how well the car would turn in, how much grip I was getting on the tiny 265 RE71s, and how playful the back of the car was.

The comments of others really stood out to me. Several people mentioned on this increasing then decreasing radius turn that I had an epic power slide through the whole thing but in car to me I did absolutely nothing. I could feel the car rotate, but it never felt like sliding and I never corrected for it. The car just did it and didn’t care.

If the car handles similarly on race tires, I don’t think I’ll change a thing all year. But I suspect the rear will gain more than the front due to tire/weight ratios when I switch to 315 A7s. So I plan to carry 100lb greater springs just incase, and will play with pressures for balance if needed.

kaj

iTrader: (60)

Sounds like that particular setup may be a bit "twitchy" for road course stuff...?

Dallas J

iTrader: (1)

I would guess if you drove it well, it wouldnt be twitchy at all but if you move the steering wheel at the same rates as we do in AX, its probably going to be less tolerant to hamfisting. Though rear wing will probably do the job to keep it settled. Im thinking of swapping to the WL24mm bar since its stiffest setting is basically same as 26mm softest setting. For track, then I can just start at soft on the rear and go from there.

Mid corner, I would expect it to be pretty awesome though. Lift a little to tuck things in or scrub speed, throttle more to open things up.

But I am probably much stiffer than most you track guys in general. So my car is faster being twitchy in the sub-70mph realm.

Construct

iTrader: (4)

So the rear uprights have about 1.25" of correction relative to stock ride height? How does that compare to how much you've lowered the car?

I haven't seen a stock ride height Evo in so long that I can't really remember what the stock ride height looks like. I need to re-measure my current ride heights when I put the car back together in the next few weeks.

kaj

iTrader: (60)

Yeah I was referring to the entire setup. So for the track, just dial back some spring and bar and end up with the same-ish results but at 100+mph LOL. It sounds good to me. I look forward to testing being done. By then, I'll hopefully be able to star collecting your stuff. Would you say the front or rear seems to be most beneficial to start with?

Dallas J

iTrader: (1)

Best we can figure from stock pictures and research, about 1.75-2" rear and 2-2.5" front. Factory has a bigger fender gap front than rear and I want the front as low as possible. But 1.25" limit is reasonable to give a bit of rotation (less roll moment, a bit less slope in the roll axis) without needed quite as much spring. Going more than that has big effects on things like droop travel since you can basically think of everything in the suspension staying at one height but the wheel moves up 1.25". It really is more along the lines of a drop spindle than the front since the front doesnt effect the ride height.

Absolutely need the front first. Front fixes the grip lost from needing huge rates to control roll and camber loss. Also has huge effect on corner dive that increases the inside rear lift. So the car rolls much flatter. The rear is more like adding back in more rotation and balance. Its seeming like the result is a more controllable and predictable rotation with better feel.

Doing both takes the car more back to its roots of what made the evo great. Both grip and rotation with all the feel and poise we love.

kaj

iTrader: (60)

I'm sold. 😂

V.8MR

iTrader: (6)

Yep me too, just need to convince the wallet to give me money.

V.8MR

iTrader: (6)

How about rear caliper options?

Dallas J

iTrader: (1)

Only plan right now is OEM rear brake. Trying to use front caliper there would be problematic with the 50% reduction in piston area. Not sure what you'd do to correct that part. But in general, any that works with OEM should work with these though there could be some unknown clearance needed.

The rear upright is pretty complicated to get everything right. And with the lower mount moved 1.25" you need enough droop adjustment in the rear shocks to accommodate things. On the flags I had to flip the control arms to get an extra 0.75" on droop (yes, you can flip the control arms for droop but only if you need more droop or you can run into interference issues).

Construct

iTrader: (4)

Would Evo X rear calipers fit? The mounting holes are in slightly different locations, but it's close enough that someone here re-drilled the holes slightly off-center and made it work.

Dallas J

iTrader: (1)

Hard to say, If I knew what it was I might be able to elongate one side of the holes or add material specifically for someone else to do. In my case, I have no intent to run anything other than OEM rear brembos with the wilwood superlights so I dont have the parts to make that check.

V.8MR

iTrader: (6)

If I get a set, would you be willing? The only unknown is the rotor and ebrake setup. Not sure if its compatible/direct swap. Also does anyone know exactly how much bigger the Evo X rears are over CT9A?