The Massive Evo That Couldn't

[Loren]

That's all "spring stack math".

Say you've got a 300# spring and a 150# spring stacked. Total calculated stack rate is 100#.

The 300# is 8" tall, the 150# helper is 3" tall.

You have to figure the "block height" of the shorter spring. With a 3" spring, let's just call it 1".

Each spring actually compresses at its own rate. The tender is 150#, the main is 300#. So, if you put 150# on the stack, the tender compresses 1" (and binds), and the main has compressed 1/2". Total stack compressed 1.5" (100# per inch as per the calculation)

So, if we put... 450 pounds on that corner of the car, the first 150# bricks the tender, it compressed 1". 450# on the main = 1.5". Total compression is 2.5".

From there, as you remove weight from that corner, it's ONLY the main spring that extends up to the point that you have less than the "block height weight" of 150# on that corner. Then the tender will start to expand.

So, the real answer... it depends on what spring rates you've chosen and how that relates to the weight of the car.

If you've got it set up right, your typical "dip in the road" should keep you on your main spring. The tender shouldn't come into play unless you're cornering hard (nearly lifting a tire) or really getting light (nearly getting air) coming over something fast.

At the very least, I'd think you'd want the tender to be fully compressed at static ride height. (for off-road, you probably wouldn't... you want that soft "stack rate" to suck up big bumps, and then the stiffer rate to kick in before you risk bottoming out... but that's a different world)

[CaptainSquirts]

I get the whole thing about my current setup having the helper fully compressed at static and comes into play when the main runs out of drop. Part I was more looking to understand is if coming down from let's say a speed bump. Main spring compresses when going over it and then coming down, will the helper ever come into play as you're coming down from the speed bump. The main spring rebounds since it compressed going up it. The helper never compressed since it's already fully compressed, but will the helper rebound a little with the main spring when coming down from the speed bump or is it all the main rebounding.

Now going airborne I see the helper coming into play but how about non air burn scenarios.

[Loren]

Unless you're going really fast over a speed bump, or the speed bump is immediately followed by a big dip, you shouldn't get into droop. The main spring is still overpowering the tender spring.

It's 2018, you could put a video camera on your rear suspension and look at what it actually does. Those videos are always fascinating to watch, anyway!

[CaptainSquirts]

That would actually be pretty cool to see the rear in action and see what it does with both springs. Can I borrow your camera and some duct tape next event. Should be suffice to tape it to the brake caliper since it isn't going anywhere.

[Loren]

There are plenty of ways to properly and securely mount a camera under your car. You just have to be creative.

But, no, you can't borrow my camera.

[Carracer]

That would actually be pretty cool to see the rear in action and see what it does with both springs. Can I borrow your camera and some duct tape next event. Should be suffice to tape it to the brake caliper since it isn't going anywhere.

On a serious note, if you want to use zip ties I have a camera that will fit and it would be fun to get the shot.

[CaptainSquirts]

That would actually be pretty cool to see the rear in action and see what it does with both springs. Can I borrow your camera and some duct tape next event. Should be suffice to tape it to the brake caliper since it isn't going anywhere.

On a serious note, if you want to use zip ties I have a camera that will fit and it would be fun to get the shot.

That would be pretty cool if you're ok with that. Will have to check where a good place to mount it would be. How big is the camera?

[Carracer]

That would actually be pretty cool to see the rear in action and see what it does with both springs. Can I borrow your camera and some duct tape next event. Should be suffice to tape it to the brake caliper since it isn't going anywhere.

On a serious note, if you want to use zip ties I have a camera that will fit and it would be fun to get the shot.

That would be pretty cool if you're ok with that. Will have to check where a good place to mount it would be. How big is the camera?

About a 1.75 inch cube. We should be able to find a place to fit it.

[CaptainSquirts]

Did some more random stuff.

1. Redid my front alignment. My driver front was like -4 camber while my passenger front was low -3ish. My toe was 1/16th toe out. Changed it up so now my front alignment is the following...

-3.6/7ish for the driver side and -3.5ish for the passenger.
Toe is at most 1/32nd toe out. Was shooting for 0 but I got the steering wheel to be centered while driving straight and doesn't feel as twitchy so I'm ok with that.

2. I sanded my rear wing, it was getting pretty damn bad due to clearcoat failing and coming apart. So I sanded it all down, and resprayed some 2k spray max clear coat on it. Also sanded my headlights and cleared those as well with the 2k clear.

No clear/sanded down

After spraying clear

So after letting it sit for a day or so I went to sand the clear since it had some orange peel. So I'm pretty new to clearcoating and dealing with it and I made some mistakes....

So I started sanding the clear with prob like 1000ish sand paper and I was getting bigger scratches than what the sandpaper would do. So I went with a lower grit sand paper to remove those scratches and I was even getting worse scratches! So after research I should've wet sanded the clear instead of doing it dry. So I started wet sanding the clear now, and it was still inducing swirls! More research now.... So the water I use should be lucubrated so I started to use detailing spray and the large scratches were going away which is good. But at this point I sanded way too much trying to fix the large scratches a couple of times so now I am basically down to the carbon fiber again on some spots..... Well I am going to reclear the wing, again..... But now I know to wet sand and lubricate. So it was a learning process . I plan on just reclearing over the new clear I put on which from research seems like its ok to do since its not the failing clear im clearing over.

[CaptainSquirts]

Pic of the clear being sanded through.

Dunno y all my photos I upload show upside down.

[Jamie]

Pic of the clear being sanded through.

Dunno y all my photos I upload show upside down.

Turn the phone over when you take the picture.

[CaptainSquirts]

Pic of the clear being sanded through.

Dunno y all my photos I upload show upside down.

Turn the phone over when you take the picture.

The photos show fine in my device and looks fine on my pc. Once I upload it to fast website it just does flip.

[Loren]

iPhones are good (or bad, depending on how you look at it) at sensing which way is up in a photo, even if you took it upside-down and it's stored upside-down. A lot of places that you then upload the photo will show it in its original stored state.

On a more fun note... your alignment specs warm my heart. "Meh, close enough!"

[CaptainSquirts]

iPhones are good (or bad, depending on how you look at it) at sensing which way is up in a photo, even if you took it upside-down and it's stored upside-down. A lot of places that you then upload the photo will show it in its original stored state.

On a more fun note... your alignment specs warm my heart. "Meh, close enough!"

Makes me wonder since brooksville, we drive up the right 95% of the times if having the passenger side having more negative camber than driver would be more beneficial. You know, since the passenger side is always on the slope end going down.

[Loren]

That's one of several reasons why I like to vary the direction of the turn-around at Brooksville. If we always did THAT the same direction, you might be onto something. But, the rest of the course is typically transition-heavy, so I don't think it would make much difference otherwise.

[twistedwankel]

I paid a local carwash detailer place $45 to do my headlights. It took about 3 months for it to finally harden but they look nice now. You are very ambitious.

[CaptainSquirts]

I paid a local carwash detailer place $45 to do my headlights. It took about 3 months for it to finally harden but they look nice now. You are very ambitious.

I like to detail as a hobby. Tried a couple of times with rustoleum 2X uv clear coat and they failed within a year. Hopefully this other stuff this time around it lasts a lot longer.

[CaptainSquirts]

Okie Doke, so from the last event the car felt fine, no real complaints. I could've been faster going into some key area's by braking a little less. Also adding more speed during the middle of the slaloms at the finish rather than going in, coasting through the 3rd and 4th cone. But watching the rear suspension video of my car, I guess you could see some issues(not horrible but not optimal?).

https://www.youtube.com/watch?v=pb0ett8 ... e=youtu.be

1. Something is limiting my droop. I should def have enough droop from the damper with the help of the helper springs, but doesn't seem like it. So either maybe the helper isn't enough, needs to be a little longer?, Or an arm or arms not allowing enough slack for all that droop, or the rear sway bar might be too stiff and might be causing it to lift the inside more than it should. So I need to jack the car up and see whats going on.

2. I posted the video on the evo forums and a more superb evo autocross commented the following..

"Watching that vid really looks like you're over dampened on rebound in the rear. You can see when it rolls over the tire lifts before it stops moving even. If you go of the notion of being somewhere around 0.65 of critically damped, that definitely shouldnt happened. This would be a scenario where damping is > 1. I wonder if its in feel of trying to compensate for probably needing more rear spring."

So I'm not 100% sure what he meant, maybe someone could chime in to make more sense. But for the remedy my guess is I need to soften up the rear dampers. Now doing so, I probably lose some of that rear rotation(not like there is a lot or anything) if I do do that. So I'm going to try and go from 11k spring in the rear to a 12.5k. Most evo owners are recommended doing a 10k front and 12k rear for more performance over daily driving and I got my coilovers 2nd hand and came with 10k front and 11k rear springs. So I've wanted to get the rear stiffer for some time now. I didn't think 1k would make a huge difference and 2k might be too much so I settled on a 12.5k spring( 1.5k difference in the rear.

My thoughts with stiffer rear springs is that I can lower the dampers some(maybe fix problem #2) and soften up the rear bar a little which might help with problem #1

[Loren]

What he's saying is that while you may have the droop travel that you need, if the shock's rebound damping is too stiff, it's just slowing down the droop so that you still lift a wheel before the suspension has time to droop that far.

You need to do some experimentation to determine if it's that. Or if it's the rear swaybar. Or if it's something else.

Don't go just changing stuff without knowing. You've come a long way with this setup. Figure out what's ACTUALLY happening so that you can apply the correct fix.

As it stands, you've got the car FEELING the way you want it to. It handles great! You're just trying to solve a wheel lift problem in the name of durability. You want to try to fix that without messing up everything else, and you don't want do change anything that you don't HAVE to change. So figure it out.

Jack up the corner of the car to match what's in the video in the "wheel lift" condition. Jack it up "just that much". Is the wheel off the ground? If it is, why? What's holding it up? If you think it's the swaybar, unbolt the end link. Did it fall? Do you now have the droop that you wanted? Okay... that would be a strong data point.

If you jack it up and the tire IS on the ground... maybe jack it up a little more. Still on the ground? Okay... so we DO have droop travel. Nothing is binding. Swaybar isn't holding us up. THAT would be an indication that maybe it's too much damping. That's harder to test. Maybe put the camera back on it... and go full soft with the rear shocks. Does it still lift? That would be another strong data point.

Figure it out.

[CaptainSquirts]

Sounds like a good start.

On another topic, what would help with low speed understeer. Now the cause for me is over driving on low speed corners and that will induce the understeer. Sounds like the fix is obvious, don't over drive it, I get that. What I would like though is change the behavior in that scenario. If I do overdrive, I would prefer it to have less understeer and prefer a more neutral feel so I can somewhat control it with throttle rather than just letting off and hoping the car slows down enough for it to get its grip back or to make it not as bad. I already have a nice chunk of negative camber -3.5, would prefer not to add any toe out, the front sway bar is stock so going heavier would just make it worse. At this point, is the only way to achieve that is to reduce the rear grip?
Thoughts?