Suspension Setup/Understeer Issues

[Talesin]

At the moment, I'm interested in setting up my 1Ga for autocross. But I'm running into a number of issues. Handling modifications are as follows:
-KYB AGX 4/8 adjustable shocks (running 2/4, 115% factory stiffness, problems persist up to 4/8, 223% factory stiffness)
-B+G lowering springs
-Manual steering rack conversion
-Front strut tower bar
-225/45/17 Riken Raptor ZR (though the problems still happened with Eagle F1 GS-D3s) on Tenzo RS-5 17x7" rims @ ~35psi, no spacer plates


Even following a proper line, I end up with a very significant amount of understeer. Also, on low-speed hairpins, the back of the car will 'hop' outward.. rolling over, then losing traction for a moment.. literally jumping sideways. I can only attribute this to body flex, and a lack of a rear strut tower bar.
Also, the manual rack is extremely hard to turn, even at speed... occasionally it will have three or four turns in it that are almost effortless, before I have to start muscling it around again. I can't find any loose brackets, and the wheel-shake test says that the tie rod ends and wheel bearings are good. I've had the chance to drive a manual rack 1.8L Eclipse, and could easily turn the wheel one-handed, compared to the two-handed hauling neccessary with my vehicle. I've also verified that it is not just a power rack with the lines removed.

So far I've only been able to compensate for the understeer by turning the wheel to full lock in the direction I'm turning, and going to WOT. This wears my front outer shoulderblocks pretty harshly though. Stiffening the rear shocks and setting the fronts extra-soft doesn't make a noticeable difference either. The 'hopping' can't seem to be helped, and almost brings the car to a full stop when it occurs.



So. Does anyone have thoughts as to what should be looked into? I'm already planning on picking up a rear STB, to see if that'll help reduce or stop the hop. The steering heaviness and understeer is definitely frustrating though, and I'm very tempted to switch back to a power rack, but would rather not give up the extra engine bay space, and increased road feedback.

 

[RamenPride]

bump up your tire pressure.

 

[SAKONE]

Try actually switching it around stiff/soft (f/r). I have that problem with my 2G, but it just depends on the way I adjust my coilovers. I read somewhere on this section of what causes that on a 2G, but not a 1G. My friend runs a 1G (GSX), but never mentioned that problem. He runs aftermarket sway bars front and back. It could be tires, it could be the way your driving, it could be just the car.

 

[Talesin]

As I understood it, softening the rear end was a way to compensate for oversteer; to reduce understeer, I'd always been told to stiffen the back and soften the front as much as possible. Would make a bit of sense, as when I bought the car, the previous owner had set it to 3 up front, and 1 in back.. I'd assumed it was to promote understeer and soften the ride while I was test-driving it, but I'll give that setting a shot once the head's back on and broken in.

Also, was told to keep the tires as soft as possible, without letting the sidewalls fold over while turning... did the shoe-polish stripe to work out my current pressure. Given that stock pressure is 30psi, I'm already running raised.

Can't afford new swaybars at the moment, unfortunately, though I might be able to afford the urethane swaybar bushings. Couldn't hurt, at least.

 

[drivemusicnow]

The rule of thumb is to stiffen the opposite end as the one that is sliding. So if you're oversteering, stiffen the front, understeering stiffen the rear.

That said, I think the solution to your problem is a rear swaybar. I would also try removing the front strut tower brace and seeing if that makes it better, or possibly worse.

Do you happen to know the spring rates front/rear of your springs. That information is neccesary to know how it is setup right now. What are your camber/toe settings right now, and can you possibly get more negative camber in the rear?


For the rear hopping, you just need a tire with a stiffer sidewall. Flexible/larger sidewalls tend to do that "folding over" thing. I would probably run a bit more pressure in the rear as well to try and compensate for that.

 

[Talesin]

Figured as much; as I said, I can't really afford an aftermarket rear swaybar at this point.

Also, I was incorrect... I don't have B+G springs, as the receipt I received with the car indicated. Instead, I have a set of H&R N/C springs, part number 52961. I can't find spring rates listed on their site.

As for sidewall folding, as noted above I run them with enough pressure to avoid that. With 45 aspect ratio sidewalls, I'd expect it to be less of an issue. The understeer is still killing my front shoulderblocks... if I don't figure out how to get rid of it, I'll either have to drive a lot slower (frustrating thought) or go through a new set of front tires every few thousand miles.

 

[jtmcinder]

The rule of thumb is to stiffen the opposite end as the one that is sliding. So if you're oversteering, stiffen the front, understeering stiffen the rear.

The rule of thumb assumes that you have (close to) proper camber and that is not true here. He needs to raise total roll resistance in any manner possible and/or get a lot more front camber from crash bolts and/or camber-caster plates.

- Jtoby

ps. the idea of dialing in steering lock and hitting the gas is just plain crazy, but in this forum we should (try to) stay focused on the suspension

 

[Talesin]

I'm assuming that 'proper' camber is significantly different from stock camber; I had the car manually aligned to stock spec, though I'll be the first to agree that an extra couple of degrees wouldn't go amiss. I've been considering picking up a set of camber plates from RRE for a while now, but given that $160 for a rear sway bar is just outside my current budget, $290 for camber plates is even moreso.

And curiosity speaking, why is that 'crazy'? Bad habit to fall into, I'm guessing. Honestly, even if the car didn't understeer (making it neccessary), I'm not sure I'd be able to muscle the wheel over enough with the manual rack.

 

[jtmcinder]

You can't "muscle" a car through a corner by cooking the fronts, especially with a lousy or open front diff. You'll just push more and trash your tires (as you are discovering).

You want (at least) -2* of front camber for autocrossing. And you want some "real" springs, not lowering springs. A 1G needs 350/350 or more to keep the tires happy.

For now, slow down and make sure that you only feed in power as you unwind the wheel. Think of your hands and feet as connected. As you hands straighten the wheel, your right foot adds power.

- Jtoby

 

[Talesin]

Not easy to do, when most of the turns would be rated on the street around 15-35mph, and to be competative you're expected to handle 45-50mph average. Can get through easily enough at a cruise-controlled 35mph without understeering, but at 40 a lot of the turns are just too sharp, even with a good line.

I'll look into the springs; for the moment, I may be able to work the rear swaybar into the budget. Probably going with a Suspension Techniques bar from RRE, or Summit if shipping is cheap enough. The camber plates are out of the question though, for the moment. Have to re-do the head, so while it's off I'm taking the opportunity to pop in a few upgrades.. lifters, springs and retainers, ARP headstuds. Still waffling on replacing the cams while everything's apart.

In any case, do you have a suggestion for springs on a 1G, for the future? The H&Rs are listed as 'firmer than stock', but I'm guessing that's mostly to make up for the reduced travel. It's irritating not to be able to find the rates for these anywhere. I'd obviously prefer something at least semi-comfortable on the street, though doubt that it'd be possible to have much worse a ride than these H&R seem to provide.

As a side note, there really seems to be very little body roll.

 

[SAKONE]

You should've mention the other thing about your front sidewalls getting wrecked. Your probably looks like mine since I was screwing around cone-dodging and trying to do what you were doing my muscling it around a turn at almost full throttle. It's not gonna work, your thinking RWD. The only times it did work I used less grippy tires and was able to "slide around" easier instead of grip (the surface was asphalt but had some gravel).

 

[Talesin]

Heh. Actually, I've never driven a RWD vehicle aggressively before. I'm a bit nervous, and don't want to borrow a friend's, as I've become convinced that I'll end up oversteering it and slamming into a wall or something.

On the up side, I've decided to pass on the FMIC, springs/retainers and cams for the moment. Putting power before control is a little like slapping a body kit on before switching out to a smoother flowing exhaust, for my purposes. The money would be better spent on getting it to handle more nimbly.

Besides, a rear swaybar for $125 from Summit, camber plates for $290 from RRE (ps: if anyone knows of less expensive ones, PLEASE chime in!), and a rear STB for $89 from RRE would be cheaper than buying a new set of 264/272 cams. Plus, I can save up and do the rest later if I still feel it neccessary, at the next timing belt change.


I'm still seriously funked out by the heaviness of the steering though. Does anyone have ideas on what could be making simply turning the wheel such a problem? I've been driving a friend's Corolla FX while the GSX is down, and can very easily steer its manual rack with just my palm, even in sharp cornering. The only things I can imagine would be my wider tires, or a very bad, large scrub patch from somewhere. And it isn't the wider tires, because the Mirage's are only 10mm narrower, and it handles just as nicely as the Corolla.
Just to be on the sane side, does anyone know off-hand where the pivot points are supposed to be measured, to get the scrub? For all I know, I might need *more* of an offset to get it lined up properly with the wheel's centerline. Which would be an incredibly easy and stupid fix.

 

[pneumo]

Instead of camber plates, you could get some eccentric bolts for the lower front strut mount. They are usually about $30/pair and give you 2 degrees adjustment. Since you'll need to do an alignment after you install the bolts you should set the front to about 1mm toe-out, maybe less if you're on a higher speed course, more if you're on a low speed course.

The front steering axis goes through the upper strut rod mounting bolt to the center of the lower balljoint on the control arm.

Do you have a stock front diff? Or is it a LSD of some type? The reason I ask is because a front LSD can make it really hard to steer with a manual rack IF your center diff is locked up. One symptom of a locked center diff is the rear wheels will skip when you make a sharp U-turn.

 

[Talesin]

Thing is, with the camber plates I can add a degree when I get to the track with just a jack and about two minutes per side. Eccentric bolts would take a lot longer and a lot more futzing to get exactly right on both sides.

I really don't think I'm to the point where I'm willing to toe-out past stock spec though, sacrificing freeway stability and nuking my tires faster. Maybe if it was a dedicated track car. Given how soft the back end is, I'll keep it in mind though if swapping out the swaybar and adding a STB still don't give the amount of handling result I'm hoping for.

I've got the factory LSD option, even after about a year I'm still not sure if it's the front, center or rear. The back end will skip when taking a sharp U-turn at decent speed, but will not while simply turning around at about 5-15mph. But the steering is heavy regardless of how sharp I turn. One of my friends with a GS-T had commented that it's worse than when his PS belt had snapped.


Again, anyone know how to measure the turning scrub patch on a 1G, or have thoughts on what might be causing extra-heavy steering between 15-45mph?

 

[jtmcinder]

Thing is, with the camber plates I can add a degree when I get to the track with just a jack and about two minutes per side. Eccentric bolts would take a lot longer and a lot more futzing to get exactly right on both sides.

If you had a car with the steering rack in the front (like a WRX), I'd say this was a great plan, because you get the camber and some toe-out, too. Problem is, our steering rack is behind the front axle, so when you slap the camber plates to negative, you dial in a bunch of front toe-in. And autocrossing with front toe-in gives away too much. So you have to learn how to adjust toe at the track, as well.

- Jtoby

 

[Talesin]

Crap, you're right. I hadn't actually thought about the steering geometry like that. Which makes buying a set of plates a lot less appealing. I mean, setting toe is just altering the adjustment sleeve on the tie rod ends, but hell if I'd be able to do it accurately myself once I got to the track. Only way I can think of would be measuring the front and back of the front tires, but the rest of the car is a little in the way. Suppose I'll have to make do with a set of eccentric bolts (whew... cheap, comparatively!), and a little more daily inner edge wear than I'd like. Maybe compromise and just add an extra degree or two over stock, assuming stiffening the back end and pulling the front STB aren't enough to compensate for the understeer.

Though with the outer shoulderblock wear, negative camber and higher pressure would at least move it back to using the full tread for grip, rather than just the outer edge as it appears to be currently.

Still no ideas on the heaviness of steering?

 

[SAKONE]

I think it has to do with your tires widths with the steering problem you're describing. Also that's a FWD car and your reacts differently with the AWD. That's all I can think of aside from driving you car since one person idea of heavy might be different than another persons.

 

[mavisky]

I'm no suspension expert but here's a couple issues I see.

-Shock settings. I get the best out of my Eibach/AGX setup at 1F/6R it seems. But I've also got the Suspension Techniques rear sway bar and front and rear strut bars in my car as well.

- Tires. No bigger handling difference can be made than switching to quality tires. I run 205/55-16 falken rt-215's or 225/50-16 Khumo V700 Victoracers.

- Manual steering rack. The problem is that you don't have a manual steering rack, you've got a power steering rack without power. I'm not sure why you did this, but I'd advise you either reverse that "modification" or actually switch over to a 1.8 manual rack.

You can see that my car with Sportlines and AGX's (which dont' bottom out on course miraculously) rides pretty level during transitions although it does hike the rear inside leg at times. She needs more spring rate though, but I'm working on that.

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Video
http://www.youtube.com/watch?v=Um4Wxf6yurs

 

[Talesin]

I may have to let you do that, Sakone. And yes, even though they're just 225s, I suspect that with the RS-5 rims, my offset may be resulting in an overly large scrub patch. If I can figure where the scrub line is compared to the tire centerline, and if it's negative scrub (scrub line outside the tire centerline) then I can reduce it with a couple of spacer plates. The rims have a 42mm offset.

Mavisky, thanks for the setting tip, I'll give that a shot.
Tires, I was running Eagle F1 GS-D3. Best tires I could find that weren't classified as comp tires. High speed corners they'd hold incredibly well, with a very defined noise-point, though a sharp breakaway when they finally did cut loose. The Rikens hold almost as well, but give a constant squeal that makes it easy to tell exactly where they are. They also break away smoothly, sliding little by little rather than all or nothing.

I am running a 1.8L manual rack, NOT a PS rack with no lines. I've looked. There's no place to hook up the PS lines. There's no actuation cylinder. The steering is still heavy as all hell.

 

[pneumo]

Scrub radius- how about this? Drive to a dirt lot, clear away any rocks so your tires are resting on clean dirt, with the car stopped turn the steering wheel completely from left to right and back, draw a line in the dirt along the outside edges of the tire so you can see how wide they are, then carefully back up and look at the marks in the dirt. You should be able to see where the center of the steering axis is located in relation to the width of the tire.

 

[Talesin]

Hmm. Might work, though it'd have to be very carefully done, dealing with millimeters.

Can probably just calculate it out, if anyone knows the stock tire size and offset. Been looking around, but have just found stuff about people asking if they can fit 20" rims on their car. :b

...actually, I just looked around and found the stock offset. +46mm. And the RS5s at +42mm. Though that still doesn't account for any alteration with the H&R springs on the front. Supposedly a 1" drop.