Understeer!

[TurboProject]

Well I've been slowly/progressivly modding my car since I got it back in 1999. First I did a lot of suspension mods because that was quicker than engine mods. The past few years I've been focusing on engine mods(IE: turbo, stand-alone EFI, etc). But now I think I'd like to revisit some suspension stuff.

A lot of my suspension mods were done under some ignorant assumptions.

One thing I've noticed that is bad with my car is that it has a huge tendancy to understeer on the street. I have a hard time taking a hard corner at 30-40mph w/o just slidding across the pavement and heading stright for the outside curb of the turn. I'd like to reduce this tendancy.

I'm going to list my suspension mods/set-up and perhaps a knowledgable person can shed some light on to what I can adjust to make this better.

Suspension/chassis mods to stock 1994 V6 5-spd camaro:

-17"x9" SS rims
-275x40x17 Kumho ECSTA Supra 712 tires(I've run these since I got the rims and have gone through a few sets)
-Take off Zexel carrier from SLP
-Adjustable Tubular Panhard rod w/ poly bushing on one end, adjustable link on the other from TByrne Motorsports
-Tubular LCA's w/ poly busings from TByrne Motorsports
-Hotchkis Sway Bars with poly mounts/end links(the big ones: 1"-7/16"(36.5mm) front, 1"(25.4mm) rear)
-Take off Z28 springs and shocks from SLP(to my knowledge the Z shocks are same as stock V6)
-Stock Torque Arm
-1 piece steel driveshaft
-Poly Torque Arm Mount
-Poly transmission mount
-All poly bushings in front

-The alignment is pretty much to factory specs as I had a shop do it for me a couple of years back.


Now I've been reading that too big of sway bars can actually be a bad thing. I just bought them at the time under the impression that "bigger is better".
I just set the adjustable panhard rod to the same length as the stock one. I've never tried to see if the axle is centered or not.
I may need to check out my pinion angle if I didn't shim the shorter poly trans mount enough.

I realize not all these things will affect understeer but I figured maybe someone can help point out some obvious flaws in my setup.

I mostly drive on the street so I'd just like a nice compensating setup that won't understeer under hard cornering and as long as oversteer can be controlled w/ throttle then that would be fine. Ride comfort isn't a concern but longevity is since it's mostly a street car...but so far everything has been wearing just fine(except maybe the tires).

Thanks for the help!

[TurboProject]

Re: Understeer!

Oh yea...also my steering jumps around a lot when on bad roads w/ a lot of high/low spots. But I've always just attributed this to the 275x40x17 tires since it showed up after I changed to this. Is that something people with this tire size just live with or is there something that can be done to give the car more control(other than gripping the steering wheel tighter :-P ).

[Camaro Dom]

Re: Understeer!

well, it'll jump around on you cuz the suspension is really stiff. theres a reason why offroaders have those huge suspension travels (its not just ground clearance).

alignment has to be done every 6 months of normal driving. if you're taking corners at 40mph i'd say you are seriously overdue.

z28 springs are the big thing that stick out in my mind. remember that the 8's are carrying alot more weight up front so those springs are alot stiffer. in order to corner correctly, you should give the brakes a good pump to make the car squat forward to put more weight on those tires so you can get the traction and lose the understeer. if the springs are to stiff (and i suspect they are) they wont let the car squat properly adn you're not getting enough weight on those front tires.

if that still doesnt work then the next in line would be those big ol' swaybars as far as i can see...

are you really running 275's on the fronts? i dont understand how you dont have a fitment issue unless you cut out some of the fender.

[TurboProject]

Re: Understeer!

Yup, 275s all the way around. I've never had much of an interference issue. I don't hear them rubbing. The only sign I've seen is a very light 1" square patch on the plastic inner fender lining that is lightly rubbed, but I've run these tires since ~2001 and that area just looks a little polished and not cut down. And the tires never show signs that they're rubbing.

I wonder what the engine weight difference is btwn the LT1 and 3.4 V6. The turbo/intercooler added an additional 20-30 lbs. But I've also mounted the battery in the rear. I've got an oil cooler up there which doesn't add much. I'm working on a custom set of headers that is made of some pretty heavy material which will probably add another 20-30 lbs to the front. Although I'll also be running a tubular crossmember and a mini-starter. Do LT1 guys run into problems with too much stock spring when they switch to tubular crossmembers, and tubular upper and lower A-arms? It seems like that would shave off a lot of front-end weight.

If Z28 springs are too stiff, then are all these guys running lowering springs running springs that are too stiff? I thought ebach and other V6 springs were stiffer than stock Z28 springs. Are stocker V6 the way to go with just better shocks?

[Camaro Dom]

Re: Understeer!

eibachs are designed to have a progressive spring rate (gets more and more stiff as travel goes on) and to lower ride height which lowers center of gravity. lower COG means that the weight of the car is distributed more evenly across all 4 tires (thats y suv's flip). Figuring out your ideal spring rate is kinda touchy obviously. you cant be too mushy (think of cornering with a Lincoln Continental) and you cant be too stiff (the suspension wont squat on the front wheels)
you've got a little bit of weight up front (those suspension parts are all unsprung weight which doesnt matter at all except to draggers) but from the looks of things you're just kinda canceling the weights out (turbo in, battery to the back, headers in, cast iron exhaust mani comes out..).

the best way to go is to jump in with the aftermarket. those springs are tested and reviewed and engineered so that they try to hit that sweet spot. if you want racing springs, you can get them but your wheel will jump around more. like i said, it all boils down to ideal stiffness given your car's weight and COG. (well tires and swaybars matter too but it looks liek you got that on lock :D)

[Vracer111]

Re: Understeer!

I wouldn't run a tubular K-member if I were you unless the ONLY THING the car is for is drag racing. Tubular K-members will fail under years of constant street use and hard track use as well. The stock K-member will hold up a lot better than any tubular K-member, which is the reason all unit-body required series roadracers have been using the stock K-member.

I guess the only thing that could really cause understeer is the Z28 springs as since the rates will be higher and the car probably sits a little bit higher than stock in the front. I have Hotchkis sport swaybars, stock V6 springs, Koni Sport SA dampers, adjustable panhard rod w/spherical bearings, adjustable lower control arms w/ spherical bearings, and 17x9.5 Z06 replica wheels with 275/40-17 Nitto NT-555RII tires all around. The car has been lightened and weighs 3240lbs with full tank. No understeer with that setup - it turns right in under braking and has corner exit oversteer (on a smooth racetrack - steering is really sensitive on bumpy broken up roads which is why on the street it has the stock alloy 16X8 wheels with 245/50/16 Yokohama ES-100's at the front). The Hotchkis rear bar really makes it sensitive and IMO requires adjustable rear shocks to control the stiff rates on stock V6 springs not to mention sticky rear tires help keep the rear end planted as well. To me the Kumho Ecsta 712 tires are not an acceptable tire to put on a car meant for handling. They have a little better grip than the poor performing stock tires and OK transient response; that's not really saying much. If you want a good Kumho street tire the Ecsta MX is where it's at. The Yokohama AVS ES-100 are also pretty good, though not quite as good as the Ecsta MX. The both are around $125 a tire verses the $106 for the mediocre Ecsta 712's.

[MrCoffee]

Re: Understeer!

what about the basic front STB and some subframe connectors? Or a RS steering rack

[Vracer111]

Re: Understeer!

you've got a little bit of weight up front (those suspension parts are all unsprung weight which doesnt matter at all except to draggers) but from the looks of things you're just kinda canceling the weights out (turbo in, battery to the back, headers in, cast iron exhaust mani comes out..).

Unsprung weight is more important for handling (autocross and roadracing) than straight line drag racing. The less unsprung weight you have the less force you have acting against the chassis under cornering - which means it will upset the chassis less.

[TurboProject]

Re: Understeer!

I wouldn't run a tubular K-member if I were you unless the ONLY THING the car is for is drag racing. Tubular K-members will fail under years of constant street use and hard track use as well. The stock K-member will hold up a lot better than any tubular K-member, which is the reason all unit-body required series roadracers have been using the stock K-member.

Well the makers of the crossmembers claim they'll work for daily driving:

http://www.spohn.net/product.cfm?productid=1617

http://paracing.com/product_info.php...ef82601a54e994

The one I have is the PA Racing one. The reason I'm running it is to add more clearence for the headers/turbo pipes.

But I guess anything will fail given enough stress and cycle time. Has anyone actually heard of a tubular crossmember failing on someone on the street other than in an accident. I would expect to sustain a lot more damage in any type of frontal crash since there's just not as much meat on the tubular crossmember compared to the stock boxed in style.


Yea, really the only reason I run the Ecsta 712s is because they're the cheapest in that size and they seem to last reasonably long when compared to some expensive goodyears or the like.

[TurboProject]

Re: Understeer!

Oh, and taking corners at 40mph is probablly a little of an exageration. There's one corner that I take daily on my way home from work and I have to crawl through it at <20mph or it'll slide. But I guess that has a lot to do with pavement conditions. But I'd say I still understeer more than it seems it should.

[Vracer111]

Re: Understeer!

If the roads are good where you are at there shouldn't be any problem with lightweight tubular K-member. It's when the roads aren't in good condition and it's daily driven that I wouldn't trust a Non-modded tubular K-member.