It won't be long now, and the warmer Indiana days will be back so I can drive my IROC again. But these last 3 years I've been trying to track down a handling issue.

First off I will list the stuff I have done...
Front end
1.) Energy suspension poly bushings
2.) Moog steering linkage and tie-rods (except a new off brand idler arm)
3.) AC Delco replacement struts
4.) MOOG H/D ball joints
5.) replacement upper strut mounts (with bearings)
6.) MOOG sway bar bushings and end links
7.) New wheel bearings both sides. (factory brakes)
8.) Eibach sportline lowering springs
Rear end
1.) Founders non-adjustable lower control arms
2.) JEGs adjustable pan hard bar
3.) Factory torque arm with energy suspension poly mount
4.) New axle bearings
5.) AC Delco replacement shocks
6.) Eibach sportline lowering springs

Now... I only use this car for cruising around on the weekends. Absolutely no racing or track days what-so-ever. So I wouldn't think that the hodge-podge of parts I have put into the suspension would be the culprit of my handling issue. I have had the car aligned once every year after I put new parts on.
But for the life of me, the car handles extremely erratic on crappy un-even pavement at highway speeds. I can stay in city limits at 40mph or under and drives like new, or if it is nice new pavement I can run as fast as I want. With no loose play in the steering wheel.
I normally run my C6 corvette 18/19 combo with a 2" adapter on front and a 2.5" on the rear (factory 3rd gen rear). But when I first put the wheels on I never noticed this issue, until I got it aligned the first time(but that was before lowering, only aligned because I changed steering components).
I put my stock 16" IROC's back on and the problem isn't as bad, but still exist. However I have a set of 215 width tires on them. So they are not as wide as the stock size.

I've only thought of a couple different things that I can think of it being. First being that the alignment shop does not know how to do anything but put it at the factory specs. Second being that the only two things that are not new (steering box, and steering shaft) need changed now. Or third I'm thinking maybe it's just the overall track width of the car being to wide and following the uneven pavement.

I'll have to see if I can find the spec sheet from alignment the last time, to see what they set everything at. But I told them that ever since they did it the first time the car follows every rut in the road going over 40mph, but drives fine in town. They checked through everything before they worked on it this last time. Only thing they could think was possibly the steering box could be wore out (but I have no play in the steering. It is just erratic).
And I went and measured my width on my car. I am at 70" front outside to outside, and 72" rear outside to outside. I thought maybe if I got some spacers and narrowed the front some more it might help?.?.

Overall goal is I just want to safely drive my car to work, and haul the family in for cruise-in nights this year. I haven't even went to a cruise-in for 2 years... everyone keeps asking me if I still have the car..

 

maybe try a different alignment shop?

 

Wider the tires the more you will fight the uneven road. I have sportlines they seem fine for normal driving but when push comes to shove in the turns they just don't cut it. Look into the jegs panhard bar relocation bracket goes on the driver side of the rear. But I would look over your steering shaft and box for play first.

 

I'm 99% sure your alignment sucks.
Factory specs are way off for performance usage and/or wider tires.


If you don't specify the settings, you get factory.
Positive camber & low caster gives you a car that wonders around with wide tires.


Do a search on performance alignment specs on this site. You will see the difference from stock.

 

I have 275/40/17 on all 4 corners and have the performance alignment specs and the alignment did nothing for me. The only place I have made a little ground on fighting the uneven road was when I upgraded my steering shaft it helped but didn't fix it.

 

Larger tires are probably the main culprit.

This seems to be a common complaint.

Craig

 

Yea, I think I'm going to ask around and see if there is any place around my area that has an experienced alignment tech. I trust the guy that owns the shop I had been taking it too. But I have no idea who he has running the rack. He can... but he doesn't get paid to physically work now. LOL! It might be a conspiracy theory... but he has a 2002 vette and he always tells me he'd like to have my gunmetal rims.
And I thought about seeing what kind of narrower 18" tire I could get by with on the front. I have a pair of Bridgestone Turanza's on there currently. I'll check my steering shaft out this weekend. And just for the sake of simplicity... I've been contemplating putting a manual s10 steering box in. Because I'm not sure which way I want to go on the engine later (possibly single turbo 350, or BBC). But that'll be years down the road.

 

I forgot to add. My steering linkage from tie-rods to the center link look like this now...
\_____/ (not too that extreme lol) instead of /-----\ So I've wondered if lowering has changed something in the steering articulation. I wouldn't think a bump steer kit from Baer would help. Plus, I'm not even sure if it'll fit between the spindle and the inner rim. It looks to have a bout an inch clearance currently with the MOOG tie rod ends.

 

i doubt the tie-rod to center link angle is an issue.

one thing you might do is, put a dab of paint on all the adjustment points. when you pick it up, you can tell if they ever actually adjusted anything. i did it once and the never put a wrench or socket on anything. very bad experience and the last at that shop.

 

I've has 275/40's on mine for years & it handles fine. On very bad roads (with low spots from truck wear) it does wonder a bit, but nothing that ever concerns me at any speed.

 

I never really put much thought into it until I drove my car yesterday and when I parked in my garage I heard a heavy rattle sound. Almost like my exhaust was lose and was touching my rear panhard bar...
I looked at it tonight and started to shake the car to find out what was loose. And I'm getting a pronounced metal thud from my axle at the hub. Especially on the drivers side. If I rock it and put my hand between the rotor and the rock shield I feel movement.
The cars rear has always whined when I take a right hand turn while deceleration. But never made any noise any other time. I did put new axle bearings and outer seal in last fall. I checked out the carrier and didn't see anything wore out. Anyone think it might actually be something in the rear end causing my issue?
I found out also that my rear clutches are not burned out... Some one put a regular one wheel peel carrier in there. I've heard of c-clips wearing out, but I looked over everything and didn't see anything that I would think would be wore out. I would've changed the bearings on the carrier. But I don't have the equipment to do it, and I was afraid of not getting the ring and pinion set up correctly.

 

Try these specs, they work great for me. 3/32 toe in is crucial, zero toe or toe out can cause your issues. Use plenty of caster to help the wheels center, but very little camber for the street, maybe just a touch of negative camber. To much camber can cause the darting and wandering.

 

How wide are those Corvette tires/wheel combo that you run?

You have Sportlines with stock struts and shocks. Konis are the only strut/shock that I know that can handle the low spring height of the Sportlines. Anything else is going to suffer from lack of rebound. This leaves you with the choices of either
a) ditch the Sportlines for a less lowered spring (either the Pro Kit or the stock height Moog)
or
b) Put some Konis on the car and keep the Sportlines.

I noticed the same issue with driving down the highway when I tried cranking the setting to max (full firm) setting on my Konis. It made the car ridiculously darty over the slightest pebble or crack in the road (but only when highway driving). Dialing the **** back down towards the middle setting or less, eliminated the problem. Your AC Delco struts and shocks are expecting the car to be at a certain height. The Sportlines leave them in a continual compressed state. This takes away the ability of the strut/shock to do it's job over the highway bumps.

I would guess that about 95% of alignments that our cars get are the wrong setting or even worse than the way they went into the shop. The chart above is a great guide for alignments.

 

I'll try the alignment specs above first. But what you're saying Reid, makes total sense. I'm running the stock corvette C6 18x? front with a 255/40 and the back is a 19x11 with a 285/35. But these wheels are a lot lighter than my stock iroc 16's. So I wondered if the un-sprung weight, combined with the stiffer spring, lowered, and ac delco replacement struts weren't half of the cause. LOL! But if I put the stock rims and tires on it's easily driveable.

 

I haven't taken the car in for alignment (too many 12hr workdays lately). But I did get the chance one night to put my stock rims back on. The car drives almost like new. No darting, no pulling, even over rough pavement the car is planted well. I can drive with one hand on the steering wheel.
But I do have a new vibration from the rear. It almost feels like a bad u-joint. So I need to look into that also. If the car drives this much better with the stock rims... does anyone think it is still related to the alignment being wrong? I guess the wider tires would definitely multiply the effects of wrong alignment. But I seriously cannot believe the night and day difference on how it drives with the stock rims back on vs the C6 rims.

 

too much camber (you would probably be able to see this), not enough toe in (3/32, not zero or toe out), and not enough caster can all cause darting/wandering. Do you have a print out of your last alignment specs? If you can post a scan or a picture of it we could look at that and tell you how it is or if it needs improvement. Might save you from having to pay for another alignment.

 

As stated above wider tires are more than often the culprit of darting in 3rd gens.

The "wondering" with the larger tires could possibly be worse because of incorrect alignment but I think you'll find out a new alignment will not cure 100% of the darting.

The vibration you have could be a number of things...Pinion angle, wheel out of balance, U-Joint, rear end gear,.......ETC.

Craig