JIMMY54

iTrader: (2)

Here is my problem, my car drives perfect on flat roads.... but roads with slight grooves such as highways makes the car almost jerk into the next lane. I have to seriously hold the steering wheel in some sections of highway.

So I adjusted the steering gear, not to have play in the steering. Ball-joints and tie-rod ends are all new. Then I bought a full suspension. Tokico HP shocks, Eiback springs 300lbs in front, and 175lbs in rear, with ground control coil-overs. So EVERYTHING is NEW.

What is going on with my car, I take my other car on the same roads and it drives perfectly. Here is a picture of my car.

If it matters the wheels are 16x7 with new dunlop 205/45r16's FM901 w-rated tires.



http://www.portugesethug.homestead.c...BrakeSetup.JPG

www.portugesethug.homestead.com/files/jimmy1.jpg

Ralph

If your castor is adjustable, you may need to increase it. A large number of cars have about 5-6 degrees of castor as standard. It helps make the car track straight and resists forces that attempt to turn the wheels.

Also, if your toe is set outward (positive toe, I think), the car is more prone to wander. A slight amount of toe in is desireable on street cars.

Mld>7

Hey Jimmy.
Did your car always do that? When did this start? When you first got the car, after the suspension or rims and tires? because with 205/45r16 tires that's gonna happen no matter what you do. When your riding on very flat faced sticky rubber the car will always follow the dips in the road allot more. I used to have re92's and changed to SO3's and my car started driving like that also. It happens. Also if you installed the new suspension yourself did you set it up right? toe, chamber, castor?.. if not and you aren't really sure of what your are doing then get that done by someone. That will make a big difference. Oh and btw if the Hwy your talking about is the 401.. every cars steering will be fucked on the pos.

JIMMY54

iTrader: (2)

Ralph....

The only thing I guess my suspension is missing is the caster/camber plates.... Unfortunately I can't adjust that. But thanks for the info, I might try getting those plates and see if it would remedy my problem.

Mld>7 That was funny about the 401, true that and the gardiner/qew mostly. It really takes the fun out of driving the car. The car was all done properly, and I'm can't remember if using my original rim/tire combo if it would cause this. anyhow do you know a shop that could set up the plates when I'd put them in?

Thanks guys for the help!!

Cheers!

Jimmy,

i don't think its a castor problem. What are you alignment settings? I think having either a TOE in or TOE out will cause this.

Travis R

I bet it's relate to the wheels. What is the offset and rolling diameter of the new wheels/ tires compared to the original? If the offset is different, the there is more torque on the steering knuckle.
Think of it this way. Draw an imaginary line down the strut all the way to the ground. For the least amount of force transmitted by the road, you want that line to intersect the middle of the tire as it sits on the ground. If you have pushed the tires out by the choice of rim, then that line hits more towards the inside of the tires contact patch. So the road has an easier time twisting the wheel out of your hands.
Let's try some ascii pics
"+" is where the steering axis intersects the tire.
1.) Good
(inside of tire) |_____+_____| (outside of tire)

2.) Bad
(inside) |__+________| (outside)

Good luck

rx7gslse

Jiummy, you've got the same wheel setup as I do, and I've got the same problem...

if the lane has two "ruts" from where the tires are it'll hop from side to side.... I just drive on top of the ruts..

its' a wheel/trie thing....

JIMMY54

iTrader: (2)

I'll try swapping rims for a day, if that doesn't work I'll get my alignment checked.

Sucks driving with that crazy pulling everytime there is a bump.

JIMMY54

iTrader: (2)

if on my next set of tires I moved to a 50 series profile, would it help my cause?

bcty

if its the rims and tires get them balenced..

nickj

Your tires are seriously underloaded (not the same as underinflated). The car just has McPherson struts, after all -- it wasn't designed for rubber that wide, especially supported by 7" rims. Changing the caster would help, if only by loading up the edges of the tires. They'd flatten out in the turns, when the load's higher.

I also think the offset explanation has a lot of merit. The tires are overpowering the car.

Aico

Maybe you need roll-center adjusters?

Kill No Cone

iTrader: (6)

Jimmy,
Can you swap wheels and tires with a friend with a first gen? This would allow you to see if it is the wheels and tires or in the other suspension parts.

JIMMY54

iTrader: (2)

The car is in storage because of winter, but I will put my fatory 195/60/14 front tires back on and try it out to see if anything changes.

GtoRx7

iTrader: (5)

I have the same "problem" on my car, which has 8" wide front tires, and a 2" offset. Stock rim is about 4" offset on a Gsl-se. I have had the whole car alined a couple of times, on a lazer rack, but it still pulls very hard into any rut or uneven pavement. And my tires are r-compound, so I just accept it as a price to pay for HIGH grip on the street. I even changed to power steering to get a faster ratio, and maybe help, but it got worse, cause I had even less torque to keep the wheels straight. If anyone finds out a cure, I'd like to know too!!

Travis R

Sure there's a cure, but you my not like it. You can either put the stock wheels back on, or find a wheel that has the correct backspacing. If you want to run WIDE wheels, then you will probably have clearance issues once you push them that far under the fender.
You could also move the top of the strut in so that the intersection point I was talking about earlier moves back towards the center of the tire. There are a couple of upsides to this. One is increased camber... hopefully not too much. If so you will need to modify the spindle/upright to straighten the wheel up. The other upside is that it should give you more space between the rim and the strut, so you could run those wide wheels.
Good luck

DamonB

Wide tires and different offset are contributing to the problem. When the center of the contact patch is far oustide the intersection of the kingpin axis with the ground the steering wheel will kick back more due to the increased leverage the tire/wheel now has over the spindle.

GtoRx7

iTrader: (5)

I thoguht about this before, with the axis being drawn though the center. It defintily makes sense, so if I was to put on wider wheels, say 15x10, my offset would be stock (4" backspacing and 6" front spacing) i would have a wider tire with not any more torque steer, right? Remember I do not have a stock 1st gen, it has a GTO widebody fiberglass front fenders, and can accomodate 15x10 easily with no clearance issues. In fact I believe 15x10 is what is suppose to be ran on it. I just couldnt find a low profile tire for 15x10, so had to go with the 15x8, with most of the tire being front spaced (2" back spacing, 6" front spacing) Also, my car seems to handle incredible with my current setup, it blows away the third gen I had by ALOT. Pulls roughly 1.2 G's currently on the G-tech, I cant imagine any more!! IF I was to change to 15x10 front and 15x12 rear, the handling would be even greater right? Is there any downside to a larger one besides the extra unsprung weight.......

DamonB

You can easily put too much tire on a car. Wider tires at high speeds will cause more drag. They will also shed heat quicker and be harder to heat up in the first place.

Travis R

I was refering to clearance on the inside. I'm sure you can run REALLY wide wheels if you stick them out further.... but that's what got the handling squirely in the first place.
It's easier for me to think about this problem in terms of offset instead of backspacing. since it references the centerline of the wheel. You want a wheel with the same backspacing as the stock wheel.
When converting these things into race cars you can make a lot of sacrifices in the name of handling. But if you have to drive the car on the street, then you will probably want to make a different set of sacrifices.
Good luck

JIMMY54

iTrader: (2)

Good point!!

LongDuck

Hey, just wanted to chime in with my own experiences which mirror *exactly* what is described by the car 'hunting' on anything other than completely smooth and flat roads.

I installed Tokico blues in the front, had Koni 1-1/8" stabilizer, full poly bushings, and RB strut bar. Ran great with stock wheels (14x5.5) and 195/60-HR14 tires. Bought new wheels in 15x7 shod with Yoko AVS ES100's, 205/55-ZR15 and suddenly the car feels like the lug nuts are coming loose on any road with ruts.

First time I had the wheels on, I pulled over and rechecked the lugnuts to be sure that I wasn't about to lose a wheel - all torqued to an even 100 ft/lbs each. Definitely not the problem. Thought it was possibly bad wheel bearings - tested and 100% both sides.

Thought it might have been a toe-out problem caused by changing wheel width - added more toe-in - no change. Tires are still wearing on the inside edges as if pulling outward from excessive toe-out condition.

Car still wanders from side to side, but less so now that I dialed in a bit more toe-in.

One of these days, I'll re-install my old wheels and tires (stock SE rims) and see if that fixes the problem. From what you guys are stating, this appears to be a common problem for wider wheels, flatter tires.

You are not alone.

Travis R

I ment to say offset not backspacing, but you got the idea.

JIMMY54

iTrader: (2)

40mm offset on my rims? anybody know what the factory are?