GT suspension

[redbaron]

Hi,

Having owned and driven an Opel GT for a number of years I have always been disappointed by the suspension. The handling is good, but there are several compromises that eventually led me to sell my GT and move on. I was wondering if anyone else has noticed these failing and/or has come up with solutions.

1) Front suspension was quickly adapted from Kaddett. In order to lower the suspension they used a "shorter/stiffer" front leaf spring. The spring is so short that it has to be overly stiff to avoid frequent bottoming. The result is far greater stiffness in the front suspension than the rear suspension. If you sit on the luggage deck and take a ride you will find that the action of the rear suspension is quite supple and almost all of the ride harshness is contributed by the front suspension.

I think this could be solved using a Kaddett front spring in conjunction with drop spindles. This would be quite a custom fabrication project but I think it would improve the ride and even allow better handling on roads the require large amounts of "jounce" travel.

2) The rear axle torque tube is very short. In the Kaddett (and similar Chevette) this allows for more rear seat legroom. This short torque tube causes the rear end to rise up like a stinkbug under hard acceleration in the lower gears. The result is wheelspin, especially exiting tight corners. It would seem that a longer torque tube would help, but there might be easier solutions.

In may ways these are minor complaint but they are very noticeable given the complete competence of the car in other areas of steering/braking/acceleration/mileage/top-speed/etc. I suppose one can always avoid slow corners, or simply take them fast , but the rough roads are rather epidemic.

Cheers,
Scott (redbaron)

[davegt27]

What about Composite leaf spring.

According to this book I have in my hand it says that a Composite leaf springs perform at least as well as steel coils or torsion bars.


Instead of drop spindles you can use a longer stud lower ball joint and bump steer tie rods


I been thinking for a long time about cutting the front leaf in half and running two independent leaf springs in the front.

there is also enough room in a GT to some type of pull rod or push rod setup

on the rear you need some type of bird cage setup to allow you to raise and lower the front of the TQ tube

I agree a longer torque tube would help.

Davegt27

[redbaron]

I think composite springs are great, if pricey.

splitting the front spring might be worth a try. I always have wondered if the spring acts as a pro-roll bar. It seems that the compression of the spring on one side due to cornering loads could increase the tension on the other side and lead to more body roll. It would be a fairly large project to construct spring mounts that could withstand the strain of the split spring leaves. In the stock setup this strain is passed to the other half of leaves from the other side.

If you can lower the car by using the long stud balljoint with the stock spring and recover some or all of that height with a taller spring it would have the same effect as dropped spindles. It would seem that you would have to fit a spacer to the bottom of the upright to raise it relative to the lower control arm and this could be as dangerous as having a worn out upright on the ball joint stud. In other words, the ball stud would break from the strain. If you want to try this I would fabricate spacers and get a VERY GOOD welder to weld them onto the bottom of a stock upright using a stud to align them. After this you will have to get someone to machine a proper tapered hole for the stud. Note that this is basically manufacturing your own dropped spindle and if it broke, you would have nobody to sue. If you try this I would not recommend telling your life insurance agent about the mod. Maybe I misunderstood what you were suggesting.

Switching to push or pullrods could be interesting but unless you address the basic suspension height question you will not net any improvement to my original objection. Might answer some other needs with this mod.

As for raising and lowering the torque tube, I cannot see how this will change the "power on lift" in the rear suspension. If this lift were moved further forward it would tend to lift the entire car rather than the rear end only and would not fight the natural weight transfer of the car that tends to increase rear wheel traction.

My honest opinion is that the Monza/Camaro get it right by extending the torque tube to the transmission.

[davegt27]

Splitting the front spring might be worth a try. I always have wondered if the spring acts as a pro-roll bar. It seems that the compression of the spring on one side due to cornering loads could increase the tension on the other side and lead to more body roll. It would be a fairly large project to construct spring mounts that could withstand the strain of the split spring leaves. In the stock setup this strain is passed to the other half of leaves from the other side.

I was thinking the same thing about the front leaf but I don't think it would be to hard to do.

one way is to lock the spring in the center another is to but a pivot in the center i should have tried one of the two ideas instead of my botched coilover effort

If you can lower the car by using the long stud balljoint with the stock spring and recover some or all of that height with a taller spring it would have the same effect as dropped spindles. It would seem that you would have to fit a spacer to the bottom of the upright to raise it relative to the lower control arm and this could be as dangerous as having a worn out upright on the ball joint stud.

My race GT has long lower ball joints of course the stock spring gets tossed works great.

they been doing the ball joint thing for years. nowadays they use roll center adj. on strut type cars

the real problem is the rear of the car
you have to modify the rear so you can have good results of you front mods

i was digging around over the weekend and found an old video of my race GT on a solo II course and i was shocked with how much body roll (about 3 deg)

and even with 20" tall tires the front was way low but it was out of whack with the rear

in other words low front roll center and high rear roll center make for a not to well handling car.

davegt27

[opeldean]

since the kadette and chevette are similiar..has anyone put a chevette rear end in a gt?

chevette had a smaller engine...is it too weak? Would it be easier to install than an impulse?

[davegt27]

Since the kadette and chevette are similiar..has anyone put a chevette rear end in a GT?

yes Marty Reimer has one

also Pappy had a Circle track GT that had Chevette rear end

davegt27