CA-Legal-Vette

I should have been working last weekend. TONS to do. Instead, the weather was perfect and on Saturday afternoon, I took a ride down to one of the local reservoirs with the family. It was beautiful and everyone enjoyed it. On the way back, my wife remarked that it would be a perfect road for me to take the Corvette down. By myself !(She gets car sick ). What a great idea

So Sunday morning, I put in half a tank and off I go. Again, perfect weather for top down driving. Tunes playing VERY loud. I may even have been going ever so slightly over the limit. 40 MPH limit down most of the road. In general, the car performed extremely well. I did a lot of suspension work before leaving CA a few years back and it really handles the curves and bumps well EXCEPT when going over rises. Because I had been down the same road the day before in my DD, I really felt like the car's ability to stay glued to the road had room for improvement. My DD has pretty decent suspension (GS430) but a Vette should be able to do better no? Besides bringing changes of underwear, what can I do to keep the car from floating over rises?

Oh and the obligatory pic:

Shark Racer

I'd bet the tires on your GS430 are probably a bit better than the ones on your C3.

There are a few things that make big improvements on modern cars:
1. Chassis/body rigidity - I think pretty much every car built in the last 10 years is better in this regard(maybe not the really junk cars).
2. Newness of components
3. Tire sidewall strength, compounds
4. Seat support...

Driving my car on a public road with bumps it's not very settled. Take it to a smoother track and it does pretty damn good.

jnb5101

The un-sprung weight on the newer cars is a lot less than the vette (brake discs, calipers, half shafts, etc). That in itself would keep the tires in contact with the road.

Jebbysan

Increase the rebound dampening....

Jebby

CA-Legal-Vette

Please elaborate. Increased spring strength?

Stock rallys and iron calipers so yes, it would be hard for me to have more unsprung weight without filling my tires with glycol.

All good points but not easy to address save tires. You think my stock 70s won't perform as well as 235 45 17's?

MajD

Jebby is talking about adjustable shocks. When you go over a rise, inertia keeps your rear end rising. At the same time, the rear spring wants to return to it's unsprung arc, so it also pushes against the rear end at the same time. This motion extends the shock absorber, sometimes to the stop. Increasing the rebound makes the shock harder to extend and saps energy from the rear and spring inertia so it doesn't rise as far as fast.

This is usually an issue for folks that have replaced their stock springs. If yours is stock, maybe your shocks are worn out or a stiffer, non-adjustable set may work. Adjustable shocks can be a bit pricey. Hope this helps.

MajD

Shark Racer

I just helped my friend try out wheel fitment on his 71 'vette. The stock rally wheel(plus trim rings and center cap) with 255/60-15s was heavier than the 285-40-18 on an 18x9.5 we were trying out.

I'll answer assuming you're not being sarcastic
I would need to know what tires you have on each of your cars to be certain, but I would say most tires in 235/45-17 except the very cheapest will perform better than the common tires on a 225/70-15. Just looking at the offerings on Tire Rack, best-to-best is leagues of difference in tire performance. Worst to worst (OK, let's ignore the snow tires for the 15) is more similar.

CA-Legal-Vette

Yes, being sarcastic but thanks for answering anyways. My DD tires are Michelin pilots. Not great in the snow but more than acceptable under any other conditions.. My Vette tires are Kirklands but before you start making too much fun of them, they actually perform better than the 60 series BFGs that I had on my previous Vette. The reason for my remark is that the DD footprint is at least double that of the Vette tires.

CA-Legal-Vette

Got it. My rear springs are aftermarket (VB&P) with Bilstein Sports all around. None are adjustable.

CraigH

Not trying to be rude but why do you think a 40 year old Vette should out handle your modern DD on the road.

I love my. 71 and for a US car built back then it's a great handler but the auto industry has moved a long way in suspension, tires, body rigidity etc since then.

You certainly should be able to get it to handle well but if your trying to get it handle closer to modern cars you will need some significant changes beyond tires.

7T1vette

When going over a 'rise' at speed, the car will lighten (waiting for gravity to draw the car back down to the road) and the springs will extend. Having stiffer springs won't change that effect, but it will reduce the distance the springs extend when going over that rise, so there is less distance between the [airborne] tires and the road.

To maintain contact with the road, the car would need more downforce...perhaps provided by aerodynamic features (wings).

MajD

You should consider adjustable shocks if the rebound really bothers you. I can't think of another practical way to increase the force that opposes the rear end lift. Anything you attach to the car, such as a spoiler or spare tire carrier, to try an increase the drag or weight, adds its mass to the inertia going over the rise and makes the problem worse. The shocks work because the energy required to extend them comes from the generated inertia.

MajD

DUB

Stupid question..and it is only because I can not see it in the photo you posted.

But do you have the black plastic air dam/front spoiler that the factory installed on the underside of your valance panel???

I know it not much...but it better than nothing at all and allowing all the air to flow under the car instead of directing some of it in the radiator area.

DUB

CA-Legal-Vette

Stock 73 setup. Everything is in place but even though I may, possibly have exceeded the speed limit briefly, I don't think it's anywhere near fast enough for the aerodynamics to be a factor. Any inkling of how fast it would become a factor?

I don't for a moment expect it to be equivalent, I'm just looking for better. It was a little startling to me how much worse it was in this particular aspect.

Shark Racer

I've only ever driven my 78 hard, which is a Pace Car with all the spoilers intact, but I'd imagine downforce isn't really an active component until 70-80mph. I don't think I've ever pulled through a turn hard enough at those speeds that my sense of self-preservation started to creep in.

I've found that in my car, the biggest improvement to perceived performance was tightening up the steering (Borg Box). I could definitely use more supportive seats to more comfortably use the car hard. I'm into the door / center console on city streets when I'm motivated and not really pushing the car hard.

DUB

This thread may offer some answers.

https://www.corvetteforum.com/forums...o-airborn.html

DUB

SwampeastMike

By "going over a rise" do you mean what I call "stomach jumping"?

Does your GS430 have active suspension?

If "yes" to both I believe you have zero reason for concern.

There's a wild rural "stomach jumping" highway in my area that I drove many time in my youth (on the way to the lake) and a few times since. I once drove my STS (with active suspension) on that road and no matter the speed it utterly refused to give the feeling.

Shark Racer

We had a sharp crest on one of our local roads that I discovered the hard way, nearly put my 78 into the cliffside. I was careful from there on out, except on the way back one time in a different car - forgot about it and discovered what jumping a car feels like.

CA-Legal-Vette

Definately stomach Jumping as you describe it. My GS does not have active suspension.

CraigH

That makes more sense and your description of the stomach drop.

I know I have tried many different front suspension changes to get it how I want it. Never felt really comfortable. Lowered with 18" wider tires induces more wander, bump steer etc so latest and what I am happiest with is Borgeson box, Global West upper arms, Global West extended travel lower arms, QA1 + Speed Direct semi coil overs, Steriod rod ends to level the Tie Rods, spreader Bar.

2 biggest Items are Borgeson and GW upper arms. The upper arms added heaps more caster giving higher speed stability And the Borgeson tightened up the entire steering experience.

Have done some work on the rear but that will be next big make over. So interesting to hear what you experienced with a big drop after a rise in road.

The suspension obviously needs to handle the drop then settle effectively without getting any bad deviation from the direction you had set.

Unless your going way fast I can't imagine the air dams etc will have much play in it.

The floating you get, do you feel it's caused by the front or rear suspension in that situation.

Even simple things like a bump stop missing on one side would cause one side to compress more and would make the car move off straight.