Steering & stability at high speeds: Who's gone fast?

Every car has that speed where it starts to float and feel like she going to become airborne. The older the car, the lower the speed this seems to happen at. What have people come up with over the years to increase the high speed stability of their old iron? I'm talking high speed sustained driving, like a lake bed, not 1/4 mile drags.

 

The fastest I've ever been in my T Bucket was 120MPH on a local freeway at night. That's when it felt like it was floating. My response was to slow down.

There's really not much I could do to my car to make it more stabile. I guess I could add weight somewhere, but it's a street car, so I just take note of my limits. I should add that I've never done it again. Fear? Yes, I guess so.

 

In my old Porsche race car I was up around 150 and stable on the straight at Willow when a GT1 911 blew by me like I was standing still. The vortex off his car made me lose downforce and it felt like ice for a sec. Scared the shit out of me.

 

Air dams and wings to create downforce. Not very traditional for the street.

 

Does anyone have examples of an effective air dam on a classic not looking like shit?

 

I went pretty fast in a Pantera one night on I-85,young & dumb,and yes,alcohol was involved but that was many years ago,,,no proof only my word.

I also went pretty fast trying to keep up with Deuce Roadster,,no alcohol involved and old & crazy,,,notice the color of the knuckles HRP

Both cars seemed incredible stable.

 

You would get some very intelligent answers I bet, if you were MORE SPECIFIC- like what kind of car?

The air can hurt you and help you as well.

Down force can help you, air foils, air dams, spoilers/wings etc.

Uplift can hurt or kill you, lifting the car and tires from the surface. Splash pans or a complete underside panneling could help prevent that or limit it.

There is a HUGE difference surrounding this discussion if you are referring to a High Boy or something like your avatar, you must be more specific.

 

I'm specifically interested in full fendered pre-war style cars, mid-30's to late 40's... 1948 chevy is my specific project

 

Well, I'm sure a true engineer will come eventually and explain why these answers are all wrong, but based on what I've read I think you can:
1. Add an air splitter at the bottom of the front bumper, and/or an air dam extending down from it
2. add a partial belly pan under the front of the car and another at the rear to help smooth the air flow turbulence caused by our bumpers
3. Splitters on the roof? (Not sure if there'd be much gain from this. Do you have a '48 Chevy coupe or sedan?)
4. Sit the car as low as it can go, especially in the front. A forward rake provides a bit of downforce and a lower center of gravity gives you better stability.
5. Chop the top (lower center of gravity, smaller hole to punch through the air, and smaller area for side wind to hit.)

If you look at photos of cars from Bonneville you'll see air dams on the front of almost everything in a class where it is allowed, and splitters on the roof. A lot also have some sort of wing or dam on the rear but I don't see how that would work on a '48 Chevy.

I haven't even mentioned big-ass wings and such because I assume you don't want to go too super ugly?

 

DW takes his Model A well over 100. I believe he chased down a Lambo or something a few months back. Anyway, he doesn't have any of this stuff. Maybe he'll chime in...

 

i went a 173 MPH in a 1964 Chevy and it felt fine at that speed

 

173 in a BRICK ????????

 

forgot to say.....a 1964 Chevy Corvette GT-1 car..... the SCCA may have been calling it B Production at that time? at the end of the straightaway at Brainard International Raceway

 

the older I get, the faster I was. I went 300 MPH in my GTO. I am now king of the top speed bullshitters.

 

I am not sure what fast is, I have driven well above sanity more than once.

Airdams help as well as getting the nose down or belly pans or lowering the entire car. I have tried all of the above at one time or another.

 

What about suspension - I assume stiffer is better up to a point... and difference front vs rear?

 

We've got over 600 extra lbs. in our Bonneville car.

 

115 mph during Americruise '97 in a '55 Chevy 2-door hardtop, lowered, with radials and a front sway bar.

The engine could've gone a little faster, but the rest of the car felt like it was starting to "float".

My wife was asleep in the passenger seat.

 

Stiffer shocks, larger sway bar, (or add one) , wider tires, poly front suspension bushings, postive caster, negative camber, defect the air going up against (and over) the radaitor support through the grill, fill the gap between the bumper and body to act as an air dam, flare out the front of the fenders so the air does not go in the wheel wells, plus above ideas......

 

Silver state classic challenge truck. A lot of older cars runnning out there, I ran in my OT car clocked at 169.9 by Nevada Highway Patrol. Not mine but its cool and fast.

 

How much caster do altered/funnycars typically have?

How much caster do rear engined dragsters typically have?

How much caster do front engined dragsters typically have?

 

I have been 170.781 mph in a Model A roadster. 3300lbs. 14 degrees caster

Billy the Kid ain't been that fast!! Yet........

 

Oh yeah! I was thinking in terms of aero mods, but big ass front AND rear sway bars make a huge, huge difference even when everything else is the same. And use urethane bushings on the front bar.

I had a '73 Cutlass a few years ago that felt like it was floating at 75-80 on the highway. I installed a 1.25" front sway bar from a '70s Trans Am with urethane bushings and a .75" rear sway bar from a '77 Monte Carlo and it was a whole different car with no other modifications at all. I later changed springs, wheels and tires and that all helped as well but the sway bars really did the trick.

So: if your car sits low, has the center of gravity as low as possible (aluminum heads and intake, batter mounted low, etc.), has big-ass front and rear sway bars, has a front air damn, stiff springs, firm shocks, and low-profile tires you should be okay unless you're planning to go 200.

We all forgot to mention limiting how much air flows into the engine compartment and/or letting it out with louvers.

And after all that, make damn sure you have a really good strong hood latch with a backup! (Several of us have learned that lesson the hard way.)

 

I must be getting old, 75 MPH seems too fast for me anymore.

 

I made the needle peg, (More like bounce, bad cable), on the 53' with the old engine.
It was going downhill & it did take a bit of time.
Big bias plys, huge taker car.
Felt Fine.

 

1931 Desoto 3 window coupe. Leafs on all 4 corners. bias ply all 4 corners. 5" drop tube axle. 1953 chevrolet spindals. Mustange steering. 160 mph + very stable.

 

Its all about air getting up under the front of the car. At 130, they want to take off on you. Look up the biggest wreck at Daytona, think it was 1959 or 1960 when they filled out the sportsman field with modified coupes.

Bob

 

My buddy has a '35 Chevy P/U on an S10 frame. The front fenders catch air at 75 and the front end gets light. I, however, had a fenderless '32 Ford 3 window. I've had it up to 120, using up the fuel in my end carbs. I didn't realize I was going that fast. The car was pretty stable.

 

when people start talking about 150+ i always wonder....

i had an OT 80 Chevy Malibu 2 door, healthy small block, prolly 350 HP maybe, stock 2:41 rear gears. It would run out of Horsepower around 4200RPM in top gear. We mathed it out, its something like 141 MPH witht he tire size.

The car was lowered and thats about it. Drove fine. Now my Model T seems to handle better the faster you drive it. but i have like 10 Degrees caster in it. that thing witht he 3:00 gears in it will go faster than any sane man would want to drive it. I suspect ive had it up around 120, and it would still keep going. but with those gears and a 7:50 16 rear tire that thing had REALLLLLLY long legs.

 

Right? The fastest I have ever been was in an OT car and it scared the shit out of me...


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