Welded suspension?

[kevinthenerd]

Does anyone have any experience with what a welded suspension on a street car feels like? I know it would be VERY twitchy, but is it drivable? Does it provide more grip than a stock suspension?

[GreyGoose006]

by welded do you mean that there is effectively no suspension and the axles are welded to the frame?

[kevinthenerd]

Originally Posted by GreyGoose006

by welded do you mean that there is effectively no suspension and the axles are welded to the frame?

What I had in mind was more like a front-wheel-drive vehicle with the front and rear shock absorbers either welded solid (with bracing for stiffness) or just replaced with solid bars.

[KiwiBacon]

Originally Posted by kevinthenerd

Does it provide more grip than a stock suspension?

No.

It'll bounce off the road with every minute bump.

[kevinthenerd]

Originally Posted by KiwiBacon

No.

It'll bounce off the road with every minute bump.

What if you're using high-profile tires? (What I have in mind are my crappy P185-70R14 tires.) There's quite a bit of give in the tires and bushings in a street car. Have you seen how high the damping and spring constants are on an F1 car?

[2.2 Straight six]

Originally Posted by kevinthenerd

What if you're using high-profile tires? (What I have in mind are my crappy P185-70R14 tires.) There's quite a bit of give in the tires and bushings in a street car. Have you seen how high the damping and spring constants are on an F1 car?

yes, but F1 tracks don't have bumps and potholes.

[534BC]

sounds like driving a tracor on the road.

[kevinthenerd]

Originally Posted by 534BC

sounds like driving a tracor on the road.

You mean tractor?

[kevinthenerd]

Originally Posted by 2.2 Straight six

yes, but F1 tracks don't have bumps and potholes.

potholes, no, but bumps, yes. If the tracks had absolutely no bumps then a stiff suspension would be best. I see where you're going, though. Streets are a lot bumpier than F1 tracks.

A lot of my friends have modified sports cars, and I can outcorner them in my FWD crap box on very bumpy surfaces. There's an intersection near my apartment with potholes and manhole covers stickup up quite high, and I can rip through that faster than any of them because my suspension is so pliable. (I've seen them try, and they tend to skip over it.)

[curtis73]

best handling will always be achieved with the PROPER spring rate, not just more. It all works together to transfer weight, keep the tires on the ground, and (in most cases) keep the body and frame from not falling apart.

Most street cars have oscillation frequencies of about 1-2 Hz. F1 cars have oscillation frequencies of about 4-6 Hz. Welding your suspension in effect gives you an oscillation frequency of approaching infinity. That's a pretty big difference.

Not to mention the weight transfer that is supposed to be progressive and compliant will now be completely responsible for absorbing all of the impact. The first pothole and your control arm, welded shock shaft, spindle, wheel, upper strut mount, pretty much everything runs the risk of being absolute toast.

[kevinthenerd]

Originally Posted by curtis73

best handling will always be achieved with the PROPER spring rate, not just more. It all works together to transfer weight, keep the tires on the ground, and (in most cases) keep the body and frame from not falling apart.

Most street cars have oscillation frequencies of about 1-2 Hz. F1 cars have oscillation frequencies of about 4-6 Hz. Welding your suspension in effect gives you an oscillation frequency of approaching infinity. That's a pretty big difference.

Not to mention the weight transfer that is supposed to be progressive and compliant will now be completely responsible for absorbing all of the impact. The first pothole and your control arm, welded shock shaft, spindle, wheel, upper strut mount, pretty much everything runs the risk of being absolute toast.

Thank you. You're right. I'm under the impression that cars in the 50s had suspension frequencies around 1 Hz but that today's cars are around 1.2 Hz. Sports cars are around 1.8 Hz. Race cars are anywhere between 2 and 10 Hz, with 10 from the glory days of ground effects in F1.

Correct me if I'm wrong, but I guess this also the reason why trucks have such loose damping. The suspensions tend to see a lot of abuse, and a stiffer setup would produce more forces in the components.

I would be happy with 2 or 3 Hz but welding a rod is a lot cheaper than buying aftermarket stuff. Those aftermarket components, however, would be a lot cheaper than bending and welding a unibody back together.

[GreyGoose006]

well the suspension isnt the only thing to consider

while it is true that f1 car suspensions run at very high frequencies, the tires run at much lower frequencies than you might expect

if you were to look at an original mini cooper, you would see that its suspension consists of rubber bushings between an axle and the frame. the tires played a big role in the suspension here too.

you might not want to weld the suspension together, but you can get away with very high frequencies on a track.

on the road, you should stick with springs though.

also, beware of 6.9-7.6 hz. that is the resonant frequency of human eyeballs.
i herd a story of an f1 car that had a suspension frequency in that range and the driver couldnt see when he got up to speed.

[KiwiBacon]

Originally Posted by kevinthenerd

What if you're using high-profile tires? (What I have in mind are my crappy P185-70R14 tires.) There's quite a bit of give in the tires and bushings in a street car. Have you seen how high the damping and spring constants are on an F1 car?

Much of the purpose of your suspension is to control the bump force. A tyre is very bad at controlling force, it just squashes and then returns it. No real damping (so you'll keep bouncing) and a spring rate that is really wrong.

You really need to compare spring rate at the wheels, while some cars have really high spring rates, they can run leverage of 2-3 or more from the wheel, so the wheel rates are much more sane.

F1 cars also have harder suspension to cope with the aerodynamic deivces. Those wings work best at a certain angle, so the firmer suspension keeps the car at that attitude more often. They also have very large changes in downforce (more than their dry weight).
Soft suspension would give large changes in ride-height as the downforce changed.

Rough rule of thumb, the more uneven the surface, the softer your suspension has to be. Consider the extremes of a baja buggy and an F1 car.

[KiwiBacon]

Originally Posted by kevinthenerd

Thank you. You're right. I'm under the impression that cars in the 50s had suspension frequencies around 1 Hz but that today's cars are around 1.2 Hz. Sports cars are around 1.8 Hz. Race cars are anywhere between 2 and 10 Hz, with 10 from the glory days of ground effects in F1.

Part of the reason for 1Hz in a road car is biological. It's a vertical frequency that doesn't upset people much, possibly because it's close to the frequency we walk at.

Slower frequencies (old caddilac, boat on a rough sea) make us feel sea-sick. Faster frequencies feel jiggly.

But that mainly concerns how a car reacts after a bump.