How to make a flaccid car more stiffy ?

[sugarwood]

Originally Posted by masraum

Ah, ok. I know that most miatas, especially the 1st gen, come with really soft springs. I hated the springs on my '97. THat car with just 128 or 133 or whatever hp had tons of squat on accel and dive on braking and wallowed through the corners (lots of grip, but also lots of roll). I was much happier when I put the springs and shocks on it.

Originally Posted by Tobra

The stock mazdaspeed suspension sucked ass, but for about a grand and a half it was the cat's ass

Originally Posted by island911

I drove a 98 MR2. I expected to like it. I didn't. It's no 911. Squishy... wet noodle. ... meh.

What determines how rigid a car rides?
It is mainly the springs?

If I wanted a Camry to have a rock hard race suspension,
could you do it just with just new springs and struts ?

When people bash a car for having a floaty ride,
can this be rectified with just new springs and struts?

[pwd72s]

Chassis stiffening also required in some cars...one trick early (2001) Bullitt Mustang owners have done is to add sub frame bracing from the convertibles.

[legion]

Actually, it's usually the frame of the vehicle. The more flex in the frame, the harder it is to tune the suspension because the frame is moving and the suspension is moving. The very short explanation is that having both moving can cause weird and unpredictable things to happen. The stiffer the frame, the easier it is to get the suspension to do exactly what you want when you want it to do it.

In general, the older a car is the more flexible the frame. In general, the less "sporting" a car is, the more flexible the frame. So a Camry probably isn't a great platform to start with if you want to tune the suspension.

[Tervuren]

Yup, frame movement is far more than most people realize.

In karting, there is no "spring", it is all chassis/wheel/tire flex, and you run chassis with different stiffness for different surfaces.

There is also bushing play when it comes to cars.

Then there is the suspension geometry.

Even if I stiffen the suspension in my 944, it won't feel "right" in a corner on sticky tires.

For me, bushing play comes before chassis flex, since the chassis flex tends to be more linear. Bushings can wedged and "bind" creating inconsistency.

Wheel stiffness also matters, same tire, similar weight wheel, different design, you can tell how the car responds.

Making a car feel right is the sum of a lot of different things, and different people may desire different results.

I find a car that is consistent over a variety of bumps and pavements to be what I like, and that means good bushings, stiff wheels, but not too stiff of suspension.

[KNS]

Aren’t all contemporary car these days pretty stiff? The frame, that is. I would think the frame on a 2017 Camry (or even a minivan) has got to be much stiffer then the same car made 20 years ago.

Was watching an episode of Roadkill the other day (great show!) and a modern, stock minivan went around a dirt course faster than a purpose built (albeit ancient) four wheel drive track car.

[Tervuren]

One other thing, your driving position really does change how you feel what is going on.

You will feel more lateral G if sitting towards the back axel, the back axel runs a tighter radius than the front.

[John Rogers]

I read the post several times and it appears that the tires and wheels were missed? When we did my 914-6 and also my daughter's 914-4 for racing we started at the ground and worked up. In my case the car had a lot done, it already had Goodyear slicks and aluminum wheels and the largest front torsion bars available, same with the rear springs. We replaced the shocks with adjustable Koni shocks front and rear as if a car hits a bump the shocks need to control how the car recovers from the "shock".

The front suspension and rear swing arm mounts were all reinforced with either steel plates and/or adjustable tubes. We also mounted a rear anti sway bar since we had installed a limited slip in both transmissions. The car rode like the proverbial lumber truck but it cornered flat as a pancake!

With the 914-4 we went with slightly larger front and rear suspension and Koni shocks that were called "aggressive street" models. Not sure if they are around now days. We put in a large front sway bar and added suspension reinforcements but not as aggressive as the race car. It only had 205 - 70 - 15 sized tires, so they flexed a lot more than the race car's Goodyear 9 - 23 - 15 cantilever slicks. I won a few races both here and in Baja MX and my daughter won her class at the 2000 Porsche Parade so what we did worked well.

[908/930]

Stiffness of anti roll bar would also fit in there somewhere, I test drove a BMW e60 with a sport pack years ago it had some sort of electronic activated anti roll bar, suspension felt cushy in a straight line but throw it into a corner and it went around flat as a pancake, quite a cool system.

[Captain Ahab Jr]

Originally Posted by Tervuren

One other thing, your driving position really does change how you feel what is going on.

You will feel more lateral G if sitting towards the back axel, the back axel runs a tighter radius than the front.

that is to do with moment of inertia, further you are from the cars pivot point the more you'll feel it

[Tobra]

The difference in my car was stiffer springs and revalved dampers. The actual structure was not changed, though the model I have has all the chassis bracing they added to the car over the course of its production.

Where the control arms attach, there are rubber bushings that wear out over time. I am replacing mine with rubber bushings that are significantly stiffer than the stock parts. I chose rubber over delrin or polyurethane, due to concerns about too much harshness in the ride.

As is discussed, there are a number of things in play.

[Tervuren]

Originally Posted by Captain Ahab Jr

that is to do with moment of inertia, further you are from the cars pivot point the more you'll feel it

No.

If your pivot point is the rear axle, and you sit over the rear axle, you will experience more lateral G than if you are over the front axel despite being further from the pivot point in the latter case than the former.

The pivot point of a bus is around the rear axle, get a ride in one at a constant corner and walk back and forth as it turns. You'll find the result is the exact opposite of what you claim.

The rear axle is running a tighter radius than the front axle and you will feel the difference.

[masraum]

Originally Posted by sugarwood

What determines how rigid a car rides?
It is mainly the springs?

If I wanted a Camry to have a rock hard race suspension,
could you do it just with just new springs and struts ?

When people bash a car for having a floaty ride,
can this be rectified with just new springs and struts?

The others are probably right about the overall stiffness, but the bouncy, floaty feel that you feel when driving a fairly modern car is probably mostly down to 3 things, springs, shocks or struts, and anti-roll bars.

Two different shock absorber's on the same springs and car can make the suspension feel very soft or very stiff.

But the stiffness of the springs will also have an impact on the ride quality/feel of the car.

Also, stiffer anti-roll bars will impact the "stiffness" and feel of the car.

[dafischer]

I believe it was Colin Chapman who said "Any suspension can be made to handle, as long as you can keep it from moving".

[Tervuren]

Originally Posted by sugarwood

What determines how rigid a car rides?
It is mainly the springs?

If I wanted a Camry to have a rock hard race suspension,
could you do it just with just new springs and struts ?

When people bash a car for having a floaty ride,
can this be rectified with just new springs and struts?

That might depend on the year of Camry.

The first step is to make sure you have a stiff enough wheel design.

The second step is to make sure you have a tire with the handling character you want.

Step Three get suspension bushings that won't deform causing wheels to point akimbo under shock stress or suspension load.

Get your stiffness between the suspension mounting points to a desired level, a modern Camry is going to be much better than an older one.

Once this is attained, you will start to get a car that handles in a consistent manner.

This is where you start to play with anti-roll bars, shocks, springs.

If you just put a stiff spring in, and the shock load causes the bushing to flex in a way that toes the car out as you hit bumps, the car will feel very unstable, the opposite of rigid, but in a different form of not being rigid than a car with a soft suspension.

No matter your suspension, is goes through the tires/wheels.

I have a thing for gathering data, so I tend to change to a different tire every time I buy.

On my Jaguar XK Coupe(Which has a stiff chassis):

It had a floating feel to it when I put Continental DW's on it. Very little steering wheel feedback, very mushy.In contrast, it would tramline twitching in reaction to the imperfection in the road with Hankook's Ventus V12 EVO 2's.

Same car, same suspension, same bushings, just different tire.

The best result is going to be from optimizing the sum of everything.

Porsche on their 80's cars tended to not go too hard on the spring rate, a decently aggressive damper compared to the mild spring rate, and mild to medium anti-roll bars.

A lot of body roll can be eliminated by suspension geometry design. Body roll's largest detriments are for fast transitions left/right, and aerodynamically for ground effects.

[dewolf]

Originally Posted by dafischer

I believe it was Colin Chapman who said "Any suspension can be made to handle, as long as you can keep it from moving".

I like that.

[RKDinOKC]

General
If the car feels like it is bottoming out, especially bumps at higher speeds, stiffer springs.
If the car rolls too much in corners, stiffer sway bars.
If the car is too bouncy, stiffer shocks.

For best handling, all of these need to be balanced for the front and rear weights of the car.
First you set the spring stiffness to get the best balance cornering without swaybars or shocks connected.
Then you adjust the swaybars to keep the car from rolling, but keep the front to rear balance, and too stiff and the car will corner slower.
Lastly adjust the shocks. Not just to smooth out the springs with dampening, but to control the rate the weight is taken off the ends of the car for maxium braking and acceleration.

[DanielDudley]

Originally Posted by sugarwood

What determines how rigid a car rides?
It is mainly the springs?

If I wanted a Camry to have a rock hard race suspension,
could you do it just with just new springs and struts ?

When people bash a car for having a floaty ride,
can this be rectified with just new springs and struts?

Floaty is shocks or struts. If the springs are stiffer, floaty turns into bouncy.

[DanielDudley]

What would I do if I had a Camry ?

Google search; https://www.google.com/search?q=Camry+Sports+suspension.&ie=utf-8&oe=utf-8&client=firefox-b-1-ab

[pwd72s]

Or..just buy a base Camry and use it for it's grocery hauling and chores running design purpose over 100,000 boring and relatively trouble free miles.

[island911]

In the world of mechanical engineers everything is a spring. and it's all relative.

If you have squishy tires, springs and/or 'shocks' (dampers) then the chassis will seem relatively rigid. (even if it's not, compared to other chassis stiffness)

Chassis stiffness is a big deal in keeping the rubber on the road, especially when increases to spring and/or damper rates are had. ...or increases to unsprung weight (larger wheels tires brakes...)