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Discussion Starter #1
Hi,

What I don't understand is why the 164 3.0 12v front springs were not uprated to cope with the extra weight of the 3.0 24v engine. Maybe over the general weight of the car the extra 2 cams are not huge but is that right in terms of handling? The 164 24v's I've driven have been brilliant but do roll. Even a 24v Cloverleaf on hard suspension setting rolls quite a lot.

Has anyone found a better alternative to harder springs to reduce the roll? Appreciate this was sold as a high-spec exec saloon but it is so much more.

R
 

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When I added Koni shocks (cranked up 2/3 to more or less match the 91S "sport" setting in driving on the same roads) to the 94LS, I also put on S springs all around, plus adding larger dia aftermarket stabilizer bars front and rear to reduce roll. Couldn't be happier as to how it turned out. Very solid feeling on all roads, seemingly more so than the S actually, both with 16 inch wheels.
 

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I don't think the various V6 versions are very different in weight.

The 12V weighs about 375 lbs. The 24V has two more cams but two less rocker shafts and arms. That's the only difference. Must be pounds rather than tens of pounds. An automatic would add more weight than changing the engine spec.

Plus the biggest variable is payload weight from a minimum of say 120 lbs to a maximum of around 1,000 lbs fully loaded with fuel, people and luggage.

The limit facing suspension engineers designing sedans is the rear springs not the front springs. If the rear springs can handle weight differences of an order of magnitude the front springs should be able to handle a slightly different drivetrain weight.

Also, people think body roll is significant factor in handling but that is not the case. Body roll doesn't affect handling very much. On the narrow profile tires the 164 was designed for the amount of body roll is not relevant. You wouldn't want a stiffer front roll rate or understeer would be awful and inside drive wheel spin up would limit cornering speed. Increasing shock rates only affects transient roll, not roll limits. Increasing bar rates is a tricky process. Higher bar rates reduce drive wheel grip and increase single wheel bump rates. Ya gotta be pretty unhappy with the handling to make those sacrifices IMHO.
 

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"Increasing bar rates is a tricky process"

For one thing, changes in front and rear bars have to be balanced so that oversteer/understeer characteristics are not adversely affected. Many ignore that.

If one is not into excessive lifting and spinning the inside tire of a turning front wheel drive car, the reduced roll results in a shorter transition time to when the car is settled in roll. I have liked that, as exhibited when I changed the stab bars on the LS and S.
 

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Discussion Starter #5
Interesting point about the minimal weight difference from 12v to 24v, thanks.

Agree that roll may not make a massive difference to steady state cornering but it can make a huge difference to left-right-left cornering stability as it reduces weight transfer. Del, your modified set up sounds great. :)
 

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Carlo keeps saying, Jeez, I wish my 164 felt like this, but he doesn't have the time to make changes on his own cars, lol.
 

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Interesting point about the minimal weight difference from 12v to 24v, thanks.

Agree that roll may not make a massive difference to steady state cornering but it can make a huge difference to left-right-left cornering stability as it reduces weight transfer. Del, your modified set up sounds great. :)
One of the many misconceptions about roll stiffness is the presumed but non existent effect on weight transfer. Neither springs nor dampers affect weight transfer.

Weight transfer is the moment generated by the difference between the CG vector and the tire contact patch vector.

Roll is the leverage effect of that moment upon the springs as transmitted by the suspension arms.

If you can imagine a vehicle with its roll axis passing through the CG you will immediately see that weight transfer is unaffected by roll. The body cannot roll if all the tire contact forces pass through the roll axis at the CG height. The weight transfer will be the same as for a car that rolls onto its bump stops. Also, think of anti squat and anti dive suspension alignments which change the pitch longitudinally but do not change the tire grip. Anti roll can be effected by suspension geometry in the same fashion with identical weight transfer effects laterally.

The change in contact patch grip is unaffected by roll unless suspension geometry adversely affects the shape of the contact patch which in turn depends on the shape of the tire. The 164 is designed for a 195/65 or 205/55 tire. There is no way reducing roll can have any useful effect on total grip for such tires.

If you increase tire grip you increase cornering force and increase weight transfer accordingly. Otherwise, changing body roll has no effect on total grip through any weight transfer effects. The driver feels better, unless the driver knows better. That's all.
 

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"There is no way reducing roll can have any useful effect on total grip for such tires."

Yeah, we know that. I'm not sure anyone stated that it would. The desired effect is just a shorter transition time for achieving the resultant reduced roll. That changes the feel of driving the car. I've driven many older Alfas where one almost worried about scraping the chrome off the door handles, so to speak, lol, and I've come to desire less roll in the cars I drive. That's all.
 

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The point I was correcting was the suggestion that stiffer roll resistance changes weight transfer. It doesn't.

Of course increasing the spring rate whether directly or by use of roll bars stiffens the ride and inceases the speed with which weight transfer is transmitted to the body. The only effect is feel unless contact patch geometry is also affected. Some believe that grip is delivered more quickly too but that is pure illusion. Why? Because weight transfer and consequent roll result from grip not the other way around.

Tires grip and you get roll. Tires slide and roll stabilizes. Therefore, at the limits of tire grip spring rate makes no difference to cornering grip unless contact patch shape is improved.

Lowering springs deliver the same illusion of better handling. They don't. It's all in the driver's head. Lowering the CG by one inch (a fairly big drop for any road car) has indiscernible effects on tire grip and handling.

Changing roll bar rates to change the ratio of front to rear roll resistance is effective if, as is often the case with road cars, understeer is a little excessive. Conversely, if you add more power you should generally reduce roll stiffness at the drive axle end of the car, or increase roll stiffness at the non drive axle end. This allows more power to reach the road and more of the cornering force to be generated at the non driven axle.
 

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Discussion Starter #10
Hi,
If a car is rolling at 25 degrees in a corner there is going to be more effective weight on the outer tyres than the same car rolling at 15 degrees. Whether you want that labelled as weight transfer or otherwise, it does make a difference to the handling, stability and agility of the vehicle, which was the point I was trying to make. :)
 

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Hi,
If a car is rolling at 25 degrees in a corner there is going to be more effective weight on the outer tyres than the same car rolling at 15 degrees. Whether you want that labelled as weight transfer or otherwise, it does make a difference to the handling, stability and agility of the vehicle, which was the point I was trying to make. :)
Nope. That's what intuitively seems correct but it isn't.

Roll angle is proportional to spring rate and suspension geometry. Weight transfer is solely a result of tire forces acting on the height of the CG. Two cars experiencing different roll angles can have the same weight transfer.

The same car on the same tires will have the same weight transfer regardless of spring rate.
 

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I think he is implying that the CG of the car changes in location, which it does (a little) since, as you say, the location of the cg determines the tire loading.
 

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I think he is implying that the CG of the car changes in location, which it does (a little) since, as you say, the location of the cg determines the tire loading.
I don't think that can be it. Body roll lowers the CG by a very small amount which would reduce weight transfer a very little.

A small portion of the moment caused by tire grip does compress the springs by a modest net amount. The roll axis also changes also usually by a small amount.

Such changes generally increase total grip a little, by dividing the load more equally between left and right tires, the opposite effect than that one might intuitively conclude. Less body roll, whether from higher spring rates or suspension geometry changes, changes the rate at which the outer tire gains grip and the inner tire loses grip from loading changes but the maximum grip does not change, apart from very minor effects of changes in CG height and roll axis.

Stiffening the roll rate will improve turn in which is felt by the driver as better handling, particularly during transitions from left to right and vice versa, but will have very little if any effect on lap times. Whenever I see road cars compared for lap times I want to know what tires were on each car compared. Tires can make more difference than power to weight.

Lowering springs improve handling by reducing weight transfer allowing more equal distribution of tire loading. Since tire grip is proportional to vertical load, but not linearly, there is a sweet spot for weight transfer resulting from CG height. However, most lowering springs for road cars do not lower the CG by enough to make a measurable improvement and the negatives frequently outweigh the positives, in altered camber, anti dive and anti squat particularly.
 

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Discussion Starter #14
I don't think that can be it. Body roll lowers the CG by a very small amount which would reduce weight transfer a very little.

A small portion of the moment caused by tire grip does compress the springs by a modest net amount. The roll axis also changes also usually by a small amount.

Such changes generally increase total grip a little, by dividing the load more equally between left and right tires, the opposite effect than that one might intuitively conclude. Less body roll, whether from higher spring rates or suspension geometry changes, changes the rate at which the outer tire gains grip and the inner tire loses grip from loading changes but the maximum grip does not change, apart from very minor effects of changes in CG height and roll axis.

Stiffening the roll rate will improve turn in which is felt by the driver as better handling, particularly during transitions from left to right and vice versa, but will have very little if any effect on lap times. Whenever I see road cars compared for lap times I want to know what tires were on each car compared. Tires can make more difference than power to weight.

Lowering springs improve handling by reducing weight transfer allowing more equal distribution of tire loading. Since tire grip is proportional to vertical load, but not linearly, there is a sweet spot for weight transfer resulting from CG height. However, most lowering springs for road cars do not lower the CG by enough to make a measurable improvement and the negatives frequently outweigh the positives, in altered camber, anti dive and anti squat particularly.
Sorry, Michael but I think we are going to have to agree to disagree on this subject. After all, if roll makes so little to difference to grip, handling etc then why don't racing cars have soft suspension and simply roll about like a Citroen 2CV? Last time I watched Formula 1 they all cornered pretty flat.
I once modified the suspension of a Bertone X1/9, to reduce roll and let my mum drive it down windy roads, while I followed in a standard X1/9. She felt she was going gently but I was having to work really hard to keep up.
Agree that tyres can make a huge difference to grip, not least because ultimate grip is also a factor of how tyres bite into the road and how long the rubber can hold it together before it starts to tear apart, drawing black across the road or shedding 'marbles' (F1 again).
Being oldish and a very hard driver, not to mention having a degree in engineering, I am going to continue to aim for minimal roll and minimal effective weight transfer - experience has shown me the benefit in practice and, as far as I'm concerned, it is more viable to keep a car on the black stuff when there is not a lot of roll with dampers not having to work extra hard to damp large suspension/body travel.
All the best :)
 

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I describe only the physics of "weight transfer" which is a misnomer but descriptive. There is nothing to agree or disagree with. Draw a diagram and add some numbers and the arithmetic will illustrate my statements.

Body roll results from the moment created by lateral forces generated at the tire contact patches, reacted to by the suspension arms and the springs/roll bars. That moment results from the lever arm created by the height of the CG above the ground. That lever arm operates on the suspension arms which compress the springs at a rate determined by the height of the roll axis below the CG (although in theory it can be above the CG). The roll axis is determined by the suspension arms. Two effects: the leverage exerted by the suspension geometry and the spring rates including roll bar rates (roll bars act at half the spring rate of the bar as the bar uses the outside spring as the end of a lever arm which compress the inside spring reducing body roll as well as lowering the car a small amount. It is the compression of the inside spring that reduces the body roll).

Some very fast cars use very soft springs and roll quite a bit. A recent episode of Top Gear America showed two camera cars: one for on road pursuit and one for off road which illustrated this quite graphically. WRC use very soft springs for a competition car for gravel or snow, relatively speaking.

F1 cars use excessively stiff springs for Aero effects. In days gone by, before wings and ground effects F1 cars rolled quite noticeably. Were it not for the requirements of aerodynamic downforce F1 cars would run much softer springs than they to today.

The main reason for using stiffer springs is to reduce suspension travel in order to lower ride height. The main reason for using roll bars instead of stiffer springs is to preserve ride comfort. Roll bars cannot be used to increase spring rates required for chassis lowering. Many road car designers have refused to use roll bars. The idea of roll bars is to reduce the spring rate otherwise required to keep suspension alignment within limits, particularly camber.

If you fit wider low profile tires to a car you need to increase roll resistance to prevent loss of grip due to excessive camber changes with suspension compliance. You could just use stiffer springs or a higher roll axis.

Regardless of those modifications you will not effect any changes in weight transfer. You will reduce the ability of the drive axle to apply power due to the lifting effect of the roll bar on the inside drive wheel. Put another way, the roll bar, or stiffer springs, will effect weight transfer at a faster rate as you corner. Total suspension travel will also be reduced for a given cornering force, which is generally a bad idea for a road car.
 

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Discussion Starter #16
I describe only the physics of "weight transfer" which is a misnomer but descriptive. There is nothing to agree or disagree with. Draw a diagram and add some numbers and the arithmetic will illustrate my statements.

Body roll results from the moment created by lateral forces generated at the tire contact patches, reacted to by the suspension arms and the springs/roll bars. That moment results from the lever arm created by the height of the CG above the ground. That lever arm operates on the suspension arms which compress the springs at a rate determined by the height of the roll axis below the CG (although in theory it can be above the CG). The roll axis is determined by the suspension arms. Two effects: the leverage exerted by the suspension geometry and the spring rates including roll bar rates (roll bars act at half the spring rate of the bar as the bar uses the outside spring as the end of a lever arm which compress the inside spring reducing body roll as well as lowering the car a small amount. It is the compression of the inside spring that reduces the body roll).

Some very fast cars use very soft springs and roll quite a bit. A recent episode of Top Gear America showed two camera cars: one for on road pursuit and one for off road which illustrated this quite graphically. WRC use very soft springs for a competition car for gravel or snow, relatively speaking.

F1 cars use excessively stiff springs for Aero effects. In days gone by, before wings and ground effects F1 cars rolled quite noticeably. Were it not for the requirements of aerodynamic downforce F1 cars would run much softer springs than they to today.

The main reason for using stiffer springs is to reduce suspension travel in order to lower ride height. The main reason for using roll bars instead of stiffer springs is to preserve ride comfort. Roll bars cannot be used to increase spring rates required for chassis lowering. Many road car designers have refused to use roll bars. The idea of roll bars is to reduce the spring rate otherwise required to keep suspension alignment within limits, particularly camber.

If you fit wider low profile tires to a car you need to increase roll resistance to prevent loss of grip due to excessive camber changes with suspension compliance. You could just use stiffer springs or a higher roll axis.

Regardless of those modifications you will not effect any changes in weight transfer. You will reduce the ability of the drive axle to apply power due to the lifting effect of the roll bar on the inside drive wheel. Put another way, the roll bar, or stiffer springs, will effect weight transfer at a faster rate as you corner. Total suspension travel will also be reduced for a given cornering force, which is generally a bad idea for a road car.
Can I ask what your definition of 'weight transfer' is?
 

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Can I ask what your definition of 'weight transfer' is?
Same as everyone's.

The moment created by the lateral or longitudinal grip of the tires and the mass of the car assumed to accelerate through its CG.

Assuming tires generate a cornering force of 1,000 lbs and the CG is at height of 2 ft then the moment is 2,000 lb ft. That moment will increase the effective weight (not the actual weight, you understand) on the outside tire by the twisting force exerted on the body of the car. Being torque this moment may or may not cause the body to roll and the amount of roll will depend on the proportion of torque resisted by the suspension geometry (roll axis) and the proportion resisted by the springs including any roll bars. This moment will always and must always effect the same weight transfer regardless of suspension geometry or spring rates, by definition.

Weight transfer continues even if the outside suspension compresses fully and even if the inside wheel lifts off the road as long as cornering forces generated by the tires continue to rise. Once the spring is fully compressed against the bump stop no further body roll can occur but, as you can see from many pictures of old rwd touring cars (or modern Aussie racing V8 cars) and any number of fwd hot hatches, wheel lifting is very common. The wheel could not lift if weight transfer depended upon body roll. Incidentally, this is why choice of roll bar and spring rates is critical in order to maintain traction for acceleration coming out of corners. Ultimateky, restricting body roll by increasing spring or bar rates reduces ultimate achievable grip. F1 cars experience this deficiency under braking (evidenced by the inside front wheel locking) since an LSD reduces the impact of the effect at the drive wheels (F1 cars are so stiff in roll you can drive one with an entire wheel missing).

The total weight transfer will be the same for all chassis designs experiencing 2,000 lb ft of torque but the amount of body roll will differ with these proportions of roll centre height and spring or bar rates. The higher the roll axis the less the body roll. Weight transfer remains the same. Lowering the CG does not affect the assumed values (2,000 lb ft at a 1 ft high CG assumes the cornering force is 2,000 lbs) but of course if the tires generate only 1,000 lbs of side force and the CG is at 1 ft height the torque will be only 1,000 lb ft and weight transfer accordingly halved.

More importantly, and this is the part the ricer crowd has no understanding of, body roll will have no effect on tire grip resulting from weight transfer effects until suspension alignment passes the point of ideal contact patch alignment of the tires. For most road cars with fairly narrow section tires roll angle is not relevant to the total tire grip developed. If roll angle changes camber away from the ideal then and only then is it worth reducing body roll.

Even if reducing body roll is advantageous weight transfer is not affected by reduction in body roll.
 
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