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Okay, since it seems I'm not the only one here who could learn more, here's another article on
suspension management.
Copyright 1996 Information Access Company, a Thomson Corporation Company
ASAP
Copyright 1996 Bill Communications Inc.
Modern Tire Dealer
April, 1996
SECTION: Vol. 77 ; No. 4 ; Pg. S32; ISSN: 0026-8496
LENGTH: 2272 words
HEADLINE: Ride control: performance suspension management.1996 Performance Handbook
BYLINE: Mavrigian, Mike
BODY:
The term "ride control," in its most complete sense, includes the vehicle's entire suspension system, including springs, shock absorbers, bushings, wheel alignment, sway control systems and tires. Each product area is responsible in part for the manner in which the vehicle rides, handles and stops.
Since we've already covered the subject of anti-sway bars elsewhere in this issue, here's we'll address the need for upgrading springs, shocks and bushings.
Springs
The chassis springs control the vehicle's static ride height, so spring evaluation should be the very first order of business when maintaining, repairing or upgrading any vehicle's suspension. Even though the springs represent the basis of the suspension, they're all too often overlooked. The ride height should always be measured first. Reference the vehicle's factory service manual or an aftermarket spring maker's fitment guide to determine where the measuring points are located on a particular vehicle, and what the minimum and maximum ride heights specs are.
Aftermarket coil springs are available with varying tension rates and in various compressed heights. Rather than playing guessing games in terms of ride stiffness and height, follow the advice of the spring maker.
They have an enormous investment in design and testing, and they know what the characteristics are on any given type of vehicle.
A common mistake that many enthusiasts make is to purchase replacement springs that are too low and stiff, and to compound the problem with stiffly valved shocks. While they may be able to soften the shocks (providing they're adjustable), correcting the spring situation means purchasing new springs and performing the changeover work again. Aside from an extensive trial and error procedure, the best advice, in terms of obtaining the desired height, ride quality and handling characteristics, is for your customers to purchase a matched set of springs and shocks recommended by the spring or shock maker for the vehicle and intended use.
When installing your customers' coil springs, make absolutely certain that the top and bottom of the spring is properly positioned within the spring seats. At least one of the spring seats, and often both, will feature a formed seat pocket, providing a definite "stop" for the end of the coil.
Be sure that the blunt end of a coil spring wire is seated against that coil stop. On "flat" coil spring ends that feature a tapered wire end, position doesn't matter.
Shocks
Shock absorbers control more than "body bounce." Shocks are responsible for damping excess wheel movement (if you can't keep the tire on the pavement, the finest performance tires on the market can't be used to their fullest extent). Shocks also control the vehicle body's tendency to wander and "float."
Shocks dampen excess body movement during acceleration, braking, lane changes and all cornering maneuvers. They're an integral component in terms of steering control, vehicle tracking, handling and braking.
If shocks are too soft, the vehicle's braking will be inefficient (stopping distances will actually increase), steering response will be sluggish, overall vehicle control will be diminished and traction will suffer, especially on rough road surfaces. If the shocks are too stiff, the ride will be harsh, and control will be lessened on rough roads.
In terms of providing damping control for the chassis, "conventional" shock absorbers and struts are the same - they're all "shock absorbers."
While some shocks utilize hydraulic oil and a system of orificed valves, others - "gas" shocks - add the use of pressurized nitrogen gas to exert a constant pressure on the shock's hydraulic oil.
This prevents foaming and loss of viscosity, which would otherwise occur when a weak inexpensive hydraulic shock is over-exerted.
Once the spring issue is resolved, the ride can be tailored to the driver's requirements with the selection of the appropriate shocks.
A wide range of suspension dampers are available, from OE-soft to race-car stiff, and everywhere in between. In fact, several shock makers offer adjustable units that can easily be calibrated to suit an individual's preferences.
If you do select an adjustable shock or strut, try to choose a design that offers an easy adjustment procedure. While some shocks must be dismounted, manually compressed (to engage the valve adjuster) and rotated to achieve stiffness adjustment, other designs can be adjusted with the simple click of a dial or use of an allen wrench, without the need to dismount the shock from the vehicle.
Some models are also available that offer remote valving control (from the driver's seat). These are usually activated using compressed air power. A small underhood air compressor sends compressed air through small-diameter plastic lines to each shock. The air pressure is used to adjust the valving (in lieu of turning a **** manually at each shock).
A superior-handling vehicle will make use of a balanced system of anti-sway bars, high-durometer bushings, springs, shocks, wheels and tires.
Considering the advances made in all of these areas, the desire for superior handling does not automatically translate into a stiff, bone-jarring ride. It is possible to create a performance-oriented street package that provides completely acceptable ride qualities.
Bushings
We mentioned in the anti-sway bar article how the use of stiff, less compliant urethane bushings can improve the efficiency and performance of the bar. In addition, other areas of the suspension can also be improved through the use of replacement bushings to create superior handling and braking.
Front control arm bushings, especially soft rubber bushings that have become aged through use, can allow the front suspension control arms to deflect during cornering. When these rubber bushings deflect, they allow the control arms to move fore and aft (under acceleration and braking and cornering) and can allow the control arms to pivot in an erratic and eccentric arc.
The result is a change in wheel camber angle during cornering. This causes sloppy handling and wheel control, a loss of steering response, and can lead to irregular tire wear due to the camber changes that occur when the suspension compresses and rebounds.
Granted, the use of hard urethane bushings at the control arm pivots may transmit more road feel (and subsequently more harshness) to the interior and steering wheel, but that's simply a side effect of the bushings' main purpose, which is to eliminate slop in control arm action and provide a firm and positive control.
By the same token, if the vehicle is equipped with rear trailing arms, the pivot bushings can be changed over to a harder urethane in the effort to maintain rear axle location and reduce wheel hop.
Strut rod bushings (on cars so equipped, these strut rods serve as a fore-aft brace between the lower control arm and the vehicle frame, preventing the front wheels from moving rearward under braking) are notorious for allowing excess lower control arm deflection.
If the lower control arm is allowed to deflect rearwards under braking, this changes the front wheel caster angle. The result is uneven, and less controlled braking during right or left maneuvers.
Installation of stiff urethane strut rod bushings (at the control arm and frame attachments) will prevent this excess deflection, allowing the caster angle to remain in a fixed angle. The benefits include handling and braking consistency and predictability.
If the vehicle is equipped with rear leaf springs, a changeover to stiff urethane bushings at the front and rear leaf eyelet mounts will eliminate the unwanted lateral lean of the spring within its mounts during hard turns.
Yes, the use of a stiffer bushing will allow more road feel to be transmitted through the leaf spring to the chassis, but if you want to stop the wishy-washy movement of the spring, this is part of the solution.
A switch to stiffer bushings isn't the right choice for every vehicle and every driver. In many cases, the less compliant bushings won't isolate the interior from road shock as the OE soft rubber bushings do. But if you want to extract more response and efficiency from the vehicle's suspension, urethane bushings make sense.
We've constantly referred to "urethane" bushings, although other bushing materials exist.
Urethane-type bushings seem to be the most popular today, as they have a reputation for being strong, resistant to breaking, and have a degree of lubricity. However, even the best bushings should not be installed dry (annoying little squeaks have been known to occur).
It's a good idea to coat the contact areas of these bushings with a dab of wheel bearing grease or lithium grease (some bushing makers even supply their own special lube).
Lowering a vehicle
On the plus-side, reducing the car's or truck's center of gravity will improve aerodynamics (in most cases, the closer the vehicle is to the ground, the less effort is required to push through the air). Lowering the vehicle, while maintaining the correct spring force, will also improve lateral handling, since body "roll" will be somewhat more limited.
On the down-side however, lowering the vehicle may create a negative camber change at the front wheels (and at the rear, if the vehicle offers independent rear suspension). Depending on how adjustable the suspension is, it may not be possible to regain the OE camber angles.
Another pronounced and potentially bothersome aspect of lowering deals with overall ground clearance.
If the vehicle is lowered beyond a safe distance, the vehicle may continually be subjected to bottoming and scraping on driveway inclines and uneven road surfaces, plus the shock absorbers may continually bottom-out internally, unless special shock mounts have been installed that mate the shocks to the specific lowering kit.
The answer: select a lowering package (this may consist of drop-spindles, springs and shocks) that is designed as a system. And pay attention to the manufacturer's guidelines for lowering.
If they recommend a three-inch drop on a certain vehicle, believe them. Too many enthusiasts have learned the hard way that the manufacturer usually knows what they're talking about.
Available truck lowering products include "drop spindles" (the spindle is relocated to a higher point relative to the ball joints, resulting in a lowering of the vehicle relative to the wheel), drop I-beams for Ford applications, lowering springs (can be used with or without drop spindles), rear leaf spring shackle kits and spacer blocks, flip kits (which allow you to relocate an axle to the top-side of the leaf spring pack for an even greater drop), replacement leaf spring packs, and even shocks designed to coordinate with a drop kit.
Alignment
A complete four-wheel-alignment should be an integral part of any performance suspension, immediately following any suspension upgrades and in the long haul.
If the vehicle's ride height has been altered, front camber, caster and toe will change (camber, and possibly toe will also be affected on the rear axle, if the rear is an independent suspension design). Whenever any load-bearing component is replaced, the alignment will probably change. That includes springs, control arms, control arm bushings or struts.
While front toe changes are readily handled on any vehicle, camber and caster adjustments are often made quite difficult due to a common lack of adjustment range in the OE suspension design.
Depending on the popularity of the vehicle, a growing selection of aftermarket adjustment aids are offered in the form of shims, strut tower adjusters and eccentric control arm bushings.
RELATED ARTICLE: BASIC TROUBLESHOOTING GUIDE
PROBLEMS AND PROBABLE CAUSES
Vehicles wanders, uncertain & lazy re: lane changes - worn control arm bushings, worn shocks, wheel alignment, or combination
Wanders in crosswind - worn shocks and/or control arm bushings
Lousy steering response - worn or inadequate shocks, wheel alignment, control arm bushings, anti-sway bar bushings, poor tire selection, underinflated tires
Poor tire grip on rough surfaces - tires overinflated, worn shocks, worn bushings; or suspension too stiff
Excessive brake lockup - brake problem, worn or weak shocks, worn control arm bushings and/or strut rod bushings, worn tires
Vehicle front "plows" in turns - understeer problem may be caused by "loose" rear suspension. Inspect all shocks, bushings. Rear may need new shocks, addition of anti-sway bar or both to balance the suspension.
Vehicle rear "hangs out" in turns - oversteer may be caused by too-stiff rear, or by need to further control the front by upgrading front anti-sway bar, shocks or both. Also check for overinflation of rear tires and wear of rear tire tread.
Vehicle "bottoms out" - worn shocks, sagged springs, vehicle lowered too far
Copyright 1996 Information Access Company, a Thomson Corporation Company
ASAP
Copyright 1996 Bill Communications Inc.
Modern Tire Dealer
April, 1996
SECTION: Vol. 77 ; No. 4 ; Pg. S32; ISSN: 0026-8496
LENGTH: 2272 words
HEADLINE: Ride control: performance suspension management.1996 Performance Handbook
BYLINE: Mavrigian, Mike
BODY:
The term "ride control," in its most complete sense, includes the vehicle's entire suspension system, including springs, shock absorbers, bushings, wheel alignment, sway control systems and tires. Each product area is responsible in part for the manner in which the vehicle rides, handles and stops.
Since we've already covered the subject of anti-sway bars elsewhere in this issue, here's we'll address the need for upgrading springs, shocks and bushings.
Springs
The chassis springs control the vehicle's static ride height, so spring evaluation should be the very first order of business when maintaining, repairing or upgrading any vehicle's suspension. Even though the springs represent the basis of the suspension, they're all too often overlooked. The ride height should always be measured first. Reference the vehicle's factory service manual or an aftermarket spring maker's fitment guide to determine where the measuring points are located on a particular vehicle, and what the minimum and maximum ride heights specs are.
Aftermarket coil springs are available with varying tension rates and in various compressed heights. Rather than playing guessing games in terms of ride stiffness and height, follow the advice of the spring maker.
They have an enormous investment in design and testing, and they know what the characteristics are on any given type of vehicle.
A common mistake that many enthusiasts make is to purchase replacement springs that are too low and stiff, and to compound the problem with stiffly valved shocks. While they may be able to soften the shocks (providing they're adjustable), correcting the spring situation means purchasing new springs and performing the changeover work again. Aside from an extensive trial and error procedure, the best advice, in terms of obtaining the desired height, ride quality and handling characteristics, is for your customers to purchase a matched set of springs and shocks recommended by the spring or shock maker for the vehicle and intended use.
When installing your customers' coil springs, make absolutely certain that the top and bottom of the spring is properly positioned within the spring seats. At least one of the spring seats, and often both, will feature a formed seat pocket, providing a definite "stop" for the end of the coil.
Be sure that the blunt end of a coil spring wire is seated against that coil stop. On "flat" coil spring ends that feature a tapered wire end, position doesn't matter.
Shocks
Shock absorbers control more than "body bounce." Shocks are responsible for damping excess wheel movement (if you can't keep the tire on the pavement, the finest performance tires on the market can't be used to their fullest extent). Shocks also control the vehicle body's tendency to wander and "float."
Shocks dampen excess body movement during acceleration, braking, lane changes and all cornering maneuvers. They're an integral component in terms of steering control, vehicle tracking, handling and braking.
If shocks are too soft, the vehicle's braking will be inefficient (stopping distances will actually increase), steering response will be sluggish, overall vehicle control will be diminished and traction will suffer, especially on rough road surfaces. If the shocks are too stiff, the ride will be harsh, and control will be lessened on rough roads.
In terms of providing damping control for the chassis, "conventional" shock absorbers and struts are the same - they're all "shock absorbers."
While some shocks utilize hydraulic oil and a system of orificed valves, others - "gas" shocks - add the use of pressurized nitrogen gas to exert a constant pressure on the shock's hydraulic oil.
This prevents foaming and loss of viscosity, which would otherwise occur when a weak inexpensive hydraulic shock is over-exerted.
Once the spring issue is resolved, the ride can be tailored to the driver's requirements with the selection of the appropriate shocks.
A wide range of suspension dampers are available, from OE-soft to race-car stiff, and everywhere in between. In fact, several shock makers offer adjustable units that can easily be calibrated to suit an individual's preferences.
If you do select an adjustable shock or strut, try to choose a design that offers an easy adjustment procedure. While some shocks must be dismounted, manually compressed (to engage the valve adjuster) and rotated to achieve stiffness adjustment, other designs can be adjusted with the simple click of a dial or use of an allen wrench, without the need to dismount the shock from the vehicle.
Some models are also available that offer remote valving control (from the driver's seat). These are usually activated using compressed air power. A small underhood air compressor sends compressed air through small-diameter plastic lines to each shock. The air pressure is used to adjust the valving (in lieu of turning a **** manually at each shock).
A superior-handling vehicle will make use of a balanced system of anti-sway bars, high-durometer bushings, springs, shocks, wheels and tires.
Considering the advances made in all of these areas, the desire for superior handling does not automatically translate into a stiff, bone-jarring ride. It is possible to create a performance-oriented street package that provides completely acceptable ride qualities.
Bushings
We mentioned in the anti-sway bar article how the use of stiff, less compliant urethane bushings can improve the efficiency and performance of the bar. In addition, other areas of the suspension can also be improved through the use of replacement bushings to create superior handling and braking.
Front control arm bushings, especially soft rubber bushings that have become aged through use, can allow the front suspension control arms to deflect during cornering. When these rubber bushings deflect, they allow the control arms to move fore and aft (under acceleration and braking and cornering) and can allow the control arms to pivot in an erratic and eccentric arc.
The result is a change in wheel camber angle during cornering. This causes sloppy handling and wheel control, a loss of steering response, and can lead to irregular tire wear due to the camber changes that occur when the suspension compresses and rebounds.
Granted, the use of hard urethane bushings at the control arm pivots may transmit more road feel (and subsequently more harshness) to the interior and steering wheel, but that's simply a side effect of the bushings' main purpose, which is to eliminate slop in control arm action and provide a firm and positive control.
By the same token, if the vehicle is equipped with rear trailing arms, the pivot bushings can be changed over to a harder urethane in the effort to maintain rear axle location and reduce wheel hop.
Strut rod bushings (on cars so equipped, these strut rods serve as a fore-aft brace between the lower control arm and the vehicle frame, preventing the front wheels from moving rearward under braking) are notorious for allowing excess lower control arm deflection.
If the lower control arm is allowed to deflect rearwards under braking, this changes the front wheel caster angle. The result is uneven, and less controlled braking during right or left maneuvers.
Installation of stiff urethane strut rod bushings (at the control arm and frame attachments) will prevent this excess deflection, allowing the caster angle to remain in a fixed angle. The benefits include handling and braking consistency and predictability.
If the vehicle is equipped with rear leaf springs, a changeover to stiff urethane bushings at the front and rear leaf eyelet mounts will eliminate the unwanted lateral lean of the spring within its mounts during hard turns.
Yes, the use of a stiffer bushing will allow more road feel to be transmitted through the leaf spring to the chassis, but if you want to stop the wishy-washy movement of the spring, this is part of the solution.
A switch to stiffer bushings isn't the right choice for every vehicle and every driver. In many cases, the less compliant bushings won't isolate the interior from road shock as the OE soft rubber bushings do. But if you want to extract more response and efficiency from the vehicle's suspension, urethane bushings make sense.
We've constantly referred to "urethane" bushings, although other bushing materials exist.
Urethane-type bushings seem to be the most popular today, as they have a reputation for being strong, resistant to breaking, and have a degree of lubricity. However, even the best bushings should not be installed dry (annoying little squeaks have been known to occur).
It's a good idea to coat the contact areas of these bushings with a dab of wheel bearing grease or lithium grease (some bushing makers even supply their own special lube).
Lowering a vehicle
On the plus-side, reducing the car's or truck's center of gravity will improve aerodynamics (in most cases, the closer the vehicle is to the ground, the less effort is required to push through the air). Lowering the vehicle, while maintaining the correct spring force, will also improve lateral handling, since body "roll" will be somewhat more limited.
On the down-side however, lowering the vehicle may create a negative camber change at the front wheels (and at the rear, if the vehicle offers independent rear suspension). Depending on how adjustable the suspension is, it may not be possible to regain the OE camber angles.
Another pronounced and potentially bothersome aspect of lowering deals with overall ground clearance.
If the vehicle is lowered beyond a safe distance, the vehicle may continually be subjected to bottoming and scraping on driveway inclines and uneven road surfaces, plus the shock absorbers may continually bottom-out internally, unless special shock mounts have been installed that mate the shocks to the specific lowering kit.
The answer: select a lowering package (this may consist of drop-spindles, springs and shocks) that is designed as a system. And pay attention to the manufacturer's guidelines for lowering.
If they recommend a three-inch drop on a certain vehicle, believe them. Too many enthusiasts have learned the hard way that the manufacturer usually knows what they're talking about.
Available truck lowering products include "drop spindles" (the spindle is relocated to a higher point relative to the ball joints, resulting in a lowering of the vehicle relative to the wheel), drop I-beams for Ford applications, lowering springs (can be used with or without drop spindles), rear leaf spring shackle kits and spacer blocks, flip kits (which allow you to relocate an axle to the top-side of the leaf spring pack for an even greater drop), replacement leaf spring packs, and even shocks designed to coordinate with a drop kit.
Alignment
A complete four-wheel-alignment should be an integral part of any performance suspension, immediately following any suspension upgrades and in the long haul.
If the vehicle's ride height has been altered, front camber, caster and toe will change (camber, and possibly toe will also be affected on the rear axle, if the rear is an independent suspension design). Whenever any load-bearing component is replaced, the alignment will probably change. That includes springs, control arms, control arm bushings or struts.
While front toe changes are readily handled on any vehicle, camber and caster adjustments are often made quite difficult due to a common lack of adjustment range in the OE suspension design.
Depending on the popularity of the vehicle, a growing selection of aftermarket adjustment aids are offered in the form of shims, strut tower adjusters and eccentric control arm bushings.
RELATED ARTICLE: BASIC TROUBLESHOOTING GUIDE
PROBLEMS AND PROBABLE CAUSES
Vehicles wanders, uncertain & lazy re: lane changes - worn control arm bushings, worn shocks, wheel alignment, or combination
Wanders in crosswind - worn shocks and/or control arm bushings
Lousy steering response - worn or inadequate shocks, wheel alignment, control arm bushings, anti-sway bar bushings, poor tire selection, underinflated tires
Poor tire grip on rough surfaces - tires overinflated, worn shocks, worn bushings; or suspension too stiff
Excessive brake lockup - brake problem, worn or weak shocks, worn control arm bushings and/or strut rod bushings, worn tires
Vehicle front "plows" in turns - understeer problem may be caused by "loose" rear suspension. Inspect all shocks, bushings. Rear may need new shocks, addition of anti-sway bar or both to balance the suspension.
Vehicle rear "hangs out" in turns - oversteer may be caused by too-stiff rear, or by need to further control the front by upgrading front anti-sway bar, shocks or both. Also check for overinflation of rear tires and wear of rear tire tread.
Vehicle "bottoms out" - worn shocks, sagged springs, vehicle lowered too far
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