More info about shocks than you want to know.
#1
03-30-2009, 09:32 AM
More info about shocks than you want to know.
I get PMs like this regularly, so after masking this user's ID, I thought I'd share the info with all of you. NOTE: long probably boring read.
Dear Bouncing,
My wife and I have been national level autocross racers since 2001, with 2 national championship wins. In our sport, suspension tuning is the most critical component besides the driver and the difference between winning and losing is measured in thousandths of a second. Consequently I have spent and continue to spend a considerable amount of time studying and testing suspension components.Now to your questions: Shocks, when they are properly matched to the rest of the suspenion (springs primarily) play only a small role in ride comfort compared to their affect on handling. Shocks, or more properly spring dampers, primary function is to control the springs natural tendency to oscillate or continue bouncing once set into motion. Think of your undamped springs as a rubber ball, say a hollow soft rubber ball. Toss the ball into the air and when it comes down and strikes the ground it bounces back up. This up and down bouncing continues for some time. Now to damp that bouncing we introduce a damper. In our rubber ball test we put the ball inside a bean bag with just the right amount of beans so that when the ball comes back down it just barely bounces back up after the first strike and then gently comes back to rest. That is an example of a properly calibrated damper for the natural oscillation rate of that ball. Now if we replace the softer ball in that bean bag damper with a superball (which has a much higher oscillation rate) of the same size and test it again, the ball is likely to bounce several times before coming to rest. We call that "underdamped". Continue to add more beans until the superball behaves the same as the soft ball did with the original amount of beans. Now we are back to proper or "balanced" damping for that spring (ball). Retaining the new number of beans in the bag we switch back to the soft ball. Tossing it into the air results in it going solidly SPLAT on the ground with no bounce what so ever, in fact the ball itself may not have even touched the ground because of the amount of beans. This condition is "overdamped" where the beans (damper) overpowered the springs and have taken over some or all of the spring's function.When a vehicle's springs are underdamped it hits a bump and continues bouncing down the road. If overdamped, instead of the springs absorbing the bump the very stiff shocks resist the spring's function. They act like a very stiff spring and you get a very harsh ride. The very best situation is where the dampers are balanced to the spring rate so the vehicle quickly stops bouncing but in a smooth manner by first allowing the spring to absorb most or all of the initial impact then settling back to it's at rest state.There are a lot of factors that come into play in achieving that balanced damped state: 1. the spring rate. 2. the weight of the vehicle on that axle. 3. the severity of the bump. 4. the mounting angle of the shock. (laying the shock over more towards horizontal the less damping you will get, The maximum bounce damping is with the shock mounted vertically.)Examining each in sequence:1. The spring rate can be determined by asking the manufacturer if new, or by physically testing the spring. (A worn or rusty leaf spring may have binding issues which results in an uneven catch and release spring rate. Balanced damping can never be achieved.)2. the weight of the vehicle on each axle can be determined with a scale, but will change significantly with changing load (in a pickup especially). Damping needs to be a compromise when the weight is constantly variable and at best is calibrated for the average or mean (most common) weight. 3. A race vehicle is much more easily precisely damped since most racetracks are relatively smooth. A street vehicle once again has to be compromise damped to the size of the mean sized bump or slightly less if most driving is done on smooth roads with an occasional bump. Underdamped is more pleasant a ride than overdamped. 4. Again a drag racing car only travels in a straight line so the dampers are mounted true vertically and damped just for the spring rate. However in a street or racing vehicle that makes turns we have another force to deal with, centrifugal weight transfer or more simply "body lean or roll". The shocks are also used to control body roll or weight transfer. This force is at an angle to the ground plane, so is best damped by mounting the shock at this angle. Since the shock must damp both bounce and body roll produced oscillations a comprimise mounting angle is used depending on primary damping needs. A street vehicle where ride and rough surface bumps are primary may be comprimised more towards the vertical whereas a a road race or sports vehicle where handling on turns is primary may have it's dampers mounted at more of an angle.Since there are all these variables to be resolved in determining the shock valving or damping rate, a manufacturer of performance shocks for off the shelf sales (as opposed to custom built) will damp for the most common conditions of a specific application then add an external adjuster to allow fine tuning by the owner to the needs of a specific vehicle. Inexpensive shocks will all be valved about the same regardless of application and use higher manufacturing tollerances and cheaper materials to maximize profits, figuring that anyone buying shocks on price alone can't tell the difference, and since the accellerated wear they will exhibit is progressive that bargain shopper won't notice how fast they wear out until they need a new set, which generates still more sales and profit.
AFA coil overs: shocks with helper springs mounted on the outside are often erroniously refered to as "coil overs". The helper springs (or air shocks as another type of helper spring equipped shock) are just that. The spring built into the shock is meant to be additional to the primary OEM springs. This may be to allow more load carrying capacity on occasion (such as when pulling a heavy trailer) without using stiffer main springs all the time or to suppliment sagging worn springs (a bandaid approach to a different problem). This function is a crutch and has little/nothing to do with the shock's damping control.True coil overs are a suspension member. The main and only spring is installed around the shock with the upper and lower spring perch being attached to the shock rather than attached to the control arms/axle and chassis as they are in traditional coil sprung suspensions. If you remove a coil over shock you are also removing the primary spring for that wheel and if you then released the supporting jack that corner of the vehicle would come crashing down.The primary attraction of coilovers are their adjustability and the fact that the spring's direction of compression/rebound is exactly the same and concentric to the maximum damping of the shock.Coilovers have at least one removable perch that allows easy spring changes and the diameter of the perches are somewhat standardized in diameter so aftermarket spring manufacturers produce a wide range of springs with different rates, lengths and characteristics to select from.Some also have an adjustable lower perch that can be raised or lowered to adjust the ride height and the roll center of the vehicle which can also be used as a chassis tuning method.Since the spring and damper are working in direct concert and concentrically the damping can be set precisely through it's entire range of travel for that spring.Coilovers are typically used on lightweight sports or road racing type vehicles with their major emphasis on handling capabilities and adjustability. It is difficult to fit a stiff enough spring onto a coilover to support a heavy vehicle and still have it function properly and not tear the necessary lightweight construction apart. In cases where it is desirable to use coilovers on a heavy vehicle (such as an SJ Jag rear) two coilovers are used per side to share the load (and the damping).Now you probably know more about shocks than you wanted to, and considerably more than the average driver, I hope I have answered your questions and provided direction for your shock selection. If not feel free to ask for more info. I think I'll post most of ths to the forum since it is an area that is poorly understood and the info may be useful to a lot of the people there. (and since I seem to have written a book, I might as well let it be read by others.)
Originally Posted by anonymous
AXracer,
I've been doing some reading and people have said that you are quite knowledgable about suspension components. I have a question about rear shocks. I'm looking for a nice comfortable ride with my '56 and my current shocks are leaking. I have a Ford 9" with leaf springs. I was wondering the difference between coil over and regular shocks (are coil overs worth it?). Adjustable? Is it better to buy expensive or just middle of the road? Any help would be appreciated.
signed Bouncing around
I've been doing some reading and people have said that you are quite knowledgable about suspension components. I have a question about rear shocks. I'm looking for a nice comfortable ride with my '56 and my current shocks are leaking. I have a Ford 9" with leaf springs. I was wondering the difference between coil over and regular shocks (are coil overs worth it?). Adjustable? Is it better to buy expensive or just middle of the road? Any help would be appreciated.
signed Bouncing around
My wife and I have been national level autocross racers since 2001, with 2 national championship wins. In our sport, suspension tuning is the most critical component besides the driver and the difference between winning and losing is measured in thousandths of a second. Consequently I have spent and continue to spend a considerable amount of time studying and testing suspension components.Now to your questions: Shocks, when they are properly matched to the rest of the suspenion (springs primarily) play only a small role in ride comfort compared to their affect on handling. Shocks, or more properly spring dampers, primary function is to control the springs natural tendency to oscillate or continue bouncing once set into motion. Think of your undamped springs as a rubber ball, say a hollow soft rubber ball. Toss the ball into the air and when it comes down and strikes the ground it bounces back up. This up and down bouncing continues for some time. Now to damp that bouncing we introduce a damper. In our rubber ball test we put the ball inside a bean bag with just the right amount of beans so that when the ball comes back down it just barely bounces back up after the first strike and then gently comes back to rest. That is an example of a properly calibrated damper for the natural oscillation rate of that ball. Now if we replace the softer ball in that bean bag damper with a superball (which has a much higher oscillation rate) of the same size and test it again, the ball is likely to bounce several times before coming to rest. We call that "underdamped". Continue to add more beans until the superball behaves the same as the soft ball did with the original amount of beans. Now we are back to proper or "balanced" damping for that spring (ball). Retaining the new number of beans in the bag we switch back to the soft ball. Tossing it into the air results in it going solidly SPLAT on the ground with no bounce what so ever, in fact the ball itself may not have even touched the ground because of the amount of beans. This condition is "overdamped" where the beans (damper) overpowered the springs and have taken over some or all of the spring's function.When a vehicle's springs are underdamped it hits a bump and continues bouncing down the road. If overdamped, instead of the springs absorbing the bump the very stiff shocks resist the spring's function. They act like a very stiff spring and you get a very harsh ride. The very best situation is where the dampers are balanced to the spring rate so the vehicle quickly stops bouncing but in a smooth manner by first allowing the spring to absorb most or all of the initial impact then settling back to it's at rest state.There are a lot of factors that come into play in achieving that balanced damped state: 1. the spring rate. 2. the weight of the vehicle on that axle. 3. the severity of the bump. 4. the mounting angle of the shock. (laying the shock over more towards horizontal the less damping you will get, The maximum bounce damping is with the shock mounted vertically.)Examining each in sequence:1. The spring rate can be determined by asking the manufacturer if new, or by physically testing the spring. (A worn or rusty leaf spring may have binding issues which results in an uneven catch and release spring rate. Balanced damping can never be achieved.)2. the weight of the vehicle on each axle can be determined with a scale, but will change significantly with changing load (in a pickup especially). Damping needs to be a compromise when the weight is constantly variable and at best is calibrated for the average or mean (most common) weight. 3. A race vehicle is much more easily precisely damped since most racetracks are relatively smooth. A street vehicle once again has to be compromise damped to the size of the mean sized bump or slightly less if most driving is done on smooth roads with an occasional bump. Underdamped is more pleasant a ride than overdamped. 4. Again a drag racing car only travels in a straight line so the dampers are mounted true vertically and damped just for the spring rate. However in a street or racing vehicle that makes turns we have another force to deal with, centrifugal weight transfer or more simply "body lean or roll". The shocks are also used to control body roll or weight transfer. This force is at an angle to the ground plane, so is best damped by mounting the shock at this angle. Since the shock must damp both bounce and body roll produced oscillations a comprimise mounting angle is used depending on primary damping needs. A street vehicle where ride and rough surface bumps are primary may be comprimised more towards the vertical whereas a a road race or sports vehicle where handling on turns is primary may have it's dampers mounted at more of an angle.Since there are all these variables to be resolved in determining the shock valving or damping rate, a manufacturer of performance shocks for off the shelf sales (as opposed to custom built) will damp for the most common conditions of a specific application then add an external adjuster to allow fine tuning by the owner to the needs of a specific vehicle. Inexpensive shocks will all be valved about the same regardless of application and use higher manufacturing tollerances and cheaper materials to maximize profits, figuring that anyone buying shocks on price alone can't tell the difference, and since the accellerated wear they will exhibit is progressive that bargain shopper won't notice how fast they wear out until they need a new set, which generates still more sales and profit.
AFA coil overs: shocks with helper springs mounted on the outside are often erroniously refered to as "coil overs". The helper springs (or air shocks as another type of helper spring equipped shock) are just that. The spring built into the shock is meant to be additional to the primary OEM springs. This may be to allow more load carrying capacity on occasion (such as when pulling a heavy trailer) without using stiffer main springs all the time or to suppliment sagging worn springs (a bandaid approach to a different problem). This function is a crutch and has little/nothing to do with the shock's damping control.True coil overs are a suspension member. The main and only spring is installed around the shock with the upper and lower spring perch being attached to the shock rather than attached to the control arms/axle and chassis as they are in traditional coil sprung suspensions. If you remove a coil over shock you are also removing the primary spring for that wheel and if you then released the supporting jack that corner of the vehicle would come crashing down.The primary attraction of coilovers are their adjustability and the fact that the spring's direction of compression/rebound is exactly the same and concentric to the maximum damping of the shock.Coilovers have at least one removable perch that allows easy spring changes and the diameter of the perches are somewhat standardized in diameter so aftermarket spring manufacturers produce a wide range of springs with different rates, lengths and characteristics to select from.Some also have an adjustable lower perch that can be raised or lowered to adjust the ride height and the roll center of the vehicle which can also be used as a chassis tuning method.Since the spring and damper are working in direct concert and concentrically the damping can be set precisely through it's entire range of travel for that spring.Coilovers are typically used on lightweight sports or road racing type vehicles with their major emphasis on handling capabilities and adjustability. It is difficult to fit a stiff enough spring onto a coilover to support a heavy vehicle and still have it function properly and not tear the necessary lightweight construction apart. In cases where it is desirable to use coilovers on a heavy vehicle (such as an SJ Jag rear) two coilovers are used per side to share the load (and the damping).Now you probably know more about shocks than you wanted to, and considerably more than the average driver, I hope I have answered your questions and provided direction for your shock selection. If not feel free to ask for more info. I think I'll post most of ths to the forum since it is an area that is poorly understood and the info may be useful to a lot of the people there. (and since I seem to have written a book, I might as well let it be read by others.)
#2
03-30-2009, 12:02 PM
Post Fiend
#3
03-30-2009, 12:30 PM
#4
03-30-2009, 01:52 PM
Rusty, trust me today's shock are so far ahead of the OEMs used then, (or even most of the OEMs used today, they still use whatever the lowest bidder provides.) that you really wouldn't want them. The better shock manufacturers i.e. Koni, Bilstein, QA1 are noticing the size of our market and that we prefer and appreciate a quality product even if it costs a little more. A cheaply made discount house mass market brand shock is ~ 30.00, starts going downhill immediately and are scrap by 15K miles. A high quality single adjustable shock runs in the 120.00 each range, but come with a lifetime warantee and in most cases can be revalved if needed.
Little is a relative term tho in some cases. The custom built and valved Penske aluminum double adjustable racing shocks on our Solstice cost 2700.00 a set! A set for a Formula 1 or a 24hrs at Daytona prototype car can run upwards of 12K a set!
PS, I hope I don't offend you and your choice, but in truth when you buy a Monroe the purchase price is mostly to cover the advertising, not the shock.
Little is a relative term tho in some cases. The custom built and valved Penske aluminum double adjustable racing shocks on our Solstice cost 2700.00 a set! A set for a Formula 1 or a 24hrs at Daytona prototype car can run upwards of 12K a set!
PS, I hope I don't offend you and your choice, but in truth when you buy a Monroe the purchase price is mostly to cover the advertising, not the shock.
#5
03-30-2009, 05:27 PM
Monroe On-Line Catalog, Shock Selector, and Application Information
Use the Shock Selection Guide - it goes back to 1948 for Ford Pickups and gives some choices.
Use the Shock Selection Guide - it goes back to 1948 for Ford Pickups and gives some choices.
#6
03-30-2009, 06:52 PM
Rusty, trust me today's shock are so far ahead of the OEMs used then, (or even most of the OEMs used today, they still use whatever the lowest bidder provides.) that you really wouldn't want them. The better shock manufacturers i.e. Koni, Bilstein, QA1 are noticing the size of our market and that we prefer and appreciate a quality product even if it costs a little more. A cheaply made discount house mass market brand shock is ~ 30.00, starts going downhill immediately and are scrap by 15K miles. A high quality single adjustable shock runs in the 120.00 each range, but come with a lifetime warantee and in most cases can be revalved if needed.
Little is a relative term tho in some cases. The custom built and valved Penske aluminum double adjustable racing shocks on our Solstice cost 2700.00 a set! A set for a Formula 1 or a 24hrs at Daytona prototype car can run upwards of 12K a set!
PS, I hope I don't offend you and your choice, but in truth when you buy a Monroe the purchase price is mostly to cover the advertising, not the shock.
Little is a relative term tho in some cases. The custom built and valved Penske aluminum double adjustable racing shocks on our Solstice cost 2700.00 a set! A set for a Formula 1 or a 24hrs at Daytona prototype car can run upwards of 12K a set!
PS, I hope I don't offend you and your choice, but in truth when you buy a Monroe the purchase price is mostly to cover the advertising, not the shock.
Well thats the only reasion why I get the Monroe, they are the only one for most of my vehicles and in my price range. Cant justify spending say $120 for one shock absober just to paint it the OEM factory color. But I havent had a problem with them though and they last long enough for me. Vehicle that I drive the most I only put something on the lines of 700 - 1200 miles a year on it.
Only thing that would effect the choice on shocks on the 56 is if I could get something to give a smooth ride but as well as look orignal since I am done with fabrication and modifications.
I did come across this leaf spring helper or what ever its called that fits under the axle plate on the spring and fits to the front end of the axle mounting bushing. Supposed to stop the axle from twisting when accelerating or braking by keeping the front spring from flexing.
#7
03-30-2009, 07:13 PM
Monroe On-Line Catalog, Shock Selector, and Application Information
Use the Shock Selection Guide - it goes back to 1948 for Ford Pickups and gives some choices.
Use the Shock Selection Guide - it goes back to 1948 for Ford Pickups and gives some choices.
Was looking for a shock site awhile back. Put a bookmark on it.
Trending Topics
#8
03-30-2009, 08:17 PM
#9
03-30-2009, 08:56 PM
AX, I have a buddy that's into AutoX racing, at one point he raced with a 2000 GTI, then a caged Miata, then an S2000. What a blast, but I never trusted myself to be able to follow the course under pressure...
Anyway, I have two follow up questions...Will a 1960 F100 ever handle "well" around corners? Could you make one into an Auto Cross racer, if you were so inclined? One of the vehicles that went to his meets that cleaned up every time was a 65 GT350 with manual brakes and steering. It was fast. I know it's different with a straight axle up front, but it would seem like if the springs were stiff enough, it would stay flat. What are your thoughts?
Question 2: If I were shopping for new springs for the F100, what spring rate would I want for something to handle well around corners and hook up when accelerating? Bear in mind, I have no idea how spring rate is even mentioned.
Anyway, thanks for the detailed explanation above.
D
Anyway, I have two follow up questions...Will a 1960 F100 ever handle "well" around corners? Could you make one into an Auto Cross racer, if you were so inclined? One of the vehicles that went to his meets that cleaned up every time was a 65 GT350 with manual brakes and steering. It was fast. I know it's different with a straight axle up front, but it would seem like if the springs were stiff enough, it would stay flat. What are your thoughts?
Question 2: If I were shopping for new springs for the F100, what spring rate would I want for something to handle well around corners and hook up when accelerating? Bear in mind, I have no idea how spring rate is even mentioned.
Anyway, thanks for the detailed explanation above.
D
#10
03-30-2009, 09:41 PM
Fleet Owner
Dick, as I noted in a post some time ago, their current shocks for F-1's allow the front axle to drop further than the rubber brake hose can stretch -- so if you jack your truck by the frame, you will instantly ruin your brake hoses. In other words, they have something that "fits", but not right.
#11
03-30-2009, 11:20 PM
I'll tell ya why I put in the link to Monroe - I was at a retirement home the other day visiting a Friend. I was watching what the staff was doing - the were playing with the inmates with beanbags and softballs, while listening to Big Band muzak.
When I read AX sermon on the 4post lift I just had to most his reference to monroe.
Does anyone know when they will start playng Zeplan & The Who in retirement homes.
My friend has to eat in his room because the Dining Room is Dress Clothes. He walked in one night with his pants and shirt in hand, got everyones attention and said Undress - clothes and shook his pants and shirt - He the put them on amd pointed to himself and said - Look Dressed Clothes. I think he just drove too many bikes into trees doing Moto-Crash - He never was any good at it.
When I read AX sermon on the 4post lift I just had to most his reference to monroe.
Does anyone know when they will start playng Zeplan & The Who in retirement homes.
My friend has to eat in his room because the Dining Room is Dress Clothes. He walked in one night with his pants and shirt in hand, got everyones attention and said Undress - clothes and shook his pants and shirt - He the put them on amd pointed to himself and said - Look Dressed Clothes. I think he just drove too many bikes into trees doing Moto-Crash - He never was any good at it.
#12
03-30-2009, 11:46 PM
AX, I have a buddy that's into AutoX racing, at one point he raced with a 2000 GTI, then a caged Miata, then an S2000. What a blast, but I never trusted myself to be able to follow the course under pressure...
Anyway, I have two follow up questions...Will a 1960 F100 ever handle "well" around corners? Could you make one into an Auto Cross racer, if you were so inclined? One of the vehicles that went to his meets that cleaned up every time was a 65 GT350 with manual brakes and steering. It was fast. I know it's different with a straight axle up front, but it would seem like if the springs were stiff enough, it would stay flat. What are your thoughts?
Question 2: If I were shopping for new springs for the F100, what spring rate would I want for something to handle well around corners and hook up when accelerating? Bear in mind, I have no idea how spring rate is even mentioned.
Anyway, thanks for the detailed explanation above.
D
Anyway, I have two follow up questions...Will a 1960 F100 ever handle "well" around corners? Could you make one into an Auto Cross racer, if you were so inclined? One of the vehicles that went to his meets that cleaned up every time was a 65 GT350 with manual brakes and steering. It was fast. I know it's different with a straight axle up front, but it would seem like if the springs were stiff enough, it would stay flat. What are your thoughts?
Question 2: If I were shopping for new springs for the F100, what spring rate would I want for something to handle well around corners and hook up when accelerating? Bear in mind, I have no idea how spring rate is even mentioned.
Anyway, thanks for the detailed explanation above.
D
#13
03-31-2009, 12:29 AM
Senior User
Join Date: Aug 2008
Location: Pueblo, Co.
Posts: 153
Likes: 0
Received 0 Likes
on
0 Posts
Great shock/spring and suspension info AX!......I even understood it!!...lol....it's amazing what "info" comes back to a person, once you have the need to use it again!....I agree with you as well on the Factory Five car's, really high quality stuff....(my son recently got a bunch of info from them)
Later, Doug
Later, Doug
#14
03-31-2009, 01:19 PM
Senior User
Join Date: Sep 2007
Location: Atwater, CA
Posts: 206
Likes: 0
Received 0 Likes
on
0 Posts
Ax,
Wow!!! Great info. You are The Man!!!
Maybe I'm a little slow on the uptake, but if I'm running leaf springs and a traction bar in the rear, I wouldn't need coil overs then? If I read everything right, coil over shocks act as the spring for the rear when running something like a 4-bar setup. So coil overs in a setup like mine would be overkill?
Shane
Wow!!! Great info. You are The Man!!!
Maybe I'm a little slow on the uptake, but if I'm running leaf springs and a traction bar in the rear, I wouldn't need coil overs then? If I read everything right, coil over shocks act as the spring for the rear when running something like a 4-bar setup. So coil overs in a setup like mine would be overkill?
Shane
