- #1,716
hallpa00
- 4
- 0
RM - many thanks for the advice. I will do as you suggest and report back in 12 days!
Race car suspension Class
- Automotive
- Thread starter Ranger Mike
- Start date
-
- Tags
- Car Class Race Suspension
In summary,-The stock car suspension is important for understanding the complexity of a Formula Cars suspension.-When designing a (front) suspension, geometry layout is critical.-spindle choice and dimensions, kingpin and steering inclination, wheel offset, frame height, car track width, camber change curve, static roll center height and location and roll axis location are major factors.-The first critical thing to do is to establish the roll center height and lateral location. The roll center is established by fixed points and angles of the A-arms. These pivot points and angles also establish the camber gain and bump steer.-I have used Suspension Analyzer for years on Super late Model stock cars as
- #1,717
Cape15
- 11
- 2
RM- thank you for last few responses for me. I finally made it out to practice and my car actually rotates in the middle of the corner which is amazing since i have always been fighting with tight tight tight in the center of the corner. however i am slightly tight entering the corner and my RF tire is average 23 deg. more than the RR. I was thinking from all ive read through these posts that i might take out the RF spring of 325 that you recommended in my prior post and go to a 300 on the RF and go from there. Is that a good idea and would that ruin my center of corner? Also just curious as to your adjustments processes at the track or if there is a post you can direct me too that I might have missed on this thread. Thanks again!Ranger Mike said:
- #1,718
- 2,349
- 359
Yes a rt ft spring rate decrease is called for. Or add spring rate to right rear. Looks like we need to kill off some rt rear traction and cut down the PUSH.
You are very close.
you can soften the front ARB (sway bar) by lengthen the arm.
you can raise the rear roll center with panhard bar.
many options before swapping springs.
Try adding spring rubbers to right rear spring. quicker than swapping springs and better fine tuning.
these fine tune to 10#, 20# 25# a must to fine tune before spring swap
https://carolinaracingsupply.com/pr...oNfJg-sM18NQFdRVgY2GprXaapXvvnu4aAniYEALw_wcB
the rubbers below are over kill in my opinion but some racers use them.
1” spring rubber will approximately 100 lbs. ¾” is approximately 75 lbs.
https://www.speedwaymotors.com/Spee...9rFQjegyPdLVh4aa7clemUlwpqBvoKLcaAultEALw_wcB
post 1638 on track tuning. I have written about this but cant find it!
You are very close.
you can soften the front ARB (sway bar) by lengthen the arm.
you can raise the rear roll center with panhard bar.
many options before swapping springs.
Try adding spring rubbers to right rear spring. quicker than swapping springs and better fine tuning.
these fine tune to 10#, 20# 25# a must to fine tune before spring swap
https://carolinaracingsupply.com/pr...oNfJg-sM18NQFdRVgY2GprXaapXvvnu4aAniYEALw_wcB
the rubbers below are over kill in my opinion but some racers use them.
1” spring rubber will approximately 100 lbs. ¾” is approximately 75 lbs.
https://www.speedwaymotors.com/Spee...9rFQjegyPdLVh4aa7clemUlwpqBvoKLcaAultEALw_wcB
post 1638 on track tuning. I have written about this but cant find it!
Last edited:
- #1,719
- 2,349
- 359
Track Tuning Tips
See post 1419 on page 41 for driver tips
Track tuning
Two things any crew chief better have in the tool box , next to the Rolaids, are Stagger tape and a Tire Pyrometer. Preferably one with a memory that will permit you to take readings and will display three readings per tire.
Tire temperatures are the only real way to tell what is going on and it is empirical. Learn how to use the tire pyrometer and make a habit of doing it correctly. I have a nice techy one that tell you to stab the right front tire inside, middle and outside then move to the right rear tire. The cursor ques you where to take the readings. Insert the sensor needle 1/8 inch into the tire at a 45 degree angle and be consistent. You will be stabbing three places on the tire face. Inside edge ( not on the edge but an inch from the inside edge) the middle and the outside ( not the very outside..,an inch from the outside edge). When taking readings try to do it as soon as the driver comes off the track as these tires cool very quickly. Tune and test day is ideal as you can do it on the track if you are solo ones in that session. Then jack up the car and take tire stagger readings right front first. Record the tire growth and this will tell you about stagger.
The optimal tire temperatures should be in a range of 190 to 240 degrees. On a short track it is normal for the outside edge of the RF tire & the inside edge of the LF to be 5 to 10 degrees cooler. This is because of the way the tires travel down the straightaway. On a larger track with longer straights, this spread will be even further. On an oval, the RF tire will have more negative camber, thus resulting in the inside edge of the tire contacting the track more than the outside edge giving you the higher temperature. On the LF you will run with more positive camber, so just the opposite holds true. While cornering these temperatures should even out if you have the correct amounts of camber & or weight transfer. The more camber you run, the higher these spreads will be. On a small track were you spend a lot of time cornering, you'll find the spread not as high. This is because your spending more time cornering than on the straights, thus distributing the temperatures across the face of the tire more evenly. If you try to achieve even temps across the tire you may develop a push. This is telling you that you have too much positive camber. Although the tire may be flat on the track, on a straightaway, the tire will not be flat on the track while cornering.
The best way to read tire temperatures is to run 10 laps on a particular setup. Read the temps and don't expect to learn everything reading the temps only once. It will take a number of these sessions to sort everything out that is going on with the tires. Make sure you are not locking up the brakes or making any sudden changes in your steering outputs. These will all create erroneous tire temperatures readings.
A tire with too much NEGATIVE camber will show an excessively higher temperature at the INSIDE edges. Lean the top of the tire out to the outside.
A tire with too much POSITIVE camber will show an excessively higher temperature at the OUTSIDE edges so lean the top of the tire in.
A tire that is OVER inflated will have a higher middle temperature than the inside & outside edges.
A tire that is UNDER inflated will have a lower middle temperature than the inside & outside edges.
A car with too much toe OUT will show higher temperatures on both INSIDE edges of the front tires.
A car with too much toe IN will show higher temperatures on both OUTSIDE edges of the front tires.
A RF tire that is HOTTER by more than 10 degrees over the RR indicates a tight PUSH (understeer) condition.
A RF tire that is COLDER by more than 10 degrees over the RR indicates a loose ( oversteer) condition.
A tire with the HIGHEST average temperature is the corner of the car that you should work on first.
A tire with the LOWEST average temperature is the corner of the car that you should work on second.
A RF & LR diagonal average that is the same or higher than the front & right side average indicates too much wedge.
A RF & LR diagonal average that is more than 10 degrees lower than the front average and right side average indicates not enough wedge.
Let’s look at a few examples.
RF
I----M----O
208--202--194
Indicates too much negative camber.
RF
I----M----O
194--202--208
Indicates too much positive camber.
RF
I----M----O
204--188--197
Indicates an under inflated tire.
RF
I----M----O
204--210--197
Indicates an over inflated tire.
RF
I----M----O
204--198--194
Indicates correct camber. Overall average temp is 198.6.
RR
I----M----O
227--225--223
Overall average temp. is 225.
If the RR & RF temp above came off the same car we have a very loose racecar. The RR is 26 degrees hotter than the RF. If this RR is also the hottest tire on the car, it indicates the RR is spinning and or sliding in the corners. We need to go to a weaker RR spring to keep more weight on this tire and prevent the wheel spin. This should cool this tire & tighten up the chassis.
Caution -Temperature Averaging works when you have a fast car and need to fine tune it. If your car is a log wagon and wallowing around like a whale cure the handling first.
Panhard bar
Do not forget- The mid point between the right and left side anchor points on both panhard bar and J bar is the Roll Center. This Rear RC can be offset many inches from the vehicle centerline.
When Panhard bar has chassis mount on frame right side the Rear roll center will DROP under body roll. Opposite if chassis mount on left side.
If you raise both mount points on the Panhard bar, you are raising the Rear RC. The rear roll center will still move downward in body roll as above stated.
Tuning with sway bar (ARB)
A quick review of the ARB - sometimes also called anti-sway bars or anti-roll bars. Their purpose in life is to try to keep the car's body from "rolling" in a left turn.
When you are inside the car, you know that your body gets pulled toward the outside of the turn. The right part of the car on the outside of the turn gets pushed down toward the road and the left side part of the car on the inside of the turn rises up. In other words, the body of the car "rolls" 10 or 20 or 30 degrees toward the outside of the turn.
Too much Roll is bad. It tends to put more weight on the outside tires and less weight on the inside tires, reducing traction. The proper amount of body roll will load the right front tire and assist in improving traction through the turn. Ideally, we would like the body of the car to remain flat through a turn so that the weight stays distributed evenly on all four tires.
ARB tries to keep the car's body flat by moving force from one side of the body to another. When you go into a turn, the front suspension member of the outside of the turn gets pushed upward. The arm of the ARB gets pushed upward, and this applies torsion to the middle section. The torsion moves the arm at the other end of the rod, and this causes the suspension on the other side of the car to compress. The car's body tends to stay flat in the turn.
If you have too much ARB, you tend to lose independence between the suspension members on both sides of the car. When one wheel hits a bump, the ARB transmits the bump to the other side of the car as well, which is not what you want. The ideal is to find a setting that reduces body roll but does not hurt the independence of the front or rear springs.
Tune by adjusting the ARB Arm length. Longer arm is softer spring rate while shorter Arm increases the spring rate in front.
See post 1419 on page 41 for driver tips
Track tuning
Two things any crew chief better have in the tool box , next to the Rolaids, are Stagger tape and a Tire Pyrometer. Preferably one with a memory that will permit you to take readings and will display three readings per tire.
Tire temperatures are the only real way to tell what is going on and it is empirical. Learn how to use the tire pyrometer and make a habit of doing it correctly. I have a nice techy one that tell you to stab the right front tire inside, middle and outside then move to the right rear tire. The cursor ques you where to take the readings. Insert the sensor needle 1/8 inch into the tire at a 45 degree angle and be consistent. You will be stabbing three places on the tire face. Inside edge ( not on the edge but an inch from the inside edge) the middle and the outside ( not the very outside..,an inch from the outside edge). When taking readings try to do it as soon as the driver comes off the track as these tires cool very quickly. Tune and test day is ideal as you can do it on the track if you are solo ones in that session. Then jack up the car and take tire stagger readings right front first. Record the tire growth and this will tell you about stagger.
The optimal tire temperatures should be in a range of 190 to 240 degrees. On a short track it is normal for the outside edge of the RF tire & the inside edge of the LF to be 5 to 10 degrees cooler. This is because of the way the tires travel down the straightaway. On a larger track with longer straights, this spread will be even further. On an oval, the RF tire will have more negative camber, thus resulting in the inside edge of the tire contacting the track more than the outside edge giving you the higher temperature. On the LF you will run with more positive camber, so just the opposite holds true. While cornering these temperatures should even out if you have the correct amounts of camber & or weight transfer. The more camber you run, the higher these spreads will be. On a small track were you spend a lot of time cornering, you'll find the spread not as high. This is because your spending more time cornering than on the straights, thus distributing the temperatures across the face of the tire more evenly. If you try to achieve even temps across the tire you may develop a push. This is telling you that you have too much positive camber. Although the tire may be flat on the track, on a straightaway, the tire will not be flat on the track while cornering.
The best way to read tire temperatures is to run 10 laps on a particular setup. Read the temps and don't expect to learn everything reading the temps only once. It will take a number of these sessions to sort everything out that is going on with the tires. Make sure you are not locking up the brakes or making any sudden changes in your steering outputs. These will all create erroneous tire temperatures readings.
A tire with too much NEGATIVE camber will show an excessively higher temperature at the INSIDE edges. Lean the top of the tire out to the outside.
A tire with too much POSITIVE camber will show an excessively higher temperature at the OUTSIDE edges so lean the top of the tire in.
A tire that is OVER inflated will have a higher middle temperature than the inside & outside edges.
A tire that is UNDER inflated will have a lower middle temperature than the inside & outside edges.
A car with too much toe OUT will show higher temperatures on both INSIDE edges of the front tires.
A car with too much toe IN will show higher temperatures on both OUTSIDE edges of the front tires.
A RF tire that is HOTTER by more than 10 degrees over the RR indicates a tight PUSH (understeer) condition.
A RF tire that is COLDER by more than 10 degrees over the RR indicates a loose ( oversteer) condition.
A tire with the HIGHEST average temperature is the corner of the car that you should work on first.
A tire with the LOWEST average temperature is the corner of the car that you should work on second.
A RF & LR diagonal average that is the same or higher than the front & right side average indicates too much wedge.
A RF & LR diagonal average that is more than 10 degrees lower than the front average and right side average indicates not enough wedge.
Let’s look at a few examples.
RF
I----M----O
208--202--194
Indicates too much negative camber.
RF
I----M----O
194--202--208
Indicates too much positive camber.
RF
I----M----O
204--188--197
Indicates an under inflated tire.
RF
I----M----O
204--210--197
Indicates an over inflated tire.
RF
I----M----O
204--198--194
Indicates correct camber. Overall average temp is 198.6.
RR
I----M----O
227--225--223
Overall average temp. is 225.
If the RR & RF temp above came off the same car we have a very loose racecar. The RR is 26 degrees hotter than the RF. If this RR is also the hottest tire on the car, it indicates the RR is spinning and or sliding in the corners. We need to go to a weaker RR spring to keep more weight on this tire and prevent the wheel spin. This should cool this tire & tighten up the chassis.
Caution -Temperature Averaging works when you have a fast car and need to fine tune it. If your car is a log wagon and wallowing around like a whale cure the handling first.
Panhard bar
Do not forget- The mid point between the right and left side anchor points on both panhard bar and J bar is the Roll Center. This Rear RC can be offset many inches from the vehicle centerline.
When Panhard bar has chassis mount on frame right side the Rear roll center will DROP under body roll. Opposite if chassis mount on left side.
If you raise both mount points on the Panhard bar, you are raising the Rear RC. The rear roll center will still move downward in body roll as above stated.
Tuning with sway bar (ARB)
A quick review of the ARB - sometimes also called anti-sway bars or anti-roll bars. Their purpose in life is to try to keep the car's body from "rolling" in a left turn.
When you are inside the car, you know that your body gets pulled toward the outside of the turn. The right part of the car on the outside of the turn gets pushed down toward the road and the left side part of the car on the inside of the turn rises up. In other words, the body of the car "rolls" 10 or 20 or 30 degrees toward the outside of the turn.
Too much Roll is bad. It tends to put more weight on the outside tires and less weight on the inside tires, reducing traction. The proper amount of body roll will load the right front tire and assist in improving traction through the turn. Ideally, we would like the body of the car to remain flat through a turn so that the weight stays distributed evenly on all four tires.
ARB tries to keep the car's body flat by moving force from one side of the body to another. When you go into a turn, the front suspension member of the outside of the turn gets pushed upward. The arm of the ARB gets pushed upward, and this applies torsion to the middle section. The torsion moves the arm at the other end of the rod, and this causes the suspension on the other side of the car to compress. The car's body tends to stay flat in the turn.
If you have too much ARB, you tend to lose independence between the suspension members on both sides of the car. When one wheel hits a bump, the ARB transmits the bump to the other side of the car as well, which is not what you want. The ideal is to find a setting that reduces body roll but does not hurt the independence of the front or rear springs.
Tune by adjusting the ARB Arm length. Longer arm is softer spring rate while shorter Arm increases the spring rate in front.
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