unadvanced suspension thread
Oct 1, 2006, 08:46 AM
#16
Ok, perhaps the thread should head towards fixing perceived suspension problems.
Last two lapping events I added a click of rear rebound. One click. About mid-corner on a 140' radius the rear stepped out. Came right back in with a little throttle modulation. Here is my problem, how do I know it was the one click and not my wanting another .7 of a second off lap time?
Next session I took the click back out.
Next event I had time to consider what had happened and concluded it was coolant on the track (from my car, long story) and put a click back in.
This time the rear stepped out on a 90' radius. Again, by this time I was ramping up my timing efforts.
At this point I added a click of front bump just to see what that would do. Unfortunately my turbo expired (see above long story).
Seems to me I had at least three courses of action. 1,- R rebound. 2, + F bump. 3, know I was trying to hard in a couple of corners.
2, adding front bump may have been the least likely. My thinking was, if the front was a bit looser the two would cancel each other.
Given this scatterbrained description anyone got suspension input?
Last two lapping events I added a click of rear rebound. One click. About mid-corner on a 140' radius the rear stepped out. Came right back in with a little throttle modulation. Here is my problem, how do I know it was the one click and not my wanting another .7 of a second off lap time?
Next session I took the click back out.
Next event I had time to consider what had happened and concluded it was coolant on the track (from my car, long story) and put a click back in.
This time the rear stepped out on a 90' radius. Again, by this time I was ramping up my timing efforts.
At this point I added a click of front bump just to see what that would do. Unfortunately my turbo expired (see above long story).
Seems to me I had at least three courses of action. 1,- R rebound. 2, + F bump. 3, know I was trying to hard in a couple of corners.
2, adding front bump may have been the least likely. My thinking was, if the front was a bit looser the two would cancel each other.
Given this scatterbrained description anyone got suspension input?
Oct 1, 2006, 11:06 AM
#17
IMO, if the car is loose at mid corner and corner exit (can't tell by your description of the second situation), then in theory, with a well-designed damper, decreasing front compression and decreasing rear rebound would tighten things up (allows load to shift to the front tires).
If you're not very consistent at that particular track, then it becomes too difficult to say. If you are somewhat sure that you were taking the same line, turning in at the same point, same tire pressures etc etc, then you can say with some degree of certainty that the changes were due to the changes in damping
If you're not very consistent at that particular track, then it becomes too difficult to say. If you are somewhat sure that you were taking the same line, turning in at the same point, same tire pressures etc etc, then you can say with some degree of certainty that the changes were due to the changes in damping
Jan 4, 2007, 01:46 PM
#19
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Suspension tunning is a black art. Read as much as you can from suspension books like the one from Skip Barber.
Tire temps... First you need to make sure you are consistant and not abusing the tire. Understeering and oversteering will give you false readings for alignment tunning. Tire temps should always have 10-20 degrees warmer on the inside of the tire than the middle, middle and outside should be close (within 10 degrees of eachother). The reason behind this is because of negative camber. Your car spends most of its time going straight, then under braking, major load/heat is transfered into the tire (inertia into heat). Because of the negative camber more will build on the inside.
Your example earlier was "Such as 198, 195, 192" (inside to outside). This is even and not bad, very close. But I would say this tire could use more negative camber. This will give you more grip in the corner.
Shocks.
Shocks are your last adjustment. The last couple tenths. An art to learn to feel. This could turn into pages just on shocks. Try to simply visualize what weight transfer you are trying to either slow down or speed up. A quick way to feel this is to drive the car as it is for a couple laps. Pull in and go full soft in front and try again. Then full stiff. Then set back to where it was and do the same for the rear. BUT YOU MUST BE CONSISTANT ON THE TRACK. Not trying to yell, but cant stress that enough.
Your car did not spin out due to adding a click of rebound. This would actually slow down weight transfer to the front therfore being less prone to oversteer. What it sounds to me is you maybe braking too late and too hard while attempting to "brake turn." Keeping your foot on the brake is to keep the weight transfer on the nose, helping turn in.
The number #1 way to getting faster is being smooth. If your not smooth you cant tune the suspension. If you stomp on the brake pedal at the last second, you will transfer more weight in the first moment and the spring will try to bounce it back. As you go into the corner unsettled you scrub a ton of speed. God theres so much Id like to say..... Be smooth, make sure the car takes a set, then turn in, takes a set, then add gas. Your speed will increase every lap, and you will notice it is a lot easier and comfortable while you are going seconds faster.
Remember, the earlier you can get on the gas the faster youll be at the end of the straight. And I mean 10%, 20% throttle (any is more than 0%, you're still accelerating). Remember the throttle and brake are not a toggle switch. This is where lap times are found. The longer you make your straights the faster your time will be. The earlier you get the car settled under braking the earlier you can turn in and get on the apex, the earlier yousee its on its way to the apex, the earlier you can start to squeeze on the gas.
As PD Cunningham once told me. "Break early, break early, break early." Which then leads to "slow in, fast out."
Thats enough for now
, I could go on and on. Ask questions, Ill try to answer.
Tire temps... First you need to make sure you are consistant and not abusing the tire. Understeering and oversteering will give you false readings for alignment tunning. Tire temps should always have 10-20 degrees warmer on the inside of the tire than the middle, middle and outside should be close (within 10 degrees of eachother). The reason behind this is because of negative camber. Your car spends most of its time going straight, then under braking, major load/heat is transfered into the tire (inertia into heat). Because of the negative camber more will build on the inside.
Your example earlier was "Such as 198, 195, 192" (inside to outside). This is even and not bad, very close. But I would say this tire could use more negative camber. This will give you more grip in the corner.
Shocks.
Shocks are your last adjustment. The last couple tenths. An art to learn to feel. This could turn into pages just on shocks. Try to simply visualize what weight transfer you are trying to either slow down or speed up. A quick way to feel this is to drive the car as it is for a couple laps. Pull in and go full soft in front and try again. Then full stiff. Then set back to where it was and do the same for the rear. BUT YOU MUST BE CONSISTANT ON THE TRACK. Not trying to yell, but cant stress that enough.
Your car did not spin out due to adding a click of rebound. This would actually slow down weight transfer to the front therfore being less prone to oversteer. What it sounds to me is you maybe braking too late and too hard while attempting to "brake turn." Keeping your foot on the brake is to keep the weight transfer on the nose, helping turn in.
The number #1 way to getting faster is being smooth. If your not smooth you cant tune the suspension. If you stomp on the brake pedal at the last second, you will transfer more weight in the first moment and the spring will try to bounce it back. As you go into the corner unsettled you scrub a ton of speed. God theres so much Id like to say..... Be smooth, make sure the car takes a set, then turn in, takes a set, then add gas. Your speed will increase every lap, and you will notice it is a lot easier and comfortable while you are going seconds faster.
Remember, the earlier you can get on the gas the faster youll be at the end of the straight. And I mean 10%, 20% throttle (any is more than 0%, you're still accelerating). Remember the throttle and brake are not a toggle switch. This is where lap times are found. The longer you make your straights the faster your time will be. The earlier you get the car settled under braking the earlier you can turn in and get on the apex, the earlier yousee its on its way to the apex, the earlier you can start to squeeze on the gas.
As PD Cunningham once told me. "Break early, break early, break early." Which then leads to "slow in, fast out."
Thats enough for now
, I could go on and on. Ask questions, Ill try to answer.
Jan 4, 2007, 04:58 PM
#20
First off, thank you very much for posting. It must be very easy for knowledgeable folks to not post because it can become so time consuming and uncomfortable when arguments arise.
Let me assure you, I try to be as smooth as possible. In my particular case I may have been trying to increase my speed in that corner by applying speed to early.
Just so happens I was just thinking about corner weighing.
If I have got it wrong please help out. The reason a car is corner weighted is two fold. 1, It can't be balanced completely evenly.
2, If you balance the weight side to side, then the car should approach even handling through the corners. Think of it this way, if you hoisted the car up and balanced the car on a pin point, a corner balanced car would balance down the center line somewhere around the e brake handle.(please nevermind the fact the wheels have to be on the ground for corner weighing to be real) This despite the fact that the left front wheel weighs much more than the right front wheel. Without corner balancing the left side of the car may weigh more than the right, and every time you take a right turn the right side tires aren't being asked to do enough work.
With the center of gravity in the middle of the car each side of the car approaches the same load as the other on opposite corners. So the car would behave about the same turning left or right.
If a tire isn't touching the pavement it can't help the other over worked tires.
You can only expect so much traction from a tire, ask for more and you lose some or most. If a side of wheels is up in the air the down side is doing all it can and is being asked for more. Keep those high wheels on the ground and they can help at least a bit. Really not talking about "in the air" tires but about tires that don't have the load on them they would if the CG were where it belonged.
Let me assure you, I try to be as smooth as possible. In my particular case I may have been trying to increase my speed in that corner by applying speed to early.
Just so happens I was just thinking about corner weighing.
If I have got it wrong please help out. The reason a car is corner weighted is two fold. 1, It can't be balanced completely evenly.
2, If you balance the weight side to side, then the car should approach even handling through the corners. Think of it this way, if you hoisted the car up and balanced the car on a pin point, a corner balanced car would balance down the center line somewhere around the e brake handle.(please nevermind the fact the wheels have to be on the ground for corner weighing to be real) This despite the fact that the left front wheel weighs much more than the right front wheel. Without corner balancing the left side of the car may weigh more than the right, and every time you take a right turn the right side tires aren't being asked to do enough work.
With the center of gravity in the middle of the car each side of the car approaches the same load as the other on opposite corners. So the car would behave about the same turning left or right.
If a tire isn't touching the pavement it can't help the other over worked tires.
You can only expect so much traction from a tire, ask for more and you lose some or most. If a side of wheels is up in the air the down side is doing all it can and is being asked for more. Keep those high wheels on the ground and they can help at least a bit. Really not talking about "in the air" tires but about tires that don't have the load on them they would if the CG were where it belonged.
Jan 5, 2007, 06:35 AM
#21
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Well, youre kinda on the right page, but its great you're trying visualize whats going on, rather than just remembering what someone told you.
Corner weights are far from equal on a regular street car, even in my race car. Left front corner is always the heaviest (driver etc) and right rear is the lightest. But the sum of those two (cross weights) should be equal to the sum of the right front and left rear. This is what makes it handle equally to left and right. Weight transfer will be more the same, car will turn the same left to right.
I love to help those who want to learn to go faster.
Corner weights are far from equal on a regular street car, even in my race car. Left front corner is always the heaviest (driver etc) and right rear is the lightest. But the sum of those two (cross weights) should be equal to the sum of the right front and left rear. This is what makes it handle equally to left and right. Weight transfer will be more the same, car will turn the same left to right.
I love to help those who want to learn to go faster.
Jan 5, 2007, 01:23 PM
#22
Great thread, Very informative. I have always felt that evo was more crisp or turns in faster on one side than the other (mostly autocross speed turns); would that behavior be cured with equal crossweight? I tried dialing an extra click to my single adjustable coilovers on the front of the softer side and the car felt more balanced from left to right . Was I in the right track or need to get the car cornerweighted ?
Jan 5, 2007, 09:28 PM
#23
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A shock is in control of the spring. It cushions or dampens the rate at which the spring compresses (bump/compression) and how fast it bounces back (rebound). So by adding a click to the front what you are doing is making it a little harder/stiffer for the weight to transfer on to that corner from the rear (for ex. less brake dive). Depending on how sensative your shocks are/how many clicks, you should try to keep them the same until the last tenth, maybe to setup for that last corner onto the straight for example.
Corner weights may be the issue, but so could caster being different on one side to the other.
The order to start a good alighnment/chassis setup.
First disconnect one sway bar endlink front and back. Then start with corner balancing, then camber/caster, toe, recheck camber, recheck toe if changes were made and so on till its perfect. Dont forget to start in race weight/trim (gas, spare tire etc). Then reconnect bars with no preload (this is where adjustable links come in) if you have stockers dont disconnect.
Corner weights may be the issue, but so could caster being different on one side to the other.
The order to start a good alighnment/chassis setup.
First disconnect one sway bar endlink front and back. Then start with corner balancing, then camber/caster, toe, recheck camber, recheck toe if changes were made and so on till its perfect. Dont forget to start in race weight/trim (gas, spare tire etc). Then reconnect bars with no preload (this is where adjustable links come in) if you have stockers dont disconnect.
