Suspension Tuning Tips (part 3)
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Suspension Tuning Tips (part 3)
How to adjust your suspension
The previous discussion involved basic concepts and principles of suspension design theory. These principles work pretty well for most driving styles (as well as most of the good drivers that I have worked with) and preferences. Your preference could be different. To find the optimal settings for your personnel suspension set-up there are a few tricks that you can do to make the process less painful and quicker.
To adjust your suspension you need a just a few simple things.
<u>First you need a good, accurate tire pressure gauge. </u>A gauge with a bleeder valve is very useful. Gauges like this can be purchased at just about any racers supply house for about 20 bucks. Don’t waste your money on those expensive electronic gauges. Those are slow to use and never come with bleeder valves.
The next bit of stuff to have is a <u>compressed air tank </u>for adjusting tire pressures. Tracks almost never have a handy air tank. I got my tank from Sears for about 50 bucks. Fill it at a gas station or use your home air compressor before heading out. Make sure the tank you buy has a safety relief valve so you don’t blow the crap out of your self if you leave the tank in your hot car during lunch or something.
A <u>digital tire pyrometer</u> is very important. Get one with a wire bead probe. These are used for measuring tire temperature differentials across the tread which is a good tool for judging whether your tires pressures and alignment settings are right. You can get one of these at any racers supply house for 50 to 200 bucks. If you don’t want to shell out the bucks for this, bring a bottle of white out with you.
A notepad and pen are critical also. With so many adjustment parameters it is important to try to write everything down as you will never remember it all.
When at the track, first note your initial settings including the air pressure. Write it all down. Paint a stripe of white out on your tire’s sidewalls going down to the tread. It helps if you have someone do all these things for you as it gets pretty hectic when you are trying to get ready to run. Go out and drive the car, making mental notes on how it handles, what you like and what you dislike. When you pit or when your run is over, immediately measure your tire temperatures. You only have a few seconds to do this as the temperatures drop quickly. If the course is clockwise, measure the left side of the car first starting with the left front. If it is counterclockwise, measure the right side first starting on the right front. You want to measure the treads temperature in three places, the outside, the middle and the inside. Push the wire of the bead probe slightly into the rubber for the most accurate measurement. Measure all the tires quickly and be sure to write it all down. Next measure and record the tires pressure quickly before the tires have a chance to cool much. Look at the white out stripe that you made. It is there to indicate if your tires are rolling onto the sidewalls. The stripe should not be worn past the rounded corner of the tread- sidewall junction.
Now review your notes and the recorded data. How did you like the way the car handled? Did it push? Was it loose? Was it perfect? Look at your temperature distributions across the tread. Ideally it should be about 10 degrees hotter on the inside than the outside with an even gradient across the tread. *This is usually only attainable on a race car with optimized suspension geometry.* On a street, production based car that is totally modified for adjustably, even temperatures across the tread may be possible and on a FWD car usually the outside will always be a bit higher. On a stock car you cannot usually get better than a 20 degree gradient. Anyway, the camber and pressures might need some adjustment to get an optimal temperature gradients out of the tires. If the temps are fairly even, it means you are using the whole tread of the tire to it’s fullest. You also want to get the average temps on the front and rear tires the same. That is not possible with a FWD production based car. A spread of 30-40 degrees is about the best that can be expected with the front tires running hotter than the rears.
<u>Modern R compound tires work the best at temperatures above 180-190 degrees.</u> At temperatures much above 220 degrees, most tires will start to chunk. To know the exact temp that your tire works best, call your tire manufactures tech line for advice. Watch for chunking on the outside edge of the tire, where it is most likely to be a problem with a FWD car. Like I said, play with your air pressures and camber to get the temps right and an even distribution to avoid chunking. Raising the tire pressure will reduce flexing and the tire will run cooler, lowering it will cause the tire to run hotter. Raising the pressure will cause the inside of the tread to run hotter and the edges cooler, lowering will make the outside edges hotter and the inside cooler.
Once you are using all of your tires tread properly, you can play with the balance. Look at the previously displayed chart to see all of the variables. Usually you want to play with swaybar and spring rates to balance the car. Toe settings are useful to get the car to turn in and rotate. Keep on monitoring the tire temps and pressures and note how changes affect the car. (BE SURE TO WRITE ALL CHANGES DOWN AND MAKE ONLY ONE CHANGE AT A TIME) In a few sessions you will be able to have a good grip on how to set your car up (bad pun).
On a stock car, about the only variables you can play with are tire pressures and toe. Adjust your pressures so the temp gradient is as even as possible across the tread. Since your adjustably is limited this will not be possible. Do not add so much pressure that the outside and middle of the tire are at the same temperature. At this point the tire is crowning with a bulge in the middle. This is not using the tire well. Tire pressures can be used to tune the balance. Try 2 psi increments as most good drivers can feel a difference in that. Remember to only adjust one thing at a time! Toe adjustments are very useful on the stock car also. A little front toe-out can help reduce push and get the car to turn in and set quicker. A little rear toe out can get the rear of a pushing car to rotate in tight turns.
If you don’t have a pyrometer, then use the white out sidewall stripe method to determine if the tire is rolling over excessively. If you adjust the tire pressure so it is only rolling just to the end of the rounded tread to sidewall juncture, then you are very close to the proper set up. Don’t be afraid of adding to much air as I have run up to 55 psi hot on the front tires of heavily understeering Showroom Stock cars with no ill side effects. In fact this is probably safer than allowing the tire to overheat and chunk. Just having the ability to play with the tire pressures at the track can give you a good edge over the typical slalom weekend warrior, at least in the beginners type classes. As you get better, you will have to master the art of suspension setup to remain competitive.
<u>Don’t be afraid to ask fast guys for help and advice but take it with a grain of salt. </u>Most of these people are helpful and friendly but every once and a while one of them will see you as a potential threat and will feed you misinformation so you will mess your set up all to hell. If someone’s advice seems the exact opposite of what I outlined here, be extra careful as this person could be snowing you.
My outline here is not the last word in suspension tuning. It is just meant to help explain things and to be a guide*** The final element is you***. You need to be able to make the car do what you want it to do. Don’t be afraid to experiment as long as it is under safe and controlled circumstances. Please experiment to get an idea what different settings do. Set your car wrong and know how that feels. Write everything down. Compare notes. Soon you will become a tweek master! Hopefully these hints will give you the winning edge and help guide your learning process.
And lastly - keep it off the streets - join an autocross club or driving school.
Peace
BPR
The previous discussion involved basic concepts and principles of suspension design theory. These principles work pretty well for most driving styles (as well as most of the good drivers that I have worked with) and preferences. Your preference could be different. To find the optimal settings for your personnel suspension set-up there are a few tricks that you can do to make the process less painful and quicker.
To adjust your suspension you need a just a few simple things.
<u>First you need a good, accurate tire pressure gauge. </u>A gauge with a bleeder valve is very useful. Gauges like this can be purchased at just about any racers supply house for about 20 bucks. Don’t waste your money on those expensive electronic gauges. Those are slow to use and never come with bleeder valves.
The next bit of stuff to have is a <u>compressed air tank </u>for adjusting tire pressures. Tracks almost never have a handy air tank. I got my tank from Sears for about 50 bucks. Fill it at a gas station or use your home air compressor before heading out. Make sure the tank you buy has a safety relief valve so you don’t blow the crap out of your self if you leave the tank in your hot car during lunch or something.
A <u>digital tire pyrometer</u> is very important. Get one with a wire bead probe. These are used for measuring tire temperature differentials across the tread which is a good tool for judging whether your tires pressures and alignment settings are right. You can get one of these at any racers supply house for 50 to 200 bucks. If you don’t want to shell out the bucks for this, bring a bottle of white out with you.
A notepad and pen are critical also. With so many adjustment parameters it is important to try to write everything down as you will never remember it all.
When at the track, first note your initial settings including the air pressure. Write it all down. Paint a stripe of white out on your tire’s sidewalls going down to the tread. It helps if you have someone do all these things for you as it gets pretty hectic when you are trying to get ready to run. Go out and drive the car, making mental notes on how it handles, what you like and what you dislike. When you pit or when your run is over, immediately measure your tire temperatures. You only have a few seconds to do this as the temperatures drop quickly. If the course is clockwise, measure the left side of the car first starting with the left front. If it is counterclockwise, measure the right side first starting on the right front. You want to measure the treads temperature in three places, the outside, the middle and the inside. Push the wire of the bead probe slightly into the rubber for the most accurate measurement. Measure all the tires quickly and be sure to write it all down. Next measure and record the tires pressure quickly before the tires have a chance to cool much. Look at the white out stripe that you made. It is there to indicate if your tires are rolling onto the sidewalls. The stripe should not be worn past the rounded corner of the tread- sidewall junction.
Now review your notes and the recorded data. How did you like the way the car handled? Did it push? Was it loose? Was it perfect? Look at your temperature distributions across the tread. Ideally it should be about 10 degrees hotter on the inside than the outside with an even gradient across the tread. *This is usually only attainable on a race car with optimized suspension geometry.* On a street, production based car that is totally modified for adjustably, even temperatures across the tread may be possible and on a FWD car usually the outside will always be a bit higher. On a stock car you cannot usually get better than a 20 degree gradient. Anyway, the camber and pressures might need some adjustment to get an optimal temperature gradients out of the tires. If the temps are fairly even, it means you are using the whole tread of the tire to it’s fullest. You also want to get the average temps on the front and rear tires the same. That is not possible with a FWD production based car. A spread of 30-40 degrees is about the best that can be expected with the front tires running hotter than the rears.
<u>Modern R compound tires work the best at temperatures above 180-190 degrees.</u> At temperatures much above 220 degrees, most tires will start to chunk. To know the exact temp that your tire works best, call your tire manufactures tech line for advice. Watch for chunking on the outside edge of the tire, where it is most likely to be a problem with a FWD car. Like I said, play with your air pressures and camber to get the temps right and an even distribution to avoid chunking. Raising the tire pressure will reduce flexing and the tire will run cooler, lowering it will cause the tire to run hotter. Raising the pressure will cause the inside of the tread to run hotter and the edges cooler, lowering will make the outside edges hotter and the inside cooler.
Once you are using all of your tires tread properly, you can play with the balance. Look at the previously displayed chart to see all of the variables. Usually you want to play with swaybar and spring rates to balance the car. Toe settings are useful to get the car to turn in and rotate. Keep on monitoring the tire temps and pressures and note how changes affect the car. (BE SURE TO WRITE ALL CHANGES DOWN AND MAKE ONLY ONE CHANGE AT A TIME) In a few sessions you will be able to have a good grip on how to set your car up (bad pun).
On a stock car, about the only variables you can play with are tire pressures and toe. Adjust your pressures so the temp gradient is as even as possible across the tread. Since your adjustably is limited this will not be possible. Do not add so much pressure that the outside and middle of the tire are at the same temperature. At this point the tire is crowning with a bulge in the middle. This is not using the tire well. Tire pressures can be used to tune the balance. Try 2 psi increments as most good drivers can feel a difference in that. Remember to only adjust one thing at a time! Toe adjustments are very useful on the stock car also. A little front toe-out can help reduce push and get the car to turn in and set quicker. A little rear toe out can get the rear of a pushing car to rotate in tight turns.
If you don’t have a pyrometer, then use the white out sidewall stripe method to determine if the tire is rolling over excessively. If you adjust the tire pressure so it is only rolling just to the end of the rounded tread to sidewall juncture, then you are very close to the proper set up. Don’t be afraid of adding to much air as I have run up to 55 psi hot on the front tires of heavily understeering Showroom Stock cars with no ill side effects. In fact this is probably safer than allowing the tire to overheat and chunk. Just having the ability to play with the tire pressures at the track can give you a good edge over the typical slalom weekend warrior, at least in the beginners type classes. As you get better, you will have to master the art of suspension setup to remain competitive.
<u>Don’t be afraid to ask fast guys for help and advice but take it with a grain of salt. </u>Most of these people are helpful and friendly but every once and a while one of them will see you as a potential threat and will feed you misinformation so you will mess your set up all to hell. If someone’s advice seems the exact opposite of what I outlined here, be extra careful as this person could be snowing you.
My outline here is not the last word in suspension tuning. It is just meant to help explain things and to be a guide*** The final element is you***. You need to be able to make the car do what you want it to do. Don’t be afraid to experiment as long as it is under safe and controlled circumstances. Please experiment to get an idea what different settings do. Set your car wrong and know how that feels. Write everything down. Compare notes. Soon you will become a tweek master! Hopefully these hints will give you the winning edge and help guide your learning process.
And lastly - keep it off the streets - join an autocross club or driving school.
Peace
BPR
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