Recommended Ride Height?
09-09-12, 10:02 PM
#26
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Fun huh!?
I wouldn't set the rear lower than the front, no need to be that low on the street. The difference in weight front to rear is nill. You're effecting the location of the center of gravity to move weight front to rear. How much does your gear shift **** move back or forward when you raise and lower the car? That is about the location of your CG.
Without your weight in the car you are wasting your time. Unless your car goes out by itself for fun, lol.
The biggest thing to look at up front is that your ball joints are lower than the center of the suspension bolts. Small changes in that relation will change how effective the front bar is. Lower the car,roll center drops more than you lowered the car, bar becomes less effective, car falls over in a turn. It's all about roll center height. I'll throw you another issue. The roll center moves sideways too, especially with a strut car. As the car leans the roll center heads toward the inside of the turn, making the car want to lean MORE. Think about grabbing a sledgehammer by the end of the handle, hold it up vertical and wave it back and forth. Pretty tough. Now, grab it right under the hammer head, a lot easier to wave it back and forth, right? Your hand is like your roll center on your car.
Your sluggish steering feel may be alignment based. Castor, camber and toe. Make sure you have that stuff right too.
What spring rates do you have? The shocks just need to control the spring in rebound and the unsprung weight in bump. Loosen them up to 2 or 3 all the way around if you have street type springs. Drive the car see if it bouncey. You can tune how the car feels in the transitions(entering or exiting a turn) In the middle of the turn they are just along for the ride unless you hit a bump. Try going to 5 on the rear, you'll find the car will turn in a little better but may skitter on bumps on turn exit when you are putting the power down.
I wouldn't set the rear lower than the front, no need to be that low on the street. The difference in weight front to rear is nill. You're effecting the location of the center of gravity to move weight front to rear. How much does your gear shift **** move back or forward when you raise and lower the car? That is about the location of your CG.
Without your weight in the car you are wasting your time. Unless your car goes out by itself for fun, lol.
The biggest thing to look at up front is that your ball joints are lower than the center of the suspension bolts. Small changes in that relation will change how effective the front bar is. Lower the car,roll center drops more than you lowered the car, bar becomes less effective, car falls over in a turn. It's all about roll center height. I'll throw you another issue. The roll center moves sideways too, especially with a strut car. As the car leans the roll center heads toward the inside of the turn, making the car want to lean MORE. Think about grabbing a sledgehammer by the end of the handle, hold it up vertical and wave it back and forth. Pretty tough. Now, grab it right under the hammer head, a lot easier to wave it back and forth, right? Your hand is like your roll center on your car.
Your sluggish steering feel may be alignment based. Castor, camber and toe. Make sure you have that stuff right too.
What spring rates do you have? The shocks just need to control the spring in rebound and the unsprung weight in bump. Loosen them up to 2 or 3 all the way around if you have street type springs. Drive the car see if it bouncey. You can tune how the car feels in the transitions(entering or exiting a turn) In the middle of the turn they are just along for the ride unless you hit a bump. Try going to 5 on the rear, you'll find the car will turn in a little better but may skitter on bumps on turn exit when you are putting the power down.
09-10-12, 10:34 AM
#27
I'd go ride height, alignment, corner weight. It will be difficult to get the weights perfect without moving stuff in the car.
When I build a car I put steel tubes in place of the shocks so any weight goes right to the wheels(tire pressures matter too!) I do a rough mock up of where things will go with the car on scales. Anything that can be moved is placed in the best spot to have my actual weights where I want them. When the car gets the springs and shocks there isn't much twisting of spring perches and jacking the suspension to get it to carry the weight the way I want.
Your spring rates are pretty low actually, should be a nice street package. You won't need to get into the 4 or 5 range to damp the spring but you can use those settings to affect handling in transitions. I've tested those shocks on my shock dyno so that isn't just a guess.
When I build a car I put steel tubes in place of the shocks so any weight goes right to the wheels(tire pressures matter too!) I do a rough mock up of where things will go with the car on scales. Anything that can be moved is placed in the best spot to have my actual weights where I want them. When the car gets the springs and shocks there isn't much twisting of spring perches and jacking the suspension to get it to carry the weight the way I want.
Your spring rates are pretty low actually, should be a nice street package. You won't need to get into the 4 or 5 range to damp the spring but you can use those settings to affect handling in transitions. I've tested those shocks on my shock dyno so that isn't just a guess.
09-10-12, 11:02 AM
#28
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I'd go ride height, alignment, corner weight. It will be difficult to get the weights perfect without moving stuff in the car.
When I build a car I put steel tubes in place of the shocks so any weight goes right to the wheels(tire pressures matter too!) I do a rough mock up of where things will go with the car on scales. Anything that can be moved is placed in the best spot to have my actual weights where I want them. When the car gets the springs and shocks there isn't much twisting of spring perches and jacking the suspension to get it to carry the weight the way I want.
Your spring rates are pretty low actually, should be a nice street package. You won't need to get into the 4 or 5 range to damp the spring but you can use those settings to affect handling in transitions. I've tested those shocks on my shock dyno so that isn't just a guess.
When I build a car I put steel tubes in place of the shocks so any weight goes right to the wheels(tire pressures matter too!) I do a rough mock up of where things will go with the car on scales. Anything that can be moved is placed in the best spot to have my actual weights where I want them. When the car gets the springs and shocks there isn't much twisting of spring perches and jacking the suspension to get it to carry the weight the way I want.
Your spring rates are pretty low actually, should be a nice street package. You won't need to get into the 4 or 5 range to damp the spring but you can use those settings to affect handling in transitions. I've tested those shocks on my shock dyno so that isn't just a guess.
i'm running 350/175 springs and the illuminas are on 3 and it seems to be really good everywhere. on my car i was looking at the #7 GTU car, and my right height is by eyeball, the same, so its at the bottom end of the stock spec, maybe a teeny bit high in the front. zero toe, -2 camber.
it drives really nice, it feels quick and light, and actually ends up with understeer
09-10-12, 01:31 PM
#29
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Allright, as I suspected I need to complete my height adjustments first. Is there a better, more reproducible way to measure? Perhaps for someone with a lesser attention to detail as myself and poorer vision whilst I'm in the car? Some of my fenders are a little bunged up, esp. were the inner lip wraps around to the outside(right where I am trying to measure). Also, how to accurately measure the height bias between the two ends of the control arm? I have no way of: getting the car high enough to get under it, level, and it's weight on the wheels... Thanks again, guys.
09-10-12, 03:20 PM
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depending how crazy/**** you want to get the tolerance is something like 1/8-1/4" measured from the fender, so if the left is 25.25" and the right is 25.125" that's fine.
also the 5/8" number is kind of the same, you don't wanna go lower than that, but you can be higher! the 5/8" thing is hard to measure, you could try ramps, blocks of wood, or put the jackstands on the control arms etc etc.
also the 5/8" number is kind of the same, you don't wanna go lower than that, but you can be higher! the 5/8" thing is hard to measure, you could try ramps, blocks of wood, or put the jackstands on the control arms etc etc.
09-10-12, 03:32 PM
#31
Since this a car being set up to win the SCCA Runoffs getting measurements within a 1/4" should be fine. I've seen old Indycar set up sheets that stuff was measured to the thousandth.
As for the measuring spots. Find spots that are the same on both sides that aren't dented from off road excursions or jacking up the car. Pick spots and always use the same spot for your set up changes. You may find the body isn't exact side to side compared to the floor pan/chassis so your wheel arches may have different gaps. I once made an L shaped stick I could slide under the car that had a ruler attached to the short side of the L. It gave me a way to measure a spot I couldn't reach with my fat arm. It was a great use of all the extra tape of a broken tape measure. I have small sections cut up all over my shop.
In the front of an FB I use the frame rail that holds the subframe, the rear I use the reinforced area the lower control arm mounts to.
As for the measuring spots. Find spots that are the same on both sides that aren't dented from off road excursions or jacking up the car. Pick spots and always use the same spot for your set up changes. You may find the body isn't exact side to side compared to the floor pan/chassis so your wheel arches may have different gaps. I once made an L shaped stick I could slide under the car that had a ruler attached to the short side of the L. It gave me a way to measure a spot I couldn't reach with my fat arm. It was a great use of all the extra tape of a broken tape measure. I have small sections cut up all over my shop.
In the front of an FB I use the frame rail that holds the subframe, the rear I use the reinforced area the lower control arm mounts to.
09-11-12, 08:05 PM
#32
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The little things...
Allright guys, I'm constantly thinking about this all week until I can get back to my car this weekend...Any tips for the best/quickest/most convenient way to get the car in the air at each end, get the wheels unsprung, make adjustments, get car back on the ground, make measurements, repeat, etc. All I gots is some jack stands, one 2ton floor jack, and one two car garage with a floor suspect as far as levelness...AND, is it okay to continually jack the entire rear off the ground under the diff. when the shocks completely compress, then take the weight of the whole rear as the wheels come off the ground? I have to do this, then stack wooden blocks up under the frame rail, then let down the rear to get the rear wheels unsprung...
09-12-12, 03:24 AM
#33
I just use the trolley jack under the crossmember to lift the front, and under the pumkin at the rear, take all of 10 seconds haha.
I dont really trust my floor either so i just made sure the actual spring perches measure the same. Ill let the wheel alignment guy fine tune that on the scales.
A small spirit level might be a good way to get the cntrl arm bolt higher than the ball joint 5/8" , i just eyeballed mine (after reading about it here from jgrewe) and its about right, but might go up another 5mm just for peace of mind.
Jgrewe, is there any rule of thumb for rear ride height with the standard watts link assembly in place? Im led to believe there can be roll center and binding issues?
I dont really trust my floor either so i just made sure the actual spring perches measure the same. Ill let the wheel alignment guy fine tune that on the scales.
A small spirit level might be a good way to get the cntrl arm bolt higher than the ball joint 5/8" , i just eyeballed mine (after reading about it here from jgrewe) and its about right, but might go up another 5mm just for peace of mind.
Jgrewe, is there any rule of thumb for rear ride height with the standard watts link assembly in place? Im led to believe there can be roll center and binding issues?
09-12-12, 09:02 AM
#34
The bind comes from the upper arms pointing 'in' in the front and how short they are. The rear will move up and down fine, top rolling forward a bit as it goes up because of the shorter upper links. As soon as you try to introduce any kind of lean the upper links start to bind and become like an anti-roll bar. The more lean, the more bind in the bushings. This is more evident if the car is lowered to start. There are also roll steer issues in the rear but that is 10/10ths stuff too.
The Watts link works great through most of its travel range. The only real problem is the roll center height that leads to a roll axis that has quite a bit of slope forward. If you can't redesign some of the stuff in the rear you just need to play with spring rates and anti-roll bars.
The binding and roll center height issues lead to needing soft springs in the rear if nothing is done to fix the problems. That is why you see HUGE front bars and stiff springs on the front of these cars and no bar and soft springs on the rear. Kind of like putting your left foot in a bucket so you can run straight because your right foot is in a bucket.
The Watts link works great through most of its travel range. The only real problem is the roll center height that leads to a roll axis that has quite a bit of slope forward. If you can't redesign some of the stuff in the rear you just need to play with spring rates and anti-roll bars.
The binding and roll center height issues lead to needing soft springs in the rear if nothing is done to fix the problems. That is why you see HUGE front bars and stiff springs on the front of these cars and no bar and soft springs on the rear. Kind of like putting your left foot in a bucket so you can run straight because your right foot is in a bucket.
09-12-12, 12:13 PM
#35
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With the combination of 150 Lb springs in the rear, the swaybar, the ride height, and the short bodied Bilsteins, the ride is extremely firm. The springs actually pull the shocks out to their limit on droop, leaving me with about 1.5" of available travel. Hard to explain, but I have to jack up the rear end, compressing the spring, in order to get the shock bolt in. Probably not the ideal setup, but it works great for me so I'm not going to look a gift horse in the mouth.
.
09-12-12, 12:33 PM
#36
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150lbs springs are really soft, the AE86 corolla people run 300-350lbs rear springs, and the car has a similar rear suspension, and if anything is lighter.
09-12-12, 02:19 PM
#37
There are a lot of ways to make the cars handle very well. For it to work well in different conditions it needs to actually 'work'. Kentetsu, I've seen your results thread, either your car works for what you do with it or you are an awesome driver (maybe a little of both!). Your system is using the rear bushings to help the anti-roll bar but you may be squating more than is ideal on corner exit with the power down. Try that on a bumpy course and you may end up short on bump travel and long on oversteer,lol.
Something to think about with these cars; if the car has almost perfect front to rear balance and the big difference is the unsprung weight of the rear end, why do you need spring rates in the rear that give you such a huge difference in wheel rate? Something isn't working as well as it could. Most times its rules that keep the problems from being solved.
Something to think about with these cars; if the car has almost perfect front to rear balance and the big difference is the unsprung weight of the rear end, why do you need spring rates in the rear that give you such a huge difference in wheel rate? Something isn't working as well as it could. Most times its rules that keep the problems from being solved.
09-15-12, 11:18 PM
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update
I got my car's height set today. Front ended up being ~23" at the wheel arch in the front (with me in it) and ~23 1/2" in the rear. It had under half tank. Is this sufficiently higher enough in the rear? I hope so, don't want to have to go through that again...Also, how do you "lock" the rear spring perches from moving over time?
Finally going for alignment hopefully this week. What do I want for a street car, and how do/when do I finally torque/tighten the rear tension rod nuts?
Finally going for alignment hopefully this week. What do I want for a street car, and how do/when do I finally torque/tighten the rear tension rod nuts?
09-16-12, 01:09 AM
#39
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The front collars have locks on them because they turn, and could therefore "adjust themselves". Since the rears don't turn, this isn't an issue. 
09-16-12, 01:13 AM
#40
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Here's a video from last year of a very rough course when I was racing with the Porsche Club. The surface was so bumpy that my eyeballs were rattling around in my skull causing blurred vision. By the third run, I think they had swollen up a bit to reduce the rattling and blurring. (no, I'm not kidding. l0l)
.
09-16-12, 01:27 AM
#41
I got my car's height set today. Front ended up being ~23" at the wheel arch in the front (with me in it) and ~23 1/2" in the rear. It had under half tank. Is this sufficiently higher enough in the rear? I hope so, don't want to have to go through that again...Also, how do you "lock" the rear spring perches from moving over time?
Finally going for alignment hopefully this week. What do I want for a street car, and how do/when do I finally torque/tighten the rear tension rod nuts?
Finally going for alignment hopefully this week. What do I want for a street car, and how do/when do I finally torque/tighten the rear tension rod nuts?
09-16-12, 12:24 PM
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09-18-12, 06:34 PM
#43
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alignment
Going for alignment Thursday morning. Found this pic from an older thread, is this what I want to shoot for? Maybe only -1* of camber, though?
09-19-12, 07:47 PM
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camber, caster, toe=?
I got an appointment in 12 hrs...I need guidance! What exactly do I need to try to convince the alignment technician to set my:camber, caster, toe to?
09-19-12, 08:21 PM
#45
Where to start...
Camber, depends on what the tire likes, which we don't know yet. 1.5 to 2 degrees should work to start but it depends on how much your car leans.
Caster, try to stay near stock specs to start because caster works best in certain relations to kingpin inclination and you have no way of changing KPI. With a ton of caster you can get some camber gain when turning but the downside is you are actually lifting the outside tire in relation to the chassis the more you turn the wheel.
Toe, this is where you have to think about your trade off. Street driving or auto-x? Auto-x you probably want some toe out maybe 1/8" or as much as a 1/4" if there are no straight sections. The car will hunt for curbs on the street but it will turn in awesome. On the street stay stock. Toe can be a quick adjustment once you have a baseline. Make sure the steering arms are centered and both outer arms are the same length.
What I would do is see how much toe is gained or lost with each turn of the adjuster and write it down in your car notes(oh yea, start a notebook of your set ups and keep track of everything you ever change, weather conditions, course surface, planet alignments etc etc)
Once you have a baseline you can start playing with stuff with string alignments and maybe buy a cheap camber gauge. A proper alignment for the course will make a world of difference and you can go back and forth from street to auto-x settings and under 15 minutes.
Camber, depends on what the tire likes, which we don't know yet. 1.5 to 2 degrees should work to start but it depends on how much your car leans.
Caster, try to stay near stock specs to start because caster works best in certain relations to kingpin inclination and you have no way of changing KPI. With a ton of caster you can get some camber gain when turning but the downside is you are actually lifting the outside tire in relation to the chassis the more you turn the wheel.
Toe, this is where you have to think about your trade off. Street driving or auto-x? Auto-x you probably want some toe out maybe 1/8" or as much as a 1/4" if there are no straight sections. The car will hunt for curbs on the street but it will turn in awesome. On the street stay stock. Toe can be a quick adjustment once you have a baseline. Make sure the steering arms are centered and both outer arms are the same length.
What I would do is see how much toe is gained or lost with each turn of the adjuster and write it down in your car notes(oh yea, start a notebook of your set ups and keep track of everything you ever change, weather conditions, course surface, planet alignments etc etc)
Once you have a baseline you can start playing with stuff with string alignments and maybe buy a cheap camber gauge. A proper alignment for the course will make a world of difference and you can go back and forth from street to auto-x settings and under 15 minutes.
09-20-12, 07:37 AM
#47
Alignment guy should have access to stock specs. I've never done anything with a focus on street driving, my RX's are all track cars.
You'll want a little toe in for the street. It helps the car track in a straight line. Zero toe with radials can cause the nose to be twitchy but not as bad as toe out.
You'll want a little toe in for the street. It helps the car track in a straight line. Zero toe with radials can cause the nose to be twitchy but not as bad as toe out.
09-20-12, 10:18 AM
#48
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Where to start...
Camber, depends on what the tire likes, which we don't know yet. 1.5 to 2 degrees should work to start but it depends on how much your car leans.
Caster, try to stay near stock specs to start because caster works best in certain relations to kingpin inclination and you have no way of changing KPI. With a ton of caster you can get some camber gain when turning but the downside is you are actually lifting the outside tire in relation to the chassis the more you turn the wheel.
Toe, this is where you have to think about your trade off. Street driving or auto-x? Auto-x you probably want some toe out maybe 1/8" or as much as a 1/4" if there are no straight sections. The car will hunt for curbs on the street but it will turn in awesome. On the street stay stock. Toe can be a quick adjustment once you have a baseline. Make sure the steering arms are centered and both outer arms are the same length.
What I would do is see how much toe is gained or lost with each turn of the adjuster and write it down in your car notes(oh yea, start a notebook of your set ups and keep track of everything you ever change, weather conditions, course surface, planet alignments etc etc)
Once you have a baseline you can start playing with stuff with string alignments and maybe buy a cheap camber gauge. A proper alignment for the course will make a world of difference and you can go back and forth from street to auto-x settings and under 15 minutes.
Camber, depends on what the tire likes, which we don't know yet. 1.5 to 2 degrees should work to start but it depends on how much your car leans.
Caster, try to stay near stock specs to start because caster works best in certain relations to kingpin inclination and you have no way of changing KPI. With a ton of caster you can get some camber gain when turning but the downside is you are actually lifting the outside tire in relation to the chassis the more you turn the wheel.
Toe, this is where you have to think about your trade off. Street driving or auto-x? Auto-x you probably want some toe out maybe 1/8" or as much as a 1/4" if there are no straight sections. The car will hunt for curbs on the street but it will turn in awesome. On the street stay stock. Toe can be a quick adjustment once you have a baseline. Make sure the steering arms are centered and both outer arms are the same length.
What I would do is see how much toe is gained or lost with each turn of the adjuster and write it down in your car notes(oh yea, start a notebook of your set ups and keep track of everything you ever change, weather conditions, course surface, planet alignments etc etc)
Once you have a baseline you can start playing with stuff with string alignments and maybe buy a cheap camber gauge. A proper alignment for the course will make a world of difference and you can go back and forth from street to auto-x settings and under 15 minutes.
