Alignment methods compare and contrast
#61
Melting Slicks
Thread Starter
Some info from Smart Strings user manual especially #6.
If anyone on the thread has actually done an alignment from true centerline, please, describe how you determine it & then how you use strings or lasers coming off true centerline. I don't see how it's possible on a street car on a garage floor.
If anyone on the thread has actually done an alignment from true centerline, please, describe how you determine it & then how you use strings or lasers coming off true centerline. I don't see how it's possible on a street car on a garage floor.
#62
Melting Slicks
Thread Starter
I can feel 2lb changes in tire pressure and that is a number most drivers are comfortable with. 3lb changes almost anyone can feel. I have not tested enough alignment variation to feel changes. I have set things to where the faster friends tell me and try and learn to drive the car. Can we comment on how much change and what kind of change might we use to optimize at different places in a corner, under braking , and on the gas? For example some front toe out helps corner entry turn in. If you wanted more corner entry turn in how much more should one try, 1/8" 3/16" so you can definitely feel it? I think we need to know things like camber gain/loss for the vette as the suspension travels before we can answer those questions? I've never looked into those changes either. For example I found out rear camber changes really mess with thrust. What happens to rear toe under braking vs. acceleration?
#63
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I can feel 2lb changes in tire pressure and that is a number most drivers are comfortable with. 3lb changes almost anyone can feel. I have not tested enough alignment variation to feel changes. I have set things to where the faster friends tell me and try and learn to drive the car. Can we comment on how much change and what kind of change might we use to optimize at different places in a corner, under braking , and on the gas? For example some front toe out helps corner entry turn in. If you wanted more corner entry turn in how much more should one try, 1/8" 3/16" so you can definitely feel it? I think we need to know things like camber gain/loss for the vette as the suspension travels before we can answer those questions? I've never looked into those changes either. For example I found out rear camber changes really mess with thrust. What happens to rear toe under braking vs. acceleration?
Of course there will be some camber changes that will affect things as well. Weight transfer to the front will cause some increased negative camber while the rear will see some decreased negative camber. Those changes will affect toe as well.
As for suspension settings I have noticed I like a fair amount of rear toe in when on the track. I don't like driving a loose race car so more rear toe tames the rear and allows me to add more power going through turns. I can tell when it isn't set right. One time at the Glen I went under the rear and adjusted both tie rods two flats each to increase the 1/16 toe in that I had set in to a total of 1/8. The car seemed to handle the Esses much better especially Turn 3 where the rear of the car had been twitching to the right as I went by the Apex. With the increased toe in I was able to go through the turn almost wide open with an appropriate increase in speed at the end of the back street. I thought about adding another 1/8 to see if I could go through Wide Open like I used to do with my previous cars.
Bill
#65
Race Director
I can feel 2lb changes in tire pressure and that is a number most drivers are comfortable with. 3lb changes almost anyone can feel. I have not tested enough alignment variation to feel changes. I have set things to where the faster friends tell me and try and learn to drive the car. Can we comment on how much change and what kind of change might we use to optimize at different places in a corner, under braking , and on the gas? For example some front toe out helps corner entry turn in. If you wanted more corner entry turn in how much more should one try, 1/8" 3/16" so you can definitely feel it? I think we need to know things like camber gain/loss for the vette as the suspension travels before we can answer those questions? I've never looked into those changes either. For example I found out rear camber changes really mess with thrust. What happens to rear toe under braking vs. acceleration?
For myself I just last alignment went from zero toe F, to 1/8 out & it CLEARLY did not feel worse, I "think" it's a little crisper turn in (corner entry). The rear I went from 3/8 total in to 1/2 total in and my rear grip was great, almost to not being able to rotate the car with power.
#66
Melting Slicks
Thread Starter
"Flats"...you mean you loosen the rear tierod nut allowing it to sit on the rod. Then moving the rod looking for movement of 2 flats on the passive nut going along for the ride correct?
#67
Melting Slicks
Thread Starter
For myself I just last alignment went from zero toe F, to 1/8 out & it CLEARLY did not feel worse, I "think" it's a little crisper turn in (corner entry). The rear I went from 3/8 total in to 1/2 total in and my rear grip was great, almost to not being able to rotate the car with power.
#68
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I mark the flats on the tie rod with red fingernail polish so I can reference how many turns I have made.
Bill
#69
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I have no idea what is too much rear toe-in because I have never tested it and do not know if it can be empirically derived with math like calculating chassis frequency to guess at empirical spring rate starting points. For anyone else reading thinking more is better, like tire pressure, "I think" there is a sweet spot to rear toe in where too little toe-in (towards toe out) causes oversteer or too much toe-in also causes oversteer. So don't be surprised out on track getting unexpected results that can put you in the weeds. Tip-toe.
When LG added a lot of rear toe in to my car at the Glen if felt much better to me on the track. When I took the car home I left it adjusted to his setting. However, on the street leading to my house the pavement was so rough the back end of the car was lifting off the pavement. If the left rear lifted the back end would jump that way and if the right rear lifted the back end would jump that way. Driving straight on that street was an exercise in flipping the steering wheel back and forth. It also rapidly wore the outside edges of my brand new EMTs and I got just over 3K miles before they corded. Once I reduced the toe from Lou's setting to close to zero the hopping around went away.
Bill
#70
Melting Slicks
Thread Starter
It is more of a feel type of thing. I think as long as you have some toe in the car will be stable enough. However, some people, like me, don't like the feel and won't push the gas pedal hard enough when the back end feels uncomfortable to them. You hear the Cup guys talk about it all the time. Some like driving a loose car and others don't.
When LG added a lot of rear toe in to my car at the Glen if felt much better to me on the track. When I took the car home I left it adjusted to his setting. However, on the street leading to my house the pavement was so rough the back end of the car was lifting off the pavement. If the left rear lifted the back end would jump that way and if the right rear lifted the back end would jump that way. Driving straight on that street was an exercise in flipping the steering wheel back and forth. It also rapidly wore the outside edges of my brand new EMTs and I got just over 3K miles before they corded. Once I reduced the toe from Lou's setting to close to zero the hopping around went away.
Bill
When LG added a lot of rear toe in to my car at the Glen if felt much better to me on the track. When I took the car home I left it adjusted to his setting. However, on the street leading to my house the pavement was so rough the back end of the car was lifting off the pavement. If the left rear lifted the back end would jump that way and if the right rear lifted the back end would jump that way. Driving straight on that street was an exercise in flipping the steering wheel back and forth. It also rapidly wore the outside edges of my brand new EMTs and I got just over 3K miles before they corded. Once I reduced the toe from Lou's setting to close to zero the hopping around went away.
Bill
#71
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It seems that you are talking about the important theory of "most important part of turn is apex to exit" getting on gas as hard as possible. How much toe did LG run on you? I do not know what happens to our rear end alignment settings under power. We know if we toe out we rear steer and are unstable into oversteer. So if LG is adding toe in my guess is that under power the rear squats improving grip and maybe loosing tow in and squatting could reduce the contact patch from camber gain? I have never put the rear through its travel and register what happens to camber and toe so that's a complete WAG. Your off track cruising wheel hop makes perfect sense because you have proven that the rear end is doing something completely different on power vs. coasting. Comments?
By the way I started changing my alignment from street to track this week. I have the Van Steel camber plates in the front. When I flipped them over to move the bolts out the camber went from -.4 to -4.7. I was able to use the Smart Strings to measure toe at each wheel and found it had gone from close to zero toe in to several inches. Using the measurements at each wheel I was able to determine how much I had to adjust each tie rod (1/32 per flat) to get the car to steer straightly. The left front would have required 15 turns plus 5 flats.
I also checked the thrust angle with my laser and knew what direction I had to move the rear wheels to get zero thrust but the string measurements showed me the left rear required no adjustment and all adjustments should be made at the right rear wheel to get the proper total toe and close to zero thrust angle.
Bill
#72
Burning Brakes
That was all done rolling around on a garage floor. Today I use lasers and digital levels like FatBillyBob and David Farmer so I don't use those holes.
#73
Racer
Your eyeballs & brain reading the ruler is a VERY critical part of the whole process & probably why alignment racks & systems were invented to eliminate the "human" error. If you can do it you can be as good or better than the machine IMO, but if you blink/sneeze/get interrupted/ etc you can end up with crap. This process needs you to be VERY focused on the task.
I once spent a half hour setting up my strings, after working on the car all day already. Finally got them all set right, when my big lab came running into the garage, knocking over a jack stand. She made it up to me with a big lick of the face.
#74
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Well I finished the alignment using the strings.
Front
left camber -3.0 == right camber -3.5
left caster +9.0 == right caster +8.4
left toe 0.0 == right toe 0.0
Rear
left camber -1.- == right camber -0.9
left toe 2/32 == right toe 2/32
Toe was measured at the rim edge. On the rear the rim edge is 19.5 in diameter.
So rear toe at each wheel in degrees is ~ .18 degrees using the Smart Strings conversion chart. Total toe is ~.36 degrees.
When I drove the car I ended up with a very slight steering wheel offset to the left. This may have been due to the crown on the road, the slightly lower right front caster which would pull the car to the right of just due to the inability to resolve adjustments any better than 1/32 of an inch. It is possible the right front is toed out by 1/64 but I knew I wasn't going to get any closer to 0 since I had to raise the car to make an adjustment, drive it back and forth in the driveway several times and then remeasure. It wasn't worth the time or effort to get it any closer.
The MacTool guy who lives on the other side of the hill stopped by to talk and watch for a few minutes and said the Cup teams he worked with would set up a string arrangement from the car center line to one side of the car and do their adjustments on that side, followed by using toe plates to get the other side. He said it was quicker that way although I would think it would be less accurate just due to tolerance stack up. He also talked about setting rear toe on solid axle cars. It is possible to adjust rear toe by bending the housing a certain amount and the full floater axles they use permit some bending. To get thrust angle they just move one side of the axle or the other.
Bill
Front
left camber -3.0 == right camber -3.5
left caster +9.0 == right caster +8.4
left toe 0.0 == right toe 0.0
Rear
left camber -1.- == right camber -0.9
left toe 2/32 == right toe 2/32
Toe was measured at the rim edge. On the rear the rim edge is 19.5 in diameter.
So rear toe at each wheel in degrees is ~ .18 degrees using the Smart Strings conversion chart. Total toe is ~.36 degrees.
When I drove the car I ended up with a very slight steering wheel offset to the left. This may have been due to the crown on the road, the slightly lower right front caster which would pull the car to the right of just due to the inability to resolve adjustments any better than 1/32 of an inch. It is possible the right front is toed out by 1/64 but I knew I wasn't going to get any closer to 0 since I had to raise the car to make an adjustment, drive it back and forth in the driveway several times and then remeasure. It wasn't worth the time or effort to get it any closer.
The MacTool guy who lives on the other side of the hill stopped by to talk and watch for a few minutes and said the Cup teams he worked with would set up a string arrangement from the car center line to one side of the car and do their adjustments on that side, followed by using toe plates to get the other side. He said it was quicker that way although I would think it would be less accurate just due to tolerance stack up. He also talked about setting rear toe on solid axle cars. It is possible to adjust rear toe by bending the housing a certain amount and the full floater axles they use permit some bending. To get thrust angle they just move one side of the axle or the other.
Bill
#75
Race Director
Well I finished the alignment using the strings.
Front
left camber -3.0 == right camber -3.5
left caster +9.0 == right caster +8.4
left toe 0.0 == right toe 0.0
Rear
left camber -1.- == right camber -0.9
left toe 2/32 == right toe 2/32
Toe was measured at the rim edge. On the rear the rim edge is 19.5 in diameter.
So rear toe at each wheel in degrees is ~ .18 degrees using the Smart Strings conversion chart. Total toe is ~.36 degrees.
When I drove the car I ended up with a very slight steering wheel offset to the left. This may have been due to the crown on the road, the slightly lower right front caster which would pull the car to the right of just due to the inability to resolve adjustments any better than 1/32 of an inch. It is possible the right front is toed out by 1/64 but I knew I wasn't going to get any closer to 0 since I had to raise the car to make an adjustment, drive it back and forth in the driveway several times and then remeasure. It wasn't worth the time or effort to get it any closer.
The MacTool guy who lives on the other side of the hill stopped by to talk and watch for a few minutes and said the Cup teams he worked with would set up a string arrangement from the car center line to one side of the car and do their adjustments on that side, followed by using toe plates to get the other side. He said it was quicker that way although I would think it would be less accurate just due to tolerance stack up. He also talked about setting rear toe on solid axle cars. It is possible to adjust rear toe by bending the housing a certain amount and the full floater axles they use permit some bending. To get thrust angle they just move one side of the axle or the other.
Bill
Front
left camber -3.0 == right camber -3.5
left caster +9.0 == right caster +8.4
left toe 0.0 == right toe 0.0
Rear
left camber -1.- == right camber -0.9
left toe 2/32 == right toe 2/32
Toe was measured at the rim edge. On the rear the rim edge is 19.5 in diameter.
So rear toe at each wheel in degrees is ~ .18 degrees using the Smart Strings conversion chart. Total toe is ~.36 degrees.
When I drove the car I ended up with a very slight steering wheel offset to the left. This may have been due to the crown on the road, the slightly lower right front caster which would pull the car to the right of just due to the inability to resolve adjustments any better than 1/32 of an inch. It is possible the right front is toed out by 1/64 but I knew I wasn't going to get any closer to 0 since I had to raise the car to make an adjustment, drive it back and forth in the driveway several times and then remeasure. It wasn't worth the time or effort to get it any closer.
The MacTool guy who lives on the other side of the hill stopped by to talk and watch for a few minutes and said the Cup teams he worked with would set up a string arrangement from the car center line to one side of the car and do their adjustments on that side, followed by using toe plates to get the other side. He said it was quicker that way although I would think it would be less accurate just due to tolerance stack up. He also talked about setting rear toe on solid axle cars. It is possible to adjust rear toe by bending the housing a certain amount and the full floater axles they use permit some bending. To get thrust angle they just move one side of the axle or the other.
Bill
If/when my steering wheel is off (but car is tracking good) I just put it back up the ramps and adjust the LF/RF by a couple of flats equal each side & don't even bother with any more measuring. Just make sure you go the right way both sides.
Last edited by froggy47; 09-22-2014 at 05:51 PM.
#76
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Did you want the front camber different by .5? Setup for your home track?
If/when my steering wheel is off (but car is tracking good) I just put it back up the ramps and adjust the LF/RF by a couple of flats equal each side & don't even bother with any more measuring. Just make sure you go the right way both sides.
If/when my steering wheel is off (but car is tracking good) I just put it back up the ramps and adjust the LF/RF by a couple of flats equal each side & don't even bother with any more measuring. Just make sure you go the right way both sides.
I had the number of shims behind the front dog bones maxed out on both sides of the car and I had 2 shims behind the rear dog bones. If I added two more shims on the passenger side rear dog bone I may have been able to equalize camber but I would also lose a fair amount of caster on that side which would make the car pull more in that direction.
Bill
#77
Melting Slicks
Thread Starter
Don't you have to add shims to front "and" rear UCA dogbones to lower camber "without" changing caster?
#78
Race Director
Bill, I have always let the caster "go off" a little side to side in favor of getting close to equal camber.
In my experience, a small caster difference does not make the car pull much/at all.
Toe difference will.
#79
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I am running Continental Slicks so want about 3 degrees camber. I installed the maximum number of shims I could get behind the front dog bones and half of that amount on the rear dog bones which reduced the camber on both sides but also increased caster.
If I add shims to the passenger side rear dog bone I may get camber closer to the driver's side but will also reduce caster on the passenger side which will increase the pull toward the right. It all depends on what I want to sacrifice.
Bill
#80
Melting Slicks
Thread Starter
FWIW, I cannot feel a difference in 1/2* of camber on the front either in turning or braking. I thought there might be a stability issue with threshold braking but did not find that to be the case. Others more sensitive or skilled might feel it.