Alignment methods compare and contrast
09-12-2014, 12:23 PM
#21
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I don't know what it is. I think of it as front and rear axle square with chassis centerline. Maybe what you are saying means the same thing. I knew nothing about strings before I saw your video. What I am thinking is strings save time? Am I correct in understanding that setting rear toe with strings is setting the thrust to zero as a byproduct of setting rear toe? My method takes more time 2 steps. In my method you set thrust by adjusting toe to whatever it needs to be on one rear wheel to get equal measurements to zero the thrust "then" you adjust toe again on both rear wheels to get desired toe in or toe out.
Back in the good old days before shops had 4 wheel alignment racks C2 and C3 Corvettes were aligned by backing the car onto the rack, setting rear camber followed by rear toe/thrust angle and then turning the car around on the rack and doing the front.
If you are using toe plates all of your toe measurements are in total toe. The only indication you get of which wheel needs more adjustment is the laser thrust angle check which shows that one side is different than the other. After doing a few alignments you sort of have an idea of which side needs to be adjusted first.
With the strings you get a quick reading of which wheel needs to be adjusted to bring the thrust angle into the correct range.
Based on what I read about the Smart Strings is you are basically making your measurements off the car's centerline. As Froggy's video shows you make sure the strings are equidistance from the hubs on each axle. That should pretty much approximate them being referenced to the center line.
Maybe I place too much importance on equal right and left turns and thus a zero thrust. I wonder about the relative accuracy of strings where you are measuring from front lip to string and rear lip to string over only 18" while I set thrust over the 100" wheel base. I think I got you beat on accuracy but perhaps accuracy here is not that important? I place emphasis on thrust due to my own bias from science backround. One small error at the start magnifys itself as the process evolves.
I think a correct toe setting is more important than a zero thrust angle. However, I am **** about thrust as well. If you get it as close to zero as possible I think it reduces the differences in handling you get when going around a left or right turn.
Perhaps a good test would be to sort of use a hybrid approach like Ernie with stings and a laser. When I read his method I first thought...if Ernie is using strings why the laser if strings can do thrust? But maybe until we amateurs can confirm alignment science doing strings for thrust first and "faster" (killing two birds with one stone) then confirm thrust with the laser make sense. Once proven that measure over 18" is as good as measure over 100" then ditch the laser if you want to save time and effort.
I think it is just as accurate to make the thrust angle measurement with strings as it is with the laser.
It isn't that hard to measure 32nds on a tape measure and that is all the resolution you need since toe and thrust angles are intertwined with a preference to having the toe set where you want it Vs the thrust angle being dead nuts on.
Back in the good old days before shops had 4 wheel alignment racks C2 and C3 Corvettes were aligned by backing the car onto the rack, setting rear camber followed by rear toe/thrust angle and then turning the car around on the rack and doing the front.
If you are using toe plates all of your toe measurements are in total toe. The only indication you get of which wheel needs more adjustment is the laser thrust angle check which shows that one side is different than the other. After doing a few alignments you sort of have an idea of which side needs to be adjusted first.
With the strings you get a quick reading of which wheel needs to be adjusted to bring the thrust angle into the correct range.
Based on what I read about the Smart Strings is you are basically making your measurements off the car's centerline. As Froggy's video shows you make sure the strings are equidistance from the hubs on each axle. That should pretty much approximate them being referenced to the center line.
Maybe I place too much importance on equal right and left turns and thus a zero thrust. I wonder about the relative accuracy of strings where you are measuring from front lip to string and rear lip to string over only 18" while I set thrust over the 100" wheel base. I think I got you beat on accuracy but perhaps accuracy here is not that important? I place emphasis on thrust due to my own bias from science backround. One small error at the start magnifys itself as the process evolves.
I think a correct toe setting is more important than a zero thrust angle. However, I am **** about thrust as well. If you get it as close to zero as possible I think it reduces the differences in handling you get when going around a left or right turn.
Perhaps a good test would be to sort of use a hybrid approach like Ernie with stings and a laser. When I read his method I first thought...if Ernie is using strings why the laser if strings can do thrust? But maybe until we amateurs can confirm alignment science doing strings for thrust first and "faster" (killing two birds with one stone) then confirm thrust with the laser make sense. Once proven that measure over 18" is as good as measure over 100" then ditch the laser if you want to save time and effort.
I think it is just as accurate to make the thrust angle measurement with strings as it is with the laser.
It isn't that hard to measure 32nds on a tape measure and that is all the resolution you need since toe and thrust angles are intertwined with a preference to having the toe set where you want it Vs the thrust angle being dead nuts on.
Bill
Last edited by Bill Dearborn; 09-12-2014 at 12:34 PM.
09-12-2014, 12:54 PM
#22
Melting Slicks
Thread Starter
If you are using toe plates all of your toe measurements are in total toe. The only indication you get of which wheel needs more adjustment is the laser thrust angle check which shows that one side is different than the other. After doing a few alignments you sort of have an idea of which side needs to be adjusted first.
With the strings you get a quick reading of which wheel needs to be adjusted to bring the thrust angle into the correct range.
Bill
With the strings you get a quick reading of which wheel needs to be adjusted to bring the thrust angle into the correct range.
Bill
I dabbled with strings on jackstands once. A big problem I had was tension on the string and string droop over set-up time and hitting the strings. One of the things that really stood out was Froggy's bunggie cord trick. Since I work lifting the car up and down on a hoist, I'm still thinking it could be faster setting up jackstands to hold strings than hooking a string fixture on the car.
09-12-2014, 01:22 PM
#23
Race Director
Hot links to camber:
Toe:
So pizzed, just typed out a bunch of responses & idiots at MS rebooted my computer to do updates automatically & lost it all. Sheesh.
Here goes again:
For thrust, what Bill said, exact equi distance of string off axle = same as centerline. This is my assumption, if your car is "bent" you need to fix that first, then proceed.
I set the rear toe & camber EXACT same side to side. If my car & axles are true then thrust is true.
For plates I use Home Depot plastic bags 2 each side = 4 very slippy bits of thin plastic, this on top of some particle board with white slippy finish cut exact to sit on top of the ramp so tires move free & no contact with edges of ramp. I tape the bag edges so no chasing bags around the garage.
For accuracy I read machinest ruler to 64ths. Actually because the 64ths lines are so close I use the 32nds and my eyes to measure 1/2 a 32nds. Keep both eyes open or the measurement will change. Try it. For the laser setups I have observed it seems hard that they would beat 64ths. You are measuring toe from front of rim to back of rim & difference is toe (of course). If you wanted you could make a straight edge to "extend" the rim, but IMO it's unnecessary.
My big complaint with strings is time to setup the strings, they MUST be exact side to side off axles. When you adjust one end (say Pass) you also move the other end (Pass) a tiny amount, and so on, so it's an iterative process, take me almost an hour to get perfect. Laser probably faster here.
My question with laser is there seems to be a lot of necessary moving around of the laser device & how do you know you get it EXACTLY back in the same spot on the axle each time & the clamps don't shift and the ruler on the other end does not move?
With strings they are very solid & unless you walk into them they never move so you can triple check left to right, bounce/settle/adjust/check and so on all day & the strings just sit there good to go. Roll the car, drive off the ramp, whatever, strings stay good.
Easy to verify strings & I have, they stay good - use the little bungee trick.
I think of my alignment as setting each corner 100% independent of the other 3 and being true to the axle/centerline of the car. So if my LF is 1/16 out and my RF is 1/16 out my total toe is 2/16 (1/8). I have no need (toe plates) to check this, I could if I wanted, but if my confidence level is high that the process & my execution of the process is good, I don't bother.
Proof is how my car handles on the track.
Also my proof is, is the steering wheel 100% straight? Last two times it has been 100% straight. What a nice feeling when you get that result. If it's not straight you did something along the line wrong, usually a ruler reading or settling suspension.
Of course worn parts will make this whole process useless. Ball joints/bearings/rod ends & more.
If you have stock bushings none of this can be as accurate as I describe (for others who come across this thread). That's why GM has a "range" of alignment values. Not good enough for serious handling. But that's another thread.
If I missed responding on any point please bring it up.
You always want to do "before" measurements, most of the time I am only doing one front & one rear corner for camber. Toe all 4 corners usually.
Keep an alignment notebook & the more you do it the easier it gets. I actually do camber one day & toe the next. Gettin' old.
I do disconnected bars for corner weight (of course) put them back zero preload & I leave them on for alignment. Maybe a LARGE camber adjustment would necessitate a sway bar disconnect? I'm not sure.
Toe:
So pizzed, just typed out a bunch of responses & idiots at MS rebooted my computer to do updates automatically & lost it all. Sheesh.
Here goes again:
For thrust, what Bill said, exact equi distance of string off axle = same as centerline. This is my assumption, if your car is "bent" you need to fix that first, then proceed.
I set the rear toe & camber EXACT same side to side. If my car & axles are true then thrust is true.
For plates I use Home Depot plastic bags 2 each side = 4 very slippy bits of thin plastic, this on top of some particle board with white slippy finish cut exact to sit on top of the ramp so tires move free & no contact with edges of ramp. I tape the bag edges so no chasing bags around the garage.
For accuracy I read machinest ruler to 64ths. Actually because the 64ths lines are so close I use the 32nds and my eyes to measure 1/2 a 32nds. Keep both eyes open or the measurement will change. Try it. For the laser setups I have observed it seems hard that they would beat 64ths. You are measuring toe from front of rim to back of rim & difference is toe (of course). If you wanted you could make a straight edge to "extend" the rim, but IMO it's unnecessary.
My big complaint with strings is time to setup the strings, they MUST be exact side to side off axles. When you adjust one end (say Pass) you also move the other end (Pass) a tiny amount, and so on, so it's an iterative process, take me almost an hour to get perfect. Laser probably faster here.
My question with laser is there seems to be a lot of necessary moving around of the laser device & how do you know you get it EXACTLY back in the same spot on the axle each time & the clamps don't shift and the ruler on the other end does not move?
With strings they are very solid & unless you walk into them they never move so you can triple check left to right, bounce/settle/adjust/check and so on all day & the strings just sit there good to go. Roll the car, drive off the ramp, whatever, strings stay good.
Easy to verify strings & I have, they stay good - use the little bungee trick.
I think of my alignment as setting each corner 100% independent of the other 3 and being true to the axle/centerline of the car. So if my LF is 1/16 out and my RF is 1/16 out my total toe is 2/16 (1/8). I have no need (toe plates) to check this, I could if I wanted, but if my confidence level is high that the process & my execution of the process is good, I don't bother.
Proof is how my car handles on the track.
Also my proof is, is the steering wheel 100% straight? Last two times it has been 100% straight. What a nice feeling when you get that result. If it's not straight you did something along the line wrong, usually a ruler reading or settling suspension.
Of course worn parts will make this whole process useless. Ball joints/bearings/rod ends & more.
If you have stock bushings none of this can be as accurate as I describe (for others who come across this thread). That's why GM has a "range" of alignment values. Not good enough for serious handling. But that's another thread.
If I missed responding on any point please bring it up.
You always want to do "before" measurements, most of the time I am only doing one front & one rear corner for camber. Toe all 4 corners usually.
Keep an alignment notebook & the more you do it the easier it gets. I actually do camber one day & toe the next. Gettin' old.
I do disconnected bars for corner weight (of course) put them back zero preload & I leave them on for alignment. Maybe a LARGE camber adjustment would necessitate a sway bar disconnect? I'm not sure.
Last edited by froggy47; 09-12-2014 at 02:14 PM.
09-12-2014, 02:30 PM
#24
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By the way, where did you guys purchase your machinists rulers?
Bill
Bill
09-12-2014, 02:46 PM
#25
Safety Car
as to making sure the ruler is in the same position for laser thrust check
I have a magnet which just fits the front hubs, it is bolted to my ruler. the height in the rear is set by the jack stand and the longer angle bolted to the level sits across the tire, That said it's not all that critical because it is measures so far away. the handling on track is what counts. and for me the tire wear on the street (even and lengthy)
09-12-2014, 02:54 PM
#26
Race Director
Harbor freight
as to making sure the ruler is in the same position for laser thrust check
I have a magnet which just fits the front hubs, it is bolted to my ruler. the height in the rear is set by the jack stand and the longer angle bolted to the level sits across the tire, That said it's not all that critical because it is measures so far away. the handling on track is what counts. and for me the tire wear on the street (even and lengthy)
as to making sure the ruler is in the same position for laser thrust check
I have a magnet which just fits the front hubs, it is bolted to my ruler. the height in the rear is set by the jack stand and the longer angle bolted to the level sits across the tire, That said it's not all that critical because it is measures so far away. the handling on track is what counts. and for me the tire wear on the street (even and lengthy)
Mine is a 6 inch kind you clip to your shirt pocket (nerd style)
09-12-2014, 04:58 PM
#27
Melting Slicks
Thread Starter
Here is my strings question: don't you need to know the difference in front track vs. rear track at the wheel faces so that the strings are parallel to the chassis centerline? To exagerate, if you had a rear track 4 ft and front track 2ft and you set up strings about a ft from each hub then measure from string to wheelface front and rear you would have natural toe in even if there was net zero toe. Does that make sense?
09-12-2014, 05:03 PM
#28
Safety Car
Here is my strings question: don't you need to know the difference in front track vs. rear track at the wheel faces so that the strings are parallel to the chassis centerline? To exagerate, if you had a rear track 4 ft and front track 2ft and you set up strings about a ft from each hub then measure from string to wheelface front and rear you would have natural toe in even if there was net zero toe. Does that make sense?
09-12-2014, 07:02 PM
#29
Race Director
yes and no the smart strings come with machined end bars with notches for the strings to lay in. if you put them in the same notches as in 2nd one from the end and then center by measuring string to hub you will have a perfectly square setup the front & rear will just be farther from the strings
So the measurements off the hub are different front / rear which does not matter.
If you use jack stands you need to replicate that.
Good question.
The machined bars are very high precision pieces, don't drop/bend.
09-12-2014, 08:12 PM
#30
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So I finished setting up my Smart Strings today. I have them centered on the hubs as close as I can get them. With the car sitting on the floor it became a real exercise to get the strings to pass through the center of the hubs. With no reference marks the parallax view can really screw you up. To help I used a tape measure to measure the distance from the floor to the center of the hub. This reduced the parallax considerably. I determined the center of the front hubs is 12.5 inches off the floor and the center of the rear hubs is 13 inches off the floor. I used those measurements to set the string height at each wheel. When I laid down on the floor and sighted along the strings it looked like each of the strings passed through the center of the respective hubs. Then I horizontally centered the strings by setting the front of the string 8.5 inches from the center of the hub on each side and the rear of the string 4 3/16 in from the end of each rear axle shaft.
Then I measured the toe at each wheel and got some interesting results. First some background. Last week I had both front tie rods and the steering rack replaced and the shop also checked the rear tie rods. After the parts were replaced the mechanic reset the toe at all 4 wheels. He said he test drove it and it drove straight with the steering wheel also straight which I confirmed when I drove the car home.
LF measurement showed the two edges of the wheel were at 2 12/16 inches or zero toe while the RF measurement showed the two edges of that wheel were at 2 11/16 inches for zero toe. The question that raised was how come there was a 1/16 in difference in the distance from the center of the hub to the face of the wheel from one side of the car to the other?
Then I measured the rear toe the LR read 1 12/32 inches from both edges of the wheel to the string, the RR read 1 12/32 inches at the rear edge of the wheel but read 1 8/32 inches at the front edge. That means the RR wheel is toed in (correction toed out) 4/32 across 20.5 inches which is the outside diameter of the stock 19 inch wheel (about .43 degrees based on the attached chart). The thrust angle would be pointed somewhere toward the left (correction to the right) which should mean with zero toe the steering wheel should be turned to the left (correction to the right) to compensate for the thrust angle error as I drive. I know if I change the RR to zero toe the distance from the face of the right rear wheel to the end of the axle will be less than the LR which has me wondering again.
I have marked the positions of each bar and bracket in the tool so I can get a quicker setup the next time I use it. However, due to the coarseness of string adjustment I will probably fine tune the string placement each time I use them.
Any thoughts or comments about my ramblings are welcome.
Bill
Then I measured the toe at each wheel and got some interesting results. First some background. Last week I had both front tie rods and the steering rack replaced and the shop also checked the rear tie rods. After the parts were replaced the mechanic reset the toe at all 4 wheels. He said he test drove it and it drove straight with the steering wheel also straight which I confirmed when I drove the car home.
LF measurement showed the two edges of the wheel were at 2 12/16 inches or zero toe while the RF measurement showed the two edges of that wheel were at 2 11/16 inches for zero toe. The question that raised was how come there was a 1/16 in difference in the distance from the center of the hub to the face of the wheel from one side of the car to the other?
Then I measured the rear toe the LR read 1 12/32 inches from both edges of the wheel to the string, the RR read 1 12/32 inches at the rear edge of the wheel but read 1 8/32 inches at the front edge. That means the RR wheel is toed in (correction toed out) 4/32 across 20.5 inches which is the outside diameter of the stock 19 inch wheel (about .43 degrees based on the attached chart). The thrust angle would be pointed somewhere toward the left (correction to the right) which should mean with zero toe the steering wheel should be turned to the left (correction to the right) to compensate for the thrust angle error as I drive. I know if I change the RR to zero toe the distance from the face of the right rear wheel to the end of the axle will be less than the LR which has me wondering again.
I have marked the positions of each bar and bracket in the tool so I can get a quicker setup the next time I use it. However, due to the coarseness of string adjustment I will probably fine tune the string placement each time I use them.
Any thoughts or comments about my ramblings are welcome.
Bill
Last edited by Bill Dearborn; 09-13-2014 at 10:54 AM.
09-12-2014, 08:22 PM
#31
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Bill
09-12-2014, 11:00 PM
#33
Race Director
Basically the strings and the brackets that hold them form a box around the car. If you set the strings so they are equi distance from each end of the front axle and equi distance from each end of the rear axle the box will be centered on the car. Once you know the total distance to center the box you don't need to center it any more. For instance the box could be moved to the right or the left of the car and as long as the box is parallel to the car it doesn't matter if it is centered. For instance if I took my measurements of 8.5 inches from hub to string on each side of the car in front and offset the box 2 inches to toward the driver's side the front measurement from the front left hub could be 10.5 inches and the distance from the right front hub would then be 6.5 inches. There would be a similar change in the rear where the left side would go from 4 3/16 to 6 3/16 and the right side would drop to 2 3/16.
Bill
Bill
09-12-2014, 11:17 PM
#35
Just one note. Anytime one is comparing alignment settings with numbers, as opposed to degrees, consider they may be meaningless. Reason is because different people measure differently. Example, some measure toe at the rim while others measure at the sidewall. All else being equal, identical toe numbers but different measuring locations(distance from hub center) will be completely different in terms of degrees. If someone says that 1/8" toe out works well yet they measured from the sidewall and you set yours using the rim (assuming identical size and shape rim) you will actually have more toe. It can get even more complicated, but this is the easiest way for me to describe it. So always keep that in mind when considering others recommendations. This doesn't even consider how square ones car is. Often times it is talked about how people shift the rear crossmember to get the camber where they want. IMO, having the front and rear crossmembers (or rear axle in stick axle cars) square to eachother is more important than having a desirable camber number in the rear. There are other ways to correct that. Lastly, when doing all that one must consider the relationship of the lower suspension crossmember with the upper control arm pickup points (independent suspensions). Moving the crossmember can change the relationship and move the instant center left to right (assuming control arm lengths are the same left to right).
09-12-2014, 11:18 PM
#36
Race Director
So I finished setting up my Smart Strings today. I have them centered on the hubs as close as I can get them. With the car sitting on the floor it became a real exercise to get the strings to pass through the center of the hubs. With no reference marks the parallax view can really screw you up. To help I used a tape measure to measure the distance from the floor to the center of the hub. This reduced the parallax considerably. I determined the center of the front hubs is 12.5 inches off the floor and the center of the rear hubs is 13 inches off the floor. I used those measurements to set the string height at each wheel. When I laid down on the floor and sighted along the strings it looked like each of the strings passed through the center of the respective hubs. Then I horizontally centered the strings by setting the front of the string 8.5 inches from the center of the hub on each side and the rear of the string 4 3/16 in from the end of each rear axle shaft.
I have come to the conclusion, just from doing these diy alignments for over 4 years now, that the string distance "off the floor" only needs to be good & close but not EXACT. I eyeball it. Laying on the floor. The measure of the string off the hub, side to side, I strive to make that one exact, & seems to work for me.
Then I measured the toe at each wheel and got some interesting results. First some background. Last week I had both front tie rods and the steering rack replaced and the shop also checked the rear tie rods. After the parts were replaced the mechanic reset the toe at all 4 wheels. He said he test drove it and it drove straight with the steering wheel also straight which I confirmed when I drove the car home.
LF measurement showed the two edges of the wheel were at 2 12/16 inches or zero toe while the RF measurement showed the two edges of that wheel were at 2 11/16 inches for zero toe. The question that raised was how come there was a 1/16 in difference in the distance from the center of the hub to the face of the wheel from one side of the car to the other?
Your "box" was shifted a tiny bit.
Then I measured the rear toe the LR read 1 12/32 inches from both edges of the wheel to the string, the RR read 1 12/32 inches at the rear edge of the wheel but read 1 8/32 inches at the front edge. That means the RR wheel is toed in 4/32 across 20.5 inches which is the outside diameter of the stock 19 inch wheel (about .43 degrees based on the attached chart). The thrust angle would be pointed somewhere toward the left which should mean with zero toe the steering wheel should be turned to the left to compensate for the thrust angle error as I drive. I know if I change the RR to zero toe the distance from the face of the right rear wheel to the end of the axle will be less than the LR which has me wondering again.
That's the box shifted again I think. Also you are within the range (alignment wise) of what your guy could do, and to him & you it "felt" good. We are all trying for "perfect" and with a street car, I'm not sure it's possible.
I have marked the positions of each bar and bracket in the tool so I can get a quicker setup the next time I use it. However, due to the coarseness of string adjustment I will probably fine tune the string placement each time I use them.
Any thoughts or comments about my ramblings are welcome.
Bill
I have come to the conclusion, just from doing these diy alignments for over 4 years now, that the string distance "off the floor" only needs to be good & close but not EXACT. I eyeball it. Laying on the floor. The measure of the string off the hub, side to side, I strive to make that one exact, & seems to work for me.
Then I measured the toe at each wheel and got some interesting results. First some background. Last week I had both front tie rods and the steering rack replaced and the shop also checked the rear tie rods. After the parts were replaced the mechanic reset the toe at all 4 wheels. He said he test drove it and it drove straight with the steering wheel also straight which I confirmed when I drove the car home.
LF measurement showed the two edges of the wheel were at 2 12/16 inches or zero toe while the RF measurement showed the two edges of that wheel were at 2 11/16 inches for zero toe. The question that raised was how come there was a 1/16 in difference in the distance from the center of the hub to the face of the wheel from one side of the car to the other?
Your "box" was shifted a tiny bit.
Then I measured the rear toe the LR read 1 12/32 inches from both edges of the wheel to the string, the RR read 1 12/32 inches at the rear edge of the wheel but read 1 8/32 inches at the front edge. That means the RR wheel is toed in 4/32 across 20.5 inches which is the outside diameter of the stock 19 inch wheel (about .43 degrees based on the attached chart). The thrust angle would be pointed somewhere toward the left which should mean with zero toe the steering wheel should be turned to the left to compensate for the thrust angle error as I drive. I know if I change the RR to zero toe the distance from the face of the right rear wheel to the end of the axle will be less than the LR which has me wondering again.
That's the box shifted again I think. Also you are within the range (alignment wise) of what your guy could do, and to him & you it "felt" good. We are all trying for "perfect" and with a street car, I'm not sure it's possible.
I have marked the positions of each bar and bracket in the tool so I can get a quicker setup the next time I use it. However, due to the coarseness of string adjustment I will probably fine tune the string placement each time I use them.
Any thoughts or comments about my ramblings are welcome.
Bill
Last edited by froggy47; 09-12-2014 at 11:28 PM.
09-12-2014, 11:21 PM
#37
Race Director
Just one note. Anytime one is comparing alignment settings with numbers, as opposed to degrees, consider they may be meaningless. Reason is because different people measure differently. Example, some measure toe at the rim while others measure at the sidewall. All else being equal, identical toe numbers but different measuring locations(distance from hub center) will be completely different in terms of degrees. If someone says that 1/8" toe out works well yet they measured from the sidewall and you set yours using the rim (assuming identical size and shape rim) you will actually have more toe. It can get even more complicated, but this is the easiest way for me to describe it. So always keep that in mind when considering others recommendations. This doesn't even consider how square ones car is. Often times it is talked about how people shift the rear crossmember to get the camber where they want. IMO, having the front and rear crossmembers (or rear axle in stick axle cars) square to eachother is more important than having a desirable camber number in the rear. There are other ways to correct that. Lastly, when doing all that one must consider the relationship of the lower suspension crossmember with the upper control arm pickup points (independent suspensions). Moving the crossmember can change the relationship and move the instant center left to right (assuming control arm lengths are the same left to right).
When anyone asks me my alignment settings, I chuckle & tell them what they are, but advise them that YMMV. Not sure if they know why but this is why.
Last edited by froggy47; 09-12-2014 at 11:23 PM.
09-12-2014, 11:24 PM
#38
Melting Slicks
Thread Starter
I can see why Froggy said it took so long to set up the "box" and now understand the importance of the slotted string rods. Jackstands holding strings would be even more difficult and mean you must physically find chassis centerline to measure off of. The smart rods make that not necessary.
I can't understand why Bill is off that 1/16". A 1/16th is pretty big. It is parallax reading the ruler from a different angle error? Is it possible that string on one side is not through the hub center so that camber changes the point at which your ruler hits the hub, thus your measure is longer or shorter due to camber? Or is your ruler not level from center measure point on hub to the string touching the ruler? If your ruler is swinging on an arc to touch the string to read the measure that could account for a 1/16". An error like that can't happen based on my small grasp of how strings work.
I can't understand why Bill is off that 1/16". A 1/16th is pretty big. It is parallax reading the ruler from a different angle error? Is it possible that string on one side is not through the hub center so that camber changes the point at which your ruler hits the hub, thus your measure is longer or shorter due to camber? Or is your ruler not level from center measure point on hub to the string touching the ruler? If your ruler is swinging on an arc to touch the string to read the measure that could account for a 1/16". An error like that can't happen based on my small grasp of how strings work.
09-12-2014, 11:31 PM
#39
Race Director
Basically the strings and the brackets that hold them form a box around the car. If you set the strings so they are equi distance from each end of the front axle and equi distance from each end of the rear axle the box will be centered on the car. Once you know the total distance to center the box you don't need to center it any more. For instance the box could be moved to the right or the left of the car and as long as the box is parallel to the car it doesn't matter if it is centered. For instance if I took my measurements of 8.5 inches from hub to string on each side of the car in front and offset the box 2 inches to toward the driver's side the front measurement from the front left hub could be 10.5 inches and the distance from the right front hub would then be 6.5 inches. There would be a similar change in the rear where the left side would go from 4 3/16 to 6 3/16 and the right side would drop to 2 3/16.
Bill
Bill
09-12-2014, 11:36 PM
#40
Race Director
I can see why Froggy said it took so long to set up the "box" and now understand the importance of the slotted string rods. Jackstands holding strings would be even more difficult and mean you must physically find chassis centerline to measure off of. The smart rods make that not necessary.
I can't understand why Bill is off that 1/16". A 1/16th is pretty big. It is parallax reading the ruler from a different angle error? Is it possible that string on one side is not through the hub center so that camber changes the point at which your ruler hits the hub, thus your measure is longer or shorter due to camber? Or is your ruler not level from center measure point on hub to the string touching the ruler? If your ruler is swinging on an arc to touch the string to read the measure that could account for a 1/16". An error like that can't happen based on my small grasp of how strings work.
I can't understand why Bill is off that 1/16". A 1/16th is pretty big. It is parallax reading the ruler from a different angle error? Is it possible that string on one side is not through the hub center so that camber changes the point at which your ruler hits the hub, thus your measure is longer or shorter due to camber? Or is your ruler not level from center measure point on hub to the string touching the ruler? If your ruler is swinging on an arc to touch the string to read the measure that could account for a 1/16". An error like that can't happen based on my small grasp of how strings work.