C5 Centerline for Alignments
07-05-2015, 11:18 AM
#1
Instructor
Thread Starter
C5 Centerline for Alignments
I have access to scales and will be setting ride height and cross weight on my C5 Z06 after I put new tires on, in preparation for a HPDE at Sebring in about a month. Afterwards I will also be aligning the car myself and had some questions about measuring toe.........
I'm aware of the two diy methods for measuring toe, where in one method you measure the distance between the front and rear of the wheels on each axle with a tape measure and either some sort of giant calipers or toe plates. However, I don't like this method because it only measures total toe. You could easily have one wheel at 0 toe and the other at 1/8" toe in for instance and just assume that each wheel is at 1/16" toe in, because you measured 1/8" total toe. I wanted to use the string method instead, since that measures the toe at each wheel. However, I'm a little worried about setting up the string to be parallel to the vehicle center line. A lot of the guides I have found instruct you to set up the string so that it is equidistant from the ends of the front and rear axles on each side of the car. I question that because the end of the front and rear axle are not necessarily equidistant from the vehicle center line. This would mean that if set your strings this way, the strings are not parallel to the vehicle center line, thus throwing off your toe measurements. So I'm wondering if there is a relatively quick way to set the strings parallel to the actual vehicle center line. Is there a reference on the frame of the car or some place that you can measure from quickly while doing an alignment? Or is the difference in distance from the ends of the front and rear axle to the center line known? This way you could still use the axles as reference points, but then just add an extra offset to one axle. Thanks in advance!
I'm aware of the two diy methods for measuring toe, where in one method you measure the distance between the front and rear of the wheels on each axle with a tape measure and either some sort of giant calipers or toe plates. However, I don't like this method because it only measures total toe. You could easily have one wheel at 0 toe and the other at 1/8" toe in for instance and just assume that each wheel is at 1/16" toe in, because you measured 1/8" total toe. I wanted to use the string method instead, since that measures the toe at each wheel. However, I'm a little worried about setting up the string to be parallel to the vehicle center line. A lot of the guides I have found instruct you to set up the string so that it is equidistant from the ends of the front and rear axles on each side of the car. I question that because the end of the front and rear axle are not necessarily equidistant from the vehicle center line. This would mean that if set your strings this way, the strings are not parallel to the vehicle center line, thus throwing off your toe measurements. So I'm wondering if there is a relatively quick way to set the strings parallel to the actual vehicle center line. Is there a reference on the frame of the car or some place that you can measure from quickly while doing an alignment? Or is the difference in distance from the ends of the front and rear axle to the center line known? This way you could still use the axles as reference points, but then just add an extra offset to one axle. Thanks in advance!
07-05-2015, 11:34 AM
#2
Safety Car
I have access to scales and will be setting ride height and cross weight on my C5 Z06 after I put new tires on, in preparation for a HPDE at Sebring in about a month. Afterwards I will also be aligning the car myself and had some questions about measuring toe.........
I'm aware of the two diy methods for measuring toe, where in one method you measure the distance between the front and rear of the wheels on each axle with a tape measure and either some sort of giant calipers or toe plates. However, I don't like this method because it only measures total toe. You could easily have one wheel at 0 toe and the other at 1/8" toe in for instance and just assume that each wheel is at 1/16" toe in, because you measured 1/8" total toe. I wanted to use the string method instead, since that measures the toe at each wheel. However, I'm a little worried about setting up the string to be parallel to the vehicle center line. A lot of the guides I have found instruct you to set up the string so that it is equidistant from the ends of the front and rear axles on each side of the car. I question that because the end of the front and rear axle are not necessarily equidistant from the vehicle center line. This would mean that if set your strings this way, the strings are not parallel to the vehicle center line, thus throwing off your toe measurements. So I'm wondering if there is a relatively quick way to set the strings parallel to the actual vehicle center line. Is there a reference on the frame of the car or some place that you can measure from quickly while doing an alignment? Or is the difference in distance from the ends of the front and rear axle to the center line known? This way you could still use the axles as reference points, but then just add an extra offset to one axle. Thanks in advance!
I'm aware of the two diy methods for measuring toe, where in one method you measure the distance between the front and rear of the wheels on each axle with a tape measure and either some sort of giant calipers or toe plates. However, I don't like this method because it only measures total toe. You could easily have one wheel at 0 toe and the other at 1/8" toe in for instance and just assume that each wheel is at 1/16" toe in, because you measured 1/8" total toe. I wanted to use the string method instead, since that measures the toe at each wheel. However, I'm a little worried about setting up the string to be parallel to the vehicle center line. A lot of the guides I have found instruct you to set up the string so that it is equidistant from the ends of the front and rear axles on each side of the car. I question that because the end of the front and rear axle are not necessarily equidistant from the vehicle center line. This would mean that if set your strings this way, the strings are not parallel to the vehicle center line, thus throwing off your toe measurements. So I'm wondering if there is a relatively quick way to set the strings parallel to the actual vehicle center line. Is there a reference on the frame of the car or some place that you can measure from quickly while doing an alignment? Or is the difference in distance from the ends of the front and rear axle to the center line known? This way you could still use the axles as reference points, but then just add an extra offset to one axle. Thanks in advance!
07-05-2015, 04:38 PM
#3
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There are several ways to do that. One was shown to me by Lou G while at an event at the Glen. He used a toe gauge that was made out of rectangular tubing. It looked like a 3 sided box. The long end was long enough to stretch across the spread of the rear wheels plus a couple of inches and the other two ends were about 12 inches long. One had a flat plate extending from the far end that was used to touch the rim, the other had a similar plate but was marked so you could read a tape measure placed on the rim and stretched across the top of the gauge. This gave total toe. Then he used a Sears 24 inch digital laser level place along the side of the rear tire to shoot a laser forward to the front wheel well. A helper had a tape measure inserted between the front spokes and touching the frame around the spot the Z06 brake duct mounting bolt is located. The assistant read the location of the laser beam on the tape measure and they then checked the other side of the car to see if they got close to the same measurement. This allowed them to set rear toe and thrust angle so the tires were almost exactly toed in the same amount.
In the front it doesn't matter as much whether one tire is toed in more than the other since the steering wheel will just turn to center the toe from side to side. The only issue with that is how much can it turn before the AH gets messed up due to too large of a steering angle being read by the EBCM when the car is being driven straight down the road. The solution to that problem is to use the laser to shoot from the front to the rear and to get the side to side measurements close to equal. You are doing this measurement over the distance of the car's wheel base so differences of 1/8 in from side to side are very small differences at the wheels.
I changed this process slightly by inserting the tape measure into the center of the hub or onto the rear axle stub before using the laser level.
If you have a caster/camber gauge, some metal plates with grease between them to set under the wheels, toe plates, a laser level, a 20 inch long rule and a jack stand that can be used to tape the rule to you can pretty much do a one person toe setting while at the track.
Recently I moved to a set of Smart Strings to set toe. They can be a little more accurate but require more setup time than required when using the toe plates and laser level.
If you really want a good setup get a Digital Caster/Camber gauge that can be magnetically attached to the hub, a set of hub stands (http://www.bbxracing.com/product_inf...products_id=69 ) and the Smart Strings.
Bill
In the front it doesn't matter as much whether one tire is toed in more than the other since the steering wheel will just turn to center the toe from side to side. The only issue with that is how much can it turn before the AH gets messed up due to too large of a steering angle being read by the EBCM when the car is being driven straight down the road. The solution to that problem is to use the laser to shoot from the front to the rear and to get the side to side measurements close to equal. You are doing this measurement over the distance of the car's wheel base so differences of 1/8 in from side to side are very small differences at the wheels.
I changed this process slightly by inserting the tape measure into the center of the hub or onto the rear axle stub before using the laser level.
If you have a caster/camber gauge, some metal plates with grease between them to set under the wheels, toe plates, a laser level, a 20 inch long rule and a jack stand that can be used to tape the rule to you can pretty much do a one person toe setting while at the track.
Recently I moved to a set of Smart Strings to set toe. They can be a little more accurate but require more setup time than required when using the toe plates and laser level.
If you really want a good setup get a Digital Caster/Camber gauge that can be magnetically attached to the hub, a set of hub stands (http://www.bbxracing.com/product_inf...products_id=69 ) and the Smart Strings.
Bill
Last edited by Bill Dearborn; 07-05-2015 at 04:47 PM.
07-05-2015, 08:53 PM
#4
Instructor
Thread Starter
There are several ways to do that. One was shown to me by Lou G while at an event at the Glen. He used a toe gauge that was made out of rectangular tubing. It looked like a 3 sided box. The long end was long enough to stretch across the spread of the rear wheels plus a couple of inches and the other two ends were about 12 inches long. One had a flat plate extending from the far end that was used to touch the rim, the other had a similar plate but was marked so you could read a tape measure placed on the rim and stretched across the top of the gauge. This gave total toe. Then he used a Sears 24 inch digital laser level place along the side of the rear tire to shoot a laser forward to the front wheel well. A helper had a tape measure inserted between the front spokes and touching the frame around the spot the Z06 brake duct mounting bolt is located. The assistant read the location of the laser beam on the tape measure and they then checked the other side of the car to see if they got close to the same measurement. This allowed them to set rear toe and thrust angle so the tires were almost exactly toed in the same amount.
In the front it doesn't matter as much whether one tire is toed in more than the other since the steering wheel will just turn to center the toe from side to side. The only issue with that is how much can it turn before the AH gets messed up due to too large of a steering angle being read by the EBCM when the car is being driven straight down the road. The solution to that problem is to use the laser to shoot from the front to the rear and to get the side to side measurements close to equal. You are doing this measurement over the distance of the car's wheel base so differences of 1/8 in from side to side are very small differences at the wheels.
I changed this process slightly by inserting the tape measure into the center of the hub or onto the rear axle stub before using the laser level.
If you have a caster/camber gauge, some metal plates with grease between them to set under the wheels, toe plates, a laser level, a 20 inch long rule and a jack stand that can be used to tape the rule to you can pretty much do a one person toe setting while at the track.
Recently I moved to a set of Smart Strings to set toe. They can be a little more accurate but require more setup time than required when using the toe plates and laser level.
If you really want a good setup get a Digital Caster/Camber gauge that can be magnetically attached to the hub, a set of hub stands (http://www.bbxracing.com/product_inf...products_id=69 ) and the Smart Strings.
Bill
In the front it doesn't matter as much whether one tire is toed in more than the other since the steering wheel will just turn to center the toe from side to side. The only issue with that is how much can it turn before the AH gets messed up due to too large of a steering angle being read by the EBCM when the car is being driven straight down the road. The solution to that problem is to use the laser to shoot from the front to the rear and to get the side to side measurements close to equal. You are doing this measurement over the distance of the car's wheel base so differences of 1/8 in from side to side are very small differences at the wheels.
I changed this process slightly by inserting the tape measure into the center of the hub or onto the rear axle stub before using the laser level.
If you have a caster/camber gauge, some metal plates with grease between them to set under the wheels, toe plates, a laser level, a 20 inch long rule and a jack stand that can be used to tape the rule to you can pretty much do a one person toe setting while at the track.
Recently I moved to a set of Smart Strings to set toe. They can be a little more accurate but require more setup time than required when using the toe plates and laser level.
If you really want a good setup get a Digital Caster/Camber gauge that can be magnetically attached to the hub, a set of hub stands (http://www.bbxracing.com/product_inf...products_id=69 ) and the Smart Strings.
Bill
Last edited by miracle_whip4130; 07-05-2015 at 08:57 PM.
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vmaxpwc (10-22-2015)
07-05-2015, 09:03 PM
#5
Instructor
Thread Starter
Also, is it generally accepted to be accurate to measure camber by laying the level across the wheel vertically? Obviously this will result in the level actually contacting the outside sidewall of the tire, instead of the wheel, which seems like it may be less accurate, due to tire manufacturing tolerances. Also, you have to avoid the bulge at the bottom of the tire, near the contact patch. I'm thinking about just cutting a section of square tubing down that would fit across the face of my wheels to space the level out away from the tire instead.....
07-06-2015, 12:19 AM
#6
Melting Slicks
Pro Mechanic
Member Since: Nov 2013
Location: Ex DPRK, now just N of Medford, OR
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Many (most?) pro teams use strings for toe (quick and dirty F adjustment with toe plates), and smart camber or similar for camber/caster. Wheel runout is the error factor in each. Make sure your rims are straight, or roll the car 180 degrees at the wheel and average the readings. With the right procedure you establish the vehicle centerline from the position of the wheels, same as a modern shop alignment machine.
Finding the car's absolute center line might be interesting (measure from the control arm mounting points... measuring from the ball joints would mask a bent control arm). You could probably adjust for it with a combination of shims at the upper control arms and eccentric adjustment at the lower... but is it actually important enough to do?
Finding the car's absolute center line might be interesting (measure from the control arm mounting points... measuring from the ball joints would mask a bent control arm). You could probably adjust for it with a combination of shims at the upper control arms and eccentric adjustment at the lower... but is it actually important enough to do?
07-07-2015, 10:35 PM
#9
Instructor
Thread Starter
07-08-2015, 03:22 PM
#10
Race Director
Also, is it generally accepted to be accurate to measure camber by laying the level across the wheel vertically? Obviously this will result in the level actually contacting the outside sidewall of the tire, instead of the wheel, which seems like it may be less accurate, due to tire manufacturing tolerances. Also, you have to avoid the bulge at the bottom of the tire, near the contact patch. I'm thinking about just cutting a section of square tubing down that would fit across the face of my wheels to space the level out away from the tire instead.....
07-08-2015, 04:14 PM
#11
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Also, is it generally accepted to be accurate to measure camber by laying the level across the wheel vertically? Obviously this will result in the level actually contacting the outside sidewall of the tire, instead of the wheel, which seems like it may be less accurate, due to tire manufacturing tolerances. Also, you have to avoid the bulge at the bottom of the tire, near the contact patch. I'm thinking about just cutting a section of square tubing down that would fit across the face of my wheels to space the level out away from the tire instead.....
When LG set my rear alignment they had their GT2 race car in the next garage bay and adjusted his ZR1 so he could give Customer's rides around the track. His team used the Sears Level against the tires to set the camber/caster. To measure caster you need to turn the steering wheel one half turn left and right to get the correct angle.
Wheel alignment's aren't all that accurate. You can set them precisely, drive around the block and come back and the readings will not be the same. They will be close but not the same so there is a certain point where you say that's close enough.
Bill
Last edited by Bill Dearborn; 07-08-2015 at 04:20 PM.
07-08-2015, 04:30 PM
#12
Burning Brakes
I thought about this when deciding my alignment methods and ended up with rectangle string setup... but I think parallelogram works also. If each of the opposing sides equal and you measure equal distance from hubs between each side (front and rear do NOT need to equal) you are centered... at least in my thinking.
It was a little difficult setting up my string mechanism measuring equal lengths and attaching the strings... used 2 aluminum electrical conduits. Actually strong fishing line worked best but retains kinks when stored. There's a few options at home depot I may try in the future.
It was a little difficult setting up my string mechanism measuring equal lengths and attaching the strings... used 2 aluminum electrical conduits. Actually strong fishing line worked best but retains kinks when stored. There's a few options at home depot I may try in the future.
07-08-2015, 06:19 PM
#13
I'll have to dig up a photo of the tools being used, but in the other thread I mentioned I was working on tooling to simplify setting up strings a while back. I finished it some time ago and have used it. Makes the job much easier. I absolutely hate smart strings only because of how time consuming they are to setup. They are nearly impossible to attach to the front of a corvette with enough stability to get accurate measurements. Anyway, that led me to build a reference system that makes the job stupid simple. The beginnings of the tooling can be seen in the other thread.