DIY wheel alignment
#1
Team Owner
Thread Starter
DIY wheel alignment
I'm gathering stuff to try my hand at DIY alignment. So far have the gauge Wixey WR300 Type 1, CH47960-10 rear caster bracket. Made turn plates out of 2 12x12 floor tiles with talcum powder between. A 22" piece of 1/2" square tubing to fit across wheel. The face on the Z51 wheel is complete flat so no stand-off needed. I am going to make a couple of toe-plates.
The question:
I have no problem measuring camber front and rear. I get good repeatable readings. What about caster? I haven't tried yet.
So from what I have read:
Turn wheel 20 degrees (or some other # as long as they are the same) out, zero gauge, turn to 20 degrees in, reading is caster angle.
The plan is to set up front and rear about - 1.0. Front caster around +8.0, rear about +0.8. Front and rear toe 0.
I noticed in the photos that there appears to be a little oblong in the control arm mounting holes. Do y'all think I can get any caster adjustment by loosening the bolts and knocking the tops all the way back and the bottoms all the way forward or is that a waste of time?
The question:
I have no problem measuring camber front and rear. I get good repeatable readings. What about caster? I haven't tried yet.
So from what I have read:
Turn wheel 20 degrees (or some other # as long as they are the same) out, zero gauge, turn to 20 degrees in, reading is caster angle.
The plan is to set up front and rear about - 1.0. Front caster around +8.0, rear about +0.8. Front and rear toe 0.
I noticed in the photos that there appears to be a little oblong in the control arm mounting holes. Do y'all think I can get any caster adjustment by loosening the bolts and knocking the tops all the way back and the bottoms all the way forward or is that a waste of time?
#2
Team Owner
Thread Starter
Having dreams about alignment, up at 3 AM. Anyway lots of BS out there to sift through.
Checking camber is pretty straight forward read directly from angle gauge.
Caster is a different story. You see the old school bubble caster/camber gauges. Turn the wheel to right 20 degrees then to left 20 degrees, etc, etc. There is lots built into the guage. For one thing it only works for 20 degrees.
I you take a look at the front suspension imagine it is a gokart with old fashioned kingpin solid axle front end. If the kingpin was vertical, 90 degrees from horizontal front to rear and side to side, when the spindle rotated on the kingpin there would be no change in camber when the wheels are turned side to side. Now imagine kingpin angle slanted back 10 degrees. When the wheel is pointed straight ahead there would be 0 camber. Imagine that the wheel can be turned 90 degrees. Let's say it is the outside wheel, 90 degrees to the left would now give you 10 degrees of negative camber. Turn it 90 degrees to the right would give you 10 degrees positive camber. If you had a car where the wheels could be turned 90 degrees you could measure caster directly by measuring the difference in camber angle between wheels straight ahead and turned toward the middle of the car.
This is not possible on most/all cars. You can only measure a portion of the arc. The camber changes from 0 to full caster value from 0 to +90. The bigger the angle the more accurate the measurement. Unfortunately it ain't linear. The value turns out to be the sin x angle. On our gokart with +10 degrees caster I turn the right wheel 90 to the right and get a reading of +10 degrees. If I only turn it 20 degrees I will get a reading of 3.42 degrees (10 x sin 20). I can double the accuracy by going 20 degrees both sides of zero so that would be 3.42 x 2 = 6.84. Sin of 40 degrees give you 6.43, not the same. A 10 degree caster angle give me a reading of 6.84 degrees. To correct you need to multiply by inverse of 6.84/10 or 1.46.
So if you are trying to measure caster with a conventional angle gauge turn wheel to right 20 degrees zero gauge. Turn wheel to left 20 degrees and measure angle. Multiply by 1.46 to get caster. If you use 15 degrees left and right the correction factor will be 1.93, 25 degrees left and right 1.18.
Checking camber is pretty straight forward read directly from angle gauge.
Caster is a different story. You see the old school bubble caster/camber gauges. Turn the wheel to right 20 degrees then to left 20 degrees, etc, etc. There is lots built into the guage. For one thing it only works for 20 degrees.
I you take a look at the front suspension imagine it is a gokart with old fashioned kingpin solid axle front end. If the kingpin was vertical, 90 degrees from horizontal front to rear and side to side, when the spindle rotated on the kingpin there would be no change in camber when the wheels are turned side to side. Now imagine kingpin angle slanted back 10 degrees. When the wheel is pointed straight ahead there would be 0 camber. Imagine that the wheel can be turned 90 degrees. Let's say it is the outside wheel, 90 degrees to the left would now give you 10 degrees of negative camber. Turn it 90 degrees to the right would give you 10 degrees positive camber. If you had a car where the wheels could be turned 90 degrees you could measure caster directly by measuring the difference in camber angle between wheels straight ahead and turned toward the middle of the car.
This is not possible on most/all cars. You can only measure a portion of the arc. The camber changes from 0 to full caster value from 0 to +90. The bigger the angle the more accurate the measurement. Unfortunately it ain't linear. The value turns out to be the sin x angle. On our gokart with +10 degrees caster I turn the right wheel 90 to the right and get a reading of +10 degrees. If I only turn it 20 degrees I will get a reading of 3.42 degrees (10 x sin 20). I can double the accuracy by going 20 degrees both sides of zero so that would be 3.42 x 2 = 6.84. Sin of 40 degrees give you 6.43, not the same. A 10 degree caster angle give me a reading of 6.84 degrees. To correct you need to multiply by inverse of 6.84/10 or 1.46.
So if you are trying to measure caster with a conventional angle gauge turn wheel to right 20 degrees zero gauge. Turn wheel to left 20 degrees and measure angle. Multiply by 1.46 to get caster. If you use 15 degrees left and right the correction factor will be 1.93, 25 degrees left and right 1.18.
#3
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Look up David Farmer Racing's DIY alignment tips ( https://dl.dropboxusercontent.com/u/1634366/align.pdf ). He has a calculation you can use to measure caster based on how far you turn the steering wheel (1/2 or full turn). No need to try and determine if you have turned the wheels 15 or 20 degrees.
Bill
Bill
#4
Team Owner
Thread Starter
Looked at it. Probably not accurate on his car or any other.
Anyway got my bracket (CH47960-10) from local at cost + tax, $137 + 11.31.
Measured rear caster R + 0.3, L + 1.5
Front camber L - 0.3, R - 0.5.
Rear camber L - 0.7, R - 0.8.
Reading are consistant/repeatable. I am measure on a section of my drive that is almost level in both planes and am zeroing the gauge to compensate.
Anyway got my bracket (CH47960-10) from local at cost + tax, $137 + 11.31.
Measured rear caster R + 0.3, L + 1.5
Front camber L - 0.3, R - 0.5.
Rear camber L - 0.7, R - 0.8.
Reading are consistant/repeatable. I am measure on a section of my drive that is almost level in both planes and am zeroing the gauge to compensate.
#5
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Looked at it. Probably not accurate on his car or any other.
Anyway got my bracket (CH47960-10) from local at cost + tax, $137 + 11.31.
Measured rear caster R + 0.3, L + 1.5
Front camber L - 0.3, R - 0.5.
Rear camber L - 0.7, R - 0.8.
Reading are consistant/repeatable. I am measure on a section of my drive that is almost level in both planes and am zeroing the gauge to compensate.
Anyway got my bracket (CH47960-10) from local at cost + tax, $137 + 11.31.
Measured rear caster R + 0.3, L + 1.5
Front camber L - 0.3, R - 0.5.
Rear camber L - 0.7, R - 0.8.
Reading are consistant/repeatable. I am measure on a section of my drive that is almost level in both planes and am zeroing the gauge to compensate.
Bill
Last edited by Bill Dearborn; 12-16-2016 at 03:07 PM.
#6
Team Owner
Thread Starter
Why do you say it probably isn't accurate? David has been a racer and a member of this forum for as long as I have been a member. He used to run in the SCCA World Challenge series with his C5 competing against people like Lou G. He has been providing alignment advice and doing alignments for other people for as long as I have known of him. I haven't heard of any complaints during that time. I don't imagine GM has changed the Corvette steering ratio from the C5/C6 16:1 ratio. No reason to change it.
Bill
Bill
I just finished measure the caster on mine using home brew turning plates made for 12 x 12 vinyl tile inscribed with 20 degree marks.
Measured 4.6 and 4.7 and calculated caster at 6.7 and 6.9. Sounds about right.
Last edited by juanvaldez; 12-16-2016 at 05:31 PM.
#7
Team Owner
Thread Starter
Bottom line:
My '16 Z51 after a year 14,000 miles measures:
Front camber
Right -0.1 degree
Left -0.2
Front caster
Right +6.9
Left +6.7
Rear camber
Right -0.5
Left -0.5
Rear caster
Right +0.4
Left -1.2
I want -1.0 camber front and rear
+8.0 caster front or as close as I can get
rear caster +0.8
My '16 Z51 after a year 14,000 miles measures:
Front camber
Right -0.1 degree
Left -0.2
Front caster
Right +6.9
Left +6.7
Rear camber
Right -0.5
Left -0.5
Rear caster
Right +0.4
Left -1.2
I want -1.0 camber front and rear
+8.0 caster front or as close as I can get
rear caster +0.8
#8
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Couple of reasons. I am more of a math guy than a car guy. I figured out the math and it didn't fit his method. To measure the caster indirectly you need to measure the arc from straight ahead to some angle, say 20 degrees. The change in camber divided by sin of 20 will give you caster. I you go 20 left and 20 right you will double the value. I said it probably isn't accurate. He might know something I don't know. Things that can throw off the reading, more than 20 degrees will give high reading, less low readings. You can use any degree turn but the adjustment must match. Any time you hear the angle doesn't really matter as long as it is the same left and right, that is pure horse hockey.
I just finished measure the caster on mine using home brew turning plates made for 12 x 12 vinyl tile inscribed with 20 degree marks.
Measured 4.6 and 4.7 and calculated caster at 6.7 and 6.9. Sounds about right.
I just finished measure the caster on mine using home brew turning plates made for 12 x 12 vinyl tile inscribed with 20 degree marks.
Measured 4.6 and 4.7 and calculated caster at 6.7 and 6.9. Sounds about right.
Bill
#9
Team Owner
Thread Starter
So did you compare it to his method where you don't need turn plates but know how much to turn the steering wheel? As you say you need to know the angle and have a formula based on that angle. Don't you think if you know the steering ratio that you may actually have a damned good approximation of how many degrees the wheels turn when the steering wheel is turned a half revolution one way and then a full revolution from there to the other side? From there a person can develop a formula for the amount of degrees traveled by the front wheels with that sweep of the steering wheel. For the people who are mathematically challenged all they need to know is turn the steering wheel X amount (and easily observed) take the differences in camber readings and apply the formula. As far as they are concerned they don't need to know the angle even though the value of the angle is inherent in how far they turn the steering wheel.
Bill
Bill
#10
Team Owner
Thread Starter
Got my Longacre to plates off Amazon about $60. Works good.
Rear toe = + 1/16" (Toe in) Front toe = - 1/32 (Toe out)
Front camber
Right -0.1 degree
Left -0.2
Front caster
Right +6.9
Left +6.7
Front toe - 1/32" (toe out)
Rear camber
Right -0.5
Left -0.5
Rear caster
Right +0.4
Left -1.2
Rear toe + 1/16" (toe in)
Everything was in spec except for rear caster
I want -1.0 camber front and rear
+8.0 caster front or as close as I can get
rear caster +0.8 front a rear to about 0.
Rear toe = + 1/16" (Toe in) Front toe = - 1/32 (Toe out)
Front camber
Right -0.1 degree
Left -0.2
Front caster
Right +6.9
Left +6.7
Front toe - 1/32" (toe out)
Rear camber
Right -0.5
Left -0.5
Rear caster
Right +0.4
Left -1.2
Rear toe + 1/16" (toe in)
Everything was in spec except for rear caster
I want -1.0 camber front and rear
+8.0 caster front or as close as I can get
rear caster +0.8 front a rear to about 0.
#11
Team Owner
Thread Starter
The saga continues . . .
Talked to the local Firestone. They have a Hunter machine and a knowledgeable alignment guy. Bought lifetime alignment for $127.78
Went there on New Years Day and spent a couple hours screwin' with just rear using Bear machine and my CH47960-10 bracket and Wixey angle guage. The initial reading off his machine didn't match mine to begin with. Couldn't seem to get to get the -1.0 rear camber and +0.8 caster. Went home and removed 1 washer from each mounting point of upper control arms and tried to knock the mounting points as far toward the front of the car as far as possible since the hole in the mounting bracket is slightly larger than the bolt.
Talked to the local Firestone. They have a Hunter machine and a knowledgeable alignment guy. Bought lifetime alignment for $127.78
Went there on New Years Day and spent a couple hours screwin' with just rear using Bear machine and my CH47960-10 bracket and Wixey angle guage. The initial reading off his machine didn't match mine to begin with. Couldn't seem to get to get the -1.0 rear camber and +0.8 caster. Went home and removed 1 washer from each mounting point of upper control arms and tried to knock the mounting points as far toward the front of the car as far as possible since the hole in the mounting bracket is slightly larger than the bolt.
#13
Team Owner
Thread Starter
I think I finally figured out this caster thing. Moving both the front and rear cams doesn't change caster. Moving the front (of car) cam to push the arm out, make it longer increases caster.
I haven't been able to get the positive camber on the rear I want, around +0.8. As it stands I have -1.1 and -1.3 for camber with room to go both directions. I'm gonna move rear cam to the minimum position and try to get the caster I want by adjusting the front cam.
The holes in the upper A arm mounting points are slightly bigger than the bolts. When I removed the washers I tried to move all the brackets as far toward rear of the car as possible. Judging by the marks left by the bolt heads on the brackets, they did move slightly.
I haven't been able to get the positive camber on the rear I want, around +0.8. As it stands I have -1.1 and -1.3 for camber with room to go both directions. I'm gonna move rear cam to the minimum position and try to get the caster I want by adjusting the front cam.
The holes in the upper A arm mounting points are slightly bigger than the bolts. When I removed the washers I tried to move all the brackets as far toward rear of the car as possible. Judging by the marks left by the bolt heads on the brackets, they did move slightly.
#14
Team Owner
Thread Starter
Removing washers from upper control arms is pretty simple. You need to remove wheel. You need 15mm socket and torque wrench. After you get the bolts out the washers will fall out. There were two washers at each point on mine, remove one.
#15
Team Owner
Thread Starter
Adjusting camber and caster ain't bad. The nut/bolt heads are 21mm. The nut probably needs a deep socket. You will probably need a 21 wrench to get at the bolt head.
Increasing the forward (toward front of car) decreasing the rearward increases caster.
Increasing the forward (toward front of car) decreasing the rearward increases caster.
#16
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I think I finally figured out this caster thing. Moving both the front and rear cams doesn't change caster. Moving the front (of car) cam to push the arm out, make it longer increases caster. Yes, it will increase negative caster. Positive caster occurs when the upper ball joint is behind the lower ball joint. Once you go past the point where they are both on a Y Axis then caster increases in the negative direction. You have to make sure you know which way is positive and which way is negative and how the gauge is oriented will change the + or - display from the left side of the car to the right side of the car.
If you move the front cam on the lower control arm outward that pushes the lower ball joint towards the rear. That decreases positive caster while increasing negative camber. Adjusting the rear cam on the lower control arm outward pushes the lower ball joint forward increasing positive caster while still increasing negative camber.
Adding shims behind the front dog bone on the upper control arm will push the upper ball joint rearward increasing positive caster. However, adding shims also decreases negative camber.
I haven't been able to get the positive camber on the rear I want, around +0.8. As it stands I have -1.1 and -1.3 for camber with room to go both directions. I'm gonna move rear cam to the minimum position and try to get the caster I want by adjusting the front cam.
The holes in the upper A arm mounting points are slightly bigger than the bolts. When I removed the washers I tried to move all the brackets as far toward rear of the car as possible. Judging by the marks left by the bolt heads on the brackets, they did move slightly.
Moving the UCA Dog bones forward on the bolts will also decrease positive caster. You want the UCA as far to the rear as it can go with the front dog bone shimmed outward. Maximize your rear negative camber first, then adjust caster. Then as you adjust caster the negative camber will reduce. Afterwards set your toe in.
If you move the front cam on the lower control arm outward that pushes the lower ball joint towards the rear. That decreases positive caster while increasing negative camber. Adjusting the rear cam on the lower control arm outward pushes the lower ball joint forward increasing positive caster while still increasing negative camber.
Adding shims behind the front dog bone on the upper control arm will push the upper ball joint rearward increasing positive caster. However, adding shims also decreases negative camber.
I haven't been able to get the positive camber on the rear I want, around +0.8. As it stands I have -1.1 and -1.3 for camber with room to go both directions. I'm gonna move rear cam to the minimum position and try to get the caster I want by adjusting the front cam.
The holes in the upper A arm mounting points are slightly bigger than the bolts. When I removed the washers I tried to move all the brackets as far toward rear of the car as possible. Judging by the marks left by the bolt heads on the brackets, they did move slightly.
Moving the UCA Dog bones forward on the bolts will also decrease positive caster. You want the UCA as far to the rear as it can go with the front dog bone shimmed outward. Maximize your rear negative camber first, then adjust caster. Then as you adjust caster the negative camber will reduce. Afterwards set your toe in.
DO NOT Forget to check the level of his alignment rack. It may or may not be level. If isn't level his machine may be calibrated for that while your gauge isn't. That is one of the things the GM Rear Caster adjustment instructions point out is to check the level of the rack and zero the gauge before making any measurements.
Bill
Last edited by Bill Dearborn; 01-03-2017 at 01:30 PM.
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juanvaldez (01-03-2017)
#17
Team Owner
Thread Starter
I'm getting pretty close. Got - 1.0 negative camber on both sides rear by going minimum (shortest) on the front and about halfway on the rear. Maximum on the rear gave me too much negative camber all the way out. Both sides now have positive caster about 1.1 on one side but about 3.0 on the other. Toe is now way out about + 3/8.
#18
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I'm getting pretty close. Got - 1.0 negative camber on both sides rear by going minimum (shortest) on the front and about halfway on the rear. Maximum on the rear gave me too much negative camber all the way out. Both sides now have positive caster about 1.1 on one side but about 3.0 on the other. Toe is now way out about + 3/8.
Bill
#19
Pro
....Don't want to hijack this thread but since we have some alignment experts chiming in I have an alignment question for you guys...
The rear end of my car has been torn out 2 times to get the transmission out once for a TC replacement and the second time for a full transmission replacement. ( 2015 C7 Coupe)
When the tech reinstalled the rear end would he have needed to do a rear end alignment to have the rear wheel Caster in spec or would it go back together in spec if it was in spec when it was torn out ??????
Thanks.
The rear end of my car has been torn out 2 times to get the transmission out once for a TC replacement and the second time for a full transmission replacement. ( 2015 C7 Coupe)
When the tech reinstalled the rear end would he have needed to do a rear end alignment to have the rear wheel Caster in spec or would it go back together in spec if it was in spec when it was torn out ??????
Thanks.
#20
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....Don't want to hijack this thread but since we have some alignment experts chiming in I have an alignment question for you guys...
The rear end of my car has been torn out 2 times to get the transmission out once for a TC replacement and the second time for a full transmission replacement. ( 2015 C7 Coupe)
When the tech reinstalled the rear end would he have needed to do a rear end alignment to have the rear wheel Caster in spec or would it go back together in spec if it was in spec when it was torn out ??????
Thanks.
The rear end of my car has been torn out 2 times to get the transmission out once for a TC replacement and the second time for a full transmission replacement. ( 2015 C7 Coupe)
When the tech reinstalled the rear end would he have needed to do a rear end alignment to have the rear wheel Caster in spec or would it go back together in spec if it was in spec when it was torn out ??????
Thanks.
The odds of being able to get the rear caster set at any shop approach zero when you include independents shops in the mix. Independents will have even less info than the dealerships.
Bill
Last edited by Bill Dearborn; 01-09-2017 at 05:03 PM.
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767guy (01-09-2017)