DIY Toe-in Check
04-15-2007, 12:48 AM
#31
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well, we dont really know the hyp, but close enough. the correct calculator would be one that uses side 1 and side 2 to find the opposite angle. (angle we are discussing) however, with an angle of only .25 degrees, using the hyp or side 1, yeilds close to the same answer
Mk
Mk
Originally Posted by Ed Hughes
I posted the wrong calculator, this is the one I meant to post. You know the hyp. and one of the sides, so the angles will be calculated. Here's the right one:
http://www.1728.com/pythgorn.htm
http://www.1728.com/pythgorn.htm
04-15-2007, 12:52 AM
#32
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Good point about the accuracy of finding 1/16" . actaully we are looking for 1/8", and if you see this, which is pretty easy to detect, you got 1/16" of an inch on each side. however, if you need to get your measurement more accurate than .25 degrees or 15min, then the longer distances can help. HOWEVER, it also amplifies an problems with runout on your rim, or the laser set up. So, i guess i becomes a series of trade offs, until we open the check book and visit a Hunter Machine 
Originally Posted by dr bob
Mark's method includes 1/16" difference total for both sides, and that's the smallest graduation on most measuring tapes. Extending the measurement field out to 86" makes it possible to use bigger values that are more appropriate for the tape. 3/8-1/2 inch is easy for us blind guys. I suspect that the 1/16" could easily be lost in two pen-widths of marks on the floor.
For those of us who run the same wheels all the time, we can speed the process next time by recording the readings from the first alignment we do, then measuring at any distance to a surface perpendicular to the front of the car, like a garage door. Get the distance between the car and the door and the space in between the beams on the door as your standard, and you can always just put the car the same distance from any vertical surface and verify that the beams are still the same distance apart. Say you work on the car before you take off for Nevada, and that work includes raising the car. When you get there, pull up to a handy wall, correct distance from it like at home, shoot the wall and measure to varify that the toe hasn't changed since home. Adjust as necessary to match your good home spread and you are assured that your toe is once again correct.
Simple repeatability.
For those of us who run the same wheels all the time, we can speed the process next time by recording the readings from the first alignment we do, then measuring at any distance to a surface perpendicular to the front of the car, like a garage door. Get the distance between the car and the door and the space in between the beams on the door as your standard, and you can always just put the car the same distance from any vertical surface and verify that the beams are still the same distance apart. Say you work on the car before you take off for Nevada, and that work includes raising the car. When you get there, pull up to a handy wall, correct distance from it like at home, shoot the wall and measure to varify that the toe hasn't changed since home. Adjust as necessary to match your good home spread and you are assured that your toe is once again correct.
Simple repeatability.
04-15-2007, 01:31 PM
#33
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Originally Posted by dr bob
I obviously need to take more pictures, maybe some video, to help some of this make sense. (
He sure made it look easy. Ha ha...
04-15-2007, 04:43 PM
#34
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I borrowed a xl spreadsheet from a guy on Pelican to help calculate toe/camber. I'll share it for you guys. Hope you find it useful. Just fill in all the information boxes.
04-17-2007, 07:40 AM
#35
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Originally Posted by mark kibort
Good point about the accuracy of finding 1/16" . actaully we are looking for 1/8", and if you see this, which is pretty easy to detect, you got 1/16" of an inch on each side. however, if you need to get your measurement more accurate than .25 degrees or 15min, then the longer distances can help. HOWEVER, it also amplifies an problems with runout on your rim, or the laser set up. So, i guess i becomes a series of trade offs, until we open the check book and visit a Hunter Machine
Mark--
The total toe-in of 15 minutes means 1/16 inch total difference, not 1/16 inch for each wheel.
The longer distances definitely help with the accuracy, at least as far as being able to discern the beam vs the mark on the tape.
I spent a good bit of time figuring out a way to get the two lasers parallel, using a holding fixture and shooting target grids 45 feet away. I have them parallel within 1/16" at that distance, so that would work out to a really small error number at 86", about 1/6 of a sixteenth, right? The H-F lasers have a bit of 'bloom' in the pattern as you get that far away. I'm tempted to look for a better laser at some point, but for now these are fine.
On bent rims-- The Hunter machine lones up on the same surfaces we are using, whether it's using a level of the fixture holding the level. The fixture is shimmed square on a surface plate, so any irregular bend in the wheel shows up when you hang the fixture on. If the whole wheel is bent on the hub, you'll still end up with the correct toe-in twice in each wheel revolution, just like with the Hunter machine or any other method.
05-13-2007, 10:32 PM
#36
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Update--
I spent more than enough time (or so she said...) yesterday working on the whole alignment, rather than just the toe-in. The car was still driving funny with the toe set correctly, the outside edge of the tires was still scrubbing, so it was obvious that more was needed.
Loosely following the Earl Gilstrom method but adapted to the aluminum fixtures I'd fab'd, it is way too easy to set the camber just right. I started off using a bubble level against the fixture support angles, but ended up with the plumb bob and drill bit method to verify. Right side was way too much camber, like over 3x the WSM spec of 30' (thirty minutes) of angle. Left side was OK. Getting just the right adjustment is iterative, since tightening the nuts on the cams will change the readings slightly.
Once the camber was set correctly, the toe was way off again, so I rolled the car just a little until the lasers were pointing forward again, and reset the to-in. Test drive says it's OK but the wheel isn't centered. Hmmm, it's close but not perfect. So roll the car a little so the lasers are pointing directly backwards. Measure from the beams to the center cap on the rear wheel. Take the total of the right and left distances and divide that in half to get a target spacing for each side with the steering wheel centered. Re-center the wheel, then adjust the tie-rods on both sides until the beams are centered, with the same target distances between the caps and the beams on both sides. Roll the car to get the beams forward and verify that the toe-in is still right, and know now that the wheel is perfectly centered in the car when the car is going perfectly straight.
Now the good news for Bill, Mark, and others who might want to verify their settings on a more regular basis. Once you have determined that perfect distance between the rear wheel center cap and the beam on each side, you can go to that same distance at any time to restore your toe settings. Say you drive all the way to Battle Mountain with the car at somewhat normal height but want it lower for the ORR. Just make the adjustment to the spring perches, drive the car a little to settle it, then put the alignment fixtures on, facing the rear. Center the wheel, adjust to your perfect distance between the caps and beams, and your toe setting will be perfect. No carpenter's square, no tape on the floor, no tape measure, after that first initial alignment in the garage. All you'll need for later adjustments is a pocket scale to measure the cap-to-beam dimension, and the wrench for the tie-rod adjuster locknut. And maybe the wrench to turn the tie-rod adjusting sleeve. You'd only need to carry one laser fixture too, since it's fast moving it from side to side using my high-tech bungee-cord support system to hold it against the lip of the rim.
Oh yeah, the results of the work on the car-- It drives like new again, no scuffing or chattering in full-lock situations (like backing out of the garage). Having the wheels going in the right direction moved the comfort zone on my morning Angeles Crest Highway test drive up at least ten MPH, a very very noticeable improvement.
When I get around to installing and firing up the new animated Autocad program on my new workstation, I'll package a fabrication instruction for the brackets. More importantly, I'll describe the procedure I used to zero-in the two lasers so they are perfectly parallel on the brackets. That part took the most time to figure out, and is critical to the accuracy and repeatability of the readings. With the right instructions, they can be zeroed in minutes now instead of hours. Biggest time-eater in that will be waiting for the 5-minute epoxy to set up to hold the laser onto the square tubing.
I spent more than enough time (or so she said...) yesterday working on the whole alignment, rather than just the toe-in. The car was still driving funny with the toe set correctly, the outside edge of the tires was still scrubbing, so it was obvious that more was needed.
Loosely following the Earl Gilstrom method but adapted to the aluminum fixtures I'd fab'd, it is way too easy to set the camber just right. I started off using a bubble level against the fixture support angles, but ended up with the plumb bob and drill bit method to verify. Right side was way too much camber, like over 3x the WSM spec of 30' (thirty minutes) of angle. Left side was OK. Getting just the right adjustment is iterative, since tightening the nuts on the cams will change the readings slightly.
Once the camber was set correctly, the toe was way off again, so I rolled the car just a little until the lasers were pointing forward again, and reset the to-in. Test drive says it's OK but the wheel isn't centered. Hmmm, it's close but not perfect. So roll the car a little so the lasers are pointing directly backwards. Measure from the beams to the center cap on the rear wheel. Take the total of the right and left distances and divide that in half to get a target spacing for each side with the steering wheel centered. Re-center the wheel, then adjust the tie-rods on both sides until the beams are centered, with the same target distances between the caps and the beams on both sides. Roll the car to get the beams forward and verify that the toe-in is still right, and know now that the wheel is perfectly centered in the car when the car is going perfectly straight.
Now the good news for Bill, Mark, and others who might want to verify their settings on a more regular basis. Once you have determined that perfect distance between the rear wheel center cap and the beam on each side, you can go to that same distance at any time to restore your toe settings. Say you drive all the way to Battle Mountain with the car at somewhat normal height but want it lower for the ORR. Just make the adjustment to the spring perches, drive the car a little to settle it, then put the alignment fixtures on, facing the rear. Center the wheel, adjust to your perfect distance between the caps and beams, and your toe setting will be perfect. No carpenter's square, no tape on the floor, no tape measure, after that first initial alignment in the garage. All you'll need for later adjustments is a pocket scale to measure the cap-to-beam dimension, and the wrench for the tie-rod adjuster locknut. And maybe the wrench to turn the tie-rod adjusting sleeve. You'd only need to carry one laser fixture too, since it's fast moving it from side to side using my high-tech bungee-cord support system to hold it against the lip of the rim.
Oh yeah, the results of the work on the car-- It drives like new again, no scuffing or chattering in full-lock situations (like backing out of the garage). Having the wheels going in the right direction moved the comfort zone on my morning Angeles Crest Highway test drive up at least ten MPH, a very very noticeable improvement.
When I get around to installing and firing up the new animated Autocad program on my new workstation, I'll package a fabrication instruction for the brackets. More importantly, I'll describe the procedure I used to zero-in the two lasers so they are perfectly parallel on the brackets. That part took the most time to figure out, and is critical to the accuracy and repeatability of the readings. With the right instructions, they can be zeroed in minutes now instead of hours. Biggest time-eater in that will be waiting for the 5-minute epoxy to set up to hold the laser onto the square tubing.
11-04-2007, 11:21 AM
#38
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Hi Dr Bob,
Great thread - how important are the slip plates?
We found that doing the alignment without slip plates was very "hit & miss" and required a time consuming rolling back and forward of the car. Is it important to move the car back and forward with a high degree of accuracy in keeping everything where it is?
Lugging the slip plates around is a PITA.
Interested in your thoughts please?
Roger
Great thread - how important are the slip plates?
We found that doing the alignment without slip plates was very "hit & miss" and required a time consuming rolling back and forward of the car. Is it important to move the car back and forward with a high degree of accuracy in keeping everything where it is?
Lugging the slip plates around is a PITA.
Interested in your thoughts please?
Roger
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Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission?
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928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission?
George Layton March 2014928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
11-04-2007, 12:11 PM
#39
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There's an e-mail exchange goin on about this in the background.
Slip plates, more specifically turn plates, are required if you want to adjust caster. Slip plates are really handy when adjusting toe and camber, but not required. As you suggest, you can roll the car back and forth a few times to unload any adjustment stress that you've added, and remeasure to confirm that the adjustments are correct. The laser fixtures I made have levels in them, so it's easy to roll the car back to precisely where it was for the next measurement. Plates really speed up the process by eliminating the rolling back and forth, but are not required.
Spend some time with Earl Gilstrom's excellent alignment guide/info on his rennlsit website. The pieces I've added or adjusted from his recommendations are the laser fixtures to get away from the strings and pocket scales, in favor of a tape measure. I simplify the math for the toe adjustment by using a standard length for the trapezoid, but otherwise I'm pretty much following his instructions.
I may be going to the metal store in a week or three, and will be batching some of the tubing and angle pieces for the laser fixtures. I have no interest in turning this into a business, but may entertain requests for fixtures from regional focal points, folks like Roger, who are in a position to host clinics for groups. Remember we are still in the experimentation mode here. Trying to extend tire life some, and save DIY owners from some of that that extra expense. Plan right now is for four pairs of fixtures. Two are already allocated, two may be available.
Slip plates, more specifically turn plates, are required if you want to adjust caster. Slip plates are really handy when adjusting toe and camber, but not required. As you suggest, you can roll the car back and forth a few times to unload any adjustment stress that you've added, and remeasure to confirm that the adjustments are correct. The laser fixtures I made have levels in them, so it's easy to roll the car back to precisely where it was for the next measurement. Plates really speed up the process by eliminating the rolling back and forth, but are not required.
Spend some time with Earl Gilstrom's excellent alignment guide/info on his rennlsit website. The pieces I've added or adjusted from his recommendations are the laser fixtures to get away from the strings and pocket scales, in favor of a tape measure. I simplify the math for the toe adjustment by using a standard length for the trapezoid, but otherwise I'm pretty much following his instructions.
I may be going to the metal store in a week or three, and will be batching some of the tubing and angle pieces for the laser fixtures. I have no interest in turning this into a business, but may entertain requests for fixtures from regional focal points, folks like Roger, who are in a position to host clinics for groups. Remember we are still in the experimentation mode here. Trying to extend tire life some, and save DIY owners from some of that that extra expense. Plan right now is for four pairs of fixtures. Two are already allocated, two may be available.
11-04-2007, 01:26 PM
#40
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Thanks Bob,
So for the "one off" alignment the backward & forward exercise is OK.
Easier with slip plates if doing it more than once or twice.
Roger
So for the "one off" alignment the backward & forward exercise is OK.
Easier with slip plates if doing it more than once or twice.
Roger
