Silly alignment question..
10-07-2016, 02:02 PM
#1
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Silly alignment question..
Schedules being as they are, Im not able to do one thing before the other..easily..
So..if I were to lower the front of my car 1/2" -after- an alignment, how much toe should I compensate for ahead of time?
Alternatively, I could hang my lardbutt from the front, on the rack..and extrapolate from there. *heh*
So..if I were to lower the front of my car 1/2" -after- an alignment, how much toe should I compensate for ahead of time?
Alternatively, I could hang my lardbutt from the front, on the rack..and extrapolate from there. *heh*
10-07-2016, 02:39 PM
#2
I wouldn't do it. Adjusting the ride height is not hard, but often requires multiple adjustments and settling before you get everything right. Get the ride height dialed in prior or pay the shop to adjust and align.
Just my 2 cents
Just my 2 cents
10-07-2016, 02:58 PM
#3
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Thread Starter
Ya..the -1- guy I trust at this point, only has 830a tomorrow open..hmm..
Im not looing for exact lowering, just I know im far too high in front, was gonna come down about 5 turns, which should be 10mm'ish.
Im not looing for exact lowering, just I know im far too high in front, was gonna come down about 5 turns, which should be 10mm'ish.
10-07-2016, 07:28 PM
#4
Chronic Tool Dropper
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There's a multiplication factor for the length of the LCA, so changing the ring 10mm on the shock tube doesn't equate with a 10mm change in ride height.
The amount of toe change to expect is different depending on how high the car is when you start. For illustration, look at how "level" the LCA is now, along with how "level" the tie rod is now, and see that a car that's already low will see a lot more toe change per mm of height adjustment than a car with level pieces will see. Were it mine, and perhaps presuming that the car is headed south next weekend, I'd add an extra 15 mins (one quarter of a degree) to the total toe, then recheck after the car has settled.
Keeping in mind that wheel offsets affect what you'll want for toe settings. the original offsets cause the steering to toe in with wear, while zero or positive scrub radius (at around 55mm offsets) will cause the steering to toe-out with wear. If you have less than stellar steering and suspension bits, and have front wheels with 55mm offsets or less, crank in some extra toe-in just to account for the wear and the forces on the steering. How much? [grabs the dice and prepares to throw them....]
Put stops or blocks in front of the middle of the tires on both sides, roll the car hard against the stops and set the brake with the pressure on the steering. Now take a toe measurement. You'll be impressed with how much it changes vs the tires sitting free on the slip plates.
---
what was your question again?
The amount of toe change to expect is different depending on how high the car is when you start. For illustration, look at how "level" the LCA is now, along with how "level" the tie rod is now, and see that a car that's already low will see a lot more toe change per mm of height adjustment than a car with level pieces will see. Were it mine, and perhaps presuming that the car is headed south next weekend, I'd add an extra 15 mins (one quarter of a degree) to the total toe, then recheck after the car has settled.
Keeping in mind that wheel offsets affect what you'll want for toe settings. the original offsets cause the steering to toe in with wear, while zero or positive scrub radius (at around 55mm offsets) will cause the steering to toe-out with wear. If you have less than stellar steering and suspension bits, and have front wheels with 55mm offsets or less, crank in some extra toe-in just to account for the wear and the forces on the steering. How much? [grabs the dice and prepares to throw them....]
Put stops or blocks in front of the middle of the tires on both sides, roll the car hard against the stops and set the brake with the pressure on the steering. Now take a toe measurement. You'll be impressed with how much it changes vs the tires sitting free on the slip plates.
---
what was your question again?
10-08-2016, 11:39 AM
#6
Rennlist Member
Do not forget as you lower the front you increase the camber and this in turn causes the steering to toe out. I cannot relate the numbers to actual movement.
After changes of this kind I eyeball toe alignment by standing about 1m to the rear of the car, crouched down, out board of the wheels, then shut one eye and move my body inboard until the face of the wheel disappears. If this happens when your body is about 1 foot outboard of the rear wheel then I reckon toe is good enough to at least run around on until you make it to the alignment shop.
Did this recently and was amazed how close to acceptable I was when I did it for real on the Hunter. For camber I use a metal rule and a spirit level to test how much the top of the wheel sits in the fender. A few mm suffices until the alignment shop. Have never figured out a way to approximate caster but I generally turn it until it is about full whack knowing that gives a bit more than 5 degrees [on my car at least].
Just no substitute for the Hunter though.
Rgds
Fred
After changes of this kind I eyeball toe alignment by standing about 1m to the rear of the car, crouched down, out board of the wheels, then shut one eye and move my body inboard until the face of the wheel disappears. If this happens when your body is about 1 foot outboard of the rear wheel then I reckon toe is good enough to at least run around on until you make it to the alignment shop.
Did this recently and was amazed how close to acceptable I was when I did it for real on the Hunter. For camber I use a metal rule and a spirit level to test how much the top of the wheel sits in the fender. A few mm suffices until the alignment shop. Have never figured out a way to approximate caster but I generally turn it until it is about full whack knowing that gives a bit more than 5 degrees [on my car at least].
Just no substitute for the Hunter though.
Rgds
Fred
10-08-2016, 12:40 PM
#7
Chronic Tool Dropper
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My DIY alignment method for camber is similar to Fred's, except that I use a 5/32" (4mm) drill bit as a spacer at the top with a spirit level and my alignment tool frame at 17" spacing. Camber has a lot of influence on how the steering feels on center, very important that the two sides are the same regardless of what your preferred camber angle might be.
For caster I add a digital angle gauge to the alignment tool frame, and calculate caster the classic way based on wheels turned 30º in and out from center. I could use the digital angle gauge for camber, but instead use the spirit level to verify the digital gauge reading at wheels centered. Before the angle gauges, I was going with the full available caster adjustment and calling it good. Earl Gillstrom alerted me to the fact that the factory settings seem to be closer to the minimum end of the adjustment range. Once I had the angle gauges his observations were confirmed. For street cars, I'd start at the minimum available caster until you can get a real measurement and adjustment.
For toe, I'm still using the same laser fixtures, but the measurement method has been cleaned up a bit. In the original thread I was projecting the lasers straight ahead and taking tape-measure readings forward of the car. I've since adjusted that method to take one reading 43" forward of wheel centers, second measurement 43" aft of wheel centers, with tape marks on the floor rather than to points horizontal from wheel centers. For the factory-recommended 15' +5' (fifteen minutes toe-in with another 5 mins available tolerance, or one quarter of one degree to one third of one degree) toe-in, this works out to 3/8" (to 1/2") difference between the laser mark spacings, with front spacing smaller. I did the math for you, so no need to try and remember your high-school trigonometry.
Regardless, alignment is not rocket science and is something one can do themselves with a few assembled tools and fixtures, and a working floor with no side-to-side pitch. Jeff, Bill Ball has/had a handy laser setup that can be used to reset toe-in after your car has settled. Earl Gillstrom shares a method that uses strings taped to jackstands, and a pocket scale. Many many race cars have been set up using his method. Andrew Olson shared a video of his own method.
For caster I add a digital angle gauge to the alignment tool frame, and calculate caster the classic way based on wheels turned 30º in and out from center. I could use the digital angle gauge for camber, but instead use the spirit level to verify the digital gauge reading at wheels centered. Before the angle gauges, I was going with the full available caster adjustment and calling it good. Earl Gillstrom alerted me to the fact that the factory settings seem to be closer to the minimum end of the adjustment range. Once I had the angle gauges his observations were confirmed. For street cars, I'd start at the minimum available caster until you can get a real measurement and adjustment.
For toe, I'm still using the same laser fixtures, but the measurement method has been cleaned up a bit. In the original thread I was projecting the lasers straight ahead and taking tape-measure readings forward of the car. I've since adjusted that method to take one reading 43" forward of wheel centers, second measurement 43" aft of wheel centers, with tape marks on the floor rather than to points horizontal from wheel centers. For the factory-recommended 15' +5' (fifteen minutes toe-in with another 5 mins available tolerance, or one quarter of one degree to one third of one degree) toe-in, this works out to 3/8" (to 1/2") difference between the laser mark spacings, with front spacing smaller. I did the math for you, so no need to try and remember your high-school trigonometry.
Regardless, alignment is not rocket science and is something one can do themselves with a few assembled tools and fixtures, and a working floor with no side-to-side pitch. Jeff, Bill Ball has/had a handy laser setup that can be used to reset toe-in after your car has settled. Earl Gillstrom shares a method that uses strings taped to jackstands, and a pocket scale. Many many race cars have been set up using his method. Andrew Olson shared a video of his own method.
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10-08-2016, 01:13 PM
#8
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What exactly is being measured to compute caster?- this is the bit I have never really understood. I think I understand the virtual concept just not how it is measured. I suspect my grey matter is handicapping me in that I am probably anticipating something more complicated than it actually is. That I dial in max caster available saves my bacon when setting up the preliminary alignment pre-settlement.
When adjusting caster one moves the lower joint forwards for more and backwards for less [correct?] and in doing so this also impacts the camber slighly because of the radius change but how one "measures it" the lights just do not come on on that one -quite unusual for me.
Rgds
Fred
10-08-2016, 03:16 PM
#9
Pro
Re height adjustment: you could try my Tripod method: takes about an hour with a single set of adjustments and perfect result.
Think of the last time you tried to "even up" a 4-legged table by trimming just the right amount off one leg ... LOL. But a 3-legged table is dead simple because 3 legs always sit evenly on the ground.
So, with the 928, lift one end under its mid-point so those wheels are off the ground. (This forms the tripod).
Next, at the other end, adjust the shock collars to get the ride height measurement equal.
OK. One end is now done.
Next - lift the other end and repeat the process.
With one end lifted, the car can now pivot on the jack and allow adjustments to be made at the other end without interfering with each other.
Before you all scream "settling", I jack under a piece of solid timber under say, the front ball joints, to lift the front wheels off the ground without suspension sag. Similarly at the rear.
Turning the shock collars isn't always easy (dirt, corrosion), so ... I use a spring compressor to compress the spring "just enough - maybe 1mm or so" to take the load off the spring so the collar can be turned, then release it before I measure the ride height.
Warning: you will find this useful only after you're on your 5th or 6th time around the car chasing that last mirage-like tweak to get everything just right..
Think of the last time you tried to "even up" a 4-legged table by trimming just the right amount off one leg ... LOL. But a 3-legged table is dead simple because 3 legs always sit evenly on the ground.
So, with the 928, lift one end under its mid-point so those wheels are off the ground. (This forms the tripod).
Next, at the other end, adjust the shock collars to get the ride height measurement equal.
OK. One end is now done.
Next - lift the other end and repeat the process.
With one end lifted, the car can now pivot on the jack and allow adjustments to be made at the other end without interfering with each other.
Before you all scream "settling", I jack under a piece of solid timber under say, the front ball joints, to lift the front wheels off the ground without suspension sag. Similarly at the rear.
Turning the shock collars isn't always easy (dirt, corrosion), so ... I use a spring compressor to compress the spring "just enough - maybe 1mm or so" to take the load off the spring so the collar can be turned, then release it before I measure the ride height.
Warning: you will find this useful only after you're on your 5th or 6th time around the car chasing that last mirage-like tweak to get everything just right..
10-09-2016, 12:32 AM
#10
Chronic Tool Dropper
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Fred--
Caster is calculated from the camber readings at +30º and -30º steering angle. You can also do it from +20º and -20º with a different multiplier. I'd have to go find the instruction with the calculation, but it's part of an instruction that comes with a commercial racer's alignment kit. The factory 928 WSM supplement on alignment has the same calcs in it too.
The lasers I use have a "beam splitter" that generates a line fromt the single laser point. I point them straight down, and use a very hi-tech piece of paper with +/- 30º lines on it. Then turn the steering wheel until the laser line matches the line on the paper. Grocery-store plastic shopping bags get a spray of PAM vegetable oil baking spray and go under the tires as poor-mans slip plates. Between the two, all the benefits of real slip plates minus the cost.
The digital angle gauges I found are typically used to set up table-saw blades, so come from a woodworker's supply place. They come with magnets to stick easily to my laser fixture, and can be zero'd at any angle so the math of subtracting a negative angle from a positive one (to get the difference....) goes away. Just stick them on, turn the steering to 30º one side, zero the gauge, turn the wheel the other way, a simple multiplier and you have the caster angle.
Hunter guys and GM offer a white paper on alignment math, but its focus is more on the errors and trip-ups available, and all the detailed math they use in their aligment machines to make them a little more idiot-tolerant. Their goal of course is to be able to take anyone from toddler to rocket scientist and get the same results every time. I have it if you are having trouble getting to sleep.
Meanwhile, the SmartCamber Manual is attached. It's a much more practical guide.
The fixtures I made have a 24" length of 2" aluminum extruded box tube about .250" wall, and a couple 6" long by 1.5" aluminum angle pieces attached as legs of an "H", with spacing on the box tube equal to stated wheel diameter. This lets the edges of those angle pieces sit in the face of the rim edge just inside the tire. the box tube then parallel with the rim face.
I mounted a couple laser levels to the face of the box tube, then spent a little time "calibrating" the two lasers to hit the same spot when mounted the same way on the same wheel. I used a very high-tech 1/4-20 bolt through the box, threaded into the bottom of the laser level, with a wave-washer under the head to provide tension during the calibration process. Then just tighten the bolt to secure it all. Less than $20 in materials, plus the laser levels and the angle gauges. I use a cheap 24" carpenter's level, a tape measure, a bit of masking tape so I can make marks where the laser hits.
There's a "DIY Alignment" thread from several years ago that has some pics and diagrams of the fixtures, but the toe measuring method has since been streamlined.
Caster is calculated from the camber readings at +30º and -30º steering angle. You can also do it from +20º and -20º with a different multiplier. I'd have to go find the instruction with the calculation, but it's part of an instruction that comes with a commercial racer's alignment kit. The factory 928 WSM supplement on alignment has the same calcs in it too.
The lasers I use have a "beam splitter" that generates a line fromt the single laser point. I point them straight down, and use a very hi-tech piece of paper with +/- 30º lines on it. Then turn the steering wheel until the laser line matches the line on the paper. Grocery-store plastic shopping bags get a spray of PAM vegetable oil baking spray and go under the tires as poor-mans slip plates. Between the two, all the benefits of real slip plates minus the cost.
The digital angle gauges I found are typically used to set up table-saw blades, so come from a woodworker's supply place. They come with magnets to stick easily to my laser fixture, and can be zero'd at any angle so the math of subtracting a negative angle from a positive one (to get the difference....) goes away. Just stick them on, turn the steering to 30º one side, zero the gauge, turn the wheel the other way, a simple multiplier and you have the caster angle.
Hunter guys and GM offer a white paper on alignment math, but its focus is more on the errors and trip-ups available, and all the detailed math they use in their aligment machines to make them a little more idiot-tolerant. Their goal of course is to be able to take anyone from toddler to rocket scientist and get the same results every time. I have it if you are having trouble getting to sleep.
Meanwhile, the SmartCamber Manual is attached. It's a much more practical guide.
The fixtures I made have a 24" length of 2" aluminum extruded box tube about .250" wall, and a couple 6" long by 1.5" aluminum angle pieces attached as legs of an "H", with spacing on the box tube equal to stated wheel diameter. This lets the edges of those angle pieces sit in the face of the rim edge just inside the tire. the box tube then parallel with the rim face.
I mounted a couple laser levels to the face of the box tube, then spent a little time "calibrating" the two lasers to hit the same spot when mounted the same way on the same wheel. I used a very high-tech 1/4-20 bolt through the box, threaded into the bottom of the laser level, with a wave-washer under the head to provide tension during the calibration process. Then just tighten the bolt to secure it all. Less than $20 in materials, plus the laser levels and the angle gauges. I use a cheap 24" carpenter's level, a tape measure, a bit of masking tape so I can make marks where the laser hits.
There's a "DIY Alignment" thread from several years ago that has some pics and diagrams of the fixtures, but the toe measuring method has since been streamlined.
10-09-2016, 04:05 AM
#11
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Fred--
Caster is calculated from the camber readings at +30º and -30º steering angle. You can also do it from +20º and -20º with a different multiplier. I'd have to go find the instruction with the calculation, but it's part of an instruction that comes with a commercial racer's alignment kit. The factory 928 WSM supplement on alignment has the same calcs in it too.
.
Caster is calculated from the camber readings at +30º and -30º steering angle. You can also do it from +20º and -20º with a different multiplier. I'd have to go find the instruction with the calculation, but it's part of an instruction that comes with a commercial racer's alignment kit. The factory 928 WSM supplement on alignment has the same calcs in it too.
.
Thanks for the input. I guess that one of these days I might grasp it. I know they do measurements at different lock angles but exactly what they measure is the bit that baffles me some somewhat. I guess it's one of those concepts you either get it or [in my case] you do not- but getting closer!
Rgds
Fred
10-09-2016, 05:03 PM
#12
Chronic Tool Dropper
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Fred--
Caster angle is figured from the differences in measured camber at the two opposite steering angles. Read some of SmartCamber tool manual and it will make sense to you. I duplicated the functions of their tool by adding the digital angle gauges to my laser fixtures. A pair of my laser and camber angle fixtures, and a pocket scale and tape measure is all you need to do your own alignments. Oh, and patience, as the settings and adjustments are quite interactive. Three times through and all is well and pointing in the right direction.
The basic fixture with the laser-level mounted on it. Rotate so the level is vertical, added the digital angle guage for reading camber since this pic was taken:
Caster angle is figured from the differences in measured camber at the two opposite steering angles. Read some of SmartCamber tool manual and it will make sense to you. I duplicated the functions of their tool by adding the digital angle gauges to my laser fixtures. A pair of my laser and camber angle fixtures, and a pocket scale and tape measure is all you need to do your own alignments. Oh, and patience, as the settings and adjustments are quite interactive. Three times through and all is well and pointing in the right direction.
The basic fixture with the laser-level mounted on it. Rotate so the level is vertical, added the digital angle guage for reading camber since this pic was taken:
10-11-2016, 10:44 AM
#13
Rennlist Member
Bob,
Seems we have the same laser levels and very similar approach albeit I use my kit to get me to the Hunter machine. I did actually calculate the gradient needed for various camber levels and my intent on the toe was to use the lasers [one each side] to project onto a wall and thus measure total toe. My plans were scuppered previously as I did not have a wall at right angles- now I do in my garage so will attempt this when I replace the upper A arms shortly.
I do not think I would sleep easy relying on this approach and not using the Hunter but your kit is a bit more sophisticated than mine at the moment. I reckon one could easily make a slip plate using two sheets of thin aluminiu cladding material with a bit of grease in the sandwich.
The caster approach is interesting- I suspect what I am trying to understand is the mathematics of the calculation.
Regards
Fred
Seems we have the same laser levels and very similar approach albeit I use my kit to get me to the Hunter machine. I did actually calculate the gradient needed for various camber levels and my intent on the toe was to use the lasers [one each side] to project onto a wall and thus measure total toe. My plans were scuppered previously as I did not have a wall at right angles- now I do in my garage so will attempt this when I replace the upper A arms shortly.
I do not think I would sleep easy relying on this approach and not using the Hunter but your kit is a bit more sophisticated than mine at the moment. I reckon one could easily make a slip plate using two sheets of thin aluminiu cladding material with a bit of grease in the sandwich.
The caster approach is interesting- I suspect what I am trying to understand is the mathematics of the calculation.
Regards
Fred
10-11-2016, 04:03 PM
#14
Chronic Tool Dropper
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Fred--
I started my quest thinking I'd project onto a wall, but the toe measurement requires the "difference" between a couple readings/distances to get it to work. Lots of math on the fly, plus as you state the car needs to be perfectly square to the wall.
My current recommended method has masking tape tabs with lines on the floor 43" in front of and behind each wheel center, laterally located so the laser beam hits them from the wheel faces. On my car, my wheels and fixtures, this is about 72" apart side to side, but yours will be different with different wheels and fixture construction.
Mount and then rotate the laser fixture on each wheel so the beam lands on the front marks, take a reading with the tape measure of distance between laser impacts. Write that distance down. Now rotate the laser fixtures so the beams hit the rear tape marks, and again measure the spacing with the tape measure. Subtract the front spacing distance from the rear spacing difference. Each 1/8" of difference equals 5 minutes (one twelfth of one degree) of toe angle. The factory spec is for 15 minutes, plus five minutes of tolerance. So your target is 3/8 to 1/2" of difference, front points closer together than the rears.
If you make just one fixture with laser, you can just put it on one wheel, and make pencil marks on the tape tabs front and rear of the wheel, then move to the other side and do the same. Use the tape measure to find the distances between the marks, math is the same.
Note also that with just one fixture, there's no worries about making the two fixtures the same. So long as you don't flex the fixtures, you could make them out of wood instead of the metal tubing. So long as the readings and relationships stay the same at all four shots, all we are worried about is consistency.
Bill Ball and I did a demo of our DIY alignment tools and methods at a Sharktoberfest meeting a long while ago. We'd been collaborating some on line, and he came up with a T-shaped fixture rather than the H that I made. The foot on the single leg was movable for different diameter wheels, and he used materials from a home center rather than what I found at the handy local metal supply store. His method then had him shooting horizontally at movable "target" panels to the front and rear of the car, measuring and then calculating toe angles from those different measurements.
My goal was/is to simplify the process, eliminating need for a calculator and the trigonometry so that a normal person could do this stuff easily at home on the garage floor, with a tape measure. The most complex part is subtracting the fractions in the tape measure readings. No need for a remedial math class, just simple addition and subtraction.
I started my quest thinking I'd project onto a wall, but the toe measurement requires the "difference" between a couple readings/distances to get it to work. Lots of math on the fly, plus as you state the car needs to be perfectly square to the wall.
My current recommended method has masking tape tabs with lines on the floor 43" in front of and behind each wheel center, laterally located so the laser beam hits them from the wheel faces. On my car, my wheels and fixtures, this is about 72" apart side to side, but yours will be different with different wheels and fixture construction.
Mount and then rotate the laser fixture on each wheel so the beam lands on the front marks, take a reading with the tape measure of distance between laser impacts. Write that distance down. Now rotate the laser fixtures so the beams hit the rear tape marks, and again measure the spacing with the tape measure. Subtract the front spacing distance from the rear spacing difference. Each 1/8" of difference equals 5 minutes (one twelfth of one degree) of toe angle. The factory spec is for 15 minutes, plus five minutes of tolerance. So your target is 3/8 to 1/2" of difference, front points closer together than the rears.
If you make just one fixture with laser, you can just put it on one wheel, and make pencil marks on the tape tabs front and rear of the wheel, then move to the other side and do the same. Use the tape measure to find the distances between the marks, math is the same.
Note also that with just one fixture, there's no worries about making the two fixtures the same. So long as you don't flex the fixtures, you could make them out of wood instead of the metal tubing. So long as the readings and relationships stay the same at all four shots, all we are worried about is consistency.
Bill Ball and I did a demo of our DIY alignment tools and methods at a Sharktoberfest meeting a long while ago. We'd been collaborating some on line, and he came up with a T-shaped fixture rather than the H that I made. The foot on the single leg was movable for different diameter wheels, and he used materials from a home center rather than what I found at the handy local metal supply store. His method then had him shooting horizontally at movable "target" panels to the front and rear of the car, measuring and then calculating toe angles from those different measurements.
My goal was/is to simplify the process, eliminating need for a calculator and the trigonometry so that a normal person could do this stuff easily at home on the garage floor, with a tape measure. The most complex part is subtracting the fractions in the tape measure readings. No need for a remedial math class, just simple addition and subtraction.