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You sir need to build some new control arms for these so called messed up C7's! I must say as bad as you say they are then why do they handle so dam well set up properly? Why can mediocre Z06 drivers hang on the track with those super high tech GT3's? You don't need to answer I just had to comment.
Now for my serious side:
In the middle of your post you gave a list of the numbers you wanted and commented we need 2.0 rear castor to get that? If I read it correctly, we have tested just that. In fact we even went to 2.5 rear castor. Frankly the car still felt great high and low load cornering. We have since gone back to 1.2 to 1.5. Also we do start out with -.5 degrees tow out in the rear with the big caster numbers. As load increases the rear toes back in fairly quickly. Our car has run some of its best times at the track with that set up. Do you think were going in the right direction with the big rear caster numbers? I Hope to get the time next spring to spend more time with that subject.
BTW, LG is waiting on the patent papers for pieces to get rid of the eccentrics. I hope they do by spring.
Mike Levitas here at DSCsport / TPCRacing . Dont be so alarmed at toe out that is only the static setting more important is the dynamic toe curve. the factory toe curve with the upright straight up and was fairly normal looking @ stock upright angle. It had close to .8mm toe in at 25mm travel under compression / the rebound curve was 1mm @25mm droop. the car in any situation acts like a short wheel base and does not put down power and is terrible in the rain wants to swap ends. so look at that curve as a slightly offset circle. I always refer to this as the toe circle its critical.
change the upright angle to .75 positive and you will find 1.3mm toe in @25mm travel under compression and .5mm toe out @25mm droop. The toe curve plotted out will look like and offset egg. Great power down huge stability from the long wheel base. now with this curve you have no issue toe out. the slightest compression puts the toe in and the mid corner grip is amazing. the next big update is to pull the stock shock controller and put in the dsc. Now you are no longer held to the passive tuning but the door is open to velocity tuning I run the rear dampers way softer now especially the low speed for added grip. with the stock upright angle your using the damper to hold up the chassis to limit wheel travel because the geometry . In racing Porsche we have never had the luxury of engine so chassis tuning is everything. Never close you eyes or mind to trying to find solutions thats how you win races.
Always try new setup changes and constantly tune your chassis at the track I try to never make a lap without gathering data and making more changes.
Have fun with the C7 its a great car the most fun in our stable for sure.
next week we will be releasing a new firmware for the DSC in the C7 it features a launch mode that tunes the chassis on the leave and allows you to change the chassis setting as the compressor comes on as a traction adder. stay tuned there is way more yet to come. Im having way to much fun with my C7 Z06
Originally Posted by Shaka
Never tow out at the rear.
Interesting info. that Mike has, but it is like putting lipstick on a pig. The problem lies in the poorly designed suspension geometry. I was the first to suggest that the C5 thru C7 has poorly designed geometry, a 2' +caster fix and possible ediff actuation problems here.
A few things: No tow out at the rear in any circumstances. Absurd.
At a glance, the negative camber gain from squat to droop is just plain awful. It's been that way since the C5. The inside wheel has increased negative camber in high G turns where the reverse is required. -camber gain in droop is unheard of. I won't even mention the front. The location of the upper control arm is simply wrong. It must be positive in droop at one G roll or at the very least, zero. Tons of grip is being lost on the inside tire and the outside tire reaches saturation prematurely because of it. The inside tires can't even handle the approx. 700 lb load each on a 1G turn because the friction circle evaporates because of no camber thrust and reduced contact patch. This is the major factor in the C7s unpredictable handling. 650 HP doesn't help. The sad thing is, is that is very easy to fix by relocating the upper control arm and steering rod.
This coupled with severe anti-squat geometry, major binding couples are generated, aggravating suspension compliance. It does have a damping effect on a spike LOAD transfer in launch and straight line activities, however, which is good at shift points for stability. LOAD and not weight xfer is determined by mass acceleration.
I want to see bump and dive tow-in to be at one degree minimum. I want to see .5 tow static. You will need at least 2' +caster to achieve that tow (CURVE)
Some questions for Mike: @.75 +caster gives -.5 tow out????
What steer migration (tow curve) do you get for droop and squat?
Tow out at the back is never a good thing in any circumstance.
Also, loose the eccentrics especially if you have slicks or high downforce. Tadge says they have them because they allow 3 minutes for alignment. Also a simple fix.
Another contributing factor in the sudden change in direction could be delays in the ediff actuation. When my normal Salisbury diff begins to open, I get violent directional changes to the right in low gear shifts. C6Z. It is then time to replace clutches.
Notice how the right rear wears faster than the left even when the diff is working right? Think about that one. Watch Steve McQueen in his Mustang with an open diff. Smoke off the left rear tire in reverse and smoke off the right tire in first. Why?
Each time you lift off with the ediff, it opens. Suspension unloads and cambers become more negative. Squat geometry forces cease. Stomp on it, and the instant asymmetric torque split and the instant negative camber change with an unloaded suspension and squat reversal forces, will turn the car. It will get worse with miles. Don't lift when shifting with the ediff.
Mikes solution only masques the real problem.
If you have the dimensions of the of the lower control arm, distance between lower control arms, upright dimensions including steer hard point, ball joint inclination and factory scrub radius, tire diameter and tread width, roll center, wheel base, total weight and CG location, my computer will fill in the rest properly. I'll add and subtract squat geometry (which Mike can control with the dampers,) to show binding and hysteresis. I'll estimate hysterein and hysteros values. A arms are obsolete in suspension design anyway but I don't know how to design a multilink system like Corvette's competitors have where you can seriously optimise the tire friction circle..
Note daylight under the inside tires.
Upper control arm is wrong.
Exaggeration but try to trend camber gains in turns to look like this.
Check that camber in droop. What were they thinking?
Loose these things.
Mike Levitas here at DSCsport / TPCRacing . Dont be so alarmed at toe out that is only the static setting more important is the dynamic toe curve. the factory toe curve with the upright straight up and was fairly normal looking @ stock upright angle. It had close to .8mm toe in at 25mm travel under compression / the rebound curve was 1mm @25mm droop. the car in any situation acts like a short wheel base and does not put down power and is terrible in the rain wants to swap ends. so look at that curve as a slightly offset circle. I always refer to this as the toe circle its critical.
change the upright angle to .75 positive and you will find 1.3mm toe in @25mm travel under compression and .5mm toe out @25mm droop. The toe curve plotted out will look like and offset egg. Great power down huge stability from the long wheel base. now with this curve you have no issue toe out. the slightest compression puts the toe in and the mid corner grip is amazing. the next big update is to pull the stock shock controller and put in the dsc. Now you are no longer held to the passive tuning but the door is open to velocity tuning I run the rear dampers way softer now especially the low speed for added grip. with the stock upright angle your using the damper to hold up the chassis to limit wheel travel because the geometry . In racing Porsche we have never had the luxury of engine so chassis tuning is everything. Never close you eyes or mind to trying to find solutions thats how you win races.
Always try new setup changes and constantly tune your chassis at the track I try to never make a lap without gathering data and making more changes.
Have fun with the C7 its a great car the most fun in our stable for sure.
next week we will be releasing a new firmware for the DSC in the C7 it features a launch mode that tunes the chassis on the leave and allows you to change the chassis setting as the compressor comes on as a traction adder. stay tuned there is way more yet to come. Im having way to much fun with my C7 Z06
Mike, Thanks for the information this is a ditto of many previous posts but one that always interest me. We set up customers Z06's for the track and I want to make sure they are getting the very latest.
Have you tried on the track or on the lift to see the toe curves with higher positive castors closer to 2.0? If toe in is at 1.3 mm @ 25 mm compression with the caster @ .75mm starting with a -.5 out then is toe in increased as Positive castor is increased? It is something we were planning to check in the spring. This leads to a good question what do you feel is enough or to much toe in at full compression? I plan to get a controller for our car but want to fully understand the suspension in stock form first. Most of our customer are staying closer to stock.
Mike Levitas here at DSCsport / TPCRacing . Dont be so alarmed at toe out that is only the static setting more important is the dynamic toe curve. the factory toe curve with the upright straight up and was fairly normal looking @ stock upright angle. It had close to .8mm toe in at 25mm travel under compression / the rebound curve was 1mm @25mm droop. the car in any situation acts like a short wheel base and does not put down power and is terrible in the rain wants to swap ends. so look at that curve as a slightly offset circle. I always refer to this as the toe circle its critical.
change the upright angle to .75 positive and you will find 1.3mm toe in @25mm travel under compression and .5mm toe out @25mm droop. The toe curve plotted out will look like and offset egg. Great power down huge stability from the long wheel base. now with this curve you have no issue toe out. the slightest compression puts the toe in and the mid corner grip is amazing. the next big update is to pull the stock shock controller and put in the dsc. Now you are no longer held to the passive tuning but the door is open to velocity tuning I run the rear dampers way softer now especially the low speed for added grip. with the stock upright angle your using the damper to hold up the chassis to limit wheel travel because the geometry . In racing Porsche we have never had the luxury of engine so chassis tuning is everything. Never close you eyes or mind to trying to find solutions thats how you win races.
Always try new setup changes and constantly tune your chassis at the track I try to never make a lap without gathering data and making more changes.
Have fun with the C7 its a great car the most fun in our stable for sure.
next week we will be releasing a new firmware for the DSC in the C7 it features a launch mode that tunes the chassis on the leave and allows you to change the chassis setting as the compressor comes on as a traction adder. stay tuned there is way more yet to come. Im having way to much fun with my C7 Z06
Howdy Mike. Happy new year. Take a look at this vid. Pay particular attention from 5:40 to 6:18. Then 6:41 to 7:05. "Too much oversteer" "Wild ride" etc. This after GM 'fixed' it. Then from 7:50. Check the camber of the inside rear of both cars in turns. http://www.corvetteblogger.com/2016/...t-laguna-seca/
This droop camber is easy to fix if you are a good fabricator. So much grip is being lost on the C7 because of the location of the upper A arms. Check the exit at the Karrosel at the Ring.
Send me the data I have requested in a previous post and I'll send you a fix for the C7's poor manors.
See my comments on the C7 chassis design some where in the forum. Nothing but praise but not for the reasons you would think. The long wheel base is magic otherwise the car would be uncontrollable as you eluded to.
You can srew around with adjustments all you want, but here is the problem. The front needs surgery also but we can live with it for now.
My 2002 430hp LS2 in my even better chassis. Poor aero but excellent mechanical grip Will beat any production car up to 130mph.
BMW M3 diff with roll understeer rear geometry with perfect manors. 4' +caster
Howdy Mike. Happy new year. Take a look at this vid. Pay particular attention from 5:40 to 6:18. Then 6:41 to 7:05. "Too much oversteer" "Wild ride" etc. This after GM 'fixed' it. Then from 7:50. Check the camber of the inside rear of both cars in turns.
This droop camber is easy to fix if you are a good fabricator. So much grip is being lost on the C7 because of the location of the upper A arms. Check the exit at the Karrosel at the Ring.
Send me the data I have requested in a previous post and I'll send you a fix for the C7's poor manors.
See my comments on the C7 chassis design some where in the forum. Nothing but praise but not for the reasons you would think. The long wheel base is magic otherwise the car would be uncontrollable as you eluded to.
Everyone in favor of banning this jackass from this thread please "thank" my post and add yourself to the petition list to be sent to the admin.
OK, I decided it was time to start prepping the car for the first event of the year at the end of the month. I measured the front and rear camber and rear caster and found some things I didn't like.
Last year I had a track alignment done. At the time the shop didn't have the tools so they didn't set the rear caster.
The front camber came in at -1.8 on both sides and the rear camber came in at -2.0 on both sides. I marked the cam positions with red nail polish so I could tell if they changed during the year.
Today I just took some quick measurements with the car sitting on the floor. Front camber was still -1.8 degrees on both sides and right rear camber was still at -2.0. However, left rear camber was -2.6 deg. The first thing I though of is a cam must be loose but when I squeezed under the car to check my marks there was no indication of slippage. WTF.
Then I squeezed under the back end and inserted my GM Caster Adapter and checked the left rear caster. It was +0.4 degrees. The right rear caster was -0.3 degrees.
So I think I have an issue with too much rear camber and uequal rear caster. I can't figure why the left rear camber would have changed if the cams didn't slip unless there is something wrong with one of the bushings.
I am wondering if some of the side slip I was getting in right turns when trying to use PTM to accelerate out of the turn may have been due to the large negative rear caster on the left side.
I have a two post lift so when I lift the car to work on it the wheels will be off the ground. Does anybody know if changes I make to the suspension when it is at full droop will correspond with how those changes will look after the weight is back on the wheels again and the suspension settled. In other words if I reduce the left rear caster by .6 deg while the car is in the air will it still show a .6 deg change once the car is on the ground?
Bill, I will guess yes it will stay the same but I have never tried other then watching toe move when raising and lowering. Just a thought a couple of cheap transmission jack stands that are 5 footers would be easy to set a block of wood on and set the car onto.
Nothing moved in the rear to change your numbers can be frustrating. My car had a change in the left front caster late last summer as we usually put it back to a street set up after. I think the UCA or LCA is bent! Will find out when we replace one or the other ahead of our first track day in May. Like your car nothing seem to move either.
OK, I decided it was time to start prepping the car for the first event of the year at the end of the month. I measured the front and rear camber and rear caster and found some things I didn't like.
Last year I had a track alignment done. At the time the shop didn't have the tools so they didn't set the rear caster.
The front camber came in at -1.8 on both sides and the rear camber came in at -2.0 on both sides. I marked the cam positions with red nail polish so I could tell if they changed during the year.
Today I just took some quick measurements with the car sitting on the floor. Front camber was still -1.8 degrees on both sides and right rear camber was still at -2.0. However, left rear camber was -2.6 deg. The first thing I though of is a cam must be loose but when I squeezed under the car to check my marks there was no indication of slippage. WTF.
Then I squeezed under the back end and inserted my GM Caster Adapter and checked the left rear caster. It was +0.4 degrees. The right rear caster was -0.3 degrees.
So I think I have an issue with too much rear camber and uequal rear caster. I can't figure why the left rear camber would have changed if the cams didn't slip unless there is something wrong with one of the bushings.
I am wondering if some of the side slip I was getting in right turns when trying to use PTM to accelerate out of the turn may have been due to the large negative rear caster on the left side.
I have a two post lift so when I lift the car to work on it the wheels will be off the ground. Does anybody know if changes I make to the suspension when it is at full droop will correspond with how those changes will look after the weight is back on the wheels again and the suspension settled. In other words if I reduce the left rear caster by .6 deg while the car is in the air will it still show a .6 deg change once the car is on the ground?
Bill
Bill, If you measure the caster at full droop and subtract the .6 it will work. it will be close. Pay very close attn to how you are measuring I cant stress the importance of making sure the car is level and backup your alignment machine with a hand held angle finde on the wheel most alignment shops rarely get the heads calibrated!!!!
Bill, If you measure the caster at full droop and subtract the .6 it will work. it will be close. Pay very close attn to how you are measuring I cant stress the importance of making sure the car is level and backup your alignment machine with a hand held angle finde on the wheel most alignment shops rarely get the heads calibrated!!!!
Mike,
Thanks for the feedback. I have been thinking of doing the alignment in my garage. Then any mistakes are my mistakes. I used to do my own alignments on my C5s and my C6Z. It took a long time to do since I had to drive the car around the block to settle the suspension between adjustments but it was doable.
When I check the car in my garage I have a spot that is level from side to side but there is a gentle down slope toward the garage door for water to drain out of the garage. When I took my caster readings I was using a Wixey gauge that has +/- .1 deg accuracy. I zeroed it by laying it on the ground alongside the rear tire in an attempt to compensate for the slope. The problem with that is the gauge is small and could easily have been sitting in a small dip (floor isn't exactly smooth although it was ground down before the Epoxy Coating was applied).
My thoughts are that I can raise the car on the lift and use my 6 ft carpenter's level across the lift arms on both sides of the car to get a reference point for the slope of the floor and what ever difference the lift makes when at full height. I can zero the gauge to each side of the car based on that and take my readings from there. I think I can use my Sears 2 ft Digital Laser Level set vertically against the tire to measure camber. I can measure it while the car is on the ground and then see what it is when the car is in the air and adjust from there.
If my caster readings from yesterday were correct then I should be able to adjust the left rear control arm front cam to reduce camber while increasing caster to your recommended amount. Hopefully, that will bring the camber close to what you recommend. On the right side I think it will be a little more complex since I have negative caster. That means adjusting the rear cam to move that side out while adjusting the front cam to move that side in thus pulling the ball joint forward.
It won't be as easy as doing it on a machine with the GM gauge since I won't be able to look at both gauges at the same time and have to hold the laser level up to the tire each time I want to measure camber.
I do have a Long Acre Digital Acculevel Caster Camber gauge with a magnetic attachment but that won't work on my ceramic rotors. I just purchased the Long Acre gauge mount that clamps to the wheel but the tire's rim protecting edge prevents the clamps from grabbing the edge of the rim.
Do you have any ideas on how I could get that adapter to work? Having the camber gauge securely fastened to the wheel would make the job easier.
Mike,
Thanks for the feedback. I have been thinking of doing the alignment in my garage. Then any mistakes are my mistakes. I used to do my own alignments on my C5s and my C6Z. It took a long time to do since I had to drive the car around the block to settle the suspension between adjustments but it was doable.
When I check the car in my garage I have a spot that is level from side to side but there is a gentle down slope toward the garage door for water to drain out of the garage. When I took my caster readings I was using a Wixey gauge that has +/- .1 deg accuracy. I zeroed it by laying it on the ground alongside the rear tire in an attempt to compensate for the slope. The problem with that is the gauge is small and could easily have been sitting in a small dip (floor isn't exactly smooth although it was ground down before the Epoxy Coating was applied).
My thoughts are that I can raise the car on the lift and use my 6 ft carpenter's level across the lift arms on both sides of the car to get a reference point for the slope of the floor and what ever difference the lift makes when at full height. I can zero the gauge to each side of the car based on that and take my readings from there. I think I can use my Sears 2 ft Digital Laser Level set vertically against the tire to measure camber. I can measure it while the car is on the ground and then see what it is when the car is in the air and adjust from there.
If my caster readings from yesterday were correct then I should be able to adjust the left rear control arm front cam to reduce camber while increasing caster to your recommended amount. Hopefully, that will bring the camber close to what you recommend. On the right side I think it will be a little more complex since I have negative caster. That means adjusting the rear cam to move that side out while adjusting the front cam to move that side in thus pulling the ball joint forward.
It won't be as easy as doing it on a machine with the GM gauge since I won't be able to look at both gauges at the same time and have to hold the laser level up to the tire each time I want to measure camber.
I do have a Long Acre Digital Acculevel Caster Camber gauge with a magnetic attachment but that won't work on my ceramic rotors. I just purchased the Long Acre gauge mount that clamps to the wheel but the tire's rim protecting edge prevents the clamps from grabbing the edge of the rim.
Do you have any ideas on how I could get that adapter to work? Having the camber gauge securely fastened to the wheel would make the job easier.
Bill
Bill, here are my thoughts. it can totally be done in your garage. I feel you will need to make 4 slip plate as simple as four squares of metal with grease in between and the angle finder on the caster tool. you need to be able to read the angle. we took a digital apart and separated the sensor from the readout so the read out display is visible without being under the car. you also need a 8 foot carpenters level to square up the car or get it reasonably close. it is way easier on a four post that is level for sure . at the track we use a setup table that is high enough to work under this is the most ideal condition if no four post is available
Bill, I had someone machine me an adapter for that level so it will sit on the hub face. However, I'm not convinced that's perfectly level either but it's probably as good as the rotor face.
Every time I've tried to do an alignment at home I have two problems. What I measure at home never seems to match what the alignment machine said, and the fact that the 4-post lift isn't wide enough to set toe plates up against the wheels.
I've checked my lift with a carpenters level and it sure appears to be level so I have to attribute it to how I'm affixing the camber gauge. Other than a string box I don't know how to measure the toe without taking the car off the lift.
I have a set of slip plates for the rear and turning plates for the front.
Another option is two linoleum tiles 14x14 with baby powder between them. You can also use multiple tiles to level you car with a laser level if the surface you are working on is uneven.
There used to be a thread in the Autocrossing Forum where we discussed DIY alignments.
I have two ways of measuring camber. One is with a Sears 24 inch Digital Laser Level and the other is with a very nice magnetically attached LongAcre Accugauge.
I use toe plates to adjust toe and the Sears Laser Level to set thrust angle and steering wheel angle. With my previous cars I would first set rear camber and then set rear toe and thrust angle. When I have the rear toe set where I want it I put the Digital Laser Level on top of the toe plates and with the bottom placed against the tire/wheel and aim the laser toward the front of the car. I place a jack stand next to the front wheel with a ruler attached to it and stick the other end of the ruler into the center of the hub making sure it is bottomed out correctly. Then I adjust the tilt of the level so it hits the ruler and record the reading. After that I move to the other side and do the same thing. Once I have my two readings I know which way to move each rear wheel to get near 0 thrust angle. Lou Gigliotti taught me this when he did a quick rear alignment on my C6Z at the Glen a few years ago. Once that is done I do the front end camber/caster and then use the toe plates to set total toe. Once I have toe set I make sure the steering wheel is locked in the center position and use my Digital Laser Level now aimed at the rear wheels and the ruler/jackstand to set the steering so the steering wheel is straight.
Doing this I was able to get very good alignments but they took a lot of time since I had to lift the car to make camber/caster and front toe adjustments and once the adjustments were done I had to drive the car around the block to settle the suspension.
The LongAcre magnetic gauge could be attached to the center hub through my street wheels so I had a nice way to fasten the gauge in place so I didn't have to move it between readings.
I did find that camber readings would vary if I used the rotor face to mount the gauge. If the gauge was mounted at the top or bottom of the rotor surface irregularities would affect the tilt of the gauge. If I mounted the gauge forward of the hub in the 9 or 3 position depending on which side of the car I was on I got consistent readings since the irregularities were not affecting the tilt of the gauge. I could verify my readings using the Digital Laser Level by placing it vertically against the tire (beside the bulge not on it).
I also have a set of Smart Strings that worked very well to set toe, thrust angle and steering centering. However, they take a fair amount of time for somebody with old man's eye sight to set up accurately (you really need to be able to see 1/64 increments in a low light level). It was also cumbersome to use them if I had to move the car any distance to settle the suspension.
Now with the C7 the Longacre gauge won't work with the ceramic rotors and the center holes of the stock wheels are too small for the gauge to fit through. I can do Camber/Caster in the front since I have the iron rotor AP Racing kit.
In the rear I have to use the Digital Laser Level placed against the tire for camber or hold the Longacre magnet against the Ceramic Rotor.
The Smart Strings don't work on the C7 Z with the Stage 2 Spoiler and the way the hatch opening is designed. The C7 hatch opening is missing the lip that I used in the C6 hatch opening to hold the end of the Smart String mounting brackets.
My curent plan for doing the C7 alignment is to verify my current alignment settings on the ground (other than rear wheel caster). Then I will raise the car on my two post lift and check camber at all 4 wheels with the wheels at full droop and then adjust camber by the difference I want to make. I will use a long carpenter's level to measure the fore aft level of the car and zero my Wixey gauge on the level and then use the gauge and adapter to measure rear caster. Based on what Mike mentioned in a previous post I should be able to subtract .6 deg from what ever caster reading I get to see on the ground rear caster. While doing that I will alternate between reading caster and placing the laser level against the rear wheels to measure camber. That will let me adjust each to get the numbers I want. Then I will repeat on the other side of the car. Then I will drop the car onto some masonite boards I use to provide slip plates. Two masonite boards at each wheel with a large plastic garbage bag between them. That will let me settle the car and verify my rear camber and caster readings. Once that is complete I will set rear toe and thrust angle since I can make those adjustments with out raising the car again. Then I will move to the front raise the car, adjust camber as needed, lower the car and check the caster reading at each wheel. Adjust those as necessary and then check toe/steering wheel angle while the car is lowered. That will let me calculate how many turns on each tie rod end will be needed to move each front wheel to get the toe I want at 0 steering wheel angle. Each step will take several adjustments and measurements before I reach the numbers I want. I suspect it will take about 3 hours to do.
Any comments on errors in thinking or procedure would be appreciated. If it gets too bad I will take it to the local dealer. The Corvette mechanic there said he will use my tools to set rear caster if I want it done.
I have a set of slip plates for the rear and turning plates for the front.
Another option is two linoleum tiles 14x14 with baby powder between them. You can also use multiple tiles to level you car with a laser level if the surface you are working on is uneven.
That Tenhulzan setup looked very nice and it looks like it should work on a 4-post lift. Which turn and slip plates are you using? Are you able to just drive up on them or do you have to lift the car and lower in on them?
I've tried using aluminum plates with a few drops of motor oil thing and that didn't work well. I'm inclined to just bite the bullet on something actually designed to be a slip/turn plate.
So started doing the alignment today. I took the following readings:
Front ======== Left ========== Right
Camber ===== -1.8 deg ======= -1.9 deg
Caster ====== +6.0 deg ====== +6.2 deg
Total Toe ===== 2/32 toe in
Rear ========= Left ========== Right
Camber ======= -2.6 deg ======= -1.9 deg
Caster ======== +0.4 deg ======= -0.3 deg
Total Toe ======= 6/32 toe out
I didn't bother checking thrust angle. I am pretty sure the left rear is toed out because the rear toe was set for toe in a year ago and the left rear camber wasn't as large as it is now. That pretty much means the thrust angle is off some as well.
When I raised the car I tracked what was happening with the camber at each wheel. What I found was interesting. Front left camber increased from -1.8 to -2.4 with the weight off the wheels. Front right and left rear camber didn't change and the right rear camber went from -1.9 to -1.4.
When I tried to insert the rear caster gauge adapter I found that can't be done with the suspension at full droop. The bottom of the shock absorber is in the way of inserting the bottom pin of the adapter. There is enough room once the adapter is in the hole so tomorrow I will lower the car with something under the left rear wheel to make some room to insert the adapter. I did take measurements from one lift arm to the other alongside the car's left side skirt and found they were sitting at 0.0 degrees. Then I checked the bottom of the car's frame and found it was level also. I am not sure but I think I won't be able to zero the caster gauge to the frame because when the car is sitting on its wheels I believe the frame isn't quite level with the ground. I know the C5s and C6s front frame lift points were spec'd at 5 mm less ground clearance than the rear frame lift points and I don't see any reason why the C7 is any different. If suspect if I use the frame as a zero point for the level that will produce an error in my caster measurement. I know I want to add +0.4 deg of positive caster so it may be better to zero the gauge when it is attached to the adapter and look for it to read +0.4 as I adjust camber and caster.
I noticed the left rear toe adjustment cam is all the way out to its max point so I will have to reduce camber at both the front and rear control arm mounts to get enough play to correct the toe settings.
So started doing the alignment today. I took the following readings:
Front ======== Left ========== Right
Camber ===== -1.8 deg ======= -1.9 deg
Caster ====== +6.0 deg ====== +6.2 deg
Total Toe ===== 2/32 toe in
Rear ========= Left ========== Right
Camber ======= -2.6 deg ======= -1.9 deg
Caster ======== +0.4 deg ======= -0.3 deg
Total Toe ======= 6/32 toe out
I didn't bother checking thrust angle. I am pretty sure the left rear is toed out because the rear toe was set for toe in a year ago and the left rear camber wasn't as large as it is now. That pretty much means the thrust angle is off some as well.
When I raised the car I tracked what was happening with the camber at each wheel. What I found was interesting. Front left camber increased from -1.8 to -2.4 with the weight off the wheels. Front right and left rear camber didn't change and the right rear camber went from -1.9 to -1.4.
When I tried to insert the rear caster gauge adapter I found that can't be done with the suspension at full droop. The bottom of the shock absorber is in the way of inserting the bottom pin of the adapter. There is enough room once the adapter is in the hole so tomorrow I will lower the car with something under the left rear wheel to make some room to insert the adapter. I did take measurements from one lift arm to the other alongside the car's left side skirt and found they were sitting at 0.0 degrees. Then I checked the bottom of the car's frame and found it was level also. I am not sure but I think I won't be able to zero the caster gauge to the frame because when the car is sitting on its wheels I believe the frame isn't quite level with the ground. I know the C5s and C6s front frame lift points were spec'd at 5 mm less ground clearance than the rear frame lift points and I don't see any reason why the C7 is any different. If suspect if I use the frame as a zero point for the level that will produce an error in my caster measurement. I know I want to add +0.4 deg of positive caster so it may be better to zero the gauge when it is attached to the adapter and look for it to read +0.4 as I adjust camber and caster.
I noticed the left rear toe adjustment cam is all the way out to its max point so I will have to reduce camber at both the front and rear control arm mounts to get enough play to correct the toe settings.
Bill
Bill, Interesting information. Odd how the camber changed on one side and not the other, something does not sound right. Could that be bent control arms changing or not in this case the camber angles? We are finding control arms more and more being produced light and sacrificial. Please and as I suspect you would let us know if you figure that issue out. I just got a set of rear toe bar turn buckles from Granatelli as we found the same issue not getting the rear toe in to what we wanted with lots of camber. Hope I get time this spring to do some camber, caster, toe sweeps under full compression to full droop. The only way to know exactly what these suspensions are doing.
12-31-2016, 05:41 PM
