Recommended Posts

Could you get the ride height data for each front wheel from the OBE II interface and use that to track wheel position?


CTS-V_Dashboard.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

Share this post


Link to post
Share on other sites

3 minutes ago, Cadillac Jim said:

Could you get the ride height data for each front wheel from the OBE II interface and use that to track wheel position?

My car is the ESC with non-electronic suspension. I went that route so that I could build it old school. I'll have to make measurements using a tape measure.


Click here to visit the main directory for my subforum about my 2002 Eldorado build for autocross racing:

http://caddyinfo.ipbhost.com/index.php?showforum=96

Share this post


Link to post
Share on other sites

You don't need the OBD II system if you read the sensors directly.  The ride height sensors are, within the sensor, just a source of voltage proportional to sensor arm angle.  It's possible that there are more electronics in the sensors, and they vary from year to year, but if you interface with the sensor directly, you can have data recording or even cockpit monitoring of wheel height on each wheel with signal directly from the wheel height sensors.

You can install the ride height sensors of your choice or even make your own.  If the sensors are a problem for racing, you can remove them after testing.

This is a concept of a wheel height sensor.  Complexity added in later models will include a gear reduction between the sensor lever and the voltage divider shaft, and, for a later model that uses full modules at the wheel height sensors, digital electronics to digitize the voltage output and put it on a Class 2 bus.  You will like the early model, perhaps with the gear reduction (a little plastic planetary producing about 4:1 is about right).  You will need to calibrate your guages from 0-5 volts to inches or cm of wheel height.

Notional_Wheel_Position_Sensor.png


CTS-V_Dashboard.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

Share this post


Link to post
Share on other sites

It is a good idea and it looks doable, but I'm really not interested in spending the time to build or troubleshoot the system for this car... I mean, sure as a scientific minded individual, the prospect of geeking out the car has crossed my mind many times. However, if the final cut of the springs result in fender lips that sit at (or just below) the top of the tire tread, we're good. 

The Grand Prix struts are also non-electronic. So if I was going to add the ride height sensors, it would be a "from scratch" build.

Now if I was using air bags instead of springs, it would be cool to even program pre-set heights and control them from the driver seat.

Rough road

Smooth road

High speed

Smooth track

Car show low


Click here to visit the main directory for my subforum about my 2002 Eldorado build for autocross racing:

http://caddyinfo.ipbhost.com/index.php?showforum=96

Share this post


Link to post
Share on other sites

One thing I didn't mention before. The Thunderbird springs have about 0.10" wider inside diameter than the springs intended for the Cadillac upper mounts. To keep them tight and centered on the perch, I used their isolators in addition to the isolators supplied with the mounts. This made them a press fit and it also increases the vibration absorption.

I used the springs' lower isolators in place of the Grand Prix strut lower isolators on the bottom and they fit well with the contour of the strut base. There is just a slight spring overhang on the inboard side of the perch, but the spring is fully supprted and the fit is good and safe.


Click here to visit the main directory for my subforum about my 2002 Eldorado build for autocross racing:

http://caddyinfo.ipbhost.com/index.php?showforum=96

Share this post


Link to post
Share on other sites

The Cadillac uses 16MM bolts to mount the struts to the spindle. And it uses slotted lower holes to make camber adjustments. The Grand Prix struts use 14MM bolts and do not have a slotted hole. I bought a 16MM drill bit to open the GP holes, but instead of slotting the lower hole, I chose to first try camber adjustment bolts on the upper hole.

0917171854a-1.jpg

The camber adjustment bolts are 14MM with an egg-shaped cam for positioning the spindle. By marking the bolt head and spindle, I can dial in some camber for the track and return it to the original setting for the street.


Click here to visit the main directory for my subforum about my 2002 Eldorado build for autocross racing:

http://caddyinfo.ipbhost.com/index.php?showforum=96

Share this post


Link to post
Share on other sites

The ride height sensors don't have anything to do with the shocks, electrically.  They are little boxes that bolt to the chassis and have arms that stick out, then links from the ends of the arms to a suspension arm.  All Cadillacs that have rear-end leveling have them on the rear.  The ones that connect to the PZM have three-wire connectors (hot on start and run, ground, signal).

But, I see your point, and also that you have moved on.

Adding a bolt with a cam on it for quick adjustment of camber for road vs. track is a really great idea.


CTS-V_Dashboard.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

Share this post


Link to post
Share on other sites
26 minutes ago, Cadillac Jim said:

The ride height sensors don't have anything to do with the shocks, electrically.  They are little boxes that bolt to the chassis and have arms that stick out, then links from the ends of the arms to a suspension arm.  All Cadillacs that have rear-end leveling have them on the rear.  The ones that connect to the PZM have three-wire connectors (hot on start and run, ground, signal).

 

Oh, yeah. I remember seeing those on the ETC models. My lowe A-Arms have unused tabs for them and I bet that all necessary bolt holes are in place too.

It might not be such a pain to add on. Worth another look when I get the car farther along.


Click here to visit the main directory for my subforum about my 2002 Eldorado build for autocross racing:

http://caddyinfo.ipbhost.com/index.php?showforum=96

Share this post


Link to post
Share on other sites

My thinking is that if you do geek out the car just a bit, like you do when you use auto tuning software, having a record of ride height for each wheel could be very valuable in selecting shock damping, evaluating tires, etc.  Very little software can tell when all the tires aren't in the same plane and thus flag wheel hop, for example, and whenever any wheel hits its limit of travel you need to know that the suspension dynamics have gone back to the stone age for that wheel.  I can think of ways that a real-time display from that data could be more valuable in an autocross race than any other dashboard readout.


CTS-V_Dashboard.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

Share this post


Link to post
Share on other sites

A very good point, Jim. Very good. The readout would have car show value as well. 

It may even be possible to incorporate accelerometer data to get lateral acceleration values along with using the ride height sensors to gauge the car's tilt and determine what amount of outboard tilt provides the right balance between loading the outboard front tire for traction in a turn vs. level ride for stability and suspension geometry.

Front suspension roll, rear suspension roll and the combination of both could be tuned for the best overall result or for the slow sharp turns of solo 2 races where reaching speeds above 50 MPH is rare as opposed to the faster sweeping turns of pro solo where 80 MPH or more might be experienced.

I could even replace the manually adjustable supports on the rear wing for actuators and have a variable rear end down force capability.

Come to think of it, I would like to explore these possibilities as a phase 2 upgrade.

For now, I will focus on finishing up this phase 1 build and then work on some engine and paint and body issues. As it is, due to time and money limitations, this car has not been driven regularly in a year and a half, and now leaks oil too badly to be driven again without attention to the engine. It has been up on jackstands for 3 months for this front end build, and my suspension build in current form started about 4 years ago.

I need to finish baking the cake then work on the icing.

BTW: I was playfully using the "geek out" term.


Click here to visit the main directory for my subforum about my 2002 Eldorado build for autocross racing:

http://caddyinfo.ipbhost.com/index.php?showforum=96

Share this post


Link to post
Share on other sites

Engine oil leaks?  That bothers me because sitting unused should not cause things to open up.  Where is the oil coming from?

Wheel height sensors can always be added later because it's all totally separate and the mounting is easily accessible.  It's the kind of thing you would use in road tuning and trial laps, and you don't need it in the way when you're doing design and construction.  I got the idea when you mentioned wheel travel limits and measuring wheel height with the strut bellows/boot off, then having to put the bellows/boot back on for the road.


CTS-V_Dashboard.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

Share this post


Link to post
Share on other sites

Not sure where the oil leak is but it's too bad to drive it safely on the street.... Okay, so I tried the struts and the car sat too high, so I cut an extra 3/4 of a coil off. Here is the stock ride height:

0701151814c-1_1.jpg

And here is how it sits now:

1019171802n.jpg

Just about PERFECT.


Click here to visit the main directory for my subforum about my 2002 Eldorado build for autocross racing:

http://caddyinfo.ipbhost.com/index.php?showforum=96

Share this post


Link to post
Share on other sites

I noticed a bit of optical illusion in the photo caused by the difference in front/rear fender heights; the car actually sits a 1/4" lower in the front. 

As pictured, the strut tower brace plates have not yet been installed and they are 1/4" thick so if no changes are made, the ride height will be level.

For esthetics, I would prefer a slight forward rake, however a level ride would deliver better cornering ability. And as it is now, I no longer need spring compressors to take the strut assemblies apart. The only pre-load is a half inch compression made when the nut is tightened. Not much room to remove more spring.


Click here to visit the main directory for my subforum about my 2002 Eldorado build for autocross racing:

http://caddyinfo.ipbhost.com/index.php?showforum=96

Share this post


Link to post
Share on other sites

I might be able to trim just enough off of the springs to compensate for the 1/4" of height that the strut tower brace plates would create but that would also only give me only about 1/4" of preload on the springs, which could be anything from 250-300 lbs. of pressure to keep enough friction between the springs and the perches to prevent them from re-clocking themselves if one side of the car is completely unloaded during an encounter with rough pavement in a turn. That should be enough, but if I miss judge the cut and remove too much spring preventing a good lockdown between the perches, then the springs would be trash.

I haven't yet decided if I want to risk another cut. 


Click here to visit the main directory for my subforum about my 2002 Eldorado build for autocross racing:

http://caddyinfo.ipbhost.com/index.php?showforum=96

Share this post


Link to post
Share on other sites

The swaybar end links are not yet connected so my short drive allowed me to get the true feel of the springs and the Comp G struts without the added firmness that a swaybar would provide when both sides of the car are tied together. We can say bye bye to the Cadillac-style ride as this car is now very firm. The stiffness of the springs and the firmness of the struts gave it almost flat cornering and a ride that was very sports car-like. It wasn't bone-jarring harsh, but I'll have to get used to it.


Click here to visit the main directory for my subforum about my 2002 Eldorado build for autocross racing:

http://caddyinfo.ipbhost.com/index.php?showforum=96

Share this post


Link to post
Share on other sites

I think that the 1/4" rake is intentional for stability and downforce at very high speeds.  You won't need it if you stay under about 120 mph.  There may be some other benefits.


CTS-V_Dashboard.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

Share this post


Link to post
Share on other sites
6 hours ago, Cadillac Jim said:

I think that the 1/4" rake is intentional for stability and downforce at very high speeds.  You won't need it if you stay under about 120 mph.  There may be some other benefits.

A slight forward rake is beneficial for downforce and drag coefficient management at highway speeds and above (as wll as giving the car the "new school" agressive stance). However, the "old school" aggressive stance of the 60's and early70's where the front is higher than the rear helps rear wheel drive drag cars launch and front wheel drive cars corner in autocross due to weight transfer.

I just don't like the old school squatting rear look even though it would help my application.


Click here to visit the main directory for my subforum about my 2002 Eldorado build for autocross racing:

http://caddyinfo.ipbhost.com/index.php?showforum=96

Share this post


Link to post
Share on other sites
1 hour ago, CadVetteStang said:

A slight forward rake is beneficial for downforce and drag coefficient management at highway speeds and above (as wll as giving the car the "new school" agressive stance). However, the "old school" aggressive stance of the 60's and early70's where the front is higher than the rear helps rear wheel drive drag cars launch and front wheel drive cars corner in autocross due to weight transfer.

I just don't like the old school squatting rear look even though it would help my application.

You are the expert on the requirements and design for your application, which, as I recall, is autocross/gymkhana contests.  I would think that total agility contests like that would favor a level car, as you say.

I qualify my opinion that the rake is for high speed stability as just that, an opinion.  I based it initially on these points:

  • My ETC came with the rake.  The car was exactly on the ride height specifications in the FSM (with new tires) throughout its life.
  • My ETC did not come with a spoiler.  I don't believe that a factory RPO spoiler was available for the 1997 ETC.
  • The owner's manual states "This car will go 150 mph."  Car & Driver timed a 1997 ETC (I believe, it might have been an STS) at 145 mph on their home test track, which has a good straightaway but is not suitable for testing top speed of very fast cars.
  • I'm not at all sure that the ETC body style would be stable above 120 mph without the rake; this is, of course, yet another opinion.
  • The ETC/STS (VIN "9" cars) designed to run with the big dogs on the Autobahn, and the VIN "Y" cars were designed to keep up with traffic (up to 120 mph or 195 kph) .  This is from the car trade mags of the time.
  • The  throttle response and stability at 100++ certainly supports real-world long-distance driving at those speeds, while dealing with similar-speed traffic and real-world roads that are designed to support such traffic.  So says a friend.

Now, if I had one to test, and had wheel height sensors available in real time with output available for recording, I could verify the utility of the rake in keeping reasonable weight on all four wheels at speed.  Wheel height, with spring rate, translates into weight on the wheel, a point that is used in the PCM/PZM/BCM in traction control and electronic stability control.


CTS-V_Dashboard.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

Share this post


Link to post
Share on other sites

We are in complete agreement on those points. And while the old school raised front or sqatted rear does help with autocross cornering (speeds rarely get above 40 MPH in Solo II and 70 MPH in Pro Solo), the lift caused at higher speeds are dangerous. My 70 Eldorado had a sagging rear due to air shock load leveling failure and in a top speed test, I had to back off of the acceleration when the car reached 115 MPH because the wind under the 4,860 lb. car had lifted the front end to full height and the steering was very touchy. I had plenty of untapped power and would not have lived to see the 150 MPH potential.


Click here to visit the main directory for my subforum about my 2002 Eldorado build for autocross racing:

http://caddyinfo.ipbhost.com/index.php?showforum=96

Share this post


Link to post
Share on other sites

I recall a friend from my high school who put a 1955 Chevy V8 in his 1949 Oldsmobile (huge fastback, as you recall) and it woudln't go over 110 mph or so because the rear wheels would come off the ground.  I asked why the Olds V8 didn't run at least as good, and he said that the Chevy V8 was much faster.

What I didn't know at the time was that the 1949 Olds V8 was 303 ci but only came with a two-barrel and was rated at 135 hp.  The standard 1955 Chevy V8, 265 ci, was rated at 162 hp with the two-barrel, 180 hp with the four-barrel and dual exhausts (and probably different heads), and 195 hp with the "power pack" (4 barrel carb, cam, dual exhausts, very probably different heads and valve sizes).  And, it was instantly recognized as tunable.  The 1956 Corvette offered the 265 in 210 hp, 225 hp, and 240 hp.  But that technology was available to the rich kids, none of whom I knew other than to recognize in the hallways at school.


CTS-V_Dashboard.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

Share this post


Link to post
Share on other sites

184035_Rear_3-4_Web.jpg.c6b22a7d5aa3c7a234fb34867f6c55ca.jpg

Ya gotta love the 40's


THERE IS ALWAYS ENOUGH TIME TO DO THE JOB RIGHT - THERE IS NEVER ENOUGH TIME TO DO THE JOB AGAIN !!!

Share this post


Link to post
Share on other sites

It looks really great, even today.  I wonder how that car would look with a spoiler...


CTS-V_Dashboard.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

Share this post


Link to post
Share on other sites
On 11/17/2017 at 1:23 AM, OldCadTech said:

184035_Rear_3-4_Web.jpg.c6b22a7d5aa3c7a234fb34867f6c55ca.jpg

Ya gotta love the 40's

👍 great looking car!


Click here to visit the main directory for my subforum about my 2002 Eldorado build for autocross racing:

http://caddyinfo.ipbhost.com/index.php?showforum=96

Share this post


Link to post
Share on other sites

I love that aftermarket windshield sun shade.  Those were quite the accessory in the sun belt during the 1940's and 1950's.


CTS-V_Dashboard.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Recently Browsing   0 members

    No registered users viewing this page.