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View Full Version : Modified / Custom Front Suspension Questions – ’92 Camaro



FlyDoc
09-15-2013, 02:46 AM
With my 92 I have installed a ’90 Vet IRS, and I have wondered if only putting on Spohn K-member, and A-arms with adjustable delspherical ends, is really the way to go for the best geometry for auto-X, and the road. Because the technology on these cars is pushing 35 years old, and just improvement in tires eclipses the suspension, and the adjustability that is available even with all the do-dads available.
I have been considering the addition of UCA’s, and different spindles, or reworking the RaceCraft ones that I have. They are their 2” drop with short steering arm for there rack & pinion steering. There has been some issues with these spindles braking, and RaceCraft not standing behind their product, if you would like to see that hub-a-hub-a see the thread - http://www.thirdgen.org/techboard/suspension-chassis/672886-racecraft-drop-spindle-failure.html but looking at the photos, and stated, it looks like welding issues. If I move the steering arm inward, I can go with wider wheels.
When I was reading Eric’s thread on his Camaro, I stated that there was some stuff I did not under stand/or know. I found this sight when I was looking up scrub radius, - http://www.racecartuner.com I have spent some time here but a lot more is needed!

What I’m looking at now is by adding UCA’s with the adjustable LCA’s and modifying the spindles for use with ball-joints, I will be able to set my scrub radius, static caster & camber, control the camber, install a manual rack (I’m installing a Electric Power Assist steering)

*Now for the hard part*
*Deterring the optimal mounting points for the UCA’s
*I downloaded a suspension analyzer, in which does not work on a Mac, then just trying to figure out what each measurement is. I would think if I could find the numbers for a third gen Camaro would be the easiest starting point.
* I do not want to take a saws-all to the front of my car! I will be installing a cage, so I will be able to place mounting points at will. As for the shocks I will place them above the UCA, and use the uppers strut mounting point for the shock, and the coils will be in typical position. Other plans at this point will be an engine set-back of 4-6”, cage, removing floor pans lowering and flat bottom floor pans, and moving the gas tank down to in front of the rear axle under the rear seats hoping to get about 16-22 Gallon’s of gas.

OK guys tell me what you think, and the pros and cons, or what ever you come up with.

SLO_Z28
09-15-2013, 09:05 AM
I dont think there is anything at all lacking with the 3rd gen. Out of 34 drivers in the SCCA Solo Nationals in the E-Street Prepared class, a 88 firebird came in second place. He had to drive over subaru WRX's, 2005+ mustangs Shelbys/GT's/Boss, and LS1 camaros. If that isnt proof that the suspension can stand up to the test of time I dont know what is. Of course installing IRS could have upset the car, so your best bet is going to a chassis setup guy at like a road racing shop or circle track shop, and having them pull data from your rear suspension and adjust the front to match.

My CMC car isnt very modified, but it is a very fast, very predicable car to drive. It doesnt take much.

Ron Sutton
09-16-2013, 09:24 AM
Hi Doc!

I don't know of any database of stock front suspension geometries. I find they vary too much from car to car anyway, because an 1/8" in certain spots can be a big deal.

No offense, but it sounds like you're looking for a short cut, and I don't know any. I do this as a professional & this is complex stuff with many variables. There is no simple "put this here & adjust" answer. Eric's was already "in the ball park" and I caught some conflicts based on his goals.

To work out your front suspension, for your goals, I see a few options:
a. Do nothing. Meaning leave it & run it as it is.
b. Guess where to put the suspension points, then prepare to trial & error various changes.
c. Measure your car, learn suspension geometry, decide the best combination for your application (with advice) & then make the mods.
d. Hire a shop to measure your car & recommend a combination for your application & you make the modifications.
e. Hire a shop to measure your car, determine the combination & they make the modifications.

If you go with C, I can make some recommendations on books, software and specific target for roll center, camber gain, caster, etc, if I know the rest of your set-up and objectives.

FlyDoc
09-17-2013, 12:03 AM
I like "C"
If you could recommend a book/sight/software, that teaches me how to take the measurements, then that gives me a starting point.
I know that here in HI for our autoX once I get it set, I will not have to change it, because of how small are run area is, but I still want the adjustability because we will eventually move to the mainland probably the Austen TX area.

Ron Sutton
09-17-2013, 06:55 AM
I like "C"
If you could recommend a book/sight/software, that teaches me how to take the measurements, then that gives me a starting point.
I know that here in HI for our autoX once I get it set, I will not have to change it, because of how small are run area is, but I still want the adjustability because we will eventually move to the mainland probably the Austen TX area.


Gotcha !

I don't know of a website that teaches how to measure the car's suspension points. I outlined a "how to" for Lance Hamilton in his Monte Carlo AutoX on this website. I think that entire thread would be a good read for you and worth your time.

The "how to" on measuring suspension points starts in Post #51

It starts here (https://www.pro-touring.com/threads/98063-Need-a-little-help-figuring-something-out).

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I tend to recommend Performance Trends for software, because it's easiest to learn & use. Here are some options.

A. The full suspension design software, which is more complex to use, mainly because you have to sort through a gazillion input options you probably won't use. Most of this type of software only measure in 2 dimensions. Of the advanced, 3 dimensional measuring software options ... Performance Trends software is the easiest to use. But that's like saying brain surgery is easier than rocket science. It's $400 & you can see it HERE (http://performancetrends.com/SuspAnzr.htm).

B. A better bet is to get their basic front suspension software, called Roll Center Calculator, which I highly recommend for car guys working out their roll center, camber gain, dive evaluations, etc. It is $79. Go HERE (http://performancetrends.com/rc.htm).

C. The best bet would be getting their "Roll Center Calculator PLUS" for $129 that includes rear suspension & overall handling calculations, which I think is important. You'll have a full suspension program for only $129. Same location (http://performancetrends.com/rc.htm).

The FLLD calculation in the "Plus" is worth the price of the software all by itself, because you can work out combinations of roll center, spring rates & sway bar rates and KNOW how balanced the car will be.

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As far as book recommendations ...

If you desire to learn about chassis set-ups & suspension tuning, there are a few good books... covering design, engineering, theories, tuning, etc ... I think the right book for a person depends on how in-depth they plan to get. There are great books, good books, ok books & horrible books written on the subject. Some books contain old school information ... some newer technology ... and some in-between.

I often recommend books, but the right one depends on the person's goals. Based on our conversation, I would recommend these books, in this order. If at any point, it's get so complex, you're not enjoying it, that's a place to stop. On the other hand if you become hungry for more in-depth knowledge, then work your way through the list.

1. Herb Adams was the "go-to" guy in the 70's & 80's. Technology has advanced quite a bit, but this book is an excellent starting point. It's a good read & much of it is still relevant. Just be open minded that some suspension set-ups have advanced & changed dramatically. Go HERE (http://www.us.penguingroup.com/nf/Book/BookDisplay/0,,9781557880550,00.html?Chassis_Engineering_HP105 5_Herb_Adams).

When it comes to books, they are all behind what professional race teams are doing. Top race teams with 30 Engineers, full Research & Development staffs and state-of-the-art testing technology ... are understandably reluctant to share info ... until it's so old it won't hurt them competitively. So with books, there will always be a lag.

Steve Smith race suspension books are the easiest to understand & have somewhat up to date stuff on advanced suspension set-ups. Don't ignore it because it's oval track. While there are some differences ... handling is handling ... and NASCAR teams utilize cutting edge technology today. I recommend two books from them.

2. HERE (http://www.ssapubl.com/%28X%281%29S%2805nfb1musiblll55prpczr45%29%29/product.aspx?nbr=S239&AspxAutoDetectCookieSupport=1) * If you only buy one book, this is the one.
3. HERE (http://www.ssapubl.com/product.aspx?nbr=S295&AspxAutoDetectCookieSupport=1)

4, 5 & 6. The best books ever are from Carroll Smith (passed away several years back). They are a little hard to read, for a rookie & non-engineer, but a very solid foundation. The three I suggest you start with are “Prepare to Win”, "Engineer to Win" & "Tune to Win." Go HERE (http://www.carrollsmith.com/books/prep2win.html), HERE (http://www.carrollsmith.com/books/ngner2win.html)& HERE (http://www.carrollsmith.com/books/tune2win.html).

7. Finally, the most complex, in engineering speak, is from Mitchell & Mitchell, titled Race Car Vehicle Dynamics. See it HERE (http://books.sae.org/book-r-146/).

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Lastly, I'm happy to help & provide guidance. I am subscribed to this thread ... so just ask questions on here & I'll answer on here so everyone following along can learn too.

If you do, please post photos wherever possible, because I'm very visual.

Best wishes.