Installing a Rack & Pinion

Suspension Tuning, Troubleshooting, Design and Discussion

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Bobalos
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Installing a Rack & Pinion

#1 Post by Bobalos » Wed Jun 15, 2005 3:55 pm

Dave,

I was wondering if there is a general rule of thumb type of thing I would follow to put a R&P setup into my 66 Chevelle.

right now its a Nose heavy BBC car with Iron heads, that has a Manual box with GM Disk's on the front of it. I was hoping I could take the box & all that off, stick the rack on & then figure out the rod end lengths as I go.

My concerns are:

How far forward to I put the Rack.
How far vertical does it go?

thanks
Bob

DOTracer
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R&P install

#2 Post by DOTracer » Wed Jun 15, 2005 4:25 pm

I'd like to hear more on this as well. It's my understanding that the most important thing in the install is making sure you minimize, or do anything you can to eliminate bump steer. I also understand that the R&P pivots should be the same width as the lower control arm bolts. BUT, I've seen plenty of installs where the R&P was wider than the lower control arm bolts.

I'd definately be interested in hearing specifics on how to properly install a R&P. My own car is a 79 Malibu. Most of the R&P installs I've seen on the G-body cars looked like butcher jobs at best with little attention paid to proper installation.

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#3 Post by David Lemmond » Thu Jun 16, 2005 10:46 am

Hi guy's.

You've got two option's when putting racks on race cars, put them where they need to go and put them where they will fit. Usually the later is what you end up with because of oil pan, balancer and etc..

While I have not done enough Chevelle's/Malibu's to give you measurements to go by, I can give you some ideas that should help.

I try to put the center of the rack dead center of the lower control arm bolts. (the pivot point) I try to get it as close as possible to being in line with the steering arm tie rod hole. The reason is this will give you the most amount of turning radius. It does not hurt to go forward from there to miss the pan or whatever else is in the way.

I don't like to go more than about 2- 2.5 inches forward with out adding length to the steering arm (build a new one) . If you don't build a new steering arm the issues will be-- the bumpsteer is harder to overcome because of the two arcs that the tie rod is going thru during the launch and landing, and the next one can be that the steering arm can become over center with the tie rod when you turn real sharp. This happens mostly while backing up with the tires cut sharp- the tires will drag.

Hope this helps some. It may be easier to try to answer your specific questions because I know I have not covered everything.

David
David Lemmond's Race Shop
Somerville, Al.
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Specializing in 10.5 tire cars chassis, suspension, and components.
67-69 Camaro, 68-74 Nova Tubular A-arms.
62-67 Chevy II tubular A-arms.

DOTracer
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#4 Post by DOTracer » Thu Jun 16, 2005 10:57 am

David,

thanks for the reply.

Do you recommend using a custom width rack to match the width of the lower control arm pivots/bolts? I'm pretty sure the Pinto & Mustang II racks are both too wide. Do you know the pivot widths for either of those racks to compare?

I see Chris Alston makes custom width racks, but their pretty pricey.

The lower control arms on the Malibu/G-body chassis has the rear lower control arm bolts wider than the front bolts. The front control arm bolts are approx 19" center to center.

Also, what is the correct method to measure and verify for bump steer. I believe it involves removing the coil springs and jacking the control arm up and down through it's travel takng recordings at specific traval intervals? How much bump steer is allowable?

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#5 Post by John_Heard » Thu Jun 16, 2005 2:29 pm

Just a note: Pivot points on the Wilwood/Pinto design rack are 24.5 inches.

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stracer859
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bump steer

#6 Post by stracer859 » Thu Jun 16, 2005 9:33 pm

hi my name is Tim Kelley, david lemmond helped me do my bumpsteer and a few other odd and end things. he is great i would and will recommend him to anyone for chassis work.

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#7 Post by David Lemmond » Thu Jun 16, 2005 11:32 pm

Todd
I have used the Pinto style rack on Chevelle's before. You can get the bumpsteer in to an acceptable range in the travel you will be using.

It would be a lot simpler to use the Alston rack with pivot points to match your car. It would take at least one of the variables out of the job.
I have used one and put it on an S-10 that worked great. It is a nice piece for sure. It's not quite as simple to mount as pinto style but I think it would be better for you to use it if you can.

On the bumpsteer, first make sure the caster and camber is set like you want it. Then like you said remove the springs and shocks and move the suspension through it's expected travel range to get into tolerance.
Bickle recommends 3/16" max on his cars. I think if you can get it to within 5/16 total with no toe out at any time your fine with these heavy cars.
I've seen worse come in and still be going down the track.
I had a guy come in the other day that someone had put a rack on, and had 5/8" toe out total and was still driving decent but shook bad when he stepped on the brakes.
David Lemmond's Race Shop
Somerville, Al.
256-778-8888
Specializing in 10.5 tire cars chassis, suspension, and components.
67-69 Camaro, 68-74 Nova Tubular A-arms.
62-67 Chevy II tubular A-arms.

David Lemmond
Posts: 123
Joined: Thu May 12, 2005 2:26 pm
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#8 Post by David Lemmond » Thu Jun 16, 2005 11:33 pm

Hey Tim
How's everything?
Got that Nova going yet? Thanks for theprops!

David
David Lemmond's Race Shop
Somerville, Al.
256-778-8888
Specializing in 10.5 tire cars chassis, suspension, and components.
67-69 Camaro, 68-74 Nova Tubular A-arms.
62-67 Chevy II tubular A-arms.

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John_Heard
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#9 Post by John_Heard » Fri Jun 17, 2005 6:56 am

David, what's an easy way to check toe while checking bump steer? I've been thinking about making me a fixture of some sort to aid doing this.

Seems like toe-in is something I have to recheck or change several times a year when I'm screwing around with the front end. Would sure be handy to make something. I never get very good results trying to do it with a tape measure.

I was looking at some of those lasers at the hardwares store the other day and was wondering if a person couldn't make some kind of mag mount to put it on the spindle. Not sure what kind of spot size they have at distance, maybe wouldn't work.

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#10 Post by David Lemmond » Fri Jun 17, 2005 9:08 am

John I still use the tape measure. I've been intending on building something but never seem to do it. lol
I use the laser alot checking for chassis squareness and it is very handy. I think you could make that work well.
Also, if you have the front clip off you could clamp a straight edge the length of the diameter of your tires to your rotors and measure off them.

David
David Lemmond's Race Shop
Somerville, Al.
256-778-8888
Specializing in 10.5 tire cars chassis, suspension, and components.
67-69 Camaro, 68-74 Nova Tubular A-arms.
62-67 Chevy II tubular A-arms.

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John_Heard
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#11 Post by John_Heard » Fri Jun 17, 2005 10:35 am

Bump Steer Measurements..

This looks like it would be great...

Why couldn't someone make something like this but with a Stanley laser?http://www.advancedracing.com/pic.php?p ... e=products

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stracer859
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david lemmond

#12 Post by stracer859 » Sun Jun 19, 2005 7:11 pm

you are very welcome on the props man, you helped me out a lot. well between work, this that and the other the car is not done yet. ive only been to a race track once this year and that was yesterday @ ohio valley. i hope to get it goin soon, really need to crack down on it and get it done.
how is everything goin with you and your stuff

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