Thread: Rack & Pinion measurements?

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I'm in the process of installing a C3 vette front suspension on my 48 Olds. I finished the upper and lower A-arm installation over the weekend, and now have the knuckles on.
Now I need steering. I would like to go with a power rack & pinion unit, and the tie rod width needs to be 45"-46", with the inner tie rod ball joints to be approximately 30".
Anybody know were I can get measurements for these rack & pinion units?

It sounds to me like you have taken Corvette pieces and adapted them to your Olds frame without having a well-thought-out plan. If you have the control arms attached and are just now beginning to think about the rack, I know that you haven't done any planning and that you know little or nothing about independent front suspension and steering geometry.

I have no answers for you and I doubt that anyone else on this board will either. You need to do some heavy reading and educate yourself before going any further. Otherwise, I can see your Olds sitting out front a few weeks from now with a For Sale sign on it because you can't get the bumpsteer and evil transient handling response out of it.

The best way to do what you're trying to do would be to graft the entire front clip from the Vette onto the Olds frame. You would use the Vette steering rack and everything would be correct in relation to everything else.

Originally posted by techinspector1
It sounds to me like you have taken Corvette pieces and adapted them to your Olds frame without having a well-thought-out plan. If you have the control arms attached and are just now beginning to think about the rack, I know that you haven't done any planning and that you know little or nothing about independent front suspension and steering geometry.

I have no answers for you and I doubt that anyone else on this board will either. You need to do some heavy reading and educate yourself before going any further. Otherwise, I can see your Olds sitting out front a few weeks from now with a For Sale sign on it because you can't get the bumpsteer and evil transient handling response out of it.

The best way to do what you're trying to do would be to graft the entire front clip from the Vette onto the Olds frame. You would use the Vette steering rack and everything would be correct in relation to everything else.

I appreciate your concern, and can understand why you may think I haven't done any planning. But I can assure you I have.
I'll even scare you a little more. I only used the upper vette A-arms on the olds frame, with some fabricated brackets. And kept the stock olds lower A-arms, boxed them, and added a bracket to the arm to utilize the stock vette lower ball joint. Actually the geometry is correct, the way I fabricated it.
Grafting an entire vette front clip onto the original frame, would of made my wheel width way undersize, plus I would of had to keep the crappy vette C3 stearing system. Which I didn't want.
Now, as far as the measurements for the rack & pinions. This is the whole reason I'm asking for these measurements, so I can get the geometry correct. If no one can help me out, I guess I'll do some bone yard searches with a tape measure . But figured I'd give it a try here first.
As far as putting the car up for sale. I've never not finished a project I've started, and until it's correct, so that won't be happenin.

Wow! I guess this is kind of a tough room! I just signed up and was going to ask for details about installing R&P steering to an 83 olds cutlass chassis and suspension. This is a street rod project and I want to move the grille back pretty close to the crossmember, making R&P necessary. Perhaps someone could enlighten me about what type of rack I should use, getting the right length and tie-rod ends installed, and what I need to know about end lengths and mounting to make this thing steer properly. If it's rocket science, please be willing to say why without being abusive, OK?

Abusive?? O.K., I guess I'm guilty as charged. I probably was having a bad day or was tired of fielding newbie questions. I guess I was taken aback that someone would start a project like this and not have all the geometry worked out beforehand.

Don, it's not rocket science, but it is geometry and it must be pretty much spot-on to make the car handle and steer correctly.

On my last project car, a scratch-built frame and IFS under a T, I read every suspension book and booklet I could find. None of it made sense in the respect that nobody seemed able to offer up an answer on designing the whole IFS from scratch. Finally, I stumbled on a set of books authored by Carroll Smith and voila!!, it all fell together for me. The very talented Mr. Smith was the crew chief for Ford Motor Co. when they whipped Ferrari at LeMans with the GT40. If you haven't read Prepare to Win and Tune to Win, drop your wrenches and grab your credit card....
http://www.amazon.com/exec/obidos/tg...books&n=507846
http://www.amazon.com/exec/obidos/tg...books&n=507846

I believe it is in the back of Tune to Win that he explains how to set up your suspension with "paper dolls" to move the suspension and steering components through their paces on paper so that they are compatible with each other before you start making hard parts. That's what finally put the icing on the cake for me.

I proceeded to design and construct an IFS that had zero bump steer through 9 inches of total wheel travel, zero scrub and 3 1/2 degrees of camber gain on bump.

Once you've read Smith and understand him, go back and read the post at the beginning of this thread and let's see what goes through your mind

Originally posted by techinspector1
Abusive?? O.K., I guess I'm guilty as charged. I probably was having a bad day or was tired of fielding newbie questions. I guess I was taken aback that someone would start a project like this and not have all the geometry worked out beforehand.

That's were you are wrong. Why would I be asking for measurements, if the geometry wasn't worked out beforehand?

Get a tape and head for the boneyard. I don't know of any chart with R&P dimensions.

.......

Originally posted by techinspector1
Get a tape and head for the boneyard. I don't know of any chart with R&P dimensions.

Thanks, that's what I've already done. But, I did see a chart with the R&P measurements on them, I just can't find it any more.

You might try contacting these guys...

http://unisteer.com/home.php

Or searching for an OEM like TRW. It might be difficult to find
an appropriate unit AFTER the other components are done. Like Tech said, usually you design the fab items around the purchased components and in conjunction with the desired outcome (like bump steer, travel, turning radius, etc.)

mike in tucson

Originally posted by robot
You might try contacting these guys...

http://unisteer.com/home.php

Or searching for an OEM like TRW. It might be difficult to find
an appropriate unit AFTER the other components are done. Like Tech said, usually you design the fab items around the purchased components and in conjunction with the desired outcome (like bump steer, travel, turning radius, etc.)

mike in tucson

I planned on, and am currently using the stock items, even the original steering box. I am just evaluating the idea of possibly converting to a R&P unit, and if it would even be possible. So far, it doesn't look good, unless I go with one of those units that the whole body moves.

i assume you know where the tie rods needs to be for proper bump steer, if not here it is.

Originally posted by lt1s10
i assume you know where the tie rods needs to be for proper bump steer, if not here it is.

Yes, I used this when putting the upper A-arms in the car, and attaching the bracket to the 48 olds lower A-arms, for the vette lower ball joint, and still using the stock steering setup.
I haven't driven the car yet, but only get a small amount of wheel movement(toe in, toe out) while running the suspension through it's entire range. Which with air bags, I will only be using the bottom part of the suspension travel.
At this point, I have a R&P out of a late model Bonneville, I was looking into modifying, so the whole body will move, and the inner tie rods are stationary, so I could add a type of drag link on the outer part. I'm sure that makes no sense.

"but only get a small amount of wheel movement(toe in, toe out) while running the suspension through it's entire range."

How much is "a small amount"?? If it's over about 0.060", it's too much.

Originally posted by techinspector1
"but only get a small amount of wheel movement(toe in, toe out) while running the suspension through it's entire range."

How much is "a small amount"?? If it's over about 0.060", it's too much.

Through my suspension travel range, I can't detect any, but ..060" is hard to see with a tape measure . I am still setting everything up, and just got the engine and tranny in last weekend, and put some temporary cut springs in, to see how it does, as far as wheel movement, fully connected to the stock steering setup.