I'm considering swapping in a rack and pinion on my Astro Van. I found one that would work well, but the problem I'm having is people are trying to talk me out of it due to not taking the Ackerman angle into effect. I did some research on the large cloud known as the world wide web . And I'm thinking it's not all that important. It seems that it only comes into play when driving at extremely low speeds and turning at the same time.

So if I'm only meeting that criteria maybe 20 feet out of a day, why is it important? Especially with power steering.

Am I missing something here?

Also are there any good books on suspension that I could read that might apply to modern suspension?

You are correct that Ackerman steering geometry is most useful at low speeds, and it is most suitable for low-speed objects like wagons and carriages, where you want the minimum rolling resistance while turning. Ackerman geometry, along with solid front axles, continued to be used in cars up through the 1930s.

Today, most modern cars actually incorporate anti-Ackerman geometry into their steering. The reason is that during a turn at above about 10 mph the outside tires are more heavily loaded than the inside tires, and thus the outside tires need to run at higher slip angles.

That said, I would highly recommend that you not change the steering geometry on a street-driven car. Steering, like brakes, is a safety-critical item. If you must replace the steering gear, replace it with parts functionally and dimensionally identical to the OEM parts.

[This message has been edited by Marvin McInnis (edited 10-16-2007).]

Thanks for the reply. With the research that I've been doing on this rack, I have found that it is possible to mount this rack to my cross member and have the exact same angle to the spindle with the tie rod ends. This rack will also allow the same travel as stock. The only thing that would be different is I would be eliminating all of the slop in the steering do to losing all of those dang idler/pitman arms. If you have ever driven an Astro Van you know what I'm talking about. I believe a rack and pinion would be a hundred times safer than that stupid ball and pintle steering that is going on now.

The thing I don't get is if all dimensions and angles remain the same why should there even be a problem with Ackerman to begin with.

edit: If anyone wants to know what vehicle the rack is from it's a Mercury Mountaineer.

[This message has been edited by fieroluv (edited 10-16-2007).]

quote Originally posted by fieroluv: ...The thing I don't get is if all dimensions and angles remain the same why should there even be a problem with Ackerman to begin with.

quote Originally posted by fieroluv: Am I missing something here?

If I understand what I read (which was, admittedly, very little) Ackerman angle seems to be a function of the arms that steer the knuckle, to which the tie rods connect.
The rack shouldn't have have any noticeable effect on this, as long as it's mounted between the tie rod attaching points on the steering arms.
If you're really concerned about it, it seems like it could be corrected by moving the entire rack forward or backward just a bit.

I believe that one of the aftermarket specialty parts houses (Ecklers, perhaps?) is selling a rack and pinion retrofit kit for older Corvettes.
If it's not creating a problem for a Corvette, I can't imagine that it would for an Astro, either.

I wouldn't hesitate to proceed with your plans.

And thanks for sharing your ideas! Way to innovate!
Please keep us posted on your progress and results.

[This message has been edited by Raydar (edited 10-16-2007).]

quote Originally posted by Raydar: If I understand what I read (which was, admittedly, very little) Ackerman angle seems to be a function of the arms that steer the knuckle, to which the tie rods connect. The rack shouldn't have have any noticeable effect on this, as long as it's mounted between the tie rod attaching points on the steering arms. If you're really concerned about it, it seems like it could be corrected by moving the entire rack forward or backward just a bit. I believe that one of the aftermarket specialty parts houses (Ecklers, perhaps?) is selling a rack and pinion retrofit kit for older Corvettes. If it's not creating a problem for a Corvette, I can't imagine that it would for an Astro, either. I wouldn't hesitate to proceed with your plans. And thanks for sharing your ideas! Way to innovate! Please keep us posted on your progress and results.

LOL... yeah right now I'm just in the planning stage. My Fiero is numero uno on my priority list. First and foremost I must get the Fiero on the road. Then I'm rebuilding the steering and suspension on the van.

I'm not breaking new ground here. I've seen a couple other Astro vans with this setup. And have driven one of them and I must say the difference is phenomenal. as soon as I got behind the wheel the first thing out of my mouth was I am definitely doing this to mine.

BTW: other parts needed is the intermediate shaft from the Mountaneer as well as one from a Citation. And the tie rod ends from a late model Camero.

Is there an Astro forum?

believe it or not yes, the person who had the van with the rack pointed me to the forum. He said there was a good write up on it on there.

edit for linky: http://astrosafari.com/

[This message has been edited by fieroluv (edited 10-16-2007).]

quote Originally posted by fieroluv: as well as one from a Citation. And the tie rod ends from a late model Camero.

If I understand it correctly, the CAMERO was made from 1976 - 1982.
Earlier and later Chevrolet F body cars were called Camaro.
Seriously, this conversion sounds like a common mod, so you aren't exactly treading on new ground here.
I'd say go for it.
Good luck!

Yeah, I had a brain fart and just stalled, when it came to trying to spell "CAMARO". I new it didn't look right, but went with it anyway.