I need to know how where the rotor face is so I can tell if there is room for the outer tie rod ends with those brakes. It is easiest to just measure from the center of the grease Zerk on the lower ball joint over to the rotor and use that as a reference. It should be somewhere close to an inch and a half?
Home built rack and pinion+ coilover build.
- Thread starter gregsdart
- Start date
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I pirated this image from another rack thread;
http://www.forabodiesonly.com/mopar/attachment.php?attachmentid=121083&stc=1&d=1263334590
To me this is a good way to understand where to start from. The problem with this diagram is it doesn't address Ackerman angle. To get that, As I see it you would just shift both inner and outer tie rods left or right of those two lines. The length of the steering arm is going to dictate to some degree how far you go also as it is affected by the line that Ackerman falls on; tie rod end, lower pivot, center of rear axle. The whole deal can be a real can of worms to get it perfect. The first measurement that should be addressed ( just chose what I thought would be close) is the length of the steering arm needed with available rack travel to give full steering radius. Using the stock dimensions will decrease steering radius significantly. I am at about four inches cent of ball joint to center of tie rod end.
One thing this diagram pointed out is the need for as high a rack mount as you can get, to try and keep from narrowing the rack.
http://www.forabodiesonly.com/mopar/attachment.php?attachmentid=121083&stc=1&d=1263334590
To me this is a good way to understand where to start from. The problem with this diagram is it doesn't address Ackerman angle. To get that, As I see it you would just shift both inner and outer tie rods left or right of those two lines. The length of the steering arm is going to dictate to some degree how far you go also as it is affected by the line that Ackerman falls on; tie rod end, lower pivot, center of rear axle. The whole deal can be a real can of worms to get it perfect. The first measurement that should be addressed ( just chose what I thought would be close) is the length of the steering arm needed with available rack travel to give full steering radius. Using the stock dimensions will decrease steering radius significantly. I am at about four inches cent of ball joint to center of tie rod end.
One thing this diagram pointed out is the need for as high a rack mount as you can get, to try and keep from narrowing the rack.
Sorry...but you ackerman thinking is incorrect...
Please look at it this way....extend an imaginary line from the center of the rear axle housing thru the lower control arm ball joint....whether you are engineering a front or a rear steer system, the outer tie rod should fall on that line.
You are correct regarding the length of the steering arm...it drastically effects the turning radius.
Keeping it real!
With the brakes being assembled and on the car the Dust Cover gets in the way big time. The best I could come up with was 1.035" from the inside face of the Rotor to the approx. center of the Zerk. Blast me for using an angled Zerk. Wish it could be more accurate......
Bob
Bob
Maybe I chose the wrong terms to describe what I meant. The imaginary line that runs through the center of the rear axle, then the center of the lower ball joint, then the tie rod end for proper Ackerman, doesn't change. But as the length of the steering arm changes, it affects the position of the tie rod end because on a front steer it has to be further outboard to stay on that line the longer the steering arm is. That is one of the reasons I said the length of the steering arm needs to be chosen first. To establish one of the axis the tie rod end will have to be on or close to.
I measured for total toe today, not just one side. I got very close to zero toe change, but it still toes in at both top and bottom a bit, showing the need for even longer tie rods. The rack is definitely going to be shorter, At least four inches shorter or 21 total inside to inside tie rod ends. I may go twenty, as there is a ready to go unit built on 20 inch centers. That extra 1/2 inch tie rod length per side out to take care of the little bit of toe in at the top and bottom of travel.
Thanks for the measurement RGP266
I don't see a stock 73 up disc brake setup having enough room with the measurements of only 1 inch+ to allow for Ackerman . If I figured it right, there would be zero Ackerman with the tie rod right up against the rotor, or 1/8 inch away. Also, the rack would need to be very narrow at about 19 inches. The one in my racer with zero Ackerman is 18.
I put in the narrowed rack, and it helped get the bump steer real close, like zero for four inches of travel. The problem is, the fat Mustang tie rod ends won't clear the Wilwood street brakes at the proper tie rod length, so I am going to a race type high angularity rod end kit, probably from ART. I didn't want to run rod ends, but to get perfect (or very, very close) bump steer and Ackerman that is real close, it has become a necessity. The rod ends will be right up against the rotors, within 1/8 inch. It looks like the Ackerman will be a touch less than stock. I want it to be about 75 to 90 percent of what it should be, but never more, which works out perfect with the 5.125 inch narrowed rack I put in. Bump steer is best if it toes out a touch at the upper and lower limits of travel, (extra long tie rod) not good to have it toe in. If the car toes in , then in a hard turn the car turns more than the steering input, not a good deal. A slight toe out is preferred by Herb Adams, The Chassis book. When I say toe out, I will tolerate and extra 1/8 to 3/16 inch at the ends of travel, on the bump part of travel (outside tire in a hard turn). The tie rod ends need to be about 4.5 inch (maybe a bit longer) from the ball joint center for correct turning radius. They will be about three inch below a line through the control arm bolts, depending on your rack placement. The distance from the center of the ball joint (a front rear parallel line)will be out about 1 inch outboard for 100 percent Ackerman, I can get to about 3/4 inch. I hope this helps. I have to put this whole project on hold for a long time, but will resurrect it when I install the whole deal next summer. Feel free to email if you have questions about what I have done. Greg
gregsdart5547@yahoo.com
gregsdart5547@yahoo.com
Here are some pictures with something to go by. The first two photos are of my race car front suspension. You can see that the steering arm is less than 5 inch from center of spindle to tie rod end. I hooked the tape to the far side of the castle nut on the lca. The second photo shows how much room there is with race Wilwoods for proper tie rod location. You can go too far and get too much ackerman angle if you use too long of a rack.
The aluminum square in the next photos shows that my street setup has a steering arm of approximately 4 3/4 inch. I am still thinking 4.5 inch is closer to full turning radius, based on the race car setup. On the race car I have over four turns lock to lock, more than stock. I think the extra steering wheel turns(4 1/4 instead of 3 3/4) is due to the tube being too short when I put the race car rack back together. So if anything, the arms on the race car are about right to a touch too long for full turning radius. I checked the race car and with 2 1/8 turns from centered I have full turning radius and the turning stop on the lower control arm is right at the bolt head.
The last three photos give you an idea of what a new Hemi with SRT8 jeep manifolds looks like in an early A. It fits, but is very close on the passenger side, and there is no/little room for exhaust coming off the manifolds.
The aluminum square in the next photos shows that my street setup has a steering arm of approximately 4 3/4 inch. I am still thinking 4.5 inch is closer to full turning radius, based on the race car setup. On the race car I have over four turns lock to lock, more than stock. I think the extra steering wheel turns(4 1/4 instead of 3 3/4) is due to the tube being too short when I put the race car rack back together. So if anything, the arms on the race car are about right to a touch too long for full turning radius. I checked the race car and with 2 1/8 turns from centered I have full turning radius and the turning stop on the lower control arm is right at the bolt head.
The last three photos give you an idea of what a new Hemi with SRT8 jeep manifolds looks like in an early A. It fits, but is very close on the passenger side, and there is no/little room for exhaust coming off the manifolds.
I finally got around to installing the coil over shocks. The QA1 single adjustable 304 shocks seem to be VERY stiff at the lightest setting. Also, the 400 lb springs are too much with the light early A. I think what it wants is a spring around 300 and 350, probably 350 would be the better for street. Medical issues have kept me out of the shop for some time. I have more issues to deal with, so this thread will drag out for a fairly long time. I hope to get the rack and pinion part installed next spring, maybe summer.
srixon4406
TURBO TOAD
Greg do you have part number for the QA1 coilovers you just picked up ive been looking at the afco 3850m but there pricey
Single adjustable ds304 on the shocks. They have about the right amount of travel. The top mount bolt needs to be down from the bottom of the stock mount about one inch to get the proper ride height with the coilover centered properly . 350 lb springs are about right. I was sold 450 pounders to start and the front was two inches too high with no preload on the shock platforms.
Due to health issues, racing another car and other stuff I haven't had time to get this deal installed, but will work on it in April.
The spring rate for my car is going to have to be reduced from 350 # to 300 or less, it is just too stiff for my liking. I prefer weight transfer over cornering. The stroker will drop the front weight another 40 lbs, most likely, and the battery is going in the trunk as well. I acquired a 6.4 plastic variable runner intake to go with the Apache heads, so front weight reduction will be at least 70 lbs.
Update! Finally!!
Got the new 408 in the 65 Dart post car, rack and pinion coil over combo is installed and working great! The 408 has about 470 hp in the car, dyno'd 504 hp but no fresh air in the car. Car has about 3600 stall, 3.55 gears. Definately impressed my buddy on the maiden voyage. Would break the 245 45 18s loose at 40 mph!
Got the new 408 in the 65 Dart post car, rack and pinion coil over combo is installed and working great! The 408 has about 470 hp in the car, dyno'd 504 hp but no fresh air in the car. Car has about 3600 stall, 3.55 gears. Definately impressed my buddy on the maiden voyage. Would break the 245 45 18s loose at 40 mph!
Shiny
Member
This is a great thread! Lots of info. I am thinking about building a strut front end for an A body. Hard to find info.
-Shiny
-Shiny
famous bob
mopar misfit
Interesting , following too !
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