plymouth rack and disc conversion (my version)

so the factory drums where not cutting it anymore, so a disc conversion was in order. wile i was in there i wanted to address the fantastic factory horrendous bumpsteer steering. and after reading on the some of kits i decided to just build my own. it did take a couple of weeks working on and off and with the 3 yr old yelling at me to turn mickey back on.

end result is a pedal that feels exactly like stock but it stops better and no fade. i use the larger bore because the stock pedal is 6.6 to ratio and i didnt want a soft feel.
on the rack, the steering is a million times better handling than stock so far, i am going to hook up the power to it. just waiting on some fittings and some time to mount the pump.

now for the best part, i ended up with less than 1/8 total bump steer at full suspension cycle. and i can probably tweak it to get that out, but im not going to anytime soon.

on the hubs i did have to turn down hubs for the rotors to slide over.

on the calipers, i did have to massage them with the grinder and run a 1/4 spacer to get the stock 15" wheels to clear.

the rack, was a rebuild from the local parts house. stander ratio power unit. the sector shaft is pic-n-pull pieces. rack end is from a chevy mini van which was the same as the cavalier on one end and had female 3/4 dd on the other end. now on the column end, is from a jeep cherokee. it had 3/4 male shaft and a splined aluminum joint that i drilled out to 7/8 to fit on the stock column shaft.

so here is the rest of the parts list
97 sploder rotors and calipers
steel braided -3 brake lines (because i had it all on the shelf)
89 f350 master (because i had it on the shelf) 1-1/8 bore
88 cavalier rack
speedway imca tie rods 19-1/2"
pinto bumpsteer kit
and some better quality 5/8 heims from ruffstuff
bolt patter drill jig from Rotten Leonard
doorman wheel studs from a explorer


so here are some pics

now i didnt use the copper that is on the master here, i ended up gettin some plastic fitting to connect the hose to.





here is the beginning of the caliper brackets/steering arms

 

now on to the rack

 

the bracket up front of the rack is their to keep the other bracket that is bolted to the rack from rocking up and down. it has a skateboard bearing on the top and bottom. on the final assembly i put the inner tierods on the inner holes.

the ackerman turned out perfect too, absolutely no tire noise at full lock and i didnt lose any steering with the rack.

 

Very nicely done!

 

WOW, that's a GREAT job very, well thought out!
KK

 

Awesome! I've been hmming and hawwing about doing this type of conversion on my wagon. I love the relatively tight turning radius and have been worried about losing it with a conversion like this.

I'm swaying more and more towards doing this mod along with new front springs and a realistic sized front swaybar.

NAES

 

Looks good, only things I saw was:
On the upper bolt for the caliper mount, did ya' have enough thread engagement into the nut?
And, the brake hose looked as if it might crash into the frame at full lock.
Of course, these could have been just mock up shots as well.

Bet it makes one hell of a difference driving it!

Did you lose much on your turning radius?

 

you should sell a kit! have you driven it much since all the mods? is that a Cherokee sway bar? aerostar springs? i like the caliper bracket/steering arm combo. it eliminates so interference issues.

 

A very interesting setup and mostly better thought-out than a lot of the GM J-car center-steer rack conversions.

My only quibble would be that that open roller arrangement for supporting the center link will likely cause you some grief over time, though enclosing/crud-proofing it would likely take a whole lot of thought.

edit - the thing that comes to my mind would be, instead of using a roller on the flat plate, would be to put a notch in the web of the center link, and have a stainless shaft that bolts into that notch, and instead of a roller use a delrin sleeve that slides on that shaft, then you could use something like a very small rack boot over either side...

...but, as I said, that'd be a whole rumpload of work.

 

It looks like he got the length of the steering arms right for the rack throw, which will make all the difference.

 

I have a fifty Chrysler and have been wondering how to put a rack under it . Great fab work!

 

cherokee swaybar and aerostar springs made a huge difference in handling




the only thing that i dont like so far is that the steering has a heavy feel at center wile driving. almost like it has way to much toe in. like it has tons of caster but doesn't track perfectly straight. it is setup now with 0 toe in/out. but i think some if it could be the fact that bearing on the bottom of the column is still a touch tight and that the rack doesn't have any fluid in it, so it could be causing some drag.

granted i did the alignment in the driveway with 2 levels and 2 tape measures, so i should check it again to make sure that its still good.

and i think that after it get fluid in it, it should move a free up a little.

but the greatest part is that when you hit a bump on the freeway, the steering wheel doesnt rock a 1/4 of a turn from the unequal length/height tie rods and steering arms

 

all mock up pics, the hose got turned up at the caliper and the bolt got changed on finale assembly.

no turning radius was lost, the outer tie rods are mounted closer to the kingpin than stock

 

i originally had a rubber bushing with a delrin sleeve and a rod that slid though it. but impations got the best of me and the bearings went on. if you look close that bracket is very unfinished because it wasnt my first choice, but the fastest choice. i wanted something that i could keep lubed. but this was fast and easy for now.

 

Excellent job; I did the Explorer brakes on my 51 but kept the stock steering. May have to rethink that.

 

Scotty approved!

 

very nicely done. I will have to study your set up more. You have put a lot of thought into this. Good job!!

 

Looks good - echoing the others who say you should sell a kit. But I think there are enough year-to-year differences, and model differences, that it would need to be more of a roadmap and set of templates.

What are the materials for the beefy disc brake bracket bottom - is that an inch of solid steel?

 

The main plate is 3/16 and the thicker plate and steering arm are 1/2

 

As long as you don't get any crud built up between the plate and the rollers it should work, but I think you will want to keep an eye on it.

I'm also personally not wild about exposed unsealed rod ends on a driver, I've run them and I'll end up doing it again but they seem to have a limited life. Still, that's a minor quibble and not really a safety issue, looks like the nuts you're using are big enough to catch the body if it does somehow pound loose...

 

the heims that im using are about the strongest you can get, i have no worrys about them. they are teflon lines and have been cryo'd. i have the same ones on the back of my f100 and they have been there for 3+ years and over 50k and are still as tight as the day i put them on. i use the same ones on my crawlers and haven't had a failure yet.

 

Interesting stuff!
Thanks for posting it.

 

I design machines for a living, that is one georgeous setup. The rack was an unfamiliar form which looks like it is adequate in size, most of the newer ones have to counter driven wheel loads as well, thanks for the clear pics to show it step by step.

 

It's typical of the GM J-car platform from the '81 Cavalier through Grand Ams, Aleros, etc. up into the last decade. The same basic design was also used in various Opel/Vauxhall Cavalier/Vectra-platform cars sold outside the US, the only one of those that got into the US was the '94-03 Saab 900/9-3 (the first year of which got a ZF-made rack of similar configuration, from '95 on they were Delphi racks but a little different from the US J-car Delphi rack, dimensionally identical but the input shaft is a different size and the pressure cylinder is smaller in diameter.)

There's only a few other production cars I can think of that use a center-takeoff rack configuration and most of them are a somewhat odd front-steer configuration with the tie rods pointed forward from the firewall at about a 30-degree angle, so the tie rods move the wrong way: lots of VW/Audi products with north-south engines and the big FWD Renault/Chrysler products from the '80s up through the end of the LH cars (the Dodge Intrepid, Chrysler Concorde/300M, Eagle Vision were developments of the Renault R20/R30 seen in the US as the remarkably uninspired Dodge Monaco and Eagle Premier.)

 

this is great work..Im using a rach on my chever..while mine is a front steer it works the same way.. the skateboard bearings are the key.. I been playing around with ideas but yours will work perfect.. thanks for the idea

 

so, today i hooked up the power. i used a 94 s10(i know un-hambworthy) pump because i had it layin around. and its the lowest psi sag pump that they made. then i used 16mm to -6 and 18mm to -6 fittings and some build your own fittings and hydraulic hose.

so now with the results,
it made a world of difference, it took the heavyness at center off of it.

other than the window rattles, it drives like a brand new car.

one thing i did notice, is that one steering left to right, is the brackets that hold the rack flex a tad side to side. they actually twist the frame, not just the bracket. so anybody running a rack conversion, have somebody steer l to r and see if your frame flexes. i would imagine that it does a little.

so with that said it will go back on the rack and i will throw a brace on it.



jeff

 

Very interesting conversion would like a setup like this for a 50 Ford car.

 

Seals-It washers from Summit will allow you to put some protection on the rod ends. They have rubber skirts that encompass the ball to keep dirt out.

 

What year/model is the front sway bar? I've heard Cherokee and Grand Cherokee, but I don't know the year or how much of the Jeep links are needed.


Posted from the TJJ App for iPhone & iPad

 

Mine is from a regular Cherokee, and the end links are some off the shelf aftermarket ones

(Edit) the year of mine was a 90 but they are the same on any xj jeep