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Discussion Starter #1
Can't seem to get the bumpsteer straightened out on this F&@KING thing. I thought I had everything perfect but wanted to map it out on the floor before fully welding the rack mounts in. I'm still getting 3/4"+ of toe change on ONE side in only 4" of total suspension travel. WTF?? Rack is mounted 1/2" below the centerline of the lower a-arm bolts (its level and perfectly centered), and tie rod is level AND parallel to the line from the a-arm bolts to the lower ball joint.

Its a 68 Firebird, front Flaming River rack stock length (24.5"-25" c-c on inner pivots), Heidt's 2" drop spindles, TRZ billet steering arms, outer tie rod ends and tubular a-arms.

Only thing I can figure is the rack needs to be shorter by about 1" on each side because the lower a-arm bolts are only 22-1/2" center to center. I don't know anyone that runs a shortened rack on a 1st gen F-body though?? Doesn't seem 2" would make much difference though.

On rebound, it toes out to a point then starts to toe back in at max travel. Then on compression it toes in. According to Dave Morgans book this means the rack is too high and too long. I moved it down 3/8" and added a 1" spacer to the steering arm and it cut the toe change down to about 1/2". Doesn't seem right though that the rack would want to be even lower yet.

Somebody please set me straight on this thing before I drag it out in the field and make it a REAL FIRE-bird using gasoline!

Thanks!

Craig
 

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I didn't have to shorten mine, but did have to use a spacer out on the end of the rack where it bolts to the steering. Believe it was a 1" or 1 1/2" spacer. I can check when I get home. Mine does not have dropped spindles though.

Don't know if this pic will help or not but it's the only shot I have of the front end rack and geometry. Car goes straight as a string though.

 

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7.86 @ 8800DA 3365lb 275s
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sounds like the rack is to wide. the lowered spindles aren't the issue it's irrelevent all that is (or should be) moved is the spindle pin. the pivot point's of the inner tie rods with in an imaginary line going from your upper control arm pivot points and you lower control arm pivot points the lower you make the rack the narrower it will need to be.
 

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7.86 @ 8800DA 3365lb 275s
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Thanks Justin. Ever narrow a pinto rack yourself? Wondering if I can just take it apart and cut/weld it to shorten the inner tie rod lengths?
i've never done a pinto i typically do mustang II but from what i'm told the pinto's are actually easier. pull it apart unthread the outer tierod and cut and rethread. i pay a local shop to cut mine for me (they charge me $10 to cut and thread it) then i reassemble the whole thing (after cutting the housing down first)
 

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Discussion Starter #6
I assume if I shorten it say 2", then the input shaft has to move over 1" towards the pass. side right? You have to shorten it all off the one side correct?
 

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What year pinto rack do you have? 71-72 pinto rack is the one you want for your car.

 

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Discussion Starter #9
Thanks Justin. We'll see how much the rack length helps tonite. I swear, sometimes I wish I had a simpler hobby like building airplanes or something.

Its an aftermarket one from Flaming River, same dimensions as the Wilwood one in the diagram.
 

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The Pinto racks are pretty easy to narrow. You just need a lathe to shorten them and turn them down to the proper thread size. Then just cut and reweld the outer housing. I may be a little slow at it, it takes me about an hour. Let me know if you have any problems I'm not too far from you.
 

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I put a Flaming river rack in a 1st gen S10 and it bumpsteers like a bastard too. Should have stuck with the stock parts. Really frustrating!!!
 

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7.86 @ 8800DA 3365lb 275s
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I put a Flaming river rack in a 1st gen S10 and it bumpsteers like a bastard too. Should have stuck with the stock parts. Really frustrating!!!
probably same issue to wide. in most cases you can't just throw a rack into something it will need to be modified. and the brand doesn't make any difference (if thats what you were saying)
 

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7.86 @ 8800DA 3365lb 275s
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What year pinto rack do you have? 71-72 pinto rack is the one you want for your car.

haven't measured a first gen F-body in a while but i bet that 24.5" tie rod pivot dimension is still to wide.
 

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EFI/N2O JUNKIE
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Wow! I guess I got lucky with my 3rd Gen F-Body. Yes, I did have a LOT of bumpsteer issues but I was able to resolve them with spacing the tie rod end away from the steering knuckle. It did take a lot of time and was a pain in the ass, but it came out perfect. Patience and persistance is the key for sure, good luck!

PS: I do not have 0 bumpsteer, I still had a swing of around 1/4", but the car goes perfectly straight and has been 154mph with no wandering-around at all. Don't forget, as long as the toe is where it needs to be, or very close, with weight on the tires, that is what really matters.
 

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The big thing that REALLY matters is that it does not toe out during braking when the suspension compresses. This is what crashes race cars! Also RJ Race Cars sells an already narrowed pinto rack if anyone does not want to narrow a stock dimension one. Be careful...............Toni
 

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You should call up Kim at smithracecraft im pretty sure some of your problem is that the rack is mounted to low...if u center it up with the centerline of the lower a-arm bolts you will prolly see an improvement...also im pretty sure a rack for 67-69 camaro/firebird is supposed to be 24in. so you may shorten yours 1/2.
 

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Craig can you move the rack up? I went out and looked at mine, it looks like it's the same height as the lower a-arm bolt centerlines. Maybe that will help.... I didn't have to cut my wilwood down.

Yeh, I did one on a 68 not long ago and it is mounted the same height as the lower a-arm bolts. Car drives straight as a string. I don't remember even needing to narrow that one. But, I do narrow most of them. Hard to remember exactly.
 

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EFI/N2O JUNKIE
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My rack needed to be moved up from where it is mounted but I couldn't because of the oil pan so the correct amount of spacers on the outer tie rod ends fixed my problem. Now, I wasn't doing this conversion by myself, this was a complete front end setup I bought from AJE Racing. I would prefer NOT having so much space between the outer tie rod end and the steering knuckle, to me that is a lot of stress on that 5/8" bolt. If you have the room to try it, move the rack up and see how the toe-change reacts to that.
 

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7.86 @ 8800DA 3365lb 275s
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did a quick drawing hopefully it makes sense...lol the inner tie rod pivot points should be somewhere in the imaginary line between UCA and LCA pivot points the higher the rack the wider it needs to be the lower the rack the narrower it needs to be. most of the time the engine/chassis...etc dictates where the rack will have to be located and thus the rack usually needs to be adjusted to fit. i don't think you will notice a small variance but anything more or less then a 1/2" is to much IMO.
 
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