So I've recently come to the realization that a fox car equipped with '96+ spindles and a stock k-member will have an uncorrectable amount of bump steer.

Err -- exactly how did you come to this realization?

Is the bump-steer exhibited by the '96+ spindles really that significant to the point where the car isn't safe to drive on the street?

There are hundreds of Mustangs out ther running Fox K-members and Lase SN95 spindles with no issues at all. Many of these have never been bumpsteered at all.

I ran this combination on my '88 GT for years with no problems at all.

Install your spindles, align it, get the car bumpsteered by someone who knows what they're doing, and then get it re-aligned (changing the spacer stack changes the toe-in slightly.)

There's nothing inherently unsafe about a properly-installed 96+ spindle on a Fox mustang. Sheesh...

 

Err -- exactly how did you come to this realization?

From doing a search on this topic in this forum. All the info was kind of wishy washy so it had me confused as I'm sure there are plenty of people out there running '96+ spindles and driving their cars daily so, I'm not entirely convinced. From what I understood no bump-steer kit, alum. offset rack bushings, or significant amount of caster could solve the bump steer issue and that a MM/Griggs K-member was the only remedy... I also remember in one of the posts, of the threads I had read, had a direct quote from MM's website saying it was an impossible fix on a stock K-member.

 

Uhm, that wasn't my impression. The way I understood it, the outer tie rod end wound up in the same location as the arm on the spindle thus the bumpsteer problem.

That's why I first bought the 94-95 spindles when I did the 5 lug swap and only recently bought the '96-'04 versions for the planned Mathis modded k-member swap.

To wit:

http://forums.corral.net/forums/showthread.php?t=716488&highlight=hidley+bumpsteer

and specifically

http://forums.corral.net/forums/showpost.php?p=6065379&postcount=36

No, I'm talking about the 94/95 spindles with the steering arm that is bent UP. With this spindle on Luke's car, about 0.10" would need to be machined off of the bottom of the steering knuckle to put the tie rod at the optimum height. If you used a 96+ spindle on his car, the center of the tie rod and the center of the steering knuckle would need to occupy the same space since the steering knuckle on the 96+ spindle is 1" lowered from the 94/95 spindle.

The goal is to have the tie rod and the control arm roughly parallel when viewed from the front of car. Parallel to the control arm means parallel to a line that goes from the inner control arm pivot to the geometric center of the ball joint. The control arm is a suspension link. The only thing that matters from a bumpsteer standpoint is the line that goes through the two pivots of the link. The actual shape of the control arm itself between the pivots is completely irrelevant. Do not look at the body of the control arm and try to make that parallel to the tie rod. The body of the control arm shape is not parallel to the line through its pivots. The ground, or the angles any suspension parts make to it, has absolutely nothing to do with bumpsteer behavior.

Just sayin' is all...

 

Uhm, that wasn't my impression. The way I understood it, the outer tie rod end wound up in the same location as the arm on the spindle thus the bumpsteer problem.

That can happen, but it depends a lot on what other parts are on the car and how tolerances have stacked up on all the suspension bits. Predicting bumpsteer and where the outer tierod pivot point needs to be is almost impossible.

When I ran my factory K-member and a '95 spindle, I had a HUGE spacer stack on my bumpsteer kit (about 2" or so.) One of the reasons I moved to the '96 and later spindle is to shrink that spacer stack to lower the bending loads on the bolt.

Making a blanket statement that '96+ arms are dangerous on a factory K-member simply isn't true.

 

I run 04 Mach 1 spindles on my car and have no issues. Car has not been bumpsteered yet, but I've driven it on the street, autocrossed it, and open-tracked it with no problems.

 

I am bumpsteering my 84 Mustang with the stock k-member and 96+ spindles. I took some base line numbers, and I am seeing .020" toe out in the first inch of bump. This is with 3.7' Caster, and I have not begun to play with the shims yet. I am fairly sure the MM instructions for the bumpsteer kit says anything less than .020" per inch is acceptable. I will most likely not be able to have a 0" of toe change per inch of travel, but I am ok with that.

 

FWIW I found that a little toe-out on bump "calms" the car a little. I have (IIRC) just under .020 total toe out on each wheel from ride height to full compression.

 

Well this is very good to know. Thanks guys.

 

Tomorrow I am going to start my shimming, and hope to be less than the .020" for 1" of travel.

 

Cello, one thing to consider is the 5 lug swap, especially with the 96+ spindles will push your wheels out past their stock locations (as it sits now). Combine that with the .75" forward relocation the K member adds in and your '88 wheelwell might get a little close for comfort. On my '91 with 9" wide Cobra R's there was NO way I could drive the car as-is, so I'm in the process of fabricating some adjustable control arms to position the wheel inboard an inch and back the .75" if I want to. Now my suspension can compress without worrying about tearing off the fender.

 

The wheels sticking out isn't too much of an issue with me. I don't think they will stick out that bad and I'm more concerned with the handling than looks, I think they'll be fine. The k-member relocation might be an issue but I'll cross that bridge when I get to it.

 

About post no.3, This line would pass through the center of the ball in the ball joint to the center line of the bolts of the lower control arm conecting it to the frame correct? Then the a line should pass from the steering rack inner tierod to the outer tierod ball center line and be parallel with the line from the ball joint?

 

So I've recently come to the realization that a fox car equipped with '96+ spindles and a stock k-member will have an uncorrectable amount of bump steer.

 

:lol: Hey, I'm just going by the info I gathered from reading all the old threads on this subject. I'm just trying to find the truth. Many people seem to prioritize/obsess on this bump steer issue regarding these spindles.

 

Would not a 94/95 stock k-member work better with the later spindles than a pre 95 k-member? Those stock k-members are easy to come by for little money, that could be a short answer until you get to an aftermarket unit.

 

Something else to consider: The year of the Stang you're talking about. Beside the obvious shorter k-frame on the pre-87's, between 87 and 93, Ford had "fun" moving the strut tower, and ?FCA? mounting points (less squat), and so on.

So, when you're talking about something as sensitive as bumpsteer, you get into
o The year of the car
o The spindles
o The wheels
o The specific tires (model and sometimes even the year they were made)
o Alignment

All of those effect the front suspension geometry, and the "fit" of the tire/fender.
BTW: As I always say: Get the MM bumpsteer kit!
________
Joe

 

Yea, Chuck S. has a bit more of my money.

I bought the SN-95 bolt-through kit for my future plans. There was a backorder so my kit was delayed by ~1 month.

 

Still trying understand how he came to justify calling it dangerous. I guess he should never drive in the midwest because of all the potholes which can do more than bumpsteer ever could. Here you think a little bumpsteer scares you, go drive a 60's vehicle with stock parts. Its normal for you to go straight you have to constantly move the steering wheel. If we all wanted somthing perfect we would all have to sell POS fox bodys and go buy somthing else with better technology. But were all hotrodders, were taking somthing and trying to push its limits. It ain't perfect, it gets close to the mark. Were cheap and were men with big arms able to reel in our mighty steeds during a bump issue. Maybe you need to sell your POS and go buy a BMW for your girly arms.

Why not first go work on your car and see the results. Before trying to theorize the outcome Mr. Gore. It must be great to take everyone elses here say and make some blanket statement thats total BS.

 

oh boy...

You've seem to have taken my questions out of context. I just didn't understand why things like I've mentioned were being said about these spindles. I have a set of '02 GT spindles that I plan on running regardless of the out come of whether they are good or not. The impression I got from reading PREVIOUS threads showed that there was a huge concern with these spindles and I didn't really understand why, hence why I made this thread. If you noticed I put a question mark at the end of my title which is hardly a blanket statement regarding the "danger". The part where I mention the "uncorrectable amount of bumpsteer" came from the consensus of reading several threads. If they're all wrong then I'm very glad I made this thread regardless of being criticized as I'm more informed, isn't what this site is all about? Hey if you feel the need to criticize to get your point across thats fine by me, I'm just not sure if anyone else would take it the same way.

 

So, which spindles are more desireble on a fox Mustang...94/95 or 96+? What are the up's and down's of each?

 

Depends on our combo. Stock Fox or 94-95 K-member, stock balljoints, 96+ steering arm will likely get in the way and a 94-95 spindle is preferred. But add X2 balljoints to the mix, and 96+ will likely work better.

 

You are saying that if you have a stock fox with a stock k-member go for the 94/95 spindles.

If you have a stock fox with a stock k-member and X2 balljoints...get the 96+ spindles.

What is the advantage of the 96 up spindles over the 94/95?

 

Other than a slight change in track width, the key difference is the placement of the steering arm. The 94-95 spindles place the outer tie rod end attachment point much higher than the 96+ one does. If you use 96+ spindles on a stock 5.0 K member the attachment point can end up smack where you want the tie rod ball to be.

 

They give you a narrower track width and you don't need the x2 balljoints.

I have 96+ (99 spindles actually) stock kmember, stock a-arms, stock balljoints with a m2300k spacer. With 18x8.5 BBS RK's with a 245/40/18 and have plenty of fender clearance. I also run the thru bolt MM bumpsteer kit and with the gauge the bumpsteer is within acceptable limits.

 

Its just with our hobby people starting throwing around the word dangerous. Some assistant to some senator is going to find this thread and find a new milk box to stand on.

 

umm... ok man. I'm an assistant to Barbara Boxer and will be forwarding this thread to the senate uberserver. We will then require annual smog checks and bumpsteer measuring. I'm getting off my milkbox now, so its safe to remove your tin foil hat.

 

 

To answer post #12. The exact proper geometry to minimize bumpsteer is to have the tie rod axis pointing directly at the instant center of the front suspension in roll, when the car is at ride height. If the tie rod and lower control arm are parallel, with a strut suspension, the tie rod will be approximately pointing at the instant center.

There are two main concerns with bumpsteer.

1) During pure cornering, with no bumps in the road. If you turn the car to the right, entering a corner, the body is going to roll to the left. This puts the left front suspension in the direction of bump travel (compression). There is NO bump encountered by the car, but the direction of suspension travel is called bump. If the bumpsteer curve is such that under bump the toe goes more negative (toe out), that is just like someone turning the steering back to the left a little bit as the car rolls into a right hand corner. This is called roll understeer. The car is going to turn a larger radius corner the more it rolls. This is a stable condition as the car tends to want to go straighter.

If the bumpsteer curve is such that under bump, the toe goes more positive (toe in), that is like someone turning the steering more to the right as the body is rolling to the left in a right hand corner. This is called roll oversteer. The car is going to try to turn a smaller and smaller radius as it rolls. Notice that this situation has positive feedback. Once the bumpsteer starts to turn the wheel to the right more, this decreases the radius of the corner. Since the cars velocity is constant and the radius has decreased, the g force has gone up. The increased g force causes more body roll, which causes the front tire to turn more to the right which causes more g force......until the car spins.

For this reason, automakers design cars so that the bumpsteer curve always goes toe out under bump, to some degree. This keeps the car from becoming unstable in a corner and spinning. If you install 96+ spindles on a Fox Mustang with a stock k-member, the bumpsteer curve will have a lot more toe out under bump than it had with the stock of 94-95 spindles. From this standpoint it is "safe".

2) During a one wheel bump and no cornering. Under these conditions, it doesn't make much difference whether the wheel goes toe in or toe out under bump. The car is going to dart, when it hits a bump. If it has a lot of toe change for a given amount of bump travel, it is going to dart a lot. Using 96+ spindles on a Fox car with a stock k-member is going to cause a lot of dartiness compared to the stock or 94-95 spindle. From this standpoint, it's not "safe".

I've just given two very simple examples here. There are obvious other combinations of vehicle motions to consider such as bump and roll, bump and braking, braking and roll, etc. The less bumpsteer the car has, the better behaved it will be under all of them.

Sometime in the near future I'll be posting a lot more information on this subject.

 

Thank you for the explaination! Please write more!

 

Well said Jack!