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That is very true and could be the case, they also say that you should never run polyurethane bushings in your rear upper control arms. They say it causes severe binding but yet there are countless companies who sell uppers with the poly bushings. Probably trying to push their torque arm setups. They do sell great products tho, cant knock them for that.

I've actually heard the no-poly in the upper arms arguement before from other sources. I actually agree 100% with that.

I am not saying the 96+ spindles may or may not have a issue on pre-1996 k-members, i am just saying i would like to hear other sources claim the same info. So far i have not. i don't really have a view either way until then.
 

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Any of the 94-04 spindles can work. The 94-95 is just easier, and most of the people on this site are all about easy, I mean most of them don't even use the search function. Heck, I just put a 99 spindle on my 66. Tell me where you can read up on that....
 

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I only said what I said, becuase obviously you haven't read the sticky at the top of the forum, which should have been the first thing you read, before putting the sn95 spindles on the car ;)

Upon reading you find 2 options. A .330" shim, or putting new sn95 balljoints in your fox control arms. I chose the latter.
We had another thread going recently and several 93 Cobra R owners chimed in and informed that Ford used the spacer method on the R models,although they welded theirs to the spindle. But spacers dont pose a problem as long as they are either hardened or a similar steel as the spindles are made out of.
 

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Discussion Starter · #24 ·
i dont see the big probem using the 96+ spindles. the only diff would be the steering arm position which you may or may not have to use the bump steer kit. all depends when you see the travel in the suspension right? im not going road racing im only going in a straight line and it all is good whats the problem?
 

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Discussion Starter · #26 · (Edited)
i read it and read up on bumpsteer not really firmiliar with the steering geometry. so basically check the changes in toe thru out the suspension travel? is that how it works? sorry if im asking dumb questions or if the same question appears worded differently that the other thing i was concerned about if the car comes up the sus is fully extended then the strut might rub the LCA. i dont want to go grinding on the control arm but i dont want to spend 600 on new struts any ideas on what to chekc out or do?
 

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i read it and read up on bumpsteer not really firmiliar with the steering geometry. so basically check the changes in toe thru out the suspension travel? is that how it works? sorry if im asking dumb questions or if the same question appears worded differently that the other thing i was concerned about if the car comes up the sus is fully extended then the strut might rub the LCA. i dont want to go grinding on the control arm but i dont want to spend 600 on new struts any ideas on what to chekc out or do?
You really wouldnt have to go grinding on the control arms or replacing the struts. All you would need is the 94-95 spindles which have geometry that is closer to the Fox body geometry. The 96-04 cars had different control arm locations as well as a relocated steering rack which required a redesign of the spindle.
Just because something bolts onto a car, doesnt mean it will function properly.
 

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That is very true and could be the case, they also say that you should never run polyurethane bushings in your rear upper control arms. They say it causes severe binding but yet there are countless companies who sell uppers with the poly bushings. Probably trying to push their torque arm setups. They do sell great products tho, cant knock them for that.
:shakehead In the first case, they're not trying to "push their K-member", they're advising you which spindle to use if you're using a stock K-member and not theirs. In the 2nd case, they're not trying to "push their torque arm setups", they specifically tell you which stock replacement uppers to run instead of full poly, in the event you're still running uppers.

Here's the roll bind study their then-engineer wrote which has been published several times.

While bind is only one of many parameters determining the handling characteristics of a suspension system, it is useful information, and has been a subject of great debate on these message boards. As part of the research we did in developing our rear suspension system, MM has actually done quite a bit of roll-bind testing. I can offer some hard numbers for everyone to consider. I will define ‘bind’ to be any resistance to wheel movement in a roll situation that is not from the spring or sway bar.

Let me say that this information is not intended to be negative toward any particular system, but should be used to gain understanding of the way cars with different setups feel/handle. This information can help everyone to optimize whatever setup they may have.

Of the tests we have done, following are the tests relating to the rear suspension systems most often discussed. All tests are with the sway bar disconnected, cycling one wheel through 3” bump/droop as if in a roll situation. The results are organized in order from least bind to the most bind.

1) 4 Link - LCA with spherical bearings or rod ends at both ends / Stock UCA’s
6lb/in Linear
This shows the stock upper arms introduce 6 lb/in of wheel rate.

2) 4 Link – MM LCA 3 piece poly, spherical bearing / Stock UCAs
9lb/in Linear
This shows an additional 3 lb/in resistance from our 3 piece urethane compared to a rod end.

3) MMTA/PB – LCA with spherical bearings or rod ends at both ends
10lb/in Linear
Here we removes the 6lb/in from the UCAs, but adds 10lb/in due to lateral deflection of the TA during roll.

4) 4 Link – Stock LCA / Stock UCAs
11lb/in Linear
This shows that the stock LCA adds 5 lb/in of wheel rate, which is actually more than our LCA of case 2.

5) MMTA/PB – MM LCA 3 piece poly, spherical bearing
13lb/in Linear
Again illustrating an additional 3lb/in additional resistance of our 3 piece urethane compared to the rod ends in case 3.

6) 4 Link – LCA with 3 Piece Urethane at both ends / Stock UCAs
26lb/in Linear
Case 6 shows that the 3 piece poly (or any LCA) works best with a spherical bearing at one end. 17lb/in is added over case 2. Note that the effect of adding a 3 piece urethane at only one end adds 3lb/in. Add it at BOTH ends and the increase is 17lb/in… NOT 6 lb/in as one might expect.

7) 4 Link - LCA with delrin, spherical bearing / Stock UCAs
30lb/in Linear
This shows that delrin does not allow necessary angular deflection resulting in an additional 21lb/in over case 2.

8) 4 Link With PB - Stock LCA / Stock UCA
In the first 1” travel 47lb/in
Between 2-3” of travel 30lb/in Decreasing Rate
In case 8 & 9 the Panhard bar defining a new lower roll center is forcing control arms to travel a new path of higher resistance.

9) 4 Link With PB – MM LCA / Stock UCA
In the first 1” travel 50lb/in
Between 2-3” of travel 30lb/in Decreasing Rate

10) 4 Link – Stock LCA / UCA with rod end at chassis, stock rubber at axle
In the first 1” travel 63lb/in
Between 1-2” travel 39lb/in
Between 2-3” travel 20lb/in Decreasing Rate
Case 10 represents trying to locate the axle with a stiffer bushing configuration on the upper control arms. Since the upper arms need to have an effective length change, the rod end in this case actually creates MORE bind.

11) 4 Link – LCA with urethane at both ends / Stock UCA’s
67lb/in Linear
Case 11 is similar to case 6, but shows that a standard poly/poly control arm does not allow much angular change.

Keep in mind that the above information is with no cornering force on the axle. Therefore, there is a huge gap in this information if you are trying to correlate this data to how these systems would feel in use. I would say that the Torque-arm in case 3 & 5 outperforms any other case shown, although it does not have the least amount of bind in this test. We have begun to build a fixture that loads the axle laterally, as if in a corner, to THEN see how the bind behaves. Any system with a Panhard bar should have no significant increase in bind over what is already shown here. This predictability that a PB provides is why we recommend it on a 4 link (with the correct control arms) for people on a budget, or Solo II Street Prepared cars (not allowed to remove uppers). True, you are inducing bind in this situation, but that bind should not significantly change as you load the suspension laterally. When driving the car, the effective added spring rate (from bind) balances well with the new lower RC, and the improved stability and predictability. YES this is a compromise, but I feel it beats trying to locate the axle laterally with stiffer bushings. Obviously, if the pocket book or rulebook permits, the best thing to do is add a Torque-arm and remove the upper control arms. All this binding is also why you are able to add at least 50lb/in wheel rate to the rear when you add a Torque-Arm and remove the UCAs.

Ehren VanSchmus
MM Design Engineer
 

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I've actually heard the no-poly in the upper arms arguement before from other sources. I actually agree 100% with that.

I am not saying the 96+ spindles may or may not have a issue on pre-1996 k-members, i am just saying i would like to hear other sources claim the same info. So far i have not. i don't really have a view either way until then.
That's when it's time to ask yourself how many other manufacturers, not to mention "suppliers", have likely actually taken the time to make the measurements and post the information? You think Steeda would do it? Maybe. Maybe. They're more likely to say "it works, trust us". Think Griggs would do it? I would have thought so but they maintain a lower profile. UPR? AJE? Granatelli? Riiiiight.
 

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how are other people getting away with using 96+ spindles?
They either have swapped to a k member that has the corrected geometry or they have the bump steer issue and are in denial. I dont know about you, but I have owned several cars with bump steer issues and it will definitely keep you awake when driving.
I especially wouldnt want to deal with it with a drag car that unloads and reloads the front suspension rather agressively.
 

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:shakehead In the first case, they're not trying to "push their K-member", they're advising you which spindle to use if you're using a stock K-member and not theirs. In the 2nd case, they're not trying to "push their torque arm setups", they specifically tell you which stock replacement uppers to run instead of full poly, in the event you're still running uppers.

Here's the roll bind study their then-engineer wrote which has been published several times.
Thanks For the info MFE, Ill be doing a cobra brake setup on my fox in the spring .
 

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Discussion Starter · #34 ·
ahh im tired of the problems. i was not aware of these things before i purchased the spindles shame on me. but one thing i ask even if i changed to the sn95 spindles i would prolly still have the strut issue am i right? and i dont know whos tube k is in my car since it was on the car when i purchased it.
 

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chris306 here is my front end setup and had NO problems what so ever.my car is a notch

stock 92 a-arms and stock 92 ball joints
stock 92 struts
bbk lowering springs about 1 1/2 inches
96 spindles and brakes

now i used like 3 or 4 grade8 washers from my local hardware store for the castle nut on the lower ball joint.look at my pics.i have done many cars like this.you could end up with bump streer but every car will be different.i drove mine alot on the streets adn i eyeballed my alignment.even with the 265-35-18's it didnt track that bad unless i caught a grove in the road.you will be fine
 

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Bumpsteer visualized

Bumpsteer is any change in wheel toe as the suspension moves up and down. Ideally you don't want any of it. As the suspension moves up and down from bumps, body roll, brake dive, whatever, you don't want the car steering itself. All cars have bumpsteer, period. Some have very little, some have a lot. The less bumpsteer a car has, the nicer it is going to be to drive. How much bumpsteer a car has is a function of the geometry of the steering and suspension system.

The exact location of all the pivot points in the steering system of a Mustang to minimize bumpsteer is a complicated problem to solve. Way beyond a 10 minute internet discussion. Here is a ROUGH approximation to the correct solution. When viewed from the front, the tie rods and FCAs should be parallel to one another. To tell when they are parallel to one another, you must be able to see inside the ball joint so you can see where its pivot point is. Unless you have taken your ball joints apart to find this location, there is no way you are going to know where it is. The bottom line is that if you want to adjust the spacers in a bumpsteer kit, you can't do it by eye. You must measure the bumpsteer curve on the car or copy a set of suspension parts, alignment and bumpsteer spacer stack from another Mustang with a known good bumpsteer curve.

Below is a link to a sketch with the correct geometry for minimum bumpsteer with a strut suspension. To achieve minimum bumpsteer, the line through the tie rod must meet the other two lines at the instant center. The steering rack can be raised or lowered to achieve this or the outer tie rod can be raised or lowered with a bumpsteer kit. Moving either of these pivot points, up or down will change the location of the line going through the tie rod and fix things or make them much worse.

See the Strut-bumpsteer-sketch.png attached at the bottom.

The bumpsteer curve refers to a graph which has suspension travel along one axis and wheel toe (in inches at the tire or degrees) on the other axis. Here is an example of one:

See the Bumpsteer_graph.JPG attached at the bottom.

I realize that it is difficult to visualize how moving around different points in the steering and suspension system could affect bumpsteer, so I made a simple suspension model in SolidWorks and animated the results. This makes it easy to see the bumpsteer behavior. The model is intentionally simple to make the bumpsteer behavior simple. The FCA pivot axis is parallel to the centerline of the car, so there is minimal caster change with suspension travel. The FCA is represented as two different links joined at the pivot point of the ball joint. The K-member is just a flat plate to mount the front control arm pivot and the steering rack to.

See the bumpsteer_model.jpg attached at the bottom.

Case #1:

The height of the outer tie rod has been adjusted to give minimum bumpsteer given the locations of the other points in the suspension/steering system. In this case, there is a total of 0.14 degrees of toe change over the entire 6.7" of suspension travel. This is barely visible in either video. Note that the tie rod and the FCA are NOT parallel. If I make them parallel, the bumpsteer gets about twice as bad.

Front view:


Side view:


Case #2:

The height of the outer tie rod has been raised 0.7". Notice that the tie rod and FCA are no longer even close to parallel. The length of the tie rod has been adjusted so that toe is still zero at ride height. In this case, the toe changes from 2.8 degrees in at full bump to 2.2 degrees out at full droop. This is total change of 5 degrees from case #1. 35 times as much toe change!

Front view:


Side view:


As explained on the MM website in the tech section, the 94-95 spindles have almost exactly the same steering arm height as the 87-93 11" brake spindles. If you put these spindles on your Fox Mustang with a stock k-member, your bumpsteer curve is going to be ok. About the same as Ford made it with the original Fox spindles. If you install the 96+ spindles, the straight steering arm of this spindle is going to lower your outer tie rod 1". No problem, just go buy a bumpsteer kit. But wait, you need to RAISE the outer tie rod 1", so unless your bumpsteer kit came with magic bumpsteer spacers that have a negative length and allow the end of the tie rod to occupy the same location as the end of the steering arm, you are out of luck.

94-95 versus 96-98 spindle photo:

Visual identification of Mustang front spindles

I know that there are a lot of Fox Mustangs out there with stock k-members and 96+ spindles. However that isn't evidence that its a good idea or will make your car handle well. At least once a week I see someone driving on the freeway with 15-20 psi in one of their tires. You point to the tire as you drive by and they are clueless. You point this out to someone stopped at a gas station and they say "I never noticed the tire was low". Should we use this as evidence that tires run at half of their proper inflation pressure make a car handle well? Of course not.

Why does the M-2300-k kit come with 94 spindles? Because a Fox Mustang would handle very badly with a stock k-member and 96+ spindles and Ford knows this.

If MM wanted to sell Mustang parts without any regard for their performance. We could crank out 500 pairs of poly-poly rear upper control arms a day. We would make a lot more money since our sales volume would be up and more significantly we wouldn't have to actually do any design and testing work. As MFE already said, we aren't trying to push our k-member, we are just trying to let people know which parts will actually work correctly with which other parts.
 

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Discussion Starter · #37 · (Edited)
i understand thanks for the vids. the qa1 struts have some hex thing on the end and it sticks about an inch or so past the strut body. i would still have a problem with the sn spindles with the strut touching the control arm. when looking at it, it barely hits but i dont want to be not able to steer my car since the suspension in the front will more than likly be almost fully extended all the way down the track. anyone have any experiance with the qa1s?
 

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The exact location of all the pivot points in the steering system of a Mustang to minimize bumpsteer is a complicated problem to solve. Way beyond a 10 minute internet discussion. Here is a ROUGH approximation to the correct solution. When viewed from the front, the tie rods and FCAs should be parallel to one another. To tell when they are parallel to one another, you must be able to see inside the ball joint so you can see where its pivot point is. Unless you have taken your ball joints apart to find this location, there is no way you are going to know where it is. The bottom line is that if you want to adjust the spacers in a bumpsteer kit, you can't do it by eye. You must measure the bumpsteer curve on the car or copy a set of suspension parts, alignment and bumpsteer spacer stack from another Mustang with a known good bumpsteer curve.
And that will only get you in the ballpark.

Bumpsteer is a strange beast and is affected to a great degree by not only the designed geometry of the system, but also by the tolerances and how they stack up. I've seen two cars with identical setups with vastly different spacer stacks on their bumpsteer kits. Shoot -- I've seen the same car with vastly different stacks on each side (mine differs by almost 0.25", left to right.)


I know that there are a lot of Fox Mustangs out there with stock k-members and 96+ spindles. However that isn't evidence that its a good idea or will make your car handle well. At least once a week I see someone driving on the freeway with 15-20 psi in one of their tires. You point to the tire as you drive by and they are clueless. You point this out to someone stopped at a gas station and they say "I never noticed the tire was low". Should we use this as evidence that tires run at half of their proper inflation pressure make a car handle well? Of course not.
This is an excellent point. As I said in an earlier post, eliminating bumpsteer becomes a lot more important once you actually start to make the front of the car handle reasonably well. If you're still running a stock-ish suspension with street tires, having a little bumpsteer in the car is less noticable than if you've replaced all the bushings with rod ends and are running wide, sticky racing slicks.

It's a bit like singing off-key. It's not as noticable in a punk band as it is in a barbershop quartet. :)
 

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I'm bumping this one back to the top, because I don't think it's been resolved.

It seems everyone on the internet is just passing around the same information like a broken record, always referring to the MM website and their warnings, about using 96-04 spindles with the straight steering arm with stock fox k-member.

I'm calling BS on this one. There are 2 problems with this gospel...

1. In all the MM info, it always refers to the stock fox k-member as one size across the board. This is incorrect. The 79-86 stock fox k-member control arm mounting points are 1" narrower than the 87-93. In all that info and preaching, nowhere does it take that into consideration when talking about track differences, wheel fitment issues, alignment, etc... between the 94-95 spindles and 96-04 spindles. You will have completely different results between the 79-86 fox and the 87-93 fox with these upgrades, yet they refer to the stock fox k-member as one size fits all. Impossible.

2. It never talks about or specifies stock height or lowered cars. How can they make such strong statements and never talk about the suspension height geometry and how it affects the angle of the tie rod. The reason the 96+ have the straight steering arm (1" lower) and apposed to the 94-95 curved upward steering arm is because the steering rack was lowered in the 96+ cars. If you lower the suspension on the fox, the tie-rod angle is going to be different than a stock fox suspension height.

Something isn't adding up...
 

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I'm bumping this one back to the top, because I don't think it's been resolved.
Yes, mostly because you don't appear to understand the fundamental relationships involved. Follow along:

1. In all the MM info, it always refers to the stock fox k-member as one size across the board. This is incorrect. The 79-86 stock fox k-member control arm mounting points are 1" narrower than the 87-93. In all that info and preaching, nowhere does it take that into consideration when talking about track differences, wheel fitment issues, alignment, etc... between the 94-95 spindles and 96-04 spindles. You will have completely different results between the 79-86 fox and the 87-93 fox with these upgrades, yet they refer to the stock fox k-member as one size fits all. Impossible.
MM's staff has been more than forthcoming about the fact that the K-members changed multiple times throughout the foxbody run, specifically the horizontal distance between the A-arm pivot points. But none of those changes has the effect on the relationship in height between the pivot points of the A-arms and the tie rod ends as changing the height of the tie rod end or the rack do, and it's that relationship that determines bumpsteer behavior. So for all intents and purposes, as far as bumpsteer behavior relative to spindle changes goes, the K-members ARE the same. OK? Next...
2. It never talks about or specifies stock height or lowered cars. How can they make such strong statements and never talk about the suspension height geometry and how it affects the angle of the tie rod.
Because simply lowering the car doesn't change the bumpsteer behavior, as defined by X amount of toe change for Y amount of suspension travel. It only moves the starting point of that behavior to a different point in the compression curve, and MM is already on record with the fact that the factory bumpsteer curve isn't all that bad in the first place, meaning whether you start at stock ride height or lowered 1.5 inches, the factrory curve is still pretty good. IThat is, until you change the height of the outer tie rod pivot point relative to the ball joint pivot point, the A-arm pivot point, or the inner tie rod pivot point (rack height)...lowering the car does none of those things. But I'll gladly rent you my laser bumpsteer gauge if you want to check their work.

The reason the 96+ have the straight steering arm (1" lower) and apposed to the 94-95 curved upward steering arm is because the steering rack was lowered in the 96+ cars.
Exactly...in so doing, they kept the relationship between the outer tie rod pivot point and the inner tie rod point pretty much unchanged.

If you lower the suspension on the fox, the tie-rod angle is going to be different than a stock fox suspension height.
...but the relationship between the pivot points is UNchanged. Get it?
 
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