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post #1 of 12 Old 08-18-2009, 10:13 AM Thread Starter
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Steering Issue

I took my car to the track again for the first time since my new engine/suspension/steering install on Saturday and I have one problem.

Seems the steering is way more sensitive than it was before. The slightest input on the steering wheel yields a large result at the tires, so much in fact, that the car is very difficult to drive at the limit and required constant small corrections, something I didn't have to do before these parts were installed.

The stuff I installed was an MM k-member, standard offset Fox a-arms w/delrin bushings, MM/Bilstein sport coilovers with 400# springs, cc plates, steering shaft, aluminum rack bushings, bolt through bumpsteer kit, shortened sway bar end links, sway bar bracket re-enforcements, XD rear LCAs, 250# rear coilovers, and a PHB. Also installed was an AGR 15:1, firm valved rack.

I took care to center the k-member and rack and I did have to re-install the shaft as it was on wrong the first time but fixed before the track excursion. The alignment settings were max caster (just under 6 degrees is all that could be obtained), 2.5 degrees of negative camber, and 1/16" of toe in. I didn't get to set bumpsteer but the condition is obvious under all surface and throttle/braking (or lack therof) conditions so I've put that aside as a possibility for now. Also, it doesn't pull or drift on the highway.

My feelings are that the rack has a valving issue but before I start going down that road, I figured I'd ask everyone here if they've run into any similar issues or if anyone can think of other causes for this. Sorry for the long post.


Last edited by MJ91GT; 08-18-2009 at 10:19 AM.
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post #2 of 12 Old 08-18-2009, 10:23 AM
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Your steering is more sensitive because the suspension is no longer as sloppy as overcooked pasta. Learn to drive the car.

FWIW -- I had the same thing happen when I installed my front end, and had to re-lern the car. It took me a little while to re-learn how much steering input the car needed at turn-in.


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post #3 of 12 Old 08-18-2009, 12:09 PM Thread Starter
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Quote:
Originally Posted by gt40mkII View Post
Your steering is more sensitive because the suspension is no longer as sloppy as overcooked pasta. Learn to drive the car.

FWIW -- I had the same thing happen when I installed my front end, and had to re-lern the car. It took me a little while to re-learn how much steering input the car needed at turn-in.
Believe me, I noticed and appreciated the lack of slop in the steering system of the car. I actually wrote a bunch on the difference between that slop and this oversensitivity but decided to delete it as it was TMI and made my earlier post way too long.

I hope your right in that it just takes some adjustment in driving, but I have driven several other cars with much better, more precise steering than the Fox Mustang both on and off track and none of them were as reactive to input as this car.

Maybe I expected the firmer boost curve in the rack to actually be more firm, but it doesn't feel like it, even low speed turning requires no more effort than before and it feels like less. I was considering going with a different pulley on the P/S pump even before this and it may have sealed the deal. I'm just still not convinced there isn't some other issue that's causing the dartiness that I'm feeling with this car.
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post #4 of 12 Old 08-18-2009, 12:17 PM
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I noticed quicker steering just by the addition of poly CA bushings.It was enough of a diff that I was turning the wheel too much into corners and had to back off a little.

2003 Azure mach1 5 speed with IUP
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post #5 of 12 Old 08-18-2009, 03:05 PM
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Still no Torque Arm? But those look like TA spring rates. How much will that affect the situation? Tie rods in good condition? I wouldn't rule out the bump steer either. My car needs to have the bump steer set and gives me trouble on some corners. It drives fine on the road. My alignment is -1* camber, 7* Caster, 1/16" toe in.

You may laugh, but what do you have for a DD? I bought a new (to me) DD 18months ago. Each HPDE since this has been PITA. The Mustang doesn't feel "as it used to" even though nothing has been changed! (bought a BMW)

93 GT
full MM w/ forward offset arms
stock sway bars
275/40 street tires
350# front, 225# rear springs, Bilstein HDs
Never been scaled

1993 GT 310rwhp / 351rwtq
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post #6 of 12 Old 08-18-2009, 07:08 PM Thread Starter
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Those springs are what MM recommended for no torque arm, they recommend I bump up to 300#ers in the rear when I go with the TA. Tie rods are brand new bolt through MM pieces and are tight, inners are brand new with the rack, also tight, neither bind. Neither do the balljoints from what I can tell.

My daily driver right now is a Ford Flex, I change company cars every 6 months to a year and have driven lots of stuff as a DD, last one was an '08 Mustang GT. My father also owns and tracks a pretty well modified C5 Z06 which replaced a '98 TA and used to own an '04 CTS-V that we've had out on the track in the past. I've driven all three on track back to back with my car and it has nothing to do with coming out of a better or worse car. I also evaluate cars for a living, so I'm used to jumping in and out of different vehicles and honing in on their characteristics.

I'm not ruling out bumpsteer as I was before though, the more I think about it, the more I'm thinking the abrupt change in direction may cause some suspension movement despite the lack of front to rear change or bumps. I already had plans to borrow a bumpsteer gauge from a colleague when I next see him, I'll bumpsteer the car and re-evaluate.

Any other ideas are still welcome. Thanks for the replies guys.
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post #7 of 12 Old 08-19-2009, 02:08 AM
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What year are the spindles?
What set of FCA mounting holes are you using in the k-member?
Is the steering rack, raised lowered or centered in the steering rack bushings?
What is your bumpsteer stack height? Take a pair of calipers and measure from the bottom surface of the steering arm to the very top of the rod end ball. In other words, the total height of all the spacers captured between the rod end and the steering arm.

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post #8 of 12 Old 08-19-2009, 09:36 AM Thread Starter
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96+ spindles
upper mounting holes, a-arms are level at ride height
rack is in the lowest position, due to the 7qt oil pan
I believe I started with the spacer sleeve and a 1/4" spacer per the instructions but I'll have to climb under the car this evening and check/measure.
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post #9 of 12 Old 08-19-2009, 12:23 PM
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The racks tend to be overboosted on these (not sure about the AGR), and as mentioned, no slop = hyper responsive, but to me it sounds like you really need to actually measure your bumpsteer and adjust accordingly.

That said, I have a similar front end setup, and mine is set for just a #### hair's toe-out under bump, and it's still a little twitchy on the street. Not really on the track, though.
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post #10 of 12 Old 08-20-2009, 01:22 AM
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I would change your bump steer stack height to 2.3". This will be the large spacer (1.44") plus the 0.48" plus the 0.24" plus the 0.12". Put the rest of the small spacers below the tie rod.

There is a new set of instructions posted for that bump steer kit. It has only been up a couple of days.

http://www.maximummotorsports.com/co...TR-1-3-6r3.pdf

Using a steering rack with a stiffer torsion valve, but with a stock power steering pump can make the steering nonlinear. When the steering is near center, the feel will be good, heavy and maybe a slight bit rubbery. Once you turn the steering wheel a tiny bit, twisting the torsion valve, which opens up the fluid passage activating the power steering, you get too much assist from the stock pump that has too much fluid flow. This makes it hard to make very fine corrections, especially when going straight.


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post #11 of 12 Old 08-20-2009, 09:34 AM
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Jack,

The new instructions are great! I have been looking into actually bumpsteering the car for a while and taking in all the data I could and these new instructions really make it a lot easier. Thanks again.

Chris

92 Limited Edition Vert HodgePodge MM , Cobra Brakes, Roll Bar, Auborn Pro, 31 spline Mosers, 3.73's
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post #12 of 12 Old 08-20-2009, 10:50 AM Thread Starter
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Quote:
Originally Posted by Jack Hidley View Post
I would change your bump steer stack height to 2.3". This will be the large spacer (1.44") plus the 0.48" plus the 0.24" plus the 0.12". Put the rest of the small spacers below the tie rod.

There is a new set of instructions posted for that bump steer kit. It has only been up a couple of days.

http://www.maximummotorsports.com/co...TR-1-3-6r3.pdf

Using a steering rack with a stiffer torsion valve, but with a stock power steering pump can make the steering nonlinear. When the steering is near center, the feel will be good, heavy and maybe a slight bit rubbery. Once you turn the steering wheel a tiny bit, twisting the torsion valve, which opens up the fluid passage activating the power steering, you get too much assist from the stock pump that has too much fluid flow. This makes it hard to make very fine corrections, especially when going straight.
Exactly the situation I have, I will definately change the bumpsteer spacer stackup and will bumpsteer the car too when I get ahold of the gauge. I'll also get ahold of AGR and see what pump they recommend to go with that gear.

Thank you
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