Small issue after MM install - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 15 Old 05-20-2011, 07:40 PM Thread Starter
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Small issue after MM install

I just got done doing a complete front and rear MM suspension setup including coil-overs.

Everything seems to run out great except for one small problem. If I am driving straight down the road/highway and I hit the gas moderately, the car will actually pull a little to the left. As soon as I let back off the gas, it will pull back in line.

This isnt a dramatic jerk to the left/right or anything like that. It is a very subtle move but noticable none-the-less.

Alignment is set at -1.5 Camber, 5.5 Caster and 0 Toe. I have not fully adjusted bumpsteer yet with the gage but it is close and I experience very little bumpsteer while driving.

What do you guys think? Is this normal?


91 Road Racing Fox. N/A 383W. Full MM setup front and rear with Bilstein coil-overs. 14x1.25 Wilwood 6 piston fronts with Wilwood 13x1 single piston rears.
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post #2 of 15 Old 05-20-2011, 07:58 PM
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Make sure your rear control arms are tight and intact

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post #3 of 15 Old 05-20-2011, 08:06 PM Thread Starter
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I went through everything with a torque wrench before I took it on the street.

I just walked outside to take a look at the lower control arm bolts and all looks well and tight still.

91 Road Racing Fox. N/A 383W. Full MM setup front and rear with Bilstein coil-overs. 14x1.25 Wilwood 6 piston fronts with Wilwood 13x1 single piston rears.
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post #4 of 15 Old 05-20-2011, 08:19 PM
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Did you bump-steer it?
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post #5 of 15 Old 05-20-2011, 08:30 PM Thread Starter
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I have not actually put it on the bumpsteer gage yet.

I did get a bumpsteer stack height number from Jack that with my setup should be really close. I got him to calculate it out for me with a different setup I had before this and it was very close to exact once I actually got it on the gage. I would presume this one will be fairly close as well because in the driving I have done today I noticed VERY little bumpsteer.

91 Road Racing Fox. N/A 383W. Full MM setup front and rear with Bilstein coil-overs. 14x1.25 Wilwood 6 piston fronts with Wilwood 13x1 single piston rears.
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post #6 of 15 Old 05-20-2011, 08:39 PM
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Well, what you're experiencing may actually BE bumpsteer
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post #7 of 15 Old 05-24-2011, 11:43 AM
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If it's minor, like you say, you might just be feeling the effects of torque on a much tighter suspension. Could also be your diff. I've noticed what you're describing on previous cars and I think it has always been there to a small degree - a tighter suspension just makes it a little more noticeable.

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post #8 of 15 Old 05-29-2011, 09:43 AM
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I know you did do it, but Im assuming you "Jigged" the chassis before you put in the frame connectors, etc. right? That includes "jigging" the centering of the rearend with the TA and PB, etc. And also through the operating range of the suspension too. Also check over the suspension mounting points really good for cracks, deformadies, etc. For us, when we check things over really good, we actually remove the rear control arms, etc. to check inside the boxes, etc.
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post #9 of 15 Old 05-29-2011, 10:12 AM Thread Starter
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I'm sure it was actually bumpsteer that I was feeling. Once I got it on the bumpsteer gage, I could see it was going toe out more than .260 in just the first inch of travel.

I have got the bumpsteer down to .020 in the first 2 inches of bump and about the same in droop. I have yet to drive the car again but have little doubt the problem is cured.

It did not mention it in the directions or anything but since you can rarely get the bumpsteer to measure 0 throughout its travel; is it better to have your stack height set to toe out/in under bump?
Or is something like .020 toe in/out per inch so negligible it doesn't even matter?

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post #10 of 15 Old 06-03-2011, 03:11 PM Thread Starter
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Well, I regretably have to say that the problem still persists. The bumpsteer is set and it is good so it can't be that.

Im wondering that since I can't set my car low enough in the rear to have the panhard bar completely level with the ground if that might have something to do with it? There just isnt enough adjustment there to get the bar level and still keep the ride height I desire....


91 Road Racing Fox. N/A 383W. Full MM setup front and rear with Bilstein coil-overs. 14x1.25 Wilwood 6 piston fronts with Wilwood 13x1 single piston rears.
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post #11 of 15 Old 06-03-2011, 03:57 PM
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i hit a curb years ago with my car and the force slid my k member back about 1/4" on the passanger side. car always pulled after letting off the gas after that. even when installing new tires and new alignment. Maybe the k member didnt get installed straight? just a thought.
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post #12 of 15 Old 06-04-2011, 12:10 AM
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Quote:
Originally Posted by LT1HAHA View Post
Well, I regretably have to say that the problem still persists. The bumpsteer is set and it is good so it can't be that.

Im wondering that since I can't set my car low enough in the rear to have the panhard bar completely level with the ground if that might have something to do with it? There just isnt enough adjustment there to get the bar level and still keep the ride height I desire....
I have a somewhat similar issue, my car doesn't necessarily pull to the left, but when I'm going straight and just need to adjust left a little (a left hand kink on the track as an example), it seems to dart to the left, this feeling isn't there when doing the same thing to the right. I installed an AGR rack along with my MM stuff and I'd been thinking it was the rack but recently I've been rethinking this. The garage floor at my old house was a bit uneven (some cracks) and when I installed the k-member, it lined up perfectly the first time. I measured a few times and it was dead on. I had the jack stands adjusted to have the car level and the cracks only caused a small drop but I'm starting to think I need to re-measure on my new garage floor that is perfectly even and couldn't possibly throw off the measurment.

I also have the same issue with the left side of the PHB being lower than the right but I would highly doubt that would have any effect in non-heavy turning events. I believe it just increases the panhard bar arc, which while not necessarily desirable, would only show issues in high speed, sharp turns where there's alot of suspension movement. You may want to remeasure the rear axle placement in the car (side to side- I've done this again and mine's still dead on in the new garage) and do the k-member measurement over at the same time to ensure they're both accurate.
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post #13 of 15 Old 06-04-2011, 07:41 AM
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Like I mentioned time and time again, make sure your car is straight, chassis, components, etc. When you "plate" your car up, we use a lazer to make sure the pads are level. Check your welds, we also tack weld the PHB mounts in after mounting them with the bolts, plates, etc. The car needs to be "jigged" up first, then load the suspension on the tires, then load up the frame connectors to the bottom of the chassis then weld up in sections, while reassuring the car is still "jigged" up correctly. You wouldnt believe how many frame connectors we changed out to MM frame connectors and when we cut the old ones out, some sections went "thang!!" It was binding up the chassis. We normally run a little bit toe in on the fronts (depending on the set up), I noticed you run "0" toe, did you try to adjust and see what happens? I dont think its entirely the front set-up though. Did you check the wheel base measurements? (side to side)
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post #14 of 15 Old 06-12-2011, 09:21 PM Thread Starter
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**UPDATE**
After trying a few things and talking to MM, we decided to try geting it aligned again. Finally got it to the alignment shop today and I am happy to report that the issue is SOLVED!

Turns out my original alignment was faulty. Perhaps the tech didn't install something correctly or the computer was giving false readings. Either way it is all good now and i am going to Mid-Ohio July 15 to really ring this thing out!!

Thanks and see you at the track!

91 Road Racing Fox. N/A 383W. Full MM setup front and rear with Bilstein coil-overs. 14x1.25 Wilwood 6 piston fronts with Wilwood 13x1 single piston rears.
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post #15 of 15 Old 06-18-2011, 11:50 AM
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Quote:
Originally Posted by MJ91GT View Post
The garage floor at my old house was a bit uneven (some cracks) and when I installed the k-member, it lined up perfectly the first time. I measured a few times and it was dead on. I had the jack stands adjusted to have the car level and the cracks only caused a small drop but I'm starting to think I need to re-measure on my new garage floor that is perfectly even and couldn't possibly throw off the measurment.
Somethiing to consider. My garage has no cracks and is an absolutely even 5" reinforced slab. However, it was designed with a slight slope from the center to the sides as well as from the front to the back. This is to allow water to drain away. I discovered this issue when I did my MM PHB install. I don't think the slope is enough to worry about, but it is a consideration if your garage is designed the same as mine.
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