Bump Steer question - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 7 Old 09-02-2015, 02:58 PM Thread Starter
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Bump Steer question

Just got done installing MM k-member and standard offset control arms on my car. I have the rack mounted in the highest position(per instructions) and control arms in the top holes(per Jack's recommendation) and have plotted 4 bump curves and would like some opinions.

I am using a tapered stud kit and am using a 4" range because I am in to the bump stop at about 2 1/8 and -2 3/4 to full droop. Ride height is 25 3/4" front, 26" rear. For reference, stack heights are: Black=1.617, Red=1.742, Blue=1.677, Green=1.647. Are one of the curves good enough or should I experiment with different rack locations? Any suggestions are welcome, thanks.

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Jarrod

'92 Coupe - Full MM suspension, koni SA, stock bottom end,stock cam,TW170,Systemax,V-2SQ,42s,Treadstone A2A 552h/541t out of fuel @ 5200 Kurgan tuned.
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post #2 of 7 Old 09-02-2015, 05:57 PM
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Of those plots, and assuming the neg toe is toe out, I'd take the blue one, because it's the most moderate of the curves, and stays toe out the whole time instead of going toe-in to toe-out as the suspension moves. You might try a slightly longer stack, like 1.33 to see if you can get a curve like the blue one that's shallower still.

I'm puzzled as to why the curve is a parabola instead of an S shape though.

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post #3 of 7 Old 09-02-2015, 09:05 PM Thread Starter
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Quote:
Originally Posted by MFE View Post
assuming the neg toe is toe out
That is correct. I laid it out to mirror MM's sheet. It seems that the red and black started to emulate the 'S' but all the others had that arc. I'm not sure whether it is better to have toe out or toe in at bump or if I should just concentrate solely on bump and not worry too much about droop. That being the case the black had the least change in bump. I'll try some more settings to see what I can come up with. This is all new to me so I value any input I receive.

Jarrod

'92 Coupe - Full MM suspension, koni SA, stock bottom end,stock cam,TW170,Systemax,V-2SQ,42s,Treadstone A2A 552h/541t out of fuel @ 5200 Kurgan tuned.
'80 Mercury Capri - 377, AFR 225s, ProRace Fogger 5.70 @ 127. SOLD
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post #4 of 7 Old 09-02-2015, 10:14 PM
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Toe out in bump is preferred, it makes the car less nervous. No toe change at all is preferred but toe out if any at all.
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post #5 of 7 Old 09-04-2015, 04:18 AM
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Jarrod,

There is no way that you should be using a tapered stud style bumpsteer kit, if you have an MM k-member. Give me a call. I'm fairly certain that you have the phone number.

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post #6 of 7 Old 09-22-2015, 10:57 AM
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Still, the numbers are small. Our car was almost .250" to .300" toe out per inch of bump when we started. Are you measuring from full droop to full compression, stopping every inch, or going up from ride height and down from ride height?
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post #7 of 7 Old 09-22-2015, 03:40 PM Thread Starter
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Quote:
Originally Posted by 375instroke View Post
Are you measuring from full droop to full compression, stopping every inch, or going up from ride height and down from ride height?
Initially I started at ride height going up and down but then just started at +2" bump and ran it down to -2" droop to verify. The numbers were very repeatable either way and I only used the 4" range so that not to unload the jack or lift the body.

Jarrod

'92 Coupe - Full MM suspension, koni SA, stock bottom end,stock cam,TW170,Systemax,V-2SQ,42s,Treadstone A2A 552h/541t out of fuel @ 5200 Kurgan tuned.
'80 Mercury Capri - 377, AFR 225s, ProRace Fogger 5.70 @ 127. SOLD
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