Rolling rear - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 10 Old 01-26-2006, 07:07 PM Thread Starter
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Rolling rear

I'm trying to figure out my upgrade plan for this year. What I want to do is get the rear body roll under control on the track. The front is working well for me, but the rear feels like a boat when transitioning. I'm trying to find the best cure.
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My current setup:
2000 GT HT.
Front - 325lb/in  x 10in Coilovers  (MM)  (lowered about 1.25" from stock - same as my Steeda Sport ride height)
           03 Cobra Bilsteins
           CC-plates
Rear - H&R Race (260-280 -1") springs
         Mach 1 Tokico shocks
         MM PHB
Note that I don't have aftermarket LCA's, but I don't think they'll help. I think replacing the shocks will be a good first step. What else can I do? Raise the front more? TA?

Thanks
Jon


e90 328i

Last edited by jfranci3; 01-26-2006 at 07:13 PM.
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post #2 of 10 Old 01-26-2006, 07:39 PM
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Since the body is essentially a hard unit, roll at the rear is the same as roll at the front. It may appear different due to differences in roll center height, but the roll is the same nonetheless. You can play with RCH's with suspension and spring rate changes, but the fact that you say the rear end "feels like a boat in transitions" tells me what you're really trying to eliminate is rear sway. Unless what you mean is it feels like a boat in the sense that it's rolling across its keel LOL. Which is fine, except IMHO that's almost more a function of your front end than rear. I look forward seeing to what others have to say about it.

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post #3 of 10 Old 01-26-2006, 10:45 PM
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What I noticed immediately after the MM T/A went in was the feel of the car changed completely. The rear end just sort of followed along instead of acting like it was fighting the front end. Kind of hard to describe, but this was noticeable even at quite moderate speeds on curved roads.

Interestingly, the rear of the car actually rolls more with the T/A than with the 4-link. I had to space my (10 1/2") rear wheels out a 1/4" to avoid contact with the inner wheel well in roll. This is due to the MM PHB which now controls the rear roll center and lowers it quite a bit and possibly also to less bind.

I also found the T/A added a fair bit of understeer at auto-cross speeds. An MM adjustable rear stabar took care of that.

Nevertheless, the improvement is immense in both feel and grip. I can't imagine owning another stick axle Mustang and leaving the 4-link in it. Easily the best change I have made to the car.

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post #4 of 10 Old 01-27-2006, 08:28 AM
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Give consideration to a 3-link?
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post #5 of 10 Old 01-27-2006, 03:16 PM Thread Starter
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Quote:
Originally Posted by MFE
Since the body is essentially a hard unit, roll at the rear is the same as roll at the front. It may appear different due to differences in roll center height, but the roll is the same nonetheless. You can play with RCH's with suspension and spring rate changes, but the fact that you say the rear end "feels like a boat in transitions" tells me what you're really trying to eliminate is rear sway. Unless what you mean is it feels like a boat in the sense that it's rolling across its keel LOL. Which is fine, except IMHO that's almost more a function of your front end than rear. I look forward seeing to what others have to say about it.
I see your point, but I don't think it's the front based on feeling. The rear feels like it's transitioning over a very large arch, while the front feels like it's traveling over a small arch.

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post #6 of 10 Old 01-27-2006, 04:45 PM
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You need that big rear wing that came on the 00 cobra R.

The only part in your recipe that raises and eyebrow is somthing you already noticed. The Mach 1 rear shocks being mated with the H&R race spring. Instead of trying to figure out what next major item to purchase. I would do the Bilstien HD shock upgrade in the rear. The shock valving compared to the spring compression clearly shows the spring is dominating the force applied. The valving of the shock can't control the spring thus allowing the spring to basically throw the cars weight from side to side. So when you transition over an arch the front of the car pulls the body down on one side compressing the spring and as soon as the rear transitions. The spring recoils throwing the weight to the otherside and vice versa. Since the shock valving can't control the motion its playing catchup, instead controlling the spring. I know its not a scientific or engineering explanation, I am trying to explain in general.

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post #7 of 10 Old 01-27-2006, 09:07 PM
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The MM PHB has a roll center of what ? 7" ? With a roll center that low you

definately will need stiffer rear springs and/or a stiffer sway bar...

I would suggest getting an adjustable MM rear bar and play around with that.
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post #8 of 10 Old 02-21-2006, 05:03 PM Thread Starter
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OK, now I have a problem. I bought a set of Bilstien HD (non-adjs) for $180 from Autozone online. I found a new set of Koni rear single adjustables for $175, these are normally $285. It was an easy decision when they were different prices, but now things have changed. Since I'm such an unbelievable freaking genius, I went ahead and bought the Konis. I have no idea why.

Which should I keep?
One thing to consider- I can't adjust the Konis by turning a knob, I have to completely remove the shock in order to adjust it.

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post #9 of 10 Old 02-21-2006, 08:44 PM
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Once I had MM Bilstein coilovers installed on the rear, it stopped leaning in hard corners. MM recommended 250lb for the rear. I also have 325lb in the front (mm bilstein coilovers)

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post #10 of 10 Old 02-21-2006, 10:08 PM
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Quote:
Originally Posted by jfranci3
OK, now I have a problem. I bought a set of Bilstien HD (non-adjs) for $180 from Autozone online. I found a new set of Koni rear single adjustables for $175, these are normally $285. It was an easy decision when they were different prices, but now things have changed. Since I'm such an unbelievable freaking genius, I went ahead and bought the Konis. I have no idea why.

Which should I keep?
One thing to consider- I can't adjust the Konis by turning a knob, I have to completely remove the shock in order to adjust it.
The Koni SA's I used to have in the back adjusted just like the fronts, with the little white knob thingie. You do have to remove or cut the trunk panels to reach it though. Removing the shock to adjust is a big PITA in my book.

I now have the MM race-valved Bil's in th rear. Can't say I miss the adjustability. I still have the Koni's up front and do adjust them from time to time, especially for slalom intensive vs. sweeper intensive courses.

IMO - if you're more driver than tuner, stick with the Bil's. Vice-versa, sell both sets and get the later version Koni adjustables you cn adjust easier.

Edit because it's bad enough I shorten Bilsteins to Bil's, at least I can capitalize it.


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