Koni Yellows, rear end jumpy on bumps - Ford Mustang Forum
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post #1 of 21 (permalink) Old 08-01-2013 Thread Starter
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Koni Yellows, rear end jumpy on bumps

Hi guys,

I have installed Koni Yellows all around on my 2012 V6, along with Steeda Sport springs in the front. Since the Steedas only lowered the front end by ½ inch, the 1 inch drop in the back was too much, so i reinstalled the rear stock springs.

Car drives great on most surfaces and is a blast around the track, but the rear end gets jumpy over sharp bumps. The stock Pony Package suspension used to float and the rear end would dance on bumps.

I can adjust the front Konis from full soft to 1 full turn up front and they are firm, in control and never uncomfortable. But i am already at full soft in the back and i wish i could go softer. A sharp bump on the road makes the rear jump a bit, but the Konis take the hit and settle, keeping the car in control. It is just a bit annoying and distracting

Only mod in the back is a BMR adj phb.

Anybody fixed that behavior of the live axle? What would better LCAs with better bushings do for this?


Canadian 2012 V6, MT, Perf.White Pony Package (3.31 gears). Koni Sport Shocks & Struts. Steeda Sport Springs w/HD Mounts, Route 66 SpeedShop 55D rear spring kit. Boss 302 Strut Tower Brace. BMR Adj PHB. BFG G-Force Sport Comp2. Pioneer TS-D6802R Front SPeakers, Clarion 80W/Ch Amp. JL Audio 8 Inch Sub And 175W Amp. GT500 Steering Wheel. 2012+ Tilting Headrests
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post #2 of 21 (permalink) Old 08-01-2013
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Time to go shopping...

I have Koni Yellows and Steeda Sport springs. Lowering changed the geometry of the control arms and driveshaft pinion angle. Here's what you will need to get that planted feeling back:

* Lower control arms & Relocation Brackets (if BMR, use middle hole)
* Upper control arm & Relocation Bracket

Choose your brand. I chose BMR and am happy.


2012 GT Yellow Blaze MT 3.73 * Steeda CAI & 91 Tune * Koni Yellows * Steeda Sports * BMR Adj. Panhard Bar, UCA, LCA's & Brackets * Barton Shifter & Bracket * Ford Brake Duct Cooling Kit * Steeda Brakes * Hypersilver Eurotek O2 19x9.5's * 275/40ZR19 Michelin PSS's * Ford Racing Touring Mufflers * GT/CS Front Valance * Boss Splitter * Blackout Fogs, Deck Lid & MMD Tail Light Trim * GT500 Rear Diffuser & Splash Guards * Infinity Ref. Fr. Speakers * Custom Faux Gas Cap * Redline Hood Struts *.
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post #3 of 21 (permalink) Old 08-01-2013 Thread Starter
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the rear is NOT lowered, i am on stock spings in the back, so ride height is stock. Those springs are the same as on the perf pack and the GT.

Again, only mod in the back, aside from the Konis, is the BMR adj Panhard Bar that i installed when i lowered the back. I returned to stock springs because the rear was too low and i felt the car was not balanced properly

Canadian 2012 V6, MT, Perf.White Pony Package (3.31 gears). Koni Sport Shocks & Struts. Steeda Sport Springs w/HD Mounts, Route 66 SpeedShop 55D rear spring kit. Boss 302 Strut Tower Brace. BMR Adj PHB. BFG G-Force Sport Comp2. Pioneer TS-D6802R Front SPeakers, Clarion 80W/Ch Amp. JL Audio 8 Inch Sub And 175W Amp. GT500 Steering Wheel. 2012+ Tilting Headrests
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post #4 of 21 (permalink) Old 08-01-2013
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You should probably get a least some better lower control arms but the biggest issue is this:

The factory springs were meant to work as a system and together just like the Steeda Sports. Despite the factory hardware not being exactly brilliant, they do complement each other just like the Steeda springs do. The spring rates are all out of wack. Plus your rake has increased as well, throwing off the dynamics of the car. Because of this, your car is now very front domant in geometric balance. Choose one: factory springs all around or the Steeda springs all around.
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post #5 of 21 (permalink) Old 08-01-2013 Thread Starter
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Quote:
Originally Posted by nsadams87xx View Post
You should probably get a least some better lower control arms but the biggest issue is this:

The factory springs were meant to work as a system and together just like the Steeda Sports. Despite the factory hardware not being exactly brilliant, they do complement each other just like the Steeda springs do. The spring rates are all out of wack. Plus your rake has increased as well, throwing off the dynamics of the car. Because of this, your car is now very front domant in geometric balance. Choose one: factory springs all around or the Steeda springs all around.
Yeah! I hear you. The Sport springs dropped the front end only about a ½ inch, while the rear dropped by a full inch. Car was levelled, no rake, and that did not look good at all and did not handle well either, creating understeer. To get the original rake, the Sport springs would need to be a ½ inch taller. So to use the Steeda springs in the back, i would need ½ inch spring spacers and i don't know if that would be a good idea or where to look for quality parts. I have also been looking at the Route 66 Speedshop MUSTANG 55D SPRING KIT as those would lower about ½ inch with a spring rate closer to the Steedas than the OE spring.

Steeda now warns buyers about the light V6 in the 2011+ and do not recommend the use of Sport Springs.... but that was not the case when i purchased my springs.

The front end is great, so i would prefer fixing the back instead of going back to stock springs in front. Swapping rear springs is also a quick and painless operation.

Keep the comments coming, my Mustang handles great, but i need to tweak the rear end.

Canadian 2012 V6, MT, Perf.White Pony Package (3.31 gears). Koni Sport Shocks & Struts. Steeda Sport Springs w/HD Mounts, Route 66 SpeedShop 55D rear spring kit. Boss 302 Strut Tower Brace. BMR Adj PHB. BFG G-Force Sport Comp2. Pioneer TS-D6802R Front SPeakers, Clarion 80W/Ch Amp. JL Audio 8 Inch Sub And 175W Amp. GT500 Steering Wheel. 2012+ Tilting Headrests
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post #6 of 21 (permalink) Old 08-01-2013
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Sounds like your dampers are mismatched to your springs and the rear is mismatched to the front. Have you tried going harder on the dampers in the rear?
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post #7 of 21 (permalink) Old 08-01-2013 Thread Starter
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Quote:
Originally Posted by uh-oh View Post
Sounds like your dampers are mismatched to your springs and the rear is mismatched to the front. Have you tried going harder on the dampers in the rear?
Oh yeah! i have played with the rebound setting in the back and ½ a turn is too firm for the "beautiful" street of Montréal, but it rides quite nicely with only a ¼ turn. On the track, ½ a turn back and a full turn front and i am laughing in my helmet ;-) ... that is a smooth track. Streets of Montréal are something else

Canadian 2012 V6, MT, Perf.White Pony Package (3.31 gears). Koni Sport Shocks & Struts. Steeda Sport Springs w/HD Mounts, Route 66 SpeedShop 55D rear spring kit. Boss 302 Strut Tower Brace. BMR Adj PHB. BFG G-Force Sport Comp2. Pioneer TS-D6802R Front SPeakers, Clarion 80W/Ch Amp. JL Audio 8 Inch Sub And 175W Amp. GT500 Steering Wheel. 2012+ Tilting Headrests
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post #8 of 21 (permalink) Old 08-01-2013
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That rear end hop and skip on a sharp bump has been in this chassis since 05. LCA go a long way to helping but due to the three link rear geometry the actual angle of the rear axle will change as it moves through its arc. When you hit a sharp bump and the rear regains footing the axle has a different angle. The only true solution to this is a watts link as the rear is now allways true and parallel and there is no more change in the rear. Kind of hard to explain but what you are getting is momentary rear steer. Cheap fix is the LCA and if you are still on the stock sway bars its time for an upgrade. SAM STRANO adjustable or EIbach adjustable setup gives you a ton of tuning capabilities. Over steer or understeer is just a setting away.
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post #9 of 21 (permalink) Old 08-01-2013 Thread Starter
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i have been looking over and over at the Whiteline Watt's Link.... but that is too much money for now.

Would be nice to reinstall rear Steeda Sports, by i need something to to add about a ½ inch in height. I have seen adjustable spring seats, but those would probably add 1 inch. Something similar with a fixed height of about a ½ inch would do the trick, but i google and google and cannot find.

Canadian 2012 V6, MT, Perf.White Pony Package (3.31 gears). Koni Sport Shocks & Struts. Steeda Sport Springs w/HD Mounts, Route 66 SpeedShop 55D rear spring kit. Boss 302 Strut Tower Brace. BMR Adj PHB. BFG G-Force Sport Comp2. Pioneer TS-D6802R Front SPeakers, Clarion 80W/Ch Amp. JL Audio 8 Inch Sub And 175W Amp. GT500 Steering Wheel. 2012+ Tilting Headrests
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I used the UL Steedas all the way around with my Koni yellows and I have no rake that is discernible. But I also do not have the hopping issue that you have with my Steeda adj. PH bar and JM LCAs.
Best pic I have for a level angle to show rake, or lack of.
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UPR control arms & panhard bar settled my rear end down a lot.

I'm running Koni Yellows on my car though, and it doesn't seem bouncy at all. It seems like there's something strange going on here.


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Ground-control sells coil.over kits for the S197 chassis and you can buy the rear only in almost any spring rate you want. Ground-control.com
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post #13 of 21 (permalink) Old 08-02-2013 Thread Starter
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Quote:
Originally Posted by Sharad View Post
UPR control arms & panhard bar settled my rear end down a lot.

I'm running Koni Yellows on my car though, and it doesn't seem bouncy at all. It seems like there's something strange going on here.
Not bouncy, it takes a sharp bump to upset the rear-end. Those same bumps would make the rear-end dance on stock shocks, so now it recovers a lot faster with the Konis, but it still kicks a bit. That is what i am trying to fix.

Canadian 2012 V6, MT, Perf.White Pony Package (3.31 gears). Koni Sport Shocks & Struts. Steeda Sport Springs w/HD Mounts, Route 66 SpeedShop 55D rear spring kit. Boss 302 Strut Tower Brace. BMR Adj PHB. BFG G-Force Sport Comp2. Pioneer TS-D6802R Front SPeakers, Clarion 80W/Ch Amp. JL Audio 8 Inch Sub And 175W Amp. GT500 Steering Wheel. 2012+ Tilting Headrests
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post #14 of 21 (permalink) Old 08-02-2013 Thread Starter
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Quote:
Originally Posted by LandToSea View Post
I used the UL Steedas all the way around with my Koni yellows and I have no rake that is discernible. But I also do not have the hopping issue that you have with my Steeda adj. PH bar and JM LCAs.
Best pic I have for a level angle to show rake, or lack of.
very cool picture :-)

Canadian 2012 V6, MT, Perf.White Pony Package (3.31 gears). Koni Sport Shocks & Struts. Steeda Sport Springs w/HD Mounts, Route 66 SpeedShop 55D rear spring kit. Boss 302 Strut Tower Brace. BMR Adj PHB. BFG G-Force Sport Comp2. Pioneer TS-D6802R Front SPeakers, Clarion 80W/Ch Amp. JL Audio 8 Inch Sub And 175W Amp. GT500 Steering Wheel. 2012+ Tilting Headrests
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Like stated above you need all 4 springs to match. I've read great reviews on the JM LCAs. They seem to keep the rear end planted very well.

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