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Considering a rear shock change: Koni Yellows to ???

Best dual purpose shock for a s197?

  • Bilstein B6

    Votes: 3 42.9%
  • Viking Double Adjustable

    Votes: 0 0.0%
  • Koni SRT

    Votes: 0 0.0%
  • Factory Boss 302

    Votes: 0 0.0%
  • Ford Performance

    Votes: 4 57.1%
  • Revalved Koni Yellows

    Votes: 0 0.0%
  • Other

    Votes: 0 0.0%

  • Total voters
    7
After finally getting the V6PP car put together halfway through the autox season, I've found myself contemplating a rear shock change away from the Koni Yellows currently on the car. I have literally modified every single car I've owned since the age of 17 with Koni Yellows starting with my 92 civic, 85 CRX Si, Dinan 540i 6spd, WRX, and 8th gen Si. On every car I loved the Konis and their adjustability, not to mention the perks of their replacement warranty.

Fast forward to the Mustang, and I've been disappointed with the rear Koni Yellow shocks in both street ride quality and in getting the rear to feel "planted" in autocross. We've got a real mix of parts (which goes against the mindset of some on here), but overall the setup has been very successful as an affordable dual purpose configuration. Our last few outings have seen the car very close to the top of the pack in CAM locally on just 285 Falkens. The setup works, but it could be better..

Current setup:
Stock boss 302 springs (186 lb/in rate), stock ride height
Koni Yellows
Ford Performance Jounce kit (Rear Bumpstops)
Stranoparts swaybar with rubber bushings set to softest setting (~162 in/lbs vs 193 in/lb for stock 24mm bar)
Whiteline rear control arms and adjustable Panhard bar (these have stiffer bushings, floating center tube to mitigate binding, non spherical)

The front Koni Yellows have been absolutely fine with 400lb springs and ride very well, even on NYC roads. The rear on the other hand rides "okay" most of the time, but is absolutely horrible on expansion joints. On the street I have the rear Konis set to just off full soft, whereas at autocross we rarely ever exceed 1 turn towards firm. This makes me think that the Konis are valved too stiff for spring rate we are running. Instead of sending out the Koni's for a revalve I'm considering changing things up and wanted to hear from the TMO collective

Options I've been considering;

1) Viking double adjustable shocks:

Pros: more adjustment (rebound/compression), American made, only ~$200 bucks each for double adjustable, have been used with some success in autocross (I know Eric Simmons ran Vikings on his CAM-T Camaro)

Cons: More variables for "tuning' the shocks can complicate things, still a twin tube design

2) Bilstein B6

Pros: CHEAPPPPPP, monotubes, should have a close to stock ride quality, Bilstein durability

Cons: Not adjustable, if we lower the car rear of the car next season with GC Coilovers sleeves they may be outside their effective range

Other options out their include stock Boss 302 shocks, Koni SRT non adjustables, or maybe even a Ford Performance shock

I feel like the mild rear spring rates/bushing combo coupled with stock ride height should not be producing such a poor ride quality. Curious what some of you are running for shocks out back?

Thanks in advance,
J
 
4,975
5,785
I think you'll find most folks on here tend to go with Ford Performance packages for their cars because the parts are designed to work together, and they have a very competitive racing pedigree in the SCCA/PWC and IMSA. Should you decide to jump the shark and go coil over, then the field opens up a bit, the JRI is probably more budget oriented to the hi zoot Penskes used for competition only, if you go that route you need to plan on spending around $4K for the less expensive brands and have them rebuilt every 20K street miles, the competition Penskes will need to be done about twice a year, depending on the tracks and the usage. I would, for the reason listed above, recommend the same shock package on all four corners because they will be more compatible with each other.
Whatever you decide, the 4 shocks need to be the same brand/style.

and even though the catalog says control arms, they are trailing arms, I'm on one of my suspension nomenclature jihads again.
 
Last edited:

Norm Peterson

Corner Barstool Sitter
939
711
Exp. Type
HPDE
Exp. Level
5-10 Years
a few miles east of Philly
Current setup:
Stock boss 302 springs (186 lb/in rate), stock ride height
Koni Yellows
Ford Performance Jounce kit (Rear Bumpstops)
Stranoparts swaybar with rubber bushings set to softest setting (~162 in/lbs vs 193 in/lb for stock 24mm bar)
Whiteline rear control arms and adjustable Panhard bar (these have stiffer bushings, floating center tube to mitigate binding, non spherical)

The front Koni Yellows have been absolutely fine with 400lb springs and ride very well, even on NYC roads. The rear on the other hand rides "okay" most of the time, but is absolutely horrible on expansion joints. On the street I have the rear Konis set to just off full soft, whereas at autocross we rarely ever exceed 1 turn towards firm. This makes me think that the Konis are valved too stiff for spring rate we are running.
J
Makes me wonder if the rear adjusting mechanisms are damaged. I noticed that the settings that even my wife was fully comfortable with (with 140-ish lb/in OE rear springs) became horribly harsh over expansion joints once the 220 lb/in rear springs went in. But that got a whole lot better after dialing them back. Only took once driving it to tell me I was on the right track, after which it became a matter of fine-tuning.

Another data point, if nothing else.


Norm
 

Dave_W

Cones - not just for ice cream
618
730
Exp. Type
Autocross
Exp. Level
20+ Years
Connecticut
"Crashing" over expansion joints seems more compression-side, rather than rebound-side (Koni yellows typically only adjust rebound). Either way too much compression, or not enough and hitting the bumpstops. Try putting a zip tie on each shock shaft at the shock body, hit some expansion joints, then check how far the zip tie moved up the shaft. Compare to distance between axle and bumpstop. If you're running out of compression travel, try a stiffer spring.

Also, make sure the rear sway bar isn't binding. If you diconnect the ends, you should be able to rotate a sway bar with one or two fingers (except the stock bars with cast-in bushings). Urethane bushings and/or aftermarket mounts are notorious for binding up sway bars.

The Vikings are almost cheap enough to try on a whim. Bilstein can custom-valve their shocks at the Poway, CA service center, but there are some restrictions on the models - you can call them to check on the Mustang B6. Used to be the hot ticket for Stock NA/NB Miatas back in the day.
 
Makes me wonder if the rear adjusting mechanisms are damaged. I noticed that the settings that even my wife was fully comfortable with (with 140-ish lb/in OE rear springs) became horribly harsh over expansion joints once the 220 lb/in rear springs went in. But that got a whole lot better after dialing them back. Only took once driving it to tell me I was on the right track, after which it became a matter of fine-tuning.

Another data point, if nothing else.


Norm
Hey Norm,

Appreciate the perspective about your own experience with the Koni Yellows. Out of curiosity, with your 220lb/in rear springs, what shock settings are you running on the streets of NJ?
 
"Crashing" over expansion joints seems more compression-side, rather than rebound-side (Koni yellows typically only adjust rebound). Either way too much compression, or not enough and hitting the bumpstops. Try putting a zip tie on each shock shaft at the shock body, hit some expansion joints, then check how far the zip tie moved up the shaft. Compare to distance between axle and bumpstop. If you're running out of compression travel, try a stiffer spring.

Also, make sure the rear sway bar isn't binding. If you diconnect the ends, you should be able to rotate a sway bar with one or two fingers (except the stock bars with cast-in bushings). Urethane bushings and/or aftermarket mounts are notorious for binding up sway bars.

The Vikings are almost cheap enough to try on a whim. Bilstein can custom-valve their shocks at the Poway, CA service center, but there are some restrictions on the models - you can call them to check on the Mustang B6. Used to be the hot ticket for Stock NA/NB Miatas back in the day.

I had similar inklings about this being a compression issue with the Konis due to the lack of tangible improvement after trying various rebound adjuster settings in expansion joint scenarios.

I certainly hope that it is not an issue with the suspension bottoming out. Stock height with Boss 302 springs, shorter Ford Racing bumpstops, and the rest of the stock suspension geometry is intact. I'll play around with the zip tie test you mentioned one of these days

Will definitely test for swaybar bind prior to next weekends NNJR event when I've got the rear apart for new rotors/pads, definitely something I may have overlooked.

Spoke to some reps at Viking and worked out a deal to R&D their new Berserker series rear double adjustable shocks with digressive valving for bolt-in S197 fitment. Not gonna lie, pretty excited to get my hands on these and see what a true double adjustable does for both ride quality on the street & keeping the rear planted for autocross!
 

Norm Peterson

Corner Barstool Sitter
939
711
Exp. Type
HPDE
Exp. Level
5-10 Years
a few miles east of Philly
Hey Norm,

Appreciate the perspective about your own experience with the Koni Yellows. Out of curiosity, with your 220lb/in rear springs, what shock settings are you running on the streets of NJ?
I'll have to check, as it's been a while and I don't want to guess. This may take a day or so, as I'm not up to getting access to those in the rain.

I do remember that I had to back it down from the 3/4 turn up from full soft that I was using with the 140-ish OE rear spring rate, if that helps at all.


Norm
 
194
198
OP, you might want to consider removing your rear bar or going to an 18 mm.

This thread has my experiences with some of these different shock, spring, and sway bar combos focused on the rear axle: https://trackmustangsonline.com/thr...de-and-handling-comparison.16874/#post-260653

I found really nice improvements with removing the rear sway entirely - both in terms of daily driving ride and handling and settling of the rear end, as well as getting on power sooner coming off the apex on track. Check out post #5 and following in that thread. It was an eye opening experience for me.
 
OP, you might want to consider removing your rear bar or going to an 18 mm.

This thread has my experiences with some of these different shock, spring, and sway bar combos focused on the rear axle: https://trackmustangsonline.com/thr...de-and-handling-comparison.16874/#post-260653

I found really nice improvements with removing the rear sway entirely - both in terms of daily driving ride and handling and settling of the rear end, as well as getting on power sooner coming off the apex on track. Check out post #5 and following in that thread. It was an eye opening experience for me.
I knew I remembered reading about someone having a positive experience with the rear bilsteins awhile back, thanks for redirecting me back to that thread @stevbd

although I don’t have an 18mm rear bar on hand, I previously ran a 20mm rear bar early this season (for about 2 events). The car rode better with the 20mm bar/boss springs/konis for sure.

We had some issues getting the car to rotate in tight corners with the 20mm bar which we noted our build thread. Tried adjusting tire pressure and fully stiffened the rear konis, but it wasn’t enough for really tight autocross. Based on the bars we have on hand (24mm, 20mm, and strano 1 inch adjustable), the strano bar on its softest setting fell in between the 20mm and 24mm. This setup has been working fairly well but did degrade the ride somewhat, I know the rear bar is definitely correlated in this sense

with the refreshed trac lok diff, I’m wondering if we might have TOO much rotation. Was supposed to test the setup on 315s today, but NNJR was cancelled due to weather concerns :confused:
 
194
198
I knew I remembered reading about someone having a positive experience with the rear bilsteins awhile back, thanks for redirecting me back to that thread @stevbd

although I don’t have an 18mm rear bar on hand, I previously ran a 20mm rear bar early this season (for about 2 events). The car rode better with the 20mm bar/boss springs/konis for sure.

We had some issues getting the car to rotate in tight corners with the 20mm bar which we noted our build thread. Tried adjusting tire pressure and fully stiffened the rear konis, but it wasn’t enough for really tight autocross. Based on the bars we have on hand (24mm, 20mm, and strano 1 inch adjustable), the strano bar on its softest setting fell in between the 20mm and 24mm. This setup has been working fairly well but did degrade the ride somewhat, I know the rear bar is definitely correlated in this sense

with the refreshed trac lok diff, I’m wondering if we might have TOO much rotation. Was supposed to test the setup on 315s today, but NNJR was cancelled due to weather concerns :confused:
I don't mean to argue but aren't your goals of making the rear more "planted" versus "rotate more" kind of mutually exclusive, at least at a basic level?

Maybe dual adjustable dampers are a way to get it all. I don't have any experience with those. But at the risk of over-simplifying, my experience is that the best ride and most "planted" rear axle came with plenty of shock damping and relatively soft rear roll stiffness. And I'm actually faster on the tracks I drive with that setup. I think most of that advantage comes from the psychological advantage of knowing the rear doesn't step out much (avoid the cliffs lol), and being able to put power down sooner coming off the apex. But I am on the verge of too much understeer depending on the circumstances so I may add back an 18 mm rear bar.

Good luck and keep us posted.
 

Norm Peterson

Corner Barstool Sitter
939
711
Exp. Type
HPDE
Exp. Level
5-10 Years
a few miles east of Philly
I'm of the belief that the lower powered Mustang trims - say, with stockish power like my '08 or the later 3.7L sixxers like OP's - can benefit from slightly "looser" stiffness tuning. With anywhere from 70 to well over 100 ft*lbs less torque than what is available in any of the 5.0 versions, it's a different balance between lateral and longitudinal demands, and a different effect on the combination of tire slip + tire slip angle vs the tire's friction envelope (it's not exactly a "circle).

That' might be my roundabout way of saying that a 300-ish HP Mustang sits a little closer to the "momentum car" side of the "momentum to point and shoot spectrum" than the 400 HP and up trims.


Norm
 
I don't mean to argue but aren't your goals of making the rear more "planted" versus "rotate more" kind of mutually exclusive, at least at a basic level?

Maybe dual adjustable dampers are a way to get it all. I don't have any experience with those. But at the risk of over-simplifying, my experience is that the best ride and most "planted" rear axle came with plenty of shock damping and relatively soft rear roll stiffness. And I'm actually faster on the tracks I drive with that setup. I think most of that advantage comes from the psychological advantage of knowing the rear doesn't step out much (avoid the cliffs lol), and being able to put power down sooner coming off the apex. But I am on the verge of too much understeer depending on the circumstances so I may add back an 18 mm rear bar.

Good luck and keep us posted.
I think @Norm Peterson made a valid point in differentiating the slower pony’s being more like a “momentum car” vs the “point n shoot” style that seems to work in the higher horsepower cars.

My father/co-driver often calls my 3.7 mustang a fat miata with power (compared to his 128hp E street miata R package). Once we started focusing on keeping up the mid corner speeds and relying less on “powering out” of corners, we got significantly faster

All that being said, I think @stevbd is on the right track of decreasing the rear bar size back down to the 20mm once the double adjustables are installed in conjunction with the re-packed diff.

A Softer rear bar combined with better dampening has to equal better ride quality, right? Hahaha

Maybe we will kill two birds with one stone? Who knows?

I’ll keep you posted with my findings

-J
 

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