First AutoX in a Very long time...

[Renesis07]

Ok well what shock/strut combo would work best for DD and the occasional cross? Koni str-t? Yellows? Eibach? Ect...

I run Koni yellows. Good starting point for all around performance IMO. Few guys in the area run similar setups and all like it.

 

[El_Tortuga]

Am pleased with the Koni yellows.

The 4.10s are to low for autocross, but I wouldn't worry about that right now. My 3.73s are A problem as well. Cant use all the power on most asphalt lots, so I'm starting in 2nd and shifting to 3rd as required. Easy fix to just grab a higher gear.

 

[claudermilk]

I'm also running yellows with Steeda Sport springs. They work ok for dual use. I'd like to rid in a car running proper coilovers to see the difference. The more hardcore guys here swear by them, and I would like to step up at a later time. The only thing I don't like is that the combo I have does not like a semi-washboard section of freeway near me at all (naturally I drive it every day :/ ).

The problem with the 3.73 is that need to make the ride the limiter/shift decision. Either way you are losing time.

 

[kcbrown]

I'm also running yellows with Steeda Sport springs. They work ok for dual use. I'd like to rid in a car running proper coilovers to see the difference. The more hardcore guys here swear by them, and I would like to step up at a later time. The only thing I don't like is that the combo I have does not like a semi-washboard section of freeway near me at all (naturally I drive it every day :/ ).

I have yellows with the stock springs, and there's a section of freeway near me that sounds much like the bit of freeway you're talking about (in my case, it's like the freeway is built of a bunch of badly made 20-ish foot sections joined together, like they couldn't figure out how to lay them flat or join them together properly, and the end result is that every section edge is a bump of at least a half inch in size). ETA: I've updated the section and bump sizes, because just yesterday I got caught in stop-and-go traffic on that very section of freeway and was able to get a good look at the sections. They basically represent a sawtooth pattern: the sections rise for about half an inch or so and then, at the interface, abruptly fall by that same amount, as if they were all individually laid down at a slight incline on a flat surface.

The Koni + stock spring combo handles that better than anything else I've seen so far (though I suspect it's possible to do better, and perhaps even a lot better). Better than KW v3 coilovers, even. I'd love to see how Bilsteins handle it, as well as top-grade coilovers like MCS.

What do you have your rebound set to for daily driving?

 

[Renesis07]

I don't daily drive my car but I have mine set at 1.5 up front and 1.25 back (turns from full soft). It's not that bad but certainly not that smooth either. You can always run them full soft for the streets, I haven't tried it yet but I heard that it rides pretty decent for daily use.

 

[Norm Peterson]

I don't daily drive my car but I have mine set at 1.5 up front and 1.25 back (turns from full soft). It's not that bad but certainly not that smooth either. You can always run them full soft for the streets, I haven't tried it yet but I heard that it rides pretty decent for daily use.

That's about what I've been running for track sessions. Street driving when it's just me is 1/2, maybe 3/4 turn less than that, and when my wife is a passenger for more than just a few miles I'll dial them back to about +3/8 front and +1/8 rear.

Stock 2008 GT springs.


Norm

 

[kcbrown]

That's about what I've been running for track sessions. Street driving when it's just me is 1/2, maybe 3/4 turn less than that, and when my wife is a passenger for more than just a few miles I'll dial them back to about +3/8 front and +1/8 rear.

I have mine dialed in at 1/4 turn up front and 5/8 turns in the rear. That gets me about 75% critical damping on both ends. Seems to work well on the street. My instructor seems to think my car handles well, so I guess that means they work well enough on the track, too.

This is on stock 2014 Track Package (a.k.a. Brembo Brake Package) springs (131 lb/in in the front, 167 lb/in in the rear).

 

[claudermilk]

I've had my Konis at 1.5 turns up from soft. I left it there after the last autocross to see how it handles DD; it's doing well enough I'm not in a hurry to go change it. I've also run them at full soft (slightly up from the stop after reading about possible issues running at the stop). It does ride smooth for a lowered car on stiffer springs. That bad section of freeway pisses off the car seemingly no matter the setting on the Konis. Maybe Bilsteins or higher-end coilovers would work better; I have a feeling that the spacing & severity of the bumps there combined with the car's wheelbase & typical speeds just just a bad combo. Everywhere else it's fine.

 

[kcbrown]

I've had my Konis at 1.5 turns up from soft. I left it there after the last autocross to see how it handles DD; it's doing well enough I'm not in a hurry to go change it. I've also run them at full soft (slightly up from the stop after reading about possible issues running at the stop). It does ride smooth for a lowered car on stiffer springs. That bad section of freeway pisses off the car seemingly no matter the setting on the Konis. Maybe Bilsteins or higher-end coilovers would work better; I have a feeling that the spacing & severity of the bumps there combined with the car's wheelbase & typical speeds just just a bad combo. Everywhere else it's fine.

Sounds like that section of the freeway might be similar to the section I was talking about (I've updated it based on observations I made yesterday). The section I hit is particularly challenging because the bump rise time is so long, but the bump fall time is very short. At freeway speeds, you're hitting about 4 or 5 of them per second.


1.5 turns from soft in the rear puts you at 125% of critical damping in the rear based on the Steeda Sport spring rates and the dyno data from my Konis. You might want to turn the rears back down to about 1 1/8 turns, which should put you very near critical damping. Your front is at about 75% critical damping right now. If you want the front and rear to match in terms of damping on the stiffer side, then you'll need to crank the front to full stiff (which will get you to 94% critical damping) and reduce the rear to 1 1/8 turns.

Might be worth trying at some point just to see what you get in terms of handling and ride. Of course, if you're trying to control transient weight transfer by changing the front versus rear damping, then getting them in balance might not get you the handling you want.

 

[frank s]

I've had my Konis at 1.5 turns up from soft. I left it there after the last autocross to see how it handles DD; it's doing well enough I'm not in a hurry to go change it. I've also run them at full soft (slightly up from the stop after reading about possible issues running at the stop). It does ride smooth for a lowered car on stiffer springs. That bad section of freeway pisses off the car seemingly no matter the setting on the Konis. Maybe Bilsteins or higher-end coilovers would work better; I have a feeling that the spacing & severity of the bumps there combined with the car's wheelbase & typical speeds just just a bad combo. Everywhere else it's fine.

Years ago, when I flat-towed my MGB roadster to events, there was an evil resonance among the wheel-bases of the tow (1967 Dodge Dart) vehicle and the towed, the concrete pavement sections' length and seam heights, and speed. At the 55-mph towing limit, the forces resulted in the tow-link's banging on the vehicles like a sledge hammer. No other speed caused such violence in the same place, and it never occurred in any other place from Santa Maria to Riverside to Rosamond to Holtville.

The bad place was on I-8 eastbound in La Mesa, from about Baltimore to the crest above El Cajon; worst was right by the place where Drew-now-Penske Ford sits. I'm wondering where your bad section of freeway is.

None of my modern Mustangs have objected to particular sections of freeway, except the little samba-dance moves the newest one makes on the 52 westbound from the crest to Santo Road. Tramlining with the rear wheels but not the front. Weird.

 

[BigBlue05]

what do you guys with sportlines adjust your koni yellows to?

 

[JerryZ]

I still have my Koni Yellows & BMR Handling springs in the boxes waiting for some decent temps...kcbrown, I have read up that you need to adjust to near critical damping. How you I figure where critical damping is for my setup? The handling springs are 240F/200R linear. Thanks!

 

[kcbrown]

I still have my Koni Yellows & BMR Handling springs in the boxes waiting for some decent temps...kcbrown, I have read up that you need to adjust to near critical damping. How you I figure where critical damping is for my setup? The handling springs are 240F/200R linear. Thanks!

240 lb/in front critical damping computes to 51.5 lb/in. That's beyond the maximum damping capability of the front Konis. Fortunately, what you probably want is something like 65% to 75% critical damping.

Here's the Koni damping data. F is front, r is rear, and "pass" is the number of 1/4 turns from full soft:

location | pass |        rate        
----------+------+-------------------
 f        |    0 | -28.5252852953472
 f        |    1 | -28.7219906633222
 f        |    2 | -29.9974361032989
 f        |    3 | -32.7627499977644
 f        |    4 | -32.2284162702381
 f        |    5 | -34.1830667583725
 f        |    6 | -35.7649128091112
 f        |    7 |  -40.603480414513
 f        |    8 |  -42.288092948718
 f        |    9 | -44.3218941610925
 r        |    0 | -20.9190039082295
 r        |    1 | -23.3490962959941
 r        |    2 | -25.8289492753623
 r        |    3 | -28.8198268077564
 r        |    4 | -32.6267659084575
 r        |    5 | -39.6733845662011
 r        |    6 | -45.7631262193423
 r        |    7 | -53.8557304493514
 r        |    8 | -58.5020354240815
 r        |    9 | -68.3945583427389

The front Konis max out at 44.3 lb/in/sec. For you, that's 86% critical. 70% critical is 36 lb/in/sec, which is 1.5 turns from full soft.

To get the rear to match, you would need to set for 70% of critical there. Critical for 200 lb/in is 39.3 lb/in/sec. 70% of that is 27.5. That corresponds to about 5/8 of a turn from full soft.

That should get you in the ballpark. You can tweak it from there to suit your tastes.




(Sent with Tapatalk, so apologies for the lackluster formatting)

 

[JerryZ]

Thanks very much for the info KC; How do you come up with the 51.5 and 39.3 lb/in. if it's not too much? I'll have to look further into it and try to learn a bit. Most interesting. I'm anxious to get all my parts on and see what I've got.

 

[Norm Peterson]

Any decent text covering damped vibrations should cover it.

In a nutshell, it's C = 2 * SQRT( [wheel rate] * [corner mass] ), where mass is expressed in 'slugs' and you have to keep the units all consistent.

More conveniently, C = SQRT( [wheel rate (lbs/in)] * [corner weight (lbs)] ) / 9.83


I think if you use 3900 lbs (car + driver, as using car weight alone would be meaningless, no?), 54% front weight, and 240 lb/in and 200 lb/in wheel rates (ignoring motion ratio effects) you'll end up close enough to kc's numbers.


Norm

 

[JerryZ]

Thanks Norm; I'll see if me and my calculator can digest it.

 

[KoolerSL2]

Ok guys from all I've read, which dampers would be best to use with my sportlines that won't break the bank and can control the springs?

Eibach pro damper?
Koni str.t?
Koni Yellows?

 

[csamsh]

Bilsteins

 

[kcbrown]

Ok guys from all I've read, which dampers would be best to use with my sportlines that won't break the bank and can control the springs?

Eibach pro damper?
Koni str.t?
Koni Yellows?

Normally, it'd be between the Koni Yellows and the Bilsteins, and which one you go with would depend on whether or not you need to be able to adjust the transition response of the car.

But in the case of Eibach Sportline springs, the amount of lowering is 2 inches in the rear and 1.6 inches in the front, and the spring rates are rather high.

Koni Yellows in the front are, in terms of their damping (not their longevity in the face of lowering by the amounts we're talking here), good to about 400 lb/in in the front. Their damping curves in the rear are such that they'll be able to control a lot more in the rear, but everyone here is saying that anything more than about 300 lb/in in the rear will ride like a dump truck no matter how good your dampers are, so the rear adjustability is mainly going to be useful for adjusting transitional understeer/oversteer.

The Bilsteins are going to be better for your application, because they're already designed to handle compression amounts that go past what the Konis (or any strut designed with the same external dimensions and attachment locations as the stock ones) will be able to (reportedly) reliably handle.


If you were on springs that didn't lower the car as much, the Konis might be in the running (probably depends on what the actual spring rates are as well. Lowering the car causes a cascade of effects which result in the need for much higher front rates than you might expect). But with the Eibach Sportlines (front rate progressive, 183-296 lb/in, rear rate progressive, 217-302 lb/in, all per Eibach's web page), you'll need a damper that is designed with that much lowering in mind.

Note that this message at mustangforums.com suggests that the Sportlines are problematic in the rear. Whether that really is the case is something only someone with the springs will be able to say.

 

[kcbrown]

Thanks very much for the info KC; How do you come up with the 51.5 and 39.3 lb/in. if it's not too much? I'll have to look further into it and try to learn a bit. Most interesting. I'm anxious to get all my parts on and see what I've got.

You're welcome.

I describe specifically how I arrived at that in detail here. Norm correctly described the process, but you also need the numbers I used to get the same answers I got. Note that I did account for the motion ratio in the front. I used a motion ratio of 1.0 in the rear for two wheel bump since I don't know what angle the rear shocks are at. It should be reasonably close to correct.