[LOLSTi]

Enough thread pollution. Great work Stretch.

 

[twiSTies]

Bilstein PSS-9 vs. KW V3 was a nice read, stretch. Those two really have my eye since they can mate up to the stock style tophats.

 

[SWortham]

By the way, I found something interesting when I was doing research on available strut options for another car several years ago. I found that KYB would gladly tell me the damping force at a set velocity but would not provide me with a damping graph. It's not ideal but it at least gave me some basis for comparison and I was able to compare them to the OEM struts they were designed to replace. I wonder if Bilstein, Ohlins, or some of these other companies in question would at least give us that much.

With that limited information I found that the KYB GR-2's had significantly higher compression damping but only slightly higher rebound damping. As I later found out, that's not a good combination if you're planning on installing lowering springs with them. And I could feel that the lowering springs I used with the GR-2's were poorly matched.

 

[stretch]

With that limited information I found that the KYB GR-2's had significantly higher compression damping but only slightly higher rebound damping. As I later found out, that's not a good combination if you're planning on installing lowering springs with them.

^ Good to know.

I have read that the as you increase your spring rates, you may actually want less bump resistance since the spring is already providing more resistance to bump. Of course, rebound should increase to cope with that increased spring load.

I think the GR-2's are usually just OE replacements designed for OE springs. Perhaps the added bump was to help turn-in a little bit. But without increasing rebound resistance, I don't see how they could be any better with firmer-than-stock spring rates (as you found out).

 

[SWortham]

^ Good to know.

I have read that the as you increase your spring rates, you may actually want less bump resistance since the spring is already providing more resistance to bump. Of course, rebound should increase to cope with that increased spring load.

I think the GR-2's are usually just OE replacements designed for OE springs. Perhaps the added bump was to help turn-in a little bit. But without increasing rebound resistance, I don't see how they could be any better with firmer-than-stock spring rates (as you found out).

My thoughts exactly. For these reasons Koni Yellow's work very well with lowering springs seeing as how rebound is highly adjustable and compression is typically closer to OEM. And I imagine you'd see the same in the Ohlins struts, Bilstein (RB320) struts, and probably the new struts RCE & KW are in the middle of developing as well.

 

[stretch]

Woo woo, more graphs. I plotted some of the above graphs together in the same scale so that they're easier to read- now it's easy to see how stock compares to Koni and Koni compares to Whiteline. I only plotted the Whiteline Group4 Circuits (softer versions) because they were most popular and renown for their ride quality, and I only plotted them adjusted to fully firm because, well, even there they were still the softest dampers on the chart! You can see that Koni's on full soft are reasonably close to the stock dampers (except for having much more bump resistance up front) but get way, waaaay stiffer from there.

The last graph is what I currently run (stock front, Koni rears) compared to Whiteline. I did this for my own sake but figured I'd post it here anyway. I've got just a smidge more rebound front and rear than the stiffest setting on Whiteline Group 4's, except I'm running much softer stock spring rates. No wonder it feels so overdamped- there's probably way too much rebound in the stock struts for the soft springs. The fix? Firmer springs to combat all that rebound.

I've said in the past that a stock STI is underdamped. And it is, if you're on the bump stops, because they more than double your effective front spring rate to over 500lb/in once you hit them (which all STI's do). It is underdamped there. Off the bump stops where the spring rate is 224lb/in, the struts feel overdamped. Ah, it all makes sense now, doesn't it!

So, after starting this thread and looking at the charts, I bought Ground Control springs, 350lb/in front and 300lb/in rear. Those spring rates are correspondingly a little more than the Whiteline rates, so I think it'll all be a great match! I can't think of a reason why my inexpensive Ground Control / stock / Koni setup wouldn't behave similarly to the Whiteline coilovers (and probably others) since the dyno curves are reasonably close. I'll be running slightly firmer springs and have a tiny amount of extra high-speed bump. But the big difference is that I won't have the excess bump travel required to lower the car much; Whitelines have much more suspension travel than stock. Even with shortened bump stops, I'll be stuck at near-stock ride height since I want to keep a sufficient level of travel. Whatever. I'm stoked just the same.

 

[spazegun2213]

very nice, i like your setup a lot, but i wish we could add koni's to the front as well.....

 

[stretch]

Horrible mis-matching of cheap shocks has been discussed before (here: http://www.wincom.net/trog/autocross_secrets6.html), but I've never seen such an obvious visual!

Check this out the shock dynos below: Tri-Point Engineering (a racing team and Koni rebuilder) dyno'd some K-Sport struts for the 240Z, one of the most popular applications for K-Sport. Both front and rear, the one shock on full stiff still wasn't as firm as the other on full soft. That's the terrible quality control you often hear about but can rarely actually demonstrate.

Well, here's the proof: http://www.msprotege.com/forum/showthread.php?t=123666252 (The images are mirrored here, but that thread is worth checking out.)

If you read further into that thread, Tri-Point dynos some off-the-shelf Koni's and shows them to be within 10% of one another (with a better shape to the curve, too, as you'd expect).

My own experience with K-Sports (actually D2's, sister brand) on a Mazda6 gets even worse: they lasted a month, and the redesigned replacement rear shocks (an answer to the quickly wearing rear) completely lacked bump resistance. It was an outsourced Tokico non-adjustable twin-tube (I paid for an adjustable design) but with one of the two internal valves completely absent!!!

 

[twiSTies]

^damn.

 

[SWortham]

^ Well that illustrates that point nicely. I could just imagine what that would feel like driving a car with dampers that were that different from left to right.

 

[AndrewSS]

Just thought I would throw some information in here... take it for what its worth... I dont claim to be much of a suspension guru/tuner, so keep that in mind, lol

I have 500/400 RCE t2 coilovers. The car is setup for STU in autocross. I have WL 27/29 FSB (29 set), 22/24/26 RSB (24 set). Front camber is: -3.2 and rear is -1.0 Tires are: yokohama neova ad07's (245/40/17 on 17x9's)

Anyway... I have set them twice.

My first autocross was at a lot that isnt that smooth, we have a fairly large drainage "hump" on the lot. I set the T2's to:

Comp: 6 clicks from full stiff front and rear
Rebound: 9 clicks from full stiff front and rear
(6 clicks = 1 turn, there are 2 full turns for compression, and 3.25 turns for rebound)
Incar footage: http://www.youtube.com/watch?v=VIuELVbI5Zs

Today, I was at a smoother lot, very smooth in fact. Settings were:

Comp: 3 clicks from stiff front and rear
Rebound: 3 clicks from stiff front, 4 clicks from stiff in rear
Incar footage: http://youtube.com/watch?v=QAW1uNokvdM

----

I felt pretty good both days, I felt like the car handled bumps very well the first autocross event, even with the notorious "hump." At the autocross today I liked the firm settings, I didnt notice any bad side-effects, granted the lot was smooth... As I get more and more seat time with the new setup I will be able to relay more useful information, thats for sure. Yet another lot will be next weekend, its decently smooth, it does have a pretty notorious bump in it, that upsets many cars. We will see how it goes, I plan to run the current settings (stiffer, from today) there as a baseline... and adjust from there after the first run to see what I like.

I will let you know.

-Andrew

(edited with incar... I dont really know what its worth, I suppose it should show some of the differences in the lots...)

 

[Rixsti]

Yes thank you!!

 

[ace996]

OK...great post, Andrew - here's my $.02...

Autox today. Lot was very loose...plenty of gravel from degrading asphalt and sand still present from the winter...the lot isn't cleaned...ever...

I ran the T2s(500/400) with the same WL bars and settings as above.
Front camber is -2.5...rear is -1.5
Tires are Kumho Ecsta700s...the older ones...245/40/17s all around.

The compression is 6 clicks out from full stiff front and rear.
Rebound was 6 clicks out from full stiff front and rear.

I found a loose rear and needed to keep the rear tires down longer on trail-brake, as the rear was getting too loose on the very slick/gravelly surface. I backed out the rear 3 more clicks (9 total) on rebound and that helped a great deal.

I wound up posting 2nd fastest time of day...a little pissed it wasn't FTD, but some clown decided he was going to trailer his Porsche 914-6 to the event -
completely gutted...no glass...no lights...nothing but frame, engine, skins, seat, and cage. Car weighed 1800lbs and ran on 245s all around.

A good day, learned some about the car and set-up, but I'll need to get back to the usual lot to really work on settings.

I've never been a big believer in running very high compression, as our lots/tracks in the N.E. are usually quite bumpy. With the rates I'm currently using and the WL bars, there's not much lean, so I'm glad to absorb the bump stroke.

Be good,
TomK

 

[AndrewSS]

^ Hrmmmm so you preferred a bit less rebound in the rear eh... I have been balancing a bit less back there too...

 

[ace996]

Andrew,
For the surface this weekend, I needed to keep the rear tires on the ground longer while trail-braking...so less rebound was the answer. Who knows...dropping the rear 1/2 inch more may do it, too...and it'd help with the weight bias as well. I may try going a little lower in the rear...

Crazy this adjustable suspension world is...last time I had adjustables, it took me a good year to find the "sweet" spot and another year to improve on it.

I'm going to do some playing at my next trackday. I've been using a "PerformanceBox" from VBox to keep track of lap-times and datalog the handling/performance parameters. Some real careful analysis at next Pocono event should show me where to look to find some more in these T2s...
Feel is one thing, it's gotta "feel" good for us to be comfortable, but then it's crunching numbers to find that last bit that's left....

A long road ahead awaits....but it is a great journey...

Be good,
TomK

 

[Bootsie]

This is a great thread- thanks for all the effort, Stretch and all others.

From it, I am trying to use it to figure out what I do not like about the stock suspension. I see this as on topic, because I think that figuring the stock setup's problems will help us choose the best dampers and other suspension parts. Anyway....

The main handling problem with the STi (as I see it)
The problem is in turns. On smooth roads the car is fine, and feels well planted. (no surprise) The problem is on turns that are bumpier. Here, when the car hits a bump, it seems to drop quickly in the suspension travel. Then the car seems to get soft, like it can no longer support the g-forces that it is well able to resist when it is higher in the travel. Basically, the suspension does not seem to work well once it is flexed down.

Note that I feel this in both high and low g-force turns, and I have experienced it in every Subaru I have driven. (STI, WRX, WRX wagon, Legacy, etc...) The only place I do not feel this issue is on dirt and snow, where there less available grip. (In these situations I think most Subarus handle very well.)

My question is what is causing this? I have a few theories, and I am hoping some of you could shed some light on this. Here are the options I see.

1. It is a geometry problem (the car's effective spring rate ratio is digressive)- as the car goes through its travel, it puts more force on the strut, which makes the car feel softer in the upper part of its travel. (I am not an engineer and am only guessing on this theory.) This seems likely to me, because the fixes I have liked best so far (progressive springs, stiff front sway bar, ALK) all seem to make the car more controlled through the higher part of its suspension range. (If so, it also makes me wonder if ball joint extenders would improve this ratio.) As I see it, this option would mean we would have to pick shocks and springs that are able to compensate for this digressive issue.

2. It is a geometry problem related to camber curve. I think this is less likely (even though it is probably still an issue), because these problems show up (especially on linear springs) as much on low g turns as they do in high g turns. (With both stock and pink springs, my car felt like it could barely stay on the highway {I live in a very mountainous area} at low g force turns- in fact, the pinks were much better at high g turns than at low ones.)

3. The car has too much rebound damping- the wheel does not get "to the ground" soon enough. (low, mid or high speed?)

4. The car needs more compression damping- the wheel needs to be able to hold its position more. (Low, mid or high speed?)

5. The car needs a more progressive spring (related to #1). While this may not be ideal, it may be the best real world solution. (It might also explain why so many people like RCE's springs, and possibly even explain why rally guys like the progressive rate of the DMS shocks.)

Looking forward to everyone's insight and opinions, and hope you find it related to the subject of shocks.
J

 

[Bootsie]

Any opinions? Anyone?

Thanks,
J

 

[ace996]

This is a great thread- thanks for all the effort, Stretch and all others.

From it, I am trying to use it to figure out what I do not like about the stock suspension. I see this as on topic, because I think that figuring the stock setup's problems will help us choose the best dampers and other suspension parts. Anyway....

The main handling problem with the STi (as I see it)
The problem is in turns. On smooth roads the car is fine, and feels well planted. (no surprise) The problem is on turns that are bumpier. Here, when the car hits a bump, it seems to drop quickly in the suspension travel. Then the car seems to get soft, like it can no longer support the g-forces that it is well able to resist when it is higher in the travel. Basically, the suspension does not seem to work well once it is flexed down.

Note that I feel this in both high and low g-force turns, and I have experienced it in every Subaru I have driven. (STI, WRX, WRX wagon, Legacy, etc...) The only place I do not feel this issue is on dirt and snow, where there less available grip. (In these situations I think most Subarus handle very well.)

My question is what is causing this? I have a few theories, and I am hoping some of you could shed some light on this. Here are the options I see.

1. It is a geometry problem (the car's effective spring rate ratio is digressive)- as the car goes through its travel, it puts more force on the strut, which makes the car feel softer in the upper part of its travel. (I am not an engineer and am only guessing on this theory.) This seems likely to me, because the fixes I have liked best so far (progressive springs, stiff front sway bar, ALK) all seem to make the car more controlled through the higher part of its suspension range. (If so, it also makes me wonder if ball joint extenders would improve this ratio.) As I see it, this option would mean we would have to pick shocks and springs that are able to compensate for this digressive issue.

2. It is a geometry problem related to camber curve. I think this is less likely (even though it is probably still an issue), because these problems show up (especially on linear springs) as much on low g turns as they do in high g turns. (With both stock and pink springs, my car felt like it could barely stay on the highway {I live in a very mountainous area} at low g force turns- in fact, the pinks were much better at high g turns than at low ones.)

3. The car has too much rebound damping- the wheel does not get "to the ground" soon enough. (low, mid or high speed?)

4. The car needs more compression damping- the wheel needs to be able to hold its position more. (Low, mid or high speed?)

5. The car needs a more progressive spring (related to #1). While this may not be ideal, it may be the best real world solution. (It might also explain why so many people like RCE's springs, and possibly even explain why rally guys like the progressive rate of the DMS shocks.)

Looking forward to everyone's insight and opinions, and hope you find it related to the subject of shocks.
J

This is a subject worthy of it's own post, but I'll throw in my thoughts.


Both 3 and 4 would be better addressed with stiffer springs...Pinks, RCEs, ect....
Its not that there's too much rebound and not enough compression...I believe it's actually the opposite - too much compression, too much rebound-stiffer springs would cure that
Start another post....

Be good,
TomK

 

[rbahr]

I have some Dual adjustable Ohlins data in spread sheet form is anyone is interested in posting it for me...

Ray

 

[4banger]

I have some Dual adjustable Ohlins data in spread sheet form is anyone is interested in posting it for me...

Ray

You should PM Stretch about it.