daveh

iTrader: (9)

I raised the car to the recommended ride height and still don't have enough rear travel. I'm hitting the bump stops even on the street.
I'm going to give all my measurements to Unitech to see if they can figure things out.
Changing ride heights is a royal pain. Both the front and rear threaded perches rotate with the collar so it's very hard to adjust, especially in the rears.
The rears are also making a lot of noise. I checked the upper mount and it was tight, so I'm not sure what's going on there either.

dnguyent

iTrader: (5)

Daveh,

Doesn't hitting the bump stops mean that compression damping is too low, and rebound damping is set too high? I have a mountain bike and had a motorcycle with two way adjustable shocks, and they alone were difficult to dial in. I can't imaging trying to dial-in a car's suspension system with two-way adjustment...lots of trial and error! Good luck with getting it all worked out...I wish I lived closer so I could check out your setup, or at least help out with the "debugging" efforts. I just signed up for the two-day event with NCRC...maybe I'll see you there.

"T4 is off camber and crowned..." I think you're talking about T3, right?

daveh

iTrader: (9)

Yes I guess that would be turn 3 that I described, I have trouble with large numbers.
A little rotation in turn 4 is ok. In fact, recently let a qualified racer drive my car a few laps and he purposely induced some rotoation there to get the car pointed up the hill (he got a little too much because my car oversteers any way). He also held T3 much longer to line it up better. I hate it when people get in my car and drive it faster than me in their warm up lap

This type of quick left right transition is where a good set of shocks come into play in weight transer. It is one corner that the old "in slow out fast" really plays a big part. You need to be on that gas/steady throttle to keep the rear in check there.

Unitech gave me all kinds of measurements to check on my car. I'll post back with my findings.

EnthuZ

iTrader: (2)

Glad to hear they are communicating with you.......

I'll try again tomorrow.

D'oh

Hi Ray,

It sure has been a while. I stopped going to the SCCA Autox (too crowded), and now I go with friends to their company that has it's own club.

Daveh,
Any more info on the similarity of your shocks VS the Koni yellows?

Later,
D'oh!

daveh

iTrader: (9)

My shocks are custom valved. I don't think they have anything in common with the off the shelf koni yellows.

I think the rattling in the rear is coming from the springs/perches. I can move them around a little with my hands. It's getting rather annoying.

daveh

iTrader: (9)

check your email. I'd like to compare our measurments. Unitech said they've sold many kits and I'm the only one with the rear shock travel issue. It sounds like you've got some issues to be ironed out too. Lets try and get to the bottom of this.

Do your rear perches have some free play? Mine move around (they even rotate when I try to adjust the ride height). I think thats the source of my rattle. Since you installed them yourself, can you refresh my memory and remind me if they are held in by anything or is it just the weight of the car that keeps them in place. Shoot me an email and we can take this offline.

EnthuZ

iTrader: (2)

I don't have my actual spring seat heights available, but I do have my current ride heights. F=25 1/4", rear=26". So, I'm down about 1 1/2" all around.

There's some spring pre-load on the rear height adjustor at full droop. There is nothing other than this pre-load holding it in place. I reused the OEM rubber thingy on the bottom of the spring.

My issue at Watkins Glen stumped the experts. They say it's NOT shock related. Yet, it never happened before I used them. Their best guess currently is that 1 1/4 degrees of negative camber in front is insufficient and/or my tires are chattering. I'm running RT615's, which are far from having the stick of an R compound tire.

Well, I'm off to my home track, Blackhawk Farms, in a few hours, so I can make better judgments.

John

iTrader: (17)

Bruce, what was your issue at Watkins Glen? The steering chatter over the concrete strips and bumps in the long sweeper (T5)?

Redfoot

iTrader: (25)

I seem to be getting a bit of noise from the rear spring perches which are just held in place by the spring tension. It’s a metal to metal contact with four little fingers from the cars frame holding the perch in place. I was thinking of putting some kind of large thin rubber washer between the two to quiet it down and readjusting the perch for the difference. I am also getting a lot of noise from the front springs when I turn etc.. I think I might install some torrington bearings to stop this noise. These bearings fit between the springs and the spring perches, elimininating spring stiction, and making ride height much easier to adjust because the perches turn more easily.

I would appreciate any information you guys come up with on this setup, so if you could send your emails to me also or just keep it in this or a new post. My first track event with these will be on Aug 6-7 at Gingerman so I won't have any good on track feedback until then.

daveh

iTrader: (9)

Enthuz and redfoot, how much rear shock travel do you have at this ride height? (the distance between the bottom of the bump stop and the top of the shock body). When I left Unitech, I had 3/4" of shock travel. Now I'm only lowered .8" and I have 1.75" of rear shock travel, but I'm still using that up on my daily commute). Unitech's car has 2.25" at this height. It seems as if I need to run the car at stock height to get the recommended amount of shock travel. This doesn't seem right.

Redfoot my fronts make some noise too when I go over large bumps, turn in a parking lot, or back out of my driveway. Honestly , that doesn't bother me much. The constant rattle in the rears is rather annoying to me and needs fixing up IMO. I can move the perch back and forth with my bare hands. I may just try some gorilla glue or a rubber pad to hold that sucker in place. Perhaps my tabs that are supposed to hold it in place have bent a little bit because I think the noise is getting worse. My first ride height change was easy, after that the whole darn perch rotates when I try to move the collars.

John

iTrader: (17)

Guys, the noise may be due to the pillow/mono-ball mounts you have. It's common and to be expected. The rears almost sound like your HyperCoil springs are too short... this is pure speculation though...

Redfoot

iTrader: (25)

the noise I get from the front is definately the springs twinging and twanging...the back could be the *****..

My rears really don't make much noise just an occasional bump or click so its not really a problem.

daveh

iTrader: (9)

I double checked my mounts and everthing was tight so I'm still leaning towards the spring. I could almost reproduce the rattle by moving the spring back and forth with my hands.
It is very hard to locate where noises are coming from without designating someone as "trunkboy" when you drive around, but I think the noise is stronger on the drivers side which has a looser spring perch.
The spring popping only happens under certain circumstances so I can live with that (its kind of like the clunking from the LSD I secretly like because I know the benefits), but the rear noise is constant and not quite as manly sounding

dnguyent

iTrader: (5)

The rear spring is pretty easy to remove. You might want to check the alignment of the rubber spring mounts, both top and bottom, and also remove the spring to make sure they are were not installed upside down. IIRC, the top of the spring is shaved flat, whereas the bottom isn't.

EnthuZ

iTrader: (2)

I like your term "steering chatter"!

It was more like an invisible co-pilot was yanking the wheel in the opposite direction I was turning, multiple times during the turn! Confirmed by Black Flag Jack who also drove my Z.

And, yes, it was most pronounced in T5, but also in the toe of the boot, and to a smaller extent on ANY bump!!!!

Driving on much smother Mid-West tracks I never experienced anything like this.

So, this $3000.00 suspension SUCKS!











J/K

After a DE at my home track, Blackhawk Farms, with a few of the BCR Harness Bar crew, I finally figured out MY problem. With the help of a tire pyrometer, tire pressure gauge, and a Porsche GT3 driver on Hoosiers, I am 90% certain I found the problem.
















Which is:


















TOO STIFF SWAY BARS!

My Cusco bars which I've had on my Z for over 2 years, and about 30 DE's, were found to be so friggin' stiff, that my once mostly independent suspension was turned into a pair of solid axels with the 67% stiffer F HyperCoil springs !!!!

I won't be back to a track for about a month to prove my conclusion with the set of Hotchkis bars I've been tripping over in my garage for a few months installed, but in a few days I'll post a longer explanation of how I reached this deduction.

Gsedan35

iTrader: (10)

Going back to the original thread on these coilovers, R&D car one was running 350EVO sway's set to med/soft and it was thought that car two was running same, set to med/med

Based on the latest stiffness data from 350EVO (5/2005) A 350EVO front way set at med offer's 10% more bar stiffness vs a oem 2003 bar. In the rear a 350EVO bar set at soft is -2% softer then the same oem bar, at the medium setting it's 27% stiffer.

So, "if" Hotchkis's bar spec's are accurate you should be able to set their front bar at soft and pretty much equal a 350EVO front bar that is set to med (+9% vs 10%).


Curious, when the "steering chatter" does happen, has anyone ran over the same spot after having made a dampning change? And if so was the behavior the same?

daveh

iTrader: (9)

tire hop is also attributed to too much compression. I would start with med/soft with the hotchkis. I've owned them and the evos and the hothckis are definately softer than the evos regardless of the published numbers. The hotchkis bar on full stiff up front gave me similar wheel hop and steering kick back like you are describing.
I actually feel a little of the same with my evos right now. I dropped my streeet tire pressure a little to counteract.

**Can someone with this setup please post how much rear shock travel they have?? I'm really stumped as to why I still have less then 2" of travel with only a .8" drop. ** this $3k shock really is useless to me!

exerpt from koni

KONI shock tuning guide
Suggested Adjustment Procedures For Road Racing Use
(from the KONI NA Factory Tuning Guide)


Adjusting The COMPRESSION (Bump) Damping Control (Very Important to do this FIRST!)

Bump damping controls the unsprung weight of the vehicle (wheels, axles, etc.). It controls the upward movement of the suspension as when hitting a bump in the track. It should not be used to control the downward movement of the vehicle when it encounters dips. Also, it should not be used to control roll or bottoming.

Depending on the vehicle, the ideal bump setting can occur at any point within the adjustment range. This setting will be reached when "side-hop" or "walking" in a bumpy turn is minimal and the ride is not uncomfortably harsh. At any point other than this ideal setting, the "side-hopping" condition will be more pronounced and the ride may be too harsh.

STEP 1: Set all four dampers on minimum bump and minimum rebound settings.

STEP 2: Drive one or two laps to get the feel of the car. Note: When driving the car during the bump adjustment phase, disregard body lean or roll and concentrate solely on how the car feels over bumps. Also, try to notice if the car "walks" or "side-hops" on a rough turn.

STEP 3: Increase bump adjustment clockwise 3 clicks on all four dampers. Drive the car one or two laps. Repeat Step 3 until a point is reached where the car starts to feel hard over bumpy surfaces.

STEP 4: Back off the bump adjustment two clicks. The bump control is now set. Note: The back off point will probably be reached sooner on one end of the vehicle than the other. If this occurs, keep increasing the bump on the soft end until it, too, feels hard. Then back it off 2 clicks. The bump control is now set.

Adjusting the REBOUND Damping Control

Once you have found what you feel to be the best bump setting on all four wheels, you are now ready to proceed with adjusting the rebound. The rebound damping controls the transitional roll (lean) as when entering a turn. It does *not* limit the total amount of roll; it *does* limit how *fast* this total roll angle is achieved. How much the vehicle actually leans is determined by other things such as spring rate, sway bars, roll center, ride heights, etc.

It should be noted that too much rebound on either end of the vehicle will cause an initial loss of lateral acceleration (cornering grip) a that end which will cause the vehicle to oversteer or understeer excessively when entering a turn. Too much rebound control in relation to spring rate will cause a condition known as "jacking down." This is a condition where, after hitting a bump and compressing the spring, the damper does not allow the spring to return to a neutral position before the next bump is encountered.

This repeats with each subsequent bump until the car is actually lowered onto the bump stops. Contact with the bump stops causes a drastic increase in roll stiffness. If this condition occurs on the front, the car will understeer; if it occurs on the rear, the car will oversteer.

STEP 1: With rebound set on full soft and the bump control set from your earlier testing, drive the car one of two laps, paying particular attention to how the car rolls when entering a turn.

STEP 2: Increase rebound damping three sweeps (or 3/4 turn) on all four dampers and drive the car one or two laps. Repeat Step 2 until the car enters the turns smoothly (no drastic attitude changes) and without leaning excessively. An increase in the rebound stiffness beyond this point is unnecessary and may result in a loss of cornering power. Note: As with the bump settings, this point will probably be reached at one end of the car before the other.

However, individual drivers may find it desirable to have a car that assumes an oversteering or understeering attitude when entering a turn. This can be easily "dialed-in" using slightly excessive rebound settings at either end.

Gsedan35

iTrader: (10)

Going with greater stiffness from sway's will offer what the chassis see's as a effective increase in compression dampning while cornering since that is the only time that the bars will leverage to the suspension (as will stiffer spring rates in steady state as well). Just wanted to see if the shock tuning can play a hole in containing the behavior and if he may have tried it. Curious when what is thought to be ideal compression dampning level's are found, do they seem to offer good low speed compression dampning behavior with the catch being that high speed compression dampning is on the sharp side?

John

iTrader: (17)

Well, like I told you at the track, adjustments had to be made on the compression and rebound. That's why I run my shitty JICs at nearly full soft at the track... Hotchkis too stiff? LOL, I'll leave it at that...

John, who runs at full stiff front and rear on the Evos, and loves it...

On a side note, I wish I had gotten some seattime with BFJ, as I probably would have learned something...

Again, what it boils down to is that it's all preference. There is always going to be subjectivity, hence the reason we have this ongoing suspension discussion (which I consider quite healthy), and the even more brutal brake pad disucssion.

OK... off to wash the Subaru... happy Sunday *****es!