Matt_27

For sure, that was probably the biggest difference.

Ramo7769

Excellent. My want is strong.

Ramo7769

Lateral Load Transfer Update: I seem to have taken a step backward. StranoParts 1 5/16" front swaybar with no rear bar was awesome in Oscoda and had me scrambling to get the car to rotate in Wilmington.

Went back to Oscoda to tune the car with rear bar and leave options open to loosen the car up on different surfaces... It went poorly. I could get steady state tuned well, but transients were very unstable. That's with the same damping settings... significantly higher rebound set on the front end. Also didn't put down power as well. Also played with rear toe. I found a similar effect to bar changes. Not solving the power down issue, nor the general transient issue.

I am regrouping and aiming to run no rear bar at nationals. I am doing what I can to heed Borg's advice of having the option to loosen the car in Nebraska. So in addition to the Strano 1 5/16" front bar, I picked up a ZR1 bar straight from the dealership which is the same OD and thinner wall. I'll also be picking up a buddy's C6 Z06 bar which is 1 1/4" just in case. I figure that should cover the bases for steady state balance to avoid scrambling again.

Braking Update: I still have Hawk HPS up front and just put HP+ on the rear. I found substantially improved braking performance. Less ABS intervention, less hard pedal. Not surprisingly more loose on entry. It was a good change. But I will probably be replacing the front pads as well before nationals for something in between HPS and HP+ for added stability.

dhowdy

Could you measure the length of the straight part of the bar and length of the arm of the bar? These will have a greater effect on rigidity than the thinner wall. A & B from the below diagram, C would be an interesting data point too.



That would let us calculate roughly the relative stiffness of all the bars so you can back your adjustments with numbers. I think they're all the same material, whatever it is, but I'm just assuming there... that would also matter.

strano@stranoparts.com

I have to recommend you slow down, or even stop. You are going to tune yourself right down the drain Andrew.

As I stated and you found, Oscoda is not Wilmington, and neither are Lincoln. I'm not sure Lane has been to Wilmington either. I can tell you that my car in Lincoln on Rival S's was bitch loose in the Spring. So I dunno if I'd just make a blanket statement like that. Also Lane likes his car looser than I like mine. In fact when I drove his it was way too loose for me and I chased it everywhere and he felt it was tight.

Step back 1 or 5 steps. Transients are the domain of the shocks. Of course bars will change that, but if you got the balance good then with the dampers and pressures and even some toe you should have been able to tune that stuff in. If power down is suffering there are things to do. Full tank. make sure the shocks aren't all bound up at the bushings (I have both spherical lowers and really trick delrin uppers in mine)

Also the C6Z bar is 1.25" or 31.75mm it is actually 31mm and made of some light material too. The ZR1 bar is 33mm, but mine is actually 33.3, or 1-5/16" and yes the ZR1 is a thinner wall.

And again, what rear bar are you trying to tune around? If you have a Z06/Z51 23.6 you could try my thin wall 1" (really thin wall, soft is softer than that bar). Or even a non Z51 19mm bar (as I recall).

In between HPS and HP+ would be HPS 5.0 or Ferodo's. But be careful there. My car with HP+ rears became a tail sliding mess on rougher surfaces (which Oscoda isn't) because the stickiness of that pad doesn't release the rotor cleanly. So when the ABS has to do it's thing a lot on less than smooth pavement it tries, the the pads are still hanging on.

Ramo7769

Going back to no rear bar is how I am attempting to step back to the state where I was fastest in the car (comparing PAX to my Detroit brethren in Oscoda). That was the StranoParts 1-5/16" up front set to soft. Almost zero rear toe. (2mm or so from my strings) I'll also have the 1-5/16" and ZR1 bar on hand in Nebraska. That and rear toe I feel should be all I need to get the car balanced steady state.

I actually have the early Z51 rear bar (1999). I'd have to double check it, but I believe it is around 21mm. It is definitely softer than the C5 Z06 rear bar though. I've tested that and couldn't drive the car straight.

This is what was most confusing to me. I basically ran out of shock adjustment to tune the transients and that had me banging my head against the wall. I had the balance pretty damned close to where I like it steady state with bars and toe. 99 z51 rear, 1-3/8" set soft. But couldn't hang onto it in transients...

So, I dialed in more rebound on the front and dialed back in the rear and the change was subtle. I went as far as full stiff front and 1 sweep off of soft in the rear and couldn't make it work. Also added a flat of rear toe-in per side and the change was more noticeable steady state. I never found a good transient balance so I added more steady state push to compensate and never got the car working well.

I had more transient stability with the no rear bar setup and front shocks set to 1 sweep off of full stiff and rear shocks set to a mid-setting. That's why I'm back tracking. I will check them out to see if they can be binding in the rear. I still have the stock rubber lower bushing.

The only other thing is that I'm going to try to get to Lincoln early to take the fronts Konis off and have them checked out. I purchased the fronts used from Rasmussen which he ran on an FS Mustang. Maybe they're not fully doing what they should.

Seems like a perfect time to pick up the Ferodos for the front axle. But, they're expensive as you know. And I have enough contingency to get HPS 5.0 fronts to try for free.99. So I may start there. Though, I am curious about the Street/Race pad out now that also claims to work well at low temps.

That's interesting about the release characteristic with HP+. Not sure I can get around it any time soon due to what I have on hand and the brake proportioning I'm trying to obtain with pads.

Also, thank you, Sam. Your input is helpful. Especially with the shock tuning since I'm still new to that. Any more thoughts on that now that I explained more where I'm at? Once I get them checked out my only thought was to start from scratch on a T&T with them closer to soft, dialing the rebound up as needed. Maybe "the front is writing a check the rear can't cash" as it were.

Ramo7769

Good input. Dimension B is mostly dictated by the mounting parts on the car. There is negligible difference there between the StranoParts bar and OE ZR1 bar. Dimension C is important. It's what gives us the difference we refer to as the soft setting and stiff setting on a StranoParts bar. Getting a rough measurement comparison, the most I can say is that the OE bar has a dimension C that is very close to the StranoParts bar. But also consider, when moving the endlink mounting location away from the end (Strano full soft, or OE location), the motion of the sway bar arm does not follow suspension travel as closely. It is a net effect of gained stiffness, but not as much as you'd think by simply measuring these dimensions. They ignore how the bar comes to play in the suspension system. See the attached picture of the StranoParts bar at full stiff for example.





I have to disagree that these dimensions will affect stiffness more than wall thickness. The mounting points are all the same, so the potential of changing A, B, or C is possible, but very limited... Overall small compared to diameter and wall thickness. Subtract ID from OD in your equation for the hollow bar and this is the only term in the equation that is put to a power of 4... while also carrying a coefficient that is orders of magnitude higher than all other terms. It matters a lot for overall stiffness. And in this case, does not affect the way the bar acts on the suspension. My dominating concern is that it will be too soft if anything. I'm hoping it's not a world of difference from the 1-5/16" bar.

dhowdy

So my understanding: Dimension B is not primarily effect by the mounting points. Theoretically the sway bar would still work with a single mounting point assuming no deflection of the bushings? Obviously we'd run into bending which would alter overall stiffness and thus why I said not primary effect, but I think for purpose of stiffness calculation we need to look at the length of the arm between the bends.

The end links are rigid, while the sway bar twists. A is the length of the lever arm that effects the twisting about the bar of length B. C is brought into the equation to account for flex along that lever arm.

A and C are both changed by changing the bar setting/mounting hole.

This part is interesting. The effect would be seen more at a great angle between end link and bar, but I think within the normal range of motion we can approximate pretty close to 1:1 force from end link to bar rotation.

I was saying that OD has more influence than wall thickness (specifically the thinner wall of the ZR1 bar), but yes you're right.

I think you'll be just fine. I have the ZR1 bar front, 1" bar rear set to soft on my car, and the steady state balance is great. I also previously ran the car with a (borrowed) 1 5/16" Strano bar and it also felt good... honestly Strano bar felt softer but the surface where I ran it was also better. The car originally had a 1 3/8" Hellwig bar on it that was a disaster. Previous owner had the car set up for road racing and I've been trying to get the push out of it all season.

strano@stranoparts.com

A few things to note. I am going off what I know works and wonder if something else isn't amiss. Also not worried about what you end up on really as long as it works. I'd love it to be my stuff but if you can't get it where you want it, that's ok too. However, I'm not seeing much detail about what the car is or isn't doing in all the different guises. A little but not enough for my needs.

BTW, if you have a car that is snappy at the tail with a pretty stiff front setup, more rebound could be worse, not better. And it sounds like that's what you did trying to settle the back and that doesn't always work, especially as the wheel rates go up. I recall running my Camaro in FS back in the day. We all ran at the time, hollow 32mm front bars and the front rebound pretty much full stiff. I slapped on a solid 35mm bar and by the time I got to the 3rd move in any slalom type thing the rear was just checked out and gone. The front reacted so quickly that the rear couldn't keep up. Softening the rebound was much better.

Also things never stay static. When I went to A7's from A6's, I softened my front shocks because at a high setting I had a similar effect to the Camaro with the bigger bar. Front was hyperactive, rear was out of phase. Same car, my Z06 on Rival S.... I run the front shocks at the other extreme, damned near full stiff as the tire is that much different in it's reaction. Same car every other way. More shock all around, much more in the front.

While possible the front shocks are messed up it's unlikely. I've driven another C6 with fronts previously used the same way on a Mustang rear and it's fine (except for the bushing falling out because of how it's twisted).

Now... this is where I'm going to honest, maybe brutally so. And when I say this understand it's not meant personally. Most of my best friends are engineers. Hell my girlfriend is an M.E. who's developed and patented medial devices. The trouble with engineers is that sometimes they live in a world of too much data, not enough real world "what's happening". I am exactly the opposite, so I tend to balance engineers who are level headed and just dont' think I'm wrong, pretty well. Previously on another STU Vette I told the owner I thought he was going way too stiff on springs. I got some "I tested it, I thought about" etc. kind of answers and when push came to shove, it ended up too stiff. It's now a lot more like what I originally felt was the way to go. But I had no DATA to back that up so down that road he went. That's ok, I'm glad he was smart enough to backtrack. Sometimes smart folks like to be different for the sake of different too and that can get them in trouble. I cannot run a non-adjustable shock, and I won't. Some run on the theory that for X weight and wheel rate, etc that you can nail the perfect damping. I don't agree with that, at all. See also how I tweak my shock just for different tires. I made shock changes in Wilmington for the Pro as the car was quite a bit different than it was the week before at the Tour even.

Here's what I'd suggest. Call me. Let's talk about this before you go throwing the baby out with the bathwater chasing setup changes on different sites and using an opinion about one to make decisions. Opinions matter, but the aren't absolutes and the thing with Lincoln is that it tends to makes whatever behavior your car has, worse. If it's tight it tends to get tighter. If it's kind of free, it tends to get more loose. At least in my experience in 6 different cars I've run there since 2009.

jesup16

Trying to follow all of this and I notice it seems there's a lot of terms thrown around for tuning the shocks e.g. stiffening, higher, tightening, etc.

It's my understanding that "tightening" a shocks adjustment makes the shock react more "slowly" because you are limiting (usually via an internal needle) the flow of gas.

In old RC car tuning days, when we did stiffer springs, we would do thicker oil/smaller pistons in the shock... effectively slowing the shock down to control the increased spring rate.

Stiffening/tightening a shocks adjustment would not be increasing rebound (single adjustment), it would be decreasing (slowing down) rebound?

Ramo7769

Increasing rebound as in rebound damping or making the shocks stiffer in rebound is how I've referred to it, which yes slows down rebound motion.

jesup16

FYI, I went to the soft setting on Sam's front bar this weekend and it felt really good... wish I would have done it a while ago, but I try to only tune 1 thing at a time. Better transient response and great med/high speed turn in. I did notice a little more low-speed understeer, but I thought that would be an expected side effect.

Ramo7769

I experienced Sam's quote play out in real life when my front rebound damping was set too high. The front was "writing a check the rear couldn't cash" in a slalom. 2-3 inputs had the rear end stepping out. Backing that down improved slalom performance.

Ramo7769

Very late 2016 Nationals Recap
I fell short of my goal of a trophy this year on my 2nd visit. But, I learned a lot. The setup summed up on the OP at nationals this year resulted in just a slight steady state push. It was pretty good. On the Nationals test course, I made a mistake of increasing rear rebound based on tighter corners. So, in competition I found myself pedaling transitional elements too much. And in general, I was too filled with anxiety to put a run in that reflected my best driving.

So, overall, I learned some important aspects of setup that will guide further research this winter. My setup next year will be better. And I learned that I generally wasn't quite as "on my game" for competition at bigger events this year and some of that boils down to not having a fast co-driver keeping me on my toes at local events. I plan to attack the 2017 season with an improved car along with setup lessons learned and applied. I have also picked up a co-driver who has some nationals trophies under his belt which should bring setup and driving help along with good competition throughout the season.

Not my best work, but here is my run on the West course anyway:

Also, for grins at a local event at the Toledo Express airport, I said F it and put the big bars on (Strano 35 full stiff and Hotchkis rear full soft) and picked up our local alien for a co-drive. It was fun. His raw time beat some decent SSR folks which is cool to see and motivational for next year.

jesup16

Andrew,

Great stuff at Nationals... don't get discouraged. I meant to find you at nationals... but it seemed you were always about to run. Sorry I didn't get a chance to meet you. This was my first nationals and I co-drove a car in G-street (very different than C5 STU).

The West Course at nationals was "interesting"... I didn't like it and it proved very challenging for all sorts of skill sets. Also, G-Street was the first group on this course, so there wasn't even rubber to follow... it was a virgin course. How did you do on the East (airport) course in comparison?

Ramo7769

I finally started the 2017 season with some big changes.

Engine: I found some power that I'm allowed in ST and probably should have done so sooner. I managed to find some 1 3/4" primary long tube headers for sale second hand for $150. Danny Popp identified them as "Melrose" headers. I don't think they're in production anymore and they were a bit rusty. But, Danny said he tested 12 different sets years ago on a C5 Z06 and these were in the top 3. This along with some high flow cats with the minimum cell density allowed in ST, an X-pipe, and the already installed C5 Z06 titanium axle-back exhaust completed my full exhaust system for several hundred dollars and some fab work on my co-driver's part.

I also added a Blackwing/SLP intake for good measure. These hardware changes warranted calibration. A friend of mine who does engine calibration for GM was nice enough to do a street tune with HP Tuners for the price of a burger and beer and a $99 license. Fwiw, we found gains of up to 11% on the VE table. And larger airflow gains were found on the low end than the higher end which is good news for this tall geared autocross car.

Differential: I also swapped out the stock differential for the OS Giken differential which is arguably the least budget friendly part of my STU build now, but I can't say I have any regrets. I took the tune Lugod came up with in his STU build. He has good details in his thread on this forum.

I always struggled with low speed understeer with the car. Part of this can be attributed to textbook vehicle dynamics concepts and instability being greater with greater speed. Another part however can be attributed to the stock limited slip differential which seems to have a lot of pre-load built in. Hence the tire chatter at light load around tight corners such as when turning in an intersection.

The diff freed up the car so much due to the negative clutch pre-load that starting with a fairly tried and true spring and bar setup from last year had the car feeling very loose. Now with the Stranoparts adjustable rear swaybar set at full soft and the Stranoparts 1 3/8" bar set "soft" up front, the balance is good. (To be honest, I can't feel the balance change with different settings on the front bar. The rear bar balance changes are profound, however).

The diff also puts down power spectacularly. I think the car is in a good place to have better balance throughout different elements in an autocross course and be a strong contender with some more setup tweaks.

Ramo7769

Sorry I missed this as I haven't looked at this thread for a while. I didn't do great on the east course either. If anything I did better on the west course. I screwed up my damper settings a bit on the test course and gave myself some transient oversteer. I learned some lessons from that at least.

Ramo7769

I ran 2 days on the Toledo concrete and ended up needing to change the balance as it was all over the place on day 1. I went to a tiny base rear bar (17mm) and that made it very driveable. Video from day 2.

I'm still loose on the brakes. I am going to try DS2500s on the front and see if that helps out while keeping the HPS 5.0 on the rear with the option of stepping down to HPS.

Ramo7769

At a test and tune on concrete in Oscoda, my co-driver and I compared the 285/30-18 Bridgestone RE-71R with the 275/35-18 BFG Rival S. I'll spoil the surprise and tell you up front that we don't have a very conclusive result that says which is faster from our A-B-A test. Surprise surprise.

Some background on the tires is that the Bridgestones were tires I put close to 150 runs. (I assure you that this is a faster state than shaved, new Bridgestones with 1-2 heat cycles and ~8 runs.) BFGs were new this year and had about 30 runs.

What I can tell you is a lot of subjective input. Have you ever had a car that you switch between snow tires and summer tires? To me it felt exactly like that (going from snow tires to summer tires) when switching from the BFG to the shorter, stiffer Bridgestone.

Time results
A: BFG best of 4 runs:
Andrew - 29.1
Kenneth - 29.0

B: Bridgestone best of 2 runs:
Andrew - 28.7
Kenneth - 28.2

A: BFG had 1 more run before it rained...
Andrew 28.3

Transitional behavior
For what it's worth, I set my shock settings on the BFGs. Being the mushier tire however, they have a much longer transient period before taking a set. This was very noticeable in the slalom portion of the T&T course. Trying to drive the Bridgestone pace with BFGs had the car getting out of shape.

Sweeper behavior

I felt that on the brakes, the Bridgestone could mix lat and long more effectively, giving more trail braking potential before the car goes into oversteer behavior. This may have something to do with force normal vs. lateral grip curbes.

Aside from that, the BFG is easier for me to drive at the limit, holding a desirable slip angle and not getting too out of shape and scrubbing speed. It feels as if the window of slip angle around the peak of lateral grip is larger than the Bridgestone. But, also that lateral grip does not diminish as much once this optimal slip angle is exceeded.

* I will continue later and add some DL1 data collected

Ramo7769

For this event, my co-driver and I ran some old Bridgestones rather than running stickers that had no heat cycles yet. Some used tires on the rear for day 1 proved to be an issue. They were lacking in grip and they were moved to the front for stability on day 2. Overall, with all 4 tires on the wear bars, the car felt a bit knife-edgey at the limit. Below is my best run that won the class of 20.