Ramo7769

I may as well stop cluttering everyone else's build threads with my stuff and put it in one place, even if it is far less impressive than Borg's and Lugod's.

Background on myself: I'm a mechanical engineer working in chassis controls. My main competitive driving experience aside from Gran Turismo and terrorizing local karting joints consists mainly of local solo events with a HS Volkswagen Jetta in college followed by 24 Hours of Lemons racing with a 1992 Chevy S10. Here's an article on our Class C win. I also had the fast lap for the class. 1:45.6 for Gingerman Short is only fast if you consider that we had 120hp. http://gmauthority.com/blog/2014/04/...emons-detroit/

I bought a C5 to advance beyond "wow, that guy in the Jetta is actually kinda quick" and to have a car to steer more with my feet. I'm currently leaving a lot of STU allowed modifications on the table. I'm mainly running ST so I can learn more about setup and will be building it more hardcore for STU over time.

I'm also looking to use up my autocross tires at the end of the season at a couple track days with the nice 3 ***** Racing folks you might know if you're familiar with Michigan car culture.

2015 Build:

Seat: Sparco Evo II, Brey and Krause harness bar with 5-point

Brakes: Stock with Hawk HPS pads

Engine: Z06 titanium catback

Wheels, Tires: 4x Z06 rear wheels, 275/35-18 Bridgestone RE-71R

Chassis:
Vette Brakes and Products springs.
1200 lb/in front, 800 lb/in rear
Strano Parts 33mm front swaybar (Currently set to full soft, we'll see if the test and tune this Friday has me leave it there)
Stock Z51 rear bar
DRM-Revalved Bilsteins

Ride Height

I corner balanced my car in April, 2015. I chose to start at a ride height where all of my lower control arms were roughly horizontal. then add ride height where needed to get equal cross weights. This landed me (with 275/35-18s and no driver weight) at 4.75" front, 5" rear at the jacking locations. To my knowledge, my car is sitting just slightly lower than stock.

Alignment
I currently only have a set of strings with no camber/caster gauge so what I've done is simply maxed the camber front and rear and aligned the toe to zero. For solo events, I run 3 flats of toe out per side on the front and 2 flats toe in per side on the rear. I zero the front toe for track days.

Lessons Learned: It's impractical to setup a car to be skidpad neutral and expect to go fast at a solo event. I spent some time at some tight, 1st gear, local events last year and it didn't help my setup at all. At my worst point, I had a T1 rear bar, stock front bar. It wasn't that bad for local events with all the relatively poor low speed steering performance of the C5 and part of the low speed push due to basic physics. I had my best PAX result at a local event with this setup even beating John Heinricy.

After then being filled with false confidence, I brought the car to the Toledo Express Airport and was beaten by a fast local guy who runs a stock C5 in BS. Ego busted. Then I started at national events. I have 2 under my belt now and my ego is in the toilet. But, now I've got some work cut out for me in terms of vehicle setup and as a driver.

Future Plans and Goals: Without spending more money this year, my goal is to take a trophy home from a national event for the first time ever. Events where I'm shooting for this goal will be Toledo Match and the Wilmington Champ events.

I'm always open to suggestion and always appreciate advice. So, any input is appreciated. Thanks for reading.

6/21/2016 Updates

I hit my goal of a national event trophy last year at the Wilmington Champ Tour after losing a day 1 lead to Martin Kriz and taking 2nd/12 for the event. A great accomplishment for myself which I'm planning to build on this season.

Current Setup:

• Melrose 1 3/4" long tube headers
• Blackwing/SLP intake
• OS Giken diff with STU tune
• Borg Motorsports Delrin AF Offset Bushings
• VB&P 1200 lb/in front spring
• Hyperco HPT rear spring
• Strano 1-3/8" front bar
• Strano rear sway bar set full soft
• StranoParts sourced Koni Sport single adjustable dampers
• 8x Z06 rear wheels, 18x10.5
• Bridgestone Potenza RE-71R 285/30-18, BFG Rival S 275/35-18, planning to test both
• 8mm front wheel spacers
• Hawk HPS front brake pad
• Hawk HPS 5.0 rear pads
• Alignment :
  Front Camber- -3.5 deg; Front Caster- ~6.5 deg; Rear Camber- -3.2 deg
  Toe: Front- -1mm (out)
  Rear- +4mm (in)

ltborg

Nice details on the car. DRM makes nice Bilsteins.

All these STU build threads give me a lot of hope for the class. The more people we get on board the better the competition will be.

Ramo7769

Thanks! I'll also add ride height in there. This seems to be a quickly growing class. With the talk about adding more cars to STU, I wouldn't be surprised if it has near STX level of attendance soon enough.

I'm headed to an air strip in northern Michigan this weekend for Friday T&T, Saturday Pro Solo format, and a 4 run solo on Sunday. I'll have the opportunity to swap drives in the test and tune with a couple of fast guys who run a BS C5 that they'll be taking to nationals this year. That should be a good learning experience.

Ramo7769

I'm having a little issue with the Strano bar install up front I was hoping someone might be able to comment on. I have adjustable endlinks I used on the Z06 bar I had on the car previously. It was very straight forward to set the pre-load to zero before. I'd shorten the endlinks both fully for maximum thread engagement. Then put the car on the ground and lengthen one endlink until it became very easy to spin because it was unloaded.

The issue I'm running into is that with this install, I needed to lengthen one endlink considerably, almost to the point of worrying about thread engagement to get the pre-load out. The only thing I think one would be capable of doing wrong is having the bar mounted slightly off to one side, left or right. I'm going to double check that this week since I may change settings at the test and tune. I'd like to avoid breaking one of my endlinks.

klodkrawler05

Subscribed for more street tire setup info and because you're somewhat local! I run my similarly modified c5z on the same tire/wheel setup at all the local furrin group auto-x's but havent made it over to a DSCCA event this year.

With regards to the swaybar, I haven't gotten around to installing my adjustable endlinks on the strano bars yet but if you aren't able to dial out all the pre-load with one end link I believe the correct method is to install said endlink as close as you can then switch to the other side and adjust it taller to make up for the difference? that's what I had to do on my miata (obviously a different car)

Xian

Are your front corner/ride heights roughly equal? Maybe one corner is enough higher that it's causing issues? Also, did you take apart your adjustable endlinks and confirm that they're the same length for both sides?

strano@stranoparts.com

so.... lengthen both links to a middle position to start. Then shorten one and lengthen the other to get where you need to be?

69autoXr

Is it the left side that you've had to lengthen? Do you have your weight in the driver's seat?

I had the same problem at first because I had forgotten to put my weight in the car. Once that was done, the left side shortened up considerably.

Ramo7769

Thanks for the input, all. To clarify, one link is as short as it goes and one is as about as long as I feel comfortable with running (or more since this post exists). It is the left side that is long. When I was struggling with it, I had my buddy sit in the driver's seat (very similar weight) which made a very slight difference, but did help. And of course this is the preferred way to adjust pre-load anyway if you know anyone capable of being dead weight.

And to answer your question Xian, I do have unequal ride heights up front with the right side sitting higher. This would make me expect to need a longer link on the right side, but I'm seeing just the opposite.

Anyway, I'll mess with it tonight and see if I can find anything. Again the only thing I can think of is the bar being mounted off center. I'm thinking I'll jack the car up and take some measurements of how it's mounted. Then if need be, loosen the mountings, disconnect an endlink, slide the bar over, and re-torque.

jesup16

Subscribing for another informative STU build. I'm glad we have so many capable people sharing their information. It may inspire me to start my own build thread.

Ramo7769

On the swaybar install, It seems that it was mounted off to one side. I loosened up the mounts and slid it over last night. That seemed to help. I still didn't do a great job on centering it because I still needed some added length on the one side. But, I took apart the end link to double check the length to see how much thread engagement I had. I feel I was in the clear anyway with more than the thread diameter in thread engagement.

I'll be doing a test and tune Friday in Oscoda, MI and I have more piece of mind at this point if I want to mess with stiffer adjustments on the front swaybar at this event. There are some good benchmarks at this event with some fast nationally competitive guys in a BS C5 running the same tires as me. Allen Chen and Ken Tsang. If I can simply raw time them, I'll be in good shape in terms of progress with my underdeveloped STU car. Figure my advantages over them are currently wider wheels, spring rates, and seat.

I also added some more on exhaust in my development plan in the OP.

69autoXr

Seems like the bar should be able to slide a bit in it's mounts without loosening it to center it. Did you lube the bushings? Can you rotate the bar by hand when the mounts are tight?

Ramo7769

I greased the bushings on the original install. Haven't done it again when messing with it. I can't move it laterally while it's torqued down to the 43 ft lb spec. I didn't try to rotate it.

Ramo7769

The Oscoda event went well. I didn't make any changes at the test and tune. Kept everything as listed on the OP. I just drove the car and learned to do so a bit better. I was happy yesterday to have a 1 second raw time advantage on 2 people who I consider to be very fast BS C5 guys on a ~50 second course.

I'm a bit alarmed at how much the Bridgestones seemed to have worn in 16 runs this weekend. But they performed great.

Comparing to the BS car during the T&T, mine is still a bit more loose and a lot better in a slalom (wider wheels help). But I like it. One downside I found is that my brake dive feels far less controlled. My spring rate should be roughly double that of the stock spring, so I'm thinking the difference is damping. They have Koni singles, whereas my Bilsteins aren't tuned for higher spring rates.

I'd consider slightly more roll stiffness at another test and tune to see if it allows me to drive harder. The car is quite neutral though as is and I like it.

strano@stranoparts.com

I've been lurking, but think I need to chime in. First, shocks matter, a lot. And Bilstein's aren't going to cut the mustard. The simple fact is that we transition, a lot. And you have a pretty stiff front spring, and my bar both. It's not rolling, or for that matter even diving that much. Trouble is the rate of the roll and dive, hence the issues in slalom and the way the car feels under braking too.

Now you can go absolutely insane with shocks if you want, and many do. Hell my set of MCS Doubles (that I sold last year) are for sale again... I think he is down to $2800 for them now. I sold them because the Koni's were all I needed on my SSR car. But I tested. Bilstein's are lacking if for no other reason than you cannot tune response rate, your only way to do that is with bar and spring, and you can to some extent, but those things also have a steady state component.

The joke tends to be how I like my cars so super soft. Compared to many, I do. And it's worked for me over the years in a number of classes, even those where springs were able to be changed, and on heavier cars.

I think at this point, your money is best spent on some shocks that allow you some ability to tune the car. The Koni's are still on sale (like $300 off), and the Ridetechs are a little bit less (normal price). There are pro's and con's to each, I've run each. I sell both (and others).

MHO, YMMV, all that jazz.

Ramo7769

I thank you for chiming in. Always appreciated. I had shocks on my list, but riding in the nicely tuned BS car, along with your input, pushes them higher up my list. The BS car felt like body motion was more controlled and as I said, gave the sensation of less total brake dive, even though this car likely had more dive, but at a lower rate. In my car, braking too hard at turn in unloads the rear fast and causes oversteer. It would be nice to slow the body motion without slowing my rate of brake apply.

Since I do run a higher front spring rate (And if anything, will increase that rate more than where I'm at now), I would expect to get more benefit (compared to your SSR car) from a double adjustable that will allow a bit more compression damping. Would you agree with that? I'd be fine with Koni singles if they'll work for me. I just don't want to get them just to end up wishing for more compression to play with.

strano@stranoparts.com

No, I'd not agree. Compression is not spring. Compression is a control for unsprung weight. Drives me nuts, (and will you too) when folks try and use it as spring. Rebound is what matters. Trust me if DA's were faster I'd have kept my MCS. If you get in a real bind tuning and have no other option compression might help, but this isnt' some no camber having street class car like a WRX or something either.

MHO.

Ramo7769

What you're saying is what I've always read but I've never had/found a technical explanation as to why/how compression damping controls unsprung mass and rebound controls sprung mass. I just can't wrap my head around it. I would think that both compression damping and rebound damping control the sprung mass in different scenarios depending on the maneuver.

How I intuitively think of it is that during the transient part of a straight line braking maneuver, front suspension is going into jounce at a rate characterized by the compression damping force while the rear suspension goes into droop at a rate characterized by rebound damping force. If you could tell me why that isn't true and why the whole sprung mass is primarily controlled by rebound damping, I'd be very appreciative.

jesup16

Sam knows his stuff. You just might be overthinking it, but the light bulb will go on at some point.

I took the time to read (more like skim) through a Penske shock tuning guide at a friends speed shop one time. After this, I understood what my friend was talking about: it's all (mostly) about the rebound. This guy is an engineer for Alex Job racing (GTD Tudor Cars).

For this reason, I was going to get another set of Koni's from Sam. Then he threw me a curve ball with the Ride-tech's and his custom bump-stops. So far, I really like them. I'm gradually stiffening them, but I can definitely tell there is a difference in the rebound adjustments. But I think you need to move the shocks to the top of the priority list. Koni's or Ride-tech's...you really can't go wrong with either and Sam sells both.

For 99/100 autocrossers, rebound adjustment is where the money is at. There are very few drivers that can control, drive, and feel a car well enough to leverage double adjustable shocks. And even in Sam's case, he didn't feel the value/speed was there to leverage DA's.

Edit: Study some shock dyno's and look at the curves of Compression versus Rebound...you'll notice most of the adjustments in DA's still largely affect the rebound (looking at the slope of the curves in the graph's).

strano@stranoparts.com

This is where theory and reality slam heads. Can you feel a difference adding compression. Yep. But generally it leads to the car skating. Shocks don't limit roll. *BUT* in things like slaloms, you are changing direction so quickly that less roll rate does indeed mean less roll.

Ok, so why do I think in most cases Doubles are overkill? Easy. Look at any picture of a car under load. Most of the roll, 2/3rd of it anyway is on the inside, coming up. Which is controlled by rebound. Rebound forces are much higher than compression forces. If you go nuts on compression will it make the car act more slot car like? It will, but here's the thing, it also messes with how the car loads the tire and how the car and tire deals with bumps.

Even when you have DA's the trick is to use only enough compression until you get the car to skate then stop or even turn it down one or two clicks. And you want to test that before adding any rebound.

Compression often "feels good", and then slows folks down because the car tends to skate. Folks from states with winter get this more than most. Walk on a low grip surface with your knees stiff, so you "load" your shoes with your weight really hard and quickly. You tend to slip and slide and often fall down. You walk with "soft" knees. Your knees in that case act very much like dampers.