Autox ASP spring rate
 

Hi there,

I'm setting my car up for ASP class in LA region solo2 autox. My question is what kind of spring rate are the fast autox FDs running? As of now, I'm looking at JRZ, Penske, DA Konis, and Advance Design. My budget is between $2000-3000. Advance Design offer the best bang for the buck it seems, but i hear there are issues with reliability, does anyone have any input on these?

Thanks,

Randy

If you're buying shocks talk about spring rates with your shock manufacturer. The valving of the shocks are going to in large part determine what range of spring rates to use.

I highly, highly recommend giving Guy Ankeny a call as he could definitely get your car setup with Penskes and his experience supplying Solo2 cars is tremendous. He's done many FD suspensions.

www.guyankenyracing.com

I contacted Guy already, the cheapest Penske he can make is double adjustable which cost $3400, and he wants $800 for aluminum top hats. This is abit out of my price range unfortunately. I've been referred to Guy numerous times, is there any one else besides Guy who has experience with FD in autox? =)

Tripoint Engineering will still build, revalve and convert nearly all types of Koni and you can't go wrong with them either as they have tons of FD experience.

www.tripointengineering.com

http://www.tripointengineering.com/G...i/28series.gif http://www.tripointengineering.com/G.../Koni/8216.jpg http://www.tripointengineering.com/G.../30series2.gif http://www.tripointengineering.com/G.../86series2.gif

Thanks Damon, I will give tripoint a call tomorrow. I'm still open for opinions directly from the owners :) Damon, what kind of setup is on your car?

Randy

Stock springs with Koni yellows revalved by Tripoint and a Tripoint adjustable front sway bar. I'm considering going to something double adjustable like a Penske or Koni 28.

Hi Damon,

I've also heard to get a stiffer front sway bar, what is the reason for this? Is it to control the dynamic camber loss or something else?

Randy

I believe that the cars prepared for ASP and SM2 at the national level are running spring rates that render them unsuitable for any daily driver use. (around 800 lb front 500 lb rear). Unless you are preparing the car as a track and autox only toy you will be best serverd by setting the car up like DamonB describes and running as stiff a spring as you can live with. Tri-point told me some time ago that the Koni Yellow can't be valved to support more than about a 500 lb front spring. If you want a stiffer spring than that you need to go to the custom stuff (Koni 2812's or Penske 8100's) and these will run around $1000 per corner with upper mounts and springs.

Hi Swilson,

Yes the car is not going to be driven around the street, it's going to be an autox only car, will do some fun track days but the car will be setuped for autox only. There is a couple options, penskes, ohlins, revalved konis, jrzs, advance design. I just need to pick a spring rate first :)

Randy

I agree with swilson.

I run my car in stock so I'm stuck with stock springs. Once you jump to ASP or SM2 you can do whatever you like with the spring but I also daily drive my car. People have been telling me to leave the Z06 class (SS) for years since my car is uncompetitive with them. Frankly I see no reason to run an FD in ASP either because the Z06 still would have the clear advantage. It's not until you go to SM2 that the FD begins to have some potential and I am NOT willing to throw that kind of money at the car, especially while I still drive it daily. The way I look at it it would literally cost me at least $10,000 to build a "real" SM2 car that will get me around the course maybe a second or two quicker. That's not worth it to me even if I were more competitive in the class.

If I go any further with shocks I will dump the Koni yellows. There is nothing particularly wrong with them but the only other step I'll take is going double adjustable and if I do that I'm going to go for something monotube with larger pistons. The Koni yellow can be converted to DA but I don't think it makes economic sense (even though it's still cheaper than buying something like a Penske, Moton, Koni 28 or Advanced Design).

The stiff front sway bar does help get rid of some body roll as you would expect but that's not the real purpose in my case. Sway bars change weight transfer across the chassis and what the stiffer front bar really does for me is keep the inside rear tire more firmly planted to the ground. This lets me use more throttle earlier and harder out of the corner. The great thing is the bar is adjustable so I can set the car up for different locations. When I go to the roadcourse I run the bar even stiffer because the radius of the turns are much larger compared to autox and the chassis likes it. If grip is low I can always soften the bar up too. I'll never live without an adjustable front bar on any future "race" car. I use it too often.

Keep in mind that stiffer springs already reduce body roll. A car with very stiff springs will not require as much bar (check out how tiny the bars on most formula type cars are!) as one with softer springs.

I would first decide on a shock (more important than price is support for it) and then speak with them about spring rate. Tripoint has lots of options and lots of FD experience. Tell them what you want to do and are willing to live with and let them decide for you. They know what they're doing.

Springs & racing
 

Just to help out. I run in SM2 with my 7 and can tell you what Andy and I run.

Andy runs 800 lbs in front 600 in the rear, ankeny shocks, no rear swaybar.

I run 550 lbs front 375 rear, Koni Double adjustable by Tri-Point, with rear bar.

Andy is going stiffer next year, as well as I.

If you are going into ASP or SM2 go with Andy's set up (he is very fast as seen by his placement at nationals) or softer like 600 front 450 rear, as that is what I am going to.

Get the double adjustable shocks from Tri-Point or Guy. I have the cheaper shocks and have not stepped up to the plate yet for the $3,500 to $4,000 deal.

Ensure you have adjustable swaybars both front and rear.

Tires the set up is 285/30/18 front and 315/40/17 in back, possibly 315/30/18 in back.

Hope that helps.

I would love to see more guys come out to play.

Allan

SM2

Thanks Spank for the info, the f/r spring rate ratio is pretty consistent with other spring rates I've found, approx. 1.3-1.4. I've been told this would give a close to 50/50 wheel rate in the FD.

Another question Spank, what kind of alignment setting are you and Andy running?

Thanks,

Randy

Alignment
 

Depending upon your likes and experience.

Front Negative Camber up to 2.5 get it all if you can, rear is the same. The camber hurts some on acceleration but helps on the turns.

Toe Front 0 to 1/4 out total. Rear depending upon experience 1/2 total to in to 0 depending upon your experience and taste. Suggestion is when you first start start with 1/2 total toe in. If your car pushes too much or you have some experience then do 1/4 total to in. Depending upon the rake you have in the car will depend upon weather you can go to 0 toe in the back.

Hope that helps.

Allan

Another question Spank, what kind of ride height are you guys running? Is it a good idea to run the ride height as low as possible? Do you guys run any sort of rakes to tune handling? or just go by corner balance.

Thanks,

Randy

Given the choice you always want ride height to be as low as possible without bottoming the suspension (or putting the tires through the tops of the fenders ;) )

A lower ride height makes the center of gravity of the car lower. The lower the center of gravity the less weight transfer across the chassis. The less weight transfer across the chassis the more work you can make the inside tires do under cornering. The more work you can make the inside tires do the faster you can corner :bigthumb:

It does you no good however to lower the ride height if you don't have the suspension travel. Low ride height doesn't help if the car is heaving off the bumpstops in every corner because striking the bump stop instantly rockets the wheel rate way up which makes the tire break loose. Some people are known to "soften" the stock bumpstops somehow so that the car in effect has more suspension travel in bump...

Listen to this answer!
 

General rule start with 1/2 inch rake and go from there. Depending upon push or oversteer will be an indicator. If you can get the camber to neg 2.5 all the way then 1/2 is fine.

Allan

1/2 inch positive rake (front lower, rear higher)? Any of ya measured the wheel center to fender distance? or ground to fender. I know it depends on the shock travel and spring length etc. just curious on what you guys are running.

I've never done a corner balance before, I'm assuming that if you adjust the ride height rake to your preference, and if the car doesn't have perfect corner balance, you wont' be able to corner balance your car to even weight distribution?

thanks,

Randy

Rake won't hurt that. Corner balance is really adjusting cross weights.

Rake
 

The front should be lower than the rear. You may find that when you get to a certain point your front, rear balance will be pretty close just by adjusting rake. Mazda did a pretty good job in balancing our car in the first place.

Also remember 1/4 inch rake Front lower than the rear is fine. If you need more bite in the front and the other normal alignment and shock techniques do not work then you can go to more rake to get the bite.

Hope to see more RX7's in SM2 next year. My goal is to be lighter and faster by next season.

Good luck.

Allan

Rake adjusts the height of the instant center at each end of the car. The instant center is the point in space about which the wheel at the end of the suspension arms pivots. This point moves constantly when the suspension is in motion but chassis rake can be used to adjust the relative heights of the front and rear instant centers to eachother.

If you could adjust the geometry of the suspension arms then you could change the height of the instant centers without having to change static ride height at either end.

Thanks for the info, everyone feel free to chime in, new information is always great =)

Damon, I think you need to adust the suspension arm mounting points to adjust the instaneous center.

No, ride height changes it too because the instant center moves as the suspension arms move. Since lowering/raising the car via the springs also moves the suspension arms the height of the instant center changes merely by adjusting ride height. This is true of any car with unequal length or non-parallel suspension arms. If the instant center and roll center didn't vary with ride height changes there would be little reason to run rake in the car...

The height of the instant center above the road changes as the suspension arms move. Whether they move because of where you set your static ride height or because of a bump in the road doesn't matter.

http://rodandcustommagazine.com/tech...1_ifs_01_z.jpg

The instant center is the point where a line extended from the upper and lower a-arms would intersect. Since the a-arms are of unequal length this point changes in spacial position as they move. The roll center is the point where lines extended from each instant center to the center of their tire's respective contact patch intersect. Roll center is the point in space the chassis roll around as it leans in cornering. Instant center is the point the wheel pivots around during suspension travel. Making a change to the instant center automatically makes a change in roll center.

Yep that's what I meant, without changing the rideheight to adjust rake, you would have to move the suspension mounting points.

Hello , I'm bringing this necro thread back from the dead. LOL

I've got My FD I am in ASP . BUT running Summer street tires . WOrking on the driver vs really getting the best times .


I have GAB 8 shocks .

stock sways.

and running 650 / 500 spring rates .

I also have springs which are 800 / 750 I believe I need to check them to make sure . But

I'd like a bit of advice about the ratios .

I've got a good friend who races in spec miata , and has a turbo miata in SSM and runs spec miata suspension which is 700 front , and 350 rears .

my car rotates quite well ... or well I should say its more on the loose side .

Now he told me my rates are to close , But I should get some opinions from some more experienced FD racers as to the front to back ratio before I swap springs .

so if anyone would be able to throw some advice my way i'd appreciate it greatly .

first was my worse lap with the car getting unsettled , this was driver error ,

and the second one was my best lap .

I would like to know if the issue is the spring rates or the driver LOL .

I vote driver..