PUR NRG

Getting an alignment done tomorrow with an eye towards making it perform better in autocrosses. I'm handicapped by the fact that a) I'll be using the stock 18" tires (I'd rather be on S03's) and b) everything else is stock as well (shocks and front sway bar).

Even so, does anyone have recommendations for alignment settings? Specific numbers would be even better. My current thought is no toe and increased camber (if possible) in front, 1/8" toe out and another degree of camber (if possible) in the rear.
________
PRISON BREAK DICUSSION

tpryor

I have been pondering this for days, and "playing" on my normal spots to get a feel for the car and what it does in the same situations as my Miata(s) in those same spots.

First, I totally disagree with the toe out in the rear. This will make the car more prone to lift throttle oversteer and is exactly the opposite of what you want. Also, having looked under the car for quite a while, I have noticed there seems to be a fair amount of camber adjustment available front and rear, but I don't know how far that translates to in degrees.

I noticed the car comes from the factory with "some" negative camber (a small amount, but noticeable) in the rear, and NONE in the front (maybe even a little positive). I think this is mostly responsible for the "push" that has been widely reported.

Also, with the wide 18" wheels, you want to be careful of the amount of negative camber you run (if you are going to run the same settings on the street), as this will DRASTICALLY affect tire life around town. It will also make the car very "darty" while driving around town every day.

I am going to try to "mark" the standard settings (with a small amount of white paint) and mark the autocross settings (blue paint) and try to change back and forth between the camber settings (I will not mess with changing the toe and caster). This is not the ideal solution, but I don't want to buy street tires as often as I have to buy Hoosiers!!

So, having said all of that, I think the standard place to start would be:

-1 to -1.5 degrees camber front and rear. I think the car will prove to be fairly neutral, so I would start the same at both ends. This will give you a feel for what the car is really doing, and small adjustments can be made later. It will also give you a feel for whether the car needs a sway bar, shocks, etc.

1/8" TOTAL toe out (Front) - this is optional and will only help if you can repeat 10/10ths runs every time.

1/8" TOTAL toe in (Rear) - this will allow mid corner corrections without all of the hysterics. More may be necessary, but this would be the limit for street wear vs. track "feel". Trailbrakers live and die by this setting (at least in Mazdas).

Caster is a subject no one agrees on. Some like to have all it will take (even at the expense of camber), and others prefer all that remains AFTER getting the desired camber settings. I personally fall into the second group, but you can decide. The only real benefit is a tendency to self center the wheels at speed and a small amount of camber "gain" in the corners.

Sorry for the rambling, but I wanted to make my case and see who does and doesn't agree with me. I received my Hoosiers yesterday, and I have a second set of wheels, so I am as anxious as you for feedback.

I hope this was at least a little helpful.

By the way, If the DSC is on, throw ALL of the above advice out the window - I would have NO idea.............

PUR NRG

tpryor, thanks for the input. This kind of discussion is exactly what I was hoping for.

I ran my first autocross in the RX8 last weekend and regardless of the factors (stock tires, alignment, suspension, dirty course) I experienced the opposite of what others reported. No push, but a definite tendancy for oversteer both going into a decreasing radius turn as well as when throttling out of a turn. I'll post a more detailed autocross report after the times are published.

I don't care about tire longetivity that much. If anything it will hasten the day the stock tires go and I can put S03's on instead. For reference I replace S03's every six to nine months on my daily driver (the RX8 is my wife's) so I don't mind the reduced tire life. I consider it a worthwhile price to pay for better performance.

I intend to run in B-Stock Street Tire so it will be one alignment setting for both autocross and street. I also fall into the max caster but not at camber's expense camp and did that on my S2000. After alignment I'll report back with what settings they were able to come up with.
________
Free **** vid

tpryor

This is EXACTLY what the toe in in the rear will help with!

Please DO report back on what setting they were able to obtain.

eccles

Tim,

We're on almost exactly the same wavelength! I was thinking of zeroing the front toe, 1/8" in at the rear, and about a degree of neg at both ends, as a starting point. I'll wait and see what the standard caster is before making a decision there - might crank another .5 degree on for good measure.

I plan on getting this done between the next Spokes event on 8/24 and the A&M practice on 8/31, so I'll be able to compare between the two on the Bridgestones and have it a little more agressive than stock before we bolt on the Hoosiers.

PUR NRG

Some interesting data from the alignment.

Before . . . . . .. . . . . . After
LF Camber: 0.0 . . . 1.0
.. Caster: 6.9 . . . 4.9
.. Toe out 0.11" . . Toe out 0.04"
RF Camber: 0.3 . . . 1.0
.. Caster: 6.5 . . . 5.6
.. Toe in 0.13" . .. Toe out 0.04"
LR Camber: 0.9 . . . 1.5
.. Toe in 0.08" . .. Toe in 0.07"
RR Camber: 1.3 . . . 1.5
.. Toe in 0.02" . .. Toe in 0.07"


At a 10 degree turn-in there's 0 degrees camber on the inside wheel and -1.7 degrees on the outside. We'll see how the car handles at the next autocross, but if nothing else this shows how variable the factory alignment can be. According to the alignment shop (Custom Alignment in Mountain View) the RX8's suspension is very similar to the S2000's. Yet another similarity between them.
________
How to roll a blunt

Sparky

FYI

See my post at the bottom, note this is still work in progress:

http://www.rx8forum.com/showthread.p...threadid=11053

Ophitioxaemia

hi guys,

i just bought an rx8 last night, but i also autocross an extremely fast car with a suspension with extreme adjustability, as well as teaching autox for the last 4 years.

the best way to tune camber is with tire temps. you want the inside of the tire to be a bit hotter than the outside- basically you cant get this on a stock car on r compound tires. it is a bit easier on street tires because they grip less and so there is less body roll.

rear toe out is a traditional no-no with RWD cars. however, for autox it has been used with mildly power RWD cars, such as the NA late model MR2.

with a stock car on dot race tires (not street tires), it is a battle to control roll enough to use the tires effectively. bigger bars will help, although only the front bar is free in stock, as well as more static camber. get beyond (very roughly) 3 degrees static camber and braking can suffer.

the rx8 is a huge weight disadvantange to the S2000 in B stock.

a little toe out in the front preloads the tire sidewalls so the car reacts faster at initial turn-in. personally, i dont notice much effect from front toe- stock cars need to be man handled a bit to counteract the designed-in understeer.

i will report more once my break-in period is over (currently at 85 miles) :D

james
thevenom.net

Sparky

Not as bad as you might think.

The S2ks are running around 2635 in fighting trim.

Haven't weighed my Sport model yet but Mazdatrix weighed his at 2908lbs fully stock, so with wheel and exhaust mods I'm figuring right around 2850, ready to run. My SSR comps and Kumhos are 8.5 lbs lighter PER CORNER than stock. Hopefully the preresonator is enough so that we can completely dump the exhaust aft of it and just run with a pipe.

In comparison a 350z is around 3050 in Solo II config.

Tire temps are important in tunning but frequently are not the final answer in stock because of camber limitations and balance. I'm going to have to back off on rear camber from what is optimal to balance with the front which is camber limited.

Ophitoxaemia

if you are camber limited in the front, then you can do the front bar in stock class and keep more rear camber.

2900lbs? oh thats great news, i thought they were more like 3100lbs!

>My SSR comps and Kumhos are 8.5 lbs lighter PER CORNER

even BETTER news!

any idea of the power increase without the stock exhaust yet?

james

Sparky

Yes that's possible, but would require a smaller bar than stock up front. Remember the stiffer the bar the more the weight transfer occurs on that axle reducing grip in relation to the other axle. So to keep optimal rear camber (best grip), you would need a smaller bar up front.

The issue on a stock class car is that you are already undersprung to start with. Spring rate in conjunction with shock damping along with vehicle mass determines the frequency response and what's called crossover frequency or the maximum rate at which you can apply steering inputs without the car doing the opposite (aka '70s vette syndrome). Since springs are fixed in stock class the only viable mechanisms for increasing crossover frequency are the front swaybar and the shocks. Hence the trend in stock classes to run large front sway bars which increase the responsiveness of the car but lead to a car that pushes heavily on a skid pad.

Increasing shock damping (going overdamped) also works but the most low dollar shocks will get so stiff as to be ineffective on anything but perfectly smooth tarmac (certainly not Topeka concrete) when turned up to the point that they can effectively control low speed body rate below crossover frequency. That's why so many people are purchasing custom shocks with large piston areas and good low speed damping without the highspeed damping penalty.

So anyway that's the trade space that we operate in.

Currently there are two approaches to tuning that I know of.

1) Put a big front bar on to go for maximum response rate in the slaloms and then try to keep the car from pushing too much in the sweepers by running small amounts of rear toe and reduced rear camber.

2) Go for static handling balance with swaybar/camber settings and then tune for slalom performance using rear toe and shock settings. This method requires expensive shocks and good driving skills or the car will swap ends. Not recommended for the average regional autox type enthusiast.

Right now I'm going for method two but in a build up approach. The car already pushes heavily so putting a bigger front bar on seems like the wrong thing to do. Too make things worse, Mazda intentionally raised the rear roll center of the car in relation to the front (vs. the RX-7) to make it turn in more positively but this kills frequency response when trying to go the other way (i.e. the car has visious oversteer if you try to steer faster than it wants to). If we could lower the rear a little things would be alot easier, but we can't in stock class so what does that leave us?

My approach is to keep the front stock bar and overdamp the rear in low speed rebound so it will take a set while using lots of rear toe to preload the outside tire. Front roll rate is controlled by high low speed compression and just enough (more) rebound to keep it stable. This will tend to keep the car acting as a single response curve rather than rear chasing the front as occurs stock in the slaloms.

Understand this is still a work in progress and I'm sure we'll all learn alot before this is over, but the best way for the RX-8 to come up to speed quickly is if we share our progress and ideas.

Comments, constructive critism welcome.

We're not competing with each other. The S2k is the enemy!

If curb weight and acceleration figures were the only things that mattered in solo2, the miata would never have won a trophy.

Ophitoxaemia

>Yes that's possible, but would require a smaller bar than stock
>up front. Remember the stiffer the bar the more the weight
>transfer occurs on that axle reducing grip in relation to the other
>axle.

this is what you will read in books, but it does not always hold true for stock class cars that are so severly camber limited that they dont even come close to keeping the contact patch flat enough. so in a car with static understeer, increasing the front bar can *decrease* push. this was true, for example, with my 1984 rx7.

there is a lot you can do in technique to make a car under or oversteer in autocross. my students are always amazed at how their car, which they thought under or oversteered is neutral when i drive it. i prefer some static understeer so you can be maximally aggressive.

we have andy mckee in my region, multi time national champ in his S2000, and i have had the good fortune to ride with him on several occasions over the last 5 or 6 years in various different cars. the S2000 is an awesome car. even in my fast car it took a few years to turn faster times than him in that nee AS now BS car.

anyway, its great to find a serious autocrosser working on the rx8. i will try mine out at the next event just for kicks since my fast car is still apart. i am prepared to battle push with heavy trail braking and an eager right foot.

incidently, on my normal autox car, one of my winter projects is to lower the front roll center. why this helps i dont have a good intuitive feel for, but it has shown good benefits on other cars like mine. (also i am reducing the SIA).

james

Sparky

Good luck, great to hear the feedback.

You'll find stock that it pushes in sweepers and gets VERY loose in the slaloms.

Dennis

Sparky

Oh, forgot to add.

Recommend starting 38psi front, 35 psi rear on the stock tires. Then go to 34 or 36 on the rear as required for track condition/driving style.

The progressive sping rates allow for a lot of body roll before they start working so you've got to lead the car (turn in early) and of course as with any car on stock shocks, smoothness is everything.

Pulsr

man, i was all excited when i got my rx-8 cause i was going to take it autox. now it just looks really complicated all these classes, tire pressure camber, man. I just wanted to drive up with my rx-8 and go autox bahhh

PUR NRG

Don't sweat the details. Get a competent alignment done with any of the settings posted here, remember to inflate your tires to 35 PSI before you run (and back again afterwards!), and go out and have fun.

The first year or two your times will improve most because you're learning as a driver rather than anything you can do to your car. Don't worry about competing with others and concentrate on competing against yourself. Oh, and avoid racing tires. They will give faster times but they hide driving mistakes that are more apparent on street tires.
________
Lovely Wendie99

Pulsr

man, i dont even wanna do that. i jsut wanna drag it out to autox not change the alignment and just go out at it =(

Ophitoxaemia

just go drive!

thats what im going to do this weekend. it gives you a baseline in any case, and some practice how the car is in normal driving.

TURN OFF THE DSC and TC though!!!

once you start tuning, madness ensues, such as i am swapping my gears and a torsen into an aluminum diff carrier on my autox car, saves 15lbs! :-P

james

Pulsr

hmm, why would i wanna turn off the dcs and tc? isnt that stuff supposed to help or wait.. lemme guess its going to develop bad habbits? :P

Ophitoxaemia

thats stuff is POISON for going fast. it is designed to keep the car in control, not to let it go fast, so it applies the brakes and slows the car when you are trying carry speed to the apex, doesnt allow any slip angle where the tires generate more grip, doesnt let you rotate the car with trailbraking, and the TC kills the little bit of wheelspin you need to start a four wheel drift on exit.

i almost didnt get the leather seats because of the DSC that comes with it.

the biggest hurdle for people to go from intermediate to advanced driving is learning to get comfortable with the car on the slip angle. as a beginner you should concentrate on the basics- where to go slow and where to go fast, but if you learn with the computer second guessing you, you will not learn to feel what the car is really trying to do.

just going to drive is the MOST important thing tho, and having fun!

james

PUR NRG

You need to get all four wheels aligned regardless of what kind of driving you do. One week after picking my car up I got an alignment done and found the rear camber differed by 0.5 degrees from side to side. Given a desired camber setting of -1.5 degrees that's really horrible slop.

Likewise with inflating the tires before an autocross. If you don't, you'll roll the outside edge of the front tires and they'll wear down to nothing real quick. Inflating the tires gives you better traction and longer tire life.
________
Ticketmaster gift cards

Ophitoxaemia

some careful flogging on the street reveals some odd and non-linear reactions in the car.. someone, maybe robin, said the car may push in sweepers and get loose in slaloms, which i can definitely see. perhaps this is the progressive rate springs. boy this car rides so smooth compared to my probe GT!

personally, i like some lift throttle oversteer- lets you tighten up the line and increase the slip angle to reduce understeer once you get back on the gas.

james

Sparky

If you like some, you'll love this car.:D

I'm convinced the progressive rate springs are the culprit here.

Ophitoxaemia

>I'm convinced the progressive rate springs are the culprit here.

when i am trying to get the car to take a set out of a corner, i get this distinct bouncing feeling.. which is awful because as it bounces after it takes the set it unloads the rear and it jumps out a little more. i suspect i am bouncing off the stiffer part of the spring and it is underdamped. more rebound in the shocks should help.

james

Foureagles

Pulsr:

There's certainly nothing wrong with just showing up and running as-is; you just happened to stumble into a thread populated by true coneheads! If I'm correct in assuming that you're new to autocross, then it's likely best to spend at least the whole first season developing skill without much touching the car. Little (in the beginning) things like tire pressures are fun to diddle with when you get bored, and a precision alignment is helpful, even to a novice, but you have a seriously fast car that doesn't NEED anything to make a respectable showing.

DSC/TC severely restricts available speed, and you'll learn to out-drive it fairly quickly (high-speed track & road stuff is a whole 'nuther matter). For example: On a local 2nd gear test corner I can not get My Dear Wife's 8 with DSC/TC on to exit faster than can her stock '90 Miata on all-season tires, but it sure is stable. With the nanny off, I can almost equal the speed of my much gnarlier Miata (and sense a few things I'd change on the 8).

If I were taking an 8 to my first autocross, I think I'd leave the DSC/TC on for at least the first run. That will let you concentrate on where you're going while hopefully keeping you below the threshold of having to re-focus on catching the car. Before long you'll become annoyed by those limitations and turn it off. The following run will make you feel like either a genius or an ***, and you'll adjust from there.

Come to think of it, I wouldn't mind having those systems on my Miata for my first lap on an unfamiliar course. I always intend to make that run a slow learner, but inevitably succumb to the red mist, go right over the edge, and have to scrabble back.

Good luck, and please keep us posted.

{{{{