justjim

I got a chance to track test my Progress front and rear sway bars Saturday at Sebring. Started off with the rear bar on soft and the front bar on the middle hole. With the OEM springs and shocks and my camber maxed out at -1.2 in the front that setup caused some understeer. I tried dropping the rear tire pressures which helped but I moved the rear bar to full stiff at lunch time. Stiffening the rear bar helped balance the car but I was never able to equal my best time of 2:41 I had in November.

I had hoped to drop my lap times but the temperature was 98 plus at the track and I think the heat kept my lap times up. During midday the temp gage in the car moved from the normal 1 click to the left (cold) of center to 2 clicks right of center (hot) after several laps of pushing the car. Anybody know what 2 clicks to the right of center would be in actual coolant temperatures? I may have to get a gage cluster to keep track of engine temps. Backing off a little brought the temps back down and turning on the heater allowed me to back to full speed and keep on running at normal temps. Needless to say it was hot in the cockpit. By 3pm the tires were getting greasy and I noticed that I had corded the outside of the driver's side front tire. I think a combination of lack of front camber and understeer in the morning led to the increased tire wear on the front.

Scott, aka "Swoope", showed up while I was switching back to my street tires. Scott and I went out for the final session on street tires. Lots of squealing and sliding but the car was fairly well balaced. If I got a little push, letting off the throttle would bring the rear end around controllably. Dragging Scott around on street tires added 10 seconds to my earlier lap times. I think I sweated a few pounds off him with the heater on. Thanks for the help Scott, its good to put a face with the name. Funny he don't look like his Avatar.

Buckeye_rx8

I have the progress bars as well and think the balance is best at full soft in the front and full stiff in the rear. Even with this setting I feel the car still is understeeing. I am considering running the stock bar up front just to see if I can induce more balance.

dieselsdad

aren't you backwards? Seems you need MORE front bar and LESS rear bar, unless your car is front wheel drive.

TeamRX8

iTrader: (25)

the swaybar settings are dependent on the rest of your setup, anyone who claims one pair of settings is better than another really doesn't understand the setup process

justjim

Absolutely right. Different people are running different springs, alignments, and tires, so what works for me might be inappropriate for someone else. That's why adjustable sway bars are nice. At the moment with only -1.2 camber up front I am somewhat camber deficient at the front, hence the reason I backed off of the front bar for more traction up front. When I had it aligned, I asked the technician to maximize the front negative camber. He said he had but I was looking at the adjustment markings on the camber adjuster and it doesn't look like either one is maxed out, maybe I can get another couple of tenths of negative camber. I might also experiment with a little toe out. If I could get more traction out of the front I could conceivably go back to the stiffer front setting.

Buckeye_rx8

True...but I was just commenting on the settings and adjustability of the sway bars as that was the topic of this thread.

To fill in the gaps the rest of my set-up includes the JDM version of the JIC magic coilovers. My front spring rate is 680 and rear is 540 and I run 4/5 stiff on the dampening in the rear and 1/2 in the front.
My camber is -2.6 front and -2.2 rear -- Toe is zero on both.
Tires are 245/45/17 Potenza RE01R's and air pressure is 42 front and 38 rear (but I am still playing with this) at track temps.

...I think the progress bars and agency endlinks are a great improvement over stock "material wise" as they are much more beefy, but I am not convinced that the front bar is needed (within the confines on my set up). IMO even on the softest setting it induces "a lot" of understeer on "my" car. I like a balanced to slightly loose car for tracking and the front bar has made it difficult for me to achieve this.

justjim

I dunno, with my setup having the front full soft and the rear on stiff gave me some oversteer on the street. I didn't fully test this setting at the track and I may try it but my initial impression at the track was to keep the front on the middle and the rear on stiff. Currently back on the street I have them set on soft front and soft rear. Again I think it all falls back on the individual suspension and tire setup the individual has. That's one of the things I like about the RX8 compared to my previous car, even in stock form you have a range of adjustments, and the adjustable Progress bars are a nice complement to the system.

On a side note I just discovered (I think) that I may be able to get more camber out of my front. Last night I went out and set my front camber bolts to the maximum. When I had my car aligned I asked the tech to maximize the front camber and he said he did and it ended up at -1.2. Looking at the Mazda manual I realized that he didn't maximize the negative camber, in fact he was 2 ticks off which by the diagram below is 41' or .68 degrees. The center tick apparently should point to the centerline of the vehicle for max negative camber. Somebody can correct me if I'm wrong. By that calculation I've changed from -1.2 to -1.9 degrees which would be significant. I'm going back to him to check the camber and the toe which I may have altered when I changed the camber and I shall have a "conversation" with him. It will be interesting to see if I was able to get more camber and can keep it without messing up something else. The car feels good, with less understeer, and tracks well down the interstate. We'll see.

Buckeye_rx8

LOL I don't think I'm backwards, but as mentioned this all depends on your set up and one can accomplish balance a number of ways. Spring rates and dampening are one way, aggressive alignment and varying tire pressure is another, and sway bars are another, and even your ride height (rake) can play a role. It is really a balancing act when you get to the heart of it. From the factory the 8 is biased towards understeer for safety reasons. As I have begun to tune the car for the track I have noticed that adding a larger/stiffer front swaybar in my setup induced a lot of understeer. Granted I have extremely stiff coilovers on the car. Also, I have a lot of additional bracing that creates less chassis flex.

Secondly, I guess it depends on your driving style and what you want the car to do.

If you want the car to rotate more (like I do) you want the front to "grip more". Over steer. Stiff rear does this.

If you want the rear to follow the front you want the front to "grip less" (or push). Under steer. Stiff front does this.


By adding the stiffer front sway I noticed an increase in under steer-- On my car's set up.

Hope this helps.

Highway8

iTrader: (11)

I know nothing about making alignment adjusments but the guy who did mine said he can get around -2 out of the front, maybe more.

I also have the progress tech bars. Middle front and firm rear. I run 245/40 nto1's, kw variant 3 coilovers (lowered .75 and very firm). I had almost no understeer problems except if i was off throttle or way to fast for a turn.

As a side note, I used Racing Beat brackets and bushings for the front bar instead of the progress tech ones that keep getting talked about.

TeamRX8

iTrader: (25)

other settings and adjustments influence over/under-steer too, so it comes down to how much body roll you do or don't want

Highway8

iTrader: (11)

I was under the impression and from my experiance driving my car on road courses, the less body roll the better. So why would someone want more body roll? Assuming it is a dry track. I know when it is wet, everything changes.

The only thing I can think of is that with more roll in the front, it transfers more weight to the outside and off the inside tire but even more weight off the inside rear tire which would decrease grip in the rear and help the car rotate. But for me, I like it flat in the front so i get as much grip on both front tires so i have less understeer. I push my nto1's pretty hard and in many turns I am sliding all four wheels, so i can not sacrifice grip on any corner, I need them all to be working.

Highway8

iTrader: (11)

If I may comment on your setup and ask a few questions, it is much different then mine. I am not trying to say there is anything wrong with it, it is just different from my own and I want to learn more about what works for other people and why.

1ST- You have a lot of negitive camber in both the front and the rear. Advantages of negitive camber is that when the car rolls, the outside tire becomes flat and gives you more grip on that tire. Negitives are that you have less tire touching the ground (less grip) when accelerating, which on the rear is no big deal because we dont have tons of torque. You also have less grip when braking, and the inside tire becomes almost useless when you are pushing the car hard.

2nd: You have you suspension very stiff/firm in the rear which is not taking advantage of the negitive camber, so why do you have so much neg camber in the rear?

3RD: You have higher front tire pressure then rear tire pressure which is decreasing your grip in the front. Switch your front to 38 hot and your rear 42 hot and it should help the car rotate much better.

4th: I think the reason you get understeer with a stiff front bar is because of your negitive camber. If you go to something around -1.0 to -1.2, you might find the stiffer bar works much better and you might end up with a faster, better handling and better braking car.

I was talking to a long time race car driver and owner of an RX8 talk about the RX8 on the track and 3 things stood out to me. 1- "It is amazing how much distance you can gain on someone when they are on the brakes but you are still on the gas." To me that means brake late, brake hard and brake right. You must have a great braking car, our brakes are great but with a lot of neg camber you loose grip. 2- "Dont start to accelerate out of a turn until and unless you can stay on the gas all the way through the turn." Tells me that I want a car that handles well in the turns on acceleration because the faster you are on exit, the faster you will be all the way down the straights. 3- "If a car was set up perfectly, the left and the right side tires would have identical tire pressures because they will both be working in every turn.". All courses are going to either have more left or more right hand turns, so one side of the car will do more work then the other, but if it is set up perfectly, both sides are doing the work to rotate the car. 4 tires that grip are better then 2.

It keeps getting said and I agree, many things effect oversteer/understeer, including how someone drives the car. But for a specific car, track and driver, there is going to be perfect setup. Each owner/driver needs to make adjustments (usually one at a time) untill he/she finds that perfect set up and dont just go by feel, watch you lap times. Sometimes when you feel faster, you are actualy slower and sometimes going slow makes you faster.

justjim

These comments weren't directed at me but I'd like to put my 2 cents in anyway.
The amount of negative camber he has probably isn't large enough to really be adversely affecting his braking IMO. Furthermore, with both my OEM sway bars and the Progress bars set on middle front and stiff rear the inside front wheel is off of the ground when pushing hard on turns (I have video confirmation).
A stiff rear is only a problem is you are losing traction under acceleration due to the roll resistance and unloading the inside wheel or causing other unwanted oversteer. If the combination of camber and tire pressure allows it, go ahead and stiffen the roll resistance in the rear.
Although what you suggest might work it is generally better to lower tire pressures below optimum to decrease traction. A graph of tire traction vs tire pressure is a lop-sided bell curve, and the fall off in traction on the low pressure side of the graph is slower and therefore easier to calibrate the reduction in traction. The fall off in traction on the high pressure side of the graph is sharper and more precipitous. Overpressuring (from optimum) a tire tends to make the traction reduction dramatic and can make the car skittish. One can debate what the optimum tire pressure for the front or rear might be, 38 or 42 or whatever, but putting less than optimum in the rear to reduce understeer is a reasonable tactic and it is the way I would go. Overpressuring became popular on autocrosses where a skittish car is less of a problem than on a high speed sweeper with concrete barriers around you.
A stiffer front bar will reduce traction in the front. Whether the reduction is enough to cause understeer depends on all the other factors, but increasing roll resistance, whether by stiffer sway bar or stiffer srpings, will reduce traction in that end. The camber you suggest,-1.0 to -1.2, is based upon my own experience, not enough. I'm currently running -1.2 up front and would be happy to have about -1.8 up front. I corded the outside of my front tire with the -1.2.

Buckeye_rx8

No...no offense taken. I am still trying to iron out a lot of things on my set up so making me think about and explain my thinking is a very GOOD thing.

First off justjim makes many good points in his post concerning your questions...so I will try and add to his thinking or comment on where we differ in opinion.

Your first comment on camber is a good one and under isolated conditions what you're saying is largely correct. However, in my experience, the loss in braking/acceleration is usually outweighed from the gains in having a larger tire patch during hard/prolonged cornering. I am willing to sacrifice this because the 8 already brakes so well. In fact I have yet to find the limit with my set up on braking (Stoptech rotors with Hawk HP Plus pads). I’ve only done 2 track days in this car so I have a lot to learn still.

As far as why I have so much in the rear...(you're gonna laugh) One of the camber adjustment bolts on the rear is siezed at -- you guessed it -2.2. So I had the tech set the other side to -2.2. I actually wanted to run in the neighborhood of -1.6 in the rear but since I didn't have an extra camber adjustment bolt with me, I decided to go with -2.2 on both. That was why I went a little higher up front.

Number 3: I am not a tire expert or material physicist, but I think you may have this one backwards, because it is my understanding that a higher tire pressure is going to give you more tire on the road and consequently better grip. This is obviously going to come at the price of increased and irregular tire wear and tire cupping, but you've got to pay for performance.
Again, this is a general statement and I am sure there are certain high torque situations like drag racing where this might not be as true.

I think justjim makes some very good points in this regards.

Number 4: In my experience you want lots of neg camber up front with a RWD car. I've spoken with several race teams on this and all of them run very high negitive camber in the front. For what I am trying to accomplish (nuetral to oversteering tendency car), I don't think decreasing the camber up front is a good idea for situations involving road course driving/racing. You might pick up a little bit in braking, but I just can't see this making up for sloppy handling in the corners. Furthermore, I actually drive my car to the track and I can't afford to be late braking and risk hitting a tirewall. I would prefer the added stability in the twistys. Plus, "for my set up" (getting back to the whole topic of this thread for a second) running at the full stiffness setting or middle setting on the front progress anit-swaybar is making "my car" push already. Anyway, I don't think adding camber to the front is going to help me, but I am open to trying it if I can take some out on the rear.

Very interesting end to your post by the way...that was some very good food for thought.

Although this post sort of contradicts what is happening on my car. Ron Carroll from Meyer Motorports posted this on his philosophy of setting up their teams 8. I started my setup from this post.

“OK my philosophy on car set up is to have a very compliant car with stiff sway bars. This works well on cars that are still driven on the street. Since I don't know where your guys cars are at I am going to start with the basics. OK with this type of set up the shocks are very important, so if you are still running stock shocks I would recommend replacing them with KONI Yellows or maybe 3011's or 2812's, this will give you adjust ability which will help when you get to the event. Now you will need adjustable spring perches so you can change your ride height and corner weights( this is very important).
As far as spring rates, I like to keep a 150-200 lbs spread between the front and rear, so maybe start with 500 lbs front and 300 lbs rear, this will depend on what you are doing with the car and the track you are on. Now the best part, sway bars, this is what will make you car handle in the turns. I recommend getting the biggest front bar toy can, make sure it is adjustable, because you will need this to be able to dial it in, you will be adjusting this a lot for different events, as for the rear bar you may or may not run with the rear bar but you need one that way if you are having trouble getting the car to rotate you can hook it up.

Now setting the car up, front toe: 1/16 total toe out
rear toe: 1/32 toe in on each side
Camber: This will depend on all of the above
stuff and what you end up with, but I
would start in the 3 degree range.
Rake: Between a 1/8 and a 1/4 inch


So there you have my base set up, this is just a starting point, it will take a lot of tweaking to get it right for your driving style and your car.”

TeamRX8

iTrader: (25)

I'd recommend fixing your rear adjuster and dropping rear cambers as you suggested

my experience with R compound tires on an 8 is dropping the rear tire pressure increases rear grip and vice versa, this can likely change at the extremes and is typically dependent on a variety of other factors so there are no hard, fast rules other than to test different things and keep good records of your resulting impressions. I generally shoot for an optimum front tire pressure on RWD and not vary from it, instead adjusting the rear tire pressures only to make slight handling changes. This probably applies more to Stock class type applications where front camber is limited, making front pressure more critical.

Highway8

iTrader: (11)

Again what is optimum tire pressure for r-comps? I was under the impression that with the NTO1's it was high 30's low forty's and from my experiance, when my hot tire pressure exceeds 42PSI, I loose grip. I aim for the low end of optimum on my fronts and 36-38 HOT and the high end of optimum for the rear 40-42. It has worked for me.

I am still confused about how and why a stiffer sway bar or stiffer front suspension can reduce grip in the front. If someone can help me out with this one I would appreciate it. My only thought is that if you are too stiff for your negitive camber, then you never get the tire patch flat. So stiffer suspension = less neg camber, softer suspension = more negitive camber.

justjim

Although it is a bit more complicated than this, increasing roll resistance basically transfers load to the outside wheel of the end of the car with the increased roll resistance. To help visualize what's going on think in terms of extremes. If you had an infinitely stiff anti-roll bar on the front and no bar on the rear, the car would roll in the corners and the inside front wheel would be several inches off the ground, the outside front would bear all of the front load and both rear wheels would be (relatively) more evenly loaded and firmly planted on the road. This would generate significant understeer. Turn this around and the opposite would happen. Stiff bar on the rear, inside rear wheel comes off the ground, outside rear heavily loaded. Front no bar, both wheels evenly planted on the ground. This would generate oversteer. Thats why rear engined Porsches have stiff front bars and front wheel drive cars have stiff rear bars. With the more balanced RX8 the difference in roll resistance between the front and the rear is less pronounced and people are twiddling the adjustments to fine tune the balance. Off course changes in roll resistance have to be taken into consideration with other factors which can augment or nullify the oversteer/understeer effects of changes in roll resistance.

General rule of thumb is the end with the softer suspension sticks better. Obviously there are limits to this, you don't want cars hoping all over the place, but it is a misconception that stiff equals sticky. People stiffen their suspension to gain control but it can be overdone. Take a stiffly sprung car properly setup for a smooth track to a bumpy track and see what happens.

TeamRX8

iTrader: (25)

You're dwelling too much on generalities, it depends on the particulars and can go either way within a given range or the extremes and based on other parameters. The hardest part to get across to most people is that there are no simple answers, only complicated details .... details matter, which is why some people can make a big front swaybar work and others can't.

pgrothe

First thing that should be done on a track car is getting it corner balanced. I also have the Progress Sways and a good set of coil over. The first thing I did is getting it corner balanced. My front sway is at full stiff and the rear is also at full stiff (I don’t have any choice for the rear because otherwise the end links knock on the headlight sensor)

My car is almost neutral with a little bit of oversteer, which is exactly what I was looking for.