I'm still planning on running no rear bar for 2012, same as I did all last year. I think the reduced weight, increased traction, and lower cost are all worth it.

On the other hand it would be nice to have quick adjustability, and of course your spring rates could be lower if you had a rear bar.

 

What about the side effect of lifting the inside front wheel due to weight transfer when running no/little rear bar? When you transfer all the weight off the front tire while in a steady state turn it lowers the overal mechanical grip of the car. On my current set-up the spread sheets say it will pull 1.27g but if I add more rear bar and keep that front wheel on the ground it says if can pull 1.31g.

Now I understand the rear of our cars can only have XX amount of rear roll stiffness before the rear traction circle starts getting smaller (instead of bigger)but I'm not sure what that magical number is. People say wheel rate=to corner weight equals a neutral car but as everyone knows we far exceed that on the front of our cars.

I'm going to try to run some rear bar to try and help keep that front inside wheel on the ground. well see how it goes.

The kooks are very limited on putting power down when coming out of a turn on the throttle. I think this is the reason Matt hated the kooks. His rear roll stiffness on star-specs was way stiffer then the typical kook stet-up. Which in returned caused the rear to get loose everytime he got on the gas coming out of a turn.

 

I'm definitely going to try it out for a couple races to see if I like it or not. We seem to have very few long steady state corners in my area.

What sort of alignment are you running if you dont mind sharing. You can pm me if you prefer.

 

I'm definately going to try it out for a couple races to see if I like it or not. We seem to have very few long steady state corners in my area.

What sort of alignment are you running if you dont mind sharing. You can pm me if you prefer.
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Right now, about 3/16" toe in in rear, 0 toe front, 3 degrees camber front, 2.8 rear, I don't remember caster.

It definitely doesn't feel quite as good as having no roll whatsoever and instantaneous response times, and is probably slightly harder to drive, but I feel like it's actually faster and I still have way less body roll and faster response time than a lot of cars. We'll see how I do this year. Post back after a few events and let me know how you feel about it.


I'm going to run stiff enough springs in rear that I'll probably have similar roll stiffness ratio to you, so this is moot. We'll see how it goes - I'm not sure I'm right, I may end up going to a rear bar later.

 

I feel at least that running no rear bar lets you get on the power earlier and slows breakaway enough where it's actually easier to feel when the rear is about to let go. The only reason I'd think you'd want to run a rear sway is if you wanted to be able to drop your spring rates to be more compliant with bumpier lots. The choice then to run more spring and no bar or less spring and add a bar would have to be more dependent on the venues you expect to run. One could then argue that having softer springs with an adjustable rear sway would give you greater flexibility to adapt to different lot conditions but from my own experience and my particular driving style I feel that having more rear spring and no sway bar creates a more predictable feel and is easier to drive than less spring with a rear bar. I also think that on AP1s in particular having more spring is good as long as traction can be maintained to reduce bump steer caused by toe changes during compression. I'm no expert at this but these are some observations I made on my own car and NFRad's car when I codrove it.

 

Agreed.

 

I agree with what you’re saying. I even said in my post that it seems adding rear bar causes the car to get loose when trying to get on the gas during corner exit. I would like to think I can run less spring/more rear bar with the same rear grip as more spring/less bar. This doesn't seem to be the case though. I would also like to think it's a good idea to have spring rates that create a natural frequency difference of less then 15% Front/Rear. Therefore the rebound numbers front and rear will also be similar.
When running crazy staggered springs (cough cough) 850F/350R would result in a weird steady state turn balance. The car would put allot of weight on the outside rear relative to the rest. Which would reduce overall grip? Keeping the weight transfer similar front and rear produces a car that can achieve a higher lateral G-force number then a car that transfers all the weight to one wheel.
When you add a stiffer rear bar it helps keep that inside front wheel on the ground. So the real question is “where do you draw the line between to much rear roll stiffness and to much weight transferred?” If we run stiffer rear springs/ less rear bar relative to the front springs/bar can we offset the weight transfer enough to keep all the wheels on the ground and achieve a higher lateral grip number?
I might be talking out of my ass but to me it makes sense in my head. “If I disperse the weight transfer “evenly” between the front and rear tires the car will be able to hold a higher lateral G-force load.”
The trick is how do we…
-keep the stiff front end for fast transitions
-keep the car balanced during a steedy state turn
-keep the rear from letting go when I power into it during corner exit

I feel like if we can achieve these 3 things the car will be faster then the current “fast” set-up. The issue is I can’t figure out a way to crank up the rear roll rate any without upsetting the freaking rear tires. I feel like I unstick the front tires to match the grip of the rears. Even though it would be a better set-up if I could make the rear tires grip levels match the front without messing up the steedy state balance of the car.
If I’m full of shit please tell me so and explain to me how. I feel like I try to talk technical terms on here 95% of the time and no-one ever really wants to comment back or give their input or knowledge. It’s always “well I just go and drive, sometimes I do ok.” I’m a number, theory, and science based guy. I naturally think theirs a science to everything and everything can be figured out using number and theory’s. Just going out and driving without any knowledge of what your actually doing to the handling of the car when you change that bar setting or turn that knob seems like a running around in circles method of setting up a car. Maybe I should just go drive the car and stop thinking about what effects on handling changes make to the car.

 

I don't want to take this any further off topic but it is interesting that you state you are a science and numbers guy yet you aren't letting yourself experiment, for fear of what I don't know. Last time i checked experimentation was the conerstone of the scientific method. I won't claim to know all there is to know about suspension tuning... Far from it, but I think there is no better way to learn than to experiment, document, and see the results for yourself.

No one is saying don't research and educate yourself on suspension theory... I think that is why we are all here checking these forums... But I would argue that you don't need a spreadsheet to tell you that a car is understeering, and also a set up that might be theoretically perfect might be awful for someone with a different driving style. For certain I would say you will never know until you find out for yourself.

http://farnorthracing.com/autocross_secrets2.html

Suggested reading to show where I am coming from.

Back on topic... I am also curious how many guys who are running the miata rear bars are moving up to the new Gredon rear bar from the increased flexibility or are most of you satisfied with the miata bar?

 

Josh, have you read the book on vehicle suspension and damping by Jan Zuijdijk? He made a really interesting point there that race car engineers go through all kinds of calculations to determine correct damping forces for a particular race track but in the end making a fast racecar is a bit of black magic and intuition since in real life both the race track and the driving style of the driver are big variables that ultimately determine a fast car. He was saying that you could set it up to what you think is perfect from a theoretical/mathematical perspective but if the driver doesn't "feel" the car behaves the way it should it'll turn out slow laptimes.

He was talking about dampers but the same can be said for sway bars. The best approach is to use calculations to determine an optimal theoretical setting but you still need a ton of experimentation through seat time to determine which is faster for you. This of course gets particularly tricky if you codrive and you have very different driving styles from your codriver. However if you do get the opportunity to put a bunch of fast guys in your car as you make these changes, you should be able to see a trend in lower run times across the board if you are going in the right direction.

 

On topic, my gendron bar is making like a popping sound when I turn on an uneven surface such as going from driveway to street. I think it's the endlinks binding. Anyone have recommendations on replacements?