zenilder

I was thinking about setup configurations today. Seeing as I don't have a number of different sized swaybars, I really can't experiment with configurations, nor would I likely have time to, given said number of swaybars.

Anyhow...

My mind is set on drifting/good turn-in/slight-to-good oversteer. I know, I know... It's hard to make a front/front drift. It's been done before on a number of cars.

I would like to talk theory and practical applications.

I have a DX, so no rear bar. If I were to get the biggest front bar, and keep the rear (no bar) the same, would I see better turn-in? Would I just experience fish tail all the time? Would this even be a good idea for normal driving conditions (daily task of going to and from work, etc..)? If not a good idea for normal freeway driving, i.e. some ***** decides to cut you off while you're traveling at ~75mph, him/her 65 or less, would it only be applicable for track to turn fish tailing into drifting? (Course that would also bring the steering rack into play, and seeing as it takes three full turns of the wheel to turn the tires completely to one side, would need to modify the steering rack somehow to control the fish tail and bring it to a drift.) Or am I talking complete utter bullshit because it can't be done?

Which would be better, the 21mm or 20mm with the biggest front bar, or larger in the rear. I know that increasing the size of the bar in the rear increases understeer/reduces oversteer, so I'm already set not to go much bigger than stock in the rear.

Can anyone provide some info the novice autocrosser here?

Thanks in advance.

zenilder

I thought CMS did, but I don't see any listing on his page for front bars, only rear.

I did a search on this forum, and only found that the zx2 has the largest front bar. I might land up looking for one at the yard, then. The bar is 1".

Is there somewhere else I can source a larger front bar?

Thanks again.

mazdaspeedwest

well, i am running the stock bars with polly bushings. The car oversteers on command, but still has a slight push (the bolts are are pretty tight

I remember when i broke a rear frame mount, it felt so loose and wiggly i knew right away something was wrong....

if anything, i suggest the F/R LX bars, or go for the kind set-up w/front LX bar/ST bar combo and the CMS rear bar.

MikeD

Your DX should have a rear sway bar...unless you removed it. I too have a DX and installed the ST rear sway bar and also upgraded the front bar to a stock LX bar since it is solid vs the DX's hollow front bar. The combination works well and I can actually at will coax the rear end to step out. I hear the CMS rear bar makes stepping the rear out a bit easier so perhaps that's your best bet for hangin the rear out.

Increasing the front bar and not the rear will result in more understeer. Increasing the rear bar and not the front promotes more oversteer. In my opinion, if you want to be safe in those emergency situations, you should increase both at the same time. Otherwise you could be along for a scary ride.

FYI: a 22mm anti-sway bar provides 62% more torsional rigidity than a 21mm bar, 186% more than a 19mm bar, and an incredible 382% increase over a 16mm bar! (From http://www.spmotorsports.com/contour_swaybars.html)

Davard

Generally speaking, a bigger front bar will increase understeer. Some stock class autocrossers use bigger front bars on FWD cars, but only because they can't change rear ones, and more body roll means more roll-induced positive camber. But it does increase steady-state understeer and wheelspin.

A bigger rear bar will increase oversteer (or decrease understeer) in a FWD car. (on a RWD car w/o a limited slip, a bigger bar creates wheelspin).

Using a ZX-2 front bar with a stock (or no) rear bar would create SEVERE understeer. The stock ZX-2 has a 1" front bar and a 1/2" rear bar and understeers horribly. It would take a 1" rear bar to make it anywhere near balanced (or 600 lb rear springs). Similarly, using a 1" rear bar with no front bar would produce massive oversteer.

And the Protege should have a 20mm rear bar (although '92+ LX's have a 21mm rear bar) according to the Mazda service manual.

And the web site is incorrect. With similar materials, a 22mm bar is 20.4% stiffer than a 21mm bar. (Torsional) Stiffness in the 4th power of radius. So a 22mm bar is 46% stiffer than a 20mm (14641/10000=1.4641 or 46% greater).

Will Kalman (EGT winner of the SD and Atwater NTs, and the El Toro PS) and I are both running the ST front/CMS rear bars. We've both thought about changing to the ZX-2 front bar (major pain to change) to remove a little weight, free up the front suspension, and improve ground clearance (although the last is not longer a factor with Darryl's lower tie bar) (not loaded due to size--400k image)

As my car is set up, it is vary stable on the street. As long as tire grip is the same front to rear (I snap-spun on a practice day on new tires front/worn rear, because the rear tires had significantly more grip). I think mine is more spin resistant than a stock Protege. And the steering is plenty fast. Three turns lock-to-lock is average fast. Much faster and you get twitchy steering at higher speeds. For most autocrossing uses, you only turn about 1/2-2/3 of a turn either way at max.

MikeD

Just curious where you are getting your specs from. Seems every site has different % increases per mm in diameter you increase the bar. There has got to be only one way to calculate the effect of this type of increase. I'd be interested in trying to figure it out myself to see which figure is correct.

MikeD

I think your match is correct Davard. Here is the formula taken from http://www.spswebpage.com/tech/swaybars.html. SPS has been making Performance parts for Saturns long enough to know what they're talkin bout, so the math is the same.

twist = (2 x torque x length)/(p x diam4 x material modulus.)

the variables are the 22mm bar v the 21 mm bar

so twist =(22 to the fourth power)/21 to the fourth power)

twist=(234256/194481)

twist =1.2045187

So an increase from a 21 mm bar to a 22 mm bar will yield a 20% increase is stiffness. You are the man.

Davard

Of course, that assumes that the materials are the same. There isn't that much variation between most types of common steel, but some alloys (spring steel vs mild steel) will be much stiffer at a given size. Most swaybars (should be) are made out or spring steel (which will return to its original shape after being deflected, within limits, without hardening/becoming brittle).

And as you might figure, it's the material at the outer edge that is the most important. You can get the stiffness of a 25mm solid bar with a 28mm hollow bar with a ~3mm wall thickness, but with a 76% weight savings.

zenilder

Okay...

Well, I'm not sure where I developed the idea of bigger front bar equals more oversteer from.

Good thing I asked about it before I decided to act out my thoughts.

I guess I'll try and get the CMS's rear and see how it handles. After that, I'll determine if I want to go bigger on the front.

I want to see if the Pro can be a good drifter. I know, I'll probably be going through tires pretty good if I do manage to get it drifting, but it's all about having fun, right?

mazdaspeedwest

well, i feel the pro is already a good drifter, even on stock bars...it's all in the excecution

Davard

Yeah, throw in a little toe-out in the rear, a 1" rear bar, sticky fronts and hard rears, and you'll have trouble keeping the front tires in front.

In the LA region (autocross) a few years ago, they had a Hyundai Scoupe that they used as a Trophy car. If you won the previous race, you got to drive the Trophy car. This Scoupe had maybe 70 hp, about 7 degrees of front negative camber, 205/55-14 Toyo RA-1 front tires and 185/75-14 Rock rear tires, and a bunch of rear toe-out. If you weren't on the gas, the rear end came around. If you couldn't left foot brake, you couldn't drive that thing. I hit more cones on my first run in that thing than I had the whole rest of the season (then someone told me about left foot braking).