Originally Posted by Beast From The East

Hi, gang. I'm joining up on this thread, which I've read with interest ever since Howard started it.

I started out with AD coilovers and 550/450 springs. on 8.5/9.5 BBS RGR rims. Went from old Toyo T1S tires to BFG R-1s, 255/275, which was a big help. Still, like Howard aludes, the back end was happy, esp the lower the gas tank got. So I went and solved that with new goodies:

http://www.headonphotos.net/gallery/...zda/index.html

The new wing is obvious (JKLs GT-A **** replica), their rear diffuser is a bit more difficult to spot in the photos.

Back end now sticks. On a higher speed track like Thunderhill, it is wonderful.

New problem - the faster I go, the looser the front end gets. Gee, wonder why? Based on all of Howard's advice, I has a suspicioun that I'd lose grip in the front as I increased speed with the wing pushing down harder and harder. I'm still faster in turn 1 now, but it is unnerving to feel the front end not want to bite.

We're working on a splitter now. I also don't have a race seat yet, I hear good things about Kirkey's Intermediate Road Race seat, esp for the cost. I could sure use it, as I'm now fighting all sorts of new forces and the stock seat doesn't cut it anymore. This is on the list (funny how Howard just said I need one).

http://kirkeyracing.com/index.php?li...&code=Series47

I also have not corner balanced the car, I've just used the 'even height at the fenders' routine...however, now that I've gutted the car's interior, who knows what sort of weight distribution I have now. I will get the car corner balanced before my next event.

My father says he's discovered a new oxymoron - we call it Racing Budget. He's 63 and kicking tail in ST2 down in AZ, should go to Nationals this year. Hope to join him someday.

Beast

Originally Posted by howard coleman

So the FD is a super car. It can be made super better. It can also be screwed up. Let’s make it super better.

First let’s start at square one. The FD is a front engine rear drive car. As such, the primary challenge will be to promote rear traction. When you get things dialed you will be focusing on the back end. Think of road racing as drag racing from corner to corner. Consider two cars both able to run identical quarter miles. If one car gets a 1 second head start it will win the drag race.

If you can put your right foot down earlier coming out of a corner than your competitor you will be looking at the next corner first.

Driving fast and being able to get the most out of your car is about feeling comfortable. Being comfortable is about your car telling you what it is about to do in advance. Properly set up your car will talk to you. A properly dialed racecar will give you advance notice so you will find it easy to drive at the limit.

The opposite is… “it just snapped on me.” Spoken typically by someone who has just had an offtrack excursion.

To go fast you need to trust your car.

Which brings me to subject one… lateral weight transfer. Ideally you want equal weight on your lateral tires. Too much weight causes the tire eventually to wash out, lose traction. Further, every pound transferred to the outside tire is removed from the inside tire diminishing it’s value.

There is a major point of confusion here that needs to be cleared up so you can get tuning.

There are only two items that determine total lateral weight transfer…

Center of gravity

Track width.

The typical FD weighs 2900. add 200 for the driver… 3100 pounds. Remove the unsprung weight (wheels/tires, brakes, half of the A arms, half of the shocks/springs, half of the swaybar, half of the driveshafts). Call it 350 pounds.

So… 3100 minus 350= 2750 X 15.5 (center of gravity for stock FD is 17 inches, our track car is lowered a bit) X 1.1 G’s divided by the track (stock is 57.5 minus your positive offset wheels so we use 55.5) = total lateral weight transfer in a 1.1 G turn.

That’s 844 pounds of total lateral weight transfer.

So what can you do about it? Given the ride height and track… Nothing.

But if you put stiffer springs and roll bars on the car it won’t roll as much. Do you see roll anywhere in the aforementioned equation? You can weld the suspension solid, you can bolt on 2000 psi springs and a 6 inch swaybar.

And you will still transfer 844 pounds.

But springs and roll bar stiffness can apportion (front to rear) where the 844 pounds transfer. By changing the longitudinal roll stiffness you can move more of the 844 pounds to the front or to the rear.

And that is one of the ways we can trim our chassis… understeer, oversteer. If, for instance, the chassis is balanced and we increase the rate in the rear we will transfer more of the 844 rearwards and will tend towards oversteer.

BTW, a common mistake when attempting to longitudinally balance a chassis is to work on the wrong end. Let’s say the car is oversteering (rear loose). You could stiffen the front by adding spring or bar but you would be decreasing front grip so it would balance against poor rear grip. You just lost total grip.

The correct path would be to find a way to increase rear grip.

Stiffer springs and shocks do decrease body roll and that is generally a good thing to a point. The FD, due to it’s double A arm front and rear suspension and attendant negative camber gain on bump, is not as effected by roll as most other cars. That is as the crucial outside wheel in a turn moves up into the fenderwell w body roll the suspension adds negative camber thus keeping the wheel properly cambered to the track.

That’s why the FD takes few prisoners ontrack.

Some cars need to run huge springs and bars to kill roll because their suspspension goes off camber in bump. These cars with too much spring rate are very hard to drive near the adhesion limit.

The stock FD spring rate is 263 pounds per inch in front and 195 pounds in the rear. These are my numbers from my Longacre Digital Spring Checker. Just FYI, with linear rated springs the rate increases with contraction. The second inch of the FD front spring is 526 and the third is 789…

I run 432 front and 378 rear. Expressed metrically 8 KG and 6 KG. I am delighted with this rate. If my springs vaporized I would repurchase this rate. It works on the track. It works on the street.

That said, Frank runs 566/422 or 10Kg/8Kg. I consider this rate the outer limit.

Remember, both rates transfer the same lateral load. The higher the rate the harder it is to drive at the limit.

Let’s talk spring and shock options….

Interestingly, the suspension area is one where more money does not necessarily buy more speed. Although there are plenty of vendors wanting to sell you high dollar stuff…

You have two options.

Replace the OEM springs and shocks with aftermarket.

Replace the Oem springs and shocks w a unitized component known as a coil over.

Both work very very well if you select the right stuff.

While there are a number of options I have been extremely happy with the Eibach Pro Kit springset. The rate is 350/255 and they lower the car close to the proper ride height. At a price of around $200 and often seen in our classifieds these extremely high quality springs TRANSFORM the FD. Do not discount this easy to install option.

I owned a Shock Dyno for a number of years. I dynoed 31 OEM FD shocks. They varied between 3500 and 135,000 miles. Interestingly they all dynoed similarly. I like them with the Eibachs.

There are various other aftermarket shocks that would bolt in but I suggest you just try the springs. You will be surprised.

The Coil Over market is sort of like oil. I have always used, and have been sponsored by Mobil One. It has worked for me. Could I really tell you why it is better than XXX? Nope. But if you start a thread on oil you will have many posts on the subject. Ditto Coil Overs. Double adjustable, digressive blah blah blah.

The first question to ask re coil overs is WHAT IS THE SPRING RATE. If you want to slide around buy something with a rate over 10Kg. Or pump up your tires to 75 psi, it’s the same thing.

It is really easy to get into overkill on coil overs. If that’s your deal fine. For the other 95% including me I will be very happy with my modestly priced Tein Has. The valving, remember I have a shock dyno, with 16 settings will give you everything from loosey goosey to rock hard.

My view is after you have spent a few years on the track and have a handle on things and you have nothing better to do you might consider something up the food chain.

There is a lot to learn in the basics area before you get to esoteric. Admittedly that just my opinion here.

Then there’s the “pillowball” upper coil over mount issue. In a word, don’t.

The upper mount of the OEM spring is a rubber insulator. This insulator helps absorb lots of unwanted vibration. There is not one bonafide engineering reason to change the upper mount to steel. Yes, “pillowball” equals steel.

Here’s the key… the upper mount has NOTHING to do with the suspension geometry. There is NO performance advantage. The A arms scribe the geometry. If you do coil overs retain the upper rubber mount.

Swaybars are always an excellent way to control roll and tune for over/understeer. The additional roll stiffness a properly selected swaybar provides allows the springs to be a bit softer thus allowing the tires to spend more time where they belong contacting the pavement.

I am in the late stages of changing my swaybars from OEM. I am installing a Speedway Engineering hollow front bar (35 inches X 1.25 O D X .188 wall thickness). I bought Speedway’s collars and mounting brackets and will purchase their aluminum arms. This will add approximately 60% more roll stiffness than the OEM bar. It will have 3 fine tuning adjustments. I will bend the arms, drill the holes and fab the links.

Mazda went a little crazy lightening the front swaybar mount. Lots of swiss cheese lightening holes… it is probably fine with the stock bar but when you upgrade to a stiffer bar you MUST lose the mount. I strongly suggest you contact Widefoot and purchase their swaybar mount.

I spent some time looking at rear bars. Remember it is important to keep the rear a bit soft to provide traction. (I run my front shocks 7 clicks from full soft and my rear 2 clicks from full soft). After doing my homework I decided to go with the Tanabe 20 MM hollow rear bar. It is up 36% from my 93 bar. I haven’t been ontrack with either but think they will work well considering my spring rate is up a bit over 60%.

Continuing talking hardware… There are lots of bushings in the FD. Most of them should be just left alone. I would not change any bushings in the front. In the rear there are two sets of bushings that should be changed.

The lower longitudinal link that absorbs all the braking and acceleration has a big fat rubber bushing in the front. It needs to be replaced. I really like the beautiful aluminum OEM suspension members and consequently removed the bushing and substituted a nylon item. It is also easy just to replace the link with an aftermarket item that employs a spherical bushing. If you don’t replace this bushing your wheels will be toeing in and out on acceleration and braking.

The other set of bushings are the two at the top of the differential. If you place a jack under the diff you will find it moves up almost an inch before the car starts rising. A big no no. lots of driveline chatter. Nylon works for me.

I believe there may be a higher durometer (stiffer) bushing available from Mazda. That would work.

some replace the rear toe links. while there may be a miniscule amount of non metal in the spherical bearings they look solid to me so i am fine with stock.

Tires of course are a key. I suggest running tires that offer a tread width equal to your rim width. I run Enkei NTO3+M wheels. 18 X 9.5 front and 18 X10.5 rear. 255s front, 295s rear.

We certainly will be offered more tire options this year as the market is changing rapidly. Lots of options in the stickier 100-200 UTQG category.

That’s about it for the hardware let’s move on to setup and tuning.

Chassis setup is HUGE. You just have to get interested in it if you care about going fast and having fun at the track. I will give you a nice dual purpose setup and once you get to the track if you want to go fast you will be changing some of the settings.

Alignment of the FD is an easy task for a shop so don’t let them give you a big song and dance about it. Tell them you want the car set to these specs. Period. Further, arrange from the getgo to get a complete printout of the before and after.

Tire pressure 30 front 27 rear
Ride height if you have coil overs should be set at 25 inches at the top of each wheelwell.

Toe in front between a 1/16 and 1/8th inch
Toe in rear zero
Camber front and rear 1.2 degrees negative
Caster equal minimal
Zero rear thrust angle.

Prior to going to the track I suggest you place a tie wrap on each shock absorber piston rod and push each wrap down just before going out. When you come in they will tell you how much travel you are getting.

For one inch of bump at the wheel the shock moves .6 of an inch in the front and .68 in the rear. You are looking for no more roll at the wheel than about two inches.

I recommend if you plan to track your car that you purchase an accurate tire pressure gauge with a bleed valve and a pyrometer. You are almost blind at the track without a pyrometer. Good digital pyrometers can be bought for approx $150 and are essential.


Set your air pressure and run 3-4 laps. Pit, check your tire temps immediately, and your pressures after… record all 3 temperatures from each tire. You want 20 degrees more temperature on the inside third of each tire. If you don’t have it you need to adjust your camber. I do it at the track in a few minutes.

The pyrometer will tell you the correct tire pressure for each corner of the car. All will be different.

That’s about it for now. I hope this will be of help. It has worked for me.

howard coleman

Originally Posted by Callsign_Vega

Howard, great read. I beleive you just laid out exactly what I will buy for my suspension. Would anything in your post change significantly if say I ran 285's front and 345's rear with a wide-body kit?

Originally Posted by Howard Coleman CPR

Pasadena....

it figures.

Originally Posted by Howard Coleman CPR

re Pasadena... Cal Tech... just trying to inject some humor. i am insanely busy for a few days but look forward to your calcs.

during one of my Runoffs at Road Atlanta i was doing a final chassis setup the night before the race and had the car on the 4 scales. i had disconnected the front bar as i was jacking some weight around. lots of people were stopping by and i got to doing too much socializing. i forgot to reconnect the front bar link!

i knew i was totally screwed on the pace lap. with less roll stiffness in the front i burned up my rear tires in 4 laps of racing and parked it.

another racing lesson learned.

racing is the ultimate task master. it teaches so many lessons.

after seriously racing for 22 seasons it is absolutely impossible for me to do anything 95%. the other 5% will always come 'a calling.

thanks for your contribution and i look forward to playing w it.

howard

Originally Posted by Howard Coleman CPR

i was unable to play the vid. "files structure invalid" whatever that means.

i like that you are juggling springs and that your tire pressure is low.

i would be very interested in what you are actually getting for travel at the shockrod. also tire temps and your tire pressure after 3 hard laps.

hc