dradon03

iTrader: (2)

I think the rear is too soft and I need to pump up the rear tire pressure because my tires aren't as wide.

Howard Coleman

iTrader: (6)

"What do you think is causing your understeer?"

the stiffest end (that'd be front if you have understeer) slides first. so you either soften the front or stiffen the rear.

or

it could easily be your camber.... too much or too little in front. you need a pyrometer to answer this part of the question.

Jose

"I dont need to do the toe adjuster link?"

there are multiple opinions on the rear toe links. actually 2, yes and no. some think they have a significant amount of rubber in them. l do not run aftermarket toe links and think the stock ones work fine.

BTW, i completed my dyno testing for the moment ( 498 rwhp at 20 psi) and am planning to be ontrack, finally oct 11-12 at Blackhawk. yippie.
hopefully the thread will become a bit more interesting as we put our dual purpose setup to the test.

i will be running in Street Modified as i run street rubber.... Sumitomo HTR ZIIIs. shaved with special sauce.

hc

dradon03

iTrader: (2)

Thanks Howard, at least it confirms that I am going somewhat in the right direction.

In front I am already having rubbing issues with my bumper on hard bumps, so I don't want to go too much softer in front, also the ride overall on these coilovers is much softer than the previous combo of shocks and springs, infact this combo is even softer than my old OEM touring shocks and Eibachs.

jeroentje.nl

Howard,

What will happen if the car is lowerd more in the front ?
or if the rear is a little lower as the front ?

Howard Coleman

iTrader: (6)

"What will happen if the car is lowered more in the front ?
or if the rear is a little lower as the front ?"

with regard to what? lowered in relation to what ride height?

jeroentje.nl

If the the height is let's say 25.5 in the front and 25 in the rear.
compared to 25 front and 25 rear.

Will I notice the difference in handling ?

Howard Coleman

iTrader: (6)

no

jeroentje.nl

The front of my car feels very light.
It is littler the the rear but I do not how much.

in a long rolling turn.... the front feels not very stable.

car has no power steering

ptrhahn

iTrader: (9)

I think you want to be sure the rear isn't lower than the front. The car was built with some natural rake to it.

jkstill

iTrader: (11)

My autox setup is ST sways front and rear, 285/18/30 V710's, 550/450 Eibach springs front/rear 550/450 with Koni Yellows and Ground Control coilover setup, and as much camber in front as stock control arms allow. (2.5 degrees)

This is an autox car. I realize you are talking about a track car, but the issues are similar.

I was experiencing understeer with front/rear pressures of 28/26. After a couple runs of fiddling with pressures I swapped the ratio front to rear, and lowered the pressures a bit.

Front/rear is now 24/26, 2 lbs more in the rear. Much better now. Something to consider, and YMMV.

The car was also was rubbing the tires on the fenders (which are rolled) in hard cornering, so the car was raised .25".

s1mpsons

iTrader: (5)

Why do you suggest to have the inside 20 degrees hotter and the center and outside? I would tend to think you would want the temps to be equal at all 3 locations indicating entire tire tread is be equally used and not overloaded in any one particular location.

jose-rs1

iTrader: (1)

Howard,
Just wondering the diff betewen the FC and FD.
Most the guys I know that run FC use much diferent spring rates about 400's # in the front and the rear are very light 120-150#.
racetracks down here are very bumppy.
nobody is running a FD, what do you think the FD sring rates shoud be?
thanks
Jose

dradon03

iTrader: (2)

https://www.rx7club.com/showpost.php...36&postcount=1

Read my friend.

Snowblind113

Howard I was searching these forums and found a post that said you were running Sumitomo's HTR Z III's. As a brand do you feel comfortable with them? I am considering getting the basic Sumitomo HTR Z which cost 65 dollars. I had Goodyear Eagle F1's on the back but when taking a turn the sidewall gave out on the rear passenger side tire. I dont have the money to shell out more than 100 a skin (especially after these Goodyears were purchased just last year) at the moment due to college financing. Thanks in advance.

jeroentje.nl

Howard,

My car is alligned again today.
This time some settings to try:

front:
2.5 camber
6 caster
1/16th toe in

rear
2 camber
0 toe in


Sunday I have a time attack event.
only 20 minutes to test in the morning and 2 ours later one warm up lap... one hot lap... one cool down lap.
that's it. if I had 2 test sessions I could change something but with one is very hard to make a good adjustment.


In our country there are just a few track days.
Now I was thinking how can I adjust the camber easy between sessions.

This is what I found: http://www.rhdjapan.com/jdm-low/Nagi...D3S-RX-7-53519

If you do it right... and adjust the front and rear of this arm the same... the caster will not change.
Because of the steering arms are almost at the same height as the under arm the TOE will not change.

So this would be a good option to easy change camber or not ?

Howard Coleman

iTrader: (6)

adjustable (length) upper A arms are an excellent addition to any serious track driven FD for 2 reasons:

1. the all important camber adjustment becomes a snap. instead of screwing around w the inner lower control arm cam, which is limited in adjustment and hard to access you merely loosen the locknuts on the upper arm, move the adj a pre-determined amount and set the locknuts.

2. you gain a much greater amount of adjustment range. as the FD is lowered the wheels go into more and more negative camber. at a certain point the OEM adjuster is unable to dial out the camber and you are stuck. w the adj upper arms there would be no problem. further, if you recall earlier in the thread Steve Kan based on his tire temps needed more adj and was out of range so couldn't get it. until he goes w adj upper A arms he is stuck. yes he is going real fast but could be going faster.

during my road racing days i spent alot of time w short track guys. your local tube frame V8 pavement crowd. they are, or have been generally way ahead of the typical SCCA racer in terms of chassis setup. i used lots of their hardware and much of the typical front line SCCA GT tube frame car today resembles short track tech.

they all run tubular adj upper A arms. many adjust w inboard shims but others actually adjust lengthwise. they have replaceable outboard ball joints and the trick setup is to have the adj on the outboard end of the A arm.

these are easy to make, lightweight as they are tubular, and inexpensive... in the area of $75 per. obviously an upper A arm built as a FD bolt-in would be not an item you'd find at Howe or Speedway Eng but it would be really easy to fab.

someone should do it this winter and make a few bucks in the process. for the front and rear.

hc

gracer7-rx7

iTrader: (16)

I think AutoRND has a Superpro poly urethane inner bushing for the rear upper A arm that has an eccentric bolt that appears to allow for camber adjustment. Pretty sure I saw that in AutoRND's vendor forum...

Andrew.

iTrader: (4)

Hey Howard/anyone that can give some insight:

I went to get an alignment yesterday and before doing so, I asked the alignment guy if he had cornerweighting scales to see where I'm at. He didn't, but his friend down the street did. So I went over there and it came out as follows:

Without driver
RF LF
909 535 1444 50%

RR LR
553 891 1444 50%

Total weight- 2888

With driver
RF LF
920 592 1512 49%

RR LR
591 973 1564 51%

Total weight with driver- 3076

Notes: This is a '93 Touring (rear wiper, bose, sunroof, etc.) with an LS1/T56, AC, PS, aftermarket sound deadening and aftermarket heat shielding. The spare tire and about 20 lbs of miscellaneous crap I had were still in it while I weighed it too. It had about ~3/5ths of a tank of gas while weighing it as well.

The huge issue was the cross weights, they're WAY off. My alignment guy said he didn't want to touch the alignment settings till I had this fixed, because in order to fix it, I'd have to screw with my heights which would in-turn screw with my alignment. So I really haven't touched my coilovers until now, but when the car was in the air, I noticed the two "heavy" sides had a lot more shock length (height from the tire-fender) than the "light" sides. So after driving back home, the coilovers on the "heavy" side had MUCH more length than the "light" side, so I readjusted the front coilovers to have an equal height as well as the rears. The car doesn't feel like it's binding under throttle like it used to and it feels a little better (other than the wack alignment), that was the issue, right? Two other people have confirmed so, I just like triple checking

Oh, the rear sway bar was disconnected while cornerbalancing, FWIW. Thanks

Howard Coleman

iTrader: (6)

WOW!

how'd you do that? i wonder what your ride heights were that generated such amazing cortnerweights....

BTW, this just shows you how important ride height is as to weight distribution. i suggest you just reset your rideheight to 25 inchs all around, get rescaled and then aligned.

your alignment guy was correct to suggest you straighten it out before aligning.

hc

Andrew.

iTrader: (4)

The ride heights were ~25.5" all around, +/- 1/8th" .

25" all around is nice, but I drive through some crappy *** streets, so I figured I'd give myself a little bit more clearance.

When I "fixed" this yesterday, I restored the two "heavy" sides back to the same height as the "light" sides (these were totally untouched yesterday), and my ride height dropped to ~24.8" or so (from 25.5) all around, so the "heavy" sides were picking up the load of the "light" sides, giving me those screwy #'s...

Pretty amazing how you can totally shift the cross-weights of this car around

SKDTME

Real good post thank you. i have a question i want to have aluminium bush's made to mount the diff and that beam that runs up the side of the gearbox. only trouble is i drive my S8 RB modle every day and i would be a lot f work to take it apart and measure the bush's put it all back together then have them made then dismantle it again to iinstall them. would you happen to the the diamensions needed to make these bush's so i can half the work? thanks very much

Howard Coleman

iTrader: (6)

535--909
891--553

"The ride heights were ~25.5" all around, +/- 1/8th"

"When I "fixed" this yesterday, I restored the two "heavy" sides back to the same height as the "light" sides (these were totally untouched yesterday), and my ride height dropped to ~24.8"............................................ ............

i am trying to understand. you said that the ride heights existent when the car was scaled were 25.5 +/- 1/8th.

then you adjusted the higher ride heights to equal the lower ride heights i gather? and you end up at 24.8? how could this be if all 4 of your ride heights were 25.5 +/- 1/8th?

please explain.

secondly, if your ride heights were within a 1/4 inch, (+/- 1/8th), there is no way you would end up w 35% crossweight. either the scales are screwed up or your car is statically a mess weightwise. you can't jack that much weight around with so little differential.

since you are looking for a bit more road clearance i suggest you adj all 4 corners to 25.5 inches and re-weigh.

one other consideration... you disconnected your rear bar. is there a chance your front bar was not neutral?

howard

Andrew.

iTrader: (4)

I'm a bit confused too, but let me try to explain it a little better.

If I were to lift the car in the air, with all corners in the air, the two heavy sides would have a lot more length (gap from the fender-top of tire/rim/etc) than the two light sides.

This led me to initially believe that since they're touching the ground so much sooner than the light sides, they're absorbing quite a bit more weight than the light sides.

So I measured the height of the coilovers on the heavy sides vs. the height on the light sides, and the heavy sides were QUITE a bit longer than the light sides.

So, I measured the height of the light side and restored the heavy sides to THAT height (fronts to the same height and rears to the same height), the light sides were TOTALLY untouched (at that time) and then after putting the wheels back on, the car dropped to ~24.8" (From the ~25.5 I had it at)

My theory is that the two heavy sides were so much taller in coilover height than the light sides, they started picking up some of the weight on the light sides, in turn lifting the ride height on the light sides. This is all just what I've thought in my head, so I could be wrong, way wrong

So now the two front coilovers have just about the same fender-wheel gap when lifted in the air and about the same coilover height. The same thing goes for the rears.


The scales hadn't been used in about a month, so that could be a possibility, but when I sat in the car, the weight went were it was supposed to, so...

I also checked the part # on my two front springs and they were the same...

I could have very well had some binding in the front considering the large difference in coilover height between L/R, but I'd still like to stick to my "coilover height" theory.

Although it's a long drive, I'll be going down tomorrow to re-weigh and align.

Oh yeah, the guy that let me go to his shop and look at my corner weights, his named Ron Wood. He used to race in the SCCA for a long time as well, doing some type of rally racing in his old VW. He's still an SCCA tech and still does custom fab for people. Is there any chance you know him? He's about your age, and since you've both been in the SCCA for so damn'd long, I figured you two maybe ran into each other at one point

Howard Coleman

iTrader: (6)

hmmm

who put the springs on the coil overs? any chance you have a rear spring on the front and VV?

assuming you have equal rated front springs... you just set them so the car sits at say 25 inches at the wheel well lip. if you find that the springs are perched at unequal distance from the lower start of the adj threads you have dissimilar front springs, perhaps a rear on the front for instance.

you need to get this issue straightened out. your car should be close to undriveable.

that still doesn't answer your cross weight however. you could put any rate spring on the car and as long as it was adjusted to set the car at equal ride heights the corner weights would not change.

Ron Wood... the name rings a bell. he might have been a crew chief on a GT3 mazda i would have run against at Road Atlanta. anywhere from 83-89.. if he is the same guy he knows his craft. mention my name pls.

hc

pluto

some update with my car. So I went to the track yesterday. We were driving the short 1.7mile CW configuration (usually 3-4secs difference between CW and CCW). My best time was a 1:21:60. This means that I should be able to run 1:18 ish on CCW configuration. So far, the track record was set by LG motorsports C6 Vette at 1:11:7 (closed wheel) and I think open wheel was set by Formula Atlantic at 1:09. I do have a problem with my fuel pump. It would drop fuel pressure completely while I'm on the straight so I'm losing alot of time from the pump. I think I could get close to 1:19:00 on CW or 1:17:00 on CCW. If that's the case, I'm within 6 secs from the track record and 6 secs slower than a 600hp world challenge GT2 vette.

BTW, here's a video of the vette I mentioned.

http://www.youtube.com/watch?v=y6eP1_sNz3E