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Soft or stiff with IRS???

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Old 03-23-10, 10:51 AM
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Soft or stiff with IRS???

Im trying to figure out how I wanna set up my car suspension wise.
Using factory IRS locations. And some custom made coilover setup.
Id need a couple opinions. since I've never made a rotary really fast. Im used to how a V8 will throw its weight around.
Id like to run a 28" slick on the car. Yes, I know everybody runs a 26. But yes, a 28x10.5 will fit. with the wheel wells hammered out a bit, and the lips yanked out. It clears all around with the stock suspension I have in the car for now.
Now for the hard part. Running a softer 50-50 spring on the rear Im thinking will squat the car too much and make the tires rub.
Since I have a 28" tire. Would running a really stiff spring be ok, since I have the extra wrinkle wall to help with the tire shock on launches.

Fronts will be 90-10
Transmission will be a Gforce or Liberty (So shift squat will be much less then a conventional manual)

I just need a few opinions on how I can set this up. Im sure theres a way I can get a 28" tire to perform!
Old 03-23-10, 01:37 PM
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If you don't mind me asking, why do you think an aftermarket trans will cause less squat?
Old 03-23-10, 02:05 PM
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Originally Posted by 13B-RX3
If you don't mind me asking, why do you think an aftermarket trans will cause less squat?
Ive just noticed a lot of squat between gears on manual cars. Rather th could see a regular manual being a little smoother in and out of gears.
But Im not 100% sure. And Ive never really had a manual at the track before. Other then driving a friends 4 speed Nova.
My Mustang has a C6 in it, and my Chevy's have all been 350s and 400's.
If Im wrong, please correct me. lol
Old 03-23-10, 06:27 PM
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my car runs hks hyperD coilovers with 10k rear springs , the thoughts behind it was that i have a full slick tyre acting as the suspension, the springs can then be stiff as ****,
If i was running street radial drag slicks then i would want soft springs to allow squat as there would be too much stiffness in the tyres .

I also understand what your trying to say about boxes, as you shouldn't get the rear end unloading and bouncing between gears in a proper drag box combo, versus a street box that you have to get on an off . but really it can be just the drivers style.

So in my case still springs is the go, and with 1.30s 60ft times i cant argue with that so far, i just gotta get a real box to get it down the track, as im loosing heaps of time between gear crunches an ****
Old 03-23-10, 07:41 PM
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If you watch any of my vid's , stock tranny or the G-force, my car doesn't squat much at all. The less movement you have the better. The more you have, the more wasted energy. Yes people use stock suspension because its an "easier" way. But you'll find a happy medium with less wasted back and forth motion is the faster way to go.
Running a 28" tire will allow you to hook up more. This is not what you want, unless broken drivetrain parts is your goal.
Old 03-23-10, 09:02 PM
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caveat: i am not a drag racer.

the FD has a road racing suspension. as such it has a significant amount of built in camber gain. as the wheel goes into bump from it's normal position the shorter upper A arm pulls the top of the tire in.

ALOT.

so at launch if you have softish springs or your shocks are soft and the car squats the rear tires will gain as much as 2 degrees negative camber. while i am not qualified to speak on drag racing i have a feeling you don't want anything but zero camber in the rear. a couple degrees will unweight the inner third of the tire.

an easy way to measure your squat is to put a tie wrap in the shock rod, push it down to the upper shock body and go for a launch. check after to see how much the tie wrap was pushed up the rod.

hc
Old 03-24-10, 02:27 AM
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I see what you're saying about the trans now. So you are looking into a full clutchless?
Old 03-24-10, 09:57 AM
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Originally Posted by 13B-RX3
I see what you're saying about the trans now. So you are looking into a full clutchless?
Full or Semi. I need to look into them a bit more to figure out which would be a better choice. I guess Liberty's LSC series transmissions are great. I have a friend running one on his SBC Datsun. And he loves it. He said its even streetable. Nothing long distance. But he brings it out for drives around town a couple times a month and said its a blast, and the street driving doesnt seem to put too much wear on the trans. Then again, he's running a 5.50 gear out back, so Im assuming its revving kinds high at almost any speed. haha.
Im sticking with a 4.29. Strange is building me a 9" this spring. And if it looks anything like the rear end I put in my Mustang. Im gonna wanna frame it and put it on the wall, rather then under the car. haha!
I need to figure out the exact axle length in the next few days though. I dont wanna have to keep sending them back to get them shortened. My Mustangs axles went back once to be shortened. So I wanna get it spot on the the FC.
Old 03-24-10, 10:06 AM
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Originally Posted by ErnieT
If you watch any of my vid's , stock tranny or the G-force, my car doesn't squat much at all. The less movement you have the better. The more you have, the more wasted energy. Yes people use stock suspension because its an "easier" way. But you'll find a happy medium with less wasted back and forth motion is the faster way to go.
Running a 28" tire will allow you to hook up more. This is not what you want, unless broken drivetrain parts is your goal.
Im scared to run stock parts. It would be fun. But christ, Im sure Id set a record on breaking them. Not to mention that Im not sure how well a 20b will punch at my stock Jspec TII trans. lol.

Hookin and bookin, sir! Id be ticked if I grenaded my new rear end on one of my first passes. But Im hoping Strange can build me something that will let me transfer the power to the ground with a bit of a kick!
Old 03-24-10, 10:14 AM
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Originally Posted by beefcake
my car runs hks hyperD coilovers with 10k rear springs , the thoughts behind it was that i have a full slick tyre acting as the suspension, the springs can then be stiff as ****,
If i was running street radial drag slicks then i would want soft springs to allow squat as there would be too much stiffness in the tyres .

I also understand what your trying to say about boxes, as you shouldn't get the rear end unloading and bouncing between gears in a proper drag box combo, versus a street box that you have to get on an off . but really it can be just the drivers style.

So in my case still springs is the go, and with 1.30s 60ft times i cant argue with that so far, i just gotta get a real box to get it down the track, as im loosing heaps of time between gear crunches an ****
Yeah. Thats the reason why I dunno how great Id be able to launch on a 26" with stiff springs. That extra 2" of sidewall can reall help get ya going! My 28's on my Mustang wrinkle up more then old people skin when I take off. I mean, I really have to work it out to get them to break loose on a launch.
I can understand a lot of it being cause by driving style. I mean. I can row gears, dont get my wrong. lol. That seems to smooth out the transition a bit. But I dont think I could ever run the car out to it full potential.
Old 03-24-10, 10:15 AM
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BTW, my laptop wont let me use the multi-quote. Sorry guys. haha
Old 03-24-10, 11:34 AM
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Checkout this slo-mo of my launch on stock R1 suspension. Lots of energy bottoming out that suspension.

http://www.youtube.com/watch?v=cJM_mWAUpvQ
Old 03-24-10, 12:35 PM
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Originally Posted by zinx
Checkout this slo-mo of my launch on stock R1 suspension. Lots of energy bottoming out that suspension.

http://www.youtube.com/watch?v=cJM_mWAUpvQ
Hahahahaha! They just wouldnt stop spinning!
Old 03-24-10, 06:35 PM
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nice, is there any way you can slow mo a vid, id like to do that to a few of mine to check out my launches too
Old 03-24-10, 06:50 PM
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My car has gone a best of 1.28 60ft on 26's. I haven't found the right suspension setup just yet but i'm close. I'm hoping 1.20's~1.24's consistently this year.

My brothers FD has gone 1.46 60ft on completely stock FD suspension and ET Streets.

I run the LSC liberty and it's been flawless so far.
Old 03-25-10, 12:07 PM
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Are you using soft springs with more shock damper enzo?
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