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85 RX-7 ride height for track?

Old 03-01-10, 08:50 PM
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85 RX-7 ride height for track?

So I'm building a 1985 RX-7 track rat and I'm trying to figure out what is a good performance ride height for it.

I have a Ground Control Coilover setup in front and eibach springs in the back I can cut (several dead coils). I don't have a trilink or panhard set up.

The car has not been lowered so it's pretty much at a stock height now.

the question is: what is a good ride height that lowers the car while still maintaining good suspension movement? AND where do I measure ride height from?

any help from PRO7, ITA7 or track gurus appreciated.

ps. car will be used in fairly fast tracks (Infenion raceway, Laguna Seca, Thunderhill)

thx.
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Old 03-01-10, 09:34 PM
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My car will sit with 3 1/2" of ground clearance measured from the ground to the lowest part of the rocker (as per rule book) directly aft of the front wheel.

I run modified shocks in all corners and tuck about 1" of rubber in the well.

On my home track, the car is rarely under 70mph through the corners and don't rub or bottom out the susp. or frame on the sometimes bumpy track!
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Old 03-01-10, 09:57 PM
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I'd be more worried about the roll center crossing the ground plane. And on a car with struts that's usually shortly after the lower control arms go past horizontal (pointed up towards the wheels). I've never looked at an FB that closely though, so I'm just speaking generally.
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Old 03-01-10, 11:18 PM
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I'd usually look at around 4-5 inches to the bottom of the frame rail. Remember also that with the McP struts up front you can run the problem of significant camber loss under bump if you lower it too much.

IIRC, there is also an issue with binding in the rear suspension when you lower it w/o modification. Some of the FB gus can chime in here.

Good luck,

-b
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Old 03-02-10, 12:49 AM
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Billy from Respeed has many years of experience in putting these cars on the track. You can either send him a PM (Bwaits_), or find him on his forum over at www.re-speed.com

He will have the facts for you.



.
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Old 03-02-10, 09:29 AM
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I used to race IT7, so I will share my experiences. You should go to where your lower control arm is level with the ground from pivot to pivot. This would be the spot where travel will have the least effect on geometry. I ran 5 inches to the rocker panel, lowest you can go in IT. Then leveled the arm with the appropriate spacer. Fix the back with the correct length spring so your rake is not jacked up and then balance the car our with spring rates. I used 450 front and 200 rear and no rear bar. This is using a panhard bar, no bushings in the upper trailing arms. If using the stock watts link setup I believe the upper trailing arms will limit you by binding well before you get that low.
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