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I wanna jump this bitch

Posted by Rx7Kevin 
Rx7Kevin
Kevin Schmidt
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Location: Waterford, MI
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Rally Car:
Rx-7


I wanna jump this bitch
November 29, 2017 09:41AM
Long time intermittent lurker, first time thread starter - Pete always nagged me to join here and somehow the magical firewalls of work have opened and seem to have stayed open this time...

I sent John a message regarding some ideas to increase ride height for my car. Its a 2nd gen rx7 and I broke the exhaust off because its too low. I have only recently made the jump from rallyX to stage rally so its still in its own shakedown stages of the build. 2 rallies completed and plenty of learning ahead.

Anywhoo this is the bitch in question I would like to jump sometime, as you can tell in the photo she squats a lot (those are 15" long springs in the back in this photo too) so I have been playing with different spring rates and unfortunately rx7s are not supposed to be rally cars so everything to improve spring rates manages to bring the car closer to the ground.

I had an idea of lowering the front subframe 1-3" to give me more wheel well gap but this doesn't give me more true ride height as the lower control arms are still lower to the ground. Ideally I am looking at a custom setup for longer travel coilover setup for the front.

I've seen bits and pieces of alex's build through the years (is it rotary again yet?) but now photobucket is trying to touch everyone's wallets like spacey wants to touch young men.



1986 Rx7 Non Turbo
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Alex Staidle
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1978 Mazda Rx7



Re: I wanna jump this bitch
November 30, 2017 10:29AM
you need to talk with Al Dantes Jr. too.



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Robert Culbertson
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Re: I wanna jump this bitch
November 30, 2017 11:31AM
And Doug Heredos, and Matt Weaver.
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dunhamr1
Ryan Dunham
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1989 Merkur XR4Ti


Re: I wanna jump this bitch
November 30, 2017 11:46AM
And Mike Halley and Mal Swann if we're talking RX-7 people.
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Alex Staidle
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1978 Mazda Rx7



Re: I wanna jump this bitch
November 30, 2017 12:01PM
Quote
Robert Culbertson
And Doug Heredos, and Matt Weaver.

The second generation cars are nothing like the first generation cars.



Respecognize!
Http://www.facebook.com/2WDriveRally
First Rally: 2010 First RallyX: 2004 (a bunch)
Driver (0), Co-Driver (5)
Organizer (3), Volunteer (3)
Cars Built (1.5), Engines Blown (2) Cages Built (0) # of rotations (3.5)
Last Updated, Oct 30, 2013
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Robert Culbertson
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Re: I wanna jump this bitch
November 30, 2017 01:07PM
For some reason I though Matt had a 2nd gen, but I haz the dumbz.

OP: what spring RATES are you using in the rear, and front?
What type of struts and shocks?
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Pete
Pete Remner
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Re: I wanna jump this bitch
November 30, 2017 04:41PM
One thing I found is that ball joint lock in the front is a very real issue once you get more droop travel than stock. So I am probably going to shove an FB snoot back under it.

Actually, that's a lie. I'll probably sell the car or something. I have a much nicer '81 (Charles Wright's old car) and I accidentally bought a twin dizzy RX-3 that is screaming to have the Group 4 Escort manual translated to Japanese.



Pete Remner
Cleveland, Ohio

1984 RX-7 (rallycross thing)
1978
Silence is golden, but duct tape is silver.



Edited 2 time(s). Last edit at 11/30/2017 06:27PM by Pete.
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Rx7Kevin
Kevin Schmidt
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Re: I wanna jump this bitch
December 01, 2017 10:56AM
Quote
Gravity Fed
you need to talk with Al Dantes Jr. too.

I did a bit, he has off the shelf tokickos in the back with some 14" long 2.5" id spring and the front has a coilover setup but I'm not exactly sure the details on that - he had said it came with the car.

Quote
Robert Culbertson

OP: what spring RATES are you using in the rear, and front?
What type of struts and shocks?

The rear I have bilstein B6 HDs and in the photo shown its a stock rx7 convertible spring which is a 15" long spring @ 90 lb/in with. I have tried an RS*R spring but its a 13" long shock but 224 lb/inch and it felt much better however too low which caused me to break the exhaust at summer sno*drift. In the mail I have a 16" long spring to try with 225 lb/inch for the rear. Al runs 250lb/ inch and thinks its too stiff I like the feel of the 224s but the ride height suffered too much

Front is also bilstein B6 Hds but they are inserts to the stock shock housing. I have 135 lb/inch springs there with again about a 1" drop.


Ideally I want some more ride height and travel I think I am close on my spring rates as soon as you step on the gas on these cars they squat like crazy and with a low car going even lower it just drags its ass through the dirt which is fine on smooth rally roads but that almost never happens, especially with only running a few rallies I am the back 1/3 start order.

Quote
Pete
One thing I found is that ball joint lock in the front is a very real issue once you get more droop travel than stock. So I am probably going to shove an FB snoot back under it.

Actually, that's a lie. I'll probably sell the car or something. I have a much nicer '81 (Charles Wright's old car) and I accidentally bought a twin dizzy RX-3 that is screaming to have the Group 4 Escort manual translated to Japanese.



Also, when did you grab that and why didn't you tell me!



1986 Rx7 Non Turbo



Edited 1 time(s). Last edit at 12/01/2017 10:58AM by Rx7Kevin.
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Robert Culbertson
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Re: I wanna jump this bitch
December 01, 2017 11:45AM
Them be some SOFT springs in the rear. Like softer than a stock Volvo 240, or a mk2 golf.
Gotta get something stiffer out back, and up front. Either the stiffer coils you already used with a spacer (for more height), or go to a 2.5in diameter coil-spring. Lots and lots of options for springs and lengths.

Quick googling for a the motion ratios of the suspension gives ~ 1:1 for the front and 0.9:1 for the rear.

Shoot for a wheel rate of around 150-200 lbs/in in the rear and a WR of 225-250 in the front. You probably want to be on the lighter end of that scale.
Our Volvo 242 has a rear wheel rate of 165 lbs/in, and have gone up to a wheel rate of 225 lbs/in... but that was pretty stiff. The front is 225 lbs/in.

So using a MR=0.9 for the rear, and :
Wheel Rate= MR^2 * K
Work that around to find the spring rate needed fora given wheel rate:
K=WR/(MR^2)

Plop in a wheel rate of 175 lbs/in and you'll get a spring rate of 250 lbs/in.
WR of 150 lbs/in gets you a spring rate of 216. So the 225 lb/in springs you ordered should be just about bueno.
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Pete
Pete Remner
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Re: I wanna jump this bitch
December 01, 2017 05:10PM
Quote
Robert Culbertson
Shoot for a wheel rate of around 150-200 lbs/in in the rear and a WR of 225-250 in the front. You probably want to be on the lighter end of that scale.

That's actually what I found had the best handling for the FB. I did eventually go softer for more ultimate grip but handling got sacrificed a bit.



Pete Remner
Cleveland, Ohio

1984 RX-7 (rallycross thing)
1978
Silence is golden, but duct tape is silver.
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Pete
Pete Remner
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Re: I wanna jump this bitch
December 01, 2017 06:59PM
Quote
Rx7Kevin
Also, when did you grab that and why didn't you tell me!

A, I got it next weekend.
B, because reasons
C, added difficulty is that I don't yet have a trailer hitch on the R so I can't tow it home so I need to bum someone else's assistance. (I know you know about the R. It's completely numb but also ridiculously fast in a "I didn't realize I was actually accelerating/braking/cornering this hard" video game kind of way)
D, recognize that it has literally sat in a barn since 1979, and if it doesn't have floors under the carpet, I'll sell off the trim pieces and scrap the rest, but I am *hoping* that the shell is decently solid enough that years of reading the "Windy's New Project" thread and other stuffs will motivate me to do something cool. As a bonus, Evan got a really sweet Kadett and I'm hoping to go in with him on various fab/restoration stuffs. Not sure if his city would be keen on my idea of a swimming pool full of Evaporust, though.



Pete Remner
Cleveland, Ohio

1984 RX-7 (rallycross thing)
1978
Silence is golden, but duct tape is silver.



Edited 2 time(s). Last edit at 12/01/2017 07:05PM by Pete.
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Doivi Clarkinen
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Re: I wanna jump this bitch
December 06, 2017 02:06PM
Or maybe talk to the guy who built the most successful and most developed 2nd Gen RX-7 in the country. (Me. smiling smiley ) 2002 SCCA Group 5 national champion. There's lots of things that need to be done to these that you aren't even thinking about.
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Rx7Kevin
Kevin Schmidt
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Location: Waterford, MI
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Rx-7


Re: I wanna jump this bitch
December 08, 2017 10:41AM
I would love to pick you brain, did you end up selling that car? I think I may have seen it at LSPR several years back when they raced up copper harbor area.



1986 Rx7 Non Turbo
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Doivi Clarkinen
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Re: I wanna jump this bitch
December 10, 2017 12:24AM
Quote
Rx7Kevin
I would love to pick you brain, did you end up selling that car? I think I may have seen it at LSPR several years back when they raced up copper harbor area.

Just to clarify, it wasn't my car. I built an maintained it for Dave Hintz. It's changed hands a couple of times since then but still lives in the Seattle area. Current owner only takes it out infrequently but it still has the same engine that was rebuilt in 1999 just before becoming a rally car. It's never been to Michigan but it did run in Minnesota 2 or 3 times and once at STPR in 2002.
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