First Gen RX7 Rear Suspension Setup

Z

zoom63

Member
Hello all,

I know the 79-85 rx7's are old technology, but I am seeking some wisdom on the suspension set-ups that make so many of them fast. A couple of questions that I have:

Is there anyway to get rear camber?

Tokico shocks the way to go?

Rear spring rates on a 2250lb car??

Differential modifications?

Anything done to the brakes in the rear to keep them from "laying over" in corners?

I am just searching for some schooling on the suspension and rear setup. It seems first gen cars are at a big disadvantage to Miatas with the rear camber issue.

Any help would be greatly appreciated!

Thanks a lot,

Steven
 
Steven,
The clutch type diff that's in these is pretty good. There are also Torsens (same guts as a Miata I've been told) and many gear ratios available. I have everything from a 4.1 to a 5.10 in the garage, but I don't know what type of diff they're bolted into.

Since the rear is a solid axle on the 1st gen, camber isn't as much of an issue as a car with independent suspension that has to counteract body roll in corners. The goal is to keep the solid axle planted on the ground regardless of body roll.

I have no idea what the spring rates are on my car- haven't looked at them since I bought it..
 
Matt93SE":1pw66yja said:
Steven,
The clutch type diff that's in these is pretty good. There are also Torsens (same guts as a Miata I've been told) and many gear ratios available. I have everything from a 4.1 to a 5.10 in the garage, but I don't know what type of diff they're bolted into.

Since the rear is a solid axle on the 1st gen, camber isn't as much of an issue as a car with independent suspension that has to counteract body roll in corners. The goal is to keep the solid axle planted on the ground regardless of body roll.

I have no idea what the spring rates are on my car- haven't looked at them since I bought it..
Click to expand...


Thanks Matt!

I am guessing the shocks make a great deal of difference. I am currently using 175# rear springs and 275# front springs with stock shocks, and I think that may be my issue. I think we need to get the Tokicos!
 
I know the springs on mine are way stiffer than that.

Here's some good info on an old thread I found while Googling..
http://www.improvedtouring.com/forums/s ... What-rates

In the spares that came with my car were 2-3 sets of Bluecoil springs.. Mine was a "Tom Thrash build" as the car was owned by a good friend of his who mimicked anything Tom put on his car that made him faster. It's currently got Advance Design shocks on it, but I just picked up a set of JRZs in case these ADs are toast. Car has been sitting since 2009 so the shocks at minimum need a nitrogen recharge..
 
On the RX7 my customer runs in Vintage, we are running a 3link setup on the rear with 500lb rear springs and it really needs more. I would skip the street car shocks all together and get either some Koni Sports or get Bilsteins and have them revalved for race spring rates. You could do a coil over arrangement as well , but you will need to reinforce the lower shock mounts on the axle.

As to rear camber we run .5deg negative. Any more using the stock housing and axle shafts will destroy bearings in short order. We haven't been able to find a company to cut us crowned axles in the Mazda spline pattern.

The rear diff, either get a MAzda motorsports diff or find a street LSD and have Steve Eckrich re-grind the ramps and restack it. You will probably want at least the 4.88 if not the 5.13 depending on the tire you are going to be using and the transmission. We are running a G-force trans (overkill but we haven't broken it like the Mazda Comp box).

Don't waste your time with the Tokico shocks, they are junk for race cars. We ran those for ten years because the owner thought they were "good enough". Ask him about them now that I built him some housings to use the Koni insert and the answer will be much different.

There was a fellow selling a lot of components for the first gen cars, but he has since retired and moved to Central or South America.
 
zoom63":33cavgyc said:
Hello all,

I know the 79-85 rx7's are old technology, but I am seeking some wisdom on the suspension set-ups that make so many of them fast. A couple of questions that I have:

A. Is there anyway to get rear camber?

B. Tokico shocks the way to go?

C. Rear spring rates on a 2250lb car??

D. Differential modifications?

Anything done to the brakes in the rear to keep them from "laying over" in corners?

I am just searching for some schooling on the suspension and rear setup. It seems first gen cars are at a big disadvantage to Miatas with the rear camber issue.

Any help would be greatly appreciated!

Thanks a lot,

Steven
Click to expand...

I built a 1985 RX7 for ITA. Used G-Force and ISC Racing suspension stuff. Car is long gone, don't ask.

Point A. Yes per G-force, 1* max. Weld length wise on one side of the axle tube.

Point B. ISC modifyed the front struts for some brand of insert, don't remember the brand.

Point C. You have one to many digits in your spring rate number. Adjustable spring perches all around.

Point D. Yes, GSL limited slip or Torsen, 4:88 or 5:12 depending tires and track.

Adjustable camber plates for the front. G-Force turn in spacers for the front. Be careful matching G-Force turn in spacres to your part, the G-Force dimensions were wrong. Long story. Install a strut bar at the front. Tubular front sway bar with alum arms. Third link, eliminating the upper OEM links function (you may desire to keep the upper links with very soft bushing material for safety reasons). Adjustable rear Panhard bar. Front brake ducts.

If any interest I'll sell my G-Force Engineering 1st gen RX7 suspension, setup and tuning note book, interesting stuff to learn/use. It was written for ITA, but has many crossover to E production comments.

Contact Jesse Prather thru pm, also look in the for sale section under "remsport" Rich Miller in MI bought Jesse's 1979 1st gen RX7, he has been selling off his 1st gen RX7 stuff. Rich
NEW EMAIL >>> remiller35 at ATT dot net

EDIT;
Another guy selling his 1st gen stuff.
John McNaughton
GNAUGHTONJ@AOL.COM
843 810-1199
License # 39946
 
What about the differential? What are people talking about when the weld theirs? I am ignorant with some of this stuff! Where do you weld it and what is the purpose?

Thanks again!
 
Welding a stock/open diff is the cheap way to get a locker or "spool". the simplest way to do it is to weld the spider gears together. both axles are effectively locked together and alwyas spin at the same rate.
This is what most of the drifters do. car pretty much exits the corner sideways, but it's predictable all the time.

It's better than an open differential, but a clutch type or Torsen is preferred.
 
David was talking about laying a bead down the outside top of the axle tube to shrink it to add camber. OR you can use the old circle track method of heating the tube about where the spring shackles connect and give it a hit on the top with a four pound hammer. I ran my car with big front bar and none on the rear. Heavy front springs 600ish and maybe 100-200 in the rear. The car was pitch and catch. I ran adjustable bars for the watts link and relieved the right side bracket to allow that side to drop as much as the left side. One of the problems with the stock setup is the binding of the suspension on the right rear under load.

James -r
 
Hey Matt,

Do you have the specs on your cars spring rates? If I could match a Tom Thrash car, that would be sweet! I appreciate all of your info.

Thanks again!
 
James Rogerson":1brxpddc said:
David was talking about laying a bead down the outside top of the axle tube to shrink it to add camber. OR you can use the old circle track method of heating the tube about where the spring shackles connect and give it a hit on the top with a four pound hammer. I ran my car with big front bar and none on the rear. Heavy front springs 600ish and maybe 100-200 in the rear. The car was pitch and catch. I ran adjustable bars for the watts link and relieved the right side bracket to allow that side to drop as much as the left side. One of the problems with the stock setup is the binding of the suspension on the right rear under load.

James -r
Click to expand...

Thanks James!
 
I forgot about the other welding stuff mentioned. Remembered you were asking about different types of diffs- clutch, torsen, etc., and thought you were asking about welding the guts of a stock differential, not welding the housing to get camber.

In regards to my spring rates, I'd have to jack the car up and look at it, and unfrotuantely that's not going to happen for a few weeks. I have a race this weekend with the other car and the RX7 is buried in the garage. It will take a couple hours of cleaning just so I can get a jack under the car.

I wish I had a setup book or something with the car. I bought it from the second owner. First owner/builder said it went with the car; second owner said he never got it. So I've got a huge learning curve when I try to finish it up.
 
zoom63":3rhlpzdi said:
If I could match a Tom Thrash car, that would be sweet!
Click to expand...

In the Aug 2009 issue of SportsCar Tom Trash shared his setup:

Double adjustable Konis front and rear, with 500lb front and 180lb rear.
 
Steven, from your descriptions and comments I would suggest that you leave the welding and rear camber efforts to a lower priority.

All the other items, spring rates, good shocks that are matched to your spring rate, adjustable rear spring seats, coil over conversion in the front. Only use a larger, front swaybar - no rear bar. Add a stock RX7 positraction unit that someone with experience has set up for you.

It will "as a package" be a significant improvement to your handling. All of those are bolt on items, you will be pleased with the results. Have someone do a good 4 wheel alignment for you after you have installed all the parts.

Could you explain one of your comments? I don't understand your brakes "laying over"?
"Anything done to the brakes in the rear to keep them from "laying over" in corners?"
 
JohnMcNaughton":25jajv98 said:
Steven, from your descriptions and comments I would suggest that you leave the welding and rear camber efforts to a lower priority.

All the other items, spring rates, good shocks that are matched to your spring rate, adjustable rear spring seats, coil over conversion in the front. Only use a larger, front swaybar - no rear bar. Add a stock RX7 positraction unit that someone with experience has set up for you.

It will "as a package" be a significant improvement to your handling. All of those are bolt on items, you will be pleased with the results. Have someone do a good 4 wheel alignment for you after you have installed all the parts.

Could you explain one of your comments? I don't understand your brakes "laying over"?
"Anything done to the brakes in the rear to keep them from "laying over" in corners?"
Click to expand...

Thanks John!

Upon further inspection, you can ignore that comment!! We had an axle washer crack and the whole thing was moving about a 1/2" and pushing the rotor into the caliper. It is fixed now! I saw you had some transmission parts for sale at one point, do you have a rx7 box with Miata gears?

Thanks again!
 
Jason@SportsCar":1mbmtuj5 said:
zoom63":1mbmtuj5 said:
If I could match a Tom Thrash car, that would be sweet!
Click to expand...

In the Aug 2009 issue of SportsCar Tom Trash shared his setup:

Double adjustable Konis front and rear, with 500lb front and 180lb rear.
Click to expand...


Thanks a lot for the info!!
 
I have several first gen RX7 transmissions and one low milage Miata transmission. Would you like to buy one of each? You can then do the conversion yourself. It's not too difficult. Or, convert your transmission over.
 
John, the biggie for the conversion is re-machining the input shaft, correct. I have the change dimensions if anyone needs which I received directly from Dave Lemon. Or the dimensions were on the MazdaTrix site at one time.
 
It is pretty much a bolt in process. Remove all the internals from the RX7 case and install the Miata internals. The internal bearings, shafts and dimensions are identical.

You will need to retain the stock RX7 bellhousing and transmission cases.

The machine work needed:
1. The input shaft from the Miata needs to be shortened 1/4". That can be done with a hand grinder and finished off with a file and sandpaper. Or, have the input shaft machined.
2. Verify that the Miata clutch splines are the same length as those on the RX7. The Miata sometimes has longer splines, simply remove as needed, and taper the leading edge of the splines.

If you don't feel comfortable with doing the conversion, a competent transmission shop can do it.
 
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