wozzoom

I’m currently starting my midlife crisis and have decided to start autocrossing this summer with my 89 GTUs. The gist of my question is pretty simple: Should I delete the rear sway bar?

Currently the car is setup as follows:
KYB AGX Shocks with Racing Beat Lowering Springs
Racing Beat front and rear swaybars
DTSS eliminator bushings
Urethane Bushings all around
Front strut bar
225/50 R16 Hankook RS-3 tires mounted on the stock 16x7 rims. –Yes they fit with no rubbing!
And a couple of other mods that lock me into the STS class…

What I’m noticing with the car is that it has a severe understeer condition. Removing the AC and buying tires helped, but I can’t get the car to rotate quickly. Stabbing the throttle mid corner doesn’t kick the rear out and just makes the car understeer worse. The only thing that has helped is using more brake prior to corner entry but with an engine that has 150,000 miles on it, acceleration out of the corner isn’t what it used to be. In a nut shell I’m asking what could be done to help loosen the car up and help it turn? Would removing the rear sway bar help?

Thanks in advance.

-Jeff

wrankin

Hey Jeff,

Do you have camber plates on the front struts? You need as much negative static camber as you can get on the fronts in order to battle the loss under bump. How much negative camber do you have on the rear and do you have the adjustable camber bar that will let you dial some out?

Regarding the rear bar, removing it will help you get the power down better, but it will will also tend to exacerbate the understeer at the front. At your next autocross, try disconnecting one of the ends for just one run and see if it helps.

Good luck,

-bill

wozzoom

Hey Bill,

Coming from a street setup, this car does not have camber plates yet. I do have camber adjustment bolts for the front that I can insert and the adjustable camber bar for the rear.

So for the front, as much camber as possible. Check. What's a good number for the rear?

eage8

iTrader: (9)

it's going to be really hard to get enough camber on the front with stock style springs, even with camber plates... I'm guessing right now you have around -1* and in reality you need at least -3* of camber if not more. which will require you to move the strut a lot further in that stock springs will let you (they'll hit the strut tower)

on the rear aim for -1.5* maybe -1*

racingbeat springs are going to be too soft for serious autocrossing too. you're probably hitting the bump stops in the front during turn in which will cause pretty horrible understeer also.

a bigger front bar is going to help control some of the roll up front which will help, but definitely don't disconnect the rear, it'll just make it worse.

Here is a thread that should be helpful, this car was built to be nationally competitive in STS by a nationally competitive driver:
https://www.rx7club.com/2nd-generati...thread-871641/

wozzoom

Thanks for the tips. I have read John V's build thread. His car was a little more serious financially than mine. Maybe over the winter I can acquire a few more parts...

I was able to measure the camber on the front. With the camber adjustment bolts installed on the front struts, I was able to squeeze 1.6* of total camber out of both sides. About half of what I need... Looks like camber plates are the next step and about the only way to get to 3*. As a side note: with the Hankook RS-3 tires on the stock rims and the camber bolts installed, I was starting to rub the spring perch with the tire. I had to break out the grinder to clear everything. The rears are coming in at 1.5* so I'll leave those alone for now.

I did attach some zip-ties on the shafts of the front struts to see if I am indeed hitting the bump stop. I need to go out and toss the car around next. That would definitely explain why the car has such a bad understeer if I'm bottoming out. I do have some spring rubbers that I could insert to give the RB Springs a little boost.

eage8

iTrader: (9)

Camber plates with stock style springs won't work great. There isn't a lot of room to move the strut since the springs are large.

If you get camber plates you probably want to get some ground control coilover sleeves too so you can use universal 2.5" springs.

This will allow you to get some springs that are actually a decent stiffness too.

LargeOrangeFont

iTrader: (7)

Agreed. Absolutely keep the rear bar until you begin to feel the car getting nervous or over steering at the limit.

Save up for a GC coilover conversion kit and camber plates. Although after that purchase you are not far off from a set of coilovers, especially if you sell the suspension you already have.

Are you allowed to do full coilovers in your class? A decent entry level coilover like a BC or Stance will give you most everything you need. More tire clearance, lighter weight, stiffer springs, and camber adjustment.

wozzoom

Yes, STS class does allow full coilovers.

If anyone can chime in with current 2014 coilover vendors, that would be appreciated! Does anyone know which vendors have top plates that adjust camber AND caster?
Suspension Techniques - Camber/Caster = Yes
BC Racing - Camber only?
Stance - Camber only?

I know the AWR top plates have both camber/caster adjustment, but I'm not sure if I would prefer a package or to piece this together.

eage8

iTrader: (9)

it's pretty easy to see in pictures weather they're caster adjustable. I don't think any coilovers are that I know of except the groud-control street kit:
Ground Control - 86-92 RX-7 Super Street Kit

Stance might have a slightly offset camber adjuster which will statically add some caster, but it's hard to tell:


suspension techniques doesn't make coilovers for RX7s do they?

wozzoom

You're correct. I meant Ground Control, not Suspension Techniques. (Too many web pages open)

For reference on the camber/caster adjustments:

eage8

iTrader: (9)

Yup, there is also the option of upgrading the ground-controls with koni race inserts (instead of the koni yellows they come with) which is definitely worth it. If you stick with the single adjustable versions it's not that much more. You'd have to call them and ask them about it.

LargeOrangeFont

iTrader: (7)

Yes a full GC/Koni kit is really good, it is just more money. It is about the only setup with adjustable caster.

If you want to spend $1000 or so, BC and Stance are good for the money. It is a better investment than spending cash on a coilover conversion and camber plates for what you have.

I have BCs at the moment. The are not offset for more caster, and I took the top plates to a machine shop to elongate the slots to easily get -3 degrees of camber. It would really not be hard to just have a new top plate made with more caster built in.

wozzoom

Concerning the kits from BC and Stance: They list the spring rates as units of K? (Stance lists them as 9K/7K?) How does that compare to spring rates in lbs?

eage8

iTrader: (9)

it's in Kg/mm

just multiply it by 56 and you get lbs/in

9K/7K = 504/392

LargeOrangeFont

iTrader: (7)

The BCs come with 8k/6k which is 447/335. You can get them with 9k/7k as well.