I have a '96 JDM R with the '98 5 Lug suspension and some Tein Hyperflex coilovers.
I'm running some 15 x 6.5 Spoon wheels with some 205 50 15 Dunlop Direzza 101 something (A common street tire here). I had some bad bushings in the front lca's so I replaced all the bushings in front with the energy suspension bits.

I recently started pushing my car a bit in some twisting mountain roads we have. What I realize is that the back of the car breaks loose quite easily with minor weight transfer changes.

In comparison to my buddy's DC5R w/some JIC coilovers and OEM DC5R wheels, on the same roads and same speeds, my car is way less stable.

I'm going back to the OEM 16 x 7 wheels and a new brand of tire. What I want to know is, what can I do or add to get a little more rear traction?

 

What spring rates are you using? Are you on the OEM JDM sway bars?

My instincts tell me that it's not your wheels and tyres that are causing the behaviour you are noticing. My instincts tell me (forgive me, but I've been here a long time) that it is the car's basic proclivities and the driver's capabilities that are causing this behaviour.

 

10F and 7R kg is the advertised spring rate. OEM JDM sway bars.
I definitely need more practice, but something still seems off.

 

The springs are a little light for aggressive driving.

Although your spring rates are designed to promote understeer, the light weight of the springs will cause a greater perceived and quicker overall weight transfer onto the nose when you lift.

This will cause a more radical swing than the one you might want.

When it became clear that I would be going into threshold braking from 135 - 140 mph, we went with 14K on the nose to slow down the nose dive, and 16K on the rear to make sure I could still rotate when I wanted.

I'm not saying you should necessarily have those weights on a street car, but I think you should spend more time w/the car before you decide that you want more understeer.

No insult intended at all...but after you learn more you are going to want less understeer and what you are calling "less grip" on the rear will eventually be a source of joy for you.

Spend more time w/the car. Think about signing up for Track Daze, or NASA events in your area.

And stop doing dumb stuff on public roads, of course. :-)

 

I'm sorry. I just noticed you were in Trinidad. I don't even know if you HAVE a track on Trinidad.

 

George hits the nail on this one. OP, your desire for more understeer is seem to goes against the logic. However, I can understand that bad habit is hard to break. So, loose up the rear suspension a bit more such as decrease the spring rate or change the JDM sway bar for an USDM bar or even a GSR bar. Tests and tries will let you dial it in. Good luck and please use commom sense when you out there in the twisties.

 

Thanks for the advice! I guess since I'm accustomed using the car for daily duty, I never realized my limits.
Unfortunately, our only circuit closed 2 years ago. I drive up to the hills twice a week to try to learn the car. Wish I had a proper circuit and an instructor though.

 

I agree with the above. If all four of your tires are the same make/model, size, and tread depth, then it's not your tires causing the problem. I think George hit the nail on the head. Even with a FWD car like ours, whose basic tendency is towards understeer (although the ITR is perhaps the most neutral FWD car out there), your driving can cause the back end to swing around on you. When you lift on the throttle (or step on the brakes), the weight transfers to the front of the car; when you do so in a turn, the unweighted rear end can swing around on you. They call it "lift throttle oversteer".

Fly to the ITR Expo. Even if you don't have a car there, you can probably catch a ride with an instructor, and learn from it.

 

Camber? Toe?
These two settings can affect the rear stability a lot.

Another wild guess would be to check your rear breaks. If they brakes are a little seized, they will drag your rear wheels all the time just like you holding on to the handbrake.
Just something worth checking since the car is so old.

Cheers

 

I'm surprised no one mentioned replacing the rest of the busings in the back of the car (first, since you've already upgraded the fronts), and then trying adjusting the tire pressures (2-3 psi less in the back than in the front, check the door jamb or manual).

Are those shock's damping adjustable?
Have you tried different settings (front vs. rear) to help out your situation.

It's always best to fix the "broken" or unfinished stuff first and then try any available "adjustments" before just going and replacing components. JMHO

 

beat, I'll go check alignment again. Brakes are good but the car did come with a 34/40 proportioning valve though (non-ABS ITR)

Zygspeed, I only changed the front bushings cause some were damaged but I guess I'll change the rears as well.
And yes, the shocks are adjustable as well. Although it hops on bumpy road, it feels better with equally high rebound rates. Softer rear settings give a lot of roll.

Expo? Hmm...

 

i actually have rear end hopping in real tight corners, i like it this way because i can tell when it wants to break loose and i can let off. if you learn your car better you can actually get better turn in and alot more rotation then with a car that under steers.

play with the car a lil more and try to be smooth. i know the itr in stock form is very tossable, you have upgraded shocks and springs so the *** might be a lil bouncy.

also inspect your rear trailing arm bushing cuz a torn one will give you a loose rear feeling

 

Mine was the same with the rear kicking out slightly but after playing with the spring rates for the rear that problem definitely went away

 

Good info!
Nice to hear some technical advice from some of the more experienced guys on the board!!

 

This the mountain road I'm trying to learn. My partner with the DC5R in the back, passenger was using a N95, no sound.
http://www.youtube.com/watch?v=eBU5ArqIR1M

It's long so kinda hard to memorize all the turns. I'll try to get a recorded run with better camera in the day sometime.

P.S. I think I have a busted rear trailing arm bushing.