Rx_treme

Sup yall,

I just got some new goodies put on and took her to the track. I noticed the rear was a bit bouncy, well actually this whole particular lot was really bumpy but it seemed to bounce the rear around more than normal. Its not something that i really noticed in the car until someone pointed it out.

Lots of other things but these are the important variables.

Tires;
275/40/17 kumho V710 all around

Spring setup;
GC Coilovers w/ 450 front, 325 rear
Tokico Illuminas, front was set at 3/5 and rear 5/5.

Alignment;
front- 1/16" toe out, -1.5 camber, 4 caster
rear- 0 toe, -1.5 camber, zero thrust
Maxed out b/c of height required for tires.

Car was really pretty neutral overall. just need some more seat time.
Any suggestions??

Thanks
Jason

Video= http://idahorotary.com/autox1.wmv

jeremy

iTrader: (1)

wow, your car sits high. the only thing i could think of is that you think you have 5/5 selected but its actually 1/5 on the rear. i couldn't see you having anywhere near that kind of bounce with the shocks set to full stiff unless they were blown.

DamonB

If the rear is bouncy the first thing you do is soften the rear shocks. When the shock is too stiff the tires will "patter" over the bumps because it's overdamped; the wheel doesn't get a chance to ride over the bumps and instead bounces over them.

I can't tell without being in the car what the shocks are doing but the first thing you do when one end of the car doesn't work is soften that end.

Why are you running with so much rear shock?

If you've never tried the car with any toe in on the rear I would give that a try too.

reza

When I was running Tokico, I set the front to 5/5 and rear to 3/5. Try that setting. Depending on surface, you may want to drop the rear to 2/5...

jeremy

iTrader: (1)

i always thought a stiffer setting on the shock would tend to make the rear end skip, etc. his was bouncing like the shock wasn't set hard enough to stop the heavier spring rate. maybe i'm just way off base.

DamonB

If the shock is not stiff enough for the spring the car will oscillate which that car is not doing; that car doesn't have enough compliance in it for the bumps. If the shock is too stiff for the track the suspension will never get to conform to the bumps and so tire grip suffers.

Springs are displacement sensitive: The farther you push them the stiffer they get. How fast you push them doesn't matter.

Shocks are velocity sensitive: The faster you push them the stiffer they get. How far you push them doesn't matter.

A stiff shock can be great on a smooth surface but once the surface gets bumpy you must soften the shocks, otherwise they will not let the spring settle the tire back to the surface quickly enough. The rear end of the car in the vid looks overdamped for that surface: Too much rear shock.

Rx_treme

ahhh, thanks Damon that sounds exactly like it felt on the track.

So too much strut, I'll try 5/5 front and 3/5 rear next time however it'll be on a smoother track.

Jeremy the only reason it sits that high is for the tire clearance i need. couldnt find any smaller diameter tires that were that wide.

Thanks,
Jas

rhinor61

My question why are you running 17" wheels and tires? I would think a 14" or 15" would be less weight for the rim+tire , faster accelleration and it would let you lower your car to ground. Being lower to the ground would decrease the body roll that appears you are getting. Springs and shocks can only do so much. I would study other cars in your region and see what the veterans are doing to go fast.

Big rims look great, which also makes you slower around so everybody will get a good look at you.

John

reza

The minimum rim diameter for FD is 16inch. I think it is because of the brake caliper position.
Unless you go with 14/15" mexican style, 0 offset

rhinor61

Yea I though about the brake clearance as issue after I posted it. I honestly recommend the smallest diameter wheel that will clear the brake calipers.

John

89rx7gtu

yeh, it does seem like it sits high.