How to fix bouncy issue at track?

wwjd15 wrote

I tracked at Buttonwillow yesterday, found that the rear was some sort of bouncy, typically at some corners like Bus Stop. How can I fix this issue? I played with Rebound and compression a bit, but didn't help. I have KW V3 BTW

Thanks in advance.

JAJ wrote

This will be tricky to diagnose, but lets give it a try:

- what does "bouncy" mean?
a. the rear of the car wallows around while you're in the corner
b. the rear of the car bounces off bumps in the road
c. the rear of the car kind of skitters sideways

a. is caused by too little rebound
b. is caused by too much compression
c. is caused by too much rebound

When it's properly adjusted, the chassis will move around on the springs more than you might be used to, but it will produce maximum grip.

Radiation Joe wrote

Here's a suggestion.

Keep your car stock until you understand why you should mod it. If you buy a double adjustable coil-over kit and don't know how to adjust it ... or explain what it's doing ... you probably had no business modding it in the first place.

UA wrote

why not offer some advice since you sound like you know this subject so well instead of bashing the guy?... At least he is tracking his modded car and getting some use out of that suspension instead of the 90% of people who buy fully adjustable coil-overs for daily driven street use.

I don't mean to sound like an @ss but you came off like one with your post so it's only fair.

Radiation Joe wrote

I know. I'm just a crotchety old man. I also sit on park benches and yell at little kids.

I have this annoyance with all the vendors out there selling people things they don't need. I'm also annoyed with the people out there gullible enough be believe they need this stuff or that it makes their car "better". How much do you want to bet that pretty much any driver would be faster in the OPs car around Buttonwillow with the stock suspension compared to it's current configuration?

elh0102 wrote

I'm no expert, but I think that is typically indicative of needing more rebound damping.

STALKER wrote

What are your settings?
Did you try softening the rebound?

JAJ wrote

This will be tricky to diagnose, but lets give it a try:

- what does "bouncy" mean?
a. the rear of the car wallows around while you're in the corner
b. the rear of the car bounces off bumps in the road
c. the rear of the car kind of skitters sideways

a. is caused by too little rebound
b. is caused by too much compression
c. is caused by too much rebound

When it's properly adjusted, the chassis will move around on the springs more than you might be used to, but it will produce maximum grip.

rldzhao wrote

Typically, the initial loss of adhesion (the bounciness) is due to having too much rebound damping. As the car starts to roll in a corner, the inner wheel droops to the ground. If you have too much rebound damping, this slows down the process, and hence you loose traction at the inner wheel.

Also, if this happens at a corner after hard braking, you may want to increase the front compression damping to reduce the amount of diving.

So at what part of the corner do you experience this? Initial turn-in, mid-corner, or exit?

Radiation Joe wrote

I know. I'm just a crotchety old man. I also sit on park benches and yell at little kids.

I have this annoyance with all the vendors out there selling people things they don't need. I'm also annoyed with the people out there gullible enough be believe they need this stuff or that it makes their car "better". How much do you want to bet that pretty much any driver would be faster in the OPs car around Buttonwillow with the stock suspension compared to it's current configuration?

Gearhead999s wrote

I just saw this and I find this pretty humourous as I have seen many guys with modded cars that are so disapointed that they are no quicker after spending tons of money on suspension stuff and they are no faster than a stock suspended car.Without having the ability to set these suspensions you might as well have old worn out stuff holding your car up off the ground or stick to the stock stuff and spend the time learning how to drive properly.

wwjd15 wrote

Why didn't you provide some solid advice before BS'ing me? Are you coming to this thread to troll?

Richbot wrote

If it's happening mid-corner to exit on accel, you could be too low in the rear, I would try increasing front rebound a little and raising the rear ride height.

Don't call people trolls when you haven't even asked the right questions. "Why is my car bouncy" is a pretty newb thing to ask.

Richbot wrote

Don't call people trolls when you haven't even asked the right questions. Your lap time in your signature is more than 2 seconds slower than a 140hp Spec Miata gets around that track. Not something I'd be bragging about with 420+bhp. An M3 with a few upgrades should be in the mid-40's, so you obviously have lots to learn. You can call me a troll all you want, but the other guys in this thread are making pretty valid points, I think, so maybe you should try learning from them instead of getting defensive?

Radiation Joe wrote

Here's a suggestion.

Keep your car stock until you understand why you should mod it. If you buy a double adjustable coil-over kit and don't know how to adjust it ... or explain what it's doing ... you probably had no business modding it in the first place.

Richbot wrote

A pull to the left on accel could be a toe problem or you may have the car "crabbing" down the track, might want to get it on an alignment rack or do a string alignment to see if you've got a thrust angle issue.

My last post on the thread which definitely is in danger of derailing if I don't shut up:

Mastek - You sound like you spend some time at the track, but you're off on a couple facts.

Spec Miatas do not weigh under 2000lbs. They weigh, at minimum, 2285 with driver. I've been on track in a Spec Miata with T2 E46 M3's and know what they're capable of (4+ seconds a lap faster even at very tight, technical tracks). A modified E92 should be much quicker than a T2 M3. The T2 lap record there is 1:52.5 and that was back in 2006 with a car that is no longer competitive. Maybe nobody has tried yet, but a 1:47 doesn't seem out of the question to me knowing what other cars can run at that track (T1 equivalent). E92 M3 3800lbs? Maybe completely stock with driver and a full tank. My heavier E90 weighed 3666 without driver with a full tank of fuel, completely stock. A modified car should be well below that. A member here is at 3500lbs with driver after a few mods and a rear seat delete. I'm not saying that power is everything, but ask any racer how to go faster around a racetrack and horsepower (power/weight, really) is the first place to look. It doesn't need tuning, it usually doesn't add weight, it doesn't cause you to go slower in one corner than another, you just shorten the time spent between corners. Horsepower isn't everything, but it's a huge, huge part of any car's lap time.

wwjd15 wrote

I had my car aligned 2 days before the track day, but you are right, I think the toe is off.

I just did some search about Infineon. I think you are talking about different layout. The layout I ran was called "Full course with Carousel CW". Here's a list of laptime who ran at the same day with me: http://www.speedventures.com/results/Default.aspx

calintexas wrote

Infineon is actually Sears Point, right? The layout you are referring to is essentially the original track?

wwjd15 wrote

I don't know. It was my first time there.