AlkyIROC

New thread created just about the suspension changes done to the 4-link. The first few messages were pulled from the slide show thread but none of these had anything to do with the slide show comments.

Going through my 4-link software, moving the IC forward isn't recommended but I can move it down a little more. That will still put more bite in the tire and add a little squat. Turning the rear shocks another step softer may help also.

As cool as those sequence pictures look, I still wish I had video. The larger file pictures are 1024x683. I took the 4th picture in that sequence and printed it out on a full sheet of paper. I think I need to get some photo paper now. That one is good enough to frame. I put the printed one on my toolbox at work and everyone has been commenting on it

My reaction time in that sequence was .045. That street Mustang beside me was .212. I was a car length ahead of him before he even started to move. The Mustang still managed a 13.251 @ 109.14. I was across the finish line when he was just past the 1/8 mile mark.

Stephen

iTrader: (12)

Wouldn't Neutral or chassis rise, be better than squat?

Squat means the rear end is being pulled up, essentially losing weight transfer. Rise would mean that the tires are being pushed into the ground. Too much rear end rise would effectively mean less effectiveness of weight transfer, which I say Neutral or slight rise would be the most efficient.

AlkyIROC

Hmm, that's right. Normally a drag car wants squat to lessen the hit on the tires. Although I had one option to more the IC lower, I have a bunch to move it higher. At the current IC length, I've only got 4 or 5 positions below the neutral line and a whole bunch above it but they all go forward of the current length. If I put the IC too far above the neutral line it will want to wheelstand even more.

Then again you have to think about the way the suspension reacts. For every action, there's an equal reaction. With squat, the first action to happen will be the diff moving upward (body drops). The next reaction is the diff moving back down which will provide the traction to get you down the track.

If the suspension was set to antisquat, the first action would be to drive the tires into the pavement but the reaction would be to pull them back up again. You may start spinning slightly off the line if the traction decreases.

Time to go read the Doorslammers Handbook again. All suggestions for suspension are to put the IC long and low. The faster and lighter the car is, the longer and lower it goes. It's not uncommon to have the IC below ground level.

All season, my IC has been 44.6" out and 7.1" up with 89.1% anti-squat so there should have been some squat. I just finished moving it down and softened the shocks one click. It's now 43.9" out and 6.1" up with 77.4% anti-squat. The actual position hardly changed but the AS made a big jump. Just need some track time so see what it will do now.

greezemonkey

iTrader: (14)

^^^

Now theres a good reason to be good at math...so you can go Faster!! it`s all in the first 60'


what software do you use for the 4 link settings and how accurate has it been for you?

AlkyIROC

I use Performance Trends 4-link Calculator.

Enter all the measurements for the holes, tire size, ride height etc and it spits out a bunch of IC points. It also shows a desired box where Dave Morgan suggests the best settings for your car. When I first set up the 4-link, I was trying all sorts of other IC points just to see what the car would do. After all that playing, I moved the IC into the suggested box and the suspension has worked fine ever since. There's also a lot of other things that the 4-link software can't account for such as spring rate and shock settings.

The suggestion box gets positioned based on ET and weight. The faster you go and the lighter the vehicle, the more forward the box moves.

With a 101" wheelbase, the weight of the car is 42% over the back tires. The CG is over halfway towards the front. That means the CG is 59.4" forward of the diff centerline. The IC for the 4-link is now 43.9" forward of the axle centerline. The IC is lifting the car behind the CG and that's where the suggested box is positioned.

If I made a whole lot more HP and was able to run 8.50's, the suggested box only moves forward a couple more inches. If I managed to get the race weight down to 2500 pounds (and run 8.50's), the suggested box would only move forward about 8" from where I currently have it. Moving the CG forward or backward doesn't change where the suggested box is located so the best IC distance is really decided on the ET and weight. IC height will change how the car reacts as changes will move above or below the AS line.

If you don't have any IC points within the suggested box, you can change the ride height to move the chassis brackets higher or lower which will change where the IC points form. Hopefully you can get some inside the box that will be useful. A 4-link can give you hundreds of different IC points but only a small handful are useful.

AlkyIROC

I just finished following a suspension thread on YB. I may now move my IC slightly above the AS line but still keep it roughly at the same length. Apparently, moving it higher should get the tires planted sooner and hopefully reduce that wheel spin as the tires get the initial hit. It may also sky high the front wheels if it does hook up. I'll have some time from when I get home tomorrow to when I head out to the track to change the IC. I need to change all the mount points. Hopefully it won't cool off too much after the sun sets. I'd like to get at least 2 passes in tomorrow.

Time to make a new thread about suspension changes

AlkyIROC

YeeHaw! I made 3 passes tonight. The first 2, while traction was still good, I nailed the tires into the pavement and got my first sub 1.3x 60' time. First pass was 1.293 and the second was 1.295. Third pass I had some wheel spin with a 1.36.

On the first pass, I'm sure I tripped the 60' timers with the back wheels. It felt like the car never wanted to come down. When it did come down, the bounce on the front must have unloaded the rear tires again as the shift light came on. On the second pass, I did some shock settings and although the front end didn't go as high, it was a much smoother landing without unloaded the rear tires and I ran my best ET of 9.348 with no wind at all and a DA of 4564'.

I'm not sure if I should leave the IC where it is or move it up a little more and control the front end with shock settings. Pictures of the launch would help if I could see what the tires are doing on those launches.

Stephen

iTrader: (12)

See if your buddy will get down to ground level, at the starting line & film the tires of the car from there. See how the rear tires react/wrinkle/spin etc. But not just on the rear tires, but the whole car, so you can see front end lift, how far it carries the front end, etc.

Curious what a video would reveal, slowed down or frame by frame.