There has been a lot of talk about suspensions lately and I hope to make people understand what they are running without breaking the bank. I don't care if you are running coilovers, leaf springs, or ride height, and anyone of the number of shocks out there. There is something for everyone to learn here and understand why and what is really happening. How can you tell if your shock is working for you and not against you during your normal driving condition??? Easy test!!!

So, today's homework assignment is to learn about the shock and it's importance on a car. There is a old but still very true fact about traction, "never let a loaded tire become unloaded".
When the wheel goes up and down there is a rate in which this is happening. This rate can't be measured without a very good eye, laying on the track at the apex. Or using a fancy shock sensor and trick computer $$$$. We have done it both ways in the past and it works very well. I see a lot of times people including myself getting the cart in front of the horse and not checking the most basic thing out there.

We have all seen the slammed look of a corvette. Well it's not always done right and without any testing to make sure things are still working right. As the wheel moves up into the fender, it is called bump travel. So from ride height to full bump is what we will be your homework assignment. The reason for this homework is to see how much of the shock you are really using and how much of your "good handling" is really just a feeling in your gut. Once the shock get to the bump stop or bottoms out there is no where for the tire to go, but airborne. Never unload a loaded tire!!!

This is the assignment that I have been talking about. Take 2-4 zip-ties, brighter the color the better. Wrap them around your shock shaft. I use either a wire cutter, or a nail clipper to take off the extra end. Then pull the zip tie all the way to shock body. Then take the car out on your normal drive. DON"T run over 6X6s or anything stupid. Just drive down your twisty road, lap around the track, down the river road, or some other fun drive. Then jack the car back up and see where the zip tie ended up. Report back your findings.

Randy

 

Good post!
I can see where this is going already and hope a few people did their homework. Here's a bump for you.

 

Randy,,what suspension set-up do You like for drag racing?{stock shocks,coilovers,etc..}
Thanks

 

Good post. Getting people to THINK before throwing parts at their car is definitely good, and your customers will be happier in the end.

People assume lower and stiffer = better handling. Unless it's done RIGHT, that can actually make things worse.

 

Used to do this with mountain bike shocks to determine how much travel was being used.

San

 

and if it bottoms out, then what do you suggest ?

 

This is among the reasons why I, as much as I've wanted to for appearance reasons, have resisted the temptation to lower my C6.
I like the way it handles and rides right now and I really don't want to upset that balance.
Luckily mine seems to sit a slight bit lower right from the factory than many other stock C6s that I've encountered so it's a tolerable look.

 

Rethinking the compression rate and/or travel length I would think.

San

 

We aren't that big into the drag racing. The cars that we have had going fast have been on Bilsteins (trick valving) and QA1s. I got a report a couple weeks ago, 110 mph in the 1/8 mile from one of our cars. Not bad for some roadracers Drag guys can learn from doing this homework also.

Randy

 

Randy

 

Well guys and gals,
I have been emailed, pmed, called and even got a phone call on my cell. What is the point you are trying to make? I don't really have a good point besides it's good to know what you have and what you are working with. There is no right and wrong with learning, it just happens. The simple data that you can get from a simple test like this is 100 times more important then, "I think". Then what you do with the data is all up to you. If you think you have a problem with your setup, and don't feel like posting that is fine. There is a huge amount of smartness (is that a word) on this forum, and many things that can be learned. I would rather not put on my boots anymore this summer, it was a long winter, so no bashing or crap talking.

What made me think of doing this post? Well last weekend I moved into my new house, I got the truck and trailer unloaded, my wife's car, and a couple of my cars. Well the last thing was my old Audi (future iceracer). The car was packed down, with my little travel tool box, (75 pounds ) about 50 boxes of shotgun shells, garage tv, vcr, and a bunch of other crap. Well I was in the mood to have some fun after all the moving. I took off down a dirt road. If you average about 65-70 mph on the dirt road, you can beat the person doing 55 on the highway. So doing about 90 mph, I got into some wash boards in the middle of the turn. After I started hearing the rear shocks bottoming out. I knew it was going to get hairy. About 90 degrees to the road. Well thanks to my ninja like skills I made it out ok.

Then with the few phones calls in the past week about people swapping stock shocks that have been lowered. "The lower rear bolts have been bent" . I see your guy's great videos, but see snap over steer 9 times out of 10 it is caused by front shocks bottoming out. A couple weeks ago, I went up to BIR going into 4, there was at least 3 cars without enough shock travel in the front. And etc and etc and etc and etc.


This is for you guys, I'm not trying to sell, not trying to bash, not picking a fight, not telling you it's wrong.

Randy

 

There is a certain freeway overpass that has a pretty harsh transition joint comming off of it.
If I'm doing 70-75 my steering wheel will give a small jolt to the right.
Would this be snap oversteer ?

 

Probably more like bump steer.

 

For many different reasons, the "jolt" isn't caused by bump steer.

 

Glass Slipper is 100 percent right on this one. Bump steer is the amount of toe-change that happens during suspension travel.

It's hard to say what exactly is happening, and why the car is jumping to the one side. Do the homework and see if you shocks are bottoming out would be the first step.

Randy

 

Your idea with the zip tie is ok except the OEM shocks have COVERS!

 

It takes about 15 minutes to remove the covers.

Randy

 

C5s and C6s have a lot of scrub steer which is the distance from the center of the wheel to the centerline of the steering axis projected onto the pavement. The more scrub steer a vehicle has the more individual wheel feedback the driver will receive. The down side to scrub steer is that each wheel is more affected by input such as rain grooves or a bump or trough in the lane especially when the inputs are not balanced to both front wheels simultaneously. So when one wheel hits something it if you are not rigidly holding the steering wheel tight the wheel will change steering angle until you can correct it, this is the swerve you felt. Part of the swerve was the change in angle of the wheel due to the impact the rest of the swerve was your correction and possibly overcorrection. This steering sensitivity is the nature of a performance handling car and requires some driver adjustment to fully control. The remedy is to lock your left arm against the door and hold the wheel tight with your left hand or both hands if possible whenever you are driving in a spirited manner.

 

If the shocks are on the car? Maybe I'm missing something.
Tell us how.

 

I think you mean scrub radius, not scrub steer. Also, since both tires hit the transition joint, the net effect on the steering wheel would be zero. It is more likely that he is "jerking" the steering wheel himself as a response to the impact. In other words, when the car hits the "harsh transition joint", the vertical component of the cars' movement causes a human reaction at the steering wheel because the seat absorbs the "bump" and the relative relationship between the driver and steering wheel is changed. He might be holding the steering wheel with just one hand causing an unintended input to the steering wheel. I've had it happen to me and tested my theory by taking both hands off the steering wheel when I hit the transition...the car didn't jump to either side, just kept going straight. Problem solved, human induced error...again.