Travel!
 

No, I'm not talking about vacation! I'm talking about front suspension. I have some things rolling around in my noggin, but I want to get some thoughts. How much wheel travel are you all designing for in compression and rebound? In circle track racing we always went for 3 up / 3 down. However, when we measured the travel we never used that much. Well, except for some air travel but thats a bad memory! :lol: When you calculate roll angle, it's not even close. Then when you add travel for things like bumps, off camber approaches etc. you need more. So that's my question what do you design for and does anyone know from autocrossing, street and track what you are actually seeing? Let me hear it! :thumbsup: Thanks!

I'm no pro. I believe 50% of what I hear and 100% of what I do. Just through my own personal experience on the road course I like 2 up and 2 down. Not saying I'm right......just saying......

Thanks Gaetano. I know where you are coming from. I appreciate the input. Basically, I am working on the front end of the truck and am looking at clearances. I would like to get more rubber on the front than when I designed it because frankly since it has been so long there are new tires available. As with all things I am playing the trade off game. I want more rubber but I don't want to cut any more apart than absolutely necessary. Do you ever get on to the stops with 2" on the compression side? If so, is that on the street or track? Thanks again!

I dont do very much street driving but so far with what I have done it hasn't been an issue. My car is too low for stops. They have all been removed. The most recent stop I had to remove was the stop above the rear differential. When I went to the 315's in the rear I had so much more rear grip that I would hit that stop excellerating out of the corners, car would squat, and then pivot on the stop. Pretty crazy feeling.

One thing I want to add.....my feeling is that with auto cross and 200 tread wear tires you probably want 3" of compression due to the tighter turning angles. Reason being.....100 tread wear tires will hold grip better than 200. Once you hit your compression limit with a 200 tread wear tire it will want to slide.

Shocks are going to be your best friend in everything you are trying to achieve so get intimate with your shock supplier. Corner weight the car and have the shocks valved properly and at a minimum get double adjustables. In addition, find the ride height you are looking for and be sure the shock you buy is designed for that ride height. If your on a budget look into Afco's pro touring shock. They are $300 a pop. If you cant find them let me know and I will dig up the part number.

Most of the stuff you see running on this board
 

are using a 5 inch stroke coilover shock front and rear. That is by far the norm and what I had on my car.

The front suspension is complete allowing slightly more than 3" of wheel travel in both directions. I am contemplating putting a bump stop on the compression side limiting wheel travel to 2.5". If I do this, I should not have to modify the inner fender structure and limit the modification I need to do to the inner wheel well. I just don't want to be on the stops ALL the time. I also don't want to have to make it too stiff to keep off of them.

When it is closer to fully assembled, I will put it on the scales and get the corner weights. I have used AFCO products for years in circle track racing. They make nice products, but thanks for the tip.

I'm with yah Payton. I have plenty of shock travel, as I mentioned to Geatano above I'm concerned about my wheel travel and rubbing. If I can get away with 2.5" of compression wheel travel I think it will work out well. I'm just trying to decide how much to modify on the inner fender structure. The other consideration is that if I limit it to 2.5" I can also reduce the back space on the front wheels and move them out board a bit. Too many decisions! :lol:

5" stroke shock is not the norm.
5" of WHEEL travel is.

We prefer 3" compression, 2" extension from ride height.

Yep. Takes an engineer to mention motion ratio...:cheers:

(Not that anyone's wrong here. Payton used JRS which comes with 5" travel front shocks. A good choice for Camaros IMO.)

Can you educate me on this......I thought 3" of compression and 2" of extension equalled a 5" stroke.

Gae you are correct when talking stroke. However, each suspension has a motion ratio - how much the wheel travels in relation to how much the shock compresses or extends. So on my AME frame my motion ratio is 1.63 IIRC. 2" compression equals 3.26" of wheel travel. Clear as mud, right ?:yes:

Interesting.....I did not know that. Thanks Ron, glad I didn't order my new shocks yet. Looks like I have a little more homework to do. :thumbsup:

Ron is spot on. The chassis I built uses the AME IFS components. My particular setup provides 1.688" of shock travel for 3" of wheel travel. I am at the point where the truck is low enough that using all 3" of wheel compression travel will create an interference with the inner fender structure. We are going to run inner fenders so it is a challenge.

If I can dig it up Gea I have a spread sheet I wrote that will calculate your motion ratio based on dimensions you take. Although with the car sitting there move the spindle up 3" and then measure your shock travel. Divide them an that is your motion ratio.

After several hours in the garage today, I think the body saw is coming out!

No need to find that calculator. . .our spring rate calculator will tell you what your motion ratio is based on the measurements you enter. You can guess on the weights at this point since all you car about is the motion ratio:

http://www.ridetech.com/tech/spring-rate-calculator/

Thanks Chad, I get it now. So technicaly you can use a 4" stroke shock, correct?

Thanks for the calculator. Looking forward to following those steps to the letter when the time comes.

Yes sir, you are correct!

Not to confuse matters more, but this discussion only applies to independent type suspensions. When it comes to rigid axle types like most have in the rear this motion ratio does not apply when the shocks are attached to the rear end. Shock travel is essentially the same as wheel travel in this case. Although there are slight differences between bump and roll if your shock travel is equal to your wheel travel you will be covered. You may have known this Gae, but for the folks that might be reading this that are not involved in the conversation I just wanted to be clear. :thumbsup:

Yeah, I figured that. As far as my car goes (due to tight budget allocated towards my car every year) I'll hit the road course, get a feel for what I think it needs, and work on that particular issue.
For this upcoming season I'm working on getting the rear to rotate and among making my rear sway bar adjustable and the repair to the body where the rear bar attaches and has torn the sheet metal, rear shocks are going to be added to the combination. With the single adjustables I am using right now I can only adjust compression. Problem with that is the rear bounces when I adjust to a tighter setting because there is no rebound adjustment.
Thanks again for the help. :thumbsup:

Famous Confucious Tuner once said, "Rebound is Everything" :lol: :thumbsup: