IC, 4 Link and weight

Yes I did mean roll center. Sorry about that.

Not a problem. Thanks for all your help.

Dammit Seth! Why can't I answer any questions?

Seth is right, there is an advantage to having the roll-center on the chassis instead of the rearend. Also, I rarely use anything thicker than 1/8" (.120) either. There are a few places that 3/16" is a good idea. For example, I use 3/16" plte for most of my 4-link tabs and bag mounts. And finally, it doesn't matter too much if the lower bars point slightly up or the upper bars point slighlty down. The small IC placement difference will not be felt.

Sorry Max. Lol. Its my day off.

I picked up some steel today and I got a piece of 2"x1 1/2" .120 wall that im going to use for my trans crossmember. I have brand new poly motor and trans mounts. Would it be advantageous at all to for me to use poly bushings for where the crossmember mounts to the frame or would it make no difference if i just solid mounted it with no bushing.

Since you already have a transmission bushing it won't make a big difference.

I do know that mounting the cross member with bushings, and mounting the transmission solid to the cross member creates some unnecessary stress on the cross member and transmission housing because the pivots are so wide.

Edited: 2/26/2008 12:46:03 AM by Lucky Dime

It wont make a big difference meaning mounting it with bushings will add some extra stress but not enough to worry about? In any case your saying its better to solid mount the crossmember? Also, ill be running a mildly built small block in it. The material im using should be strong enough? Im just used to using 3/16" or 1/4" for everything, so thats why I question the strength of .120 because I dont have experience using it. I would like to get away from using overkill materials though so thanks for being patient with my questions. Thank you. I appreciate your input.

On your tubing. 1.5" o.d. .120 wall, you using cold rolled, hot rolled d.o.m. or chromoli?

Everyone gets so concerned about chromoly (4130) and 1010 & 1020 (DOM) steel when it comes down to strength. The difference of tensile strength between DOM and 4130 is minimal. In fact in some applications, it is desireable to use DOM over 4130. Even plain ol' mild welded seam tubing is quite strong. The important part is using it correctly and avoiding stress risers.

Anybody that is concerned about using lighter weight material needs to read Engineer to Win by Carroll Smith, he covers a large area of material grades, welding techniques and proper use of tabs and such.

I'm not sure they even make hot rolled tubing.
For the most part I just use ERW (welded seam) tubing. I rarely use DOM, unless I can only get the tubing in DOM. And the only time I use chromoly is if I need an accurate wall thickness. I use it for bushing sleeves, inside or outside. The chromoly I use, the .120 wall stuff measures out to 1.215 and fits the bushings excellent. Whereas the rest of the tube I use measures to .115-.117 and the bushings fit a bit slop. Or I will get some that is .130 thick and then they don't fit. Thats really the only time I use it. Like Max said, its not really necessary. Mild steel will work just fine for most applications.