XRAY - Model racing cars

Does lowering the roll center with the upper link in the rear suspension (Hole 1 on the shock tower up to to hole 2) change about the same amount as one hole lower on the lower A arm? I am going to test this tomorrow but want to know what others have experienced. Thanks.

If I remember correctly, it lowers the roll center about half as much as changing the lower arm.

But it affects camber gain as well. With the link being more level or even slanted downward toward the hubs, you will have less camber gain as the chassis rolls.

Are you having trouble with rear grip or just fulfilling your curiosity?

Just playing around more than anything but since I switched to a one way, I have had to much steering at the last couple of weekends. So trying to get just a bit more rear bite without taking away to much steering. I can get it close with standard adjustments springs and stuff but not quite where I want it. This seems really fast and easy to change if it works. My setup is just like Peter Robinson setup at the Reedy race. Except, 40wt AE oil with three holes open, and been playing from a diff to full oneway.

Is the camber gain going to change that drastic? With the little travel these shocks have it can't make as big a difference as the roll center can it? Thanks for your help.

Also just trying to get info for when I switch tires throughout the day each set has it's own balance front to rear. If I can fine tune it quickly, 1 or 2 laps then just a spacer adjustment that is what I am really looking for. Out track temps range from about 60 to 120 sometime throughout the day so changine tire compounds pretty regularly. Thanks again for any input.

David Mayhew
www.davidmayhewindustries.com

What type of corners and where in the corner does the rear have too little grip? On the gas, off the gas or both?

It is mainly entering the corner to the middle, off gas. On throttle it is really good so I don't want to mess that up at all. I have found myself trying to keep a little gas on to keep the thing straight.

Try changing the front arm mounts to position #4 & #5 for a little higher roll center and 1.5 degrees anti-dive. And maybe close one hole on the front shock piston as well.

The anti-dive will decrease your overall front caster to 1.5d and therefore the outer front tire will lose camber gain. If the changes above work for the rear, but you find the front starts to push anywhere from mid corner to exit, then you may have to either use 4.5d c-hubs or change the front camber link inside mount position to #2 and maybe add 1 to 2mm shims on the outside link.

Another thought is to try the rear diff in the low position to see if it will decrease the weight transfer to the front enough to keep traction in the rear while decelerating.

Will give it a try at the track tomorrow. Will post tomorrow night with some results. Thanks again.