Setup

[Truck38]

This weekend at THR (before the rain) there was a disagreement on the best way to correct an understeer exiting the turn. I wanted to change a spring, but my team felt like more rollout would be best. I know both would probably have worked but I'm curious from all the more experienced setup people as to which would have been the better option? Or is there another I should consider... I know what I would have done I just wanted to know which would be better.

 

It was a tad tight in the center but as soon as I picked up the throttle it wouldn't turn.

 

Cameron

[Truck99]

How much stagger did you have when the problem was present?

[SSCHUCK]

You have to consider springs on all four corners and what stagger you are running just to start.

You still have alot of other suspension adjustments as well.

[NickHolt]

Without known intimate details about your truck, it's pretty much a crap shoot giving suspension advice.

 

But I will tell you this. That "slight push" in the center of a turn has to go, especially in turn 1-2 at THR.

 

THR calls for about 2.5 inches of rear tire stagger. Much more or much less is simply a crutch. So I will assume you already have the correct rear tire stagger.

 

There are many ways to get rid of a push in the middle, but I prefer using the panhard bar if the push is not induced by either braking or acceleration - that is, the truck wants to push while "rolling" through the middle of the turn. In this case I would raise the rear panhard bar until the truck is easily able to turn in the middle of the turn.

 

If the truck is pushing going into a turn, usually that's due to some sort of bind in the suspension or too much RF spring/sway bar rate.

 

If the truck is neutral going in but has a slight push in the center and you don't have a panhard bar to adjust (four link set ups and leaf spring rears), I'd consider removing a bit of cross weight percentage, opening the rear stagger a bit, removing some sway bar pre-load, raising the RF spring rate, increasing the roll steer in the toe out direction, increasing the Ackerman (I run zero Ackerman and prefer to use roll steer). Of course, you could also increase the rebound on the LF shock and/or decrease the compression on the RF shock.

 

Of course, static toe, camber angles, ackerman and a dozen, or more, other parameters come into play here, but those should already be right before you make other weight/spring/shock changes.

 

Hope this helps.

 

Nick

[Truck38]

The last THR race, I was very very very happy with the truck. I could drive it in hard and it was just a tad loose off which I like anyway.

 

BUT I discovered at the dirt track that I had a bent RR axle which explained a lot because the last THR race I had to change springs just to keep it from coming around. Now that I have a new axle and the push off the turn I want to put the spring I had in there before but everyone else wanted to change the stagger. We fixed the slight push in the center by loosening the sway bar, but as soon as I would get into the trottle it would chatter the RF. My thinking is there isn't enough weight on it.

 

Maybe I'm wrong but if I put a heavier RR spring in that would keep more weight up front and also take some off the back = turn more. BUT more stagger = more turn.

 

Everything else you mentioned Nick is right on or really close.

[Crazyhorse]

close up the front a 1/4 or take a round out of the bar. if that works a little ,go a little more....these trucks don't have panhards , and they are usally so front heavy that by doing anything to the rear doesnt help even in exit all it will do is free the ass up then you are chasing two problems. unless it is something drastically wrong i would not change a spring

 

-edit- i didn't see your last post cameron.

[Truck38]

It is all good, I guess I'll go with the stagger and see what that'll do.

 

Cameron