Alright, I have a 2wd st truck. If I lock the diff it is said that it wont turn good. Well riddle me this. The perpose of caster is to lift one of the rear wheels while cornering. So if it is not on the ground who cares if it is spinning in the air.

So lets say I locked up the rear diff. It will turn horribly durring acceleration correct? Well I dont race so if I need to turn I can just let off the throttle. right?

I know that my go kart has a straight axle. when I turn left the left rear tire has nearly no weight on it. Becasue of the caster in the front wheels. So why cant my rc car do the same.

Im not really sure why you think front caster is there to lift a rear tire in the turns. Thats just not true. You get some chassis roll in the turns and the caster is there to maintain a full tire contact with the ground for traction. If your getting enough side bite that the inside rear tire is lifting off the ground in turns you need to use stiffer springs/oil in the shocks.
A locked diff/spool is really for Monster trucks for climbing. This way when they are climbing over rocks etc and the axle gets to extreme angles you still get traction even if a tire loses contact. This stops the tire from "diffing out".
In a ST a spool will cause 1 of 2 things (or both) to happen. If the rear has good traction the truck will push. If traction is poor the rear will break loose and hook out. Somtimes it will push up until the point it cant get traction and then suddenly hook out. Not a good thing for a ST.

You guys are a little mixed up with your terms i think.

Caster is that angle of the steering pivot relative to the ground, looked at from the side of the car. When the car is moving forward, the wheels want to follow the steering pivot (like in a shopping cart wheel) This creates straight line stability. It also adds camber as the wheel is turned. (which is usually good)

Dockman, i think you are talking about camber, which is the angle that the tires make relative to vertical, looking from the front or the back of the car. Like you said, it is there to maximize the tires' contact with the ground while body rolls in the turn.

As far as i know mittimj, there is no good reason to make one of your tires lift during a turn, it would mean less traction and poor cornering. In your go-kart, caster doesn't likely cause the wheel lift. It's probably just a consequence of a solid axle, and no springs or dampers. It's likely unavoidable as soon as the body rolls enough in a turn.

[link=http://www.ozebiz.com.au/racetech/theory/align.html]Here's[/link] a decent but not too technical read about caster, camber and toe.

caster does change the wieght on the rear tires as you turn and that is that. No arguement I know I am correct. I race my go kart and that is a well known fact. Think about it. If the king pin is tipped back it will make the tire go up or doun as you turn. This also helps the car go back to center or go straight. And will change the wieght distribution amungst the car and it will make on tire in the back have less weight on it than the other, the inside tire.


I was thinking about the whole locking diff thing and decided that it wasent a good idea. Also scence it is such a pain to get to.

gerwen- I wasnt confused at all. In fact I agree with what you said I guess maybe I wasnt clear enough in how I said it. The caster in the front does effect the camber as the wheel is turned. The more caster the front end has the more camber you will get when the wheels are turned. As you said the caster does help with stability since the wheel want to go straight and also its there to help with bump and jump handling.

mittimj- Dude, if you already have your mind made up why even ask a question and waste peoples time that are trying to help. Simply put caster does NOT affect the weight transfer from the rear end. That is not its purpose. You can have no caster at all and when you slow down to go into a turn you will still transfer weight forward. As you turn left more weight will go to the front right tire and weight will be taken off the left rear.
Have you noticed that a stadium truck usually has about 25-30 deg caster. This is because offrod trucks use softer springs/oil to handle bumps/jumps so they get more chassis roll so the extra camber gain due to the higher caster still keeps the tire flat for traction.
In your gokart/on road RCs there is usually very little caster since you use stiffer springs and oil. You dont need as much caster because you dont get as much chassis roll. Less chassis roll allows the tire to maintain a better contact patch with less camber gain.
You never Want the weight to come off the rear inside tire. You use spring/oil combos to try and prevent this, but its a compromise for handling on the rest of the track.
I hope some of this will make sense to you.

Guys,
Caster at an extreme angle can and will raise the rear inside tire in a turn. This isn't a good thing. This means you need a stiffer spring or thicker oil as was said by mittimj. Caster does add camber when you turn the wheels. If you run a lot of caster you need to dial all the camber out when the wheels are straight and make sure that all the tires are making contact with the track in the turn. It isn't good to unload the tires in a turn. You want the most traction you can get to pull out of the turn the quickest. As for go-carts, I race them to. The reason the rear inside tire lifts from the ground is because there is no suspension. The reason that happens is because the chassis from your high centre of gravity is flexing. It isn't supossed to do that but it does because of the speed carried through the turn and it is flexing. Hope this helps you out. As said, if you knew what you were already asking then you shouldn't have posted and caused this frustration between members.
Peter

well if this helps i have a mrc monster truck like form 96 or 97 and i broke the diff ring some how so i locked the diff, well it would spinn kiddies like no other but thats about it every time i turned to fast kiddie.....but luckly i found a mrc monster truck chasis on ebay so i just replaced the hole tranny.... i jb welded it....just degrease it real good...