Can some one shed some light on shimming the front end of our oval cars.

I was told to shim the frontend so that the upper a-arm matches the tie rods is this correct?

Any and all information. Thanks.

Yes simply speaking adding/subtracting shims above your steering block and under your upper arm to get your upper a-arm to match your tie rod angle will help bumpsteer.
Heres a link to a wealth of information that can help many areas...
http://www.iroaronline.org/dannyb.html

"The more parallel the upper and lower a-arms are the lower the roll center for your car will be. The roll center in its simplest form is how much the front end will roll in the corner. The lower the roll center the higher the center of gravity and vice versa. A good analogy is to think of a flagpole, if you were to grab a flagpole at the bottom (low roll center) the pole would sway back and forth easily. If you were to grab the pole in the center (high roll center) the pole would not sway as easily. The roll center is one of those things that is not a chassis adjustment but more of a building thing. You want the car with a low roll center; this will help the car turn in the corner. More roll equals more weight transfer therefore giving the car more steering. Once you get the car planted in the rear you will need this to make the car turn freely."

Ok...

So is it more important to keep the upper a arms more parallel, lower roll center, to the lower a arms than to get the upper arm even with the tye rods?

The lower the roll center the higher the center of gravity and vice versa.

Roll center placement has nothing to do with establishing
the center of gravity...

Can some one shed some light on shimming the front end of our oval cars.

I was told to shim the frontend so that the upper a-arm matches the tie rods is this correct?

Any and all information. Thanks.


Not getting into the whole roll center discussion, here is how most people run.

Left front upper arm parallel or close to parallel with the ground. Right front at an angle (kingpin side higher then caster block side) relative to the ground. The biggest reason, in my opinion, why this is the typical set up everywhere is camber gain. When the arm is at an angle the camber increases as the suspension compresses. On your right front you want camber gain since the tire rolls to the outside while cornering and on the left front you don't since the tire is rolling onto the inside edge. The more camber and camber gain you have on the RF the more the car will turn.

That is a very broad overview.

Simkins that makes sense. I wonder if that would apply to a suspension car on dirt? (more camber and camber gain on RF=more steering) I would think so. Also, I don't get why in touring car once, my car was pushing terrible, a racer suggested more camber gain in the rear camber, I did that and it helped a ton. That doesn't really make sense to me, any idea why that worked? Maybe it made the car "roll" on the RR more which would also transfer more weight to the RF?

I almost always run 0 camber in the rear of my pan car. Trying to figure this dirt stuff out though.

Actually weight tranfer is more from LR to RF when going through corners. It's not really a big thing in RC, as far as I can tell, but in the real cars, crossweight is something we check before every race.

Actually weight tranfer is more from LR to RF when going through corners. It's not really a big thing in RC, as far as I can tell, but in the real cars, crossweight is something we check before every race.


keep thinking that :thumbsup:

Explain....

May not be a big deal in RC because of the effed up rear suspension design, but weight transfer is a basic principal. Atleast on any car i've ever built, driven, or worked on.

weight transfer is a big thing in flat carpet oval

As it is in any type of racing. But tell me how weight transfers from the right rear to the right front in any situation other than braking in a corner?

I never said it did

Well that is what I was responding to after reading Tommygun's post

As it is in any type of racing. But tell me how weight transfers from the right rear to the right front in any situation other than braking in a corner?

Any change in direction is a change in accelleration even if the object in motion remains at a constant speed.

Weight will transfer to the FR of the car while turning LEFT even if the speed remains constant.

This is an simple explantion of it (http://www.glenbrook.k12.il.us/gbssci/phys/Class/circles/u6l1b.html)

Right over the head lol

But what does that have to do with weight tranfer from RR to RF?

Here's a link for you
http://www.autopedia.com/stuttgart-west/Physics/StuttPhysics01.html

And another one that explains crossweight and it's impact on weight transfer

http://www.circletrack.com/featuredvehicles/139_0303_crossweight/index.html

While I work on road racing cars these days, the principals are all the same, Atleast that is what Bill Riley tells me, and considering his chassis rarely lose, I'll take his word for it.