Ackermann ?

[MasterSbilt_Racer]

I agree with Heavy Duty. If you buy a used car, you should usually plan on putting a new front end on it. The parts may not be right or may at least be bent up or in need of an upgrade.

[pcope98]

i had one of those 02 GRt wide cars it indeed had to have a 19 3/4 rack it used the 96 style black tall spindles looking thru my notes from back then, if i remeber correctly it was very very similar to a black front rocket used longer rf lower i do belave it was 19 on the rf and 17 5/8 on the left we always ran 10 inch uppers, but to make a long story short i was glad it was gone after about 10 races , we could never get it to work out, they fellow who bought it decided to have it restubbed back to the standard front clip and won over 40 races with it afterwards.

[mignum]

[QUOTE=MasterSbilt_Racer;1651314]I agree with Heavy Duty. If you buy a used car, you should usually plan on putting a new front end on it. The parts may not be right or may at least be bent up or in need of an upgrade.[/QUOTE
Every part except the left front spindle on this front end is new, that spindle has the GRT sticker still on it so I assumed that the steering arm length was right at 5 1/2 but I'm not sure now. I talked with someone on here that has an original wide front from the builder and my measurements check out with his all except the steering arm lengths his are 5 1/4 and thats what everyones saying best I can tell. This really screws me up because of the left front spindle steering arm length on my car being 5 1/2 with that GRT sticker on it, so are you all thinking that I should get new spindles straight from GRT? Thanks again

[HEAVY DUTY]

[QUOTE=mignum;1651359]

I agree with Heavy Duty. If you buy a used car, you should usually plan on putting a new front end on it. The parts may not be right or may at least be bent up or in need of an upgrade.[/QUOTE
Every part except the left front spindle on this front end is new, that spindle has the GRT sticker still on it so I assumed that the steering arm length was right at 5 1/2 but I'm not sure now. I talked with someone on here that has an original wide front from the builder and my measurements check out with his all except the steering arm lengths his are 5 1/4 and thats what everyones saying best I can tell. This really screws me up because of the left front spindle steering arm length on my car being 5 1/2 with that GRT sticker on it, so are you all thinking that I should get new spindles straight from GRT? Thanks again

You need to call GRT with the chassis number so that they can get you the right stuff for that chassis. All chassis builders continually change and test new stuff. Just because it has a GRT sticker doesnt mean it is right for your chassis.The best way to explain it would be a spindle for a 2002 chevy monte carlo wont fit a 88 monte carlo. Things have to change as we figure new things out. Otherwise we would all be running a 79 model rayburn and still be competitive.

[rcmaster]

make sure you check ackerman and bump together,and the best way is mark your tires around the center, set your toe, roll your car to what travel on RF you want, re measure your toe front and back, then steer your tires at different amounts and re check, make sure to measure as low as possible to the contact patch front and back, this will tell you exactly what is happening with your front end.

[mignum]

Do I need to set caster with the upper control arm or the lower? I am thinking that this could have an affect on my bump steer and ackermann, after more investigation I am quiet sure that I need a 19 3/4 steering rack, per Joe's recommendation.

[DLM06]

make sure you check ackerman and bump together,and the best way is mark your tires around the center, set your toe, roll your car to what travel on RF you want, re measure your toe front and back, then steer your tires at different amounts and re check, make sure to measure as low as possible to the contact patch front and back, this will tell you exactly what is happening with your front end.

I tried this and finally gave up on our '11 Rocket. The bump went all over the place when we steered from straight ahead and every expert I called including Rocket told me to just set the bump straight ahead and forget everything else. What kind of bump readings do you get when you turn the wheels from straight ahead? Do they change significantly left vs right? What do you do if the bump is fine straight ahead but changes when turned?

[MasterSbilt_Racer]

Do I need to set caster with the upper control arm or the lower? I am thinking that this could have an affect on my bump steer and ackermann, after more investigation I am quiet sure that I need a 19 3/4 steering rack, per Joe's recommendation.

Chassis manufacturer recommendations vary, but it will affect the ackerman. I think few cars have it right when straight ahead, turned left, and turned right.

[hucktyson]

Chassis manufacturer recommendations vary, but it will affect the ackerman. I think few cars have it right when straight ahead, turned left, and turned right.

With the geometry required to have correct bump steer at all 2 locations it would be impossible ..

[mignum]

So I need to be concerned with the wheels turned like I'm headed off into the corner instead of straight mostly right?

[hucktyson]

So I need to be concerned with the wheels turned like I'm headed off into the corner instead of straight mostly right?

When the car is handling their not turned very far anyway ..

[let-r-eat]

Draw a straight line through your lower control arm inner pivot and your upper control arm inner pivot. Your rack inner tie rod position should fall along that line. If your rack and pinion is too short the inner tie rod pivots will fall inside that line and the rack would likely need LOWERED in the car to make it work. That is why you shim a rack and pinon up and down, side to side to correct bump. What you are trying to accomplish is get that inner tie rod pivot in line with the lower inner and the upper control arm inner pivot.Think about this. Looking from straight ahead at the steering the pivots need to lie on the same plane. To illustrate this you would take a string and put on your lower control arm inner pivot and stretch it to your upper control arm inner pivot. Stand back and look at the inner pivot of your rack.............inside that line or outside that line with the wheels pointing forward. If your pivot is outside that line you need to shorten or inside you need to lengthen.Ask yourself this:What determines the length of rack I need? Is it the distance between the lower control arm pivots? Yes if the rack is level with the lower control arm pivot points. No, if the rack is higher. The rack must then lengthen.Here is something else that might help.How do you post pictures here:

[7uptruckracer]

Thanks Let-Er-Eat Ive always wondered what determined the rack width and I'm about to use this on a car. Really great info!

[mignum]

Yep, thanks that helps clear things up for me.

[let-r-eat]

Glad that helps you. Sometimes its easier to get a piece of graph paper and map out all the front end points. A design software is much easier, of course. You can use one square on the graph paper for one inch and get the basic suspension mapped out in front view and side view. Things like anti dive and caster etc can all be figured using mathematics. There wasn't all this computer stuff back in the day, we just used pens and papers.