Leading the RF on Mastersbilt (Smack Car)

[lcpestka]

Can anyone tell me how much they are leading the RF ahead of the LF on a Smack car? I am really struggling this year trying to get the car to turn the center. I can get traction in and off, but can't get the car to get up on the RF through the center of the turn on the gas. I have been running about 5 degrees of caster in the RF pulling the lower forward and keeping the upper straight up.

on my GRTs I used to pull the RF ahead about 3/8 of an inch and had really good sucess, but can't find the sweet spot on these Mastersbilts. Any help would be greatly appreciated.

[Punisher88]

I was told by Kirk Loudy at Envy to always lead with the left front. On my bwrc when I went to left front leading instead of the Rf it definitely helped steering getting in and seemed to help side bite also.

[TheJet-09]

5.0* of caster on the RF sounds like a lot, at least to me. Keith Masters himself said to run no more than 1.5* on the LF so based on what you're looking for as far as "split" you shouldn't be any more than 2.5* or maybe 3.0* on the RF. I have a Smackdown and am at 1.5* on the LF and 2.5* on the RF. The split coupled with the camber amounts we're running is really pulling the front end left so even at my numbers there's no problem getting the front end to turn into the corner. I'm not sure there is an actual number for the lead your speaking of. For this year I straightened my lowers (perpendicular to the theoretical vehicle centerline) and am adjusting caster with the uppers.

[lcpestka]

I was told by Kirk Loudy at Envy to always lead with the left front. On my bwrc when I went to left front leading instead of the Rf it definitely helped steering getting in and seemed to help side bite also.

Not sure how a car with the RF behind the LF would get off the corner. How do you balance out the car with the LF forward?

[slingindirt83]

I am curious about this as well. I know our pierce stuff the wheel base had around 3/4" difference form left to right but how did it get there. We checked our car we have now and it is WAY different from that . How should it be set? Bob had a measurement in the back that set the rear end in the car but I never checked to see where it sat in comparison to the cross member.

[Punisher88]

I'm not sure what you mean by Balance out? It helped the car steer more positively over all. And also helped sidebite which helps get back to the gas sooner and carry more momentum off.

[MBR Performance]

I've messed with caster some but one thing I've never tried is zero both sides. Has anyone ever tried this? Or run it equal both sides?

[Matt49]

Can't say I've tried it but with some of the things I've been working on and learning, I'm REALLY close to doing it (0 caster both sides). We have SO many ways of tuning dynamic loads on these cars now, I just really think that caster could be adding an unwanted "dynamic" element to all of it. And by "dynamic" in the last part I mean "with steering input".
The idea of caster on any car is to promote "self-straigtening" of the front wheels. The idea of caster split on an oval car is to promote "self-turning" on corner entry. I feel we need neither. Especially given what I consider to be unwanted weight jacking effects. The only other solution would be to have zero scrub radius which is about impossible given our tire/wheel widths. Anyway...I'll stop rambling...

[TheJet-09]

Correct me if I'm wrong, but didn't Rayburn have a "zero scrub" front end at one time, which sounds cool (like it would be less resistance), but actually required the front tire contact patch to break loose in order to turn?

[Dirt_Buster]

Kind of an off topic in a way question but how much toe out are you all running? No scrub fallUnder the category? We're usually 1" at least. Any input on this?

[let-r-eat]

With 0* caster how are you going to keep the car from darting when trying to go in a straight line?

Caster is what makes a front end stable. Don't believe me just put some negative caster in both sides and see. Look out water truck!

[ALF401]

Save the water truck!! Why not put .5 in Left Front and then 1.5 in the right front and take to power steering off the car to save weight..........

Really, if you look at the angles that are recommended and the length of the spindles used today there should be very little distance that we are talking about here. But the real issue is when you back steer and that affects the left rear and how much "bite" the car has at a given point.

[Matt49]

How often are the wheels really pointed "straight" and the car going "straight" at any point on the race track?

[MBR Performance]

Negative caster will make the car darty. I wouldn't make it zero but maybe .5 or less each side to insure no negative caster. with that low of caster you would rely on toe and bump steer to stabilize the car and keep it from being darty.

[lcpestka]

Not that the caster discussion in not interesting, But I would like to focus on the alignment of the lower ball joint and whether leading the LF is something people are doing with success or not. And if they are how much are the leading it over the RF? 1/4 inch or 5/8 of an inch?

[Punisher88]

Your inbox is full Icpestka

[let-r-eat]

I had this discussion with a major builder because they moved the torque arm from infront to behind the lower for clearance purposes. The STrut tube then was creating negative instead of positive caster in compression.

0 caster is zero caster. Even though the wheels aren't pointed straight doesn't mean the car can't dart even with the wheels turned in any direction. Straight isn't only straight in relation to the centerline of the racecar! The wheels are pointing straight ahead toward whatever direction they are traveling.

I would be looking at controlling the jacking forces properly.