Straight Axel Caster and Weight Distribution

[Sumner]

.............The reason I ask is I have 15x7 rims now.  I want to go to 15x5  but that narrow I can not increase the back space, so by reducing the rim width (from space, does that help too ?........

You are just going to have to see where the center of the tire is with the new wheels.  If it is more inboard that is good.  The other thing that would help is if the tire is larger in diameter.  That would move the projected point as projected through the king pin out and that would be good.

I feel that increasing the castor will also move the point out as it rotates the point upwards and thus it hits the ground further out.  I can't get anyone else to comment on this though, so it is just my view.  Anyone??

c ya,

Sum

[Cajun Kid]

Sum, Wiilie, Anyone,   I have drawn the same conclusion.  Caster should help a small fraction to move the line out, however,  I can not visualize how the tire height will help scrub radius?  The center of the tire contact patch will not move in or out as the tire height grows or shrinks


Front Tire height... I am at 24.2 now,,, I am thinking of going to 26 tall,  but If i do that It will raise the car 1" higher off the ground. not sure If I want to do that. More room for more air under car. But Alt class allows for a Step Pan (not sure if that is good idea on my car.. What do you think ?


Hmm, but taller front tires will also "slow the steering"  correct ?  Would that help to going taller and narrower ?

I feel the short fat tires seem to follow the irregularities in the pavement/concrete more than skinny tires may ?  am I right ?


See, now that I have rum my car once, I am now searching for ways to make it handle better and safer as my initial runs confirm that the motor can do lots more, the question is can the car do it ??

I am hooked,,, this LSR stuff is a blast,, and you guys and gals on this site and at the track make the experiance even more enjoyable,,, sooy to ask so many questions, but I need to learn.

Charles

[Sumner]

.........  I can not visualize how the tire height will help scrub radius?  The center of the tire contact patch will not move in or out as the tire height grows or shrinks ...........

The center of the tire patch will be the same place, but as you raise the axle the projected point 0f the king pin inclination will move out.


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Notice that the left inclination has moved further from the vertical line than the right one.  The left has the axle higher due to a larger diameter tire than the right example.

c ya,

Sum

[willieworld]

charles   jack the front of the car up about 3 inches then follow the line to the floor and you can see how much farther the lines have gotten apart --thats what will happen with a taller tire --if you put on a taller tire it will move the scrub  --if you change the backspace on the rim ---if you run a narrower rim with the same backspace those are things you can do without machine work  --if you run a taller tire to fix your problem and the car is to high LOWER IT that wont change the scrub with a straight axel and very little with a arms  as long as you dont lower it by putting the small tires back on  LOL    when you get this fixed dont stop there check everything else that effect handleing   --if you need a list i think all of us on this site could think of about everything  ===take all of your measurement accurately otherwise you are just guessing    willie buchta

[jl222]

   Thank God we didn't know anything about center of pressure-center of gravity theories when we built the 222 car, or we would have a lot of wheelspin [resulting in  oversteer and possible spinout] like a lot of other cars i know of.
   Yes the car is low and has 1'' of rake under the rocker pannels.                         
                                     JL222

Like someone has mentioned earlier there is more to it than just CP/CG.  Obviously your combination has worked for you, but I still wouldn't say that it is correct for everyone.  You do have a lot of mass up front in your car and in the middle which I'm sure helps your situation.  If you took a lighter car and just hung weight at the rear bumper I don't think that would be a good deal.  Now a lot of weight in the back doesn't hurt a thing if the car is never upset and doesn't have wheel spin.  Your car must be in that operating mode now.  The CP is only going to come into effect if the car does start spinning the wheels and is upset to the point that it wants to turn.  A lot of cars that don't get into this situation don't need to worry about it probably.

The point you made about the F1 cars I feel actually probably shows what does happen with the weight in the rear.  These cars along with a lot of other circle track cars use a lot of aero work for downforce and to help them handle.  Their main purpose is to corner and not go straight so they work toward a neutral balance where they aren't pushing or loose.  We would like our cars to push if anything.  Once the F1, NASCAR cars do start to spin you can see them spinning like a top in most cases exactly what we don't want to happen. 

John when some of us bring up CP and CG we aren't criticizing your setup as it has worked for you and you are happy with it, we just want some of the people that are considering this for the first time to take a look for what has worked for a lot of other people, in fact airplanes use the concept every day  .  They should also take a look at your car and make a decision what is going to work with their car, their HP, their body style and the speeds they expect to run.

c ya,

Sum
[/quote

       The formula 1 cars i know about were the turbo charged 90 cu in. type that produced 1200-1350 hp [qualifying motors] in the 1980s.
 Not only did they go around corners they had to exit the corner,which was a big problem because some of them tripled
in power from 8000 -13000 rpm. 65%-35% weight distribution [static weight] + rear wing. wheelspin was a problem to harness as the drivers said pressing the throttle was like firing a shotgun. Wheelspin resulted in slower lap times and worse
starting position.
   Cajuns question was what some people were running, not what we thought he should run.If you notice i don't tell people what to do, just what we do.     
                                         Hope to see you at bville JL222

                                           

[Cajun Kid]

Got my car weighed today.
Without Driver
Total Weight Ready to Race is  2521
Front Weighs 1256 (49.8%) and Rear is 1265  (50.2%)
Left Weighs 1258 (49.9%)  and Right Weighs 1263 (50.1%)

LF is 595  RF is 661
LR is 663  RR is 602




With Driver the distribution changes to 52% Left and 52% Rear

Do I need more % of weight on the front ?