Why +4.5 instead of +2.5 on caster?
05-23-2007, 04:37 PM
#1
Why +4.5 instead of +2.5 on caster? I tried to have my car setup at -1.2 camber +4.5 caster and 0 toe when it was sent out during the re-build., The alignment guy said +2.5 was plenty of caster and that he wont set it any higher. He has set a few f1 cars at PIR and he didnt see an advantage of the +4.5 caster.
I couldnt intellingently argue with him on the subject and so my car is setup at -1.2 and +2.5 0 toe. Its a little jumpy. Corners great, little bit of wonder on the straights but can be a little jumpy if braking real hard on a corner.
what does the increased caster do ? I've read all the stickes and crap and still dont understand. I know what camber will do but confuses me as to its effect. Thx for the help.
I couldnt intellingently argue with him on the subject and so my car is setup at -1.2 and +2.5 0 toe. Its a little jumpy. Corners great, little bit of wonder on the straights but can be a little jumpy if braking real hard on a corner.
what does the increased caster do ? I've read all the stickes and crap and still dont understand. I know what camber will do but confuses me as to its effect. Thx for the help.
05-23-2007, 07:10 PM
#3
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Caster is basically the angle that your steering axis is off being perpendicular to the pavement. You can demonstrate the effects of caster pretty easily with a piece of paper:
Hold the piece of paper at the top and bottom in the middle of the page with your thumb and pointer. Have the paper straight up and down so the points where you hold the paper are aligned vertically. Now twist back and forth, notice that the paper always remains upright. Now keep your fingers in the same spots but turn the paper to an exaggerated caster angle of 45º or so, twist the paper, and you can see how your tires will lean into the corner to grip better.
Pretty much you always want the most caster you can get, there isn't really a downside to it (that I know of).
Hold the piece of paper at the top and bottom in the middle of the page with your thumb and pointer. Have the paper straight up and down so the points where you hold the paper are aligned vertically. Now twist back and forth, notice that the paper always remains upright. Now keep your fingers in the same spots but turn the paper to an exaggerated caster angle of 45º or so, twist the paper, and you can see how your tires will lean into the corner to grip better.
Pretty much you always want the most caster you can get, there isn't really a downside to it (that I know of).
05-23-2007, 07:45 PM
#4
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You need another alignment guy. More caster makes your car much more stable, especially when braking on less than perfect pavement ( do we ever see that ? ) it also helps its 'return to center" properties.
05-24-2007, 09:28 AM
#6
thx for the help guys. not sure what the techs problem was, why he wouldnt do what I wanted but I'm gonna find another shop. I know Les Schwab isnt the greatest and they argued with me last time but at least they set it the way I wanted them to.
It felt really unstable braking on a speed run I did and had me real concerned. I jumped it from 40 mph to 110 mph and then hit the brakes to see how fast I could stop. It didnt handle it the greatest. I was thinking of backing the camber off a bit as well to see if that would help but maybe its just the caster alone?.
It felt really unstable braking on a speed run I did and had me real concerned. I jumped it from 40 mph to 110 mph and then hit the brakes to see how fast I could stop. It didnt handle it the greatest. I was thinking of backing the camber off a bit as well to see if that would help but maybe its just the caster alone?.
05-24-2007, 01:03 PM
#7
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I'd guess your jumpiness is probably that -1.2* front camber. Many cars run that much, or more, rear camber, but it's rare to see more than -1.0* in front on a street car. I'd guess most street cars are between 0 and -0.5*. For autocross or lapping a road course -1*+ isn't too much, but for daily driving it probably is.
