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nowings4me  
#1 Posted : Wednesday, September 11, 2019 9:55:13 AM(UTC)
nowings4me

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I've been pretty loose when the track gets slick in the feature, so last race I thought I'd lower my roll center before the feature since we know that tightens the car up by transferring less weight to the RR, keeping the rear tires more equally loaded. Then I made my typical adjustment of moving the RR in, which we know tightens the car up because when the track is slick, less weight transfers to the RR, so moving it in helps add that weight back. Then it\crap me...this seems like a paradox...one adjustment tightens the car because it allows less weight to transfer to the RR, but the other adjustment tightens the car by adding RR weight. Is this right? Maybe I want to RAISE the roll center for the feature when it gets slick, as that would achieve a similar goal as moving the RR in??

Please help, this is melting my brain.
Mike Dicely  
#2 Posted : Wednesday, September 11, 2019 11:52:18 AM(UTC)
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Ah good question, I think I answered this somewhere else on here, but here goes.

Moving the RR in tightens the car because it causes a big jacing affect causing the LR to jack up when in a turn. When the LR jacks up, the CGH goes up, when the CGH goes up, we get more weight transfer from the front to the rear. There are better ways to raise the CGH than moving the RR in. I don't like doing that.
nowings4me  
#3 Posted : Wednesday, September 11, 2019 1:05:51 PM(UTC)
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so then what about moving the right rear in when it gets slick because the g forces on the car are much less on a slick track? I thought I read that somewhere. What you are suggesting would mean moving the RR in only has a tightening affect during corner exit, when weight is transferring from front to rear, correct?
Mike Dicely  
#4 Posted : Wednesday, September 11, 2019 3:22:22 PM(UTC)
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Just add more static RR weight by adding turns to the RR and LF.
nowings4me  
#5 Posted : Tuesday, September 17, 2019 9:51:52 AM(UTC)
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But the paradox is still there. Adding static RR weight for a slick track directly contrasts with lowering the roll center to tighten the car. One adjustment adds RR weight, the other reduces it (reduces dynamic RR weight), but both are claimed to tighten the car.

Mike Dicely  
#6 Posted : Tuesday, September 17, 2019 10:01:50 AM(UTC)
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Right, and I talk all about that paradox in my Rethink dirt paper. But my conclusion is that on a small track longitudinal weight transfer is more important that reducing lateral weight transfer. Also we get both by raising the car and moving the RR out. And when I said to add more static RR/LF weight, I was assuming you are heavy on the LR now. There is a balance. And due to the larger contact path of the RR vs LR, we need to end up with about 30% more RR than LR weight to get maximum traction. on a slick track when the g-forces are less we have less weight transfer from the LR to the RR, so we need to bring some of that weight back to the RR statically to end up where we want to be.
nowings4me  
#7 Posted : Tuesday, September 17, 2019 3:31:44 PM(UTC)
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Thanks for the explanation.

So would I be correct in saying that after the heat race, when the track is getting slick for your feature, that is not the time to be moving the roll center down, but if you were loose in the heat race, and the track is the same exact conditions for the feature, that would be a good time to move the roll center down?

Basically moving the roll center is more of a base set-up adjustment, while adding static RR weight is an adjustment to make throughout the night as the track gets slick.
Mike Dicely  
#8 Posted : Wednesday, September 18, 2019 7:20:53 AM(UTC)
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Lowering the rear roll center will reduce the lateral weight transfer to the RR and increase lateral weight transfer to the RF. Depending on how slick the track is and how much static weight you have on each corner as well as other dynamic weight transfer variables, this may or may not tighten the car. If you really want to dig into this, you should enter your specific numbers into the formulas, play around with the g forces (you can get these off your Mychron) for slick and wet track, and see what you need to adjust to get your weights where they need to be for maximum traction. There are no straight forward answers like everyone is searching for "when the track does 'this' what adjustments should I make?" Without knowing all the numbers you cant say anyone thing is always true. You can make generalizations, but you have to preface your answer with 'generally'.
thanks 1 user thanked Mike Dicely for this useful post.
nowings4me on 9/18/2019(UTC)
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