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Thread: Understeer. Loads of understeer.

  1. #11
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    May 2019
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    Here was my fastest today. Terrible technique though. I probably left at least a second on the course with all that acreage between the car and the cones :-)

    https://www.youtube.com/watch?v=f9b4...ature=youtu.be

  2. #12
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    Feb 2009
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    Fascinating video. Great location for an autocross - nice big course. Your hands on the steering wheel got confused a few times and you really needed to change down a gear a few points to keep the engine in its power band. Understeer seemed mostly under control but it was there at times.
    Mike
    2010 Caterham CSR with Cosworth 2.3 Duratec
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  3. #13
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    May 2019
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    Quote Originally Posted by Croc View Post
    Fascinating video. Great location for an autocross - nice big course. Your hands on the steering wheel got confused a few times and you really needed to change down a gear a few points to keep the engine in its power band. Understeer seemed mostly under control but it was there at times.
    Definitely a few first gear corners there. My heel-toe technique needs a bit more practice before I'm going to try that with the 7. The Honda is like a battleship and can handle a downshift like that without heel toe but I'm a bit more cautious with this car.

    Understeer is much more pronounced in the earlier laps. I was able to do about 10 fun runs on Saturday, which was great. I figured out I need to backside a lot more with this car because it doesn't rotate as well. On the Honda the front really digs in and gives the back a good point around which to rotate. It's super fast through a slalom if I can I can get the tail wagging I started off driving the 7 like the Honda. The Honda has nice balance - I get a little bit of mid corner oversteer and then if I'm just a hair too fast, a bit of exit understeer. About as balanced as you can be with a car that has a 62f 38r weight distribution. I like to refer to autocrossing a FWD car as the triumph of enthusiasm over physics :-)

    Mississippi Region has the absolute best locations for autocross. We're lucky to find a postage stamp and these guys have both Grenada airport and a section of the runway at Columbus Air Force Base. That's why I drive the 2 1/5 hours.

    Hands, yeah. Hand position is a challenge for me. The Honda has extremely slow steering and there are times when hand over hand steering is faster than shuffle steering. Since the 7 has a Caterham quick rack, I really don't need to do that, but it's just another habit that works with the Honda

    Anyway, I have to decide how serious I am with autocrossing this car. I really don't want to tear it up, but if I put the old windscreen back on and get some 200 tw tires I would be in Heritage Classic Street and I would actually be competitive .
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  4. #14
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    Sep 2007
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    Houston, TX
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    Lots of good suggestions here, but I think your tire pressures are way too low. Toyo recommends 17-22psi cold and 22-29psi hot. On a typical autocross run you will not generate enough sustained heat to get to the hot recommended pressure. I would start with 22 psi cold and experiment with even higher pressure and monitor tire pressure between runs to see what you are actually gaining.

  5. #15
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    May 2019
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    Quote Originally Posted by James A View Post
    Lots of good suggestions here, but I think your tire pressures are way too low. Toyo recommends 17-22psi cold and 22-29psi hot. On a typical autocross run you will not generate enough sustained heat to get to the hot recommended pressure. I would start with 22 psi cold and experiment with even higher pressure and monitor tire pressure between runs to see what you are actually gaining.
    I think the sidewalls of the R888Rs are too stiff and the car too light for the treadwear to line up with the diamonds, regardless of the tire pressure. I went up on pressures for Sunday. I think with this car on these tires, 10 in the front and substantially higher in the rear (eg 22) is going to balance it out as much as it can be balanced. Obviously that's not an ideal situation and is a kind of a mickey mouse fix - the proper way is going to be to model the suspension and likely increase the rear roll stiffness relative to the front. I usually shoot for 2.2-2.5 Hz spring frequency in the front and about .2 to .4 Hz higher in the rear as a starting point, so that may mean swapping out springs on all four corners, who knows.

    I'm honestly not sure yet if I'll both since I didn't buy this for autcross and I don't want to tear it up

  6. #16
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    Jul 2009
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    Arkansas and . . .
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    Quote Originally Posted by xcarguy View Post
    . . . when running on slicks on a damp/slightly wet track (yes, with slicks), my car absolutely pushes through the turns. This not to say that I donít get oversteer as well (Croc can verify ), only that the tendency is for understeer. Example; I did . . .
    Correction to my original post....
    Stalker V8, chassis #85

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    Get up in the morning and give the day your very best. You donít get it back.

  7. #17
    Join Date
    Apr 2016
    Location
    Cary, NC
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    34

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    Itís probably not the case with your car, but do you have a limited slip rear end, or possibly worse, a welded differential? In tight turns, these could cause the front to push out during acceleration.

  8. #18
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    May 2019
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    OK, an update. Some previous owner replaced the stock front springs with 260# springs. I dropped them back down to 175, adjusted the ride height. Handling was much better and I was about 2 seconds faster per lap. It still has a tendency to understeer though. I'm going to adjust the camber back to what it was (changed a bit when I set the ride height) and move the rear bar up a notch. Should tame the rest of the understeer. I'll be able to try it out at MIR tomorrow at our last track day of the seasonl.

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