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Old 04-08-2004, 01:00 PM   #1
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Default Rear end lifting on the inside

The situation is, that my car handles pretty good. It's more stable than ever before, yet very responsive - almost too responsive.

In hairpins, the inner rear wheel lifts off, if I turn too sharp and fast. Of course there's some limit, but I didnt had that problem before. Also, in other sharp turns, if I'm a little off-line due to other racers, the inner rear wheel also lift.

I'm not really sure what the cure is: Less downtravel, stiffen up the rear or thicker shock oil? I tend to try thicker oil, since that both shold delay body roll and make the car less responsive.

I'm racing on carpet with a few bumps, rubber tires and stock motor. HPI Pro2, almost stock, saddle pack.

My setup goes like this (unless other's noted, it's the same all around):

Tires: Schumacher Dragon Carpet with Sorex type A insert. Soft wheels. These are THE tires for our track.
Springs, front: HPI Green, 480 g/mm.
Springs, rear: HPI Red, 432 g/mm.
Shock oil: AE, 60 wt, piston number 5.
Camber links: Short as possible, angled (only one angel, except for parrallel).
Downtravel: 2 mm.
Ride hight: 5 mm.
-1,5 degree camber.
10 degree castor.
1 degree toe-in front, 2 rear.
No one way.
ESC auto brake disabled.
Mondeo body (handling close to HPI Stratus)

Thanks.
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Old 04-08-2004, 01:16 PM   #2
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I would stiffen up the rear. I had the same problem with my car a while ago, except it was the front that was lifting. I had a swaybar on, and taking that off fixed it. When you stiffen up the rear, you may also want to go up one level of spring on the front too, to preserve the balance you have. I would try stiffening just the rear, and the front and rear.

Good luck,
Josh
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Old 04-08-2004, 01:32 PM   #3
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Josh, that sway bar, did you have it front or rear? I maybe try a swaybar at the rear - usually that's considered stiffing it up... (I know sway bars aint the best for bumpy tracks, but the bumps are quite small, so several people had succes with that - and if I order stiffer springs now, they probably wont be here before next race)
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Last edited by Cole Trickle; 04-10-2004 at 05:05 AM.
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Old 04-08-2004, 04:29 PM   #4
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I had the bar in the front, but I wouldn't recommend putting one on if you're having said problem. The reason taking it off fixed my car is because the car had a lot of roll, and the swaybar would lift the inside tire off the ground when it got to a certain point. So installing a swaybar would probably make your problem worse.

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Old 04-08-2004, 07:02 PM   #5
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Sounds to me like you need more rear droop or downtravel (same thing.)
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Old 04-08-2004, 08:51 PM   #6
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Cole, lengthen and raise up (make it flatter) the rear camber link. The short links are not allowing it to roll deeply enough into the corner and since they are angled there is more camber gain, as well. Everything else looks good although you are running a LOT of caster...i'd take it down to like 4-6 degrees.
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Old 04-08-2004, 09:25 PM   #7
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maybe putting stiffer springs in the front will help...

In your honest opinions, do you guys find sway bars actually make difference?

I can't tell the difference but probably because i am not good enough driver...
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Old 04-09-2004, 11:08 AM   #8
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Super Steve

Depends on the car. Some cars have better swaybar mounts than others and the way that the bar mounts to the suspension has a big impact on how effective the bars are. I have a couple TA04's and the bars are pretty worthless in the rear due to the sloppy mount arangement they use. The front works well, though. You need to set the car up with more droop than you would run without bars in order for them to be effective, though.
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Old 04-09-2004, 12:04 PM   #9
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On a TC3, swaybars have a very large impact on handling, and are a great tuning aid because there are different thickness bars to use. Or you can use none, or one, or both (front and rear)

Generally, whatever end you attach a sway bar too looses grip, unless your suspension is TOO soft, whereas excessive roll is causing you to lose grip (side bite) then a sway bar will help. Or, you can acheive basically the same grip by installing a sway bar and softening the spring rate or re-locating the shock position to a "softer" location.
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Old 04-09-2004, 12:21 PM   #10
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Drop the caster down to Mr. McGreevy's 4-6 suggested settings.

What is happening is the car is "tipping" onto the outside front. This is caused by excessive caster. Caster raises the outside wheel and lowers the inside wheel when the front wheels are turned. This causes natural wheight jacking at the corner entry, encouraging the car to turn. Too much caster and the car "tips" onto the outside front. The reason you see this in the hairpin and slow, tight corners, is beacause the effect is exagerated by pitch (rear to front weight transfer due to deceleration).

Later,
Phil Matthews.
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Old 04-10-2004, 04:52 AM   #11
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Quote:
Originally posted by psycho
Sounds to me like you need more rear droop or downtravel (same thing.)
I think it's the opposite. I had 3 mm downtravel in the rear and the problem was there. So I limited to 2 mm, and the problem became smaller.
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Old 04-10-2004, 05:04 AM   #12
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Quote:
Originally posted by Brian McGreevy
Cole, lengthen and raise up (make it flatter) the rear camber link. The short links are not allowing it to roll deeply enough into the corner and since they are angled there is more camber gain, as well. Everything else looks good although you are running a LOT of caster...i'd take it down to like 4-6 degrees.
Before I shortend and angeled the arms, the rear tend to slide out instead....

And I like the responsive feel with short/angled arms, so I'll give it a try.

But that castor thing sounds very reasonably. However, I cant go lower than 8 degress on my car. But I'll try it.

I've also ordered stiffer springs, so I have the option. They should be in before next race...
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Old 04-10-2004, 05:25 AM   #13
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The reason people have found taking off sway bars helps is because grip is peaking...

A sway bar adds grip to the opposite end of which it is added usually, and limits roll, so the whole car has to lift a wheel

In a real car, if a sway bar is too stiff the car will "Hop" which is the inside wheel lifting, and due to high amounts of momentum, the outside wheel skips sideways and drops the inside, now a small car like ours dont have a high momentum rate... so they dont "hop" just lift...


Increasing droop will allow more weight to be thrown to the front, so it makes it even worse...
Try and remove some rear wheel grip...
I'd try a little bit of rear toe out, or at least no rear toe...
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Old 04-10-2004, 05:28 AM   #14
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look at Josh Cyruls race report on the xray webpage, he had the same problem. give what he did a try
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Old 04-10-2004, 05:29 AM   #15
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Quote:
Originally posted by dontfeelcold
look at Josh Cyruls race report on the xray webpage, he had the same problem. give what he did a try
Can you provide a link? Thanks.
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