what to do about wheel lift? this was in a right hand corner within a short section of left/right/left turns, 2nd gear, very fast transitions from left to right ...

obviously, the front swaybar is holding up the pass. tire as the load shifts to the drivers side.

looking at the geometry of the front swaybar i don't see any way to prevent this except to replace my front shocks with a flat piece of iron so i don't get *any* bodyroll what-so-ever ...

what am i missing here?
Andy

BTW: this is on super sticky racing slicks, the car rather flips over before they will give away and slide ...

Just aim for the cones, the wheel will lift, go over the cone and you've created a shortcut, just like Peter Gregg used to do.

T.C.

Roll stiffness!!! Way to go!

would limiting compression on the drivers side do the trick?

Coil overs?

I think that would get rid of the wheel lift.

yes. welding in a piece of steel instead of using shocks ...

but, i was hoping there would be some other solution ...
Andy

how could it? coilovers don't change the swaybar geometry. how would coilovers prevent the swaybar from lifting the unloaded wheel?

Andy

NO sway bar,

Coil overs instead.

Therefore the "No load" would just rest the tire on the ground.

Andrew

Increasing rear spring rate, or changing the front bar, or lowering the car more, will stop this. It's transferring too much weight to the left rear, and the suspension can't droop enough to let the tire stay on the ground. The droop limiter is either the front bar, or the strut (more likely the bar). The fact that the left front is heavily compressed means the inside front will also be "lifted" by the bar, so a softer bar will reduce this. Lowering the car will reduce overall weight transfer, so the car won't roll as much.

The question is: is it really a problem? The inside front is obviously very lightly loaded, anyway, so all you're going to do is help to load it (slightly). The very small increase in front grip will most likely be offset by losses elsewhere if you "fix" this. If you're understeering in places where the inside tire is lifting, then maybe there's a benefit. If you're not understeering, then keeping the other front tire on the ground isn't going to help.

Two things:
Make sure there is no preload on the bar. Set the car level and disconnect one side of the sway bar. Then dial the disconnected end link in until it will bolt up with no fuss.

Second, you need to add roll stiffness to the rear or take some out of the front. First try adding a few more lbs of spring rate to the rear. Say 25-50lbs. If you have a rear bar add a little more bar. Test each one of these seperately and see what happens.

You may also have to, in combination with rear changes, soften the front roll stiffness, slightly.

If this is a problem in one or two corners, then you might try adding a little compression to the rear shocks and see what happens.

hard to judge from behind a computer monitor, but...

possibly heavier rear springs
if the outer rear compresses too much it will make the inner front lift (specially with a big front swaybar - which makes the front susp. less independent - and a rigid chassis)

or maybe heavier front springs and lessen the front swaybar

what are you running (susp.wise)?
All I remember is that you have a 22mm tarett front swaybar
what t-bars up front and what spring rate rear?

Will it do the same thing with the other front wheel when turning left? If not, maybe you should consider NASCAR..

I don't know how much the weight of a driver affects it, but if you carry a passenger for balance, it should do the same thing on both sides. Maybe tub bentness would affect that?

A car will always corner faster on four wheels than it will on three.

then what are the coilovers for? *no* swaybar and 911 torsion bars work just fine, no wheel lift.

BUT, no sway bar also means *no* way of fine-tuning in my suspension setup front/back ...
and that ain't gud ...
Andy

did that, *no* preload on the bar. i made sure of that before the event.

rear is already 250lbs springs and a stock rear swaybar. front is stock 911 carrera ('85), whatever torsion bar size that is and a 23mm tarett swaybar.
one would *think* the rear is heavy enough, but maybe not.

full rollcage, so not much body roll in the tub itself. freshly corner balanced.

no understeer, just a tad of oversteer, front bar pretty much dead center with about 2" to move either way ...

yes, the tweaked tub could be a factor here ...
Andy

Coil overs dude... lol

How fine do you want? You can go 5lb increments with coil springs....

Yes, money... I know.. But you said you wanted no lift... lol

if it were me, I would try what they said as to stronger T bars and a softer sway bar. (and the pre load thing...)

Andrew

I agree, but sometimes the compromises made to keep all four wheels on the ground aren't worth the cost or the effort. Adding more rear bar would help, but also might make the car so oversteery that it will be difficult to drive. Softening the front bar would also help, but may increase roll to the point that the front tires don't work anymore. Add more camber to fix that, and you may upset braking too much. Lowering the car more may hurt streetability too much (this is a part-time racecar, remember).

It may very well be that living with the inside front lifting is the best compromise.

or two for that matter ... as you can see, no body roll to speak of, the tub still looks flat, just at a slight angle ...

Andy

lol, I still cant believe your car did that...

I want slicks! (oh wait... theres that breaking stuff thing...)

Andy: Easy fix. Put bigger tires on the right side.
Dave

When you have to compromise the grip elsewhere just to get the one tire to touch down, the car will corner slower on four wheels than three. Sure you can add a ton of rear roll stiffness to get that front tire down, but then the car will oversteer, probably pretty badly!

James (Lapuwali) is dead-on correct in this.

--DD

My mentor told me that if a wheel lifts then you have to increase the pressure on the pavement from the diagonally oposite corner. My 2L car used to lift the inside front wheel usually due to the Goodyear slicks, even with a front and rear sway bar. It had 200# rear springs and going to 300# rear springs cured the problem. This is figuring you have at least a six point roll cage and not just a bar with a brace, otherwise the body is twisting badly as I don't remember if you have a cage or not? Remember, if you do change the rear springs, then a fresh corner balance would be in order. As several have noted, you corner faster with all four wheels on the ground.

this is without a rear bar? do you ever hook yours up just to see? your car must feel some kind of unsettled when it's up on 2 tires.

k

actually, the 2 wheeling felt suprisingly stable. no sliding, no wiggle, stayed in line, didn't hit a cone, didn't even slow me down much. still got a 57, with 55 being my best time of the day ...

Andy

I was going to say stiffer rear springs will keep the front on the ground, but then I saw BOTH inside tires in the air......

NO ammount of stiffer springs will help that condition.

Something else that MAY keep both front wheels on the ground is a stiffer chassis (roll cage).

The other thing is, your tub is twisted. It will act funny until it is un-twisted. (How is that working out?)

Perhaps a wing or some ballast may help when lifting two wheels. How about training wheels?

sure looks cool. thanks for the Ctrl andy.

k

my question is about the *one* front wheel lift as shown in the first picture. i just threw in the 2 wheel pic as a bonus. i know what causes that, so no surprises there ...


but i'd really like to know if there's anything i can do about the front wheel lift besides putting 500lbs springs on all 4 corners ...
Andy

How far are you on your sway bar adjustment?

Could be worth a shot to loosen the front a little...

read post above where i quote my own post from the first page ...

Andy

The idea (that has been stated here a few times now) is to reduce the front roll stiffness and or increase the rear roll stiffness.

stiffening up the rear is kinda out of the question. 250lbs springs + stock rear swaybar is already pretty stiff. remember, this *is* my daily driver also ...

so how to go about making the front softer without losing the adjusteable swaybar? right now, the car is perfectly balanced. going softer in the front would change that unless i can retain a working front swaybar that still has some adjustability left in it ...

Andy

and how about my mueller roller bearing i have sitting on the shelf here?
would getting rid of my 30+ year old sticky rubber bushings make a difference?

Andy

where would one start with the front? soften up on the torsion bars first? didn't you have to alter the drop links in your car andy (long ago u&b)? what causes the joey chittwood (2 wheel) driving?
k

super sticky tires that refuse to slide ...
Andy

I just wonder if the front bar isnt allowing suspension full travel when it becomes unloaded. Your car in paticular has always seemed to have signficant front wheel lift. Well at least until Alameda. Now it has bicycle syndrome.

andy, upping my front t-bar rates, backing off my front sway bar, and raising my rear spring rate slightly has helped keep all 4 down on my car. the 710's i'm running don't have quite as much raw grip as my old hoosiers, though, so that might be part of it.

i'm not going to get into the debate as to whether or not lifting a wheel is slower or faster.... no one i respect says that it is a 'good' thing, but i've heard experts vary on how 'bad' it is.

i will say, though, that your car's ride height seems a little high to me. even given stock geometry, i think you can go lower. or maybe raise those spindles...

andy....

i read tune it with spring rate, and then throw swaybar at it...

maybe stiffer all around (you have 19mm torsion bars if stock 911)

up it to 22 with 250's.... and back off on the sway bar....

I think there is a point of having too much grip. You and that 911 shown somewhere here recently are running slicks. The surface must have tons of grip and very compatable to the tire compound.
Or some Knuckle head is designing a course that is too fast into a tight turn. and you Knuckle heads ain't got the good sense God gave to know better.

I'm going to say that the smoother you get the less you will lift the front wheels or go up on two.

Both Bill and Randal were driving the same car.

No slight on Bill, but Randal was clearly driving the car smoother.
it showed in the fact that he didn't lift the front, go up on two wheels or sling the rear end around getting rear wheel hop and wheel spin.

I have all of this on video.

You never lifted the wheels again in that corner where you got two wheels up.
And you got faster, too.

Some courses will cause certain cars to lift the wheel a bit. Pretty common actually.

The exit from the "go-cart" chicane and the finish line at RR are two turns where I always lift the inside wheel a little.

Car stays flat and no control is lost.


KT

Andy - as long as your car is capable of going up on 2 wheels - no amount of spring or bar changes will solve that. Only way to solve it is to either lower your center of gravity, or reduce your tire grip.

I know!



Drive slower. That'll keep all 4 wheels planted firmly on the firmament.

you are correct, sir ... that is due to the bend tub. when we corner balanced the car, i didn't want to go too low as the corners are off by as much as 4" (holy mother of bend tubs!) ...

once the thing is straight, i will have it come down a bit ...
but right now, the corners are very well balanced.

maybe it's time to make the front a bit stiffer? it's complete stock 911 carrera with who knows how old boge shocks ...

Andy

you are mistaken ... on all 4 afternoon runs i heavily lifted in that corner. only got on two wheels once, but the other 3 runs it lifted enough for the pass. rear wheel to lose *all* traction. tire was spinning freely up to where the valves started to float. lots of rpm and no go ...

so that corner did upset the car big time once the tires started to grip well (in the afternoon) ...

that corner was not particularily abrupt either, hard right hand, yes, but with time to get the car settled before turning.
it just happend that i could carry *much* more speed into & through that corner in the afternoon, to the point where the car would lift ...

lowering the center of gravity is an option, less sticky tires is not ( ) ...
Andy

I'm surprised that no one has pointed out the simple solution........less horse power

Here is an exerpt from "Performance Handling How to make your car handle" It claims that you have your front sway bar too tight for your spring rates.

'If the antiroll bar is too stiff, it will lift the inside wheel (front or rear) off the ground during cornering. This is not a major problem at the front of a rear drive car or at the back of a front-driver, but is serious at the drive wheels, especially at the exit of a turn when power is applied. The solution is not to increase the amount of roll resistance provided by the antiroll bars, but to increase the amount provided by the springs. Stiff springs will not try to lift the inside tire off the ground as an antiroll bar will.'



Loosen your front bar or increase your front springrate, and you will stop lifting the inside tire.

I still think Randal proves smoothness is a huge factor.

Give Randal a little more seat time in Fritz, and he takes TTOD.


KT

Who was it that said they are faster on two wheels, less friction. Maybe outriggers would help.

randal also was the one that flatspotted the tires on bills car. so much for "smooth" driving ...

he overcooked the tight corners not once, not twice, but at least three times. and not in a settle kind of way either ...

the power of a 3.6L is something one has to get used to ...

i actually begin to like driving with my current 1.7L ...
Andy

ok, so stiffer torsion bars and less sway bar dialed in ...

what's the next step up from a 19mm 911 torsion bar?
Andy

Can you increase your psi in the front tires to keep the inside tire from squating as much and to slightly decrease grip?