George A

Bob, judging by the large red markings on your passenger tires, you are running the Yoko's (me too). What size are you running? Are they the 230's and 280's or something much wider? I've noticed an increase in understeer also (but I don't mind it). I'm actually wearing the outside front faster than the rear.

I hate making little changes. I would probably even try 1200/1400 if I get boared. Springs are inexpensive. I just wish you didn't have to realign the car every time you changed them.

George

kev

Hi Steve, I've seen race cars with zillon $ suspensions commonly exhibit front wheel lift and always assumed it was an unavoidable consequence of a race suspension's extreme stiffness or radical geometries. I'm surprised to hear that it is actually improper suspension tuning.

Like George mentioned, the car feels pretty flat through the turn.

Could you further elaborate on this issue? Thanks!

viperbob

George,

Yes I am running Yoko race slicks. 250/320s. Pulling a wheel off the ground is caused by a number of factors. Some of it is related to the rear needing to be a little stiffer in the bar or potentially the spring. Other facrors are as Kevin mentioned the use of other solid suspension components. One of the factors in my case is that I run Motons, and they do not have much droop at all. So if the body treeks a little (and all these cars do it) then it will tend to pull a wheel sometimes off the ground. In most 911s it is not that big of a deal. It is a little worse in my turbo as it is AWD and the front is always trying to pull.

George A

Bob,

I wish I had adjustable shocks/struts like you. That's going to be my next investment. I just had the Bilstiens revalved for 650/800 and I bet I would need them revavled if I went with much stiffer springs. I've noticed the body does flex more than I want. I've been told a cage would stiffen the chassis a little but I still drive it on the street once a week (at least that's my goal) and I don’t like the idea of all that steel around my bare head. I just bought and installed a DAS bar (thanks Dylan) but I'm not sure that really makes the car any stiffer.

George

Nemick42

Can you describe the handling characteristics of the car as it is now, regardless of wheel lift?

George A

Neil,

The car actually behaves perfect for me. It's got a slight hint of understeer that's easily changed by the gas pedal. Turn in doesn't feel as crisp as it use to, but I'm also not experiencing the power oversteer at the end of the turn.

Previously, my car would turn in great and the entry characteristics were perfect but the exit oversteer was hard to live with. I'm sure it lifted a wheel even then.

I am willing to bet that if someone else drove it, they would get a different impression. It’s hard to really get an idea of what a car is doing without getting more that one opinion. I don’t think I’m experienced enough to really give you the exact characteristics.

George

Glen

George , let me drove your car. I am able to take 3 seconds off your times by letting You observe.....lol

kev

Glen,

I sent you an email the other day...can you put me in touch with your piggyback oil cooler fab guy or happen to have one lying around?
Much thanks.

George A

Glen, so you want to switch cars for a session? See you Tuesday.

George

Glen

Kev, dont do the piggy. We had some heat sink probs with it so the one per side is best. I think I have a spare cooler though if interested.

Steve Weiner-Rennsport Systems

George-Kevin:

Whether a 911 lifts its inside front wheel is dependent on many factors such as Bob pointed out:

A) Suspension droop as defined by shocks

B) Front roll center as defined by ride height and front uprights

C) Front roll stiffness (springs & swaybar)

D) Rear roll stiffness (springs & swaybar)

E) Wheel/tire package

As you already know, these cars do have a tendency to momentarily lift an inside front wheel when exiting a corner under power. Its a question of degree whether its a problem or not. A 3-wheeled car doesn't corner as quickly as a 4-wheeled one and the real concern is how far and how long the inside front tire is off the ground. If its a momentary thing or a very slight lift, it may not be a concern.

Up to a point dictated by rear tire size and the car's aero package, one addresses this by stiffening the rear end with firmer springs and/or stiffer rear swaybars and settings. One has more flexibility when one has an effective, adjustable rear wing (with a Gurney flap) and front splitter. These two items permits one to run very stiff rear springs without paying a penalty in grip on bumpy & uneven surfaces.

The other big variable is when people lower the car too much and the front roll center goes below ground. This really exacerbates the front lateral weight transfer (not to mention bump steer) which lifts the inside front tire off the ground. One raises that back up with EVO uprights just like raising spindles on a 911.

The other big variable is shock valving. Since shocks (dampers) play such a huge part in controlling and determining the RATE of lateral weight transfer, you can see this happening more with less-than-optimal shock valving. Properly adjusted professional grade shocks such as Moton, Ohlin or JRZ really go a long way toward keep the tires on the ground where they do you the most good,....

kary993

I will find some pictures of my car under heavy load in a turn, but as I recall there are none where the entire inside front wheel is off the ground. I drive my car hard on the track and so have some pics where there is daylight on the outer edge (half) of the inside front tire. My car sits pretty flat through most turns and understeer is at a minimum even in slower corners. I run Pirelli slicks and have around 3.5 degrees camber in the front. I have a cup suspension with TRG sway bars and run them looser than most.

I'll post some pics when I find them.

Nemick42

George,

Thanks for the description of your car's handling. I read down and saw Steve's post and have to agree with his comment on the dampers. I would think that stiffening the rear springs would tend to induce more over-steer, although a little more suppport from the rear anti-roll bar might be worth checking out.
Ultimately though, if you have the opportunity to try out a little more bump on the rear dampers, it might give you just a little more suppport.
Does your car currently have normal droop on the front suspension, or has it been limited by the dampers you are running?

kev

Glen,

Sure, send me a email. I'd be interested in any other parts too for the project.

Steve,

Thanks, your expertise is appreciated.