Why can't I keep all four down?

[Jack Olsen]

I'm looking for some suspension advice. I've got 21/30mm torsion bars on a pretty light car, along with 22mm front and rear adjustable swaybars.

A picture is worth a thousand words, right?

Well, here's a million words:

[Jack Olsen]

And hey, here's one of Pelicanite Tyson Schmidt mixing it up with MMarsh:



All their wheels are down!

[Bill Douglas]

Jack, nice photo's, the car sure looks good! Thrashing Tyson nicely too

[tmctguer]

i've been told the same thing about my bone-stock '73............i get air on 1 tire around some corners. i think it is cool.

some day, i'll get a new car that stays on the ground. until then, i'll keep going around corners on 3 wheels !

[widebody911]

In that first pic, you're either apexing *very* late, or taking a different line than the S2000 altogether....

21/30? That seems like a big spread. I'm running 22/29 and I could still feel the inside wheel getting light. Couldn't tell if it was actually getting off the ground.

When working the autocross course, I'll see the inside wheel of the well-prepared 911s come all the way off the ground and stay there long enough to stop rotating!
Increasing your track would probably help.

[marcesq]

Jack:

The problem is that you are not leaning into the turn enough. Your head is only slightly bent in the pictures. Could'nt pass this one up . . . sorry.

I wish I had the knowledge to help.

Regards.

[Early_S_Man]

Jack,

I recall seeing a few notable drivers like ... Dan Gurney, Mark Donohue, Peter Gregg, and even Richard Petty up on three at Riverside's Turn Nine over the years in Autoweek!!! Pretty good company, if you asked me!

And, my most memorable shot of Richard Petty 'herding' a 3800 lb '71 Plymouth Road Runner around a corner on three wheels ... seems to defy the laws of physics, yet he won the race! Take that, Mr. Puhn!

So, Jack ... join the winners! And, don't worry about the 3-4 wheel argument.

[5axis]

How flexible are the early car tubs? Could all the mods be approaching this limit? I am guessing that you are a long way from the chassis of a GT3 Cup car but not that far in terms of power. Cage and tube time?
UN-SWAG from the peanut gallery

Looks like great fun anyway

[Tyson Schmidt]

Front swaybar too effective, rear bar not effective enough.

Although Jack, a little bit of lift is just fine.

I'm not lifting my inside front wheel because my suspension is totally stock. Mush. 20mm front bar, 21mm rear (which I found out in a Tech bulletin is rare. The 21 rear that is.) And worn-out standard Boge's.

And, well, Mike's not in the apex yet in that picture.

And Bill Douglas? Thrashing Tyson? I don't think I was "Thrashed"!
(Come on Jack, stick up for me!)

[orbmedia]

To get that front wheel down reduce the stiffness on the front anti-roll bar or increase the stiffness on the rear one, assuming they're adjustable. Your front roll stiffness is too high. Be aware you will be dialing out steady-state understeer.

[Jack Olsen]

Thrashing Tyson nicely too.

That's Mike (MMarsh) and Tyson in the last picture. I'm probably a couple of laps behind. Tyson was in the only 'bone-stock' 911 of the three of us, and with more weight, less brakes (his rotors were warping), and a softer suspension, he was doing very well. In an apples-to-apples match, with both of us in my car -- as is coming up for the Open Track Challenge -- I have little doubt that Tyson will turn the faster lap times. The kid's got great instincts and a lot of solid autocross foundation.

There, Tyson, how's that?

In that first pic, you're either apexing *very* late, or taking a different line than the S2000 altogether....

Thom, in that first picture, I think I may be in a full-on broadslide. But it was the one shot with the highest lift. Toward the end of the second day, my driving was getting pretty wild. I ended up with no pads whatsoever up front, and had to make the 5-hour drive back with only downshifts to slow down and the handbrake to stop.

And Marc, you're probably right. If I just slammed the helmet into the side window a few times, I could probably bring that wheel back down. What is the human instinct to 'lean into the turn,' and how do I get rid of it?

And Warren, if you say it's all right, and Mark Donohue did it, then okay, I'll stop worrying so much. I'm going to tighten up the rear swaybar a little before my next track event to see how that effects handling.

5Axis, the early tubs are more flexible, and it at least felt like the new 80% limited slip was just twisting everything as it pushed the car through that very tight turn before the main straight. We'll see if a few ajustments to the swaybars, and the addition of a camber brace makes a difference. If I go to an RSR configuration with 9x11x17 3-piece Fuchs, the track might widen out enough so that the point is moot and the wheel lift is history. It does make for pretty interesting looking pictures, I'll admit.

Nice pitures. I think it's a common thing with 911s. Look in your old car magazines and Porsche books. Lots of similar pictures there. Both road cars and track cars can be seen doing this.

Jack, if you put 17inch Fuchs on your BlackBeauty it will simply look wonderful. I can't wait to see the pictures you'll be posting when the wheels are on the car

BTW has anybody ever seen or heard about one piece 17 inch Fuchs??? I have a picture with what looks like one piece 17 inch Fuchs on a killer look swedish 911? Pic too large to post

[dickster]

wow, the car looks great!! in its element.

its normal for touring cars to raise that wheel isn't it - i don't think its a problem. it seems to be the result of less body roll, stiffer setup. the other black 911 (130) looks to be rolling alot more, so is probably set up softer!!

anyway you're in front!!

the dickster

[chuckr]

I have seen this many times, it is the car, even with a cage this will still happen, though a full cage will keep this to a minimum.
It is called body flex,I kinda like it, makes things fun ! looks like you were having fun.Sounds like you have a good set-up, so if this is the only "problem" I do not think you have a "problem"

[jluetjen]

Jack; I'm not sure I understand what the problem is? How were your lap times on the laps that each of those pictures was taken? That will tell you if you have a problem.

Cars pick-up wheels all the time when raced on the track, it is not necessarily a problem. For example, Stock Cars (Both WC and BGN) will almost always lift a front wheel while climbing through the esses at Watkins Glen. The cars are neither flexible nor slow. I have a great picture of Tom Gloy in a GTO Mustang at Sears Point with both right side wheels off the ground. In Starkey's book "R-RS-RSR" on page 104, there is a great picture of John Fitzparick in an RSR at Dijon with a wheel just lifting off the ground. VW Rabbits will routinely lift the inside rear wheel off the ground in corners and will still beat lots of other cars around the track which have all 4 wheels firmly on the pavement. The ONLY time that lifting a wheel is a problem that I know of is when the wheel is one of the driven wheels and the car has an open dif. Then all sorts of time is being lost.

The reason that some cars lift wheels and other don't has to do with the location (Laterally and height) of the center of gravity, the relative stiffness of the sway bar and shock settings front and rear and the stiffness of the chassis.

CG Location: Formula cars and sports racers rarely lift wheels because the CG is usually close to the center of the car and relatively low. In the case of Touring Cars/Sedans, this is not the case. More so in the case of the 911 since the engine is at the back of the car and relatively high (compared to a formula car). When cornering, this creates a long lever that tries to yaw/roll the car against the suspension.

Sway Bars: Porsches generally run with fairly stiff sway bars in the front compared to the amount of load in the front of the car. This is done to help control inherant "looseness" of the rear engine configuration. By running a "stiff" front bar the yaw and roll force I mentioned above is transferred from the overworked outside rear tire to the relatively lightly worked outside front tire. A side affect is that the inside front wheel is pulled up at the same time by the sway bar as the bar transfers some of the rolling forces to compressing the inside front spring. Shocks can have a similar affect while transitioning into a corner if they are stiff in rebound.

Stiffness of the chassis: Actually I disagree with Chuckr. Flexible chassis (by this I mean the structure as opposed to the suspension) are less likely to pick up a wheel. This is because the chassis flex will absorb the twisting forces created by the sway bars and make sway bar adjustments less affective. This is why chassis designers are always trying to make the frames stiffer. Furthermore, this chassis flex is undampened (in other words there is no shock controlling the flex) which makes it a bit of a random element when tuning the suspension. Flexible cars are evil to try to tune because nothing seems to make a difference. This generally does not seem to be the case with 911's.

The bottom line, lifting a wheel (or even two on occasion) is not a problem! Slow lap times are a problem. If you are getting fast times while you lift a wheel -- that's great! If you are slow because your car is pushing AND it is lifting the front wheel, then your car is most likely too stiff in front and/or too soft in the back because you are overworking the outside front tire. Then getting the inside front wheel on the ground might help improve the front end grip. But that is a rather special case. You will need to evaluate the specifics of each case and make a determination about what to change: LSD, Springs, Shocks, Bars, Tire Pressures, Alignment or Aero. Each will have a different affect on the problem. If you were lapping faster then the other guys, I'd keep talking out loud about lifting the inside front wheel while doing nothing about it. If you are lucky, the other drivers will all be out softening their front end trying to catch up with you!

BTW: Carroll Smith has an excellent Handling Cause/Effect cross reference in "Tune to Win". I believe that it is essentially the same thing that he recently published in a pocket book. Your pictures are interesting because your car seems to be a little loose in the first picture and picks up a push in the later pictures. Are they chronological? This could be either driver induced or the result of tire wear or fuel burn-off. If your car is prep'd to "Stock" rules, there may not be much you can do about it but learn to drive around the issue.

[Will]

I agree with John, it's not a problem. There's no weight on that wheel, so it doesn't matter that it's not on the ground. Stock Golfs and Jettas have been lifting their inside rear wheels for years, and not even Consumer Reports can find a reason to complain about it.

Will

[nostatic]

well, since it is the left front tire in each photo, obviously the problem is with the tire. Get a higher profile tire for that wheel. Maybe a Firestone Wilderness AT. I hear those are great in high-g situations...

[724doorE]

Well said John L. Those old books are tops. Find some old photos, I seem to remember many pics of Nick Frere (spelling) and Jofn Fitzpatrick with that wheel so high I think it could clear a 12 oz beer can! But seriously its nothing new

I also seem to rember reading somewhere some bragging about the 73 rsr. I think they said you could litterally run Lemans with five tires and the fifth was for the left rear(only one changed) since they go clockwise. This would seem to support John's knowledge pretty well as he said the left rear was the one you want to remove loading from and send to the left front while the right front skies.

This right John...

BTW if the King could sky a cuda front wheel, its only fair his son would admit he loves driving 911's at the 24 hrs of Daytona!
Dennis H.

72 911E

[Superman]

I'd like to agree with your conclusion that Tyson has tons of AX experience, but it's just not true, according to my belief. Tyson exploded onto our local AX scene last spring and has been kicking asses and talking names ever since. He was in the hunt for first place in a very competitive group. It came down to the last AX event and it was anybody's game to win or lose, among three or four gladiators. Tyson did not emerge victorious, this time, but he is competing with at least two very serious drivers and machines. I'd agree his instincts are a cut above those of ordinary race enthusiasts. The kid's got talent.

[emcon5]

Nice pics Jack.

There is a good picture in Vic Elford's book showing a 911 on 3 wheels, followed by some small sedan on 2 wheels.

Tom