Reason for no rear sway bar?

[DougM]

I am by no means a suspension expert so bear with me if this is stupid. Would there be any reason no to install a rear sway bar on a '71 RSR clone with all 930 suspension? My car was built by Dave White Racing for the previous owner and it just came to my attention that there is no rear sway bar. According to the receits, they installed the 930 arms and spring plates, TRG monoballs, new Bilsteins, but no rear sway. The fronts had adjustable TRG sways installed.

[Flieger]

Go for it as long as it is adjustable. It will help fine tune the chassis' handling balance through the twisties.

[joetiii]

Well. I guess it depends on how you drive your car.

As a "new" early 911 driver, my 69 was updated with new suspension components ie monoballs, bilsteins, adj spr plates, bushes and front adjustable sway, but no rear bar. My Pwrench wanted to have some understeer dialed into the car.

Well I enjoyed learning to drive a rear engine car for two years but when I started doing autox, the slow speed push was too much. I added a rear bar two months ago and the car is transformed. Much more neutral at mid speeds and it pivots better around tight corners. When I get off the highway now, the rear feels lighter into the off ramp but I'm accustom to braking first and accelerating thru the turn.

[DougM]

What would be the advantage of no rear sway? The PO spent lots of money having this car built. I can't see why it would be finished without a rear sway unless there was a reason.

[Zeke]

I had a rear sway link jump off the ball pivot during a high speed run in the twisties. The guy behind me thought I was some kind of hero driver catching the car at each corner. I told him I was hangin' on big time.

I didn't know what was wrong until the next day.

[FPB111]

Ask Dave White Racing or the PO.
No rear sway bar would make the car tend to understeer. Rear engined cars tend toward oversteer. Perhaps the PO was concerned about 911 reputation for "snap" oversteer?

"Understeer is when you see the car hit the tree. Oversteer is when you hear the car hit the tree." (That is a quote but I cannot remember who originally said it that way.)

[mph911]

Im running completey stock torsion bars, shocks etc with a small 13mm front bar and no rear bar. It does push/understeer a bit, however it is fun steering on/off the throttle. I shot this video the other day, you can get a fair idea of the handling....

http://www.youtube.com/watch?v=Xt1US87H5Us

An adjustable rear bar on your set up could be tuned nicely.

Matt

[gestalt1]

you might also want to check the torsion bar sizes. typically there is about an 8mm difference from front to back on cars with upgraded suspensions. it is possible the rear torsions are larger than normal and they are taking some of the function of the absent rear sway. theoretically a front sway could be used as a under/over steer balance adjustment and the torsions used for pitch control in all directions (left/right and front/back). i am thinking of trying this on my 68 because there are no mounts for the rear sway and i'd like to get a really good front with the money saved from not investing in an additional rear sway. just a thought.

[Zeke]

My '71 at Willow. 19mm sways front and rear. Never any wheel lift. I prefer the way this car handled to the one in the video. YMMV.

[mph911]

Quote...My '71 at Willow. 19mm sways front and rear. Never any wheel lift. I prefer the way this car handled to the one in the video. YMMV.
Hey Milt, I wish my car handled like your 71', thats what Im aiming for. Even though its fun to drive and Im learning the limits, Im ultimately after quicker lap times. My car is only putting out nearly 110 hp. When funds allow, my suspension is first on the agenda. BTW, nice pic.
thanks Matt

[Chuck Moreland]

the advantage of no rear bar is weight savings. It is possible the car is setup with very stiff rear tbars instead of a sway bar. Or perhaps the car has other mods that balance the handling. Or it could be the car understeers like a pig, you didn't say.

I don't recommend running without a rear bar. An adjustable rear bar creates an easy and effective way to tune the balance. It is more effective than an adjustable front bar.

[911st]

I am not a suspension expert either.

I do know of a local narrow body that was built to 73S specs with the typical 22/28, 22/22, that ran 205/15 Hoosier slicks.

This guy was an instructor and always the fastest car in class and often faster than most of the big cars. He typically ran with out the rear bar hooked up on the track and hooked it up for autoX.

He had a lot of front tire being a narrow body. Softening up the rear will make it stick better.

The rear of a 911 has about 50% more weight on it. What I was thinking is if you can get 100% of one front tire's traction, 100% of the outside rear tires traction, and 50% of the inside rear tires traction, that would be a balanced car.

An added advantage might be that the rear suspentin will be less upset with bumps not having any sway bar as load is not transfered to the other wheel.

I suspect a lot of people do not have there front suspention set up righ to begin with. The rear gains some neg camber with compression and can get a fair amount to begining with. Most lower there front a bunch which puts it at a point where it dose not get any camber gain under compression. I think the front needs the spindle rased to put the a arm back in a position to contribuit neg camber gain with compression. I think we might need more neg camber dialed in up front to get the bite it needs. Otherwise we might be working around another problem.

Dose any of this make any sense????

[DougM]

I guess with the suspension of a 2900# car under a 2300# car running 285 rear rubber and 245 front, it would handle well at the track? It was built with the intention of running DE at Sebring, not Auto-X.