Help With Sway Bar Selection
 

This last weekend I took my car out for the first autocross event of the season. This was the car's first outing of any kind since a complete suspension rebuild, which included coil overs all the way around, replacement of all rubber bushings with spherical bearings, Elephant Racing's ASP spring plates and big brake upgrade. This was followed by a corner balance and allignment aimed toward track days rather than street use.

Overall, the car did great, however, I am experiencing a noticeable amount of understeer out of corners and the car does not turn in as quickly as I would like. All that leads me to believe that it is time to do the final phase of the suspension upgrade and install new front and rear sway bars (the car has the factory bars on it now). A friend of mine loves his Smart Racing sway bar set up, but those are no longer available.

Can anyone suggest a sway bar set up that would allow me to dial out the understeer. The car is a 1975 911 and weighs just a little over 2400 lbs. Many thanks.

What size tires are you running? My experience (YMMV and all that) is that slow-speed understeer is hard to get rid of. I found that my understeer decreased as front tire width increased. I've run 185, 195, 225 and 245 tires in the front and with the 245s, low speed understeer is greatly decreased and turn-in is awesome. I've had lots of different sway bar combinations and honestly never noticed extreme improvements in balance/handling. Obviously, you need to balance the car with rear tires. Before I flared my '76, I ran 225/50-15s front and rear and that actually worked pretty well.

Believe it or not, factory Carrera 22/21mm bars work really well, but it sounds like you've looking for something fancier (and more adjustable).

What spring rates did you go with and what size tires are you running?

Scott

I am running 295/30/18 Michelin PS2s on the rear and 225/40/18 PS2s on the front. The spring rate is 600 lbs in the rear and 400 lbs in the front. The shocks are ER's Von stage 4 coil over inserts.

I bought Smart ARBs from Steve Weiner @ Rennsport Systems last summer. I believe they are still availble.

Ditto. I got mine in November.

Just got a set of the Smart racing sways...they are definitely available.

I also think they are available. I believe they have just switched to a wholesale business model instead of direct retail sales. I also think they are looking art retiring the Smart Racing name and putting it under the Jerry Woods Enterprises banner of products instead.

Elephant also has a selection of adjustable 911 sway bars

Thanks, I will give Steve a call.

Does anyone have any experience with the "blade style" sway bars being offered by Elephant Racing. They are more expensive than I anticipated and I am wondering if they are worth the money. Thanks.

The feature of the blade style is that it can be cockpit adjustable while driving the car

I think I have a set of factoy carrera sways that you can have...have to check (they may be SCs). Probably cost more to ship to Cali than they're worth. Like IROC said they are an inexpensive soltion and work pretty well on lighter old cas.

Have you tried increasing front tire pressure/decreasing rear?

Whoa...just saw...225's on front 295's on rear? I think that may be a big part of your oversteer issue. That's quite a diffeence.

yeah, I think you would want 245 fronts as a minimum

Unless you have a mountain motor, I bet if you dropped the rear to 265 or even 255 your car would be waaaaay quicker on the autocross course. I doubt you can get a 245 under the front unless you have flares.

Yeah, I am aware of the differential between the 295s and the 225s, this is a remnant from the previous owner's set up. The problem is that I simply cannot fit 245s in the front without having some serious interference issues, and currently I am not in a position to pop for a new set of wheels and tires which would be better suited for the car. With that being said, I am running a 3.6L V-Ram motor so the car is making respectable power and the extra rubber in the back has been helpful in that regard.

I did speak with Steve at Rennsport a couple of times earlier this afternoon and he confirmed that the Smart Racing bars are still available, although on back order. He suggested that I try and fit a set of 235s in the front and try and dial out the rest of the understeer with the sway bars. I will do a couple of events with that set up and see where it takes me (I don't want to do too many changes all at once, I find that it becomes more difficult to tell what is making things better and what is not making much of a difference or actually making things worse).

If the larger front tire and the bars don't do the trick, I will probably try and get some additional front camber by using some of ER's offset front ball joints.

Lots and lots of ways to tweak a car the way you like it without going through the expense of new sway bars.
Smaller rears or increasing the stiffness of your rear coilovers will help, and one of those options is free.

http://forums.pelicanparts.com/uploa...1363740346.jpg

225s are your problem. Typically the front rear ratio for best handling, dialing out the understeer is at least 0.85-0.89. You need at least 235s on front, but better is 245s. Your ratio at 0.76 is just too wide. You can fidget with sway bars to make it feel better with initial turn in, but as soon as you gas it, you will push badly as it becomes a three wheel car when the inner front wheel has no load, and only a 225 to steer your car while you have 590 amount of rear rubber to deal with. The Smart Racing bars are awesome but with what you have, if you were to get some big bars such as the 31s/27s and set the rear really stiff with the fronts soft to get yourself more oversteer, the window of operation for throttle steering and a countersteering drift would be much narrower and you could transition into snap oversteer if the inside rear wheel lifted in an abrupt AX transition.

A car is much easier to drift and throttle steer if you had more front tire, set the front bar stiff, allowing you to use throttle to be able to lift the inside front with gas, or plant it with throttle lift giving you that instant transition from slight understeer to countersteering oversteer, and set the rear sway bar on a softer setting, which plants both rear tires under a larger window of conditions, giving you great grip and stability in the rear. Your car will be faster out of turns because you can gas earlier and harder into and coming out of turns without worrying about the front pushing out.

Excelllent description...
 

Damn, I almost wet myself.

Good description of the dynamics, I had old 66 911 that went three wheel tooo easily.

chris

Tony - did that co-driver help pay for some of that rubber you wore off Saturday? SmileWavy