Rear Mounted Front Swaybar

[Philip Hehir]

Hi.

I was looking to go up in size on the front swaybar of my montreal race car but with enough weight up the front of the car I decided perhaps I should be fabricating a rear mounted chrome-moly tube with blades so I can tune it.

Not wanting to re-invent the wheel, has this been done before? I see from Google the Jack Beck in from Orion Engineering has done something like this but I’ve not see a picture of this. I’ve tried the search function on the AlfaBB but I got a heap of threads and the Alfa BB server is really slow at the moment to make it worth while trying to trawl through them all to see if a picture has been posted of one.

So if someone can either post a picture on this thread or feel free to email direct that would be appreciated.

Regards
Phil.

[la_strega_nera]

Mike Valant's old website had some great pictures - the mounting brackets bolt on via the steering box and idler arm box mounting bolts.
mikevalant.com

[Philip Hehir]

Where does the link attack onto the lower A arm? As the shock is on the opposite side to where the factory locating point is for the sway bar. Is a longer shock mount made to provide the attachment point or does it attach beneath the A-Arm under the spring pan?

[conedriver]

Philip,

Here are pictures of a Jack Beck rear mounted sway bar on a spider. A longer bolt (and spacer) is used at one of the lower ball joint mounting holes. Wheel offset is critical with this arrangement; I use 9.00 wide wheels with the inner rim edge in the stock position and must be carefull to eliminate interference with the lower bolt in the heim joint link to the A-arm when the steering is at full lock.

Note, this is not a blade-type design. The end levers are large aluminum bars; the sway bar itself is a 1.25 in. hollow tube, and tuning is done by changing wall thickness (these components are actually from U.S. style racing Sprint and Stock cars). Alfaholics makes a gorgeous blade-type swaybar for the rear. However, this is a much smaller (weaker) bar. I have never seen a blade-type bar for the front of an Alfa.

Quote:

Originally Posted by Philip Hehir Where does the link attack onto the lower A arm? As the shock is on the opposite side to where the factory locating point is for the sway bar. Is a longer shock mount made to provide the attachment point or does it attach beneath the A-Arm under the spring pan?

[gtv27]

what's the advantage with the rear mount bar (apart from moving weight backwards - although seems like a lot of effort for little reward in that respect)?

[conedriver]

I don't think the weight matters that much. However, the mounting is much stronger. The original Spider/GT/GTV front swaybars are mounted with narrow straps that are held by relatively small bolts threading into nuts welded on the inside of sheet metal frame sections. The Beck-style tubular sway bar is STRONG. This thing is 1.25 in diameter, and I'll bet would either rip the standard mounting straps out of their mounting holes, or break the straps outright.

Quote:

Originally Posted by gtv27 what's the advantage with the rear mount bar (apart from moving weight backwards - although seems like a lot of effort for little reward in that respect)?

[gtvpete]

I have obtained similar swaybar components as those depicted (hollow bars and solid aluminum alloy arms) for my ongoing race chassis build. The rear mounted bar presents a myriad of design problems that only start with mounting the bar to the chassis.

My biggest dilemma has been this: In order to clear the inner tire/wheel, the bar cannot protrude very far into the fender well. However, the mounting points for the arms on the lower a-arm must be sufficiently outboard in order to have an effective motion ratio. This necessitates a significantly bent arm. However, when i took the arms to my local fabrication shop they basically declined the job since the bend(s) would "stress and weaken the aluminum alloy, rendering them unsafe etc. etc. etc".

Since the depicted arms all seem to be bent, this seems to be less of an issue than these guys have made it out to be? Can anyone tell me if the arms are bent only once, just forward of the swaybar itself, or if there is an opposite bend near the end of the arm, creating an offset type design? Any idea of how sharp a bend has been accomplished in degrees?

Basically trying to get an idea of how far these can be bent before the material is really weakened beyond practical use?

[Philip Hehir]

Many thanks for the pictures and info gentleman.

I've decided that due to clearance issues (both ground and wheel) with a rear mounted bar and also the fact that a rear mounted bar might not be considered legal or at least looked at with a sideways glance at some race meetings, I've reverted to my plan to make a blade style front bar. This way I utilize the factory mounting points and with the future plan to get a COD ("Certificate Of Description" which is New Zealand's classic racing equivalent to "FIA Spec" with grades depending on how far you are away from FIA Spec) at some stage I'm best to keep everything within the rules or at least on the line. The main reason I don't have a COD yet is because of the EFI I use on the Montreal and I'm fairly sure I'd need to revert back to the SPICA or use carbs first to get a COD.

Anyway with a blade style bar I can also easy tune it as unlike you chaps in the USA we get rain here in New Zealand and I want to be able to soften the bar easily if the track conditions get damp. I've already come up with the design I want and passed this onto the machinist yesterday to knock up (I'm racing next month). I'll post a picture onto this thread as soon as it's complete which should be in a few weeks .

Regards
Phil.