Front Anti-Sway Bars

[Flieger]

So I got some 22mm hollow (about 25.6mm OD with plating) Tarett sway bars. Today I took out the 22mm solid (about 22.2mm OD with plating) bar but it put up a good fight. I always thought it looked very close to the fuel tank on the right side of the car (right side when viewed from driver seat). It looked like it was scraping a tad but there are/were so many other noises in my car that I couldn't really tell. Then I tried putting in the Tarett bar. It wouldn't fit. The holes in the chassis were a few tenths of a millimeter larger than the sway bar, but the bar could not go through both holes because it was hitting the tank. I did not want to use a hole saw or file or anything like that to ruin the nice rolled/flared edge that is currently there, but that would be one option- enlarge the hole. I loosened the tank mounts and was able to nudge it forward just enough to get the bar all the way through the car, but it was scraping obviously on the tank so I removed it again and have left the job for another day.

I have a feeling that my suspension pan has been replaced, maybe at the same time as it got converted to short-hood. But I think my tank is also the later space-saver type. It seems to either have a bulge on the right side (there is plenty of clearance on the other side) or else the tank is crooked.

Now, I would not be adverse to "clearancing" the tank with a big hammer, but I would want an expert like TLG to do the clearancing.

I can do without a front sway bar, but I would like to have an adjustable one to fine tune the handling. So, are there any adjustable sway bars that have stiff bushings like the Taretts but are smaller- like 15 or 16mm? I think Ira's 19.3's are the same OD as the 22's with just a larger ID.

[jameshtaylor]

Max,
Is doing your adjusting at the rear an option? Also, I have the 19mm Tarrett (rear) which I'll be happy to measure for you if you'd like.

[Flieger]

Yes, please measure the rear bar. Ira's bars are the same front and rear. I suspect it will be a 1" OD as well.

My ultimate goal is to run with no rear sway bar, as it is very low to the ground and I run the risk of breaking the mounts if it is too stiff That already happened on one side. The side that broke (passenger) side was reinforced but the side with the fuel pump mount is not, because of that fuel pump. I suppose it would be an upgrade to move the pump to the front, but I'd like to be able to do the suspension nicely before Parade and the fuel pump some other time. The 22 front bar (or even the 19) is just too stiff to use without a rear bar, unless I had coil-over springs or maybe the biggest torsion bars that Elephant Racing makes (with their quick-change spline setup).

So, I would like to run just a front sway bar to take a bit of weight off the back of the car, gain some ground clearance, and not have to worry about breaking the mounts. A further reason for using a front bar only is that I want the rear ride frequency (before considering damping) to be higher than the front so as to give a more level ride. This means going down on the front torsion bar size, up on the rears. This then makes the elastic roll stiffness distribution too far rearward, requiring a little bit of front anti-sway bar to correct.

I can run 22/31 and get a pretty good roll stiffness distribution (5% more forward than the weight distribution) but something like 21/31 would be more balanced, but then my front frequency is a bit higher than the rear, and I also wouldn't be able to tune the balance depending on what my tires need for the best grip, and what I need to get the most out of my open differential (in the future when I get it out on the track). I could maybe play with roll center heights (ride heights) but that basically means raise the rear and so raise the cg. I could also accept the undamped front frequency being higher than the rear, but make sure that the front damping ratio is closer to critical than the rear is, thereby giving me a damped rear ride frequency greater than the damped front ride frequency. I have no idea what my dampers look like in terms of force vs. shaft velocity, however. I suppose I could get a rough idea by bouncing the car.

[jameshtaylor]

Ira's 19.3mm equivalent bar measures 0.878" in diameter. That gives you another .06"/1.5mm clearance. In addition, putting this bar in his standard mount requires use of two shims which look about 2mm or .08" thick. If you placed these at the front of the mount, you might pick up that amount more clearance, giving you about 0.14" more. Enough? (No, sorry, that's wrong. The shims only position the arms on the bar, their position has nothing to do with the clearance issue you face. So 1.5mm is all you get I think.)

[Flieger]

Thanks. That would put me back to where I was. The Weltie was rubbing a bit I think judging by the look of the bar. But I did manage to pull the tank forward a tiny bit, so using that bar size might just do it. I'd still like to "clearance" the tank in my car (it is a later tank).

This does give me some things to consider, though. I will still need a rear bar with a 19.3mm front.

[Flieger]

Well I took the rear bar off today (took less than an hour and did not even require taking the wheels off!) and I like the way the car handles. Much more stable when I give it a sort of slalom input. Before I could feel the rear starting to get out of phase but now it feels planted. It does roll a little more and I can tell that it takes just a little bit longer to transition, but the ride is much better over bumps and the extra stability is nice.

I don't have good measurements for front unsprung weight or the some of the rear sway bar dimensions, but I think I changed the roll stiffness distribution from about 51% front to about 48% front. Going to 31 in the rear like I am planning to (bars are on order from Pelican) will give me about 42% front, which is about 5% more than the weight distribution, which is what textbooks recommend as a starting position for neutral handling (I think they assume equal tire sizes though and I have a bit wider rears). The longitudinal ride quality (pitch) wasn't bad, so it might not be such a big deal to have the highest undamped ride frequency in the front instead of the rear.

[Flieger]

Anyone want to trade an unused 22mm RSR style front bar for a 19.3 Tarett (preferrably RSR style) front bar?