rear sway bar?

[ericjon262]

My 85 has an 88 rear cradle, but I never have had the rear swaybar on it. is it worth trying to find one (or a swaybar period) and install it?

for reference:

85 SE

Front:
Will's Anti dive setup
Spherical bearing LCA's
poly bushings in the UCA's
stock springs
Koni Reds
2" drop spindles
addco(?) heavy duty front swaybar

Rear:
heim joint lateral links
rubber bushing trailing links
KYB struts converted to coilovers
unknown rear spring rate

I don't have any of the brackets for a swaybar, but could easily enough whip some up.

[neophile_17]

Hello Eric,

This is a matter of taste but I would want one on that setup. I'll describe our preferences and setup as a reference point. Hopefully this will help you decide where you want to go. We are (hopefully) out on track for a full day going wheel to wheel with drivers of varying skill levels. This has led us to a pretty neutral handling setup that leans toward understeer. We have stiff springs and smallish bars, stock front and 10mm rear. You have a bigger front bar so ~13mm in the rear would balance similar to our setup. I really like the sway bar link style Honda and several other Japanese companies use. There is no lash or bind and they are available at any parts store. Good luck with your decision.

Sam

[draven]

If you aren't running a stock sized muffler / stock location (i.e. tight against the rear cradle) definitely consider building your own. Speedway motors has quite the selection of DIY sway bar rods, arms, and pillow ball mounts.

The OE rear sway bar has a ~1ft "kink" in it to fit in front of the muffler. I still may go aftermarket eventually. Let me know if you need pics while my cradle is still out of car.

[eHoward]

Full disclosure, I've attended a number of vehicle dynamics classes, but never really saw it presented this way, where it makes most sense to me in my mind so this may be completely off the mark.

If you think of the anti-roll bar as a spring that only works in one axis of the vehicle...

And if you look at the length vs width of the vehicle, there is generally more length which would equate to needing less spring in that axis. The reason why you don't see anti-roll bars running front to back is you do not need additional spring front to back. You size the springs for that axis.

You do need additional spring left to right typically in the form of the anti-roll bar because that width is shorter given you have a spring that is optimal for the length of the car and assuming a tire generates equal max Gs in all directions. That is where the anti-roll bar helps add additional spring.

Therefore if you have a roll-bar on the front axis and don't want to be bouncing off of bump stomps unevenly (fore/aft) mid corner, you're typically going to need some amount of an anti-roll-bar in the rear. It will likely be a smaller in the rear bar due to trail braking (braking into a turn) and preferences in at the limit handling where you don't want the back to come around front erratically.

If you simply size the springs so they work left to right and scrap the bars, the ride will be harsher than it needs to be.

TL/DR: If you want to take turns at the limit of traction, you'll probably want bars on both ends. If you're mostly interested in highway driving or quarter mile (straight line), it's probably unnessesary to add.

[ericjon262]

Thanks for the replies, at this point, I drive the car alot, but if I can make it corner better with such a simple add on, then I don't want to leave that off the table.

[Jalisurr]

As a counterpoint, if your rear springs are stiff enough to provide the desired handling characteristics, having no rear sway bar should give you excellent traction on the exit of a corner. More bar is not necessarily better, it should be used as a tuning tool to adjust the handling balance of the car.

On a track car, having very stiff springs and no bar might be ideal, but it would make the ride very harsh. That might not be acceptable on a street car, so you'd have to compromise.

[The Dark Side of Will]

Steven has ~450ish rear springs, and still added a bar. Also has 275 width ~200TW tires.

The stock Formula setup includes a fairly large front bar and the stock rear bar along with (I think) the same springs as every other '88 has. The rear springs are slightly softer than '84-'87 stock springs (150 and 170?). With Konis and spherical bearings, it handles quite well on stock tire sizes. It can still lose the tail first because the rear tires are fundamentally overloaded due to the car's weight distribution.

As you widen the rear tire, the rear grip goes up. You need to stiffen the rear suspension so that at the higher lateral g, the "natural roll" of the rear suspension still equals that of the front suspension.

[pmbrunelle]

It seems to me like sway bar tuning is done at the very end, once everything else has been selected.

[ericjon262]

Thanks for the replies, I'm going to look into it a little further and see what I can come up with.

[zok15]

If nothing else, the way you can tune the rear of the car to behave how you want is worth having a rear swaybar. I have messed with rear sway bars on a bunch of different vehicles to dial out factory understeer, and my friend who races spec Miata does a lot of adjusting of his rear sway bar depending on the track he is racing that day. Anecdotally, a stock front bar on the rear of my 85 made the front end change direction much faster without making the ride any harsher (I have 350# springs in the rear). And as stated above, if springs are stiff enough to control roll, you will sacrifice traction over less than smooth roads, as well as ride quality.

Subaru's front swaybars use a slick double ball joint link that is another option if you are going to adapt something yourself, and they are readily available to buy in stock at stores/dealerships. They are pretty short, maybe 3-4 inches pivot to pivot, but just another option if you are looking for off the shelf parts that work for whatever you end up doing.