Rear Swaybar Mount

[eliminator]

This shows the position of the rear swaybar and the swaybar ends in realation to the right and left hub carrier. I bent my sway bar to give me the clearance shown from the end of the sway bar to the hub carrier. I can easily get the bolt out and make adjustments in this position, (normal ride height). This also shows the upgrade to poly bushings instead of the rubber bushings.

[davebetts]

Thanks for the excellent photos. I just asked Alan (yesterday) about this and what it would do for handling.
I race with Hooziers, Street TD's and both the outside and inside tread edges are worn with lots of tread remaining on the center area. Hoozier person said to start at 22-24 lbs of air and the ideal hot tire pressure is 28 lbs. That's what I have after some laps. Do you guys think the car is just leaning that much in both directions and will the addition of the rear sway bar help my handling and tire wear?
Any thoughts?

[eliminator]

Dave,

I don't know how you could drive these car's in an aggressive manner without a rear swaybar. So absolutely it will help and it will be very noticeable.

My recomendations, take the 3/4" FRONT swaybar and put it on the rear, on a Unique they are interchangeable. Then buy a 7/8" swaybar for the front. Use poly mounts on both, throw the OEM rubber mounts away. Now you have a different animal for track events.

The Unique swaybar is from a early MGB front sway bar, 1973 and earlier, and are avaliable from several companies.

[Brent]

Rick,

You have one of the nicest, most sorted out, cleanest Unique cobras ever built. It is impressive how well you maintain your car and how many things you have changed. Your car should be the Unique 427 ad and poster car. They should re-do the website on the 427 car and use your car for everything!

I do think you have O.C.D. !!!

The garage looks way too clean too.

[eliminator]

Brent,
That will get you 2 drinks on me......
Thanks for the compliment, there are some other nice cars out there.
I just like taking the basic car and seeing what I can improve on, that's the fun part for me after the build.

[davebetts]

Why do you recomend a thicker (7/8") bar for the front?
The balance on our Cobra is 47% at the front wheels and 53% on the rear wheels? Cobra weights 2645 lbs with 1/2 tank of gasoline.
I really appreciate your input. I am swicting from road racing to auto cross and I would like more control, I've got more power than I could ever need. And truth be told, I'd like to kick some Corvette butts, I'm getting killed as of now.

[Tony Radford]

Rick, do you have to drill and tap the holes in the frame to accommodate those straps that hold the bar? I'm getting ready to do the upgrade on my car. I don't think replacing the front bar to one of greater diameter is an option for me since it would already be hard to get a feeler gauge between the bar and my Spal fan.

[eliminator]

The 3/4" sway bar is plenty for street use, I have a 3/4" on the front and rear. The larger the sway bar the stiffer the ride. I just have heavier springs on the front and rear. I also have the Billstein Racing Shocks and I can change the nitrogen filled pre-load on them for additional tuning.

My car was ordered with a rear sway bar so the threaded inserts were welded into the frame. I am not sure drilling and tapping the frame will work, there is a heavy load on the sway bar bushings. I would have the inserts welded into the frame, 5/16 - 18 will work.

Here is agood article on sway-bars.

"When it is time to install a sway bar, you first need to chose the correct size, then do a proper installation, and maybe also do a little fine tuning to suit your personal preference and driving style. To this end it will help immensely if you understand how the sway bar works.

A single sway bar does not change weight of the vehicle, nor front to rear weight bias, nor left to right weight bias. What it does do is to reduce body roll (improving steering response), make tires stand up straighter, and change weight distribution from corner to corner. Making the front sway bar stiffer adds weight to the outside front wheel while reducing weight on the inside front wheel, and vice versa at the rear. For example, in a right turn it could add 100 pounds to left front and right rear while reducing 100 pounds at right front and left rear.

The secret to "adjusting" oversteer/understeer with a sway bar lies in how tires work. The relationship between lateral grip and load is the coefficient of friction. Stickier tires have higher friction and produce higher latteral grip. Lateral grip for a tire increases with weight loading, but is not linear. Increasing load on a tire by 50% may only increase lateral grip by 30%. This represents a reduction of grip efficiency. That is, if you overload one tire by reducing load on the other tire (on the same axle), the total lateral grip is reduced.

The sway bar takes advantage of this principal by transferring weight from corner to corner, thereby increasing total lateral grip at one end while decreasing total lateral grip at the other end. By adjusting stiffness of the sway bar you can adjust the relationship between front and rear lateral grip, thereby adjusting oversteer/understeer. But this only works when all four tires are on the ground, and weight distribution is close to optimal.

When the car is carrying one tire in the air you are on a tricycle, and the sway bar has nothing to do with weight distribution. With half the weight of the car on one rear tire you will have reduced grip efficiency at the rear, and the tail will swing wide in a hard turn (whether you like it or not). If you lift off the throttle at speed the car will likely swap ends (unless you are very adept at driving sideways). It is tough to drive a car in this condition, and not the fastest way around the track.

Additionally a large amount of body roll will tilt the tires so they will tend to roll over a bit onto the sidewall, chewing up the outside shoulder of the tread, and lifting the inside third of the tread width off the pavement. This also reduces grip efficiency by overloading part of the tread while unloading another part of the tread. This affects the front tires (due to kingpin inclination) much more than the rear tires (on solid rear axle). Excess body roll then spoils grip at the front more than at the rear, leading to the characteristic low speed push or understeer with no sway bar, up to a point.

In a fast turn when the rear tire finally lifts off the pavement grip efficiency is reduced dramatically at the rear, and you get a sudden (and maybe unexpected) transition from understeer to oversteer causing the tail end to swing wide. This gives horrible oversteer going sideways in fast turns and doing dramatic (and increasing) tail wagging in slaloms and switchbacks.

Starting with the case of one rear tire in the air, increasing front roll stiffness will reduce body roll, bringing the rear tire closer to the pavement, and improving tire grip all around (especially improving front grip and reducing understeer). Once the rear tire is in contact with the pavement the roll bar can begin to affect weight distribution. Going stiffer up font, reduces weight differential at rear and increases weight differential at front, improving grip at rear while spoiling grip at front. This further reduces the oversteer problem, getting closer to neutral steering that is the holy grail of high speed road racing.

If you go too stiff up front you reduce front grip to the point of inducing high speed understeer. This is not terribly bad for a street car. If you do something stupid at speed the front end will drift to the outside of the turn. If/when you then (instinctively) lift off the throttle, the deceleration will transfer a small amount of weight forward giving better grip up front at the same time as the car slows down, and it will turn in and stay on the road (very civil, nothing dramatic). But this is not the quick way to go racing.

For fastest top speed potential around curves you need close to neutral steering. For quickest turn in for tight corners at autocross you can use a little bit of oversteer. It may also be advantageous to be able to adjust the amount of oversteer depending on track configuration. To do this you need to be able to intentionally induce oversteer, and then you can decrease oversteer as needed (or as desired) by softening up the front sway bar end links. This is where the 7/8" bar is nice for competition (but a bit much for street use).

If you start tinkering with the suspension geometry for serious competition, you might install stiffer front springs and/or softer rear springs, which has much the same effect as a stiffer front sway bar. In that case you can use a smaller sway bar. If you lower the ride height the center of gravity gets closer to the pavement, also reducing left to right weight transfer and body roll, and you might use a little smaller sway bar. If you want to reduce body roll independent of corner-wise weight transfer, then you need to increase roll stiffness at both ends at the same time. This requires stiffer springs at both ends, or increased sway bar at both ends, in which case you also need a small rear sway bar, but only one bar front or rear needs to be adjustable.

A softer tire gives larger footprint and better grip, as long as it keeps the tread fairly flat on the pavement. Too little pressure allows a tire to squirm and roll over on the sidewall reducing grip, so there is an optimal tire pressure for best grip. When you have all four tires giving best grip, the way to adjust oversteer is to reduce the grip at one end, commonly by increasing tire pressure a little to spoil grip. "

This article pretty much sums it up. Hope this helps

[TurnpikeBoy]

As to inserts in the rear frame crossmember, well....Rick, I'm only one car ahead of yours (#9404) but there were no threaded inserts in mine, and I got the car in 2003. Then again, the car was bought without the rear swaybar, so maybe that's why. Nevertheless, it was a very, very simple matter to mark and drill two holes at each bushing location and use 3/8" self-tapping hex-head screws to mount the bushings and brackets. Yes, low-tech, but have proven more than adequate.

As to fan clearances, well...I haven't found a need yet for a puller fan - but. I did make 3/4" thick spacer blocks to lower the bigger bar at the front mounts, as the Addco bar didn't have the offset bend at the ends to provide for front framerail clearance (basically, it was bent such that it lays flat, one end to the other, on the floor - the standard-equipped 3/4" bar has a dogleg bent into the ends that props the ends of the bar up off the floor). I don't know if this would put the bar low enough to clear the fan motor, but likely would help some.

I cannot say that the larger sway bar made the ride more stiff - it most certainly has eliminated any body roll under hard cornering, made steering inputs much more immediate and precise, and has made the rear much more stable and better planted coming out of corners. As noted above, the lack of inserts is no impediment to getting the clamps into place. I suppose, if you were worried about self-tapping screws, you could use larger riv-nuts...but the setting tools for these are a pretty expensive proposition for 4 riv-nuts. The car now has about 3300 miles on the install using self-tappers and there is no problem of any kind.

Try to find a 7/8" bar and you'll find that the only outfit still making MGB bars in 7/8" is Addco. When I went looking for the bar last winter, there were a few import suppliers (Like Moss Motors) who list the bars as kits with a back bar, but no separate front bar. Addco hasn't figured out how to include end-link bushings with the bar, so likely you'll have to supply them (Addco give you two pieces of 3/8" rubber hose and tells you to use them as bushings....) and have the ends of the bar reamed for the press-fit. Or you can get some urethane bushings that might fit - there is one outfit that makes MGB end-link bushings in urethane and they look like they might work.

As to the fan - well, can't help you there. The spacer blocks might put the bar low enough to clear the fan motor, but you will have to check your car to see if that will work.


-Roger

[pgermond]

Rick,

You have one of the nicest, most sorted out, cleanest Unique cobras ever built. It is impressive how well you maintain your car and how many things you have changed. Your car should be the Unique 427 ad and poster car. They should re-do the website on the 427 car and use your car for everything!

I do think you have O.C.D. !!!

The garage looks way too clean too.

Ditto what Brent said!

[spd4me]

Rick - In the first pic it looks like the bottom bolts of the brackets are below the crossmember. Is that right and did you have to weld a tube to the bottom of crossmember.
Bob

[eliminator]

No, the bolts holding the sway bar bushings are in the rear frame crossmember, no welding required. If you click on the pictures you can enlarge them and see the detail on the mounting.

[Tony Radford]

I spoke to the folks at Gran Turismo East, a precision balancing and alignment shop here in Atlanta about doing the install and set up. Do you think it could be installed and tuned in two hours or less? Are the installatioin details documented well or at least intuitive? At least they have the tools and lift. I suppose I could do the drilling and tapping of the strap holes in the frame myself post installation to save a bit. Would it hold for the 1 hour drive back to the house without the straps?

[TurnpikeBoy]

?????

Tony, this isn't rocket science - you are assured you can do this, even on your back on the floor (what I had to do). You will find that the tube walls of the frame are really too thin to tap - you would get maybe two or three threads into it, not likely to hold for long and more likely to strip when you tighten the bolt down the first time. The install is VERY intuitive, VERY simple - no instructions needed. Simple drilled holes for 5/16" or 3/8" sheet metal screws will hold this bar....do NOT drill them too big, gives the screw more to bite into and develop strength.

You will need the bar, bushings, bushing clamps, end links (1 male / 1 female Heim joint each side with short threaded stub to connect), bolts to connect all up and whatever you choose to fasten the bushing clamps to the frame with. Alan can supply you with all you will need.

I have to believe a shop that does this for a living, with a lift, could do all within a half hour. Working on my back, on the floor, and having to crawl out 2 or 3 times for parts still took less than an hour. But you do NOT want to drive the car without the bar properly installed - make sure it's done completely before you scoot around.


-Roger

[Tony Radford]

Roger, thanks for that. I don't think a flounder could get under my car. I'll have some self tapping screws with me. If all they have to do is drill and ratchet in four screws, that shouldn't take long. Having a lift that supports the tires should make this install a breeze.

[eliminator]

The hardest part is the bolt that connects the heim joint to the lower wishbone. You will have to remove the bottom of one shock on each side to get the bolt out. I would suggest contacting Maurice to make sure you have all the spacers and hardware to connect the sway bar. Once you have everyting it could be done by a shop in under 2 hours easily.

[jmillington]

Rick,
Where can I buy the poly mounts?

Thanks!
Jim M

<snip>
Use poly mounts on both, throw the OEM rubber mounts away.
<snip>

[Slither]

Ditto what Brent and Phil said!

Wow, it is always a treat to see that frame wax!

Rick, the car looks immaculate.

[eliminator]

Thanks Paul, the sway bar bushings can be purchased from Jeg's or Summmit. I will see if I still have the part number, I think I did a thread on this too. See Sway Bar Bushing Upgrade Thread....just brought it up again.