Lateral-g Forums - Ron Sutton Offset 3-Link install

Answers to FAQ

1. The square tubing struts are simply for mock up purposes to simulate where the shock goes & hold the rear end at height.

2. The sub frame rails Ron Myers found from a company that makes a lot of frames rails … didn’t fit perfectly. With the front of rails against the floor & the back of the rails against the floor … there was a ¾” gap between the frame rails & the floor in the middle. Of the various installation options, the lowest priority was the middle. So there is a gap there.

3. The Watt’s Link bellcrank & links are just mock up pieces. The final bellcrank will look similar but be longer & use ½” bolts on the outer two rod ends & will be either the shiny aluminum you see of anodized bright black … Ron Myer’s choice.

4. The links will be powder coated black, but with one will have curves, not straight like the mock ups. The lower right link actually curves to form a slight S stepping forward … so there will be only a small ¼” spacer between the rod end & shock. Not the 3 big spacers shown in mock up.

5. The rod ends are heat treated chromoly wide body design. The ball rides on an injection molded nylafiber liner that is self lubricating & keeps the dust out. These are the best low maintenance rod ends & they do have about a pound of stiction. For pro race teams that clean & lube the rod ends after each event, we run a similar rod end without the nylafiber liner for zero stiction, but more maintenance.

6. I see a lot of Watt’s links where the bellcrank bolt attaches to a plate with holes. There are two major negatives to that strategy. One … if you have to jack the car up … unbolt the bellcrank … move it to a different hole … and rebolt it in … that takes time & work … and you are less likely to do that at the track as a common tuning tool. Second … by the nature of holes in a plate … the adjustments are somewhat coarse. Typically the holes are 3/4” to 1-1/2” apart. That is a big change. That would be ok if the car was out to lunch. But if the car is pretty good handling & we’re tuning for track changes … most times we need anywhere from a 1/8” change to 3/8”. Raising or lowering the roll center ½” is a bigger change than many guys might think.

7. Adjusting the rear roll center is … one of the best tools to balance the handling of a car for changing track conditions. It is … or at least should be … one the easiest tuning changes to make too. But only if the adjusters have been well thought out.

8. The adjuster for the bellcrank in my Track-Star Watt’s Links like Ron Myer’s here … provide a full 6” of quick & easy adjustment. The second photo from the top shows a bottom view shot … where you can see a hole in the billet steel framework & a threaded hole in the bellcrank center bolt. That allows us to utilize a non-loaded threaded rod in the assembly … with an aluminum cone on top or bottom for easy adjustment.

7. When we mount the adjuster cone on the bottom … the Tuner slides in under the car with a ½” ratchet (no socket) and adjusts the rear roll center in any amount desired just by turning the cone with the ratchet. The threaded rod is 14 threads per inch … so each full turn is a smidge over 1/8” of an inch. You can see it allows pretty fine adjustments if desired.

8. When we mount the adjuster cone on the top … an aluminum rod attaches to that cone … goes up thru the tube in the crossmember … and protrudes a few inches up into the trunk area in front of the fuel cell … with an adjuster cone on it. This way the Tuner simply opens the trunk … reaches in & turns the adjuster cone with a ½” ratchet … without crawling under the car.

9. I typically plan the rear roll center adjustment range from 6” above ground to 12” above ground. This way you can optimize the rear roll center for whatever suspension strategy you choose & any type of track.

10. Frame mounted bellcrank versus housing mounted bellcranks? Housing mounted bellcranks keep the roll center basically the same at all times because the center of the housing only lifts or squats a minimal amount as the tires compress or stretch. The lay person may think that’s desirable but it’s not. Frame mounted bellcranks move the roll center with the chassis. So if you have chassis lift in the rear on corner entry the roll center goes up with it … minimizing the roll angle. On corner exit, as the driver lays power on the car squats in the rear to some degree … the roll center lowers with the chassis, providing more rear grip & forward bite for optimum corner exit acceleration.

11. Weight is our enemy, so I design all of my stuff to be as light as it can be & still as strong as it needs to be. Plus I work to multi-purpose things as much as possible … to reduce duplication of items & unnecessary weight.

12. For example the upper Watt’s link crossmember serves as the shock crossmember also. Why run two crossmembers only a few inches apart? That is unnecessary weight. Of course it took me some work to make the packaging all fit well. But there are no wasted tubes, no duplication of mounts or crossmembers & no unnecessary weight.

13. Another example is the Watt’s link housing mounts. I see a lot of heavy, bulky mounts that clamp on. Just adding weight to the rear end. Most have to add two mounts to the housing. My design here dual purposes the right rear shock mount. This not only saves the weight of the bracket & bracing, but bolt hardware too. All of this weight is “unsprung weight”. The lighter we can make the rear end housing … especially out at the ends … the quicker the suspension can respond to irregularities on the track. Lighter unsprung weight in the suspension = more grip.

14. A common question is about the additional load that shock bolt sees with the lower right Watt’s link attached to it. Anyone that knows me very well, knows how safety conscious I am, so you know I did the math. I have a bolt load stress calculation spread sheet I use.

For those that care … calc’s ran as:
* 4000 # Car
* 50% rear weight (2000#)
* 1.5 G load
* 3000# force

No, Ron’s car won’t be that heavy … LOL. I like to do my calcs with more load on stuff than it will actually see. Like a safety factor inside the safety factor.

The bellcrank bolt sees half of the total force going through the Watt’s link.
* 1500# force on ¾” Grade 8 bellcrank bolt @ 1.156” = .0017” deflection (17/10,000)

The four bolts & rod ends each all split the other half of the load four ways, for 375# of force.
For weight savings, I utilize lightweight, tubular chromoly bolts on most mounts that are in double shear. For single shear suspension items, I use special 170,000 PSI 12-point bolts.

The combo shock & Watt’s link bolt sees loads from both the coil over shock & the Watt’s link.
* 1600# force on ½” 160k PSI link bolt @ 0.3125” = .0002” deflection (2/10,000)
* 375# force on ½” 160k PSI link bolt @ 1.1875” = .0022” deflection (22/10,000)
* The forces are from different vectors so the deflection doesn’t really total .0024” … but it doesn’t matter anyway, as anything this small is negligible.

P.S. Shear strength ratings of the hardware is:
* ¾” Grade 8 bellcrank bolt = 39,762#
* ½” 170,000 PSI 12-point bolts = 20,023#
* Chromoly Rod Ends 5/8” shank & ½” hole = 31,390#

15. One advantage a panhard bar has, is it allows us to get the fuel tank closer to the rear end. But I work to get all I can, so this Watt’s link design is pretty compact, allowing us to place the fuel cell only 9.5” from the rear axle CL.

16. As mentioned earlier … by placing the frame rails narrower … we’re able to get the 3-Link trailing arms out wider … get the shock mounts out wider … and get the Watt’s link mounts out wider. All of this reduces the angle changes & geometry changes during suspension movement.

17. Getting the shocks out wider is a bigger deal than most people know about. The motion ratio affects the springs … but it’s no big deal to run softer springs for wider placed shocks & stiffer springs for narrower placed shocks. But the shock is more responsive … and has better control … the wider we place them.

18. In other words, we can partially make up for lower motion ratios of narrow spring mounting by simply increasing the spring rate. There are side effects though. The side view motion ratio doesn’t change … so a stiffer spring is truly stiffer as far as the side view motion ratio is concerned … and this affects the basic up & down motion for bumps, as well as affecting grip under acceleration. So we always want the springs out as far as we can get them to help with grip.

19. All shocks have delay in them. Gas monotube shocks have less delay than twin tube shocks, but again … all shocks have delay in them. The closer you mount the rear shocks to the chassis centerline … away from the rear tires … the greater the delay. Meaning … the longer time it takes for the shock to respond … which equals less control. The farther out we place the shocks from the chassis centerline … closer to the rear tires … the smaller the delay. Meaning … the shorter time it takes for the shock to respond … which equals more control. Control is grip.

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20. In future photos you’ll see:
* Curved Watt’s Links
* Smaller Rod Ends & Bolts
* Watt’s Adjuster Rod & Cone in place
* Rear 3-piece Sway Bar installation

:cheers: