Norm Peterson

My hat's off to you for those . . . both are outside my comfort zone and probably have been for decades.


The tire absolutely will deflect at the top, though it won't be by nearly as much as at the pavement. It won't be this bad ↓↓↓ , but the deflected shape will be at least generally similar.



Reasonable, and I think that's a better gauge than trying to use the sheetmetal (which would introduce perspective changes due to roll).

If you do try to take a video, it might be a good idea to include a separate tether to the camera mounting arrangement.

The S197 is probably a much better handling platform (at least potentially) than previous Mustang generations led people to expect. Seems when most people hear the name 'Mustang' the initial thoughts involve "loud", "drag racing", "racing on the street", and more recently "running out of control when leaving car shows". It didn't take too many years in SCCA's Solo for the S197 to utterly own F-Stock (now F-Street), which they did until the 1LE Camaros started getting dialed in and certain BMWs were allowed in that class.


Norm

Tw557

I have gone to a few track days recently to watch at the Poconos and Summit point which were my Roadrace tracks. A friend bought a used Porsche and is having fun with that since his roadbike racing days have passed also. I have seen a few s197's doing quite good. A couple boss 302 were doing very well even on the smaller autocross which I did with my ecoboost. So I then got he idea to buy an 06 salvage title that was mostly cosmetic and fix up and maybe hit the track. Well then my wife and daughter got in on the game. They don't have the vision of a fixer upper and found this one close buy that they loved AND its an automatic. So between the car being in great shape and being an automatic i'm not sure its going to see the track other then an autocross.

I think if time permitting this weekend I'm going to try the camera (tethered)with the 275's on the rear and then switch the 255's to the rear and see if a difference. I did look up your control arms and I'm not sure they are in the budget right now but I am looking into a few option that will hopefully not bind up on the street cornering bumps.

ohskigod, Which model of BMR arms did you purchase. The cheaper double bushing ones really concern me of binding up over un even bumps.

Tw557

I'm thinking about trying out a prothane bushing kit on the rear LCA's It could firm things up but by using the stock stamped arms I'm thinking the weaker center area could allow enough flex to not bind up. Doesn't sound like its a bunch of fun to get the rubber bushing out but should have enough tools to get it done.

Norm Peterson

You'd have to do a brief structural analysis to find out what the torsional stiffness/flexibility of the metal part of an LCA might be. From that you might be able to estimate what it would compare to in terms of a virtual rear sta-bar with bushings either completely rigid or of some finite stiffness as springs in series.

But it's probably easier to DIY a voided bushing approach and not worry about the metal needing much compliance, where you go about making the poly somewhat more compliant in a couple of directions by removing bits of it here and there. This will at least theoretically reduce the service life of the poly, but poly bushings should really be considered "wear parts" or - in extremely severe use - "consumables" anyway. I actually drew up a sketch of what I'd done with the rear LCAs for a RWD Chevy Malibu (triangulated 4-link quite similar to the Fox/SN95 Mustangs), but I guess that was too many computers ago because I can't find it right away. Years ago, a Maximum Motorsport employee ran a series of "roll bind" measurements as part of their development of "3-piece poly bushings", and the aim was the same - remove the worst of the stiffness in the "bad" directions. There's a chance I posted a copy of his testing on this site, maybe 8 or 10 years ago, and I can at least find my own copy of that one.

I've done the rubber to poly bushing swap a few times, and the quick DIY approach with the least likelihood of deforming the metal involves heating/burning the rubber out and sanding or wire-brushing out the debris that remains. This is a messy, smelly job, and the rubber usually snaps and spatters and drops little ***** of molten rubber (read: do this outdoors, wearing the oldest work clothes you own).


Norm

Tw557

I am notorious for plaguing myself to save a couple dollars over the years. I only have a propane torch and I'm not sure that will give enough heat to replace the bushings easily. Plus the BMR has grease fittings. So for a little more I'm going to try a box beam BMR arm set I think. I then plan to mill (3) 1/8 holes about a 1/3 of the way deep on both sides top and bottom of the center steel bushing. That will mimic the rotation that a spherical and do or more so like the stock bushing but still be full strength front and back. I was wondering if this was the DIY you mentioned earlier.

My nightly craigslist search scored a set of Koni Yellows on craigslist last night for $125. They are new but open box. Don't look to have ever been mounted and had a very solid feel to the stroke. I still plan to do the go pro under the car this weekend. Hoping to find a good solid spot that points in the right direction.

Norm Peterson

You're going in the right direction for a poly/poly configuration. I found that 1/8" holes were still too small (too much roll stiffness remained), though the S197's rear geometry might be OK with smaller holes than what I ended up with on the triangulated 4-link (over half the radial thickness of the poly). You might want to pin bushings so modified to keep them from rotating inside their outer sleeves.

I also sanded the flat faces of the poly into very flat cones so that the poly could not develop any moment resistance directly from the brackets. I suppose you could leave a tiny width of poly at the same length as the inner sleeves as a hedge against water intrusion, though that never ended up being a problem.

Your test for added roll stiffness (and the effectiveness of your efforts at reducing that) is to drive at an angle over a drainage gutter - or any other smooth contour that can be taken as one-wheel bumps) while paying attention to the amounts of lateral head-toss the car throws at you. At 1/3 depth for the holes plus the other things, 80% reduction from what the poly/poly adds should be within reach.


Norm

Tw557

Sounds good with your advice. I was waiting to see the mass of the bushing to determine if I was going to go with a 3/16 hole possibly. I didn't think of the sides of the poly bushings but that could be a factor. I'll pop them in my lathe and cone them out a little. I wanted to see if the bushings had any keying feature to hold them in position of if the grease fitting would help. But easy enough to drill and tap a 10-32 from the outside in about 1/2" to hold it pretty good. I work a few minutes from CJ Pony so I plan to stop in over lunch today to check out the arms.

I'll try some hand flexing (twisting) in the vise then and see how it feel up to about 10 degrees rotation in the bushing. And of course plan to see how the stock ones feel. I of course hope they feel terrible and fall apart in my hands. LOL

Tw557

Well I have to say I am very pleasantly surprised at how much difference the new BMR control arms did for the handling of this car. I did drill in about 5 3/16 holes on the top and bottom of each side of the bushings. This took the torque needed to twist the arm about 5 degrees from a bit over 100f/lbs to about 35 f/lbs. Install was quick and easy. I then took the test ride and about 70% of my rear sway feeling is gone and I am very happy with much better compliance over the bumpy back roads. I assume the last amount of sway is probably the All Season tires but I didn't put the poly bushings in the panhard yet though. Honestly, the Rousch shocks don't seem too bad now. Maybe just a little soft allowing the car to g out a little more then I want a few spots. At this point I am not planning on doing the upper control arm yet. Plus looks like it can be a bit of a pain. I just really didn't give the control arms enough credit.

Once I had the stock arms off I could then tell how incredibly soft the bushings were. But I did check the actual stamped arm for twist stiffness and the arm itself was only about 15 f/lbs of torque for 5 or so degrees. The metal is very flexible. So maybe the ideal setup in poly bushings installed into the stock arms. But I have no issue at all at least for now with the modified BMR.

I also checked my in and out play on the rear wheels. I have about 0 on left and about 1 mm on the right. I assume that is fine. Now I'll try the Koni yellows next weekend if time permits. Doubtful with plans to hit the American Muscle show on Sat.