Bob's Track Friends Chat

[Bob Zumbrunnen]

Good point you raise about the fact that the control arms should move freely about the bushings. I haven't looked yet, but I suppose it's possible that the new control arms sandwich the bushings hard enough that the only up and down movement they'll allow is the amount of twisting the poly bushings will allow (ie. nearly none), so it still doesn't add up. When I picture the movements the rear axle goes through, I'm not coming up with any scenario where if the control arm bolts are tightened, the axle should make that its "normal" position.

http://www.globalwest.net/Mustang_rear_control_arms.htm

This was an eye-opening article. I'm not going to go as far as they suggest, but changes will be made.

I'm in posession of a new set of original rubber bushings. The axle end. Ford doesn't sell the chassis-side bushings without selling the whole control arm, which goes for something like $160 each. Today I'm going through my daughter's car since she's turning 16 soon and if I'm gonna turn her loose in a SHO, it's gonna be a tight one. Tomorrow the Mustang gets a lot of love.

Or hatred. The Ford bushings are in stout metal cups and have to be pressed in. And, of course, they're wrapped in a big identification label that's thick, goes all the way around, and is very sticky. Lots of wire brush time at the grinder.

I'm hoping I'll be able to get them in with a bolt, nut, and some really big washers. I remember how difficult it was to remove them from an axle that was out of the car. Seriously tight fit. Too tight, I think. If I can get positioned right with the rear-end in the car (taking it out is the last thing I want to do!), I'm planning to use a brake-caliper hone to clean and open up the receiver a bit.

According to the article, the setup I've got is still going to cause too much bind. The place a lot of blame on the lower control arm bushings and say that the all-poly setup I've got just worsens an already bad problem.

But we'll try it next weekend (Porsche club at MAM) with just the rubber upper rear bushings and no sway bar and see what happens. It's bound (pun intended) to be a little better.

But if it's not good enough, I just might go 3-link. I'd heard horror stories about control arms punching their way into the cabin on heavy braking when using a solid 3-link or too-stiff 4-link bushings, but in looking at the box reinforcement kit on one site, a lot of my reluctance to modify the car this way has been allayed.

In looking at the kit, my guess is that the problem hasn't been pushing the box into the car as I'd thought, but instead tearing out the sides of the box then control arm itself punches through the too-thin sheet metal of the Ford chassis. So thin that it took major reinforcing with c-channel to get the driver's seat to quit tearing away. I was reluctant to make the mod if it meant a lot of welding on the car's chassis itself. Looks like it's mostly reinforcement of the box. Not the part of the chassis where it mounts.

So, if the rubber bushings don't solve the problem to my liking, I'll go ahead and reinforce a receiver box and go 3-link and be done with it (hopefully).

Pete's experience with adjusting tire pressures matches up with my own. I've found the Mustang to be very unresponsive to small changes in pressure. I use tire pressure only as a way to preserve tires on the car; not as a way to adjust the handling. If the fronts are rolling over too far and the camber is already so extreme that it's squirrely on the straights, I add pressure to protect the Hoosiers from tearing the cap/sidewall seam. Simply put, I adjust pressure only to get the tires to roll over the amount I like. And figure I've got the pressure right if the difference between hot and cold is 4-6 PSI.

The Subaru's another story. That car stubbornly refuses to rotate and I decided to get stupid with pressure once just to see what would happen, and it turned out to work really well. 44 PSI in the front (on tires that can go up to 50) and 28 in the rear. It worked surprisingly well. The car does 4-wheel drifts through the turns, but since it's AWD, that's a good thing. The main thing is that by making the rear tires too soft (they sidewalls are so stiff you can practically run them flat anyway), the car more readily rotates and keeps rotated.

Last weekend, I'd forgotten about that and was running my Mustang setup (42 front outside, 40 front inside, 36 both rears) and it would either not rotate at all, or could be gotten to rotate if handled abusively but wouldn't stay rotated. Letting a bunch of air out of the rears cured that and it was a blast going through turns the way it likes to go through turns.

I've seriously considered running stickies on the front and good street tires on the back. The push is that severe.

Since I was unfamiliar with the 911C4S I was instructing in, we asked around about trail-braking. I didn't drive the car hard enough to scare the student, but could feel that weird combination of a car that felt like it really wanted some trail-braking but had to be handled carefully because of the huge ballast behind the wheels. I came to actually like that ballast because it felt like oversteer could be induced more easily (as is too much oversteer, I'm sure) and once the attitude through the turn was what you wanted, you could apply power and it'd go through as if on rails. VERY different from anything else I'd driven.

I didn't want to trust my own instincts that the car wanted trail-braking, though, since it's such a spinnable car. But when we asked around, it was unanimously confirmed that the car really does like it. My student was a first-timer, so I didn't want to mess with that yet, but I did explain the mechanics of it to him and suggested he try it in parking lots then later on the street, then we could use it on the racetrack.

Well, daughter's up, so time to go put her car on the lift and really go through it with the fine-toothed comb. So nice to have a parts car for it sitting right in the same building.

Oh, and she's gonna do a lot of the work herself, with me just showing her how to do it. Rotating the tires, changing the oil, taking the front speakers out of my (never driven anymore) 89 and putting them in hers, fixing the driver's door lock mechanism (parts car might prove handy there) and I'm sure a million other things we'll find wrong with it.

I'll let you know how the rubber bushings do in the Mustang next weekend.