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95_5speed
01-16-2003, 09:01 AM
Hey in the last post I think it was Mannysc said he made poly bushings for his sub frame and eliminated it. I was wondering if anyone had the demensions for the bushings and maybe a pic or two.

Thanks

Mike8675309
01-16-2003, 11:59 AM
Mannysc said he made them from a block of poly on a neighbor's lathe. He hasn't come up with dimensions yet but is working on sourcing the pieces and maybe selling completed units.

The dimensions would be simply the same size as the existing rubber isolators that are used in the subframe. These rubber isolators allow too much movement in the rear subframe in the horizontal plane causing the wheels to load and unload, thus hopping.

DrFishbone
01-16-2003, 01:19 PM
okay, i'm not clear on exactly what bushings are the ones that let this problem happen....is it the two lil rubber ones that separate the rear end bracket and the actual rear end?? i was looking at those.....they seem kinda squishy :) two little circlular bushing....about 1/4-1/2 inch thick....maybe around a 1/2 inch in diameter.....least that's what my memory is telling me :) are those the little farts?

dRfisH

Randy N Connie
01-16-2003, 06:05 PM
I THINK HE IS TALKING ABOUT THE FRAME THAT THE TOTAL REAREND BOLTS TO.
AND THIS FRAME BOLTS TO THE CAR.BETWEEN THIS FRAME AND CAR YOU WILL FINDED
4 RUBBER DISC.1 BOLT GOES THROUGH EACH OF THE 4 ARMS,TO BOLT THE
FRAME TO THE CAR.I WAS THINKING ABOUT REPLACING THE RUBBER WITH ALUMINUM
DISC WITH BOLT HOLE IN CENTER. I HAVENT CHECKED IT OUT YET TO SEE THE DIA THE
DISC NEED TO BE,OR THICKNESS,THAT I NEED TO MACHINE THE DISC .THE RUBBER FLEXs
AND THE REAR END GOES TO THE FRONT OF THE SC AND THEN FLEXs BACK TOWARD THE
REAR OF THE SC.THIS I TURN CONTRIBUTES TO THE WHEELS JUMPING UP & DOWN.

mannysc
01-16-2003, 09:16 PM
finaly someone understands the woords that ah commin out my mouuthh,those are the culprits, the four big squishy sloppy bushings type thingys.

SweetSc
01-16-2003, 10:33 PM
But I dont believe its a problem with the wheels bouncing up and down. They are actually moving from front to back. Is that what you ment to say? If not, I dont believe thats the source of the problem.


Chris

Mike8675309
01-17-2003, 12:27 AM
It's physics.

Yes, the wheels hop up and down. But they don't go straight up and down. Instead they are going in a elipse.

#1 - All the bushings play a role in the issues with wheel hop on the car. But people that have replaced all the bushings still have the problem. That's because of a design flaw that even new bushings won't fix in the attachment of the subframe to the unibody.

Our cars are Unibody construction. No frame rails. The body of the car makes up the frame. To simplify construction, our cars use SUB FRAMES to mount and attach the suspension and engine to the body of the car. These subframes are rubber isolated to the body of the car to prevent road vibrations from being transmitted into the car cabin.

And here is the problem:

Automatic cars have built in slop in the form of the Torque converter. 5 Speed cars just have a clutch. Thus when you are trying to smoke the tires and dump the clutch, all the torque from the engine is immediately transfered to the tires. But because the tires are on the ground, they don't immediately move. They first must overcome the weight of the vehicle to drive it forward.

So imagine the wheel trying to roll forward because the drive axle is trying to turn because you just released the clutch. So since our car is heavy, the rubber bushings in the A-Arms that locate the rear wheel knuckle first compress. Then the bushings that locate the A-arms onto the sub-frame compress as the wheel continues to move forward. And then the subframe actually starts to shift forward as it's rubber bushings start to compress . Now, if you are really into it the tires loose traction. And then the problem happens. Grip is lost, forward momentum is broken, and the tire slides. But all this compressed rubber bushings now spring back, throwing the wheel back, but as it slows down it grips again, and drives everything forward, recompressing all the rubber, and the pattern continues.

The wheel hops up and down a bit because the bounce factor in the rubber of the tires. The wheel is thrown back and when it hooks up again it tends to leap forward, causing the bounce. But the primary movement is forward and back.

People have put air bags in the springs to stabilize the suspension. But that just clears up the minimal up and down bouncing. The forward and back bouncing can be improved by bigger anti-roll bars (as they then tighten up the whole subframe). And poly bushings in the A-arms certainly helps. But those big sloppy rubber subframe bushings need to be improved to fully remove it.

This doesn't happen any where near as much in a auto tranny car because the torque converter ends up dampening the shock like reaction of the driveline to the applied torque.

That's my theory and i'm sticking to it.

mannysc
01-17-2003, 01:02 AM
the subframe isolater mounts need to be replaced, with a solid semi sold mount or isolater, mine are poly, but aluminum or other substance can also be used, depends on the use of car for strip car solid aluminum or other solid mounts can be used for street strip a poly or semi solid material is in order.

JAFO
01-17-2003, 01:25 AM
Great information, I'm saving this thread to my personal FAQ folder. Manny, do you have pictures of the new vs. old mounts? That would be great if you or someone had the resources to make/market these things.

Randy N Connie
01-17-2003, 10:38 AM
KENNY BROWN MAKES A TUBE SUB-FRAME,THAT REPLACES THE FACTORY SUB-FRAME
FOR STANGS WITH IRS REAR ENDS.DONT NO, BUT HE MAY BE A SORCE FOR DISC REPLACEMENT

DrFishbone
01-17-2003, 02:43 PM
pictures yes.....that'd keep me from getting dirty on a cold december afternoon!!! :D okie...i understand why they "hop"....but like you were saying....it's actually more of a forward-back motion, since the major axis of the elipse is horizontal. hehe...anyways, pictures would be great! i'll get under the car and look at what i'll need to do if i want to fix this problem. hmmm....actually all these rubber baloney bushing may be why my car feels like i gets streched whenever i go over a sharp bump at cruising speeds! nothing serious, just annoys me (the stiffer shocks are to blame i sure) but hopefully i can rid my car of the rubber junky thingys ;) thanks!

drFIsh

mannysc
01-17-2003, 07:06 PM
heres a picture of the bad boys doing the crime.

Mike8675309
01-18-2003, 08:18 PM
www.mn12performance has an EXCELLENT write up on beefing up your IRS suspension subsystem.

Below is a picture where you can see the 4 main subframe bushings at the 4 corners.

These are the only four points where the entire rear subframe attaches to the body of the car. Thus with 300+ ft/lbs of torque hitting the road pushing against 2 tons of car, you get some deflection of the rubber.

Click the picture to jump to the Article and more pictures from MN12performance.

http://www.mn12performance.com/mn12how-to/irs/irs.jpg (http://www.mn12performance.com/mn12how-to/irs/irs.html)

darkstar_one
12-25-2005, 02:01 AM
hey any more info on the FRAME BUSHINGS? thanks.

yes i know how old this thread is.

68COUGAR
12-25-2005, 02:33 AM
People have put air bags in the springs to stabilize the suspension. But that just clears up the minimal up and down bouncing. The forward and back bouncing can be improved by bigger anti-roll bars (as they then tighten up the whole subframe). And poly bushings in the A-arms certainly helps. But those big sloppy rubber subframe bushings need to be improved to fully remove it.
The whole air bag argument comes directly from solid axle / coil spring cars, like the Mustang. On those cars, the wheel hop IS vertical. Since our IRS wheel hop is not all vertical, air bags don't cure it.

Bigger sway bars only help when the vertical component of the hopping is out of sync on each side of the car. If the vertical component of the hopping is IN SYNC, the sway bars will have no effect on it at all. I have the 1 3/8" Competition bars on my car car. They are GREAT for handling, but did Nothing for wheel hop.

I bought, but have not yet installed the poly knuckle kit from:

http://www.vintageperformancemotorcars.com/

68COUGAR

68COUGAR

AsScLoWn
12-25-2005, 02:17 PM
anyways, I added quad shocks like mustangs have and the hop went away.
If you actually believe you have no hop, expecially in a 5-speed, dump the clutch a bit when starting off in the rain and give it some gas, if it bounces you still have wheel hop :rolleyes: