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Does anyone know the range (degrees) of movement the Ford SuperCoupe IRS will accomodate?
I have a Cobra replica that uses a 8.8 centersection and SuperCoupe uprights. The halfshafts are shortened to accommodate the desired track. Sitting at my prefered ride height, the center shaft of the halfshaft is angled up 2-3degrees, rather than sitting horizontal.
Going down the road, everything is fine, but when I get into some aggressive cornering, I get a shudder in the backend that feels as if the halfshaft is going into a bind. Kind of feels like a tire is rubbing but I've determined that isn't the case. No signs of contact or scuffing anywhere.
I tried a bottle of friction modifier, thinking it was the TrackLoc plates but that really didn't change anything. If I raise the ride height a little higher, it does improve slightly. I haven't sat the height so high so as t have the halfshaft horizontal. Were I to do that, the car would look like it belonged with the mud-racers.
Does anyone have any ideas or similar situation on how this can be resolved
Thanks
Paul Proefrock
www.3x2CSX.com
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Hey Paul!
Welcome, being I also have a Cobra. However not familiar with your setup, HS's. I find it hard to believe your binding your HS's. How many miles are on them? How much travel do you have in your coilovers?
Tire rub? Not the same manufacture but my tires show signs of rubbing inside and outside.
Ralphy
Last edited by Ralphy (5/28/2012 5:46 pm)
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Ralphy,
My IRS was produced by Hurricane Motorsports. It is based on the Ford TurboCoupe independent rear. Uses 8.8 center w/ Ford uprights. Halfshafts are shortened Fords. The control arms are by Hurricane. All the joints on the IRS have been converted to Spherical Bearing - no rubber in the system so it will stay pointed in the direction you want. Vast improvement in handling - except for this weird vibration.
It is very similar to the one supplied by Factory Five for their cars. The shortened halfshafts are the same and from the same supplier.
I have about 5000 miles on them. Travel is approx. 4" - 2 up, 2 down. I recently install bumpstops on the frame/upper arm so their is solid contact against a bumper rather than relying on the shock. Prior to this, the shock served as the stop and was constantly destroying the bearing joints.
I initially thought my problem was tire rub - but after having been all over the car (and under) the tires aren't contacting anything. Plenty of clearance. The link you listed is the manual I got from Hurricane on it. If you are familiar with the Ford & FF5 IRS, it will look familiar.
When I go to the bump stops, I still have 1 - 11/2" clearance between body/frame to tire. If there was any contact, it would show on the glass or liner and nothing. Pretty confident it isn't the tires. Running Goodyear Eagle P295-50x15
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I found this thread. Stating good for 15 degree angle total. Thinking back the wife's Volvo acted up making noise. At first I thought she had a bad CV. Turned out to be a bearing in the hub.
I took the pdf file from your page.
Ralphy
Last edited by Ralphy (5/28/2012 6:46 pm)
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On another note we went over roll centers fairly in depth here. Lowering/changing height probably also changes your RC. Any chance you can raise the third member?
Ralphy
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Welcome aboard Paul.
It occurred to me - is there the possibility you are getting a problem with end-play? Is the geometry causing the half shaft to bind inside the Diff - push and pull?
If you don't have slip joints - that cold be a problem with some Diffs, but I'm not familiar with your set up.
It looks like time for pics! 1 more post maybe ;)
Cheers - Jim
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Paul Proe:
At the risk of repeating previous statements.
How close are you to the travel limit in plunge on your half shafts. At normal ride height if you are not centered on the plunge travel, the half shafts can bottom out your inner CV against the bottom of its bore. This can create the exact symptoms you have described. The bearing cage will break if this bottoming exists and is not delt with. If I am correct you will see witness marks on the cage and inside the inner CV when they are dismantled and inspected.
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Paul,
If the 15 degree total angle is right. Considering a 14" long HS, you would have 3.75 inches of motion in one direction. A 12" HS would have 3.22 inches. Totaling 6.44 inches ofmotion. If your static position is 2 degrees off center with a 12" HS, your starting point would be .42 inches off center, . 3.22 minus .42 = 2.80 inches of squat travel.
Maybe remove the coilover and raise your suspension so you can see just how much motion you have.
Also maybe it's not the angle but the length. Maxing out the travel of the CV joint. Maybe the half shafts were made to the wrong length? I just don't see a Cobra having enough body roll to reach the maximum motion.
Oops, brain fart! I see I am repeating TR's post.
Ralphy
Last edited by Ralphy (5/30/2012 7:06 am)
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