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10/27/2011 7:25 pm  #1

mocked it up in the car yesterday... the good the bad and the ugly

on August 31, 2010, 9:22 am, Daze wrote:

I absolutely love the clean look and easy install of my bolt in sub frame. I know it has clearance issues and I may still have to ditch it, but at this point I will keep it if I can because of how well the mock up went.

Second thing I was very happy with was ride height when the wishbones were level. I used some steal tubing in place of the shocks and dialed in the suspension (upper shock mount in stock location relative to the amount the system was narrowed)

All the calculation I had made based on the original live axles location served me well and I was able to get a rear tire ride height just a bit taller than stock. I realize the system need to come forward about 1/2" to center the tires in the wheel well, but that will not be hard to do.

I also got an even better under standing of the systems camber curve and with the LCAs tilted down camber becomes positive so there is a big reason to correctly set the LCA parallel to the ground like Jaguar intended.

Now to the bad.
I still have the clearance issues with my side frames. Looks like there is room for me to modify them to clear the hub if I choose to do that, but it is going to take some more thought and prep before I decide exactly what to do.

The adjustable upper shock mount is a bigger pain in the but than what it is worth. This is due to a couple of things. First with it all put together there is not a lot of room to be moving the upper mount. when I drilled out the adjuster holes I drilled 9 of them but due to clearance issues at the bottom of the car and clearance issues to the half shafts only about 5 of those holes will be usable. I also didn't realize how drastic the camber change was when the LCAs are angling down, at one point I had 3º of positive caster. with this in mind it makes far more sense to adjust the shock mount location to set the proper ride heigt/suspension location from the beginning other wise there will be alignment issues.

The ugly

When I set the system up with the coil over on the car, put the tires on the hubs and then put the weight of the car on the suspension, almost nothing happened. The suspension was very stiff, not to stiff, but stiff enough that I would not want heavier springs, especially with my KYB gas adjusts, which haven't even been installed yet. With the coil overs I had 6" from the top of my tire to the bottom of the fender lip... UGLY and there was so much angle on the wishbones that there was as I said before 3º positive caster on the tires, without any shims between the diff and the half shafts. I even tried it with just one coil over per side to see if that made much of a difference, but it only lowered the gaping opening between my tires and my fender by another inch.

This means in order to have the set up I want with, two shock per side, the correct wishbone orientation and proper ride height I must either find shorter coil overs or move the upper mount. The steel pieces that give me the ideal ride height are 10" center to center on the mounting holes with the current upper mount location. A Jaguar shock s 13.5" center to center when uncompressed, and it looked like my suspension only compressed about 1/2" to 3/4" when I put the weight of the car on the suspension. I need to take the exact measurements of the amount of suspension compression so that I can modify the cross bars and raise the mount. this should get me dialed in for both ride height and a parallel wishbone.

All in all yesterday was a VERY productive "Day" and I am more excited about this install than I was before. I should be able to easily work around the few small issues I have and get things set up just the way I want them.

If it isn't broken..... modify it anyway!!!!

10/27/2011 7:26 pm  #2

Re: mocked it up in the car yesterday... the good the bad and the ugly

  on September 2, 2010, 10:44 pm, tyrellracing wrote:

Clearly shortening the LCA's must have improved the leverage the coil overs had over the load. Was the fuel tank half full? That is recommended when setting ride height or a weight that approximates the fuel load. Your shocks look like they are at similar angles to mine but further inboard. When I mocked up mine, I could bounce my car by hand hard enough to bottom it out. Fast backs are heavier in the rear than coups and I set my engine back 4 inches so that must have played a role in the mushy feel of my jag springs.

If it isn't broken..... modify it anyway!!!!
     Thread Starter

10/27/2011 7:27 pm  #3

Re: mocked it up in the car yesterday... the good the bad and the ugly

on September 7, 2010, 3:19 pm, Daze wrote:

huge catch!!! thank you!!!!!! I didn't even think about the weight in the fuel tank, its empty right now. My brother is lending me 4, 25# weights so that I can set it up and see what it does with a 50# load and a 100# load. Thanks again!!!

If it isn't broken..... modify it anyway!!!!
     Thread Starter

10/27/2011 7:28 pm  #4

Re: mocked it up in the car yesterday... the good the bad and the ugly

  on September 9, 2010, 10:23 pm, irstang wrote:

Mock ups can gain you a lot of information and allow you to make design changes. Nothing but good will come from breadboarding your mechanical system like you are doing.

I have some concerns with your mock up numbers, however. I believe you are using stock X-type coilovers, same as me. According to the data I have the springs go solid at about 9.7 inches. This is a difficult number to check since this equates to maximum suspension travel and you are going to have to pile a lot of weight in the trunk to get there. My Boge shocks by themselves max compress at 9 inches, so the 9.7 number seems reasonable. They extend to a maximum 0f 13.4 inches. Total travel is therefore 3.7 inches. Aldan Eagle recommends we should set up a ride height at about 2/3 of travel. This equates to about 1.25 to 1.5 inches of compression at ride height. I am striving for a compressed length at ride height of 12 inches. This gives a bit more than two inches of compression and 1.5 inches of rebound.

Coilovers should be at about a 30 degree angle off vertical at ride height. The angle you have set looks pretty close to optimum. If you increase the angle much more the car will ride softer, especially while cornering.

From looking at the pictures of your mock up it looks like a compressed length of 12 inches would make your car sit very high in the rear. The 10 inch strap which I believe simulates max compression leaves the the tire completely showing in the rear well picture.

What can you do with your design to move the upper attachments for the shocks upwards in relation to the differential? This is the adjustment you need most of all. Also, can you position the differential any higher? Can you eliminate the sub-frame sides and weld the center differential mounting tubes directly to the Mustang frame rails?

If it isn't broken..... modify it anyway!!!!
     Thread Starter

10/27/2011 7:29 pm  #5

Re: mocked it up in the car yesterday... the good the bad and the ugly

on September 10, 2010, 8:40 am, Daze wrote:

Until you mentioned it I have not heard about 2/3 compression at ride height. I have heard that Jag set it up with a 40 60 ratio with the shock 40% compressed at normal ride height. When I set mine up I was not and am still not worried about that ratio. The Jaguar is so much heavier that I fear the coil overs would have to be mounted much further inboard to achieve that 40 60 balance which in turn as you know will make for a softer ride.

I based all my calculations on my desired ride height and the desire to have the wishbone parallel to the ground at normal ride height. Due to the camber curve it is important to have it set up this way for optimum camber during suspension travel. With those two criteria in mind I have the differential located exactly where I want it. I like a little rake on my car and with the weight of the car on the suspension the lower lip of the fender is about 3/4" above the top of the tire, and my wishbones are ever so slightly off of level

You are correct that in my pictures my upper shock location was totally incorrect!!  when I had it mocked up it was so bad that the top of the fender was 6" above the top of my tire. The biggest issue was my adjustable mount and how far down it hung, now that I have eliminated that and made the upper mounts a direct attachment to the cross bars I have the car sitting exactly where I want it with just a slight rake. Good news is I will be able to maintain mild adjustability with two or three options as an upper mount in case I want to move it up or down a little bit. The wishbones being slightly off of level only mildly effects the camber curve

If it isn't broken..... modify it anyway!!!!
     Thread Starter

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