That 66 3/4 is assuming my toe-in is set to 0.

Just rechecked and I am toed-out by 3/8 inch.

So, I think the actual figure is closer to 66 1/2 -give or take a 1/6 of an inch.

 

[QUOTE=49willard;15231154]Assuming that wms is "wheel mount surface" I just happened to measure mine with the truck on my lift and wheels off (suspension on stops) and I got 59 1/2 ". It will be a bit more with the lower control arms level-weight on the suspension. That agrees reasonably well with the Jag track width of 58.3 since as I stated above, Jags had 1" offset rims such that you subtract 2" from my wms to wms measurement getting 57 1/2. My measurement should increase by of the order of 3/4" with the weight on the suspension. Using Jags #'s the wms to wms should be 60.3".




I knew that there would be a significant difference (increase) for wms to wms with the suspension fully loaded. I just measured it in the fully loaded case. The distance increased by almost 2 inches. As noted earlier I indicated that my springs are original and my lower control arm is almost level when fully loaded (fully assembled truck with sbc and 700r4)

 

[QUOTE=49willard;15232983]So it was 61 1/2 with the suspension at ride height? I'm just trying to see how close it is to the Lexus IFS i have. I did a quick measurement with the a-arms parallel to the ground and got over 61 but don't remember it exactly

 

[QUOTE=c91x;15233186]

The 61 1/2 measurement is with my weak" original springs such that the lower control arm is level. I do not think that the measurement would be that high for a typical Jag since the lower control arms normally point down a bit toward the wheel. Probably a little closer to 60 1/2".

 

Bill and I have been talking on the phone over the last few days about old cars in general, and F1's with jag ifs in particular. He asked me to add my findings to this thread. I'll start with the finish. My F1 has 10,000 miles on it, and I'm using P215/60R16 on the front, and P235/65R16 on the rear on 16x7 wheels with 3 3/4" backspace. It looks great, and doesn't rub. Now the story.
My jag is soft mounted with stock jag rubber mounts. Mine is similar to most of the other soft mounts, pics are in my gallery. To lower the front 4" to match the rear, I first removed all four of the plastic shims, and added some washers between the lower spring plate and the lower control arm. At that time I was using 235/60R16 on the front without the fenders mounted yet. With the fenders mounted and a passenger, the front tires rubbed entering drive ways. I had the first show in a few days, the debutante ball for the truck, and I didn't have time to experiment alot. My spare is a 215/70R16 (skinny version of the rear tire) and the narrower tire worked, but it rubbed once or twice while turning during a bump. My next try would have been 225/60R16, but I was out of time and needed a sure thing. I knew 215/60R16's would work, so that's what I went with. All was good for 5000 miles or so when I started getting a bit of rubbing in heavy bumps. I noticed the front end was very low, about 8" at the bottom of the frame (10 1/4" is normal). The springs, original, were sacked.
I ordered new springs online. There was only one part number that covered both the six and twelve cylinder models so I wondered if the spring rate would be correct. I installed the new springs with the four spacers and the spring plate in the stock position. The front stuck way up in the air. It looked like a gasser truck. It was several inches high. I removed the four spacers and tried again. It was still too high. After several tries, I found that four regular washers between the spring plate and control arm, along with no spacers gave me my correct ride height. After 5000 miles on the new springs the ride height hasn't changed. I haven't rubbed since the new springs were installed. The ride and handling are fine and the stance is great.
Rusty

 

Bill, we were talking about your desire to tow with willard, and adequate tire load rating. For everyone else's benefit, I'll explain what we talked about. After the tire size you'll find the load index and speed rating. For example, P235/65R16 103S. The 103 load index, from a load index chart tells you how much weight the tire can carry. Half ton F150's, when they still had 15" wheels, typically had a load index of 105, in the stock P235/75R15. As long as the tire you choose has a 105 or higher load index, you'll have load capacity equal to what F150's had until the mid 90's.

 

Thanks rhopper that was real informative will run the same as have been wondering which way to go

 

Rusty. Thank you for your most excellent post and taking the time to discuss same with me. That is exactly the type of information that benefits those coming along on their F1/Jag Ifs combination and the reason that I started this thread. There is no substitute for hard data!
I am in the process of going toward your formula. I have not ordered new springs-yet, however, that may just be my next move. I have ordered new rims to get into 16's rather than 15's based on declining access to 15's. I had to buy and paint 2 new rims for backspace reasons for the front in any case and decided that since I would already be painting 2, I would do 4 and go to the 16's. I am not sure that I can get wheels to fit and get to the 105 rating like the older F150's. I hate to scrub my thoughts of towing my trailer since I went thru a lot to set it up to tow. I currently tow with my 2003 Ranger and tow 4000-5000#. I need to do more research on tires. At first blush it looks like the ratings are mainly a function of tire size.

 

Bill, tire size has a lot to do with load rating. The air carries the weight. The more air inside the tire, the more load it can carry. A bigger tire contains more air, so it carries more weight. Increasing the ply rating allows higher pressures which just means more air in the same size tire. This is where we go from a P metric tire to a LT tire. P metrics usually have a max pressure of 35-41 pounds. Lt tires ( c d or e rated, the old 6, 8, or 10 ply) usually have a max of pressure of 50, 65 or 80psi. The higher pressure allows for more air to be packed inside so it carries more weight. Don't stress if you don't get a tire that has a 105 load index. The Rangers of that era typically had a 235/70R16 tire which has a 104. That's only a difference of 42 lbs per tire.

 

Rusty,
Thanks for the additional info/tutorial on tire rating. It looks like I can get close to the 105 rating on the rear which is where the additional hitch weight for towing will be. I r and r'd the springs yesterday installing additional shims. It is up high enough to at least move it around. I have 4 new 16" wheels coming from Summitt Racing which should be here on Tuesday. I will shoot some color on them next week.

 

I made a tool to remove and replace the Jag front spring using the threaded rods as Dave used and after hand wrenching once to add shims under the springs decided to improve on the time and effort. I sliced a 9/16 socket in half which fit well in a standard pipe and then welded the 2 halves of the sockets in each end to the 10" long pipe creating a 10" deep, deep well socket. This allowed me to use a 3/8 air gun working my way maybe 1/2" to 1" at a time, big difference in the job!

 

Bill, that's brilliant! Rest assured that fifty years from now that tool will be shown around to others asking, "what was this tool made for"? When I lowered my spring plate, I had to use longer bolts for the ones that thread into the control arm, 3/8-24 trimmed to fit. I used standard 3/8-16 bolts for the ones that pass through the lower shock mount.

 

Rusty,
OT a bit however years ago I modified the handles on a snow blower for an older friend who has one arm locked at 90 degrees. he had a devil of a time managing the snow blower. I had him bring it over and told him to put his hands where he wanted the grips/handle to be. I then bent and welded a modification to fit him. That is one that I have thought would create a big ??? for a future owner.

 

I have been thru the Jag IFS tire and wheel war and am using the same tire sizes as Rusty with no rubbing. I also replaced the Jag springs since with up to 7 spacers on the old springs I still was a bit low for my taste (and comfort factor to not rub on a hard turn-I am in final paint). For what it is worth, I tested the old springs (came off a Series 1 Jag) and they were 300#/inch. You will not find any spring data from Jaguar sources-I tried. My wheels (which I changed) are now 6" x 16" with 3.75" backspace or 3/4" offset on the front and 7" x 16" with 4 " backspace or 1/2" offset on the rear. I have driven about 50 miles and I am confident that they will not rub. I am a little higher at the front bumper than I want and Rusty has but am going to drive it a bit to see if the springs settle in more. Rusty told me that he is 10 1/4" at the bottom of the front frame horn, I am currently at 11 1/4". I currently have a total of 4 spacers under/on top of the springs (2 above and 2 below the spring)and the lower spring plate is hard up against the lower wishbone, i.e. no washers. Rusty told me that he has no spacers under the springs (new springs also in his case) and has 4 standard 3/8 " washers at each of the 6 bolt locations for a total drop of the spring plate of about .300". We both have SBC so should be very close, however we are not and I know that I would be lower than Rusty using the same spacers, spring wheel and tire sizes. I suspect some spring differences even though they should be the same. Jag aftermarket support just "one size fits all" in springs or either the xj6 or the xj12. Note that Jag originally had 3 different springs.

 

This has been an interesting thread bill and thank you for it.
I am going to see how my sets soon now that I have the 302 in it