Jag Shock Angles Questions.

[22rdstrguy]

I was out eyeballing the Jag rear that I have and realizied that my frame is a little to wide 30 1/2 '' at the rear(originally was set up for coil sprung live axle)and the Jag shocks mounts are 29 5/8'' (frame is 1 1/2''x 3'')Quest.1) Can the Jag shocks be moved about 1'' either in or out without screwing up the geometry? Ques.2) Have any of you guys that run Jag diffs changed the shock angle and noticed any difference ie. "binding" ,etc.?

 

[PeteT]

I think you are ok to move the top shock position but it will alter the spring rate! I've seen some that are at almost 45 degrees.

One thing to beware of if you are new to Jags is the top diff mount is not horizontal! It is normally mounted at a slight angle so the propshaft flange is vertical. If you do this the top shock mount can be horizontal otherwise the top shock mount has to be at an angle (front to back) to eliminate bind. Hope this makes sense. Pete

 

[Lee_in_KC]

Moving the top shock mounts out an inch is not going to be a problem geometry-wise. As was mentioned, it will change your effective spring rate... slightly. I assume you will be using after-market coil-overs, as the stock Jag springs are way too stiff for a T-bucket. You will probably have to experiment with spring rates and lengths to get the ride height and quality you want. I'm on my fourth set of springs and I'm still not happy with the ride. Here's a pic of my rear. You can see that moving the top shock mounts out an inch is not going to be a bid deal. Mine are at stock distance.

 

[Lee_in_KC]

Here is a good explanation and chart on spring angle vs. rate...

QA1 Adjustable Coil-Over Shock Kits (11")

 

[22rdstrguy]

Thanks Pete and Lee for the info. I was going to use the CCR jag mounting Patters and I will make sure that the shaft flange is vertical. I was going to just use 1 pair of the 4 shocks is this too "soft" or will that be still? too "stiff" ?,
I was hoping to use the left over pair for the front axle.

BTW Lee, what spring rate are you using now? I thuoght I remeber someone on here saying 120-150lbs springs were just about right.

 

[Lee_in_KC]

You might be able to get away with using one stock coil-over per side. I have seen that done, but I don't know what kind of ride quality you'll get. I'm guessing it will be on the firm side. The stock coil-overs are not adjustable, so you'll have to live with whatever ride height you get.

My current springs are 180. I'm going to 165 next. I think 150 will be too soft. I started with 300 based on what turned out to be faulty logic. I went down to 250, then 200, now 180. With two people the car rides about right. With just me, it's a little firm, but tolerable. I'm thinking 165 should be about perfect.

 

[PeteT]

I've got 160lb on mine and I'm very happy with the ride. I think they were 9" long so had to wind the adjustable shocks up quite a way to get the ride height correct.

 

[22rdstrguy]

I got this spring rate from a "Jag" forum, "stock springs calculate to have a rate of 250lbs/in. " . So is that the combination for a pair of the shocks?, that would be my guess, I can't see it being 250lbs a spring for a total of 1000lbs (thats getting into hi perf. "front" spring territory @ 500lbs a side)
ie.:
A 1968 Chevelle(38600-4160lbs*) stock front coil springs are usually between 250 and 300 lbs/in and the rears have a stock rate of 90 lbs/in.

Hot Rod magazine had done a '68 Chevelle suspension upgrade ,The fronts were upgraded to 600 lbs/in, which is on the stiff side, The rear springs were upgraded to 140-lbs/in coils.

1985 Jaguar was 3,860-4,065* lbs.-

* optional engines and transmission weights(small block-B/block, I-6-V12)

 

[GAB]

What you are not taking into account on both the Jag and the front of the Chevelle is that they are attached to an arm at a point where there is leverage involved. That makes a lot of difference in the spring rates. Look at the lower control arm on the Jag rear photo shown above and note where the coilovers attach in relation to the pivot points of the arm. The same applies to the A-arm on the Chevelle.

 

[22rdstrguy]

What you are not taking into account on both the Jag and the front of the Chevelle is that they are attached to an arm at a point where there is leverage involved. That makes a lot of difference in the spring rates. Look at the lower control arm on the Jag rear photo shown above and note where the coilovers attach in relation to the pivot points of the arm. The same applies to the A-arm on the Chevelle.

I am only comparing the rear spring rates. I think I know what you are saying but(maybe not sometimes I get a little dense, so my wife said), what I was getting at is spring rate is spring rate (X amount per inch), now I realize that the jag may have more leverage, but not by much as the Chevelle coil springs are mounted inboard also, although it is a "live axle" ,I guess that could make a difference. I think it is time for me to take one apart and measure coils and to get out the calculator and do the math and for curiousity sake I'll "scale it" and find out what the true rate is.
Here is a qoute from another site (HAMB) : The best coil overs to use are from any Jag Independent Rear. Theres 4 per rear end so get all of them and use a pair for your rod and have a spare pair, or another person may want em. I'm using Jag coil overs in my T-bucket and they work plenty fine. Ill admit they maybe a little hard but not too bad. (but again that's his opinion and opinions are like.....ah , you now the rest!)

 

[PeteT]

I got this spring rate from a "Jag" forum, "stock springs calculate to have a rate of 250lbs/in. " . So is that the combination for a pair of the shocks?, that would be my guess, I can't see it being 250lbs a spring for a total of 1000lbs (thats getting into hi perf. "front" spring territory @ 500lbs a side)

I think that the 250lbs/in is per spring. My car had original Jag springs on it when I bought it, I did a rough measurement to see what they were. It sat a bit high:lol: couldn't even get it off the stops by jumping up and down. I think it was a case of solid suspension, it did bounce about a bit on the bumps :lol:

 

[22rdstrguy]

I think that the 250lbs/in is per spring. My car had original Jag springs on it when I bought it, I did a rough measurement to see what they were. It sat a bit high:lol: couldn't even get it off the stops by jumping up and down. I think it was a case of solid suspension, it did bounce about a bit on the bumps

Holy crap! Sounds like Gab was right about the leverage, Thanks guys!, at least it's pointing me in the right direction...$$$$!!!!:lol:

 

[PeteT]

Another thing you need to consider is spring length. I almost ended up with the wrong springs because I didn't take preload into account.

On the original Jag ones there is quite a load of preload (you need spring compressors to get them onto the shocks) a complete guess would be probably 1" or 250lb. So when you put them on the car, that much weight (also taking into account number of shocks and leverage as GAB pointed out) is needed to take the shock of it's end stop. On the adjustable height coilovers you don't have this preload when it is off the car, you just adjust it when fitted to get the ride height correct.

I think the original Jag springs were about 11.5" long and I tried to buy 11.5" 160lb springs. Luckly the guy selling new his stuff and pointed out that I would have to compress them quite a bit to get them on and then the weight of the car wouldn't be enough to take off this preload. So I ended up with 9" springs and these worked out fine.

Not sure if this makes sense but if it doesn't I'm sure someone else could explain it better.

Pete

 

[Lee_in_KC]

Here are three drawings I did when I was trying to understand pre-load and ride height. I ended up going with 9" springs and getting 1.5" of settling to ride height, which gave me the exact stance I wanted.

 

[Lee_in_KC]

Here's a drawing I did to better understand the leverage of the Jag. Actually, I think GAB did the original drawing with "X" and "Y" and I added "Z".

 

[22rdstrguy]

Another thing you need to consider is spring length. I almost ended up with the wrong springs because I didn't take preload into account.

On the original Jag ones there is quite a load of preload (you need spring compressors to get them onto the shocks) a complete guess would be probably 1" or 250lb. So when you put them on the car, that much weight (also taking into account number of shocks and leverage as GAB pointed out) is needed to take the shock of it's end stop. On the adjustable height coilovers you don't have this preload when it is off the car, you just adjust it when fitted to get the ride height correct.

I think the original Jag springs were about 11.5" long and I tried to buy 11.5" 160lb springs. Luckly the guy selling new his stuff and pointed out that I would have to compress them quite a bit to get them on and then the weight of the car wouldn't be enough to take off this preload. So I ended up with 9" springs and these worked out fine.

Not sure if this makes sense but if it doesn't I'm sure someone else could explain it better.

Pete

Yes it does make sense, I wasn't taking consideration of "preload" and I realize there is a big difference in leverage. I was going by just by what I understood from buying my springs for my '68 Chevelle. As you can see in the '68 Chevelle comparison (a BAD case of comparing apples to oranges) ,the springs do not really have a preload, just "ride height" preload only "appears" once the car is resting on the springs,which if you want a different ride height you just order the springs "X" amount shorter or taller and whatever lbs per inch rating you would like.
Thanks guys for clearing this up, sometimes I get myself so confussssssed! Great pics BTW.

some people have brain farts....I get brain diarrhea!!

 

[Youngster]

Pete is right about the top of the pinion housing. Mine has a 4.5 degree taper to it. A suggestion here, build your frame and set up your front axle assembly first. Get that at ride height and then set your Jag so the pinion flange is level vertically and your axles horizontally. Now build your mounts. There are so many veriables that unless you are copying an existing frame, it's going to be tough to set it up rear end first.

The same goes with the springs for your shocks. The closer to vert. they are, the less spring rate you will need. Other thing also have an effect on the springs, like steel or glass body, 8, 10, or 12 gallon fuel tank, personal ride prefrence, etc. You will have to play with the springs to get the ride you want. You could use the Jag shocks and just swap out the springs.

Ron