Thread: Jag Rear End Springs

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I want to increase the rate of the coil-over spings used on the jag rear end installed in my 48 Ford. I have replaced the coil-over shocks with Bilstiens, but I used the stock springs. The spings are to week for this application, so I would like to ireplace the springs and increase the spring rating by about 20%, but I don't know how to measure the stock springs rating so I can increase them.

Does anyone know where I can get the spring rating measured?

Tim

do you have a shop that builds round track race cars close by? they will have a spring tester. sometimes they will put a paint color code on the coil spring to tell you what wt. it is.

Thanks for the quick reply. The Springs have two paint stripes on them one Red and one Blue.

Originally Posted by lt1s10

do you have a shop that builds round track race cars close by? they will have a spring tester. sometimes they will put a paint color code on the coil spring to tell you what wt. it is.

What weight should they be for that car lt1s10? The reason I ask is that we went the same route (Jaguar ifs/irs) with our 47 Ford sedan, and while it's 100% better than it used to be, there is still more `body roll' than is desirable. I guess I've known that I would have to do something about it, but my knowledge of suspension matters is, to tell the truth, virtually non-existant. There are no paint `code' marks on our springs, and I have absolutely no idea what the shock absorbers are. Some idiot (me) painted everything in rattle can black before it went under the car. So I guess, what I'm asking is, what would be the best spring weight/shock absorber combination for the car?

johnboy

Speedway has avery nice chart in their coil over section. You can gain almost 20% just by standing them up straight,rather than tilting them in at the top. I'm planning to have to go in some more on my pickup because it is lighter than a stock Jag. Hank

looks like the blue/red in this chart is 400 lb. spring rating. about 1600 lbs. everything i can find says a 48 ford rear is about 1700 lbs. another 100 lbs on the rear makes a big dif. how tall are your springs?

COLOR CODE: W/White R/Red B/Blue Y/Yellow G/Green
6 INCH SPRING Weight/Code
350# Y-R
450# W-R
550# Y-B
650# B-W-Y
750# B-W-G
8 INCH SPRING Weight/Code
200# W
350# B
300# Y
350# Y-R
400# B-R
450# W-R
500# R-W-B
550# Y-B
600# B-W
650# B-W-Y
700# Y-W
10 INCH SPRING Weight/Code
100# W-G
120# Y-G
140# R-6
160# B-G
180# G
220# R
250# B
300# Y
350# Y-R
400# B-R
450# W-R
12 INCH SPRING Weight/Code
100# W-G
120# Y-G
140# R-G
160# B-G
180# G
220# R
25O# B
300# Y
350# Y-R


Y-yellow
R-red
B-blue
G-green
W-white

I have a couple of Jag IFS from late 80's They look beter than the early xjs front with the canted upper a arms and have bigger brakes. I plan on building a tubing crosmember to narrow it and finding a new rack to fit. Has anybody done this?

thanks for the chart.
Jaguar springs are 8" tall, so from that chart it looks like I would need 450lb springs, white/red, or would it be better to go a bit heavier, say 500lb?

johnboy

Originally Posted by johnboy

thanks for the chart.
Jaguar springs are 8" tall, so from that chart it looks like I would need 450lb springs, white/red, or would it be better to go a bit heavier, say 500lb?

johnboy

i believe i would use the 500 lb. rated ones, but i like the car to be a little stiff. that would be good for about 1800 lbs.

Thank you for the chart "lt1s10". I would have replied sooner, but this is the first chance I have had to log back online, I was on an airplane all day flying home to Ventura CA from Norfolk VA.

My 48 Ford is a pick-up truck and it weighs 3450 lbs total, but I don't know how much the rear weighs. The truck sits very low and rides perfectly the way it is set-up now with me and one passenger. My problem is when I add any additional wieght in the bed or another passenger the rear lowers too much and will bottom out. I was told the way to fix this is to increace the spring rating by 20-30%.

According to the chart you provided I currently have 400 lb rated springs. The coil-over springs are 9 inches long when mounted in the coil over shocks (with now wieght on them) and appox 11.5 inches when not mounted on the shocks.

Based on the chart you provided, I assume I should order the (10 inch #450 W-R) springs. Do you think that correct or will that give me the correcting that I am looking for. Keep in mind that there are four of these coil-overs mounted on the rear-end.

If so do you know where I can order these springs? the ones in most of the catalogues like speedway or Proshocks are only 2 1/2 inches inside diameter the Bilstien sholks I have require 3 inch inside diameter, (same as the stock Jag shocks).

Tim

Originally Posted by Fatfender48

Thank you for the chart "lt1s10". I would have replied sooner, but this is the first chance I have had to log back online, I was on an airplane all day flying home to Ventura CA from Norfolk VA.

My 48 Ford is a pick-up truck and it weighs 3450 lbs total, but I don't know how much the rear weighs. The truck sits very low and rides perfectly the way it is set-up now with me and one passenger. My problem is when I add any additional wieght in the bed or another passenger the rear lowers too much and will bottom out. I was told the way to fix this is to increace the spring rating by 20-30%.

According to the chart you provided I currently have 400 lb rated springs. The coil-over springs are 9 inches long when mounted in the coil over shocks (with now wieght on them) and appox 11.5 inches when not mounted on the shocks.

Based on the chart you provided, I assume I should order the (10 inch #450 W-R) springs. Do you think that correct or will that give me the correcting that I am looking for. Keep in mind that there are four of these coil-overs mounted on the rear-end.

If so do you know where I can order these springs? the ones in most of the catalogues like speedway or Proshocks are only 2 1/2 inches inside diameter the Bilstien sholks I have require 3 inch inside diameter, (same as the stock Jag shocks).

Tim

i'm up next to Roanoke va., should have stopped by. i don't know Fatfender48, about going stiffer if its riding good now. you probably don't have 1500 lbs. on the rear now and add a 200 man, would give you about 1700 lbs. and that sounds about right with the spring you have, any car you add 200 lbs. to is gonna go down some. is there anyway to raise the car up a 1" or so, might be all you need, or if the shock is leaning in at the top you can straighten it up some and that will increase the wt. cant help you on the 3" shock, i've always used Carrera coil-overs. looks like you have 3 choices, raise the rear of the truck a little, straighten your coil-overs up a little or go up to a stiffer spring.

Originally Posted by lt1s10

i'm up next to Roanoke va., should have stopped by. i don't know Fatfender48, about going stiffer if its riding good now. you probably don't have 1500 lbs. on the rear now and add a 200 man, would give you about 1700 lbs. and that sounds about right with the spring you have, any car you add 200 lbs. to is gonna go down some. is there anyway to raise the car up a 1" or so, might be all you need, or if the shock is leaning in at the top you can straighten it up some and that will increase the wt. cant help you on the 3" shock, i've always used Carrera coil-overs. looks like you have 3 choices, raise the rear of the truck a little, straighten your coil-overs up a little or go up to a stiffer spring.

Thanks for all the info, I wish I would have known you were in Roanoke, I would have stopped by. I work for the Navy (Civilian) so I may be back out there soon, if so I'll look you up. I'll check into raising the truck an inch, if possible the way the cross member is set-up, may make it tough. That's why I was considering stiffer springs. I definately need to raise it up, one way or the other, cause the camber on the rear wheels is toed out about 3/4 inch without any wieght in the truck.

Thanks again,
Tim

Originally Posted by Fatfender48

Thanks for all the info, I wish I would have known you were in Roanoke, I would have stopped by. I work for the Navy (Civilian) so I may be back out there soon, if so I'll look you up. I'll check into raising the truck an inch, if possible the way the cross member is set-up, may make it tough. That's why I was considering stiffer springs. I definately need to raise it up, one way or the other, cause the camber on the rear wheels is toed out about 3/4 inch without any wieght in the truck.

Thanks again,
Tim

let me know when you're coming. welcome anytime. i hope you can work it out, got to have the Hot Rod driving a and riding good.