jag irs spring rates?

[bakbutler]

I'm looking for a suggested starting point for spring rates on jag irs rear. Will be going to QA1 shocks. rear wheel weights - left 706 lb. right 702 lb. Car will be street driven with limited track time. Firm, not harsh ride is preferred. i realize that a variance one way or the other might be necessary to suit my preference.
Thanks for any suggestions
Leo

[RICK LAKE]

bakbutler Leo Hi, Couple of questions, Is this with your weight in the cars driver seat? Are you running a rear sway bar? What is the front spring rate and are you using QA1 shocks? You know that the suspension setup for the track will kill you on the street. I race 17" wheels and tires, but run 15" for the street for a softer ride. Also what is the front end weight and what motor are you running. Have you had it aligned? Did you have someone look at the bumpster for the car. Not trying to be a smarta$$ with the question but, there is a big differents between street and track. I also have my front shocks from ERA for the street. What motor are you running, HP and torque, aluminium heads,and guess about the weight? Help us out and we will point you in the right direction. Rick L.

[ERA Chas]

I find 300-350 is a good starting point for combined use.

[joyridin']

Don't forget that Butlers and Arntz Cobra's have a weight distribution of somewhere near 52-58% in the rear, so the springs handle a bit more weight than normal. Not sure if other cars have this weight balance or not.

I will look at my car later today and see if I can find a spring rate listed.

[ERA Chas]

My ERA is 48 /52 with driver and 350's are effective.

[RallySnake]

Leo,

I am very glad you brought this up, I have been wondering the same thing. My Arntz has stock XJ6 springs on the 4 KYB coilovers. These are probably rated at 200 lbs per inch and a little too soft. The car is very comfortable for long distance rallies this way and just soaks up rough roads. However, my problem is scraping the frame on the road when we hit a big dip. My co-driver and I weight in at 455 together. So, I would like to step up to a little stiffer set of springs. Anyone know where you can get stock size springs?

Another thought I had is to replace two of the coilovers with air springs. That way, I could adjust the ride height and stiffness based on the event (rally versus autocross) and number of occupants.

Paul

[patrickt]

Originally Posted by RallySnake

These are probably rated at 200 lbs per inch and a little too soft. ... Anyone know where you can get stock size springs?

FWIW, the stock ERA 427s have 250 up front and 350 on the rear (Jag). AFFCO & Eibach are recommended. I have the optional ERA rear with 400 lb Eibach springs. Eibachs are available everywhere.

[bakbutler]

Hi Rick and all
Thanks for the quick response. A little history on my car.
Balance 48/52
Rear wheel weights are with driver
Engine fairly mild 351w Guessing at 350 flywheel HP Not sure of torque
Front Wheels 26x10x15 Rear wheels 28x12x15 MT S/R. 3:31 rear ratio. Top loader transmission. Hope to soon swap out MGB front end for "Fast Cars" complete front end. This will save 80 lbs on front of car, plus addresses the problems of bumpsteer, and ackerman and gives total adjustment to camber, and caster. I am going to QA 1 proma stars replacing Bilsteins (cannot determine spring rates) on the rear end. I am familiar with the difference between race and street suspension (I hold SCCA and TCRA competition license) and have competed in GT1. I am looking for a firm but not harsh ride, and am willing to change set-ups if and when I track the car (not comfortable racing without a full cage however).

Thanks
Leo