SIII Rear Spring Rate

Does anyone know what the stock rating is for the rear springs used in the SIII E Type? After two and a half days searching through the archives I can’t seem to find an answer. Surely, SOMEBODY must know after all these years!

I have the CJ Aldan shocks & springs installed and am considering going to a slightly softer spring since the ride is a bit stiff. I’m not sure exactly what CJ supplied for springs. These were purchased around 2001, so the invoice has long disappeared. I’m just trying to figure out the stock starting point.

Thanks,
Steve

Steve

Not a direct answer but some information is provided here:

See bottom of page 1 for Jaguar IRS data

EDIT
This provides a data point for 6-cylinder Jags
( https://www.terrysjag.com/category/PERFORMANCE-TORSION-BARS-SER1-2-E-TYPE.html ) :
Fits XKE 6 Cylinder Series.

Rear spring set (Set of 4) 10" free length with 275Lbs Spring Rate which gives a 30% rate increase compared to Stock. Fits standard 2-1/2" spring platforms. For Performance street - Autocross use.

Made to Bill Terry own specification by a leading US Spring manufacturer that supply NASCAR winners with their highly engineered springs. We bring you “Total Performance Advantage” in a box.

Also this link provides contact data for a reported Jag IRS expert. The cdiscussion is dated Aug of 2012 so . . . . :
https://www.jaguarforums.com/forum/xj6-xj12-series-i-ii-iii-16/great-new-jaguar-irs-resource-78862/

I believe pretty much all normal passenger cars will have spring rates in the neighborhood of 250-275 pounds/inch.

Regards,
Ray L.

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This guy calculated his spring rate at between 170 and 185 pounds inch, Can’t vouch for his technique nor the age/originality of the springs

https://www.jaguarforums.com/forum/e-type-xk-e-59/e-type-rear-spring-rating-147288/

I have the springs that SNG sells with adjustable GAZ dampers. Both damping and spring seat height. Nice a supple ride in my book. I adjusted the damping to settle the car after one compression followed by extension using speed bumps and sharp turns to unsettle the car. Gives a nice smooth ride and certainly not harsh.
Side note: Painted the springs “Ducati” yellow.

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A post was merged into an existing topic: Thread pages are corrupted?

Seems like I’m coming up empty again. That QA1 chart has some great information in it explaining how to do the calculations based on weight. I think I’ll be setting up an Excel spreadsheet for some plugin answers to give me a rough idea of the situation.

I’m only interested in the SIII E Type stock spring rate, not “all normal passenger cars”, but thanks anyway. My main purpose in asking this question is to do some fine tuning since I feel my current springs are a bit too stiff.

The FelineCat method may have some merit since from what I understand, the rate is based on the pressure needed to compress the spring 1 full inch. I may have to eventually resort to this.

Ole, do you know what the part number is for the spring SNG sent you? From what I see on the SNG website, it looks like they suggest C32062, which is the stock spring, but maybe they supply something of an upgraded part for the GAZ shocks. Is there anything on your invoice that would indicate this?

The Terry’s listing is for 6 cylinder E Types. Their listing for 12 cylinder E Types show only 1 item that has been discontinued and it’s description is devoid of any detailed information.

99% of the information I’ve been able to find on this subject is for the 6 cylinder cars. What I HAVE been able to determine is that the 12 cylinder cars have a higher spring rate due to the increased weight if the SIIIs. Simply resorting to the stock springs is not an option for the Aldan shocks I’m told. Rumor has it that they require their own special spring, though I’m not sure exactly why.

The quest for knowledge continues!
:open_book: :books:

Thanks,
Steve

Steve, why don’t you call Dan Moody at Classic Jaguar in Austin, TX? He was the guy who was selling Alden shocks and originally spec’d them out. He can likely tell you the spring rate.
Have you tried adjusting the damping to a softer setting?
Is your ride height at a proper level? You have adjustable spring perches. If you are too high or low you can get a poor ride. You might start at being at the middle of suspension travel with two passengers & fuel.

Also (I have Aldens on my S2), I took the springs off the dismounted shocks and found a vast difference in compression damping by pressing downward. I had to send them back to Mooney who forwarded them to Alden for rebuilding. CJ offered a lifetime guaranty when he sold them.
Lots o’ springs at Alden: (https://aldanamerican.com/custom-coilover-springs/)
Dave

Are you SURE the springs are to blame, not the shocks? If the shocks damping is too much the car will also ride hard.

This Saturday I removed one of the rear Aldans. I had the shocks set to their softest setting and the springs were adjusted to where they were barely compressing the spring at all, maybe 1\16th to 1\8th of an inch. I did find paint dabs on the end of the spring, Yellow and Blue. According to the Aldan catalog, that would indicate 550 lbs. I also found that the extended length was 15". My old Girlings measure 14 and 1\4, so that explains why I am having interference at the inner axle shaft U joint when the rear suspension is at full droop. I also found in the Aldan catalog that they only offer a 14" extended length shock before jumping to 15". I also was able to measure a set of Spax shocks and they are also at 14 and 1\4 extended length. I’m beginning to think its time to change brands. Aldan does not even list Jaguar in their applications. GAZ and Spax are looking better since they at least have the Jaguars as an application. I also did the math according to the calculations outlined in QA1s catalog for independent suspension and the answer came back as 239.63 lbs.

Much food for thought! :head_bandage:

Comments welcome.

Thanks,
Steve

Steve, Did you buy the shocks or were they on the car when you got it?
If the Terrys catalogue said his spring was 30% stiffer, so working backwards stock would be 212 lbs.
How in the hell did you wind up with 550 lbs. springs???

For what its worth, I have Gaz HPG nitrogen shocks on the front of my car. The high pressure makes them a bit jiggly on small road irregularities. The don’t want to move on the small stuff. My front Alden’s are gas bag or low pressure so they’re compliant on small stuff. Nice ride quality. Point is you may want to consider Boges for ride quality.

I went to Alden’s site and looked: four new springs are $200+/-. So a lot less than new shocks, FWIW.
Not sure if you can live with the 15" length, that might break things.

Put a small zip tie on the shock shaft and go for a ride. See how much the shock is stroking relative to the entire stroke that’s available. It’d be helpful to have the shock off the car, so you can compress the shock to full compression, mark the shaft. then put the zip on the shaft at the body at full extension. Install, and go for a ride with some good bumps.
I wonder if you could take the spring off the inner 2 shocks and wind up in the “spring rate ball park”???
Mad scientist stuff there!

I bought the shocks from CJs when they were on sale, then later sent my car to them for restoration along with all the parts I had bought from them. When the car returned, I put the engine & trans in and finished up putting the car back together. Dealing with Dan has never been a problem, but first I always had to go through his shop manage who was a horror show. There were many issues with the returned car and the shop manager finally said “no more!” and seemingly convinced Dan of the same, so I will just move on. Don’t want to bad mouth anyone. Overall, the car looks fantastic! That was back around 2001.

I didn’t see in Terry’s where they listed any rating other than saying their HP springs were increased 30%. But 30% from what?? Stock, I would presume, but again, that is the unknown quantity, at least to me, sort of.

This afternoon I did the bathroom scale measurement of my original springs, a set that I had purchased new many years ago as standard Jaguar parts, and one of the Aldan springs. Both of the stock springs were around 240 lbs, even though the older set was about 3\4 of an inch shorter, and the Aldan measured around 275 lbs. Curious, that’s exactly half of Aldan’s 550 spec. Funny, but I don’t THINK I read their chart wrong, but who knows? At least that bears out the formula in the QA1 catalog.

And no, I can’t live with the 15" length as it causes the axle shaft at the U joint to collide with the flange on the output of the diff. With the whoop dee doos we have here on the Southern California freeways, anytime your at speed there is the possibility of bouncing up to full extension of the suspension.

Anyhow, I think I’ve had enough of this and will go with a set of GAZ adjustables, ala Ole, and use my newer set of stock springs. He had mentioned that his springs were as supplied by SNG and I only see stock springs(both original and aftermarket, neither being listed as anything other than stock) listed for the SIII on their website. The Aldans will be headed for ebait sometime in the near future.

Steve

Steve, I’m pretty sure they were standard, but I’ll check my invoices and let you know.

Steve,
the springs I bought in 2011 are C32062
Cheers … Ole

Thank you Ole!

Steve