Yesterday was a big milestone for me: the body is finally back on the chassis for the first time in 30 years. The mating went better than expected, but it confirmed what I had suspected before. The rear end sits way too high on the replacement leaf springs I purchased from SNG. I am not trashing SNG here. What I would like to know is if anyone has specific experience with these springs and how much I might expect them to settle once the car is back on the road. I don’t want to throw more money at this issue if it is not necessary, but I also don’t want to finish the car and have the rear end jacked up like a 60s dragster. Right now the rear end sits about four inches too high. It will drop a little when the tank is full, the spare is in the boot and the interior installed, but i suspect it will still be several inches too high. That seems like a lot to expect from the springs settling in. Does anyone have experience with these and what is your counsel?
Did you compare them with the arch of the old springs?
Are they well greased?
Could the shackles and front bolts be too tight?
Figure a spare tire weighs 50 lbs and a full tank of gas weighs 100 lbs.
I Have replacement leaf springs on both my XK140 and XK150 Both from SNGBarratt.
Both cars have the right ride height, very pleased with them.
They will settle down when your car is fully assembled and you take it for a spin.
The new springs supplied by all do make the cars sit too high at rear.
Certainly your car will drop down when finished etc but you will find it will be to high see the pic of this car restored by jaguar and it is way to high at rear.
The Xk140fhc above lovely colour I would say is about right at rear but from front seems to be a smidge to high?
Whether lowering front on torsion bars will raise the back which then would make it to high.
Terry
photo shortly
If you have installed the springs, preload the rear ( I used bags of play sand) and bounce the car multiple times to settle the springs. If that does nor change the ride height you can take the springs to a spring shop and they can change the curvature of the springs. On mine I had a set made to order for no dip on high speed cornering because the original set was too soft.
Thanks for the input guys. My old springs were not original and did not match each other. The new springs had enough arch that I had to flatten them with clamps just to install them. Before the body was installed I used my body weight (considerably more than 150 lbs.) to bounce the chassis without getting much movement from the springs. I will check the shackles and front bolts as Rob suggests. Peter’s car looks about right to me. I always thought the tires and fender openings should form concentric circles when all was set up correctly. Unfortunately, leaf spring shops are becoming rare birds. I would have to remove the springs and send them out of town to rearch. If it comes to that, I question whether it is worth throwing additional funds at this set which never impressed me with their quality.
Ground clearance is 7-1/8" measured at the front mounting structure of the rear springs.
Here is my 7-1/8" measurement device. I made 4 of these.
Front suspension height I adjusted first with these at the rear and the rear wheels off. Then I could put the rear wheels on and check the rear, knowing the front was already right.
I took my springs apart and re-arched the top leaf to 5-1/2" by setting it across two blocks and jumping on it. Then did each successive leaf the same way until they matched the curvature of the top leaf.
It worked.
Jumping on the leafs sounds cheaper than having them rearched. I just hate the idea of taking them out since they were such a pain to mount. I will use your method to set the front height since it takes the exaggerated height of the rear out of the equation. That just leaves the alignment of the front wheels to worrying about while the rear decides to settle in.
You jumped up 'n down on 14 different leaves?!..got any videos of THAT?
Sorry, it wasn’t that dramatic, wouldn’t win an oscar. On the other hand, people put some pretty stupid things on social media. 
Think tik-tok…
Hi Bob, I know you fitted SNG springs some time ago. I’m just about to replace the leaf springs on my XK150 the SNG springs come in at a very tempting price. Can you give me your thoughts on them before I buy all the parts. Cheers.
Rod, I know there are others who have been pleased with the SNG springs but I cannot recommend them. The arc was off on my new springs and as a result the car sits four inches too high. I don’t know if the rear end will come down after driving it for a while (I am still restoring the car), but I have already prepared myself to buy another set. There is a company in Detroit which custom manufactures springs called Eaton Springs. At one time, I gave them the original specifications for the 140, so they should still have them. If you want to send me your email, I can send you a handwritten spec sheet from a company in England which claims they have been using those specs since the 1950s. Unfortunately, I cannot remember the name of the company. Finally, Coventry Auto Components in England sells a set which they claim meet original specs. My bottom line, don’t source leaf springs from SNG. It is worth spending a bit more and getting something you will be pleased with. The 150 has one more leaf than the 140 if I recall correctly.
Bob
I have the 140 leaf springs from Coventry AC, they look OK at the moment but again the car has not been driven. Judging by the labels on them, they were made by BCC.
I’m a bit concerned that the car is sitting exactly right, with zero miles on the springs. My experience tells me that a little high is a good thing as leafsprings can settle a fair bit. I wouldn’t worry too much about yours until you have a couple of hundred miles on them, myself.
I use Eaton Spring in Detroit a lot, weirdly, as I am in the UK. I have bought a lot of Mustang springs from them over the years and they are very good. I believe they supplied Ford as OEM back in the sixties.
The company I could not remember may be Owen Springs in the UK. If the SNG springs only sat an inch high, I would not be sweating it, but four inches is a lot, and even if they do settle, I can’t imagine they will settle precisely the same amount. The SNG springs are also square cut, whereas the originals were tapered and have oval ends. So, the price is attractive, but if I have to replace them it will be expensive.
Bob thanks for your reply. I’ve heard a mixture of reviews from SNG customers, the price seems to good to be true so probably is! I’m going to try and do the job myself so don’t want to be struggling with poor fitting components and then have to replace them. I tried to make a start in getting the old springs off this afternoon. I think it might take a while 
At least I’ll have more time to research replacements.
With regards to getting springs from the States, wouldn’t it be best to find a U.K. supplier import taxes etc.
I was also thinking of getting my original springs reworked, but no spring workshops that I can find here in South Devon.
Thanks again. Rod.
I believe Owen Spring is in Sheffield, so at least you are on the same island. Finding someone close by isn’t always the ticket. Sometimes it is best to pay the freight and find a specialist. The key would be whether they can reproduce the 150 leaf springs to original specs. Mine may be a particularly poor set from SNG. To see if they would compress, I placed two 40-gallon trash bins in the empty cockpit and filled them with water. That is about 640 pounds. The car still sat about 1 1/2 inches high. Not good.
It does sound as if they might end up high, Bob, but springs do settle over the first six months or so, sometimes quite a bit. Rod, it makes huge sense for me to buy Mustang springs from the US, as that’s where they were made originally and Eaton were the OEM suppliers. Their catalogue has a huge list of stock springs for those cars, with the correct spec. for each model from base model six to full GT, and the option of changes to stiffness and ride-height etc. No one in the UK can even come close to that. I’d never buy Jag springs from the US though.
I’m pretty sure BCC springs (Coventry Autos top range) are made by Owens of Rotherham, but couldn’t swear to it.
There’s also Jones springs in Birmingham, another old company I’ve found very helpful in the past with the Cobra’s transverse leafs as they were happy to copy a set of sixties factory drawings. For me, being in Birmingham is always a good sign for an engineering company…
This chat is quite timely as I am removing the leaf springs from my early 1950 XK120 OTS as one leaf spring broke on a road trip a week or so ago. The leaf springs are original to the car and have never been removed previously. Looking at Coventry Auto’s springs they are part number C5721 which is for the later 120’s whereas for my car the part number is C3661. Does anyone know if the specifications are the same even though they are different part numbers.
Regards, Geoff
670203
Hi Geoff, no they are not the same.
The C3661 has 3 leaves @ 7/32" thick and 4 leaves @ 3/16" thick.
The C5721 has 5 leaves @ 7/32" thick and 2 leaves @ 3/16" thick.