Rear spring rates

PeterCrespin · Post by **PeterCrespin** » Sat Jan 31, 2015 11:19 pm

Thanks for the tutorial. I figured as much on material, but didn't know the size of the effect or lack thereof.

It'd be nice to have a name?

Pete

jag68 · Post by **jag68** » Sun Feb 01, 2015 7:17 pm

Oh yeh I keep forgetting about that

Terry Sturgeon

Post by **mgcjag** » Mon Feb 02, 2015 3:34 pm

HI All.......just had a response from Julian Barratt at SNG......he has read the concerns posted re the rear springs and will respond to any customers who contact him.......Steve

Simonpfhc · Post by **Simonpfhc** » Mon Feb 02, 2015 8:30 pm

Had a reply back from SNG today. It's so re-assuring that these guys get back to you when they say they will - top marks SNG!

Anyway, they have confirmed that they have been using the same supplier for these springs for many months now and have sold hundreds of sets, without, apparently anyone else raising an issue.

I'm not too sure if that's good news or not?? It would be great to hear back from anyone who has recently fitted a set of these springs and actually got the car back on the road to get some feedback, along with a side profile photo of the ride height maybe??

Cheers.

Simonpfhc · Post by **Simonpfhc** » Wed Feb 04, 2015 9:05 pm

I removed one of the originals springs this evening to compare to the SNG springs:

You can easily see that there are more coils and the wire is slighlty thicker on the SNG spring. This sort of makes sense, as the thicker wire will make the coil stiffer, but more coils makes it a bit softer. However, tomorrow evening I plan to load each spring with the same weight and measure the deflection. We shall see.

Also, I had a better look at the shock components;

What is immediately obvious is that you definitely need the old upper dust cover fitted to the new shocks (or buy new) as this locates the top of the spring. There is a recess at the top of the cover that locates into the upper platform of the shock and a curved groove on the underside for the spring. Without this, the top of the spring is not laterally located to the top of the shock.

Cheers.

abowie · Post by **abowie** » Thu Feb 05, 2015 12:24 am

Simonpfhc wrote:I removed one of the originals springs this evening to compare to the SNG springs:

Cheers.

The spring on the right looks identical to the ones I got too. I posted the coil count and thickness in an earlier post. I'll confirm the length if I ever got out of work...

adam · Post by **adam** » Thu Feb 05, 2015 6:03 pm

Hi the parts manual for my 3.8 calls for an alloy spring locater, that goes between dust shield and spring part no C19027. On the SNG website, it also shows the part used on there assembled boge shocks.?
Adam

Simonpfhc · Post by **Simonpfhc** » Thu Feb 05, 2015 6:33 pm

Hi Adam,

You must have a very early 3.8 as that part was only fitted to the first few handful of cars along with a different lower spring seat. Looks like they modified the lower spring seat to illiminate the use of the upper packing ring.

Cheers.

adam · Post by **adam** » Thu Feb 05, 2015 7:18 pm

Sorry my mistake. Mines not that early but I have been looking at pictures of restored IRSs, sad I know some seem to have them others don't. SNG website shows them fitted to there assembled Boge shocks

Adam

Simonpfhc · Post by **Simonpfhc** » Thu Feb 05, 2015 8:40 pm

Ok, so I have load tested the springs this evening to measure the sag of each spring.

According to the factory specs found here -

http://www.jag-lovers.org/brochures/xke ... h_17_l.jpg

- i worked out that the rear corner weight is 630lbs. As there are two springs sharing the load, each spring will normally support 315lbs of weight. In real money, that is 142Kg.

I didn't have that weight at hand, but I managed to weight the springs with about 72kg, so about half the load.

The original spring compressed by 25mm.

The SNG spring compressed by just 15mm.

So if twice the weight was applied, and the compression figures are doubled, then my E-type will sit about 20mm higher with the SNG springs.

Someone with more knowledge of springs will need to confirm my logic here, as I am presuming that everyrhing is linear, so I may be wrong??

Now, 20mm doesn't sound too much, but this will be noticeable, and does prove (maybe) that the springs are wrong.

I still could do with someone making themselves known who has fitted these springs recently and can post a photo of the ride height

I may end up fitting the original springs??

Cheers.

iani · Post by **iani** » Thu Feb 05, 2015 9:04 pm

You're almost making me glad my IRS removal is proceeding slowly Simon. Seriously, good work, it would be useful to know the impact on ride height soon though, I hope to be reassembling within the next 3 weeks, I am looking to use the SNGB Shock/spring assembly and would like to know if this will be correct/acceptable.

Ian

adam · Post by **adam** » Thu Feb 05, 2015 9:11 pm

my original springs have settled I think. I have DMG springs to put on new Boge shocks, the springs look more like the originals than SNG springs. I will post results when they are on the car, its weather I use top spring locater or not?

Adam

iani · Post by **iani** » Thu Feb 05, 2015 9:15 pm

adam wrote:my original springs have settled I think. I have DMG springs to put on new Boge shocks, the springs look more like the originals than SNG springs. I will post results when they are on the car, its weather I use top spring locater or not?

Adam

Assuming you are talking about C25939 springs, can you confirm that these don't have blue and/or yellow paint marks on them?

Ian

adam · Post by **adam** » Thu Feb 05, 2015 9:45 pm

No they don't have blue or yellow paint on them. they are gloss powder coated and marked C25939*.

Adam

daykrolik · Post by **daykrolik** » Fri Feb 06, 2015 2:13 am

Last winter I was rebuilding my rear suspension (I'm doing the front this winter) on my '67 OTS. In my opinion, and the opinion of several other experts, my rear ride height was originally a bit high. However, when I sought advice on replacement rear shocks, several of the experienced posters to this forum strongly suggested that I use Boge shocks with springs from one of the usual suppliers as opposed to purchasing the adjustable-perch Gaz units, which was my original intent. Consequently, I purchased Boge shocks and springs from SNG Barratt. The rear ride height was even higher than before replacement? from what I was able to ascertain, clearly 1 1/2 to 3 inches too high. (Some posters even suggested I should wait and it would settle after a few thousand miles.) In any event, I purchased Gaz adjustable rear shocks with accompanying springs and am very happy with the adjusted height and ride. (Anyone who would like to purchase my fitted but unused Boge shocks and springs at a very nice discount please contact me.) I now feel somewhat vindicated. The issue may be with the SNG Barratt springs, but I was not in a position to buy springs from multiple suppliers and give them all a trial. All theory aside, this was my recent experience. Would I prefer springs that I knew would achieve and maintain the height I wanted as opposed to significantly more expensive adjustable shocks ? of course. But I fully understand that there are many spring variables. I hope this is of practical help to those currently rebuilding their IRS.

abowie · Post by **abowie** » Fri Feb 06, 2015 3:11 am

Simonpfhc wrote:
I may end up fitting the original springs??

Cheers.

That was my solution.

Post by **mgcjag** » Fri Feb 06, 2015 9:29 am

Hi all.....what is the rear ride height?.....there are no figures in the jag manual.....the best indicator that i can find after reading on the subject is that with the front height set acording to your model, then the rear is correct when the sill line is level......To have a rear ride height that is 3in too high, is huge and if it was down to the springs this should have been taken up with the supplier at the time to ensure that u were not supplied with incorrect items.............we now have a situation where a few forum members are strugling to to decide wether to refit there irs with the new springs they have fitted................I fitted the combined boge with springs 3 years ago and have no problems........if u have done the same very recently please let us know...But include include some measurements..... Thanks Steve

PeterCrespin · Post by **PeterCrespin** » Fri Feb 06, 2015 10:15 am

I would never expect the rear springs to 'settle' in a few thousand miles but I would expect a dramatic lowering effect by driving the car round the block versus lowering it to the ground and measuring ride height without allowing for tyre scrub. Even lowering a corner after a wheel change has it sitting way too high.

As a minimum you should either lower any raised wheel(s) onto a glossy magazine to allow slippage. or roll the car to and fro a significant distance in total, to allow the tyres to move outwards and the suspension to sit correctly before measuring. If you did all that and the car was still tail-high with the front at correct ride height, you may have been sold shocks for a heavier model IRS. If the car never moved with them fitted, it's possible they were OK.

daykrolik · Post by **daykrolik** » Fri Feb 06, 2015 3:14 pm

I did some significant rolling with a full tank of gas and weights in the boot. When I originally asked the rear ride height question on this forum, some people were kind enough to do some measurements and I got some feedback. One thing I was never sure of is whether or not with the rear camber adjustment "rear setting links" in place, was the suspension indeed supposed to be then at the correct "mid-laden" height. I spoke with several independent experts and examined a number of cars, including two that sold for stupendous prices at two well-known auctions and the car given to the New York Museum of Modern Art by the factory. I do believe rear ride height is subjective, as there was clearly some variation. For what it's worth, the bottom edge of the middle of my rear fender well is about 1 1/2" above the top of the wheel rim. It seems the challenge is just finding the correct springs. Perhaps I was not diligent enough, but am pleased with my GAZ adjustables as opposed to buying, fitting, removing, refitting various spring sets until I got the height I wanted.

KingRichard · Post by **KingRichard** » Fri Feb 06, 2015 6:06 pm

HI,

What is correct read ride height? Well I think it is when the front ride height is correct (data given by manual) and the engine is level along the inlet manifold; so no diving in at the front. Furthermore, if rear ride height is to high, I can't get the camber to be correct, but this could also be caused by my 185/70 tires (too small diameter).

Richard

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Rear spring rates

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