1965 COUPE STOCK REAR SPRINGS AND SHOCKS NOT SNG

[Heuer]

Thanks Joey!

[andrewh]

Agreed, a lot of miss information there.

I think most of us agree, but for clarity, there are three things combined that go together to make up the rear ride height on an E-type.

1. The distance from the top eyelet to the top spring perch.
2. The laden length of the spring
3. The distance from the bottom spring perch to the bottom eyelet

Change any one of those three and the ride height changes. Points 1 and 3 are dimensional characteristics of the damper component because of the coil-over design. The damping rate in both compression and rebound makes no difference to the ride height. Adding packers or spacers effectively changes points 1 & 3.

Changes in spring rate, spring free length and laden weight affect point 2. Using gas charged dampers reduces the load experienced by the spring so, for a given spring, there’s an increase in laden length.

I completely agree with this Tom. I have just compared my NOS BOGE to the original Girling. The distance from both spring perches to centre fixing eye are different. The BOGE is longer by a margin on the top. To prove the point I fitted the original springs to both a Girling again, and a BOGE. The BOGE has the distance as about 1 inch longer. That is going to irritate me so I now need to know which shocks to buy that have the correct distances , given I am retaining the original springs.

[mgcjag]

Hi Andrew...you need to check the parts catalogue and your chassis number..spacers were fitted on the shocks for some cars....Steve

[andrewh]

Yes I know about those thank you. However, the distance is too long on the BOGE so spacers will make it even longer, since they effectively lengthen the spring. I will post some photos. This is for a 4.2 series 1 and I think the spacers were only used on early 3.8s from memory anyway.

[andrewh]

this is a picture of an original Girling with original spring in the rear and a BOGE with same original spring in the foreground. You can see the effect is to increase the distance between fixing eye centres by a considerable amount. Hence the ride height is too high.
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this is my 3.8 on CMC springs with Koni rear shocks
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and this is the 4.2 with original factory springs and BOGE shocks. So there you have it! Shocks do effect ride height.
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[DWW]

Not convinced. Unloaded it is the spring stretching the shock further out but at the end of the day the spring and car weight dictate the drive height.

[mgcjag]

Hi Andrew.......what would be usefull information would be the actual measurements.....top/bottom spring perch to eye center.....for both the Original Girling...and the Boge that you have........if your car rides correct for you with the Girling then finding shocks with the same dimensions is the key......your photo is misleading with the springs at different lengths caused by the different full opening thength of the shocks you dont have to mount the spring ..just lay the shocks side by side to see if they match.....

Danny...you are missing the point...this has been discussed numerous times on the forum.....rear ride hight is determined by the 3 points listed in posts above...shock perch length is a factor.....Steve

[Bob.]

Irrespective of the ride height issue, the relatively short distance between the top perch and eye bolt of the Boge damper compared to the Girling is cause for concern. The full bump position should be checked to ensure that as the damper swings outward it does not impact the IRS cage. Consequences can be broken damper rod and/or split IRS cage as occured to this S3. (S3 has same cage but longer driveshafts than S1/2 so damper operates at a slightly greater angle exacerbating the problem)

[mgcjag]

Hi Bob....from Andrews photo above the top of the shocks is on the left as can be determined by the shock cover....the Boge top looks longer to me but the bottom looks shorter...could just be the angle..thats why measurements are needed.....or bare shock laid side by side... buy yes you are correct to check there is nothing touching....Steve

[Bob.]

Hi Steve,
Age strikes again - yes I was looking at the wrong ends of the dampers.
FWIW the Konis which came with my car only have 10thou clearance from the cage on full 3.5in bump.

[andrewh]

Not convinced. Unloaded it is the spring stretching the shock further out but at the end of the day the spring and car weight dictate the drive height.

I am not sure what you are not seeing ? The springs exert the same deflection on the shock absorbers , either the BOGE or the Girling, but the BOGE has longer extensions each end to the eye, so when you connect it to the IRS and lower radius arm it makes the distance between those two fixing points longer.

[Series1 Stu]

I think you are at crossed purposes here.

It is true that, for a given set of springs and car weight, the deflection on the springs will be the same no matter which damper they are fitted to. That is, the distance between the spring perches will be pretty much the same on both types of damper.

The spring DOES NOT exert the same force on both dampers if one damper is longer than the other. That is, if one damper has a longer stroke than the other then the pre-load of the spring will be less on the longer damper. This will, however, settle out when the damper is fitted to the car and the spring is further deflected by the weight of the car.

If the distances from the spring perches to the fixing eyes are different then the fitted length of the spring/damper unit will be different with the longer (from eye to eye) assembly giving a higher ride height.

If you want a standard ride height then, in addition to standard springs, you need a standard length damper as measured from each eye to its adjacent spring perch.

I don't know whether the SNG Barratt shocks are dimensionally correct, I think I've read somewhere here that they are, but, along with correct spring rates, it is the most important aspect of getting the ride height right. The suspension design is so good on our cars that I'm not sure that we need fancy adjustable gas dampers for general road use.

Regards

[andrewh]

I am not at crossed purposes. I can see exactly whats what as I am looking at the effect of one shock absorber over the other. I am not getting into all this technical arguing its pointless. The distance between fixing eyes with the same spring is longer with the BOGE, so the ride height will be. End of to be honest.

[Series1 Stu]

End of? For you maybe, but I wouldn't want anybody else to be mis-guided by such erroneous assertions. There is no argument here.

"There is none so blind as he that will not see".

Regards

[mgcjag]

Hi Andrew...it would be very usefull information to get the perch measurements i asked for above....many have talked about ride height befor but none as far as im aware have given these measurements....thanks.....Steve

[andrewh]

yes I will measure it when I am next in the workshop. Andrew

[abowie]

The distance between fixing eyes with the same spring is longer with the BOGE, so the ride height will be.

I don't think this is correct.

The ride height is a function of the spring strength. Putting in spacers makes the spring stronger because you have compressed it more, which is why the car sits higher with spacers.

That the shock itself is longer only means that the suspension's maximum droop can be greater, although in practise this too is irrelevant because neither shock should ever end up at maximum length while the rear wheels are on the ground and the spring is loaded by the car's weight.

All the dampers do is damp the springs' oscillations. They don't support the weight of the car.

[Geoff Allam]

I think that there is some confusion in what is being measured that is causing the controversy. The measurement that is important is the combined distance between each end of the spring and the centre of each corresponding eyelet. If this distance is the same on each shock then the ride height will be the same. Shims alter this distance so they will alter the ride height.

[Series1 Stu]

Just had a quick skim through that JL thread....there is some real nonsense in there. ........If were not carefull then this thread will go the same way as the JL one..with most thinking the same thing but it comeing across as we all have different ideas..........Steve

Very prophetic,Steve.

[andrewh]

I think that there is some confusion in what is being measured that is causing the controversy. The measurement that is important is the combined distance between each end of the spring and the centre of each corresponding eyelet. If this distance is the same on each shock then the ride height will be the same. Shims alter this distance so they will alter the ride height.

Exactly, I guess there must be some confusion as to how people are seeing this. Its not about anything technical at all. Its physical distance between centres with the same springs on different shock absorbers.

THINK OF IT LIKE THIS. TWO WIVES BUY THEIR HUSBAND THE SAME XMAS JUMPER IN THE SAME SIZE WHICH THEY BOTH WEAR TO GO TO WATCH A BOXING DAY FOOTBALL MATCH. NOW THE CROWDS ARE QUITE LARGE AND ITS DIFFICULT TO SEE BUT ONE OF THE HUSBANDS IS 6 INCHES TALLER THAN THE OTHER SO HE CAN SEE THE FOOTY. THE JUMPERS MADE NO DIFFERENCE AT ALL. HE IS JUST TALLER TO START WITH.