To lower or not to lower ?

[Pete Lewis]

its down to both factors 

Pete

[JohnD]

Mjit,

There's length and there's stiffness.

Imagine fitting a 'spring' that is instead a solid tube, so thick that the weight of the car cannot compress it.  Then ride height will be the same as bench fitted height.   Alternatively, a spring of thin wire, which will be compressed until the suspension meets in  the middle, or the car meets the ground!    Performance springs are usually stiffer, so that in use forces compress them less, while ordinary springs are flexible for a comfortable ride.     A stiff spring will be shorter than a flexible one, to lower the suspension and car but also because of the above.   If they were as long as a flexible spring, the ride height would be much higher.

Suspension spring manufacturers offer an almost infinite range of length and stiffness.   For the ultimate optimum performance, it's still difficult to choose exactly the right combination, which is why the dampers with an adjustable seat are used, but for road use, such precision may not be needed.      The spring maker will be able to quote the stiffness in "pounds per inch", how much weight will compress the spring by a certain amount.     That will allow you to estimate how much a stiffer spring will compress compared with the original.      The original spring stiffness, unless it is a factory fitted one (1500 Spitfire 180lbs/in), may not be known, but standing on the free spring, and having an assistant measure the compression will let you estimate that (Your weight/compression = stiffness)

Good luck!

John

PS I should have pointed out that the angled mounting of the Triumph springs is not optimal for suspension purposes, however useful it was for production.      Not only does the spring length affect ride height in a way that is related to the trigonometry, not directly, but as the suspension is compressed that angle increases and the stiffness of the spring changes, because the moment lever changes!     Cars designed as race cars almost always have vertical springs, so that none of that applies.     That's not where we are, but I hope is interesting!   J

Edited October 5, 2023 by JohnD

[DanMi]

One question. Is it that the car is sitting high at the front or could it be that it is sitting low at the back, making it look high at the front. A weak spring or disintegrated spring pads can make the rear low.

[Aristotle]

On 05/10/2023 at 12:31, DanMi said:

One question. Is it that the car is sitting high at the front or could it be that it is sitting low at the back, making it look high at the front. A weak spring or disintegrated spring pads can make the rear low.

Nope, the rear spring and dampers both new when car rebuilt, similarly those at the front. It's just the front that's higher roughly by about two and a half inches over standard ride height.

Believe it was done on purpose to allow chap who had it rebuilt to (as John Wayne used to say) "get over the ridge" as his drive fell away sharply from the road.

[Aristotle]

On 04/10/2023 at 13:37, Steve P said:

If you make the spring longer then keep fixed spring plates shocks then it would be even higher, or you may have to compress it to get it to fit in the first place.

I would go for standard fitment springs if it was mine. Yours are obviously either for another model or meant to be used with adjustable spring plate shocks.

Steve.

Quite.

[Aristotle]

On 04/10/2023 at 16:35, JohnD said:

No!   make the spring longer and the car will ride higher, but not as much as the spring was longer!

 Spring length = SQR[ Ride height^2 + Distance from the vertical of spring^2] - Pythagoras

 

OR Trig.  Tangent A = Ride height/spring length  Here's a table of the tangents of Angle A: Tangent Table Chart of all Angles from Zero Degree to 90 Degrees (basic-mathematics.com)

Good luck!

John

 

 

Many thanks for elucidation, these ancient Greeks have a lot to answer for !

[Aristotle]

On 04/10/2023 at 14:53, Pete Lewis said:

if you are only doing normal casual driving its probably (without checking) more economical to 

fit std springs and std shockers ,as adjustable are a pretty steep wallet emptier 

full kit from JP  £79 +vat etc.

what you need to find is this just the springs are tooooo long or the pans are in the wrong place ...or both

James Paddock Limited - Triumph Stag, Spitfire, TR6, TR7, GT6, Vitesse, Herald Parts and Spares Specialists. FRONT SHOCKS & SPRINGS KIT MK1V + 1500(GSA366K-2)

 

As you say - "serious wallet emptier" and as I've now discovered the alternator on the boat's packed up the budget for my toys this winter looks in serious jeopardy.

With satisfying the exchequer a necessary expedient, that standard kit from JP's is attractive, particularly as I'm more of a pootler.

Will investigate pan heights and actual spring lengths when I get to it - just to be sure.

Thanks again.

[JohnD]

6 hours ago, Aristotle said:

Many thanks for elucidation, these ancient Greeks have a lot to answer for !

On the contrary, they provided a lot of answers!     Although the Egyptians knew about right angled triangles before they did.

[Mark B]

In my opinion cars look better sitting low. I have lowered Spitfire's, Vitesse's etc. My very original untouched, rat look (rough looking) mk2 gt6 still had all the original springs, shocks fitted, 20 years ago when I purchased it. It always sat very high at the front, but was  comfortable to drive. I lowered it, and looked great to my eyes, but was uncomfortable in comparison. I ran it for years like that, but with the increasing amount of speed humps, etc. I used the car less and less. Recently I raised the front end with one inch spacers, I previously had removed the one inch lowering block from the rear. I have the original springs somewhere, and one day may reffit. Originally Spits and Gt6's sat suprisingly high at the front, but lots have been lowered, so you forget what they looked like out of the factory. Personally I would fit as close to original spec springs, shocks as possible for a road going car, more comfortable, and you can just about navigate speed humps, cushions? etc. Without ripping the bottom of your car off.

[AlanT]

Mine (recent resto) has a totally standard set up (all new and from Rimmer) and sits quite low. It rides really well. The factory setup is actually very good when well maintained…and parts are cheap! 

[AlanT]

I suspect that new ‘standard’ is actually lower than original ‘standard’ anyway.

[Aristotle]

On 08/10/2023 at 11:40, Mark B said:

In my opinion cars look better sitting low. I have lowered Spitfire's, Vitesse's etc. My very original untouched, rat look (rough looking) mk2 gt6 still had all the original springs, shocks fitted, 20 years ago when I purchased it. It always sat very high at the front, but was  comfortable to drive. I lowered it, and looked great to my eyes, but was uncomfortable in comparison. I ran it for years like that, but with the increasing amount of speed humps, etc. I used the car less and less. Recently I raised the front end with one inch spacers, I previously had removed the one inch lowering block from the rear. I have the original springs somewhere, and one day may reffit. Originally Spits and Gt6's sat suprisingly high at the front, but lots have been lowered, so you forget what they looked like out of the factory. Personally I would fit as close to original spec springs, shocks as possible for a road going car, more comfortable, and you can just about navigate speed humps, cushions? etc. Without ripping the bottom of your car off.

My thoughts too - I want to get it lower but still a comfy ride, I'm only a pootler.

[Aristotle]

On 12/10/2023 at 19:25, AlanT said:

Mine (recent resto) has a totally standard set up (all new and from Rimmer) and sits quite low. It rides really well. The factory setup is actually very good when well maintained…and parts are cheap! 

I am most impressed with your garage floor - the car too.

Photo's snap and snap.

[JohnD]

Vert nice!   Let's hope it doesn't stay that clean!

John