Uneven Ride Height

[Nukski]

Hello, mar car ride height is almost 1" Lower on the passenger side but the coil over shock spring is already raised more than that amoint apposed to the drivers side. This causes a slightly softer feel to right hand turns vs left. The lenght of my spring on the passenger side is also 3/4" shorter on the passenger side. Is this a worn spring problem? Thanks to those in the know.

[BDA]

  Nukski!!

Springs don't wear but they can collapse but that is rare. Regardless what happened, you need new springs. Do you know anything about your springs such as the rate, where they came from? I would be tempted to change them all so that I was sure I knew what I had.

[lotusfanatic]

Hi Nukski!

 

Mark

[Nukski]

Thanks BDA,
     The PO had installed Spax adjustables all around. They now have 15k miles on them. Springs were changed at the same time. The fact that I have to adjust the Spax very differently to get any semblance of equal ride height is what led me to the question of springs condition. May make a good Summer project.
      Is there data on correct Springs for S2 ?

[gideon]

How long have you had the car?   Was it like this from the beginning?  Is it the front or rear springs that are unequal?

I just wonder if the PO assembled something incorrectly when the new shocks were installed.  Perhaps if you could post a few photos of the relevant suspension bits and coil-overs then that might reveal something.

[BDA]

I'll second gideon's request for pictures. We really like pictures here! 

I can't speak to the S2 but I imagine they would respond to springs similarly to the TC. There is a wide variation in spring rates used by owners. A lot depends on what kind of driving you intend to do. I would give a call to Dave Bean or Ray at r.d. enterprises for advice. I might lean toward Dave Bean because of their history of past development but I wouldn't be surprised if they both had similar advice. They will likely advise stiffer springs than stock in which case you should be prepared to adjust the shock stiffness to accommodate them. Again, their advice will be useful.

Basic rules for shocks:
1) before you monkey with the shocks, make sure your alignment is correct
2) general instability or vagueness in feel, even on the highway indicates the shocks are not stiff enough
3) stiffening the shocks increases the roll resistance which affects over/understeer
4) stiffening the front shocks will tend to increase understeer, stiffening the rear will tend to increase oversteer
5) shocks that are too stiff will not allow the tires to remain in contact with a bumpy road.

[EuropaTC]

A couple of questions....

Where are you measuring your ride height;  the wheel arch,  bumper height or underneath the chassis ? Bodywork measurements can be deceiving although they are good for comparing changes on the same car when you're modifying. Chassis datum points are probably your best bet ?

Secondly, is the 1" difference the same at the front & rear or just one end ?  to have a 1" lower ride height coupled with an extra 3/4" compression (hence pre-load) on the spring at that side is odd.

15k is no mileage for a spring, I'd be very surprised if they're anything other than their full strength and unladen lengths at that age. I would look at the rubber bushes though, one of mine collapsed at an early age.

As the others have said, photos of what's concerning you would be good....

Brian

[Nukski]

Thanks All, for your quick responses.
I have had the car for along time and always wondered why the Spax were adjusted at different heights on the front.
I am measuring at the bottom of the body wheel arch to the ground.
The rear springs are also adjusted lower on the passenger side by about 3/4" at the wheel arch. The rear springs seem soft only because I can see they rub the Spax paint off in certain places, and I creak a little when slowly going over bumps(i.e.- turning into the driveway at an angle).
I'll try to post some photos.
Possibly time to re-bush and remove the Spings to see if they have equal strength.

[JR73]

If the PO installed them then it may be worth loosening the suspension bolts and retightening them as per the workshop manual - could be that one side has been tightened up at something like full droop whilst the other side has been tightened with some load on the suspension.

It’s a bit of a long shot admittedly but if everything else looks to be correct then it’s worth checking before you start disassembling and swapping parts out.

[Nukski]

Ok, pulled the first Spring Spax coil over. It measures 10.5" in free length so it seems this was a height lowering installation years ago. Will try to pull the other side so I can measure the springs side by side.

[BDA]

It looks like the PO cut your springs. That's not optimum... It shortens the springs and raises the rate. So if he did cut it, did he cut both the same so they would be the same rate? It's not an uncommon practice and whoever did it may have known what he was doing but I wouldn't assume that.

I can't say for sure but the little I can tell from your picture, you probably should get some new springs. Compression springs for coil-over suspensions are commonly squared and ground meaning the last turn is "closer" than the others and the ends are ground flat. Your spring just stops in mid coil. That's why I suspect it was cut.

I would check into new springs from r.d. enterprises or Dave Bean. They may have different ideas of the proper spring rate so it would be worth a call to each of them. There are some good places in England for springs (and shocks) as well (eg. SJ Sportscars, Europa Engineering) so you can check with them too if you want.

[GavinT]

Agree with BDA.

The spring seems to have been cut. It also appears to be distorted on the left hand side unless that an optical illusion.
Luckily, new springs are inexpensive.

[EuropaTC]

Yep, that spring has been shortened, and not very well either because that's not going to sit evenly on the platform.  It looks to me as if someone's just taken a grinder and lopped off a coil or two.

The good news is that, as has already been quoted, new springs are cheap.  That would be my preferred option although if you want to play around first, it's certainly possible to recover the spring.

First off, unless you've got a method to test the spring rate of your shortened spring, you can always calculate it instead. Very simple to do but you must be accurate on the coil & wire diameters, plus number of coils. The formula is in the first attachment.  This is worth doing because it will give you some idea of what you've been riding on and let you decide if you want to go harder or softer with a new spring.

If you decide to experiment with what you've got (you might as well) then I'd try to get them looking right first.   The second image shows my springs as received and after shortening. It's not very clear on the lower image but basically you need to bend & grind the wire where you've made the cut and flatten it so it's like the original spring, which is clear on the top image. 

You can't do this without heat and the danger is that you'll heat up too much and lose the temper in the first active coil. I don't think it makes much difference on half coil you're flattening, but if you get heat further down then I'd reckon that's not good. It's easier than it sounds but you need a directional heat source and I usually wedge wet rags & a bit of stainless to deflect the heat away from where you don't want it.  It goes easily if you grind both sides of the last 1/3rd of the coil in a gradual taper so that when you bend it to the first active coil, it sits neatly in place. You can see this on the "as received" image.

It's definitely the Brian School of Bodging, but if you want to experiment with a slightly higher coil rate then it's fine for learning. And you can always buy a new spring at the rate/length you decide is best after you've played about. That's exactly what I was doing there, I bought a slightly softer spring (still higher than OEM), drove it and then modified it one coil at a time, adjusting the platform to get the ride height the same.  It was cheaper than buying 3 sets of springs and throwing 2 away !

Brian

[Nukski]

Thanks Gents, for your input.
    The picture I sent was not very clear but the PO did grind the end of the spring cleanly. Also when I first compressed the spring to remove from the shock it appeared to be slightly distorted, then as if by magic, it was perfectly straight again this morning.
     I am working with the formula that EuropaTC sent because I would like to estimate what the PO had installed before I order new. The car was very firm on the road so I suspect something more than the original 100 lbs.

Regards,
Bruce in NJ

[BDA]

If the spring is still squared and ground on the other end and you really want to know the rate, I would work up a rig with a bathroom scale and a ruler. Brian's equation will get you close to the rate but I didn't see where it accounted for the squared and ground end. One of my engineering books says to take off two coils for ground and squared springs but I tried to calculate the rate of one of my springs and wasn't satisfied with the results (sorry I can't provide details, it was some time ago).

To test the rate with a bathroom scale, you need two pieces of metal or wood that won't bend under the pressure of your spring, two pieces of threaded rod long enough to go through both pieces of wood or steel, the scale, plus a bit longer than your spring. Basically, you are building a clamp around the scale and the spring. Tighten the clamp evenly to generate some pressure on the spring and note the reading on the scale. Then tighten the clamp, evenly again, compressing the spring one inch further and note the scale reading. Your spring rate in pounds per inch is the second reading minus the first.