Rear Ride height

[mdf]

For some reason my S1 Elan sits too low in the rear. I need to raise my rear ride height. What is the best way to do this. I have adjustable spring perches and they are already cranked up as far as they will go. The springs are the ones that came with the car they are 12" long. I don't know waht the rate is.

Are there longer springs available? Should I try spacers? I would like to get an inch or two more ride height in the rear. Any sugestions appreciated.

Michael Fatsi

[elancoupe]

You may just have fatigued springs, as 12" should be a serviceable length. There have been instances of some springs sold by a US supplier experiencing premature fatigue (don't ask me how I know this )

If you decide to order new springs, some kind of determination of what your front and rear spring rates are is important to the cars handling characteristics. Since you have adjustable perches, it is very possible that the rates have been changed from stock.

If you are able to determine the rear rates and other dimensions, you are not limited to buying from a Lotus vendor, one of the top spring companies can certainly supply the correct spring as well.

When you have the rear apart, checking the condition of rear shocks, wheel bearings, donuts/axle joints and bushing should be considered.

[cal44]

Springs start losing their spring around 10 years and it is all down hill from the there. People fight me all the time on this. Springs are cheap so I don't understand when those same people tell me all one needs is new shocks..............NOPE.

And what Mike wrote.

mike

[rgh0]

Michael
A new set of springs is in order. Your current ones must be near coil binding on full bump and adding a spacer will make it more likely to occur as they continue to deform and loose their length over time.

As you have non standard small diameter rear springs and adjustable perches you need to determine what spring rates are fitted front and rear in order to determine what replacement you should fit.

Spring rate is easily calculated. You need to measure the wire diameter, the number of working coils and the outside diameter of the coils to determine rate. The required free length to get the right ride height can then be determined once you know the rate and the length required at normal ride height and load with the platforms set approaximately mide range.

Mike - "springs start losing their spring"? I presume you mean springs start losing their freelength over time and need replacing ( or resetting and re heat treating) - I agree with this. How long it takes depends on the spring material and heat treatment and stresses involved in their use. The front plus 2 springs are very highly stressed no matter what design options you choose and unless hot formed out of top quality material will deform and loose free length over a few years. The Elan rear springs on the other hand are relatively lightly stressed if properly designed and rarely deform even over an extended time unless poorly made in the first place. The actual spring rate of a spring however never changes over time as it is determined by the bulk modulus which is a constant property of the steel (G) and the springs physical dimensions.
cheers
Rohan

[englishmaninwales]

Lots of spring rate calculators on line e.g.
http://www.ridetech.com/info/spring-rate-calculator/
http://www.pontiacracing.net/js_coil_spring_rate.htm
http://www.reliablespring.co.uk/calculator.htm

Malcolm

[cal44]

Rohan............you mean "springs start losing their spring" isn't an engineering term?.............dang it

mike

[rgh0]

[mdf]

I neglected to mention that my Elan does NOT have the Chapman strut set up it has an independant rear end. I think that the solution to my ride height is to switch to 14" rear springs. Any other folks out there with independant rear running 14" springs?

[rgh0]

The Spyder wishbone rear end especially in its earlier versions had a number of problems with the spring design
I suspect you need to redesign the springs being used as they are probably overstressed. A longer spring of the same design may restore the ride height only temporarily

cheers
Rohan

[mdf]

Why would the longer springs only be a temporary fix????

[rgh0]

If they are of the same design as the current springs, just longer, then they will be overstressed like the current springs appear to be and thus collapse in a similar way over time until you get to coil bind on full bump and you need to replace them again.

You need to check the spring design versus the loads and ensure the spring material used can withstand the stresses imposed

cheers
Rohan

[mdf]

Thanks to those who offered advice. As it turns out my car has the latter type Spyder independent rear suspension. I had to call Spyder to figure this out. With this set up the car needs 13 or 14" springs to provide sufficent ride height. I also discovered that it is impossible to obtain anything longer than a 1.9 x 12" spring in the USA.

The options available became stack 2 - 7" springs on top of each other and use some sort of coupler/seat. Or purchase 14" springs in jolly ole England. I went with the 14" springs problem solved.

Thanks again.