Rear Spring/Shocks Advice - S4 Elan

[William2]

My car is fitted with 5" Minilite wheels and standard profile 155 tyres. I have adjustable spring perches fitted with 2.25" springs at the rear. I only use the car for road use and have found that the springs fitted to the car seem to give a hard ride compared to normal Elan springs. Can anyone advise me on the rear spring length and rating to soften the ride and suggestions of shock absorbers as well? Ideally I would need restricted movement shocks as the drivetrain is U/Js' with sliding splines. I also want the car to have a more or less standard ride height. The front shocks and springs are Tony Thompson fast road use adjustable.

[toomspj]

On my Sprint I run TTR dampers front and rear with 100# springs 12" free length all around (1.9" front and 2.25" dia rear). I find I have a pretty good ride (Michelin 155 XAS FF tyres). The dampers are set at or close to minimum front and rear. Any more and the ride becomes harsh very quickly.
I also run a large (7/8") dia anti bar on it.

I would suggest first thing to try is setting dampers to minimum and see what that does. Do you have adjustable rears?

Paul

[William2]

Hi Paul, thanks for your reply. I have the same TTR suspension on my car. The only difference is that the rear shocks are not adjustable and came with the car. My rear springs are the 12" 95lb ones so maybe my shock absorbers are the reason for the hard suspension. Maybe I should invest in some TTR adjustable ones. I do find that I have to screw the spring perches up to a fairly high position to get a normal ride height and I guess this will have some affect on stiffening the suspension. I will check that my front shocks are on the minimum setting though.

[nmauduit]

Hi Paul, thanks for your reply. I have the same TTR suspension on my car. The only difference is that the rear shocks are not adjustable and came with the car. My rear springs are the 12" 95lb ones so maybe my shock absorbers are the reason for the hard suspension. Maybe I should invest in some TTR adjustable ones. I do find that I have to screw the spring perches up to a fairly high position to get a normal ride height and I guess this will have some affect on stiffening the suspension. I will check that my front shocks are on the minimum setting though.

under normal setting conditions (e.g. not coil bound...) changing body height would not change suspension stiffness.

The perceived stiffness results of 2 factors that are combined in operation : amplitude of motion for a given stimulus (coming from spring stiffness, typically expressed in lb/foot) and dampening (coming from the shock, which may be adjustable). It should be noted that the front ARB is also a spring of sort (responding to a differential stimulus from side to side), and the aeon limiters as well when they come into play (end of travel).

stock springs are 75 front 67.5 rear

then open to debate, fast road in the region of 150-175 front 100-125 rear

and race can go quite higher (300 and up ) depending on the track...

Shocks set very high would make the car feel stiff, regardless of spring values, as they would prevent any fast large body motion with respect to the wheel (no motion = no suspension) : if unsure of the setting, you may want to check the shocks adjustment, or reset them to the recommended value, and possibly experiment different settings, before changing parts.

[rgh0]

"stock springs are 75 front 67.5 rear
then open to debate, fast road in the region of 150-175 front 100-125 rear
and race can go quite higher (300 and up ) depending on the track..."

I would add to this that the above quoted fast road rates are the top of what most people would consider acceptable for a road car and many would say that's much to hard..

150 lb /in to 300 lb/in front springs is in the race range IMHO depending on the track and your preference and the tyres your allowed to run.

100 lb/in to 150 lb/in front springs I consider in the fast road range..

Based on what front springs you select you then need pick your rear spring rate to match using roughly the same ratio as the original setup as the starting point and the roll bar and the shocks and rear progressive rubber spring or its replacement all need to be matched to that.

There are two suppliers who will give you knowledgeable advice of Elan suspension setup in TTR and Dave Bean in my experience. Personally based on my own experiments with both at road and race level, I think TTR recommends hard setups which can be very fast but are challenging to drive in the wet and on rough tracks and are a hard ride on the road. Dave Bean likes softer setups which can be just as quick and are easier to drive in variable conditions. Neither of them will give you much about what you need to do with the roll bar and rear rubber progressive springs based on what your doing with the Springs and shocks. I am sure they know they just dont talk about it as a package which is how it needs to be viewed - racer customer secrets I guess.

cheers
Rohan