Discussion topic - What weight helper/tender springs to fit?

[amallagh]

I've just ordered a coil over kit for my 914/6GT rear Bilsteins suitable to take 2.25" ID springs. I havn't bought the springs yet.
This is a prelude to maybe fitting a bigger engine and 915 box to handle the power. It will also allow me to set up the corner weights better due to the adjustable lower spring perch.

I currently run full width Weltmeister SP180 rear springs and just found the following info on line about them -
http://www.914world.com/bbs2/index.php? ... ntry696531

- which if it is to be believed would indicate that they are in fact a dual rate spring - 100lb spring up to 340lbs force and 3.75" compression, then a fraction over 160lb spring after that. Static rear corner weight on my car is about 600lbs just for reference.

I had been planning to up the main spring rate to 200lbs but having seen this link then I'm a bit hesitant to go more then 180/185lbs for my main spring as the SP180 have felt about right for a fast road/rally car. I'm assuming the 180/185lb springs would be a small step up which could also deal with the modest extra weight of a slightly larger engine (2.8 ) and a 915 gearbox. Either way, they are easy to change if I decide they aren't stiff enough once the engine/box is changed, but that may be some way off yet.

I've measured one of the rear Bilsteins and there is room to fit a slightly longer total spring length with the coil over kit than the current length of the Weltmeister SP180s. Need something about 15/16" overall length to take up any slack but the adjustable lower spring perch it isn't so critical.

This brings me to the main point of this discussion thread -
What weight of helper/tender spring to fit ?

After a load of reading on-line then I'm thinking a proper dual spring set up is a waste of time. Interested in.

This would leave me with 2 distinctly different options -

1) 180/185lb x 12" + 4lb x 4" helper spring just simply to take up the slack

2) 180/185lb x 12" + 230lbs x 4" - I'm thinking this would create a bit more wheel load on the inside wheel when hard tight cornering. Compared to the set up above under the same lateral cornering force the car would drop a bit less on the outside wheel and rise a bit more on the inside wheel. I think body roll would remain about the same overall as the same overall axle load has to be distributed between the 2 wheels. The intent is to maintain better inside rear wheel contact on hard tight cornering and hence reduce inside rear wheel spin.

Does this make sense ? or am I barking up the wrong tree and should I just stick with set up 1) ?

Of course there are many options in between these 2 in terms of helper/tender spring weight but the principle is there, i.e. is it worth increasing the tender spring rate to improve traction out of tight corners ? or are there any other benefits/disadvantages to this set up ?

Tender/helper springs are sold in a wide range of weights so there must be some reason or intent behind this ?

Any advice from any suspension experts out there would be much appreciated before I commit to some new springs.

Cheers
Andrew

[amallagh]

Have I raised a conundrum or does nobody give a s__t

Still looking for an answer if anyone has any knowledge on this topic
Andrew