Rear coilover trouble

[nickso]

I'm using helper springs on my rear coilovers because the spring kept dislocating when it was jacked up and I heard it was an MOT fail but now have a new problem.

I put the helper above the main spring but now the cup at the top of the piston and the spacer between the helper and the main spring interfere with each other and I often hear them moving about when giving the car some stick. If I jack it up they almost always lock up in a silly manner when jacked back down. The cup and the spacer have almost no lip on them and this is what is making them dislocate when they contact.

Before I go to the hassle of swapping the helper to the bottom for a try I though I would ask what others have done.

Thinking maybe the best option is to get a longer main spring. I need longer ones for the front anyway as it's at its max travel now and it still a bit too low for me.

[handpaper]

Helper at the bottom is actually the correct location - it minimises unsprung weight when the wheel is unloaded!

[Demlotcrew]

Helper at the bottom is actually the correct location - it minimises unsprung weight when the wheel is unloaded!

I dont think thats quite correct, helper at the top eliminates unsprung weight.

You could weld the main and helper together and get them powder coated?

This is not a bodge and many race cars have this done for the exact reason you mention.



In the photo above the spring is a tender NOT a helper but the principle is the same.

Andrew

[nickso]

Hmm, not a bad solution.

What's the difference between a tender and a helper? That tender looks a good deal thicker and longer than the helper I have on the car.

[Demlotcrew]

Hmm, not a bad solution.

What's the difference between a tender and a helper? That tender looks a good deal thicker and longer than the helper I have on the car.

A tender spring is designed to produce a progressive over all spring when combined with the main spring.

A helper spring adds nothing to the total spring or wheel rates and is only there to keep the main spring from falling off the perches/seats.

Today you can get progressive springs made in any size (ID/Length) and in any combination of spring rates.

I have a progressive spring rate on the back, quite a few race teams have had great success with this combination on the E30.

This is my rear, you can see the coils getting tighter towards the top of the spring.



Andrew

[GeoffBob]

That tender looks a good deal thicker and longer than the helper I have on the car.

The tender spring is on top, the main spring below in that pic. Notice how the tender spring has an almost flat cross-section to allow the coils to stack up on top of each other, after which the main spring takes over.

From Herb Adams' book Chassis Engineering:
"A study of the optimum spring rates for a car eventually came to the conclusion that the best spring rate is a variable one. We would like to have a low spring rate to absorb the road irregularities, and a high spring rate to absorb the larger bumps"

[nickso]

Cheers guys.

Andrew I notice you have a helper at the bottom of your spring. I take it you have no such issues with your setup?

[Demlotcrew]

No problems at all, not ideal for it to be under the spring but it works.

[rix313]

Did Curtis fit them or was this something you added Andrew?

[Demlotcrew]

I speced them, I have actually ordered more springs at a cost of £460! these are too soft sadly.

Andrew