Car: AP2v2
Suspension: MCS 2-way remote. 7" 750 lb/in front, 6" 700 lb/in rear. 2.25 ID.

Issue:
At full droop, my rear suspension has about 3" of space that needs to be taken up. When springs are reseating against upper spring collar, they're not always landing in the center, and the spring collar gets damaged. Would like a tender/helper spring to prevent this.

Question:
Researching on the internets has led to some confusion on my part. My understanding is that helper springs should be fully compressed at static ride height such that my main springs are the only springs that are doing the work--but some places make it seem that a tender setup is sort of a DIY prog spring setup and should not be coil bound at static ride height, which means that tender spring rates and lengths matter more than I thought they would. Can anyone confirm?

 

Well, this is a tricky issue because of nomenclature.

There are two types of secondary springs.

There is the almost zero rate type which is used to solve the problem that you are experiencing (i.e. making sure the spring stays in place in full droop by taking up the extra space).

Then there is the type that has a non-trivial spring rate that is used to fine tune the vehicle's behavior by effectively creating a 2-stage "progressive" spring rate.

Sometimes the first type is called tender and the second helper. Sometimes it's reversed. Depends on the manufacturer. This is where the confusion stems from.

In your case you want the first type.

 

Yeah after some thought i came to a smiliar conclusion. Ordered some hyperco tender springs already. Thanks for the reply!

 

Cool!

 

I know that you have already solved your issue, But it is worth mentioning for anyone who comes across this in the future.

Adding a second spring (in this case a tender spring) will change the initial spring rate more than people think. Because you now have two springs, you will see small amounts of movement from each. This lowers the initial rate by quite a bit.

FORMULA FOR SPRINGS IN SERIES: FINAL RATE = (RATE 1 x RATE 2) / (RATE 1 + RATE 2)

Example:
250lb/in Tender spring
450lb/in Main spring
Initial spring rate of 160.71lb/in

 

Where can someone find tender springs or helper springs say for a 95 integra LS.
I've searched for about 20 min and can't find anything.

 

These springs are not vehicle specific. You will need to know what the inside diameter is of the springs you need. Once you have that, it becomes much easier.
here is a link the Eibach Motorsports catalog. Everything is listed by inside diameter.
Motorsport Performance Perfected | eibach.com/america