Cutting Coils: Let the hate flow....

[GeorgeJFrick]

I think people stopped cutting springs because it stopped being necessary. There are aftermarket options these days.

If you go back to the posted instructions from the book, you can see he has to immediately flip them over, etc. It's something you can kind of mess up and end up with a spring that is eating into it's perch on one end.

Another reason is that "ricers" started lowering springs by heating them up. This gave a very negative view to "modifying" springs. The general idea being that you are acting on lack of knowledge or care about the car.

I'm guessing the reason for the thread was just in case someone knew something that made sense to you and would keep you from cutting them. But you argued that you can just get another oem set on the cheap or even free. So cut the damn springs?

I'd never cut the springs, there is risk and if you DD you could end up needing a set of springs and only having 4 janky springs.

What is your plan for making sure to cut them all exactly the same length? Manufacturers have a plan and a tolerance rating. I'd maybe get a backup oem set and then go to town (carefully and methodically)

[wparsons]

Originally Posted by Chad_W

I hear what your saying, but we're being speculative here and that's why I'm looking for a calculator.

Stock BRZ rates are 153/195

Swift Sport Springs Drop 1" and are 212/252

If I calculate the stock .5" cut rates and come up with something like 185/225 it may be a reasonable experiment. If I come up with 158/200 I could expect to spend a lot of time on my bump stops.

Where are you getting the idea that cutting one of the dead coils is going to magically stiffen the rest of the spring??

If you cut the spring it's going to be the same rate as before, you've just reduced the amount of shock stroke.

If you want 1/2", get the JDM STI springs. If you're ok with closer to a full inch, there are LOTS of options out there.

Stock you have about 5mm of travel before touching the bump stops (they're progressive, not like hitting a rock), so their effective spring rate is also part of the total spring rate. You can't just ignore that either.

[Ashikabi]

Originally Posted by wparsons

Where are you getting the idea that cutting one of the dead coils is going to magically stiffen the rest of the spring??

If you cut the spring it's going to be the same rate as before, you've just reduced the amount of shock stroke.

If you want 1/2", get the JDM STI springs. If you're ok with closer to a full inch, there are LOTS of options out there.

I think the idea is OP doesn't want to spend any money to get what he wants

[Gunman]

Originally Posted by wparsons

Where are you getting the idea that cutting one of the dead coils is going to magically stiffen the rest of the spring??

If you cut the spring it's going to be the same rate as before, you've just reduced the amount of shock stroke.

By cutting the coil, you reduce the over all length, thus reducing the amount of active coils, and this increases the spring rate.

[pushrod]

Originally Posted by Gunman

By cutting the coil, you reduce the over all length, thus reducing the amount of active coils, and this increases the spring rate.

If you cut dead coils, nothing happens, besides lowering the overall height of the spring.

[Ashikabi]

Originally Posted by pushrod

If you cut dead coils, nothing happens, besides lowering the overall height of the spring.

When you remove dead coils some of the live coils will become dead, thereby decreasing the number of live coils

[Gunman]

Originally Posted by pushrod

If you cut dead coils, nothing happens, besides lowering the overall height of the spring.

You are always going to have dead coil. If the last two inches is dead, and you cut two inches off, the last two inches remains dead. The amount of active coil is reduced though.

[Hyper4mance2k]

In the 90's Honda drag guys couldn't get rear springs stiff enough to limit the weight transfer to the rear of the car, so in an effort to keep as much weight over the front tires as possible, some guys were replacing the rear springs with cut sections chain-link fence posts.
Maybe you could try that.

[pushrod]

If the dead coils were wound dead, they will NOT have an effect on the spring rate once removed. If they were dead only when loaded, then they weren't dead coils to begin with.

[Gunman]

If it's an open end coil, then there is virtually no dead section, but it still sits in a helix, which will cause the full contact portion to be dead.

Even if there is no helix for the open end coil, and you don't remove any "dead" coil, you are removing active coil, so the spring rate goes up.

If you remove the closed end "dead" coils, or the ground end "dead" coils, now your spring won't seat the way it was designed.

[Calum]

Originally Posted by Gunman

By cutting the coil, you reduce the over all length, thus reducing the amount of active coils, and this increases the spring rate.

Only if the free length stays the same. The above formula is incomplete.

The number of coils alone has no bearing on the spring rate, the number of coils per spring length does. Basically, the straighter the wire is the more force it takes to compress.

[Chad_W]

The stock springs are open on both sides, so while dead coils are an important consideration in cutting springs, they're not relevant to this conversation.

I'm going to play with this and get some results in the next month or so (my BRZ is sitting out the winter). If anyone has some extra springs they want to get rid of, I'll get started a little sooner.

[Gunman]

Looking at the set of OEM BRZ coil springs I have sitting here, both front and rear have one closed end. A closed end spring has one full dead coil.

You can see the closed end in the pictures in this thread too:
http://www.ft86club.com/forums/showthread.php?t=10842

[Chad_W]

I'm happy to hear some other input on this, but I think because they don't touch unless they're under compression, it's still technically an open end. Check out this link and tell me what you think: http://springipedia.com/compression-end-types.asp

Either way it would make more sense to cut from the lower portion that does not have a pitch change