Cutting Coils: Let the hate flow....

[Chad_W]

My goal is to lower my BRZ about 1/2 inch, increase spring rate slightly and increase dampening dramatically.

Bilstein B6 Shocks will take care of the dampening and work fine with a drop of less than one inch.

There doesn't seem to be any springs on the market that fit my goals. I'm thinking about cutting stock springs to achieve this very modest change.

I don't see any issue with the result, as I will be cutting the free end of the coil and uprating my struts.

My question is does anyone have access to a good calculator and/or the dimensional specifications of the BRZ springs?

(Also I expect plenty of "Go by a '92 Civic if you want to cut coils")

[MisterSheep]

[8R6]

just get TRD springs then

[MisterSheep]

wait.. Yeah. If you only want to go about a 1/2 inch lower from stock then why not go TRD or Eibach? Eibach has good ride quality. My tein s-techs lowered me about an inch or so.

[strat61caster]

Alternatively buy lowering spring and find/make/commission a 1/2" spacer to reduce the drop, cutting the spring isn't going to significantly stiffen it as I do not believe they are terribly progressive.

[swarb]

There are easily 20+ spring kits on the market, keep searching. Cutting the spring will just make you bottom out a lot easier.

If you really want to cut the spring, just cut one coil and be done with it. No calculator needed.

[Racecomp Engineering]

The JDM STI springs would work well for you. 15mm drop.

- Andrew

[go_a_way1]

cutting springs also weakens them near the cut and makes them prone to snap near the cut

[Chad_W]

Originally Posted by strat61caster

Alternatively buy lowering spring and find/make/commission a 1/2" spacer to reduce the drop, cutting the spring isn't going to significantly stiffen it as I do not believe they are terribly progressive.

That was the road that I was going down initially, but then I started to think why buy something to lower and then buy a spacer, when modifying the existing spring for free would help me achieve my specific goal?

[go_a_way1]

Originally Posted by Chad_W

That was the road that I was going down initially, but then I started to think why buy something to lower and then buy a spacer, when modifying the existing spring for free would help me achieve my specific goal?

umm maybe safety? but hey if you like living on the edge go for it. I just hope our insouciance doesn't go up if you crash

[Chad_W]

Originally Posted by Racecomp Engineering

The JDM STI springs would work well for you. 15mm drop.

- Andrew

Thanks for your input Andrew. I really respect anything coming from you or Myles.

Can you tell me why a well measured cut of the factory spring wouldn't be a cost effective way of achieving my specific goal?

[Chad_W]

Originally Posted by go_a_way1

umm maybe safety? but hey if you like living on the edge go for it. I just hope our insouciance doesn't go up if you crash

Can you explain in what way cutting the springs will weaken them?

I understand that the lower you go, the higher the spring rate needs to be in order to prevent the suspension from bottoming out. If you go too low the increase in spring rate may not be appropriate for the ride height, but for what I'm doing that should not be an issue.

Are you referring to action of heating stock springs to lower? That can cause issues, but I wouldn't go that route.

[go_a_way1]

Originally Posted by Chad_W

Can you explain in what way cutting the springs will weaken them?

I understand that the lower you go, the higher the spring rate needs to be in order to prevent the suspension from bottoming out. If you go too low the increase in spring rate may not be appropriate for the ride height, but for what I'm doing that should not be an issue.

you will be heating the metal up when you cut it and that will weaken it near the cut point. Is it likely going to fail... no, but there is a greater chance and why take that risk?

You ride will become much softer and bouncy and to boot you will ride on your bump stops a lot during hard cornering and this will upset the car and lead to unstable (possibly unsafe) cornering. You really should just buy some used spring if you are looking to save a buck.

Edit: its not hard to hit the OEM bumpstop with everything stock

[renfield90]

Originally Posted by Chad_W

If you go too low the increase in spring rate may not be appropriate for the ride height, but for what I'm doing that should not be an issue.

Strongly disagree.

Bone stock the suspension spends a lot of time riding the bump stops. That's fine because it was designed that way. A cut spring is only marginally stiffer, this sample calculation (https://www.eatondetroitspring.com/c...-calculations/) shows a gain of ~18lbs/in (and remember, rear motion ratio is under 1 - if you don't know why that matters, stop here, do not pass go, do not cut your springs).

That sort of rate gain is in no way going to make up for 0.5" less travel. You will spend more time on the bump stops and go deeper into them (past the progressive zone and straight into the hard bump stop), resulting in a much harsher ride. A basic set of drop springs with appropriately sized bump stops is going to be much nicer than what you're trying.