Coilover spring rates for comfort

[solidONE]

Originally Posted by fatoni

I imagine it has more to do with not riding the bump stops under normal circumstances

I'm sure it can be a contributing factor. Bumpstops... very interesting.

[Racecomp Engineering]

It's bump travel and valving that make the biggest difference.

Slam the car and you're going to have a bad time. Poor valving will do the same.

HOWEVER...spring rates still play some role. Just less than other factors and less than most think.

- Andy

[raytrix]

Originally Posted by solidONE

I'm sure it can be a contributing factor. Bumpstops... very interesting.

You only start worrying about bumpstops when
A: you reduce your stroke to where the bump stop is within a inch from it
B: having super soft spring rates will dip lower than stiffer springs

[wparsons]

Originally Posted by Barbecue

I am having my coilovers built and can choose any spring rate I want. Is 5k/6k good for comfort or too soft? I care more about comfort than track performance.

I have 17x9 +35 TC105N and will be using 245 or 255 Michelin Pilot Super Sports

I have the following installed.

Whiteline front lower control arm bushings
WL front caster bushings

WL rear upper adjustable camber bushings
WL rear subframe bushings
WL rear trailing arm bushings

If you're going for comfort, why are you getting tires with stiff sidewalls (harsher ride) and stiffer bushings (more NVH)?

[solidONE]

Originally Posted by raytrix

You only start worrying about bumpstops when
A: you reduce your stroke to where the bump stop is within a inch from it
B: having super soft spring rates will dip lower than stiffer springs

A: According to another member's measurements, the factory suspension only has 5mm of compression stroke from static ride height before the bumpstops are engaged.

B: Do you consider factory spring rates "super soft?' I dont believe there is any company offering springs for this car with lower spring rates than factory springs.

[CSG Mike]

If you're hitting the bumpstops, you have other issues to worry about. You're either:

1. Too low
2. Too soft
3. Too low AND too soft.
4. Went hellaflush and DGAF.

[Racecomp Engineering]

Originally Posted by CSG Mike

If you're hitting the bumpstops, you have other issues to worry about. You're either:

1. Too low
2. Too soft
3. Too low AND too soft.
4. Went hellaflush and DGAF.

Everyone with a stock FRS or BRZ is hitting the bumpstops. The car essentially rides on them.

See this thread and post below:
http://www.ft86club.com/forums/showthread.php?t=52061

Originally Posted by Racecomp Engineering

This car is very bumpstop active....

You're very close to our measurements....about 5mm of bump travel before you start touching the bumpstops.

Drop the car an inch and you're about 20mm into the bumpstop at rest. The spring rate of the bumpstops is progressive and ramps up by that point to be fairly substantial. This is why a lot of cars with big drop springs, OEM bumpstops, and soft-ish front rates lead to understeer. The coil spring rate ratio (soft front / stiff rear) doesn't mean all that much if you are rolling in progressively firmer and firmer bumpstops and quickly overloading your outside front tire.

EDIT: this is for the front, I don't have the rear numbers off the top of my head but yes you need to use the motion ratio to get correct numbers.

- Andy

And it's designed that way on purpose...it's one way OEMs have been doing things for a while now. Different advantages and disadvantages. You don't feel it "hit" the bumptops as they essentially act as a second (and very progressive) spring. The "hit" people feel is likely bottoming out the shock.

Things definitely get extra crappy when you go low and soft.

- Andy

[CSG Mike]

Originally Posted by Racecomp Engineering

Everyone with a stock FRS or BRZ is hitting the bumpstops. The car essentially rides on them.

See this thread:
http://www.ft86club.com/forums/showthread.php?t=52061





- Andy

I've always wondered if this was done on purpose... because the bump stops aren't SUPER stiff. There's a lot of design/engineering hacks on this car that are blatently done on purpose, which is why I even wonder at all.

[Racecomp Engineering]

I've got a lot of theories, but would love to talk to one of the factory engineers.

The idea is used on a lot of cars though...BMW has been doing it for years.

- Andy

[Anthonytpt]

The engineers use an aimbot.

[CSG Mike]

Originally Posted by Anthonytpt

The engineers use an aimbot.

Sorry I had to.

[ame="http://www.youtube.com/watch?v=NYGlWjIKoY4"]Aimbot - YouTube[/ame]

[raytrix]

Originally Posted by Suberman

This thread may be illuminating:

http://www.ft86club.com/forums/showthread.php?t=52061

If this is fact, and I have not tried to check the length of the bump stops myself, then steel spring rate on these cars may not be very relevant to how coilovers might change ride and handling.

The bump stops on the coilover dampers would also need to be compared to stock bump stop rates and lengths.

If bump stops are being "tuned" by the factory to add to the steel spring rate then how the coilovers are treating the same issue would be important.

For example, if the coilovers don't rely on contacting the bump stops the higher stated spring rate might not be too much different from stock.

Bear in mind that the BRZ comes from the factory with fixed height coilovers.

Coilover designs vary between companies depending on style of height adjustment. In the case of Stance coilovers the lower bracket is adjusted to raise and lower the car while retaining the spring/stroke/spring collars untouched. Now there are other coilovers where you adjust at the spring collars where you reduce the stroke as you go lower which brings you closer to the bump stop.

See below example. The KW coilover stroke changes as you lower. The Stance stroke stays the same no matter when you lower it at the lower bracket.

[Racecomp Engineering]

And I still say that's an overrated feature...in theory it can be a good thing but it's usually (not always) a cost cutting measure marketed as a must have thing.

Single adjustable coilovers usually are already shortened quite a bit to get you lower from the start. Unless you're slamming the car, you'll often times end up with more bump and more droop travel with a single height adjustable coilover.

Single height adjustable coilovers do trade bump travel for droop travel when you lower the car but with helper or tender springs you can have a bunch of droop and still a lot of bump. Plus no preload on the main spring.

Notice that JRZ, Moton, AST, KW competition, etc. all run single height adjustable coilovers. They're designed around an intended ride height range and they work very well. Ohlins goes both ways. Tein and Cusco and most JDM companies run dual height adjustable coilovers. It's not inherently bad and it IS sometiems applied correctly. But it is not the only way to do things.

- Andy

[raytrix]

Originally Posted by Racecomp Engineering

And I still say that's an overrated feature...in theory it can be a good thing but it's usually (not always) a cost cutting measure marketed as a must have thing.

Single adjustable coilovers usually are already shortened quite a bit to get you lower from the start. Unless you're slamming the car, you'll often times end up with more bump and more droop travel with a single height adjustable coilover.

Single height adjustable coilovers do trade bump travel for droop travel when you lower the car but with helper or tender springs you can have a bunch of droop and still a lot of bump. Plus no preload on the main spring.

Notice that JRZ, Moton, AST, KW competition, etc. all run single height adjustable coilovers. They're designed around an intended ride height range and they work very well. Ohlins goes both ways. Tein and Cusco and most JDM companies run dual height adjustable coilovers. It's not inherently bad and it IS sometiems applied correctly. But it is not the only way to do things.

- Andy

Absolutely agree with what you said there. This day and age most kids just want to slam the car so a single height adjustable coilover could prove pretty harsh when they bring it down to the lowest spec and then some. They end up riding on bump stops all day. Best way to avoid the bump stop riding is going with a dual height adjustable to maintain the proper stroke the coilover was valved for.