BRZ suspension sucks!

[fatoni]

Originally Posted by mike the snake

I read somewhere that ride quality is something like 70-80% rear springs and 20-30% front springs.

If you think about it, it seems to be true. When I hit a pothole, I cringe when the rear wheels hit.

i dont think ride quality is much about springs at all but im curious to see how you came up with those numbers.

[Apoc]

Originally Posted by KoolBRZ

You do mean 9k front, 10k rear right? Because the combination of hard front and soft back springs exaggerates the tiniest of pavement ripples, making the whole car pivot on it's center. In this respect, those stiff springs are probably better, since they won't rock at all over small bumps. When I mentioned bobble-head earlier, I really meant that the back and forth bobbing motion of a bobble-head is what my car does to me over small dips and bumps. I have the Delrin steering rack mount inserts and even with soft snow tires and soft front springs it doesn't drive vaque and squishy. I think those people who want stiffer springs in front should really get Delrin inserts first. They even conduct LESS vibration than stock. since the vibration is absorbed by the chassis.

Delrin steering rack bushings will definitely not conduct less vibration. I'm not sure how the chassis could absorb vibration between the road and steering rack. The derlin bushings purpose is to stiffen up the steering by using harder materials and will transfer more vibration.. I am now convinced that you live in an alternate universe where the laws of physics don't apply. Please read the description for Whiteline Steering Rack and Pinion Mount Bushings and make a note about the sentence "As with all harder bushings, more noise and vibration will be transferred into the vehicle" http://www.42autosports.com/BRZ-FR-S...ngs_p_699.html

[Racecomp Engineering]

What you need to have good ride quality:

1. Quality damping
2. Enough suspension travel

Spring stiffness plays a role, but it's not as big as most think. Choose spring rates based on how you use the car and what kind of tires you run.

I don't think the stock FRS or BRZ rides poorly...it's fine for a sporty car at it's price point. There is room for improvement for sure though.

Better shocks help...but the keyword is "better", not just "different." There's a lot of stuff out there that isn't better.

Lowering the car with just springs is tricky since you reduce compression travel. Using properly designed shortened bumpstops helps here but most importantly, you just can't go too low.

You can go lower with coilovers and keep adequate bump travel, but with coilovers often comes other compromises.

If stock BRZ is too rough for you, then you're gonna have a bad time with any lowering. Only thing I would recommend at that point is to try Bilstein B6 dampers.

- Andy

[KoolBRZ]

Originally Posted by Apoc

Delrin steering rack bushings will definitely not conduct less vibration. I'm not sure how the chassis could absorb vibration between the road and steering rack. The derlin bushings purpose is to stiffen up the steering by using harder materials and will transfer more vibration.. I am now convinced that you live in an alternate universe where the laws of physics don't apply. Please read the description for Whiteline Steering Rack and Pinion Mount Bushings and make a note about the sentence "As with all harder bushings, more noise and vibration will be transferred into the vehicle" http://www.42autosports.com/BRZ-FR-S...ngs_p_699.html

You don't understand, when they say "As with all harder bushings, more noise and vibration will be transferred into the vehicle", they mean the whole car will vibrate more. The vibration I'm talking about is in the steering wheel, and only the steering wheel. The chassis has way too much mass to be affected by minor vibrations, only major vibrations pass through.
When the engineers moved the motor 9 inches further back, they reduced the cars moment of inertia, making it easier for bumps to move the weight balance front to rear, or rear to front. I normally carry about 75 to 100 pounds of computers and parts in my trunk, and I think that adds to the disparity when the front springs are stiffer than the rear springs. So, my solution for a good ride is not going to be the solution for everyone, just for me and my use of the car. It's more like driving around with two wheels in the trunk. In a normal car two wheels in the trunk won't do much beside make the steering a bit lighter. In the BRZ however, it changes the balance enough to force the back end down when the front end comes up, like a see-saw. It's this forward to back rocking sensation that I really hate with a passion of undying fire. That sensation has finally been lifted from me.

[wootwoot]

Originally Posted by Racecomp Engineering

What you need to have good ride quality:

1. Quality damping
2. Enough suspension travel

Spring stiffness plays a role, but it's not as big as most think. Choose spring rates based on how you use the car and what kind of tires you run.

I don't think the stock FRS or BRZ rides poorly...it's fine for a sporty car at it's price point. There is room for improvement for sure though.

Better shocks help...but the keyword is "better", not just "different." There's a lot of stuff out there that isn't better.

Lowering the car with just springs is tricky since you reduce compression travel. Using properly designed shortened bumpstops helps here but most importantly, you just can't go too low.

You can go lower with coilovers and keep adequate bump travel, but with coilovers often comes other compromises.

If stock BRZ is too rough for you, then you're gonna have a bad time with any lowering. Only thing I would recommend at that point is to try Bilstein B6 dampers.

- Andy

How do you match spring rates to tires? Is it just by feel and experiance? Or is there more involved? I have asked before but never found a clear answer.

[JB86'd]

[Racecomp Engineering]

Originally Posted by wootwoot

How do you match spring rates to tires? Is it just by feel and experiance? Or is there more involved? I have asked before but never found a clear answer.

The short version is to go by feel and experience. I know that 12 kg/mm springs on stock tires will suck and you'll very quickly overload the tires and lose grip. But it would make sense on r-compounds.

Generally you have a rough idea of the range of spring natural frequencies to shoot for in a car on X tires without downforce for the track (for example). There are all sorts of guidelines on the internet and I recommend taking them as just guidelines.

You can also (with some testing) investigate predicted lateral forces and desired roll angle, or run springs as soft as you can without hitting bumpstops, or run springs as soft as you can to keep suspension geometry "good", or some combination of all of the above.

You might also have a full run-down on tire data (tire spring rate, internal damping, etc.) but you'd probably be working in F1 or something.

- Andy

[KoolBRZ]

Originally Posted by mike the snake

I read somewhere that ride quality is something like 70-80% rear springs and 20-30% front springs.

If you think about it, it seems to be true. When I hit a pothole, I cringe when the rear wheels hit.

First off, I want apologize for making misleading statements that weren't factual. That was my opinion that the front springs were stiffer than the rear springs. The facts are as follows;
HKS Hypermax GT IV are;
Front-59 N/mm
Rear-38 N/mm

Stock springs are;
Front
BRZ 27 N/mm, FR-S 23 N/mm
Rear
BRZ 34 N/mm, FR-S 37 N/mm

BRZ front springs are roughly 79% as stiff as the rears, while FRS front springs are roughly 62% as stiff as the rears. I think the ratio is as important as the stiffness is. Using FRS front springs and BRZ rear springs would give me a ratio of roughly 68% front to rear, so I might find that to be a more comfortable setup. In the meantime I will continue to use the scientific method of trial and error to find the best combination for the best ride.

[Captain Snooze]

Originally Posted by KoolBRZ

The facts are as follows;

You have ignored motion ratio.

With the number you have given it works out to be approximately
Hypermax 48 N/mm / 24 N/mm
FR-S 21 N/mm / 24 N/mm
BRZ 24 N/mm / 22 N/mm

The BRZ is softer in the rear but the FR-S is stiffer in the rear. (Which lends itself to the FR-S being less understeery than the BRZ.)

[KoolBRZ]

What are those ratios exactly? I'd like to figure this out scientifically. Nevermind, I found out it's 1/1 front and 1/.75 rear.

[Captain Snooze]

Originally Posted by KoolBRZ

Nevermind, I found out it's approximately 1/1 front and 1/.75 rear.

I have seen numbers for the front ranging from 0.9 to 0.95 and 0.75 to 0.82 for the rear. The ratios change with suspension movement but is usually not considered.

[KoolBRZ]

Originally Posted by KoolBRZ

What are those ratios exactly? I'd like to figure this out scientifically. Nevermind, I found out it's 1/1 front and 1/.75 rear.

HKS Hypermax GT IV are;
Front-59 N/mm
Rear-28.5 N/mm

KW V3 are;
Front-60 N/mm
Rear-52.5 N/mm

Stock springs are;
Front
BRZ 27 N/mm, FR-S 23 N/mm
Rear
BRZ 25.5 N/mm, FR-S 27.75 N/mm

So the BRZ ratio front to rear is 1.06/1, the FR-S ratio is .83/1, the HKS ratio is 2.07/1, and the KW V3 ratio is 1.14/1. Mix and match gives us FR-S front with BRZ rear, .90/1, and BRZ front with FR-S rear, .97/1. So, with just stock parts I can try out ratios of .83/1, .90/1, .97/1, and 1.06/1. If I can mix and match KW and HKS, I can get F/R ratios of .63/1, 1.14/1, and 2.46/1.

[Ultramaroon]

[Digitalanalog]

Why would you mix shocks from different companies. The valving wouldn't be correct and you'd really get a fucked up ride. Quit focusing on the springs as the issue, as others have said is more on the shocks. Did you bother adjusting any on the dampening settings on any of the systems?