CSG and RCE tag-team suspension Q&A thread! Ask us anything!

[Racecomp Engineering]

Originally Posted by Cephas

Hey I got a question for @Racecomp_Engineering. I have the RCE Yellows/B6 kit, and like it quite a lot. A couple weeks ago, I randomly had a couple hundred pounds of stuff in the trunk, and was surprised at how much more settled and smooth the car felt.

That got me thinking. In a car with a pretty significant front weight bias, why the square spring setup? The rear of this car has always been a little nervous/flighty (especially over our junk pavement around here). Seems like it'd make sense to make the rear more compliant, but I'm not a suspension engineer.

The motion ratio influences spring rate choice as BlueWhelan said and controls how stiff your springs are "at the wheels" (or wheel rate). There's more to choosing spring rates and you have to balance grip, compliance, response, body roll, etc.

More here on motion ratios:
https://www.instagram.com/p/B3cDzqOD..._web_copy_link

Adding a bunch of weight to the rear lowers the rear natural frequency, which makes your rear suspension feel softer.

More here on suspension frequencies:
https://www.instagram.com/p/B6TKG6Un..._web_copy_link

- Andrew

[Racecomp Engineering]

Originally Posted by nova.86

I got Tein Mono Sports coilovers, once I find a good shop that can install them and do corner balancing followed by an alignment, is there a specific set-up I should ask for ? I am looking for a street focused set-up with spirited driving and minimal track sessions a year. I've heard I should have more of a drop in the front, and as well as from others to have more of a drop in the rear, and some that say equal drop on front and rear. I'm a noob in customizable coils and am just wondering what's a good set-up to ask for for what I'm looking for. Thanks in advanced.

If you're talking to a good suspension shop that knows these cars, they'll want to know what kind of tires you use, what type of driving you do, any other suspension mods, and so on. A really good shop will properly set bump vs droop travel on your coilovers since they have separate ride height and preload adjustability.

In terms of drop, a 1 inch drop front and rear is a safe place to start. I personally would destroy my bumper with a -1.5 inch drop but that isn't necessarily better from a handling standpoint anyway.

For damper settings, start soft and work your way up. Impossible to say from here which damper clicks will be best for you but in general most people are too stiff. Some compliance is good even on track. Learn what the clicks do and don't change (for example, stiffer damper settings do NOT mean less mid-corner body roll).

An completely optimized alignment depends on your tire choice and ideally for a track car is dialed in with testing and tire temp probes. Probably not what you need, so ball park for a fun backroads street car is 0 toe all around (or a tiny bit of rear toe in), -2.0 degrees camber front and -1.75 degrees camber rear. Don't worry about anything else.

The Tein manual might give a good starting point for damper settings. Like timurrrrrr said, revisit everything in a few months and evaluate how it feels. Take notes too.

- Andrew

[Stonehorsw]

What the main differences are related to coilover design between gen1 and 2? Should we expect a significant departure on spring rates?
Scenarios:
1. Daily driver - GT type setup
2. Track car - original aero in both vehicles

[RedReplicant]

Picked up a car yesterday, car pulls right traveling down a normal road. On the brakes and the car seems to straighten out, on medium-heavy throttle the car pulls left (supercharged) and then goes back right when letting off throttle.

Toe plates show basically 0 toe front and rear and neither side looks odd. Swapped the rear tires side to side and it acts the same as before. What should I check first? Car has SPL arms everywhere in the rear other than UCA, OS Giken diff, Salasko subframe / diff mounts.

[marco_mc22]

Originally Posted by RedReplicant

Picked up a car yesterday, car pulls right traveling down a normal road. On the brakes and the car seems to straighten out, on medium-heavy throttle the car pulls left (supercharged) and then goes back right when letting off throttle.

Toe plates show basically 0 toe front and rear and neither side looks odd. Swapped the rear tires side to side and it acts the same as before. What should I check first? Car has SPL arms everywhere in the rear other than UCA, OS Giken diff, Salasko subframe / diff mounts.

You may have something loose if it changes drastically behaviour from under to off throttle and braking, have you checked your front LCA and steering arms?
I’m not a fan of toe plates tho, it may be worth to double check everything using side by side string alignment or a good laser bench imo.

[RedReplicant]

Originally Posted by marco_mc22

You may have something loose if it changes drastically behaviour from under to off throttle and braking, have you checked your front LCA and steering arms?
I’m not a fan of toe plates tho, it may be worth to double check everything using side by side string alignment or a good laser bench imo.

Nothing looked loose in the rear, but I'll get under it and start prying on stuff today, including up front.

I'm also not a fan of toe plates for this kinda thing, it was mostly a sanity check. I'll take it to my alignment guy this week and see what he says.

[Racecomp Engineering]

Originally Posted by Stonehorsw

What the main differences are related to coilover design between gen1 and 2? Should we expect a significant departure on spring rates?
Scenarios:
1. Daily driver - GT type setup
2. Track car - original aero in both vehicles

We're STILL waiting on our preordered test car.

But we have a few things in process already.

I don't expect a significant change in spring rates for either scenario as overall design/dimensions of the car have not changed much. A lot of the change in handling feel is likely from the increased rigidity of the car and the change in valving on the factory shocks. I think the new platform will make better use of more spring rate, and the front aluminum uprights on the BRZ will make better use of available compression damping. But probably not enough to say...go up the next 50 lbs/in in spring rate.

We'll have a lot more to say soon.

- Andrew

[Racecomp Engineering]

Originally Posted by RedReplicant

Picked up a car yesterday, car pulls right traveling down a normal road. On the brakes and the car seems to straighten out, on medium-heavy throttle the car pulls left (supercharged) and then goes back right when letting off throttle.

Toe plates show basically 0 toe front and rear and neither side looks odd. Swapped the rear tires side to side and it acts the same as before. What should I check first? Car has SPL arms everywhere in the rear other than UCA, OS Giken diff, Salasko subframe / diff mounts.

Originally Posted by marco_mc22

I’m not a fan of toe plates tho, it may be worth to double check everything using side by side string alignment or a good laser bench imo.

Second this, check with strings or a rack. Check thrust angle.

ALSO...check tread depth at all 4 corners. One time when putting my winter tires on, I got my tire rotation mixed up such that 1 rear went to the front and the other stayed in back. It did what you described, although super squirmy tread winters made it extra noticeable.

- Andrew

[RedReplicant]

Originally Posted by Racecomp Engineering

Second this, check with strings or a rack. Check thrust angle.

ALSO...check tread depth at all 4 corners. One time when putting my winter tires on, I got my tire rotation mixed up such that 1 rear went to the front and the other stayed in back. It did what you described, although super squirmy tread winters made it extra noticeable.

- Andrew

Thank you too, I'll see what the alignment shows this week.

I swapped the 17s with A052 from my other car onto this car to test (front brakes won't clear the 17s) and found that the rear pull was lessened a fair amount, so I am guessing it is the rear alignment coupled with the Nankang AR1s not being super friendly.

[ForeverCar]

I took delivery of a 2022 BRZ about a week ago and am considering suspension upgrade. I would like to get @Racecomp Engineering input on some options.

My use of the car is likely atypical (for more context, my intro thread https://www.ft86club.com/forums/showthread.php?t=147938).

Goals for the car,
1. The most connected driving experience
2. A learning platform for myself

To accomplish goal #1, would using spherical bearings and changing to solid/harder bushings where possible be the way to go? NVH isn't too much of a concern.

To accomplish goal #2, I'm consider finding a 4-way adjustable damper setup with relatively low spring rates. Mainly, I want to experiment with the different settings to learn how they impact the dynamics. If available, I probably would like to add sensors and data logging as well. When available, I plan on going with Motec (either a full M1 build or PnP). My testing grounds are backroads and road courses.

I'm definitely not chasing lap time. Driving feel and learning suspension adjustment are the primary goals.

[timurrrr]

Originally Posted by ForeverCar

To accomplish goal #2, I'm consider finding a 4-way adjustable damper setup with relatively low spring rates. Mainly, I want to experiment with the different settings to learn how they impact the dynamics. If available, I probably would like to add sensors and data logging as well. When available, I plan on going with Motec (either a full M1 build or PnP). My testing grounds are backroads and road courses.

Good goal!

Damper tuning is really fine tuning of the handling characteristics, and can be very hard to "feel" and understand in the beginning. Good data and consistent conditions are key to making progress effectively. That's really hard to achieve in the real world!
Have considered instead learning that first in a simulator? Easy to recreate literally identical conditions, as many times as you want, any time of any day. Much cheaper. Really high quality data for $0.

You may end up paying less for a decent sim rig and a set of good 1-way adjustable coilovers than for a 4-way set and all the data stuff.

[ForeverCar]

Originally Posted by timurrrr

Good goal!

Damper tuning is really fine tuning of the handling characteristics, and can be very hard to "feel" and understand in the beginning. Good data and consistent conditions are key to making progress effectively. That's really hard to achieve in the real world!
Have considered instead learning that first in a simulator? Easy to recreate literally identical conditions, as many times as you want, any time of any day. Much cheaper. Really high quality data for $0.

You may end up paying less for a decent sim rig and a set of good 1-way adjustable coilovers than for a 4-way set and all the data stuff.

Thanks @timurrrr! Great idea and I have considered it. It’s probably not the most cost effective path and likely tougher, I am drawn to dealing with the real world complexities as I think the learnings stick more as well as transfer better to applications in the future.

[grumpysnapper]

Originally Posted by ForeverCar

1. The most connected driving experience
To accomplish goal #1, would using spherical bearings and changing to solid/harder bushings where possible be the way to go? NVH isn't too much of a concern.

My 2cents (not that you even asked me, or that you should even care) is that this is a great way to potentially ruin a connected driving experience on real world roads.
Most of histories most renowned "drivers" cars have used a degree of compliance to achieve greatness.

[ForeverCar]

Originally Posted by grumpysnapper

My 2cents (not that you even asked me, or that you should even care) is that this is a great way to potentially ruin a connected driving experience on real world roads.
Most of histories most renowned "drivers" cars have used a degree of compliance to achieve greatness.

Appreciate your input. I expect significant increase in NVH. If tires, springs, anti-roll bars, and dampers remain mellow, I wonder how it would feel. Maybe there still won’t be sufficient compliance for road use?

When I had a 991.2 GT3RS, I didn’t think it’s very hard. Springs were a bit stiff and I think the tires (Cup 2) could use a softer sidewall for compliance. IIRC, the stock setup doesn’t use many “rubber” bushings.

It’s more a curious exercise to see what eliminating all the “soft” bushings while keeping compliance in the tires, springs, and dampers would do (and keep anti-roll bars stock or similar). Might be a bad idea. Since it’s not a daily driven car and one of the goals is feel, I wonder what it’d feel like.