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

[8686]

@Racecomp Engineering @CSG Mike

I have SWIFT brz spec springs and I blow my shocks. The road condition in area is very bad. Now I need new shocks. I am thinking of Bilstein B6 but they are double the price of koni yellows. Appreciate your kind advice on what to chose.

[solidONE]

Originally Posted by ultra

Just want:
- More grip (higher cornering speeds)
- Lower lap times
- Less steady state understeer at the limit (more front grip)
- Less lift off oversteer (no trouble catching & balancing it but it slows me down a bit)

aaand local time attack doesn't allow aero mods in the class I'm targeting (go figure) so not going there.

I'm going to try out the more aggressive alignment and some tire pressure tweaks next time out. Will see how that it works. Then worry about tires ($$) then different suspension ($$$). No big rush, just trying to think ahead a bit.

But yes, you are most probably right. Those last few tenths are always the most expensive; it may or may not be worth chasing after them.

I think tires will help most if not all of those.

[u/Josh]

Originally Posted by CSG Mike

Last resort, if you want to experiment, try bumping the compression by 1 in the rear. It's a temporary band-aid fix to the lack of steady state rotation, not a real fix.

It is my understanding that damper settings have no effect on steady state performance because the damper only provides force when the wheel is moving in bump or compression and not once it has settled into its steady state position. Is practice different than theory in this case?

[CSG Mike]

Originally Posted by u/Josh

It is my understanding that damper settings have no effect on steady state performance because the damper only provides force when the wheel is moving in bump or compression and not once it has settled into its steady state position. Is practice different than theory in this case?

Only if the track surface is not perfect, which it probably is not. YMMV.

It's a hack to use loss of traction in the rear from hopping to get additional rotation, but its tiny momentary losses of traction.

It's not a real fix at all, and the car will ride like crap, and may suffer in performance elsewhere on the track.

[CSG Mike]

Originally Posted by 8686

@Racecomp Engineering @CSG Mike

I have SWIFT brz spec springs and I blow my shocks. The road condition in area is very bad. Now I need new shocks. I am thinking of Bilstein B6 but they are double the price of koni yellows. Appreciate your kind advice on what to chose.

Rates? Application? What are you doing with your car?

[8686]

Originally Posted by CSG Mike

Rates? Application? What are you doing with your car?

Swift spring brz rate 3.8k/4.5k rates with an inch drop

The car is my weekend fun drive and I am would like to balance comfort and stability. Reliability is important for me as I we have bad roads in my area. I dont want to change a shock apsorber every now and then. the original shocks survived for 5000 miles only with the springs.

[solma]

@Racecomp Engineering @CSG Mike

Question about rear suspension geometry, last summer after adding KW V3, rear upper arm whiteline camber kit(bushing) and running staggered setup 235/255 I have found that I am not able to rotate de rear when turning, instead I get understeer all the time(I am a smooth driver that do not like upsetting the car entering a curve).

So I decide to map out the dynamic toe in the rear suspension as I think it is where the solution is, my finding seem to go along with what I am feeling on the track.

I find that toe, at oem height, is toe-ing out on compression and toe-ing in in decompression.(logical by the fact that rear suspension can take more load during a turn) up to a certain point, close to max compression, the toe start to come in(must be for stability/security)

But there was a twist in the geometry and upper arm bushing(one is more compliant compare to the other). When torque is applied to the wheel, the hub start turning clockwise(due to weaker bushing), by doing so the toe is toe-ing out(without mesuring it, it seem quite a lot, possibly 2-3deg). This happen only when suspension is compress and torque is apply.

So here my question, because of the lowering(I am at maximum height for daily driving, so i just lower the car 3/4inch), but spring are stiffer then oem(less compression in cornering)=less toe out , plus because I have replace the upper arm bushing with poly it meen I have lost the toe-ing out feature on power, and last because I have larger tire in the rear(so need to transfert more working load at the rear), the solution I have found is to modify the pivot point(on the subframe) of the toe link, I did try it, its working, I can play with the decompression and compression toe-ing, so do you think its a good idea?

The max toe out I can get, under full compression is around 2 deg out with 1 deg in in full decompression. The oem value are around 0.6deg out (compress) and 0.5 deg in(decompress)

[u/Josh]

Originally Posted by CSG Mike

Only if the track surface is not perfect, which it probably is not. YMMV.

It's a hack to use loss of traction in the rear from hopping to get additional rotation, but its tiny momentary losses of traction.

It's not a real fix at all, and the car will ride like crap, and may suffer in performance elsewhere on the track.

And that is where theory differs from reality. Thanks.

Is this also a situation where the driver feels like the car is handling better but his lap times (or cornering speed in that particular corner) aren't improving? The way I see it is if you are front grip limited to begin with, more compression damping in the rear isn't going to get you more front grip in "steady state" cornering, just less rear grip. Thus the car feels like it's rotating better but you're still limited by the same amount of front grip you always had.

[CSG Mike]

Originally Posted by 8686

Swift spring brz rate 3.8k/4.5k rates with an inch drop

The car is my weekend fun drive and I am would like to balance comfort and stability. Reliability is important for me as I we have bad roads in my area. I dont want to change a shock apsorber every now and then. the original shocks survived for 5000 miles only with the springs.

How were your old dampers damaged? Excessive bottoming out?

[CSG Mike]

Originally Posted by u/Josh

And that is where theory differs from reality. Thanks.

Is this also a situation where the driver feels like the car is handling better but his lap times (or cornering speed in that particular corner) aren't improving? The way I see it is if you are front grip limited to begin with, more compression damping in the rear isn't going to get you more front grip in "steady state" cornering, just less rear grip. Thus the car feels like it's rotating better but you're still limited by the same amount of front grip you always had.

Precisely. We're lowering rear grip, rather than changing the balance or adding front/overall grip.

It *may* be faster, if it allows the car to sustain a more optimum slip angle and/or be throttle steered as a result.

[CSG Mike]

Originally Posted by solma

@Racecomp Engineering @CSG Mike

Question about rear suspension geometry, last summer after adding KW V3, rear upper arm whiteline camber kit(bushing) and running staggered setup 235/255 I have found that I am not able to rotate de rear when turning, instead I get understeer all the time(I am a smooth driver that do not like upsetting the car entering a curve).

So I decide to map out the dynamic toe in the rear suspension as I think it is where the solution is, my finding seem to go along with what I am feeling on the track.

I find that toe, at oem height, is toe-ing out on compression and toe-ing in in decompression.(logical by the fact that rear suspension can take more load during a turn) up to a certain point, close to max compression, the toe start to come in(must be for stability/security)

But there was a twist in the geometry and upper arm bushing(one is more compliant compare to the other). When torque is applied to the wheel, the hub start turning clockwise(due to weaker bushing), by doing so the toe is toe-ing out(without mesuring it, it seem quite a lot, possibly 2-3deg). This happen only when suspension is compress and torque is apply.

So here my question, because of the lowering(I am at maximum height for daily driving, so i just lower the car 3/4inch), but spring are stiffer then oem(less compression in cornering)=less toe out , plus because I have replace the upper arm bushing with poly it meen I have lost the toe-ing out feature on power, and last because I have larger tire in the rear(so need to transfert more working load at the rear), the solution I have found is to modify the pivot point(on the subframe) of the toe link, I did try it, its working, I can play with the decompression and compression toe-ing, so do you think its a good idea?

The max toe out I can get, under full compression is around 2 deg out with 1 deg in in full decompression. The oem value are around 0.6deg out (compress) and 0.5 deg in(decompress)

If it works for you, it's always a good idea.

Have you considered using square tires or changing your spring rates to try to balance the car instead?

[8686]

Originally Posted by CSG Mike

How were your old dampers damaged? Excessive bottoming out?

I think so. We have some bad bumby roads here.


Sent from my iPhone using Tapatalk

[CSG Mike]

Originally Posted by 8686

I think so. We have some bad bumby roads here.


Sent from my iPhone using Tapatalk

The real solution is to raise your car.

I've seen good results with the Bilsteins as well.

[Racecomp Engineering]

Originally Posted by ultra

@Racecomp Engineering

What spring rates do you recommend as a default for the Tarmac 2s versus the KW Clubsports, and what increase in spring rates (if any) would you recommmend for the Tarmac 2s based on, say;

a) Mixed street & casual track, extreme performance summer street tires
b) Mixed street & serious/competitive track, club level, extreme performance street tires
c) Mixed street & serious competitive track, club level, R comps/semislicks
d) Serious competitive track work, club level, R comps/semickicks
e) Serious competitive track work, club level, full slicks (aka Hoosier A6 or stickier)

Let's assume aggressive-as-you-like alignment. Ballpark rates would be OK, not trying to steal your setup tricks. Just curious where the 'sweet spot' is on the RCET2s before you'd have to look at custom valving or a higher end shock, as well as what to consider when choosing spring rates.

Our default rates for the Tarmac 2s are 7kg/mm front and rear. Yes, even rates. The front of this car really likes spring rate as it keeps geometry in check. If you're limiting your front camber due to driving the car on the street IMO it especially makes sense.

Anyway, that default set-up works well for a, b, and even a little bit of c. Most of the time with c, d, and e, we'd be going custom....9k/9k is common, 9k/10k, 10k/10k, and firmer.

For e you'd certainly still be happy with T2s...they can easily handle the spring rate but it might be a good time to think about JRZ and that level.

There is always room for driver preference and suiting the rest of a set-up. The default is just a starting point that works for most, but we do our best to tailor each set-up to the individual (we assemble everything here for each person anyway, so it's just parts).

I hope that's a good enough answer. There are so many variables and if/thens for each case that this could become a book!

- Andy