A discussion on improving ride quality

[Captain Snooze]

Originally Posted by jsimon7777

I just wanted to remind everyone that there is an ignore feature on this website. You can ignore users who you might feel add nothing to the discussion.

Thanks for the heads up. I have just tidied up this thread.

[wparsons]

Originally Posted by jsimon7777

I just wanted to remind everyone that there is an ignore feature on this website. You can ignore users who you might feel add nothing to the discussion.

My worry is that newer users will read his posts and think his advice is sound because they don't know any better.

[EAGLE5]

Originally Posted by wparsons

My worry is that newer users will read his posts and think his advice is sound because they don't know any better.

Taking one for the team.

[RYU]

This poor thread. It started out with good intentions! I promise...

[stonenewt]

Originally Posted by wparsons

Typically fast = soft damping, not the other way around. The softer the valving, the faster the damper will move for a given force.

When I say the damping is too stiff it means that the shock is responding too slow for the given spring rate.

Damping that is too fast would be underdamped, damping that is too slow would be overdamped.

Intrestingly I found this in a magazine article today

Be careful when someone uses the terms dampers and shock absorbers interchangeably. The two terms use opposing definitions for fast and slow. It is also reasonable to talk about stiff and soft when using the term shock absorber.

[Trettiosjuan]

Is there a coilover available that has a lot of stroke and enough adjustability to work with a relative low springrate (<5kg) at stock height? With a good shock so that it behaves well over small bumps, but can take big bumps massively better?

Could the Öhlins work for that? Or cheaper, RCE tarmac Zero? Any suggestions welcome.

[EAGLE5]

16" wheels and softer tires will do the trick.

[Trettiosjuan]

It goes a long way. But if one already has that and wants even more improvement? Aiming high..

[wparsons]

I found the solution to all of @Ubersuber 's complaints about this car.



They ride softer, understeer way more, make more power/torque across the board, etc. They address every single complaint he's had with these cars. You can even get them without an LSD.

Funnily enough, all those differences are exactly why the FRS/BRZ is chosen as a much better drivers car in every review that compares them.

[Trettiosjuan]

I still have some thoughts and wanting feedback on this subject.

So mine is the GT86 version with a front spring rate of only 2,3kg/mm. It's a DD, sometimes driven hard on small bumpy twisty roads.

To improve comfort I have very light 16" wheels with a very compliant tire. They help quite some in harshness and the small road irregularities.
But at say 5-10Hz, the ride is still bad, esp at the front. It's overdamped and just follows the irregularities on the road. Slightly ironical, I think the light wheels made that part worse as the dampers see lower wheel forces and become relatively more firm.
The high damping helps the handling in transition, but in the end the springs are still soft and they bottom out fairly easily, especially on multiple bumps taken quickly on that spirited back road drive.

After reading this forum extensively I realised that rebound damping in the front is stronger than rear despite the much softer front springs. And that contrary to many underdamped cars, a harder spring here could actually work out more comfortable (I tend to very sceptical to such claims but here it could actually be so).

Anyhow, things start to make sense but unfortunately most springs lower the car which I usually don't like - I want bump travel! But I like one of those, the rce yellows. These make sense in light of the damper dynos. And have a chance in improving the above discomfort phenomenon significantly. And also improving handling (I will not elaborate on my understanding of it here as you probably know already). Also the rates and shorter bumps stops suggest they should bottom out later despite the lowering (in commited driving, comfort is less important )

Actually, I think that the 4,5 kg front rate would be a tad too aggressive for the dampers on European roads and tastes, but I'm imagining that the light wheels here certainly make their job easier.

In short, wouldn't have thought I'd ever say so, but now I think that lowering springs really could improve DD comfort and back road handling. That said, anybody have suggestions for spring/perch spacers?

Any holes in my reasoning?

[Racecomp Engineering]

Much of your reasoning follows why we went with the specs that we did with our RCE Yellows. Mild drop, shorter bumpstops, firmer rates. We wanted to make the most of the limited bump travel available and we wanted to match the shocks better. I suppose you've seen the shock dyno plots we've posted.

That said, the rates are firmer than stock so although for some it is "better than stock", if you're a real stickler for ride quality it may just be "different than stock." Bilsteins help.

- Andy

[Trettiosjuan]

Originally Posted by Racecomp Engineering

That said, the rates are firmer than stock so although for some it is "better than stock", if you're a real stickler for ride quality it may just be "different than stock." Bilsteins help.

- Andy

Thanks. Yes, in the end I'm not looking for limousine comfort , but right now I feel that the relative compromise in suspension (dis)comfort at full ride height does not deliver as much as expected dynamically. I.e. feels firm but is ultimately soft dynamically. So perhaps not sooo much of a pure ride improvement, then I would need looser dampers but that would damage body control when pushed. Then I'd rather have "different" firm and actually being firm dynamically ...

Bilsteins are my next step if I feel the stock dampers can't handle the higher rate. But good hopes for my setup, I read in a comparison thread that yellows on stock dampers were more comfortable than the Bilsteins+yellow below 35mph, but at higher speeds the Bilsteins were more composed. It is here I have good hope that my 27lbs wheels will make the difference, as it is at high speeds light wheels with lower wheel forces becomes most noticable and the stock dampers will be better equipped to keep the lighter wheels from jarring over sharper bumps (it's at highway speeds the overdamping became more noticeable with the lighter wheels).


In the end, I've got to trust my BD and just try it, makes sense from observation and my "literature study and peer review" here

[Ubersuber]

With stock BRZ springs I found the Bilstein B6 to work perfectly.

You might consider swapping out your GT86 springs for a set of BRZ springs.

I also shortened the rear bump stops but that of course changes the rear roll stiffness, quite dramatically until the bump stops engage.

I decided that the real problem with this car from ride perspective is the pitch control is poor. This is common when anyone tries to increase roll resistance by fitting stiffer springs without carefully considering the effect on the pitch moment. The stiff and long rear bump stops accentuate this pitch problem in my opinion.

Fitting shorter rear bump stops would likely solve your ride issues but you would then have to be satisfied with more understeer and less roll resistance in the rear. Traction is improved but understeer is increased. For me the improvement in ride was more than adequate compensation for the slight difference in chassis balance. Just swapping to BRZ springs will have a similar effect for a GT86 owner. In fact just fitting rear springs from a BRZ might do the trick if the rest of the GT86 chassis suits you.Fit Bilsteins as well, I can't recommend them highly enough for the stock BRZ springs.

[Trettiosjuan]

B6 is next stop if this doesn't work out. How high are the front (hidden) bumpstops, same as OE?

Originally Posted by Ubersuber

...in my opinion.

Great progress