A discussion on improving ride quality

[Reaper]

Originally Posted by cdrazic93

If you can achieve that with a FWD car, hats off to you sir!

Drive in reverse

[cdrazic93]

Originally Posted by Reaper

Drive in reverse

My favorite FWD car is a supra in reverse...

[Fizz]

You should also try to reduce un-sprung weight as much as possible as this can have a huge impact on ride comfort. Go for the lightest 17" wheel you can find, and match that up with a slightly "meatier" than stock tire size (for added sidewall). Add in lightweight calipers and 2-piece rotors too.

[Vracer111]

Another vote for reducing the unsprung mass... the stock setup is just too heavy for 17" wheels IMO. I'm also someone who cannot stand very stiff-walled tires... hence my dislike for Falken Azenis which I feel are horrible tires. Kumho and Hankook are where it's at for me. Tires are an integral part of the vehicle suspension and they need a proper elasticity to maximize grip while not being too soft to badly effect responsiveness. Some noticeable elasticity is very good, you are able to ride that traction area all day long rather than having such a narrow band to fall off either side of with very stiff-walled tires.

I'm still on the stock suspension and the ride quality is much better than factory due to 3 factors: 1 - reduction in unsprung mass, 2 -tire size and brand choice, and 3 - front Grimmspeed strut bar. Unsprung mass has already briefly been mentioned, but the less mass you have fighting and impacting against the springs and dampers the more efficiently the suspension is able to do its job. I'm currently almost 5lbs a corner less in mass than stock. 5lbs is very noticeable improvement in ride quality with this car.

With my tire choice, I decided to experiment with upgrading the handling by decreasing the tire size and running a Max Performance category tire for optimum wet/dray handling balance...I've recently installed 205/45-17 Kumho Sport LEs on 17x7.5 +40mm offset Enkei Fujins that even further improved the ride quality over the stock tires mounted on the same wheels (which improved the ride quality over the stock tires on the stock wheels.) The car has never handled better, while it doesn't have the ultimate grip or unsprung weight (~1lb less) of my track tire set, the dry grip is still way beyond that of the stock Primacy HP's, the balance of the car is just incredibly agile like it's never been before, and the grip in the wet is beyond phenomenal, insane is a more apt word. There is also better acceleration and responsiveness due to the smaller diameter. Running 205/45-17 sized Max Performance compound tires melds perfectly with the chassis in a way nothing else I've experienced has - I seriously giggled like a schoolgirl and laughed hysterically for the first time driving this car that I've owned for 2 years - it seriously should have been the stock setup (and did I mentions tires are really inexpensive in the size as well?) I encourage everyone to try a great 205/45-17 Max performance tire on a lightweight (17lbs or less...) 17x7.5 wheel set with a 40-45mm offset... you will experience something rather amazing that no amount of huge meaty tire with grip on wide wheels can ever give you.

And finally the Grimmspeed front strut bar solidified the front and reduced the harshness felt by large bumps and rough pavement. Everyone who has installed one has said the same thing as well...if someone didn't notice a difference, then they probably are the type of individual that doesn't notice the felt difference a 2-3 lb reduction in unsprung mass per corner makes in ride quality, and yes it's quite a noticeable difference...

[BrandonB]

Originally Posted by RYU

I should have clarified further. The front damping has been fine. It's the rear I feel has a very short stroke and can be improved.

I've looked into the higher top mounts by increasing the height of the tophats. The problem with this setup is you're not really increasing overall stroke. You're simply repositioning the damper piston in a more optimal spot as to not bottom it out within the damper. You spring height and motion ratio stays the same. While this will help a little bit i'm not sure yet it will solve the problem.

I've tried the following
* Stock BRZ
* Stock with RCE Yellows
* Eibach Multi-Pro R1
* RS*R Sports-i
* KW V3
* Bilstein B14

I've also driven a car with Tein SRCs. Although better it still felt like a lack of travel when hitting the big bumps. I've also considered Ohlins R&T but they appear to be firm as well.

Basically, I don't think this is a damping problem. It's a short stroke/damper travel issue.

I have not read if people have experienced good results from these various offset LCAs and was hoping to hear from the community before proving my theory.

I'm an old guy relatively. I've owned (and tracked) several vehicles including an S2000 AP1, AP2, 911 930 Turbo, E36 M3, GSXR750, CBR600, NSX and even a Pantera and 66 Chevelle. I'm familiar with basic suspension tuning (but not an expert).

What else have you guys done?

BTW... this car is ok on normal roads. But my commute in downtown LA requires 16 miles of driving on Olympic or Pico blvd. For those who know these roads...I know you feel sorry for me now. The thing is.. my NSX, E36 M3, and S2000 take these roads perfectly fine. The BRZ suspension must just suck in these situations.

which coilover would you say rode the best?

[Trettiosjuan]

Also have the grimmspeed strut bar. It literally felt like I had underinflated my front tyres by 10psi, it's that more comfortable on sharp/rough imperfections.
Basically, my car now rides and handles like a Lotus

[gramicci101]

Originally Posted by Trettiosjuan

Basically, my car now rides and handles like a Lotus

The last time I drove a Lotus (Exige) it rode like it didn't have suspension at all. I think one of my fillings fell out.

Handled great, though.

[Trettiosjuan]

Originally Posted by gramicci101

The last time I drove a Lotus (Exige) it rode like it didn't have suspension at all. I think one of my fillings fell out.

Handled great, though.

Not all Lotus are alike... the base models are known for their good ride, dunno what Exige you tried...

I just like it when a car both rides well and handles well at the same time. The stock car didn't really do that first part and I think mine improved a lot while handling also improved significantly. At least in part because it rides better... just by following an old, well known recipe...

[cdrazic93]

Wait...just a thought, what about airbag suspension?

[Ubersuber]

I cut one half inch out of the hard top section of the rear bump stops and glued the two remaining bits together and installed Bilstein HD rear shocks (B6 standard length). My mechanic installed Subaru supplied camber bolts for the lower arms and set the rear camber within spec at 1.9 degrees negative. Toe was tweaked at both ends. The ride improvement was marked and the tendency for the rear axle to step out suddenly in the wet was reduced.

I fit 225/45x17 Michelin Pilot A/S 3 tires which are exceptionally good for an all season compound. Tread design is as for the Pilot Sport 2, essentially just a four rib design with that narrow outer groove. I fit OZ Alleggerita wheels in 17 x 7.5, graphite silver (dark grey) which are certified to be under 16 lbs per wheel. The new wheel is lighter but the tire is heavier resulting in a saving per corner of only a couple of pounds of unsprung weight. Fuel economy is worse (the Primacy is a LRR tire but also 225 section means the odometer is reading a tad lower than stock which will throw off the fuel economy as measured but not in reality).

I liked the Bilsteins so much on the rear axle I fit the front struts recently.

I note that Subaru is rumoured to have changed shock supplier maybe to Sachs for 2015 and that suspension "improvements" have been made. I'm thinking that Subaru has recognized the deficiency in the original shock specification.

Finally, I am convinced that the tendency of this car to step out at the rear axle in the wet or snow or ice results from too early a contact with the rear bump stops, which combined with what seems like a tight bias ratio of the Torsen (anyone know what that ratio is?) tends to break the inside rear tire loose a little too suddenly for my taste (traction control off obviously). Elsewhere on this forum it has been reported that the free stroke on the rear shocks is only one half inch stock. If so then on mine it is now one inch. The ride is much better but more importantly the rear axle behaves itself much better.

The balance of the car under steady power application is essentially unchanged as the Torsen is quite tight. What has changed is the effective spring rate rise when the outside suspension compresses far enough to touch the bump stop. Unlike an anti roll bar the bump stop suddenly increases the spring rate when the shock/spring begins to "bottom out" on the bump stop. I decided to shorten the bump stop by cutting out part of the hardest end (the top) which also then reduces the effective spring rate of the bump stop as well as increasing the free travel of the shock/spring before contacting the bump stop. This seems to work very well for the street but for a time attack or tight cornered track I would refrain from cutting the bump stop OR I would cut the bump stop and fit slightly larger roll bars front and rear as for the new TRD kit, for example. Roll bars increase roll stiffness but do not stiffen the ride by as much as a spring rate or bump stop rate. Cutting the bump stop has a similar effect to reducing the rear roll bar rate or increasing the front roll bar rate.

The Torsen diff does tend to induce a little twitchy handling because of the way it works. Because it transfers torque from the faster moving wheel to the slower moving wheel it tends to push from the inside rear when torque is applied. This is known to induce oversteer forces (the opposite effect is obtained by braking the inside rear wheel as stability software is designed to do). Under some conditions this torque transfer can oscillate back and forth across the Torsen depending upon just how much grip each tire has at any given moment. Obviously, transferring torque from the outside wheel which is loaded and has plenty of grip to the unloaded inside wheel which will have less grip can induce inside wheel spin which then drives the torque back to the outside wheel, stopping the inside spin and so on. If you have been in a Mustang GT which is also fitted with a Torsen this effect is obvious because the rear tires are easily overcome. In our puny little BRZ this effect tends to show up in the wet or on snow or ice although somewhere on this forum somebody tracked a car with wheel speed sensor tracing and recorded this effect on a wheel by wheel graph, very interesting.

[Captain Snooze]

Originally Posted by Ubersuber

I'm thinking that Subaru has recognized the deficiency in the original shock specification.

Deficiency? From what I have read the stock dampers are very good for a car at this price point.

[protpibe]

I'm currently running:

17x9 Rays with 245/40 Continental ECDW Tires
HKS Hipermax IV GT Coilovers (set to 15 out of 30 firmness)
Hotchkis Sway Bars
Buddy Club Rear LCAs
Buddy Club Front Control arms and Ball Joints

The car drives very close to a stock vehicle, if not better. It rides extremely well on the highway, but in the city it's probably very close to the OEM setup (somewhat choppy, doesnt' like sharp bumps). The front and rear control arms were probably the most noticeable difference in making the car more "compliant" and "normal" feeling. The added stroke in the rear and roll center correction in the front were probably a large contributor to that.

[shattered_memory]

Out of the following suspension setups that you had, which one would you say felt closer to stock level of comfort?

* Eibach Multi-Pro R1
* RS*R Sports-i
* KW V3
* Bilstein B14

[Ubersuber]

Originally Posted by Captain Snooze

Deficiency? From what I have read the stock dampers are very good for a car at this price point.

Perhaps at a "price point' but they are still deficient as compared to what should have been fitted. For Subaru we're talking an incremental additional cost of under $500.00.

The stock shocks are definitely the weak point of an otherwise excellent stock suspension. The spring and roll bar rates seem exactly right. I understand a stock BRZ will pull over 0.9 g lateral on stock tires and nearly 1.0 if you fit sticky rubber. However, during bumpy bends this excellent suspension is let down by weak rear damping and relatively crude front strut damping.

I think Subaru have recognized this failing with the 2015 model year and improved this aspect of the suspension, but I have not driven one yet.

My view is that the rear shocks are not stiff enough in rebound to properly control the spring. Hitting the rear bump stops too early in the shock stroke just exacerbates this weak damping problem. The symptom is an annoying pitch which fitting the four Bilsteins eliminates completely.

I am now of the view that the stock front shocks are too stiff in jounce which contributed to the pitching. Once I fitted the Bilstein struts the pitching has been eliminated.

One unlooked for bonus is the Bilsteins are an inverted design (as for the Subaru WRX STI) and the much larger strut "rod" (it is the hollow cylnder holding the shock fluid) stiffens up the front strut laterally which further benefits the already excellent steering.

I am so impressed with the difference I recommend you try upgrading to Bilstein B6 (or HD in North America, same shock) even before you fit better tires. The difference is remarkable.

In fact, the new shocks and tires I fitted are so solid I can now feel the inadequacy of the stock rubber bushings...