Ohlins Road & Track for FRS/BRZ suspension install/review thread

[Racecomp Engineering]

Originally Posted by strat61caster

Like racecomp says, front and rear suspensions are entirely different, putting the same spring rates will create two vastly different feelings at each end of the car, if I may quote them, the rough math below illustrates it pretty well:



According to the thread below the difference is actually bigger than they estimate above: 0.92 motion ratio to a 0.59 rear and realistically calculating stiffness and frequencies involves many more variables. But a 4k on the rear actually feels like a 2.5 and a 1.9 vs the front sitting at 4k or 3k.

http://www.ft86club.com/forums/showthread.php?t=26661

imo swapping front and rear springs sounds like a good start and the adjustable valving should make accommodation easy, I've even heard non-adjustable dampers can easily take +/- 50 lb/in (0.9k) spring changes without adverse effects.

Right, but the motion ratio is not the only difference in the front and rear suspensions. Camber and toe change through the range of motion, available travel, etc. These are very important too and are a big part of the reason why I don't recommend going so soft up front on this chassis. 3k is very soft.

EDIT: also, the 0.59 motion ratio you cited was for the rear swaybar, not spring.

- Andrew

[strat61caster]

Originally Posted by Racecomp Engineering

Right, but the motion ratio is not the only difference in the front and rear suspensions. Camber and toe change through the range of motion, available travel, etc. These are very important too and are a big part of the reason why I don't recommend going so soft up front on this chassis. 3k is very soft.

EDIT: also, the 0.59 motion ratio you cited was for the rear swaybar, not spring.

- Andrew

Thanks and corrected, thought I made it obvious that there were many factors

[Tor]

Originally Posted by strat61caster

Like racecomp says, front and rear suspensions are entirely different, putting the same spring rates will create two vastly different feelings at each end of the car, if I may quote them, the rough math below illustrates it pretty well:

Hi strat61caster, I already read that thread and for my part am fully aware. The same math obviously applies to the stock suspension.

The OEM e.g FR-S is 2.3k front and 3.8k rear. So if you put a 10k in the front and divide it with 2.3, you get an increase of 434%. If you equally increase the rear with 434% it would give you a spring rate of 16.5 k.

10k/16.5k would probably be a very bad combo - so that's what meant with that they react differently to increasing rates. In the rear an increase in rate apparently has a bigger impact than on the front - due to the different constructions. Thereby is not automatically being said, that the same applies to a reduction from the OEM values. E.g. the GT86 (my car) is OEM only 3.3k in the rear, which percentually is a big difference to the FR-S. So maybe the rear suspension doesn't react that much to changes in the lower end of the scale but exponentially more to higher rates? Where as the front perhaps react to changes in a more linear fashion?

So the objective may not be to make a selection in spring rates that equals in same motion-compensated-rates front and rear. The goal for my part is to make the car handle as neutral as possible, within the limits of the parameters I can affect with my choice of suspension (coil overs / anti sway bars). From the the availability of kits out there and what experiences people report, it seems that as you increase the rates, the motion uncorrected rates should be about the same, preferably with a slight rear bias.

With the basis, in my case, being dampers matched for 6/5 rates. What can I change, in order of ease/costs:
1) Alignment
2) Anti sway bars settings
3) Spring rates - but limited within the ranging of the dampers.
4) Revalving

With my cheap choice of ST XTA coilovers the last option drops out. It wouldn't have been a cost efficient purchase, and from the start my plan was to see what could be obtained within the limits of 1 and 2. I am keeping option 3 open, but would only do mild changes (like changing the rear from 5 to 6, as I doubt the quality of the dampers would support making big changes. Personally, I think the same logic goes for the Öhlins MP20, it would have been more cost-effective to make a different decision from the beginning, rather than revalve and change springs - hence they got eliminated from my list of choices.

I would like to point out that I am a theorist. I spent a long time gathering as much information as I could on the subject and still have a lot to learn, which is a process I enjoy a lot.
I still probably overlook a lot of theory and most importantly; the practical experience is still completely missing. So the above may have a lot of errors, which I then hope some else will then correct me on here.

[ajc209]

Just too add. The GT86 here in the UK has ~2.3kg/mm front and ~3.7kg/mm rear spring rates. I know someone that tested them.


BRZ is 2.7kg/mm and 3.3kg/mm I believe.

[strat61caster]

Originally Posted by Tor

So the objective may not be to make a selection in spring rates that equals in same motion-compensated-rates front and rear. The goal for my part is to make the car handle as neutral as possible, within the limits of the parameters I can affect with my choice of suspension (coil overs / anti sway bars). From the the availability of kits out there and what experiences people report, it seems that as you increase the rates, the motion uncorrected rates should be about the same, preferably with a slight rear bias.

Gosh, so much I want to say but fear I may be out of my depth until I prove my theories which won't be for a few more months. Until then, start reading up on effective wheel rates, the stiffness of the suspension as a whole from tire contact patch to the chassis, it can be characterized and is usually expressed as a natural frequency of the system with cars in the 1.2Hz-1.8Hz range being suitable for street use and then climbing up to 2.0+Hz which usually reserved for competition vehicles. There's also theories there about appropriate spring selection from setting up F1 cars to Cadillacs.

[Tor]

Please do state your theories, im sure someone else here will add to/complete and correct where necessary.

The part of my post you quoted was very unscientific. I'm just saying that the most proven setups out there are e.g. 6/6 6/7 8/9 10/11: Which is what I meant when I wrote "it seems that as you increase the rates, the motion uncorrected rates should be about the same, preferably with a slight rear bias."

In that sense we can disregard the motion ratios, because we already know what works.

[Racecomp Engineering]

Y'all might want to jump over to the suspension tech thread or the ask RCE and CSG thread

- Andrew

[DocWalt]

After four months of street driving in all sorts of weather conditions and a couple of events on the Ohlins I figure I have enough time for some impressions. I'll post back with track impressions in May

My suspension setup:
-2.6 / -1.9 degrees of camber front/rear
0 / 1/8" toe in front/rear
60N/mm / 70N/mm spring rate front/rear
~1/4" rake, set to Ohlins recommended setup (though tweaked to compensate for the stiffer rear springs)
17x9 ET35 RPF1s wrapped in 245/40/17 RE-71Rs (I was using stock spec wheels with Continental Winter Contact snow tires for two months of testing)

Street use:
- Not as soft as I was hoping, though very acceptable considering the springs are twice as stiff as stock. Nobody that's ridden in the car has commented on a rough ride or anything.
- Very controlled damping, not at all "floaty" or pogo stick like. Hitting potholes (inevitable part of Pennsylvania winter driving) is pretty much a non-event.
- The top hats most certainly transmit more noise and road feel. Anyone that says otherwise is either numb to the world or has an exhaust that's loud as hell. Any large impact clearly transmits more noise through the car. Note I'm not talking about rattles because there simply aren't any.
- I was surprised by how affected the damping was with temperature swings. Below ~45 degrees F I chose to open up the damping a bit as it was noticeably stiffer. I think the temperature compensating needle valve is intended for raising temps on track, not 2 degrees F shock oil
- Not a single new rattle or squeak. I'm impressed and very happy with that.
- I drove on plenty of salty roads, no corrosion or other issues. Just hosed the dampers off (with low pressure, no spray) and the salt just washed off. Fantastic!
- Noticeably more playful feeling, the car does more of what I want without any vague wishy-washy movements if my inputs aren't smooth and slow.
- I've tried a few different suspension settings. 18/18 (front/rear) is great for DD in cold weather, 15/15 is great in warmer weather, 12/13 is a sportier setting for still comfy backroads corner carving.
- Much better balance, the car is neutral with a slight tendency to understeer as you add more power. Lift off oversteer actually exists now, before it would only tighten the line a bit if you snapped the throttle closed, now you have to be a bit more careful (smoother throttle closing) or you'll experience proper rotation.

Autocross use:
- I turned the dampers up to 5/7 (front/rear) and left them there for both events. Still perfectly comfortable on the street, but noticeably stiffer on poor pavement. I was attempting to combat the lack of upgraded front sway bar with the stiffer front damper setting, it seemed to work well enough.
- Fantastic control over bumps. I never feel like the car is going to misbehave over bumps now, which is a huge confidence booster.
- Nice transitional control (low speed damping) and the car responds how I'd like. In cooler weather at my second event with MUCH colder pavement I did notice that the rear would break away a little earlier than I'd like mid-corner. I definitely have some skills to brush up on here including learning to trust the car so I keep my foot in it to keep the car stable As I mentioned above, sharp throttle inputs can much more easily upset the car.
- Noticeably more controlled than stock as there's no waiting for the car to settle. Obviously any stiffer suspension will have this benefit.

Some general cons:
- Rear shock travel is limited a bit in my opinion, somewhat easy to bottom out on big (I'm talking BIG) bumps.
- Rear shock height adjustment is pretty tiny, I'm literally maxxed out lowering in the rear just to compensate for the height gained by using stiffer rear springs.
- As I mentioned, the solid top hats certainly transmit more noise and road feel (vibrations, feel of every little rock, etc) which is a touch tiring in DD use on poor condition winter roads. Not at all a con for any other use.
- Front height adjustment is a bit of a pain. Not something that's done very often, so very much a nit-pick.
- I do wish the front damping adjusters were on top, but being an inverted strut there's not exactly a good alternative.
- Only single adjustable. I do wish I could tweak compression/rebound separately, but that's obviously a known spec of the coilovers.

I'm really looking forward to getting it on track. The car has noticeably better balance in sweepers on the street and autocross which will translate very well to track use. The fast transitions and quick inputs for autocross lend themselves well to a car more biased to steady state understeer, but I may decide to add an adjustable set of sway-bars so I can tweak the balance beyond changing damper settings. It's still easy to adjust those back and forth for track or autocross use

As a whole, I'm very satisfied. Worth the money though? For the price I paid and doing the install and alignment myself? Yes. That said, I think anyone on street use that doesn't want the best off the shelf 50/50 street/track damper setup can look elsewhere. I've driven an FR-S on Bilstein B14s for example, and I liked that a LOT for a street and mild track setup. There's a critical balance there and for my use, the Ohlins R&T setup is brilliant.

Here's a video of one of my autocross runs. You can't hear any funny rattles from the suspension even with the mic in the trunk You can also see the suspension just soak up a manhole cover in the chicane near the end of the course and really handle a massive dip in the pavement well right into the finish line too.

[ame]http://www.youtube.com/watch?v=tZ5lW6j0E4w[/ame]



For an example of the oversteer that's much more accessible in autocross now, watch this video. Pretty clear that the rear steps out when I'm not fully expecting it (practice practice practice!). The final corner though, I felt that it was coming and just got on the gas and it straightened right up.

[ame]http://www.youtube.com/watch?v=S_AS6RMTm1Y[/ame]

[ajc209]

Great writeup. I dont think I could have said it better tbh. Although regarding only single adjustable, if ohlins offered that it'd add significantly to the price and probably make them too expensive.

Oh snap on the adjustable sway bars too!

[DocWalt]

Surely double adjustable would ramp up the price. FRSport can convert to double adjustable fronts, which I think would get most of what I wanted anyway.

As it is, I'm happy. No install issues (other than the stupid hexes in the shafts starting to strip before Ohlins' specified torque setting) and nothing has popped up since. They sure look pretty too

[ajc209]

I just torqued up the shafts by hand as much as I could and used torque marker paint on the bolt/thread so I should be able to see if they loosen off. The spec they gave was very high.

[DocWalt]

Good to know. Post up if you have any issues. My haven't backed off at all, but I am pretty peeved by the shafts looking terrible now. I should have stopped when it felt like I was going to break stuff instead of following torque specs, lol.

[mav1178]

I'm glad my initial install thread has given so much good feedback on this kit.

-alex

[ajc209]

Originally Posted by mav1178

I'm glad my initial install thread has given so much good feedback on this kit.

-alex

It certainly has Alex and I hope you dont mind it turned into a sort of official ohlins thread on here.

I must have read through this thread 20 times before I made the purchase.