What coils/spring rates for midsize E/UHP wheels (weekend/hobby drive)?
 

First of all, thank to all that contribute here on the forums. Along with the many that videoblog, I think the many evenings of reading and watching has helped me, hopefully, get a better understanding about suspension, and hence to make a better decision about how to mod my car. I am looking for some specific advice about what coilovers to get for my situation:


1) Weekend drives on backroads (like those here): [ame="https://www.youtube.com/watch?v=PMPn9TOH304"]Fun with GT86! - YouTube[/ame]


2) Going to and from work, when the sun is shining and I feel like it (it's not my daily drive). I won't be stuck in traffic it's pretty much the same roads as above to get there. I.e. I would take it, if I want an enjoyable drive and need not a huge emphasis on comfort.

3) I would like to start taking it to the track occasionally. I live in Germany only a good hour drive from Nürburgring and Spa isn't that far away either as examples. I would also like to take part in drivers courses and maybe do some auto cross at some point.

4) It would be nice to retain some capability to use the car for longer tours, like 500 miles autobahn (few times a year at most and I drive it with in ear noise reduction headset already on such stretches already). Or going away for the weekend.


As such, I would like to retain a good deal of street-ability, starting with wheels that remain practical. I got a set of used OZ 18x8 inch Ultraleggera wheels with Pirelli Nero GTs (bought the set for the rims). From what I read so far the Nero GTs didn't get the best reviews. I didn't have a chance to drive them myself yet (winter). The tire I am most interested in is the Yokohama AD08R, I had my eyes on those for so long, that those will probably be mounted in a matter of time.

Adjustable LCA are also on order and a brake line/pad upgrade will be done at next service. In a more distant future I would like a HKS compressor upgrade as well.

So to the question:
What coilovers would work well for me?
I initially looked at KW V3 4/5 kg, then KW Clubsport 6/7 kg, and after a lot of reading decided on the Öhlins Road & Track MI20 6/6kgs only to find out it has been discontinued. :cry:

I thought it would be more suitable for my needs because 1) as it's 1-way might be easier for a beginner like me and 2) the dampers were probably higher quality and 3) it appealed to me that they were the same rate front and rear.

Öhlins now make the MP20 with 4/3 kg spring rates. Initially I though it might be too soft, and it was weird with the soft spring in the rear. But from reading the advice of @Moto-P (http://www.ft86club.com/forums/showthread.php?t=10643), I am wondering if it after all might not be such bad a choice?

It's soft + it only lowers the car 20~30mm (the damper is probably high quality, has good stroke) + the AD08R is a ____ grip (medium or high in this context?) street tire.

Would the Öhlins MP20 be a perfect fit? I also consider AST, as they are fairly close to me. Would you advice to go with something harder for a tire in the category of AD08R and with the intended use?

Thanks for reading!

Do you have a budget??

Preferably <4000$ and given that I want to use the car something that is durable and doesn't require a lot of maintenance.

Okay, I would look into something you can get rebuilt local, as you may want to rebuild them every few years to keep then in tip top shape.

I also agree with you trying to stick to a 1 way system but if you buy a 2 way from a reputable dealer they can help you set them up I am sure.

I think you can get Ohlins built with custom specs cant you? Don't quote me on that but if you can I would go that route or if you want something really really good and are willing to pay a little more go with these.
http://counterspacegarage.com/jrz-rs1-brz-frs.html
I think you will have to contact them before you order them as they set them up to your car and needs as they are built to order.

If you want to take a cheaper road contact Fortune Auto (go for the 510)they also hand build their coils to order to your specs. I would call them and talk with them just to get an idea of what you are looking for, they know their stuff.

I should have mentioned that it should preferably be something I can source in Europe. The JRZ looks nice and I would be willing to go slightly above 4k for something extra nice. But unfortunately they will end up in 6k$+ with shipping and taxes. :(

I was thinking about the AST 1-Way 5100 too.
http://www.ast-suspension.com/websho...a-gt-86-detail

It's $2000 without options. With custom springs, a piston option that sounds fancy (double digressive, whatever that means) and top mounts it's a very reasonable $2500 and they are 2 hours drive away.

Here I could really use some advice regarding spring rates. Surely AST will have an opinion too, but still it would be nice to get some outside advice.

Bilstein would probably be his local option, B16 fits the bill under budget and can be adapted to his specs and chosen springs via revalving from someone local, faraway, or the factory, but that would take a ~$2k setup up to ~$3k+ and require some guesswork and trust with vendors, not everyone wants to go that route. They are maybe a little too street oriented in off the shelf configuration with spring rates on par with the soft Ohlins but that will help daily drivability.

Edit: Spring rates for B16 and B14 (cheaper no damping adjustment)
Front: 2.5-4.5kg progressive
Rear: 3.0-7.0kg progressive

Bilstein B16 PSS10 would be a good choice if you're okay with progressive springs. I don't prefer progressive springs for the track, but they're fine for fast back road fun.

The new Ohlins are very soft and I don't know if they have enough travel. We liked the old version on our car with the 6k and then custom 7k rates, but even then we wanted more stroke.

KW V3 would be a good choice. A little bit soft, but lots of stroke. They are comfortable and easy to drive fast when set up correctly. With the Advans you might be better suited to the KW Clubsports though. We make a custom valved and sprung KW clubsport over here and are very happy with them (RCE Tarmac 2).

AST is fine choice. It sounds like you get them a bit cheaper than we do over here.

- Andrew

Typically you'd want stiffer springs to accommodate stickier tires like the AD08R.

Right on, and those tires with the super soft Ohlins would be a poor match in my opinion.

- Andrew

For track situations, what would happen with a sticky tyre like AD08R with springs which are not stiff enough? Would this mean the suspension will be hitting the bumpstops through the corners? Would this worsen the car's handling? Would stiffening the damping help?

But wouldn't it still be better than having stiffer springs but crappy tyres?

Just for reference, my setup is koni shocks with RCE yellow springs 4.5kg square.

Sent from my LG-H815 using Tapatalk

Basically with sticky tires, your car grips hard enough and generates more cornering force so your car rolls more. In some cases it rolls onto the bumpstops if the springs are soft enough.

Yes, it will still be faster than stiff springs and crappy tires. Maybe not as fun, but faster.

Damping doesn't limit body roll in a steady state long corner, so it won't keep the car off the bumpstops in that case. It's felt in transitions, bumps, and corner entry/exit.

- Andrew

If the car isn't tuned to utilize the bump stops it will probably create erratic behavior if the body roll is high enough and the bump stops are stiff enough. Basically the car will all of a sudden get an extremely high spring rate once the suspension gets compressed into the bump stops, any changes in the road surface like a bump or kerb when the car is riding on the bump stops will jolt the chassis likely causing a loss of grip, even potentially a very small one. Whether or not this would be the case with the soft-ish Ohlins or B16's (which are nearly double the spring rate of OE) and AD08's I can't say, but bump stops can be shortened.

On a smooth course with well chosen bump stops maybe nothing will happen, totally unnoticeable, I've heard that the new ND miata is rather bump stop active from the factory. But bump stops can create some very undesirable behavior, namely sudden at the limit under or oversteer.

Again, I don't know if the AD08's are sticky enough to cause this behavior, they are geared for street/track use and a somewhat reasonable life expectancy means they aren't total gumballs, it will also depend on the track and setup (raising the car up will allow for more travel and more predictable suspension behavior). When you start getting into this level of detail even people with similar setups may not be comparable as they run big fast courses where they load up the car a ton vs. quick short courses that won't generate the g's to overwork the suspension with that level of grip.

Agreed with racecomp, damping would only help reduce roll in the scenario where your cornering isn't sustained, like an autocross and that would be a crutch where you're removing ultimate grip in order to band-aid another problem (springs not being stiff enough, ride height too low, bump stops too tall/stiff).

Thanks a lot for your replies all of you! :thanks:

@Racecomp Engineering, I asked Öhlins Nürburgring center about the reason for the 4/3 spring rates. Their product manager is supposed to get back to me after xmas.

Another forum user in the German GT86 forum apparently got a reply that Öhlins Sweden found the 6/6 "to be too unstabile on the limit". If that translates into that they want to make the car understeer more in long fast curves, then fair enough and it might suit some.
Only it would be hard to justify the price in that case, as a driver looking for such setup would probably be equally satisfied with more reasonably priced dampers like KV V1, or ST XTA (1 way with top mounts for 1000 usd, I don't think you got that variant in the US?).

@strat61caster, I don't know if I would want to experiment with custom Bilsteins, as I don't think I am knowledgeable enough to undertake such task.
And their stock springs seems so different from anything else that is offered, that I don't know how to relate to it.

Can someone perhaps expand on the benefits/disadvantages of the exponential rates? And which rate (low/high) applies in which situation? Am I correct in assuming that the higher rates apply when the spring is compressed? And couldn't it make for some unpredictable dynamics if the spring are unequally loaded?


From what I can summarise, I guess the AD08R would require 6-8ish k springs?

No matter what I look at for options, it seem to circle back to KW Clubsport.

I still keep AST as an option. I sent an email to them to inquire about what spring rates they use for their AST 4100, and what they recommend for the AST 5100 (which allows customisation).
The 5100 is upside down. Say that two dampers are equal quality, is there a huge benefit to an upside down damper? They are 2000 and 2500 usd here respectively. With the relative small difference in the price, should I go for the 5100?

I'll also await the reply from Öhlins before making any decisions. Since no one seems to run those dampers + if they have a good explanation for the change + they give me an Godfatherlike offer like installation, alignment and track time at Nürburgring = I might go ahead and try them.

Thanks again everyone!

The Bilstein spring rates are similar to OEM and most street oriented lowering spring options including Eibach which is supposedly the same as the TRD package with the rear being ~50% stiffer than the fronts. This also lines up with a few other setups like Tein SRC from CSG.

http://www.ft86club.com/forums/showthread.php?t=8739

They're different from the aftermarket that seems to like equal spring rates front/rear. Considering that the motion ratios in the rear mean that the effective spring rates in the rear are softer than the fronts given equal rates. Essentially the equal rates F/R results in a stiffer front than rear.

Here's an old thread from racecomp about it:
http://www.ft86club.com/forums/showthread.php?t=9936

I think you're correct, progressive spring rates aren't ideal and create a small question mark when it comes to how the car will react at the limit. Yes soft at initial compression and increasing spring rate upon increasing compression, but that's how most street cars are sprung, I believe the 86's stock springs are slightly progressive. It means a compliant ride on the public roads but stiffer springs when the car is pushed hard, reducing body roll when it's needed, but without creating harshness.

It's easy to say "yes, I'm all about maximum performance" and order what you think is best, but to live with that every day is an unknown until you do it.

Best of luck, there is no answer, only what makes you happiest.

:burnrubber:

I wonder if upgraded sway bars would help out the ohlins

I read the linked threads you mentioned. Hence, is why I find the Öhlins MP20 rates weird. Most race oriented setups seems to have 1 or 2 kg more in the rear.

That leads to a the question, as the stock GT86 is also 1 kg more in the rear (2.3/3.3). "To retail the stock feel":

1) The "1 kg more rear" is an "absolute value"? I.e. 2.3/3.3, 4/5, 6/7 9/10 etc? A lot of manufactures seems to follow that schedule.
Or
2) Should the rear become proportionally harder, the harder the springs in the same ratio as the original setup? 2.3/3.3, 5/7, 7/10 etc? Bilstein seems to follow that kind of ratios?


It leads straight to the next question, as I got a mail from AST...

Both their 4100 and 5100 coilovers are delivered with 4 kg/mm front and 7 kg/mm rear.... (Edit: the other way around 7 kg/mm front, 4 kg/mm rear)
Am I right in thinking it seems like it could be a very fun and tail happy setup, everything else being equal? <--- disregard
The 5100 is also customisable for a small extra (about 100 - 200$ afair).

What do you think of those standard rates? It seems almost like the same philosophy as Bilstein, only non-progressive. <--- disregard

I'm tempted to go with custom AST 5100! What rates would you recommend for a track oriented (street tires) setup (225/40/18 AD08R as an example)?

I saw @Captain Snooze, was running the AST 5200 with 9/10 kg/mm springs, but on slicks and the question is if there is a huge difference in the quality of the the 5100 and 5200 damper, that it can facilitate higher rates?

Would a more moderate setup be more appropriate?


I will of course ask AST as well, as they probably know their dampers the best. Still it would be great with an outside opinion, so they don't sell me the springs that they have the most of in stock. :D (Just kidding, but I trust the combined Toyobaru experience here would be a good input).

Seeing as you're in Germany, I'd recommend looking into the SACHS Performance Coilovers as well. They will be local to you, their office is located in Schweinfut, and seem to be a great option for a daily driven car that will occasionally see track time. They are a single adjustable coilover with an inverted monotube damper in the front and monotubes in the rear as well. The spring rates are a bit softer than other options on the market, Front Rates: 38N/mm Rear Rates: 30-45N/mm (progressive), but this should make for a better compromise between daily and track driving. The most comparable option out there would be the Bilstein B16, the Ohlins R&T is a little more aggressive setup.

I recently got a set, although I won't be installing them until after winter, but I'm very excited. This is my only car, so it is daily driven and will also see at least 3 track days next year, more likely 5-6. Full disclosure, I do work for ZF in the U.S. but not in the race engineering division. I asked our U.S. suspension guy, a German, about the softer rates and he said that they suited the handling dynamics they were seeking more and that the focus was on proper valving to make the coilovers ideal for both street and track driving. If you wanna see some pictures and other info you can check them out on the thread I started http://www.ft86club.com/forums/showthread.php?t=97549

4 kg/mm front and 7 kg/mm rear is a pretty big split. It's not the way I would go.

We usually go with even rates front and rear and occasionally a slightly stiffer rear, depending on driver and intended use.

Mostly, I would say that 4 kg/mm front is very soft for performance driving. The front will roll a lot, and unlike the rear, it is a mcpherson strut suspension that does benefit from firmer rates.

- Andrew

I've heard 'proportionally harder' as it's maintained ~50% across setups with stiffer rears, there was a post by CSG like a year or two back about it that I can't seem to find... Did find this though:
http://www.ft86club.com/forums/showthread.php?t=37684

There are many many other factors to the car setup that will determine whether it will under or oversteer: alignment, bump stops, sway bars, damping, even tire pressures can skew the balance and make even the most unbalanced spring rates over/understeer.

For instance I am currently using the B14's and at my first event last weekend I struggled with understeer all day despite having a very balanced and effective car on the stock springs and dampers just a few weeks prior. There are a few things I know I did wrong and can correct in the setup to help bring the balance back but if you just blindly assume the spring rates were the dominant factor you'd expect similar handling to stock if not more oversteer.

Sorry, I have to correct myself, reread the mail from AST and he mentioned the rear spring first, and I didn't look carefully enough.
The AST 4100 coilovers come with a fixed 7 kg/mm FRONT and 4 kg/mm REAR.

The AST 5100 coilovers are customisable, but will come 7/4 kg/mm too if nothing else specified.

Again sorry for the confusion.


It's funny, but SACHS doesn't seem to want to sell their coilovers in Germany. I can't find them anywhere, and I never hear of anyone having them installed. They look nice though.
I think I would feel like too much of a guinea pig going with those (same as with the proposed custom Billstein).
Anyway, they are in the other end of Germany, so a fair distance away 4 hours drive. I am actually much close to the Dutch border and less than 2 hours from AST. I am also just 1 hour from Nürburgring (Öhlins). I think I will visit them in the new year.

Yes, I don't know if I'm too hung up on the spring rates.

To clarify the assumed basic setup I have in my head, when I think about the springs:
225/40/18 AD08R
Front 2.8 deg camber, slightly toe out.
Rear 2.0 deg camber, neutral toe

With the above aprox. setup, would 7 kg'ish springs be a good figure? With, say, 8 rear?

(It seems to be around those alignment/spring values good KW clubsport setups have).

TOR: with the greatest respect to everyone who's posted, please consider one very simple rule of thumb: grip goes to the soft end. Stiffen the rear and you'll move grip to the front (oversteer); Stiffen the front and you'll move grip to the rear (understeer).

Take your car to the track, it's awesome right out of the box. After a few track days decide whether the car understeers or oversteers for you - it's up to you, not me. My BRZ 'pushes like a pig' (obscure JV reference...), and it drives me nuts. But it's not too soft - there are bumps at my tracks so I need compliance.

The GT86 seems to be set up a bit softer with better balance than the American FRS (oversteers) or BRZ (understeers). Here's a chart of spring rates from popular companies. Ratios closer to the FRS will oversteer more, closer to the BRZ will understeer. This is assuming OE sway bars.

F R F/R
OE BRZ 2.7 3.5 0.771 (pushes)
OE GT86 2.3 3.3 0.697 (balanced)
OE FRS 2.3 3.8 0.605 (loose)
---------------------------------------------------
Swift 3.8 4.5 0.844
RSR-Down 2.8 4.5 0.622
RSR-SuperDown 3.2 4.5 0.711
Eiback Pro 3.6 4.9 0.735
hotchkis 3.3 4.7 0.702
Race Comp yellow 4.5 4.5 1.000

You can see that every setup is stiffer (higher rates), with close to GT86 balance (ratio). It's easy to see that the OE FRS is set up to oversteer, and the RC Yellows will understeer on the OE sway bars. A setup as stiff as the yellows means very little bump compliance, so don't show up at the 'ring and expect to have any fun.

My OE FRS pushed like a pig. Camber in the front changed the balance and with enough camber I could get the car to oversteering, but adding camber in the rear would have brought back the understeer. Honestly was quite happy with the OE suspension and would still be using it if I didn't have a mind towards competition.

Yes we've gotten too hung up on spring rates for what's supposed to be a fun non-competitive car.

You are making generalizations. The difference between oem FRS and BRZ is marginal. Driver input is more significant. You are giving off the shelf spring rates as opposed to effective rates given the motion ratio at the rear.

From your quote above with motion ration taken into account the there is bugger all difference between the models. Best of luck feeling difference of 0.4 kg/mm
(I have used 0.95f and 0.75r ratio. )
OE BRZ 2.4/2.0.........0.4
OE GT86 2.1/1.9.......0.2
OE FRS 2.1/2.1........ 0.0

It is the difference f/r not division/multiplication that should be the concern. That is, using your example, on a car with 1:1 motion ration front and rear using 2k springs front and 8k springs rear gives the same balance as 4k/16k springs. I am saying 4k/10k springs would give the same balance.

Thanks for joining Captain Snooze, I read your thread about the AST with great interest.

To see if I got this right allow me to continue your calculations:

(using 0.95f and 0.75r ratio again)
Öhlins R&T MI20 6/6 becomes: 5.7/4.5..... 1.2 front
Öhlins R&T MP20 4/3 becomes: 3.8/2.3..... 1.5 front
KW V3 4/5 becomes: ..............3.8/3.75.... 0.05 balanced
KW Clubsport 6/7....................5.7/5.25... 0.45 front
AST (Captain Snooze 9/10).......8.6/7.5..... 1.6 front

Odd ones:

Bilstein (hard rates 3/7)...........2.9/5.25... 2.35 rear
AST 5100 (stock 7/4)...............6.7/3.0..... 3.7 front

I see now why KW V3 is such a safe bet setup?

I think this thread has helped me getting out of "must mod!" state of mind. I really like my car (GT86) as it is. My car both oversteers and in some situations it pushes. My theory:

Low speed curves, high steering deflection (high camber front, due high castor) = Oversteers quite happily.
High speed curves, low steering deflection (low static camber front and castor not giving an effect) = pushes like a pig.

If the above theory is correct, Toyobaru made the car quite safe as it is manageable but still fun for inexperienced drivers.
I am by no means an expert driver, but it annoys me that it pushes under power, when taking a fast curve. On the other hand I wouldn't want it to violently kick it's tail out at 100 mph! Ideally I would like the rear just to start talking a bit when pushed.

The questions is, if this is rather an alignment issue and a bit more static camber up front would solve that.

Also I am not taking into account, that I didn't drive it on my new wheels yet. So the above behaviour might be more pronounced due to the Michelin Primacies. :bonk:
In any case, I will slow down my decisions and drive the car on the new wheels first. I ordered LCAs and camber bolts already, which I might then install with the stock suspension and give it a proper alignment.

@ansibe, thank you for your post too. You have many good points that were helpful. I should really consider no going too firm, as my backroads are rough like the ring. :)
I think I agree more with Captain Snooze's calculations though.
Also the examples you mentions are lowing springs. So for the example with "Race Comp yellow" a 4.5 spring rate would really not be well matched for the stock damper.
A set of coilovers at 4.5 with well matched damper is another thing?

No, that is incorrect.
Effective spring rate is spring rate x (ratio^2)
In the first example (using .95f/.75r)
Öhlins R&T MI20 6/6 becomes: 5.4/3.4..... 2 front

Then nothing is close to stock, with KW V3 still being closest.

Bilstein (hard rates 3/7)......2.7/3.9... -1.2
Stock FR-S........................2.1/2.1... 0.0
Stock GT86.......................2.1/1.9... +0.2
KW V3 4/5........................3.6/2.8... +0.8
KW Clubsport 6/7...............5.4/3.9.. +1.5
Öhlins R&T MP20 4/3..........3.6/1.7.. +1.9
Öhlins R&T MI20 6/6...........5.4/3.4...+2.0
AST (Captain Snooze 9/10)..8.1/5.6...+2.5
AST 5100 (stock 7/4)..........6.3/2.3.. +4.0

When increasing sprig rates, what is the reason for increasing the effective spring rate more in the front than in the rear?

Why doesn't e.g. 4/6 front/rear make sense = 3.6/3.4 effective? Or e.g. 6/9 (5.4/5.1).

Trying to get my head around this! :bonk:

Edit: My question has been asked and answered over here:
http://www.ft86club.com/forums/showthread.php?t=9936

It's important to keep in mind that the stock suspensions are also very bumpstops active and very much used in cornering.

- Andrew

I now spent the last 14 day every evening researching which Coilovers to get. In the process I came across some info that may surprise some.

It is well know that the KW V1 is the same as the ST X, only that the KW is stainless steel. The two set use the exact same springs (4 kg/mm front, 5 kg/mm rear) as can be seen from the German TÜV documents, which list their specifications in detail. It is a German requirement, that the springs are marked. And the markings has to correspond with the documents when the car is brought in for it’s biannual “TÜV inspection”.

I am slowly getting to the point bear with me for a few more lines: Fact is that the 4/5 V1-springs are also the EXACTLY the same as those used for the european version of the KW V3.
We also have the US V3 (6 kg/mm front, 7 kg/mm rear) rates available, but it is sold as “KW Clubsport”. Over here, it’s a well know (and from KW confirmed) fact that it’s the same damper being used in both kits. They even retro-actively changed some early customers TÜV papers.

All in itself not so particular interesting…

The interesting part is about the galvanized ST branded rebound-only adjustable “XTA” - a.k.a. not-available KW V2. Interestingly enough, it uses the 6 kg/mm Clubsport/US V3 spring on the front, and the XT/V1/"Euro V3" 5 kg/mm spring at the rear.

That kit comes with front camber adjustable top mounts and for a price of 1,200$. From the respective manuals, it appears it’s the same top mounts too…

XTA manual:

http://s18.postimg.org/oe2tgfke1/Scr...t_05_51_19.png

Clubsport manual:

http://s2.postimg.org/5edm8o9mx/Scre...t_05_52_08.png


Before doing this research I was skeptical about the price, and I was under the impression it had much lower spring rates.

I imagine KW (even under their ST brand) wouldn’t release a kit where the dampers can’t support the spring rates. So I would take the relatively high rates (compared to the V3/Clubsport), as an indication that this might be a damper of good quality. Several people here are running them and all seems to be happy with them.

The 6/5 XTA spring rates doesn’t appeal particularly to me. But for 1200$ instead of 2500, there is plenty of room to spare to buy some new ST sway bars to dial out possible understeering tendencies. Btw the ST swaybars cost 300$ as opposed to the (exact same) KW swaybars that goes for 500!

Swaybars, even listed side by side on the German KW site: lol :D

http://s23.postimg.org/ikhvh67cr/Scr...t_05_54_10.png



Alternatively, since the V3/Clubsport springs are interchangeable, it could be that it is possible to use the 7 kg/mm Clubsport spring in the rear.

I think my decision has been made up... It may be a surprising decision, when I started out with a budget of 4000$. But I think I'll go for the XTA + swaybars, and spend the rest on beer and girls. :cheers: And if the decision turned out to be wrong, it would be very easy to part with those coilovers used. Thanks for all the input! :thanks:


Documentation for all the above claims:

ST XTA: http://docs.kwsuspension.de/ga-STXTA-58804_1094-14.pdf
ST X: http://docs.kwsuspension.de/ga-STGFw-58004_1237-12.pdf
V1: http://docs.kwsuspension.de/ga-KWGFw-58004_1237-12.pdf
Euro V3: http://docs.kwsuspension.de/ga-KWGFw-58004_1237-12.pdf
US V3 / Euro Clubsport: http://docs.kwsuspension.de/ga-KWCS-...04_1248-12.pdf

^ interestingly I've recently driven 86's with Flex-Z (6k/6k) and ST (6k/5k). With the damping pressure adjusted -1 click on the Flex-Z and -1 turn on the ST from full stiff the ST is noticeably more aggressive (firmer) feeling than the higher sprung flex-Z. Both cars had wayyy more grip than they need. (255 wide 595rsr on the Flex-z equipped car, and 265 wide tires on the ST equipped car.) I would have to drive the ST equipped car some more to get a better impression, but it definitely feel like they offers more damping force over the Teins. Both cars have never seen the racetrack either.

One click from full stiff is very far from the recommend default setting of 9 clicks.
I am not sure what you mean with too much grip.

If you mean difficult breaking traction rear, then that is exactly my concern with the softer springs to the rear. I don't mean drift or wheel spin, but rather to get the tail of the car to "move around the corner".
I believe I have a pretty good feel for cars, but it's new for me to put it into words and I am never sure if I use the right terminology, but I believe that is what is meant when people say "rotate".

The above would be my purpose of getting the the swaybars, so I can make the rear a little stiffer if needed.

@Racecomp Engineering
Thanks Andrew, this just really makes it even more difficult for us mortals to make any educated guess on how a coilover might perform from the stats alone.
Who knows, take e.g. the Öhlins R&T 4/3 kit. Maybe it's great, even if the numbers are not in line with the majority. As long as no one tried them? Maybe Öhlins made a golden combo and it's being dismissed just by the numbers?

This is also why I'll go with the ST XTA, it will get me started off without a big investment, and I can continue to improve upon my knowledge with practical experience. Down the line I can change, if needed and at that point I will hopefully have a better knowledge about my true needs.

At the "default" setting for the flex z I believe it was 7-8 clicks out from fill stiff there was too much body roll and the rear end would wallow from making contact with bumpstop, even at -5clicks. It only when I jacked it up to -1 that it would be less pronounced. But the flex z weren't designed for the kind of driving I was doing with them. The ST's I've not had the chance to really toss it around some bends, but I've a feeling, even with its lower spring rate, it will not have the problem bottoming the rear under hard cornering because of the damping it provides. From initial impressions I think the ST are more performance oriented. I'm sure the T0 would be even better in this regard, though that's just my assumption since I've not tried them myself.

I'm sure there is a very good reason why the AST guys are using such low spring rates in the rear. As the saying goes, "there is more than one way to skin a cat," or something to that extent.

Captain Snooze, you’re right, I should have accounted for motion ratio. This is a complex subject and I over simplified. I’m making a similar choice as TOR (at a lower price point), and I want the car to be more balanced on my tracks with OE tires. I know I’m not supposed to like the OE tires, but I’ve tried OE, all-season, max perf summer, and snows (yes, on the track) and I find the OE Michelins best for the brz.

TOR, I like your choice. You’re making a conscious decision, and I’d love to hear how it works out for you. FWIW, I’m from the bike world and I’ve never heard of a bad Ohlins set-up, or a cheap one!

I’m shooting for 25mm lower, maximum. Lower CofG resulting in less body roll is all good. Of course I’ll need stiffer springs which will compromise bump compliance and probably necessitate better dampers. That’s a double edge sword - better dampers would be nice, but they’re not free.

If I go 25mm lower at both ends, I’ll add more camber at the back than the front. That’ll make the balance worse unless I use very stiff rear springs, or sways ($$). Or I could dial out the camber with LCAs …. more $$.

There’s also a good chance Andrew from RCE has nailed my problem. The front suspension is collapsing onto the bump stops, dramatically increasing the effective spring rate and causing the front to wash out.

I tracked the OE tires 2x and autocrossed them at least 2x and I think they're seriously underrated. Yeah they're not fast or grippy but they're relatively well mannered on the road, communicate and lose traction progressively, last a really long time, and contribute to the good fuel economy.

FWIW the Primacy's could almost qualify for 'max performance summer' and are already classified as a summer tire (not all-season) you haven't really tried a tire that's objectively noticeably better as a performance tire than the Primacy yet.

And I totally agree with your assesment of understeer when lowering the car, I saw the exact same things (may have posted it earlier in this thread even...) after installing my B14's. So far camber plates have been my favorite change bar none over coilovers and tires (Dunlop ZII Star Specs in OE size) the added grip up front means you can get the car very balanced on stock suspension for autocross or track and then slide it back to reasonable levels for street driving.

I just received my XTA's today and your posts are giving me positive reinforcement that I made the right decision based on my needs and budget!

I had ST-X's on my previous car and felt they were to soft and under damped based on my preferences. Great for going low and a stock like ride but always on the bumpstops through the fast turns.

http://i96.photobucket.com/albums/l1...pstw8bd88v.jpg

Looking forward to you opinion about them.

When are you installing them?

This weekend!

Lucky you. :-) Do you have a build thread? Could you perhaps make a couple of photos before putting the wheels back on?

Any updates @yip? :)