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Track-focused build underway - Bilstein Clubsport / OS Giken
The aftermarket has matured nicely for these cars, so I'm excited to get my GT4 "clubsport" type build underway, similar to my GT3. I was very fortunate to have a good friend who was selling his GT4, which already had some really nice parts (Dundon headers, Cobb Pro tune, 19" BBS E88, caliper and wheels studs, etc. etc.), so it's a great base to build upon. My typical focus tends to be on handling, not so much on power, so the headers/tune already put it on-par with 718 cars and should be plenty quick in a straight line. I plan on using some parts which I have alot of experience with, but they don't seem to be quite as common in GT4 land, but they probably should be.
A couple highlights are Bilstein Clubsport suspension kit, and OS Giken LSD. The Bilstein clubsports are a bomb-proof, double-adjustable, inverted monotube suspension that is really good. I considered Ohlins Road & Track and TTX's, but the Bilsteins slot in nicely in between both Ohlins and I run the clubsports on my E92 M3 track car and they are fantastic. I already have TTX's on my GT3, and while they are amazing, for the GT4 dual strut setup, they are wildly expensive. The clubsports are almost half the cost, but only marginally more expensive than the Ohlins DFV kit, and the double adjustability is nice to have. I run re-valved Ohlins DFV's on my FRS and miata race cars, and they are great, but there are times I wish I could independently control comp/reb on each end. MCS and KW shocks aren't inverted monotubes, and still cost alot more for an inferior product (except KW's competition line). I am uprating the springs to 120/160 N/mm (~700/900# ), and having PSI re-valve since this car will be basically full time track. The kit comes with 457/685# rates, and while those are perfectly good for track use, from testing and using 600-700# springs on the front of the GT3 (which is the same as GT4), the car further responds to these spring rates on sticky tires. The adjustment range is nice and defined, and completely usable, unlike alot of other shocks which tout 20+ clicks but in reality half aren't even useable because both ends are either insane stiff or soft, and pointless to have. I'll post up some pics when I receive them, which should be very soon.
Regarding the LSD, I know the "gold" standard here is Guard GT's LSD, and it is awesome, I had one in my 997.1 RS, but I've since been running OS Gikens in my 987.1, FRS, and miata, and I have to say, I slightly prefer the GIken. The issue is that OS Giken themselves have never listed the GT4 as a fitment, even though they list the 981 Cayman-S 6spd, which uses the exact same gearbox and diff. I have told them they are costing themselves quite a bit of business by not listing the GT4 as an option, since perhaps the casual buyer/vendor may not know they can still use the Giken. Hopefully they will be updating their marketing materials in the near future to address this issue. It also comes with a forged housing, and is ~$1000 less than the comparable Guard unit.
Also going with the Brey Krause harness kit, which allows you to mount to the rear bulk-head (similar to factory clubsport style), which also means there is no need for a heavy rollbar to be installed, and probably saves about 35-50lbs depending on which one is used. It installs cleaner than a simple harness bar with less cutting of carpet required as well.
Most of the parts have arrived, so install should start in a couple weeks with some track-testing and chassis sorting in early March. Will continue to post up pics and review, so perhaps some of these lesser used parts may get a little more love that they deserve.
· Bilstein Clubsports - 120/160 N/mm springs
· SP Front strut tower braces
· Ohlins PASM cancellation kit
· BBI inner control arm monoballs – front and rear
· Solid caster pucks - front
· TPC Offset Toe links – offset inner flange/bump steer
· Toe-link lock out kit
· Brey-Krause harness mount kit
· Schroth 4pt belts for GT buckets
· OE heat shields – 9A1
· Heat wrap headers – collector section
· NACA duct install to underbody (additional airflow into the engine compartment)
Interesting on the Bilstein kit. It's actually less than half of the TTX kit in Europe (38xx USD pre-tax). What kind of spring rates do you think the stock valving is good for?
I've found that adding a lot of spring rate at the front worked pretty well on a 981. Closer to equal F:R than keeping the big stock split. On my non-GT4 981 race car we've actually gone 140/140 N/mm and it's a lot better than it was with 160 rear springs. But we run slicks, and that car doesn't have exactly the same suspension as a GT4. And it's on JRZ RS pro2. Not my best ever purchase, but they work OK.
I'm interested in these Bilsteins for my 718 GT4 which would be more of a road plus trackday car on Cup 2.
Interesting on the Bilstein kit. It's actually less than half of the TTX kit in Europe (38xx USD pre-tax). What kind of spring rates do you think the stock valving is good for?
I've found that adding a lot of spring rate at the front worked pretty well on a 981. Closer to equal F:R than keeping the big stock split. On my non-GT4 981 race car we've actually gone 140/140 N/mm and it's a lot better than it was with 160 rear springs. But we run slicks, and that car doesn't have exactly the same suspension as a GT4. And it's on JRZ RS pro2. Not my best ever purchase, but they work OK.
I'm interested in these Bilsteins for my 718 GT4 which would be more of a road plus trackday car on Cup 2.
For dual purpose, I'd say the kit springs 80/120 would be just about perfect for Cup2/Dunlop/Trofeo type tires and some road use. Or you could easily go to 100-110 front springs without any revalve, if you already like the 120 rears. The Bilstein engineers told me the same thing you hear from any shock company, once you go about >20% higher in spring rate, it will benefit from a re-valve. Not a must do, but since I was going up 50% rate in front, I decided to do it. That said, I went from 100/140 on my M3 Bilsteins to 150/210 without a re-valve and they still feel and adjust fine.
I like that that Bilstein keep a nice split F/R to help reduce understeer and allows nice handling without extreme alignment requirements for better street manners. The Ohlins DFV (and the other "spring only" kits) use too soft of a rear rate at only 90 N/mm, but still use 80 fronts. I chose to keep the same spring 40 N/mm split as Bilstein to baseline the car, and can adjust from there. I'll be running on 265/295 R7's, so plenty sticky to work with those rates. TTX come with 120/140 springs, so I'm sure that's ballpark, but my car has the higher wing risers and a wicker so it's making more rear downforce, and it's a heavier car than a clubsport.
I think the heavier weight of a street car, and higher rear downforce will play nice with the 160 rear springs. Testing will confirm though.
Most importantly, yes, the price in the UK/Europe is fantastic. I tried to buy direct from UK, but Bilstein didn't have any in-stock for immediate shipment and gave me a few months lead time. If I had more time to wait, I would have waited, but got a very good deal here in the USA for my set which is in-stock for immediate shipment.
Are you installing the harnesses on the passenger side?
Nope, nobody rides in my passenger seat on track. It always amazes how many people/shops hack holes in their beautiful bucket seats to have "matching" 6pt harnesses for a seat that nobody rides in. Unless you instruct and routinely have people ride with you, it's a pointless mod for a passenger seat. Not to mention, nothing worse than a sub/lap belt constantly in the seat.
Carbon buckets with Schroth GT3 4pt ASM belts are the PERFECT setup for a DE/dual purpose car. There's a reason the owner of Schroth made these belts.....because he also owns a GT car.
Nope, nobody rides in my passenger seat on track. It always amazes how many people/shops hack holes in their beautiful bucket seats to have "matching" 6pt harnesses for a seat that nobody rides in. Unless you instruct and routinely have people ride with you, it's a pointless mod for a passenger seat. Not to mention, nothing worse than a sub/lap belt constantly in the seat.
Carbon buckets with Schroth GT3 4pt ASM belts are the PERFECT setup for a DE/dual purpose car. There's a reason the owner of Schroth made these belts.....because he also owns a GT car.
Yea that is what i was thinking when i found out that the pass seat wasn't pre cut for it. I was wondering what people are doing to make them fit. Or they just don't put the sub belt attachment in. I was thinking I don't want to have to cut my LWBS to put them in. That seems kinda silly to me.
Great build, I think if someone really wants their road car to feel like a "track car", suspension mods are the ticket. Remove the rubber and get a real track suspension.
Nope, nobody rides in my passenger seat on track. It always amazes how many people/shops hack holes in their beautiful bucket seats to have "matching" 6pt harnesses for a seat that nobody rides in. Unless you instruct and routinely have people ride with you, it's a pointless mod for a passenger seat. Not to mention, nothing worse than a sub/lap belt constantly in the seat.
Carbon buckets with Schroth GT3 4pt ASM belts are the PERFECT setup for a DE/dual purpose car. There's a reason the owner of Schroth made these belts.....because he also owns a GT car.
I had the QFP's on my E90 M3, made a big difference with stock seats. I imagine with the LWB's they are even better. I was going to go half cage, 6 point etc. but leaning towards just doing the Brey Kreuse mounts with the 4 point Schroth so good to see some real feedback. I still like to drive the car on the street and dont want the center belt sat there the whole time. I'm also not cutting up my passenger seat for the occasional passenger or instructor ride!
I had the QFP's on my E90 M3, made a big difference with stock seats. I imagine with the LWB's they are even better. I was going to go half cage, 6 point etc. but leaning towards just doing the Brey Kreuse mounts with the 4 point Schroth so good to see some real feedback. I still like to drive the car on the street and dont want the center belt sat there the whole time. I'm also not cutting up my passenger seat for the occasional passenger or instructor ride!
FWIW, you can hide the crotch belt by removing the cam lock and laying the belt flat under the seat cushion. See this thread.
I had the QFP's on my E90 M3, made a big difference with stock seats. I imagine with the LWB's they are even better. I was going to go half cage, 6 point etc. but leaning towards just doing the Brey Kreuse mounts with the 4 point Schroth so good to see some real feedback. I still like to drive the car on the street and dont want the center belt sat there the whole time. I'm also not cutting up my passenger seat for the occasional passenger or instructor ride!
You will not regret it. The half cage can always be added later if you want the "clubsport" look, or more rollover protection, but even if I did a half cage, I would still do the BK harness mounts.
I've had these in my GT3 for 3 years now. Love them.
Also going with the Brey Krause harness kit, which allows you to mount to the rear bulk-head (similar to factory clubsport style), which also means there is no need for a heavy rollbar to be installed, and probably saves about 35-50lbs depending on which one is used. It installs cleaner than a simple harness bar with less cutting of carpet required as well.
I did the same. Rear visibility on the road is already not great, so adding a cage into a mostly street-driven car wouldn't help, and not having a bar in front of the firewall allows for a larger range of rearward seat travel. Have my first track day of the season in late March, so looking forward to having proper belts 👍🏼
Originally Posted by Mvez
Regarding the LSD, I know the "gold" standard here is Guard GT's LSD, and it is awesome, I had one in my 997.1 RS, but I've since been running OS Gikens in my 987.1, FRS, and miata, and I have to say, I slightly prefer the Giken
If you search the forums, there's a pretty epic thread from several years ago between Paul Guard and a Giken sales rep that couldn't stop putting his foot in his mouth. Drama aside, it ended up being an educational thread & I learned a ton about LSDs from it.
If you search the forums, there's a pretty epic thread from several years ago between Paul Guard and a Giken sales rep that couldn't stop putting his foot in his mouth. Drama aside, it ended up being an educational thread & I learned a ton about LSDs from it.
Yeah, that's an oldie but goodie. That's the difference seen between a guy who owned the company, and a guy just selling a product. There's some selling going on both sides, but that rep was kind of a clown. OS Giken moved to fully forged housings after they had a few failures in the higher hp/tq applications years ago, and that seemed to solve the issues. I still love Guard LSD's....it's a first-class LSD, but so is Giken. Like I said, I use them both, but sometimes it's beneficial to the entire track community to know about other products that can serve them just as well. The other thing I really like about Giken is their design inherently behaves nicely on the street, as it doesn't have lots of preload or locking when cruising around on the street, and is very progressive on lockup. It just does it's job without you really even knowing it's there. For any dual purpose car like GT3/GT4's, it's a really nice trait to have.
Just like every forum, there are definitely fan favorites, and often rightly so, certainly for Guard. But for example, if you jump on a BMW forum (which I do for my M3), everybody is on the MCS shock bandwagon, as if it's the greatest thing ever. Sure, it's a nice shock, but they aren't even inverted monotubes....nobody ever seems to talk about that glaring fact. The reason MCS aren't is because it's more expensive to manufacture inverted monotubes (which are a superior design for racing struts), and is why only the big boys like Bilstein and Ohlins are mass producing inverted monotubes for performance applications, and can offer them more affordably. Economies of scale. KW offers inverted monotubes too (competition line), but they are the top of the line option that costs the most. That should tell you all you need to know about these boutique smaller shock companies like MCS and JRZ, which neither offer inverted monotubes that I know of, and if they do, are astronomically priced. Vendors and customers like dealing with them because you get quick service and sales, and it feels easier and more "custom", compared to dealing with OE supplier behemoths like Bilstein, Ohlins, or KW. Sure, MCS/JRZ are nice products, but the hype is a bit much, and alot of it is forum generated. JRZ was everywhere on Rennlist a few years back, I had their RS Pro shocks on my 987, and I'll never buy JRZ again. The Bilstein Clubsports just don't have alot of applications, that's the real reason they don't get as much exposure as they should. Hell, most people don't even know they offer a kit for the 991 GT3/RS and 981/718 GT4....that's the point.
Or in BMW land, all the LSD's are from DiffsOnline or another forum favorite. They wont explain that most of their base LSDs are a 2-way based upon an existing BMW LSD, which is inferior to a 1.5 way OS Giken. Plenty of guys running Gikens there too, and all love them. But some salespeople will try to talk you out of them, and also cite rare early instances of failure to try and steer you away. I know probably 25-30 people, personally, with OS Gikens in every type of car, and I've never heard anything but very happy results, and never once heard of any failure. My 987.1 was beat on in full race conditions for 6 years, and I just rebuilt it after 5 years of abuse, and that was without any tranny cooler.....which is nuts because 987.1's gear fluid runs crazy hot, which is not good for anything in there.
We would endurance race the Gikens in our miatas, without trans coolers, which is nuts to do when you have 2 x 8 hour races a weekend on less than 1L of gear oil. Never once a failure, and went crazy long before a rebuild was required. All we would do is change the fluid after each race weekend.
This isn't a "it's better" or "faster" exercise, I'm just saying there are other high-level options out there, and options aren't bad.
Yeah, that's an oldie but goodie. That's the difference seen between a guy who owned the company, and a guy just selling a product. There's some selling going on both sides, but that rep was kind of a clown. OS Giken moved to fully forged housings after they had a few failures in the higher hp/tq applications years ago, and that seemed to solve the issues. I still love Guard LSD's....it's a first-class LSD, but so is Giken. Like I said, I use them both, but sometimes it's beneficial to the entire track community to know about other products that can serve them just as well. The other thing I really like about Giken is their design inherently behaves nicely on the street, as it doesn't have lots of preload or locking when cruising around on the street, and is very progressive on lockup. It just does it's job without you really even knowing it's there. For any dual purpose car like GT3/GT4's, it's a really nice trait to have.
Just like every forum, there are definitely fan favorites, and often rightly so, certainly for Guard. But for example, if you jump on a BMW forum (which I do for my M3), everybody is on the MCS shock bandwagon, as if it's the greatest thing ever. Sure, it's a nice shock, but they aren't even inverted monotubes....nobody ever seems to talk about that glaring fact. The reason MCS aren't is because it's more expensive to manufacture inverted monotubes (which are a superior design for racing struts), and is why only the big boys like Bilstein and Ohlins are mass producing inverted monotubes for performance applications, and can offer them more affordably. Economies of scale. KW offers inverted monotubes too (competition line), but they are the top of the line option that costs the most. That should tell you all you need to know about these boutique smaller shock companies like MCS and JRZ, which neither offer inverted monotubes that I know of, and if they do, are astronomically priced. Vendors and customers like dealing with them because you get quick service and sales, and it feels easier and more "custom", compared to dealing with OE supplier behemoths like Bilstein, Ohlins, or KW. Sure, MCS/JRZ are nice products, but the hype is a bit much, and alot of it is forum generated. JRZ was everywhere on Rennlist a few years back, I had their RS Pro shocks on my 987, and I'll never buy JRZ again. The Bilstein Clubsports just don't have alot of applications, that's the real reason they don't get as much exposure as they should. Hell, most people don't even know they offer a kit for the 991 GT3/RS and 981/718 GT4....that's the point.
Or in BMW land, all the LSD's are from DiffsOnline or another forum favorite. They wont explain that most of their base LSDs are a 2-way based upon an existing BMW LSD, which is inferior to a 1.5 way OS Giken. Plenty of guys running Gikens there too, and all love them. But some salespeople will try to talk you out of them, and also cite rare early instances of failure to try and steer you away. I know probably 25-30 people, personally, with OS Gikens in every type of car, and I've never heard anything but very happy results, and never once heard of any failure. My 987.1 was beat on in full race conditions for 6 years, and I just rebuilt it after 5 years of abuse, and that was without any tranny cooler.....which is nuts because 987.1's gear fluid runs crazy hot, which is not good for anything in there.
We would endurance race the Gikens in our miatas, without trans coolers, which is nuts to do when you have 2 x 8 hour races a weekend on less than 1L of gear oil. Never once a failure, and went crazy long before a rebuild was required. All we would do is change the fluid after each race weekend.
This isn't a "it's better" or "faster" exercise, I'm just saying there are other high-level options out there, and options aren't bad.
Appreciate all your input here on the suspension and LSD options. Totally agree, forums just like insta get their favorites and then you lose sight of the other great options out there. I remember diffsonline! I stopped by their shop when they just started, seemed like decent guys but they were basically selling rebuilt oem diffs for premium $....
02-22-2021, 11:35 AM
Track-focused build underway - Bilstein Clubsport / OS Giken
