PSA: Turner J Stock Springs are Available Again

[moatilliatta]

J stock valving is 300/175 F and 200/125 R, And the set I had done matches the J stock valve curve strait from Bilstein.

All this effort went into this because how compliant this setup is and surprisingly nice on the street. Anyone on full Group N setup that has driven J stock always says the J stock is better on Race Track or Street.

[nogapersnBMWs]

All this effort went into this because how compliant this setup is and surprisingly nice on the street. Anyone on full Group N setup that has driven J stock always says the J stock is better on Race Track or Street.

110% agreed J-Stock suspension is "surprisingly nice on the street". These tuners also agree:

https://s14net.vbulletin.net/forum/s...ck-meets-grp-n

Some tuners, even ones on this forum have proclaimed--without ever owning or riding in an E30 so equipped (so funny)--that J-Stock springs are "progressive" or dual spring and thus of an outdated design that also lacks initial turn-in especially at track until the stiffer spring is loaded-up (off the softer spring that becomes fully compressed), but IMHO it's the softer spring that allow for great street ride. Most E30 M3 owners who have this suspension agree it should have came from the factory with J-Stock suspension (Version 2 with super stiff H&R springs, not soft like Eibach's in Version 1).

[Digitalwave]

J-Stocks at full tilt are the same rate as the low end Group N linear rates (dry tarmac spec), or at least they are very close. The J-Stocks are approx. 680lb/in front and 1026lb/in rear, but of course it's apples to oranges comparing progressive and linear spring rates. J-Stocks ride softer than Group N because they are progressive springs, and the dampers have softer compression valving.

IMO the major downside with any full length E30 front strut setup is the lack of bump travel. Group N strut tubes are about 2" shorter, the Motorsport inserts are much shorter, and they don't have the ridiculous 4" internal bump stops like most OTS Bilsteins have (but that is easy to remedy).

[ForcedFirebird]

Anyone have the Bilstein b8 specs for the f-bodies? I stuck a pair in the back of the car and they feel great with the rest of the j-stock. Stock sway bars and the car handles like coils for the most part EXCEPT when riding the curbs/gatorbacks - that's when these shine. The progressive rate allows some travel while getting planted, and the weight is shifted. Tested with a 'vert sway bar and the car pushed a little, so if upgrading stock sways, I would suggest keeping the stock F/R ratios for a balanced feel.

[amcp]

Would the Jstock springs and e30 revalved Koni SAs be a better choice over Koni OTS valving and the GC kit?
This it for a mostly weekend, track car.

[moatilliatta]

Best would be having a damper that is matched. I'm sure GC or TC Kline has done enough kits to be able to valve a koni to match the Jstock springs.

A post I found
https://www.r3vlimited.com/board/for...gc-konis/page2

[amcp]

Agreed. Just need some feedback on which is the better direction

[Digitalwave]

OTS Konis are likely going to be underdamped for any spring rates this high, whether progressive or linear.

[Northern]

Given that they're progressive, the 680/1026 would be the rate at the top of the ramp?
I'm just guessing this because if it were the lower end or even the average, they would be stiffer than hell?

I imagine something like a Koni 8610 1437Race up front, could be enough once it is turned up? Rates aren't published, but someone tested them here: https://wilhelmraceworks.com/koni-shock-dynos edit: Calculators at the bottom

paired with Koni 30-7436 and a rear spherical RSM adapter from GC. (also a few other shock variants in this size, and unlike the fronts, they have an xls with damping rates: https://www.koni-na.com/en-US/NorthA...essories/Oval/ )


Interesting setup: http://www.e30performance.info/viewtopic.php?t=2378

[nogapersnBMWs]

I imagine something like a Koni 8610 1437Race up front, could be enough once it is turned up?

Koni paired me up with the 8610-1437RACE for use with IE3 or H&R Race which are 50% the rate of J-Stocks using a 3" aluminum spacer as shocks are shorter than stock made for lowering springs.

[nogapersnBMWs]

OTS Konis are likely going to be underdamped for any spring rates this high, whether progressive or linear.

Agreed

[Northern]

People run iX konis up to 450lb/in on linear springs, I think 1437Race were overkill for H&R Race.
I run them for 450lb linear springs and they feel great, I think ~1/2 turn from full soft

[nogapersnBMWs]

Best would be having a damper that is matched.

IMO with non-adjustable Bilsteins (Konis dif) this could be difficult based on: 1) weight of car (my E30 weighs 2340 v stock 2800 lbs); 2) aerodynamic downforce

For example, my non-M3 E30 uses an E30 M3 EVO 3 "venturi" undertray (51112233041) and EVO 3 three-way splitter (51112233040) in addition to a double decker diffuser with a 12 square foot (3x4') horizontal wing (which adjustable angle relative to rear undertray and/or ground) which provides significant downforce requiring different suspension requirements than stock.

[ForcedFirebird]

Would the Jstock springs and e30 revalved Koni SAs be a better choice over Koni OTS valving and the GC kit?
This it for a mostly weekend, track car.

My take. Pinch some salt, and throw it in the air for posterity.

Last weekend, I was able to make a super clean/fast pass on an e36 t3 at RA, car bumped in the air, even, with the j-stock and the aforementioned f-body b8 sport rear replacements (fast lap was 1:46 on 225/45 Rival, 200tw streets, spec-legal 155whp m20, 2600lb wet/190lb driver).

I started my HPDE experience with GC and the typical 450/600 setup, using up scrub RA1's since that was the Spec tire in the day. Built a SE30, and immediately realized you could get the rear corner to completely bottom out before gaining traction - the rear b8 and H&R is way too soft, hence the larger sways se30 gravitates towards.

Stuck a set of Koni adjustable in the car for an event (illegal: we are a top 10 if we are lucky after 14hr with 100 entrants lol). Koni lasted about 12hr at RA, mid 40's all day, I started a night-time stint and the car wouldn't get to apex at t7, you can tuck an e30 in tight there and "slow in fast out". Lap times dropped almost 8sec.

So far, I really like this setup. We were able to exchange the points in large sway bars for a coil-like feel, yet get the bumps/gator jumps of the se30 suspension lively hood. Spec Miata can't ride curbs like we can, giving an advantage on a bumpy track. Pair that with a strong m20 and these cars are a BLAST to race. :)

[nogapersnBMWs]

Best would be having a damper that is matched

It would appear from the original sales ad from TMS that the J-Stock dampers and springs are already somewhat "matched" being that the Bilstein's are "completely reengineered for stiffness and rate, as well as travel"

https://www.turnermotorsport.com/p-4...ger-available/

The Bilstein box that the front struts came in also says "custom valving" which to me implies some spring matching (in other words what else would the custom valving be primarily matched to (besides anticipated weight loads?))