XTreme clutches - sprung vs cushioned? - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

lapsio · 09-16-2022, 08:16 PM

Hi

I recently ran out of clutch in my BRZ after 6 months of ownership (yea well... I also ran out of 3 rear tires sets so it may be somehow related). Anyhow, car is still on warranty so I'm still servicing it at Subaru. I asked them about STI clutch and guys at subaru told me it's plain scam tbh and if they were to be completely honest they'd much rather recommend me getting Stage 2 Xtreme clutch for my type of driving and said that they'll be more than happy to install it instead as part of next service interval so that I shouldn't have any warranty issues etc.

So I googled a bit and indeed those clutches seem to be available here and I narrowed down my choice to 3 options. Mostly those two:
KSU23512-1B and KSU23512-1C

Both are Stage 2 with the same components but one is cushioned ceramic and another one is sprung ceramic. What's difference? Also should I get one with flywheel or one without? Price difference between KSU23012-1B (without flywheel) seems to be like 250$ so not much.

colinshark · 09-16-2022, 08:50 PM

KSU23512-1B is a puck clutch, and regardless of the center springs, it will feel like an on/off switch.

KSU23512-1C has a full face, so it MIGHT have the critical marcel spring (flat spring between the friction surfaces) to provide progressive engagement.

https://motoiq.com/clutch-technology...-construction/

lapsio · 09-17-2022, 01:50 PM

Quote:

Originally Posted by colinshark

KSU23512-1B is a puck clutch, and regardless of the center springs, it will feel like an on/off switch.

KSU23512-1C has a full face, so it MIGHT have the critical marcel spring (flat spring between the friction surfaces) to provide progressive engagement.

https://motoiq.com/clutch-technology...-construction/

I guess I'll get 1B then since I'd really like to try out that on/off feel. That said - does such kit require some supporting mods? My car is overall stock apart from Cup 2 tires and standard PP. Are stock drivetrain and gearbox going to be okay with such clutch and grippier tires or should I consider getting some other supporting mods in order to prevent accidental drivetrain damage?

WNDSRFR · 09-17-2022, 03:23 PM

Good luck with that on/off feel.
Hope there's not much traffic there.

09-16-2022, 08:16 PM	#1
lapsio Member Join Date: Mar 2021 Drives: 2020 BRZ Final Edition, 1999 MX5 NB Location: Poland Posts: 90 Thanks: 41 Thanked 31 Times in 18 Posts Mentioned: 4 Post(s) Tagged: 0 Thread(s)	XTreme clutches - sprung vs cushioned? Hi I recently ran out of clutch in my BRZ after 6 months of ownership (yea well... I also ran out of 3 rear tires sets so it may be somehow related). Anyhow, car is still on warranty so I'm still servicing it at Subaru. I asked them about STI clutch and guys at subaru told me it's plain scam tbh and if they were to be completely honest they'd much rather recommend me getting Stage 2 Xtreme clutch for my type of driving and said that they'll be more than happy to install it instead as part of next service interval so that I shouldn't have any warranty issues etc. So I googled a bit and indeed those clutches seem to be available here and I narrowed down my choice to 3 options. Mostly those two: KSU23512-1B and KSU23512-1C Both are Stage 2 with the same components but one is cushioned ceramic and another one is sprung ceramic. What's difference? Also should I get one with flywheel or one without? Price difference between KSU23012-1B (without flywheel) seems to be like 250$ so not much. Last edited by lapsio; 09-16-2022 at 08:30 PM.

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09-16-2022, 08:50 PM	#2
colinshark Member Join Date: Mar 2011 Drives: Some RX-7s Location: Michigan Posts: 13 Thanks: 0 Thanked 12 Times in 4 Posts Mentioned: 0 Post(s) Tagged: 0 Thread(s)	KSU23512-1B is a puck clutch, and regardless of the center springs, it will feel like an on/off switch. KSU23512-1C has a full face, so it MIGHT have the critical marcel spring (flat spring between the friction surfaces) to provide progressive engagement. https://motoiq.com/clutch-technology...-construction/

09-17-2022, 03:23 PM	#4
WNDSRFR Senior Member Join Date: Jan 2014 Drives: FR-S,GTI Location: Cocoa, Florida Posts: 1,189 Thanks: 235 Thanked 868 Times in 442 Posts Mentioned: 13 Post(s) Tagged: 0 Thread(s)	Good luck with that on/off feel. Hope there's not much traffic there.

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