OSGIKEN STR2CD 'wear'

[Torques]

I had this clutch (STR2CD ) in my GTST for about 8 years.

I did about 8,000km on it, 30% city traffic, the rest 4th/5th gear on the motorway.

Clutch was never abused .. no burnouts, daily commute etc.

Long story short:

Clutch started to slip in 4th+ gear at 3800rpm coming onto boost (18PSI)

Checked the slave cylinder, and (the plunger) sits tight with no play.

I had trouble getting the slave cylinder bolted on again, it's about 2mm 'off'

So I presume this is down to wear. I don't know how much play the plunger/fork had at installation though.

Clutch was installed brand new, with the supplied bearing carrier/sleeve. (16mm)

 

I don't want to pull the box atm and was thinking shortening the plunger by 2mm .. clutch should still disengage I reckon.

Thoughts on this? Would that be an option?

 

 

 

 

 

 

 

 

 

 

 

 

 

[robbo_rb180]

Check the adjustment of the clutch pedal under the dash first to make sure the master cylinder isn't being preloaded. It may have been adjusted in the past for a worn clutch and now readjusted when new one was installed. 

[PLYNX]

Have you checked the clutch pedal box isn't broken ?

They are notorious for the spot welds cracking and the box then flexing all over the shop.

You'll have to flip upside down in the foot well with a bright torch and get some one to press the clutch to see it.

[BK]

As @robbo_rb180 mentioned above check your pedal box integrity and adjustment against master. You should never actually need to adjust your pedal height if done correctly in the first place though. This is normally set when a new clutch goes in and actually should be pretty low before any fork movement happens.

The theory behind this is as your clutch wears your pedal becomes higher with also less free travel, indicating plate wear. The problem is most people adjust their clutch pedal to be too high when a new clutch goes in, thinking it's too low to the floor when it really isn't. If you do this so you start with a higher pedal you run out of adjustment when it starts to wear, which ends up preloading the pressure plate fingers, causing a slipping clutch as it is ever so slightly disengaged. 

So have you got a high clutch pedal with no free travel ? Did you ever have pedal free travel ? If so you could try to adjust it do the pedal becomes higher until you get some sort of free travel, unless you got the wrong carrier in there, which I suspect you do as you mentioned a 16mm carrier.

Is this a 32 or 33 gtst ? And is it definitely a dampened STR2CD clutch ? Because I just checked and the OS giken STR2CD correct release bearing carrier from OS giken specs is 18mm for R32 and 14mm for the R33.

I think your box is coming out mate.

 

[Torques]

7 hours ago, BK said:

As @robbo_rb180 mentioned above check your pedal box integrity and adjustment against master. You should never actually need to adjust your pedal height if done correctly in the first place though. This is normally set when a new clutch goes in and actually should be pretty low before any fork movement happens.

The theory behind this is as your clutch wears your pedal becomes higher with also less free travel, indicating plate wear. The problem is most people adjust their clutch pedal to be too high when a new clutch goes in, thinking it's too low to the floor when it really isn't. If you do this so you start with a higher pedal you run out of adjustment when it starts to wear, which ends up preloading the pressure plate fingers, causing a slipping clutch as it is ever so slightly disengaged. 

So have you got a high clutch pedal with no free travel ? Did you ever have pedal free travel ? If so you could try to adjust it do the pedal becomes higher until you get some sort of free travel, unless you got the wrong carrier in there, which I suspect you do as you mentioned a 16mm carrier.

Is this a 32 or 33 gtst ? And is it definitely a dampened STR2CD clutch ? Because I just checked and the OS giken STR2CD correct release bearing carrier from OS giken specs is 18mm for R32 and 14mm for the R33.

I think your box is coming out mate.

 

You're correct, I got this wrong from my other clutch document (TR2CD), it's 18mm, not 16mm.

It's an R33 GTST, I couldn't re-edit my post to put this in.

Good points, I'll check the pedal height and check if there is any pre-load on the master.

Attached a picture of the slave, not sure if it can retract any further?

Cheers!

 

[Torques]

All -> cheers for the help,

While at it would you know if the actual release bearing is OS-Giken only, or would the OEM fit as well?

 

 

[BK]

Yeah slave looks pretty maxed out. The release bearing itself is just an OEM one. So are the bearing release carriers, which come in 2mm increments from 8mm - 32mm.

So what is actually in your car, an 18mm ?

Read my info again. R33 gtst with this clutch is supposed to be a 14mm carrier, which is actually the standard R32 GTR push bearing carrier.

Where are you getting your info from ? Because a TR2CD for a 33 gtst is supposed to be 12mm, NOT 16mm. 16mm for TR2CD again is for a 32 gtst. Seems like you've maybe have been buying 32 gtst clutches mate, as your information is incorrect for your car and you've twice now quoted R32 gtst carrier sizes for the clutches mentioned.

I know I am correct, as what I have noticed in OS giken specs is the R33 GTSt seems to follow all of the same carrier sizes as the R32 GTR push boxes, I guess because the 33 big box is so similar. They are actually the same as a GTR around the bell housing area, input shaft, counter shaft and main shaft gears.

If you do indeed have an 18mm and it's supposed to have a 14mm, you've pretty much prematurely worn out your clutch and would exactly cause this problems you've described, as your release bearing is 4mm further forward towards the pressure plate fingers than they should be. Basically like driving around with your foot resting on the clutch all the time - not good.

 

[Torques]

Thanks for the input, I got the info from OSGiken. I did not measure the actual sleeve when it had been installed (which I should have).

All I can say is that the clutch came with the spec'd carrier / bearing. I don't see my clutch in the attached page though, do you have another document?

 

Cheers

 

 

 

 

 

 

 

 

 

[BK]

😂 That is from their english OS giken page, which is definitely incorrect compared to a copy I have, which I've referenced when doing GTRs. Something has been lost in translation...

The one from actually OS giken Japan says:

 

[Torques]

10 minutes ago, BK said:

😂 That is from their english OS giken page, which is definitely incorrect compared to a copy I have, which I've referenced when doing GTRs. Something has been lost in translation...

The one from actually OS giken Japan says:

 

Cheers for that!  Yes, my document / info is from the US support!

When the clutch was installed many years ago I didn't do the due diligence. I ordered the whole kit from Japan, so I assumed it will be ok. I also didn't check how much free play there was at the fork etc. since it wasn't installed by me but my mechanic. If it was already 'tight' back then it would explain my current issue.

 

While at it, back then I also bought this Nismo slave ... it wouldn't retract further, would it? I think it's just a bigger cylinder for heavier clutches (?)

I never installed it since the twin clutch was easy to operate.

 

 

 

[BK]

Might as well sell that.

Under no circumstances use a Nismo big bore push slave. They make the clutch lighter, but they DO NOT provide enough travel for multiplate clutches, and are actually recommended from Nismo themselves only to be used with single plates in the notes. They are right, they provide less travel.

I've tried one with an R3C on GTR with a 26mm carrier. After a bit of use the clutch wouldn't disengage properly because of the reduced travel, very noticeable. Bit different with the STR as they are a pretty soft clutch for a twin plate. They are really only designed to be silent and have a light clutch pedal. Not really the sort of clutch for any serious power that's for sure with such a light pressure plate.

But because of the less travel it might actually retract further, and provide some freeplay.

Might.

But if you've got the wrong carrier that really doesn't change the fundamental error of the clutch release fork to bearing carrier height, it's going to throw your travel amount off.

[Torques]

I checked the pedal travel, and it needs about .8 - 10mm until it rests on the master rod/actuator.

Then another 5 to 7mm till there is resistance and the clutch starts to operate.

I'm not under the impression that there is any 'load' on the clutch master while the pedal is resting / clutch disengaged.

I didn't unbolt anything, so that's just my observation from operating the pedal by hand and having a close look / feel.

 

 

 

[BK]

I think it's time to pull the box out, remove your clutch and inspect the setup. The clutch has obviously worn raising the front cover fingers, making them push against the release fork, therefore pushing your slave piston in. It could be slightly disengaging the clutch without you realising it by feel.

The question will be is it because of an incorrect bearing carrier length being too long, causing premature wear in the plates. Or everything is infact correct, and it's just worn out from light use because the STR2CD is a shit clutch (which they are from a performance point of view).

There's a reason there is no OS giken GTR recommendation to fit a STR2CD behind an RB26 GTR, because they handle very low torque and is barely an upgrade over a stocker as far as torque loading goes.

[Torques]

10 hours ago, BK said:

I think it's time to pull the box out, remove your clutch and inspect the setup. The clutch has obviously worn raising the front cover fingers, making them push against the release fork, therefore pushing your slave piston in. It could be slightly disengaging the clutch without you realising it by feel.

The question will be is it because of an incorrect bearing carrier length being too long, causing premature wear in the plates. Or everything is infact correct, and it's just worn out from light use because the STR2CD is a shit clutch (which they are from a performance point of view).

There's a reason there is no OS giken GTR recommendation to fit a STR2CD behind an RB26 GTR, because they handle very low torque and is barely an upgrade over a stocker as far as torque loading goes.

 

Cheers, yes ...  it's time to possibly rethink my choice of clutch while at it .. I think it's just worn.

Which clutch would you recommend? 300KW ish setup? Must be 'OK' to be used in traffic.

As for STR2CD, OSG wouldn't give me any torque figures, just HP (450-500).

I found that a bit funny ..

For example you could make 450HP @

8,000 rpm and 295 lbs ft

Or

4,000 rpm and 591 lbs ft

 

 

 

Edited December 17, 2020 by Torques

[robbo_rb180]

I have used exedy in past but have moved to npc for the last few clutches as they are a lot nicer for daily driving. Some others I know have tried mantic on a few different platforms with good results with holding big power and still nice for daily driving.

[GTSBoy]

11 hours ago, Torques said:

I found that a bit funny ..

While that's true in general - on a particular engine, retaining the same mode of induction (ie turbo(s)), then the relationship between torque revs and power remains fairly constant. More power = more torque at about the same rpm.

[Torques]

On 12/17/2020 at 9:31 PM, GTSBoy said:

While that's true in general - on a particular engine, retaining the same mode of induction (ie turbo(s)), then the relationship between torque revs and power remains fairly constant. More power = more torque at about the same rpm.

That depends, often the torque curve shifts upwards when modifying an engine (especially with bigger turbos). Thus making more power @ higher rpm.

All things being equal it would be nice to have a torque figure for a clutch.

 

 

[Torques]

So update on my initial problem.

I found a push-pin that is about 1.5 mm shorter. (Ideally 2.5mm would do the trick)

I'll see if that fixes the issue for the time being. There's still no play at the fork but no pressure either.

I could mount the slave without any problems, but it sits tight.

 

In a couple of days I'll test if the clutch is still slipping...

I'll pull the box at a later point ...

 

Edited December 20, 2020 by Torques

[GTSBoy]

4 minutes ago, Torques said:

That depends, often the torque curve shifts upwards when modifying an engine (especially with bigger turbos). Thus making more power @ higher rpm.

No, I think you miss the point of what I said. It's the same engine. The clutch manufacturer knows what engine they're making the clutch for. They therefore know the likley characteristic rev/torque/power characteristic of the engine. A stock engine will to X torque at Y rpm and make Z power out of it. Make mods to it so that X increases and Y changes and you get a different Z.....and the clutch manufacturer can still choose to rate that clutch at the new Z number because it is likely tied very closely to the new value of X.

They're not talking about "here's a clutch from a 20L diesel engine that can handle 300HP and 3000ft-lb, it is therefore rated to 300HP on a Honda K20. Because that woudl be silly. The opposite would also be silly with the K20 clucth on the diesel. But if they say, here's a stock clutch for an RB25 and it can handle ~350 HP, and here's a better clutch for an RB25 and it can handle 700HP, then there's a really fair bet that the better one can handle about double the torque.

[Torques]

This is an older post of mine but I just thought I should update it and explain what the problem was.

Long story short the friction plates were below their service limit.

New they are around 4mm, and service limit is (according to OSG) 3.5mm

In addition the crank seal gasket wasn't sealing 100% anymore and that led to an oily clutch.

Not sure what came first and why the clutch was worn after just 10,000km .. but all good now.

OSG refresh kit via Nengun

 

 

 

 

 

 

Edited September 9, 2024 by Torques