Clutch Masters hydro bearing failure!

I spun the bearing, but just a small spin to see if it moved. It spun freely and smooth. I left it at that due to the damage on the piston.

 

Yeah, exactly. I’m sure the bearing itself is fine, but it’s spinning the hub for sure, which shouldn’t be happening, at all.

Jeff

 

Man I'm kinda happy I'm auto lol

 

It's a labour of love.

The SC auto guys have their own issues with shift tuning in the ecu and a trans upgrade kit that installs some springs and stuff to firm up shifts

 

Out of curiosity, I picked a somewhat reasonable angular contact bearing from SKF that is approximately similar in size to the release bearing, which has a dynamic load capacity of about 2500 lbs.

L₁₀ bearing life (number of hours 90% of bearings will reach before failing) can be found as,

L₁₀ = [(C ÷ P)ᵉ × 10⁶]/(60 × N)

Where C is the dynamic load capacity for the bearing, P is the applied load, e varies by bearing type (3 for ball bearings), and N is the speed (in RPM).

If we're talking about bearing life just from spinning while the clutch isn't being used, in most applications it is simply the force of the spring compressed under the piston of the slave cylinder, reduced by the release fork movement ratio (probably about 2 or 3:1), which is pretty small, but for good measure let's err on the cautious side and say that there is a force of maybe 50 lbs pressing the release bearing against the pressure plate fingers. Let's then also say that the engine is constantly running at 4000 rpm, which is pretty high. L₁₀ is then,

L₁₀ = [(2500 ÷ 50)³ × 10⁶]/(60 × 4000) = 520,833 hours

Now of course, you're not usually just sitting in a parking lot revving the engine to 4000 rpm while stopped, but let's say worst case, you're just driving around a school for the entire life of your truck at 20 mph, you'd be able to do that for about 10.5 million miles before that bearing failed.

In doing this calculation, I also contemplated bearing failure criteria related to underloading and acceleration. That is, for many typical bearings, you want about 2% of the dynamic load capacity applied to the bearing at minimum to avoid skipping (when the bearing races spin without the bearings themselves rolling), and also that you want the bearings to start rolling as the races accelerate. This is one of a few reasons bearings are preloaded in general. A bearing that is constantly running under a light load will typically have a longer service life than a bearing that is accelerated from a stopped/no load condition. That brief period of time when the bearing is accelerated from a stop as it starts to have load applied will cause increased wear to both races, and the contact surfaces where the load is being applied (in this case, the pressure plate fingers and the release bearing contact surface). This is likely why, at least from my experience, pressure plate finger wear isn't as prominent on modern clutches compared to older designs that required adjustment and/or used a spring to pull the bearing off of the pressure plate. In fact, this small shock loading may also be contributing to the seal failure of the CM unit if it is not in constant contact with the pressure plate, as the initial shock load may be enough to get the hub to slip on the seal just a bit every time you use the clutch.

That said, I would expect the preload force on constantly spinning release bearings to fall below the 2% recommendation, and is likely carefully considered when designing a clutch release setup.

In conclusion, I don't like Clutchmaster's release bearing design. If I was designing one, it would have a preload spring under the hub to maintain contact with the pressure plate, and it would have a slide channel or peg on the hub to prevent rotation against the seal. I would also have a dust deflector covering the sealing surface to prevent debris from damaging the seal.

Jeff

 

Today I took the CM unit off the trans wiped it down to take some measurements. There is about .3mm of difference between the piston and the housing. It was consistent from the outside of the piston and the inside of the piston. I'm not an engineer, but I say .3mm is way too much for this application. I think .1mm on the inside and outside of the piston would be plenty.
Enjoy.

 

Using ISO limits for a free-running fit (e.g., H9/d10), the ID should have a clearance of approx. 0.080 to 0.242 mm and the OD should have a clearance of approx. 0.100 to 0.294 mm. You could certainly run a tighter fit, but I wouldn't say these measurements are particularly unusual given the size, that there are rubber seals holding them in place, and that it will also provide axial clearance to allow bearing misalignment.

Also not sure if you were able to measure past the wear to see what the initial measurements were vs. the worn, but that might have been slightly tighter as well.

Jeff

 

Maybe the seal had swollen, but there was no way that the seal was fitting between the piston and the housing. The way it looked "after failure" was more the seal looked like the "piston" and the piston was moved by the seal.
Not sure if that makes an sense.
The seal took up the whole space in the housing. I had to use compressed air to remove the seal from the housing.

 

Still holding strong 10k in

 

Of course they don't. How many makes/models do they make products for? Many.
Are they going to have a guy sit on a computer all day to watch every forum?
No.

Same here. Hopefully it keeps going. Quieter than stock and feels better than stock.

I actually accidentally took mine apart before installing, out of curiosity to get an idea of how it works. Then put it back together. It seemed free moving.
And also bled the shit out of fluid after install to make sure no air bubbles. Not sure if that all made any difference.

I'm not sure why German cars had the design figured out for over 20 years and Toyota couldn't. And what makes them different.
Take any German car and you've probably got a replaceable $30 sleeve the bearing rides on that bolts to the bell housing. The bearing may or may not apply at an angle. But either way when those people do clutch jobs, it's usually not the bearing that goes. But they replace at the same time because while in there, and the cheap cost of the part.

 

Toyota also had it figured out 30+ years ago. Not sure whose idea it was to change it. There is always a risk associated with changing a design that works, Toyota knows this.

Jeff

 

Yeah I just took a lot of time getting mine bled and installed… feels great still other than a first clutch press after driving awhile

 

Someone justifying their pay check.

 

I would suspect this issue is likely a result of not having a spring to either hold the release bearing against the pressure plate or away from the pressure plate, resulting in variations in the required piston travel.

Now that I’ve potentially got a bit more time coming up, I’ve been thinking of potential solutions again. Might design something.

Jeff

 

This is really disappointing, I was looking at this kit closely. My truck is getting worse noises from this bearing, started chirping at around 60k, but it seems like all of the fixes just solve it for a couple thousand miles and then you're back to square one and one step closer to an entire transmission replacement. I have neither the skill nor the lift facilities to be dropping my transmission every 50-60k for a bearing.

 

I've got about 7k miles on my clutchmasters hydro bearing kit with URD Stage II clutch/pressure plate. I don't have a chirping, but I do get an occasional noise from the transmission rotation when the clutch is not engaged...basically the opposite of when a stock setup gets the chirping.
I haven't had any other issues with the hydro bearing yet though. I thought something was messed up for a couple weeks because I couldn't press the clutch pedal far enough to disengage the clutch and get the vehicle in gear....turns out the spring inside my master cylinder broke into 3 pieces and was causing my pedal to drop to the floor. Replaced master clutch cylinder and I haven't had ANY issues with saggy pedal.

 

I’m over 10k on mine

 

I think some people just got unlucky, perhaps due to the QA/QC setup at clutchmasters since they are not a big company like Toyota. I'm at about 700 miles on imne and no issues thus far.

 

I'm glad to hear that there are people that are not having issues with these.

 

I have about 25k on my clutchmasters bearing, it only likes to leak when I slip the clutch a lot so I guess its been holding to some extent. However, I am not too thrilled about its "hit-or-miss" performance, so I will be ditching this hopefully soon with a Tilton setup.

I would recommend to anyone with this bearing who has made it this far and has not had the bearing crap out on them, to periodically flush the brake fluid from the cm setup as I've noticed clutch dust/ect can get past that seal rather easy. Flushed mine a couple weeks ago and that fluid in the cm hydrobearing was pitch black.