Wear and tear on throwout bearing

[FRSstyle]

What causes the wear and tear on the throwout bearing? Is it the continuous compression/decompression, or is it the continuous pressure of holding the clutch away from the flywheel?

If you look at regular springs. If you keep a spring round up, there will be no wear and tear. It is the continuous compression/decompression that wears it out.

Sometimes I'll roll up to a stop sign/traffic light and know that I will have to move again in 4-5 seconds. So I can either:

1. Push the clutch pedal, move to neutral, release clutch pedal, and then in 4-5 seconds push the clutch pedal and then go off into first.

2. Or push the clutch pedal and keep it depressed 4-5 seconds until I move off.

If the throwout bearing wears like a spring, option 1 puts more wear and tear.

[theholycow]

Springs "wear" from compression and decompression via metal fatigue. It's not actually wear; material is not worn off.

The throwout (release) bearing is not a spring. It's a bunch of bearings (ball bearings or needle bearings or whatever) in between a pair of cylinders used as sleeves. The bearings are constantly spinning and wearing. When more pressure is put on them while they are spinning, their wear increases.

If you're going to be stopped for 4 or 5 seconds, you'd be nuts to do a bunch of clutch work. You'd wear out your leg and your shoe. Just sit there with the clutch pedal floored. If you do everything right you'll save more wear on the much more expensive and difficult synchronizers than you will on the cheap and relatively easy release bearing.

Most importantly, though, don't be neurotic! This stuff is designed to be used, just go ahead and use it. Forget the technical explanation above.

Here is a photo of my release bearing (incorrectly aligned in this fork, just FYI). I did not find a cutaway in google so I figured I could at least post my own photo of one.

[FRSstyle]

how would i be saving my synchros?

to be more clear, I'll come rolling to a stop in a higher gear and then 3-4 meters before stopping, push in clutch and then proceed to either my scenario 1 or 2 above. either way, the synchro in first needs to do work.

another way to phrase my question. what wears out the throwout bearing more? pushing in the clutch pedal for 5 seconds and releasing, or pushing in the clutch pedal twice for a second at a time?

my clutch pedal is light, so I can do either 1 or 2. doesn't matter.

[theholycow]

how would i be saving my synchros?

to be more clear, I'll come rolling to a stop in a higher gear and then 3-4 meters before stopping, push in clutch and then proceed to either my scenario 1 or 2 above. either way, the synchro in first needs to do work.

I bet that 3-4 meters before stopping, at idle RPM, you are perfectly double-clutched for 1st and barely use the synchro at all.

On the other hand, if you're at a stop and put it in neutral and then step on the clutch and put it in first, you use that synchro in its normal way, contributing its normal wear. You'd be nuts to worry about it, but you were already asking about something equally neurotic anyway so I figured I'd give you the whole story.

another way to phrase my question. what wears out the throwout bearing more? pushing in the clutch pedal for 5 seconds and releasing, or pushing in the clutch pedal twice for a second at a time?

Holding it for 5 seconds wears it more than pressing twice for a second at a time, but it is completely ridiculous to worry about 5 seconds. If we were talking about 150 seconds repeatedly all day then you might want to think about neutral for the bearing's sake.

The movement of engaging/disengaging does not affect wear. Fully disengaged, it is under the most pressure and gets the most wear while sitting there fully disengaged (more so if RPM is higher). Fully engaged, most of the pressure is off (not all, because there is a little bit of preload) and it gets the least wear.

Again, and I can't stress this enough, worrying about 5 seconds of wear on that bearing is incredibly neurotic and counterproductive. You are willing to put more wear on the rest of the clutch release system and on the synchros, just to save a cheap wear part whose job is to do exactly what you're trying not to make it do. You can't wash one hand without getting the other dirty, I think is Rope-Pusher's saying. You're flexing the clutch cover assembly's springs (which are fatiguing but not wearing, like any other spring) and the compression spring in the clutch disc and any brackets involved, there's bound to be some flex in the pedal and (if equipped) fork, you're wearing the ball stud (if equipped) and quill and input shaft and clutch hub, you're wearing the seals on the clutch master cylinder, you're shearing and wearing the fluid, ad nauseum. The extra shifts are wearing the synchronizers, shifter pivot, shifter cables/housings/ferrules, the entire transmission, and a bunch of other things I forgot. Have I given you a heart attack yet?

[FRSstyle]

I bet that 3-4 meters before stopping, at idle RPM, you are perfectly double-clutched for 1st and barely use the synchro at all.

On the other hand, if you're at a stop and put it in neutral and then step on the clutch and put it in first, you use that synchro in its normal way, contributing its normal wear. You'd be nuts to worry about it, but you were already asking about something equally neurotic anyway so I figured I'd give you the whole story.

what do you mean perfectly double clutched? double clutching is putting it into neutral and then stepping on clutch again for first.

Holding it for 5 seconds wears it more than pressing twice for a second at a time, but it is completely ridiculous to worry about 5 seconds. If we were talking about 150 seconds repeatedly all day then you might want to think about neutral for the bearing's sake.

The movement of engaging/disengaging does not affect wear. Fully disengaged, it is under the most pressure and gets the most wear while sitting there fully disengaged (more so if RPM is higher). Fully engaged, most of the pressure is off (not all, because there is a little bit of preload) and it gets the least wear.

Again, and I can't stress this enough, worrying about 5 seconds of wear on that bearing is incredibly neurotic and counterproductive. You are willing to put more wear on the rest of the clutch release system and on the synchros, just to save a cheap wear part whose job is to do exactly what you're trying not to make it do. You can't wash one hand without getting the other dirty, I think is Rope-Pusher's saying. You're flexing the clutch cover assembly's springs (which are fatiguing but not wearing, like any other spring) and the compression spring in the clutch disc and any brackets involved, there's bound to be some flex in the pedal and (if equipped) fork, you're wearing the ball stud (if equipped) and quill and input shaft and clutch hub, you're wearing the seals on the clutch master cylinder, you're shearing and wearing the fluid, ad nauseum. The extra shifts are wearing the synchronizers, shifter pivot, shifter cables/housings/ferrules, the entire transmission, and a bunch of other things I forgot. Have I given you a heart attack yet?

i don't see how either option 1 or 2 puts more or less strain on the synchros. either way, I'm putting the gear into first gear at idle rpms. this is about the throwout bearing.

it may be neurotic to you, but i have a light clutch pedal and can go with option 1 or 2. it doesn't matter to me, so i'll go with the one that puts less strain on the throwout bearing.

[monkeyhunk]

Sweet lord baby Jesus kill it with fire before it lays eggs.

[theholycow]

what do you mean perfectly double clutched? double clutching is putting it into neutral and then stepping on clutch again for first.

I was thinking you were already in neutral, but indeed that may not be the case.

it may be neurotic to you, but i have a light clutch pedal and can go with option 1 or 2. it doesn't matter to me, so i'll go with the one that puts less strain on the throwout bearing.

It sounds like you're going to be buying a lot of other more expensive components to avoid buying a measly throwout bearing that you're bound to throw out during your next clutch replacement anyway. Are people with your car chewing up lots of them?

Is it safe to assume from your username that your car is the FR-S? Clutch work is easy backyard work on a front engine rear wheel drive car. The throwout bearing is probably the cheapest, most easily available part in your whole drivetrain.

I urge you to think about the dozens of more expensive, more rare, more difficult to replace parts you'll prematurely wear by being paranoid about the most disposable part on your car. It would be like tripling your oil change interval to avoid wearing out the oil drain plug.

[FRSstyle]

It sounds like you're going to be buying a lot of other more expensive components to avoid buying a measly throwout bearing that you're bound to throw out during your next clutch replacement anyway.

So how will option 1 or 2 will put more strain on the other components?

Rolling to a stop in a higher gear and you:

1. Push in clutch pedal and keep depressed, stop, put gear shifter into first and then go.

2. Push in clutch pedal, move shifter to N, release clutch pedal. Push clutch pedal again, move shifter to 1 and go.

[theholycow]

In option 2, you have twice as many fatigue cycles on the the pressure plate springs, pedal, master cylinder, hydraulic line/fittings, slave cylinder, any brackets involved, and the clutch disc's springs. You're also sliding the clutch hub on the input shaft twice as much, pivoting the pressure plate springs on their mounts, and letting the flywheel/clutch/pressure plate friction surfaces wear slightly.

That's all a worthwhile investment if you're double-clutching or if you're going to be sitting at a very long red light. It's a miscalculation for a mere 4-5 seconds, especially since you're really only going to save half a second of bearing wear. The time in which you are disengaging and engaging the clutch, there is still pretty much the same amount of pressure on the bearing.

[ClutchFork]

Here is a photo of my release bearing (incorrectly aligned in this fork, just FYI). I did not find a cutaway in google so I figured I could at least post my own photo of one.

Now that is beautiful. A real live clutchfork. My last two trucks were missing the clutch fork and had these horrible concentric slave cylinders instead. The best clutch hydraulics I ever had was on my 1984 F150 because it still had a clutchfork and the slave was on the outside of the bell housing. It was a hundred times easier to service the transmission and clutch that way. I could change out the clutch and not have to bother bleeding the hydraulics because you really didn't go into them. And if the slave were to go bad it was a piece of cake to get to.

By the way, if you could change your username on this site, I would have become ClutchFork months ago.

[monkeyhunk]

Make new account identify yourself as member formerly known as inline paul....unless you care about post count being senior etc

[theholycow]

Now that is beautiful. A real live clutchfork. My last two trucks were missing the clutch fork and had these horrible concentric slave cylinders instead. The best clutch hydraulics I ever had was on my 1984 F150 because it still had a clutchfork and the slave was on the outside of the bell housing. It was a hundred times easier to service the transmission and clutch that way. I could change out the clutch and not have to bother bleeding the hydraulics because you really didn't go into them. And if the slave were to go bad it was a piece of cake to get to.

By the way, if you could change your username on this site, I would have become ClutchFork months ago.

I felt the same way about the concentric slave, but recently I've re-thought it. While a concentric slave makes slave replacement go from a few minute easy job to a major undertaking, it's also a much simpler, more direct system (which is, shall we say, in line with your values) and it's more durable.

I would like longtube headers (never gonna have them, at least not on this engine) and I've wondered how I would ever make that happen with my fork/slave/bracket in the way, then I realized that a concentric slave would solve that problem. It would also make my improvised fork boot better, I could just use a piece of stiff plastic or sheet metal instead of sheet EPDM rubber with a big forkhole in it. (Of course I could just invest $10 in a proper one and keep my fork.) Also, it would prevent the slave from having to be so friendly with my exhaust manifold, and my slave bracket might be partially at fault for a brake line failure I had (flexing car and drivetrain in an extreme avoidance maneuver might have pushed the bracket into the line).

You might be able to get your username changed, have you asked?

[Rope-Pusher]

You can't wash one hand without getting the other dirty, I think is Rope-Pusher's saying.

Fickset

[Rope-Pusher]

You can't wash your hands without getting the sink dirty, I think is Rope-Pusher's saying.

Fickset

[theholycow]