Lifespan of a clutch? - Sportbike Forum: Sportbike Motorcycle Forums
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post #1 of 13 (permalink) Old 09-21-2007, 09:16 PM Thread Starter
 
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Lifespan of a clutch?

A few clutch questions today...

So what wears one down? How long do they typically last? What are some things you should/shouldn't do?
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post #2 of 13 (permalink) Old 09-22-2007, 01:25 AM
 
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Proper usage and maintenance, they can last anywhere from 20,000 to 50,000+. Depends on what bike we are talking about.

Clutch less shifting wears it down, specially from high to low. Popping the clutch to do wheelies or drag launches. Doing a burnout and not fully engaging the clutch (feathering it is bad). Fast accelerations can reduce the life a bit. Keep up with changing your oil and use motorcycle specific lubricants as they work well with the transmission and clutch.

Things I've heard:
- Not properly having the chain tighten can reduce clutch life
- Keeping the bike at high revs reduces clutch life
- The high revs may produce high heat, which then can warp the metal plates between the clutch discs.
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post #3 of 13 (permalink) Old 09-22-2007, 06:25 AM
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Clutch

My stock clutches only seem to last about 12,000-15,000 miles. Aftermarket ones (like Barnett) seem to last forever.

"Fat, drunk, and stupid is no way to go through life son." - Vernon Wormer.- Dean, Faber College.
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post #4 of 13 (permalink) Old 09-22-2007, 06:43 AM
 
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I'm going to have to disagree with jbaz and say that clutchless upshifts do nothing to wear out the clutch. Clutchless downshifts wont wear it down either, but you shouldnt do them, cause you are risking bending your shift forks for no benefit.

In its heart, a clutch is a type of a brake, only instead of engaging contact between a rotating and stationary plate it contacts two rotating ones.
Clutch damage can be seperated into two components. One is plate wear, which is kind of like wearing your brake pads. They series of plates are a wear item, designed to be replaced. What will wear them is temperature and ammount of time they are rubbing against each other (when the clutch is in the friction zone). Drag launches are brutal on the clutch, you can kill one in a day. Clutching wheelies are the next biggest cause of wear, but it isnt nearly as bad, since you arent transferring all the power the engine can make like you do in a launch. Everything else is pretty negligable, unless you are bad at doing burnouts and have to feather the clutch for a long time. Feathering is bad.
The other component of plate wear is temperature. When the clutch gets hotter it works better, but wears faster. If it overheats, it works worse and wears even faster. Most clutches are oil cooled (italian bikes and harleys are the exception), so having proper oil is critical. Having too little oil or having oil thats too far broken down will destroy your clutch along with the rest of your engine. Also, if you have a slipper clutch it will wear faster, since it automatically goes into the friction zone when you downshift, thus wearing a touch more.

The other component of clutch wear is wear on the structural parts of the clutch, mainly the basket. This is damage that isnt supposed to happen, but will if there are sharp impacts. An unevenly wore chain is a big culprit, as well as popping wheelies (power wheelies are worse than clutch ones here). Baskets arent too difficult to replace, but they are likely to be expansive. The danger here is that a basket can fail catostrophically, and send pieces of aluminum into your engine to mess up who knows what.

The third theoretical component is bearing wear (in cars its called the throw out bearing, I have no idea what the term in bikes is, but its where the actuator connects to the rotating clutch). it would be really easy to fix, and I have never seen one fail, ever. How you use the clutch shouldnt have much of an effect on how quickly this part will wear, its just a matter of operating hours. Anyways, dont worry about this.



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post #5 of 13 (permalink) Old 09-22-2007, 04:42 PM
 
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yes, but with clutchless shifting from higher gear to a lower gear may slip the rear tire. It's worse for the transmission, but it also adds more wear and tear on the clutch than normal use. That jumpiness or shakiness when you loose traction is slipping the clutch just a bit because the transmission is providing too much power and breaking the static coefficient of friction. That force of friction is also providing a large resistance to the transmission, which is then transferred back to the clutch. The clutch then slips a bit because it's the only thing in the system that will allow to "give" to the stress. The transmission is pretty much fixed in transferring energy from the engine to the wheel, or vice versa. If the transmission does give, something usually breaks or grinds. (a bad sound that you shouldn't hear is usually associated with it though)

Unless you have a slipper clutch, when you break traction from speed shifting down, it adds a lot more strain/pressure on the clutch and transmission system compared to normal use. This is really debatable because you hear people say that it's better to clutchless shift than to use the clutch when shifting gears. I'm only taking about high revs, which multiplies the forces involved and increases the wear and tear on the parts (all parts involved), and that generally involves the slip of the rear (the point of where it turns into excessive power transfer).
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post #6 of 13 (permalink) Old 09-22-2007, 05:10 PM
 
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My '00 Honda 929 had a faulty clutch (all 929 had the same so it as a factory recall) replaced in June of '01.

I was 50 miles out of town to & about to shift down from 6th as I was comming to a red stop light. Suddenly I did not have a gear change lever.

Off the bike & could see I had lost the adjusting rod. Did not have the strength to move the gear change linkage by hand as the bike stood still.

So with 6th gear I slipped the clutch & nursed the throttle to roll down in this small town with aim to turn around in a few blocks only to find myself in a narrow Municipality yard road. So made a U-Turn on this paved road smeared with gravel (though believe me I was up on the footrests like when I use to compete in Observed Trials) all in 6th gear, to the stop light & all the way home.

When passing cages I knew I only had throttle, clutch & brakes, but I made it with some of the tight bends to my home town that is built on a mountain side & my home was pretty far back.

Took the same gear change linkage adjusting rod off my Honda 954, to find it was the same) & went back on the ride up in the mountains without worry about the clutch & honestly feel the clutch will still be good some years down the road FOR the clutches on the Jpn bikes are long lasting. Far, far better then what we suffered on the Brit irons in the late 40s to sometime into the 50s.

Some refer to the '00 Honda 929 as an "old bike" so I have a lot of milage on it & it will last a goodly number of years as it is not THAT old.
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post #7 of 13 (permalink) Old 09-22-2007, 05:29 PM
 
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ok so feathering is bad. what about when you're in a parking lot and you don't need all the power transferred to the wheels so you feather the clutch to navigate through a space or whatever you need. i'm not talking 9,000 rpm feathering...merely putting around slowly.
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post #8 of 13 (permalink) Old 09-22-2007, 05:40 PM
 
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when you feather the clutch, the disk's aren't fully engaged. Think of two pieces of sandpaper and rubbing them together. That's what clutches are doing when the fly wheel transfers the power of the engine to the transmission. Low revs will wear it down, but it's very very very nominal and considered normal wear. You have to have a transitional period to transfer power some how...

Now if you left the transmission to 6th gear and feathered the clutch from 0-35mph before full engaging it, that's bad, even for low revs.
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post #9 of 13 (permalink) Old 09-22-2007, 05:45 PM
 
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aah ok thanks for clearing that up. i'm assuming the clutches in our bikes are specifically designed to allow a small amount of slipping while transfering full power to the transmission.
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post #10 of 13 (permalink) Old 09-23-2007, 01:21 PM
 
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Still the clutch has to be feathered or slipped, or whatever, for a bit for it is is not pull in a bit & let go with a big thud.

Read my bit about having to travel back out of the town of Peachland to my town & actual resident some distance back & higher up in Summerland & did it all in 6th gear, but the damage to the clutch was very little due to past 61 yrs or riding m/cs.

Last edited by Smitty; 09-29-2007 at 12:32 PM.
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