Tilted Forum Project Discussion Community - View Single Post - Educate Us: Mechanics behind driving a manual transmission...

Peryn · 01-28-2004, 08:44 PM

Well, for long clutch life, realize when it wears and you can pretty much figure out how to make it last on your own. The only time the clutch material really wears at all, is when it is only partially engaged. When engages, the flywheel and pressureplate/input shaft are locked together. The clutch is stationary on them, and the whole assembly is turning. The clutch material, is therefore not being worn. When it is fully disengaged (petal to the floor) nothing is really touching it, so naturally it wont be wearing down. At any point in between though, when it is touching the rotating engine parts, and not locking them together, you are wearing down the clutch. So slowly taking off, your clutch is spending more time with the engine moving fast, and the clutch not moving as fast. Kinda acts like sandpaper and wears away the clutch lining. Where as if you drop the clutch quickly, while you stand a chance of shattering the clutch if its mega-fast, there is essentially no time in there for the clutch to spin off its coating.

If it helps, think of it just like brake pads and rotors. When your foot is off the brakes, they aren't being used because they aren't touching the rotor (flywheel), and basically wont wear down. When you are stopped, and the pads are clamped all the way down on the stopped rotors, neither is moving (when the clutch is engaged and you are moving...parts are "stuck" to each other). Your brake rotors aren't turning inside the pads, so again, neither is wearing down. It is only in the process of doing the braking - some point where the pads are clamping down, but not stopped totally - that you wear them out. This is just like your clutch. It only wears the lining (very similar to that of your brake pads actually) when its partially engaged/disengaged, but not at the extremes. Now that you know when/how it wears, you can judge how to drive for long life. Quick engage/disengage of the clutch wont wear as fast, but puts a little more shock and abuse onto the other parts. Holding yourself at a hill with the clutch is like driving with your brakes on...its just gonna wear them VERY quickly. Taking a long time to engage the clutch just increases the time its wearing down (which is why 2nd and 3rd gear starts tend to be so hard on clutches).

As for not downshifting and using the engine to slow you down...it depends on how you do it. If you just engage the clutch in the lower gear, and let that spin the engine up, then yes, it is bad for the car and clutch. BUT, if you can spin the engine (flywheel) up to the same speed the input shaft of the transmission, there (theoretically) will be zero clutch wear. If you tap the gas after shifting down, before letting the clutch in, you can rev one side of the sandwich (flywheel, clutch, pressure plate) up to match the other side. Then when you put them together, there isn't a difference in speed, and nothing wears as they go together. When done properly, you shouldn't feel any jerking or engine revving while engaging the clutch. Once the engine and tranny are locked together, you can let off the gas and let the engine help slow the car down without any problems.

01-28-2004, 08:44 PM	#10 (permalink)
Peryn Junkie Location: San Diego, CA.	Well, for long clutch life, realize when it wears and you can pretty much figure out how to make it last on your own. The only time the clutch material really wears at all, is when it is only partially engaged. When engages, the flywheel and pressureplate/input shaft are locked together. The clutch is stationary on them, and the whole assembly is turning. The clutch material, is therefore not being worn. When it is fully disengaged (petal to the floor) nothing is really touching it, so naturally it wont be wearing down. At any point in between though, when it is touching the rotating engine parts, and not locking them together, you are wearing down the clutch. So slowly taking off, your clutch is spending more time with the engine moving fast, and the clutch not moving as fast. Kinda acts like sandpaper and wears away the clutch lining. Where as if you drop the clutch quickly, while you stand a chance of shattering the clutch if its mega-fast, there is essentially no time in there for the clutch to spin off its coating. If it helps, think of it just like brake pads and rotors. When your foot is off the brakes, they aren't being used because they aren't touching the rotor (flywheel), and basically wont wear down. When you are stopped, and the pads are clamped all the way down on the stopped rotors, neither is moving (when the clutch is engaged and you are moving...parts are "stuck" to each other). Your brake rotors aren't turning inside the pads, so again, neither is wearing down. It is only in the process of doing the braking - some point where the pads are clamping down, but not stopped totally - that you wear them out. This is just like your clutch. It only wears the lining (very similar to that of your brake pads actually) when its partially engaged/disengaged, but not at the extremes. Now that you know when/how it wears, you can judge how to drive for long life. Quick engage/disengage of the clutch wont wear as fast, but puts a little more shock and abuse onto the other parts. Holding yourself at a hill with the clutch is like driving with your brakes on...its just gonna wear them VERY quickly. Taking a long time to engage the clutch just increases the time its wearing down (which is why 2nd and 3rd gear starts tend to be so hard on clutches). As for not downshifting and using the engine to slow you down...it depends on how you do it. If you just engage the clutch in the lower gear, and let that spin the engine up, then yes, it is bad for the car and clutch. BUT, if you can spin the engine (flywheel) up to the same speed the input shaft of the transmission, there (theoretically) will be zero clutch wear. If you tap the gas after shifting down, before letting the clutch in, you can rev one side of the sandwich (flywheel, clutch, pressure plate) up to match the other side. Then when you put them together, there isn't a difference in speed, and nothing wears as they go together. When done properly, you shouldn't feel any jerking or engine revving while engaging the clutch. Once the engine and tranny are locked together, you can let off the gas and let the engine help slow the car down without any problems. __________________ Dont cry kid, It's not your fault you suck.