Clutch and clutch wear

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  tonyjzx on 18/06/2013 - 02:20

  i have a corvette ls7 clutch in my car

  i dont think any of your activities really constitutes unusual wear

  it is wear nonetheless but nothing too bad

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  _Bruce_ on 18/06/2013 - 07:31

  Any time you are engaging the clutch and the rev doesn't match your speed and gear then there is some degree of wear. The clutch is designed to handle this, but try to keep it to a minimum.

  Particularly crawling or holding the car at lights is bad.

  Yes older non-sport clutches are a lot more forgiving and will slip when the speeds don't match much more, but this also reduces the power transfer.

  • 

    Davo1111 on 18/06/2013 - 08:01

    Particularly crawling or holding the car at lights is bad.

    citation?

    I'd say bunny hopping is the worst.

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      OzzyOzbourne on 18/06/2013 - 08:17

      I believe he meant bad for the clutch, which is the topic of the OP, because it is slipping and causing wear in that situation and hence could be referred to as bad.

      There are certainly other things that are worse for the clutch and vehicle driveline as you say.

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      _Bruce_ on 18/06/2013 - 08:54

      Sure bunny hopping and stalling are both bad.

      http://en.wikipedia.org/wiki/Clutch_control

      Normally, when a vehicle is stationary on an uphill slope it is necessary to use the handbrake in conjunction with clutch control to prevent the vehicle from rolling backwards when pulling away. However, in situations where the vehicle must be stopped briefly, for example in slow moving traffic, the clutch can be used to balance the uphill force from the engine with the downhill force of gravity. The benefit of this is that there is no need for the hand- or foot-brake, and the driver can pull away more quickly. Using this technique will, however, wear out the clutch faster.

      Also this is likely to increase fuel consumption.

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  OzzyOzbourne on 18/06/2013 - 08:14

  A clutch is basically a friction material which allows a faster spinning engine to connect to a slower spinning (or stationary) gear box, until the point they lock together (clutch not pressed). Any slippage of the clutch ie. with the pedal pressed to partially or fully disengage the clutch will cause some degree of wear, because the friction material is being rubbed.

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  Speckled Jim on 18/06/2013 - 09:37

  1) Take off from traffic lights, where you accelerate a little (or a lot if I got impatient) then release the clutch and sometimes "hold" the clutch while accelerating for like 0.5 seconds?

  This is "slipping" the clutch and yes, it increases clutch wear. The higher the revs (flywheel rotational speed) the greater the wear rate.

  2) Normal shifting of gears, including both up and down shifting (and sometimes down shift a little too quickly to the point the engine revs up to 3.5-4)?

  If you engage/disengage the clutch reasonably quickly during these up/down shifts, it doesn't represent a significant increase in clutch wear. When your revs rise to a greater degree after downshifting, you're increasing the engine braking effect. The wear here is greatest on rods, rings and valvetrain.

  3) Stepping onto the clutch while waiting at traffic lights?

  If the transmission is in neutral there's no effect anyway. Assuming that's what you meant.

  I also happened to be in a sports car once, and found that the clutch of such car, though heavy, seemed to "bounce back" to almost the biting point. I have never experienced such clutch before (I had been driving old bombs). Is that specific to the make and model of specific cars, or was there something special about that clutch

  Most likely a heavy duty clutch here using heavier springs. May also have a heavier spring in the pedal box.
  Hard to know for sure without knowing the exact make/model. Even then, the clutch may have been aftermarket.

  • 

    Ether on 19/06/2013 - 18:28

    The sports car that I was driving is still under new car warranty, so I doubt it is modded. In short, it is heavier than a usual clutch, and seemed to bounce right back at near the biting point if I release my foot. It means it is easier to operate than a normal clutch.

    What I meant was that if say I was idling in front of the traffic light. Normally I'd just step on the clutch and brake at the same time. Someone told me that would wear the clutch as well, which I don't really believe but not sure.

    Also, I have a habit of holding the clutch at the biting point at the traffic light (or T-intersection), for this enables a quicker take off. Would that introduce clutch wear?

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      Speckled Jim on 19/06/2013 - 19:05

      The sports car that I was driving is still under new car warranty, so I doubt it is modded. In short, it is heavier than a usual clutch, and seemed to bounce right back at near the biting point if I release my foot. It means it is easier to operate than a normal clutch.

      Cars with decent power outputs usually have heavier clutches for longevity.

      What I meant was that if say I was idling in front of the traffic light. Normally I'd just step on the clutch and brake at the same time. Someone told me that would wear the clutch as well, which I don't really believe but not sure.

      Not much in the way of clutch wear in that scenario if you're depressing the clutch pedal all the way. If you're riding it — transmission still in gear, even at idle — yes a little wear.

      Also, I have a habit of holding the clutch at the biting point at the traffic light (or T-intersection), for this enables a quicker take off. Would that introduce clutch wear?

      Yes it will wear a little quicker than the method below.

      In my case, if I know I'll be stationary for a while, I stay in neutral with the handbrake or brake pedal. If pedal, I only engage first gear a few seconds before green and simply shuffle off the brake (or handbrake) and move off.

      If you want quicker starts, it's better (and cheaper) to work on your reaction times. If you know the phasing of the traffic lights, this can help. But it's got to remain secondary to other considerations (dawdling pedestrians, cyclists, emergency vehicles etc).

      When in my "better" car I make occasional exceptions to the above. But given how risky it is these days (impounding and crushing cars) my desire to keep it outweighs the fun of traffic light drags ;)

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        Ether on 20/06/2013 - 13:08

        Ok thanks for the clarification.

        I've been taught by different instructors. Some told me to hold the clutch at biting point (where the engine "lifts up"), and then take off; while some tells me to hold petrol to 1.5-2 revs and then slowly release the clutch. I tend to go for the first one because my left foot either releases too slowly or too quickly, but have been told that it is very dangerous if my right foot fails to coordinate the acceleration. I'm also a serial offender for using the clutch and first gear (without acceleration) to move the car when parking or getting out of the garage. Maybe thats bad clutch wear also?

        It is kind of confusing being taught by so many who all tells me different things. Realistically, how bad is the wear to the clutch if I drive the way described above?

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        _Bruce_ on 20/06/2013 - 13:16

        Ether: Doing this things you describe is fine. There is a difference between:

        Leacing the cluth disengaged until the lights are about to change. Move the clutch the start of the grabbing point, then take off when ready.

        And:

        Wait at the lights with the clutch partially in.

        Also between:

        Perform a slow small reversing move with a slipping clutch

        And:

        Slowly roll forward in peak hour traffic for a long time with the cluth slipping.

        The clutch is meant to be used how you descripbe, but within reason. Try not to leave it partcially in for longer than you need to.

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  MATTDAMON on 18/06/2013 - 16:26

  -1

  Any kind of slippage (ie riding the clutch a bit/holding the vehicle by the clutch etc) will cause wear on both the friction material and on the fingers/throwout.

  Regardless of what you do, driving around the city etc will mean you will go through more clutches then someone out in the country.

  But hey, a clutch is cheaper then a replacement gearbox.

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  Jalif on 19/06/2013 - 10:40

  Heat is what kills clutches. If the clutch becomes too hot the friction material becomes more fragile, and begins to disintegrate.

  Riding the clutch is the main problem as the constant slipping causes heat build up, and does not allow the heat to dissipate.

  Harsh engagement of the clutch is less damaging than you think, as is stalling.

  A previously heat damaged clutch is already fragile and may be damaged by harsh engagement, however this is only the scare that triggers the heart attack, where the clutch riding is the high cholesterol diet that is the underlying cause.

  • 

    Mikinoz on 20/11/2013 - 20:52

    +1

    Weirdest comment goes to

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  onlyletters on 21/11/2013 - 16:59

  A clutch has plenty of meat on it, I wouldn't worry too much, the less you use your clutch to slip, the more pressure you will put on your gearbox/tires. I would rather replace a clutch any day of the week instead of the gearbox. Clutches are designed to be worn, they last about 120,000 kms.