advice re clutch please

BRG190 Pete · 15th October 2008, 19:26

Hi all

About 6 months/9k miles ago, I had a new clutch plus master and slave cylinders (at great expense!)

I've noticed recently that the biting point seems quite high (not sure if this has always been the case). I can change gear with the clutch pedal about half way up. The clutch doesn't seem to be slipping, though. In fact, the car pulls very well in all gears. I had thought that a high biting point means the clutch might be worn out, but mine is virtually new. Is this anything to worry about, please?

Also, when the engine is cold, I do find the car judders when moving off in first gear. I seem to be able to solve this problem by increasing the revs when moving off. Any ideas, please?

Simon · 15th October 2008, 19:45

I had always thought that the higher biting point was synonymous with the new clutch and a clutch pedal that goes almost to the floor is a sign of wearing clutch plates.

BRG190 Pete · 15th October 2008, 21:02

Thanks for the reply. That is reassuring, but.....

I do find this confusing, as some sites I have looked at say that a low biting point is a problem while others say that a high biting point can indicate a worn clutch.

Should be grateful for any further clarification.

Simon · 15th October 2008, 21:13

I guess it depends on whether you are comparing like-for-like cars. I'm not totally 100% sure on this so we best wait for some clarification from some our more knowledgeable members.

T-Cut · 15th October 2008, 21:36

Here's what I reckon. I'm assuming that the hydraulic system is faultless. With a self-adjusting clutch like these, it shouldn't make much difference whether the clutch disc is new or well worn. The release bearing to diaphragm distance sets automatically as the friction plate/diaphragm creep towards the flywheel due to the disc getting thinner. Whether the point of take up is high or low is determined by variations in the system used to press the diaphragm, in this case a hydraulic piston. I guess pistons (slave cylinders) vary slightly in their capacity and mechanical efficiency. This could lead to differences in 'feel'. I can't think of any other reason for it so I'm interested in what others say about it.

TC

amableson · 16th October 2008, 10:26

The only hydraulic clutch i can remember with adjustment was the early mini's with the bolt nut arrangement on the end of the bell housing, all others are self adjusting like wot he just said.
Unless you know different.

pondweed · 16th October 2008, 10:48

I think I agree with TC but I've always wondered about the difference in capacity/volume of the hydraulic system as the adjustment is gradually made over time, to compensate for wear. Surely this increases...although as our master is sealed presumably/perhaps it doesnt!

I also get confused about the ambiguity of high and low biting - is this high as in "push pedal down nearly all the way" or high as in "nearer your foot - dont have to push it far..."??

I think the answer is that we are born worriers and any difference in the status quo is going to scare the willies out of you and make you consider an automatic, even though you aren't really old enough...

T-Cut · 16th October 2008, 11:18

Quote:

Originally Posted by pondweed

I've always wondered about the difference in capacity/volume of the hydraulic system as the adjustment is gradually made over time, to compensate for wear. Surely this increases...although as our master is sealed presumably/perhaps it doesnt!

As the clutch disc wears away, the volume of hydraulic fluid retained by the slave cylinder increases to compensate for the 'gap'. In practice, this volume difference (new clutch vs old clutch) is quite small and is supplied from the reservour feeding the master. The clutch pedal remains in the same position as the clutch wears, so everything is handled at the other end.

Quote:

I also get confused about the ambiguity of high and low biting

The 'high/low' description refers to the position of the foot pedal at the bite point. So, a low bite means the pedal is near the floor when the bite occurs. A high one is closer to the rest position. Neither are good things to have since they compromise the action of the clutch mechanism in different ways.

TC

T-Cut · 16th October 2008, 11:25

Quote:

Originally Posted by amableson

The only hydraulic clutch i can remember with adjustment was the early mini's with the bolt nut arrangement on the end of the bell housing

Yes the old mini had a fixed volume master/slave system, so wear wasn't compensated by increasing the slave volume. If the slack wasn't taken up by the stop bolt, you'd get a situation where the clutch wouldn't fully release the worn disc because the slave hadn't enough travel.

TC

pondweed · 16th October 2008, 13:17

so could the disparity be a result of using the wrong clutch master - i.e. the petrol fits the diesel but we know its about 1cm difference in length. I presume not.

Presumably the result of the tiny reservoir for the sealed clutch is that the fluid gets dirtier quicker? Or is there no diffusion over time between all parts of the system when clutch is depressed?

The value of bleeding the clutch surely must be worthwhile once a year or so to keep the system fresh.

15th October 2008, 19:26	#1
BRG190 Pete Avid contributor None at the moment Join Date: Sep 2007 Location: Wokingham Posts: 147 Thanks: 0 Thanked 0 Times in 0 Posts	advice re clutch please Hi all About 6 months/9k miles ago, I had a new clutch plus master and slave cylinders (at great expense!) I've noticed recently that the biting point seems quite high (not sure if this has always been the case). I can change gear with the clutch pedal about half way up. The clutch doesn't seem to be slipping, though. In fact, the car pulls very well in all gears. I had thought that a high biting point means the clutch might be worn out, but mine is virtually new. Is this anything to worry about, please? Also, when the engine is cold, I do find the car judders when moving off in first gear. I seem to be able to solve this problem by increasing the revs when moving off. Any ideas, please?

16th October 2008, 10:26	#6
amableson Gets stuck in Ex Rover 75 owner Join Date: Nov 2006 Location: Boston, Lincolnshire. Posts: 553 Thanks: 0 Thanked 2 Times in 2 Posts	The only hydraulic clutch i can remember with adjustment was the early mini's with the bolt nut arrangement on the end of the bell housing, all others are self adjusting like wot he just said. Unless you know different. __________________ Regards Andrew.[SIGPIC][/SIGPIC]

16th October 2008, 10:48	#7
pondweed This is my second home Waiter, Waiter! I seem to have a Roomster in my drive... Join Date: Nov 2006 Location: Sussex Posts: 3,268 Thanks: 0 Thanked 1 Time in 1 Post	I think I agree with TC but I've always wondered about the difference in capacity/volume of the hydraulic system as the adjustment is gradually made over time, to compensate for wear. Surely this increases...although as our master is sealed presumably/perhaps it doesnt! I also get confused about the ambiguity of high and low biting - is this high as in "push pedal down nearly all the way" or high as in "nearer your foot - dont have to push it far..."?? I think the answer is that we are born worriers and any difference in the status quo is going to scare the willies out of you and make you consider an automatic, even though you aren't really old enough... Last edited by pondweed; 16th October 2008 at 10:52..

15th October 2008, 19:45	#2
Simon Banned - Join Date: Nov 2006 Location: - Posts: 10,318 Thanks: 0 Thanked 4 Times in 3 Posts	I had always thought that the higher biting point was synonymous with the new clutch and a clutch pedal that goes almost to the floor is a sign of wearing clutch plates.

15th October 2008, 21:02	#3
BRG190 Pete Avid contributor None at the moment Join Date: Sep 2007 Location: Wokingham Posts: 147 Thanks: 0 Thanked 0 Times in 0 Posts	Thanks for the reply. That is reassuring, but..... I do find this confusing, as some sites I have looked at say that a low biting point is a problem while others say that a high biting point can indicate a worn clutch. Should be grateful for any further clarification.

15th October 2008, 21:13	#4
Simon Banned - Join Date: Nov 2006 Location: - Posts: 10,318 Thanks: 0 Thanked 4 Times in 3 Posts	I guess it depends on whether you are comparing like-for-like cars. I'm not totally 100% sure on this so we best wait for some clarification from some our more knowledgeable members.

15th October 2008, 21:36	#5
T-Cut This is my second home Rover75 and Mreg Corsa. Join Date: Nov 2006 Location: Sumweer onat mote o'dust (Sagin) Posts: 21,753 Thanks: 341 Thanked 3,660 Times in 2,924 Posts	Here's what I reckon. I'm assuming that the hydraulic system is faultless. With a self-adjusting clutch like these, it shouldn't make much difference whether the clutch disc is new or well worn. The release bearing to diaphragm distance sets automatically as the friction plate/diaphragm creep towards the flywheel due to the disc getting thinner. Whether the point of take up is high or low is determined by variations in the system used to press the diaphragm, in this case a hydraulic piston. I guess pistons (slave cylinders) vary slightly in their capacity and mechanical efficiency. This could lead to differences in 'feel'. I can't think of any other reason for it so I'm interested in what others say about it. TC

16th October 2008, 13:17	#10
pondweed This is my second home Waiter, Waiter! I seem to have a Roomster in my drive... Join Date: Nov 2006 Location: Sussex Posts: 3,268 Thanks: 0 Thanked 1 Time in 1 Post	so could the disparity be a result of using the wrong clutch master - i.e. the petrol fits the diesel but we know its about 1cm difference in length. I presume not. Presumably the result of the tiny reservoir for the sealed clutch is that the fluid gets dirtier quicker? Or is there no diffusion over time between all parts of the system when clutch is depressed? The value of bleeding the clutch surely must be worthwhile once a year or so to keep the system fresh.