I have hardcore data to add to the discussion. I had my clutch replaced at 42000 miles because a lady cut in front of a guy in a jeep who smacked into me wrecking my car. The impact damaged the suspension and tranny which had to be replaced.

All three had their feet off the clutch at the time. So, it's obvious that if you keep your foot off the clutch you will need a new clutch pre-maturely

 

This is generalizing to the particular. Do you know for a fact that the clutch in the MINI has a self-adjusting clutch system? I am not trying to pick a fight, but before I could begin to evaluate the benefits of a self-adjusting clutch system for the MINI, I would need to know it had one. Separately, the issue of throwout bearing wear is not about the application cycle count, but about the application time. More time spent with the clutch pedal depressed is more time the bearing is being used (and depleted).

I would agree with that statement. Also, what failed? The throwout bearing? (Doubtful.) Or, the friction plate? (More likely, from the driver riding the clutch....)

And another factor, when the clutch friction plate is replaced, a general practice is to replace the throwout bearing at the same time - kind of like replacing the brake pads when the rotors are replaced.... So, from the perspective of tracking failure rates, it is kind of hard to be able to track the total expected life of a throwout bearing when it has such a high likelihood of being replaced before it has actually failed....

My point in my original post was to identify throwout bearings as a potential point of failure if one follows the practice of keeping the clutch pedal depressed at long stops was more objective identification of parts that could fail over time. Whether the failure occurred at 50,000 miles or 150,000 miles (or more), is an unanswered question. (And probably will never be answered, because of the practice of replacing the throwout bearing anytime the friction plate is replaced....) I personally haven't seen any clutch failures that were solely due to throwout bearing wear (I have seen one example due to manufacturing defect - the bearing material disintegrated).

 

Or sooner. And those some people will swear up and down that the reason for the clutch friction plate needing replacing is because of a manufacturing defect.... The only manufacturing defect is the one that occurred at conception....

 

Grommit and C4 are perfectly correct in stating that holding the clutch in at prolonged stops causes additional wear on the TOB. Whether or not this is enough to see a marked difference over four to five years is debateable. The fact remains: holding the clutch in invovles added duty cycling to the TOB - period.

Most people hold the clutch in at regular traffic light cycles which average approximately 2 to 3 minutes depending on locale. This may not be enough time to see an appreciable difference in TOB wear.

Riding the clutch between shifts is a bigger factor in prematurely wearing out the various components of a manual tranny. This is prevalent in stop and go commute traffic and commutes that involve several closely space traffic stops.

 

But, and excuse me if I am wrong (there is a reason my degrees are in biology and not engineering), isn't the throwout bearing in continual motion/action if the MINI has a self adjusting clutch and wouldn't that then mean that the major variable in clutch wear is the number of cycles it is put thru?

 

When I drove up to EAA last week and was getting into the parking lot, everyone was driving maybe 3-4mph at most and at that point the mini started chugging a little bit, so I put the clutch in, give it some gas let the clutch off and repeat for a period of a few seconds. I don't think that did anything to the car that I should be worried about.

What I do want to establish is that when you are going maybe 2-5mph, is it alright to continously do what I did at EAA? I'm also not the person who gets stuck in traffic often and even if it is, it's also for a minute or so and even then I'm moving at about 10mph. Going 5 or under is what I'm worried about just because the engine will start to chug.

 

When my flywheel went bad (terrible screech when leaving in first) and the dealer said it was a wear item, they wanted $1800 for the clutch assembly and flywheel including labor. That was at 35,000 miles and it was ultimately replaced under warranty at another dealer who knew the flywheel was broken not worn.

The bottom line is that the part costs are inconsequential. It is the labor that is significant.

Rich

PS-When we looked at the clutch it was pristine but we put a new one in anyway figuring we were there already.

 

Let me be clear about one thing. My concern is not just about the throw out bearing, and never said as such. Actually, holding the clutch in will cause more stress to the pressure plate, and cause it's early demise. Often, the throwout bearing will go out too.

A self adjusting clutch keeps the distance between the TOB and the PP constant, but not in continual contact.

 

Yes. It is in constant motion. But when you step on the pedal it puts considerable lateral pressure on that bearing that it dows not see when it is simply spinning. It is designed for that pressure but my feeling is that the less time under that pressure the longer it will last.

Add me to the netural with foot off the pedal camp. And add to that I rarely even depress the clutch to get it to netural when coming to an anticipated full stop. I simply "slip" it out.

Rich

 

If it's designed for that pressure then wouldn't it have been testing to determine how long it can withstand that pressure and the effects of pressure over various lengths of time?
My feeling is that if a part has been engineered to the point when a 2 minute exposure to said pressure begins to create excessive wear over time we have an engineering issue not a driving one.

How does holding it in wear the pressure plate, isn't it disengaged in that position?

 

That's all I'm sayin'!

 

I really am not concered with the pressure plate but thinking about it when you depress the clutch the throw-out bearing contacts the plate fingers and pushes them hard against its springs. Over time I would guess that holding them in less would be better in the long run for wear in that the pressure plate would get weak over time with more use than less.

That said in a properly designed system like we have the friction disk should be the item that wears out first no matter how hard or what technique the driver uses while at rest. If anything wears out before the disk, that should be unusual and I expect that normal for us in an S driven the way an S is designed to be driven (not necessaraly on the track but clearly spirited driving) the clutch "should" last at least 80,000 if not 100,000 miles or more. That would be an unmodded S. Cars that have pulleys and anything that adds horsepower would naturally see shorter lifecycles. That, of course, is IMHO with no imperical data except my engineering degree and lots of experience.

Rich

 

I can't help wondering how many clutch depressions my knee joint is engineered for. Oh what the heck I'll just order a replacement if it starts to squeek. LOL!

 

There's a lot of anger on this thread for some reason. I never expected clutches and throwout bearings to elicit such passion!

I keep my foot off the clutch at redlights, drive thrus, etc. I think it's just good practice to relieve stress on components whenever possible.

Throwout bearings are THRUST bearings. They are designed to take axial loads. Most bearings that people are familiar with are designed to take radial loads (such as wheel bearings). While the throwout bearing IS spinning whenever the engine is running, it is spinning unloaded. When the clutch is depressed, it is applying pressure to the fingers on the pressure plate to neutralize its clamping force (probably on the order of 1500 pounds or thereabouts). Bearings are sized according to an L10 calculation. L10 is the estimated number of hours that 10% of a group of bearings will fail. L10 is INVERSELY proportional to the amount of load applied. As I vaguely remember from a Machine Design class many years ago, this is a long and involved calculation.

I have a love/hate relationship with working on cars. I love to install better springs, swaybars, shocks, lighting, and other "improvements", but I hate replacing clutches, water pumps, starters, etc. Improving things is fun! Spending hours and hours of time and sweat just to get it functioning again is other than fun to me. (Now, for the record, I DO that stuff, but I'm not all grins when I'm doing it....)

My $0.02 worth,

Rawhyde

 

Sorry Dave. I never meant to call anyone a clutch holder. It just came out without thinking. I will try to behave in the future.

And for those that like to hold it in, rock on. I gotta go.

regardless,
Red

 

Anonymity + Opinion + The Internet = Comments you usually wouldn't make to someone's face.

If you can't get someone to subscribe to you point of view, it appears the next step is to insult them from the safety of anonymity.

 

In most pressure plates, the spring action is a series of solid metal "fingers" arranged like the spokes of a wheel, but pointing inwards. Sort of a reverse sunburst pattern. There is a collar or bushing usually at the center of the pressure plate that these springs connect to. This combined assembly is what is pushed inwards by the TOB then the pedal is pushed down. The springs then bend in towards the friction plate (or disc) to disengage the clutch.

Now, any metal will have a fatigue factor that is accounted for in the design of the part. A manufacturer will tell you that a pressure plate is designed to last for, oh say 80,000 miles of normal use. Normal use is the interesting phrase here. Borg Warner, one of the largest clutch manufacurers in the world, has not considered keeping the clutch pedal down, to be normal use. This has come out in advisories to distributors in the past. Some parts stores I remember, tried to sell clutch assemblies with "lifetime" guarentees. That practice has pretty well ended; they were losing money.

Most clutch failures are with the pressure plate springs, with the TOB coming in second. Disc problems are usually from feathering the clutch too much, and wearing the friction materal down, or heat glazing it.

 

Good reflexs! I wish I had kept my clutch depressed 2 yrs ago when a woman in a blazer (also talking on a cell phone) came up and rear ended my car...THEN fled the scene like a scalded cat! That's 1 reason that I now keep my foot pressed on the clutch at all stops now...I couldn't stand to have my Mini hit like that.

 

thats the ticket!! Reading this thread has been very interesting. I had to sit here and think about how I treat my car. I learned to drive on a 4spd 1980 Pontiac sunbird. That was in 1986. It had around 76k miles when we bought it. My father replaced the the clutch, at around 80k. Other than that, I don't remember any car of mine having premature (love it) clutch failure. Until I bought my 330i. At 3k miles, I noticed that when I disengaged the clutch to place it in neutral, it would make a vibrating/rumbling sound and sensation. I took it to the dealer. Their response was that it was working to bmw specs. Yeah, right. No new car should make those noises. I switched dealers, new dealer tested the clutch, and replaced it. faulty mechanism.

Anyway, I thought about my shifting style. I place the car into neutral when coasting. I place leave it into neutral at stop lights unless I can see that the light is about to change. But, over all, cars are for driving. And how can life get any better than getting to drive something you really enjoy. Sooo... if you want to preserve the life of your car... park it in the garage and appreciate it from afar. As for me.... I love to drive. See, ya'll worry about clutches, I HATE to replace tires. Always ruining my tires from driving through the alley! I can think of better ways to spend 800!

 

Pressure plate springs usually go bad when the clutch is overheated and they lose their "temper." Other than that, they are steel springs and no more likely to wear out than the steel springs that hold up your car. Failures are usually directly attributable to user error.

There's another thrust bearing to think about... in the engine. On the MINI it is crankshaft bearing #3, and is under just as much load as the throwout bearing whenever the clutch is held down. Some engines are notorious for having the crank thrust bearings wear thin until they actually fall out into the oilpan. The endplay then allows the steel crank to grind into the engine block, rendering both unrebuildable. Automatics never seem to have this problem, of course.

And the MINI has self-adjusting disc brakes too, but that doesn't mean they don't wear out.

 

I was going to mention this but didn't and I think you are correct. The decision to keep the car in gear when stopped is not only a mechanical decsion. I have taught a number of advanced driving classes for special purpose driving and being ready to lauch quickly in first gear is definately a consideration in some traffic situations. Of course you need an escape route as well. Usually I will only place the vechicle in neutral when there is no possible traffic movement and vehicles behind me have come to a full stop.

I did escape certain Mini destruction on one occassion by leaving space and having the car in gear. However, the JCW's ability to launch in second gear came into play as I had down shifted in heavy fog and was unable to get into first before the need to escape occured.

I think it's fair to say that there are pro's and con's to both techniques and situations where either will be of benefit. I don't think parts wear is much of an issue and I have never replaced a clutch or a throwout bearing in any of the cars I've owned over the last thirty six years but if you do that doesn't mean that use was absolutely the cause. In any case to each their own...

 

Another bit that fails, are the rivets that hold the pressure plate springs.

 

What an educational thread! Thanks to all for contributing! It's been good reading! Apparently I'm quite old school. I've always shifted to neutral and released the clutch when stopped. Never coast in neutral, and double clutch when I down shift.

My last fun car was a '94 Ford Probe GT, I drove it 10 years as my daily driver, put on 74K miles and never had a clutch problem. So I just assumed I was doing something right. Maybe I was just lucky! Reading all the other opinions on driving a stick are quite interesting.

 

This was a good thread. I'm gonna give it a bump. I am of the clutch out at lights school, being a mechanic, I always have a mental image of the machinery working while I'm operating it and I can see the wear occuring as its being used. Sounds weird, but it helps in working the clutch and shifting properly and efficiently if you can visualize the components and understand how they work. The throw out bearing works overtime when it is pushed against the pressure plate springs for long periods, this includes resting your foot on the pedal while driving. The clutch disc and friction surfaces of the pressure plate and flywheel wear faster if the you ride it, and the shift forks in the gearbox wear if the rpm's are not matched properly OR the clutch is not disengaged fully when shifting and when your hand remains rested on the shift lever while driving. These are facts that mechanics use everyday to diagnose problems with clutches and gearboxes.
The following picture is from a MINI with less than 50,000 miles brought to me this weekend. The bearing exploded, and the clutch appears OK (I am replacing it anyway due to other damage). The finger springs on the pressure plate are tempered blue from the bearing overheating and ***** from the bearing have lodged and broken the nose cone on the starter. Luckily, none found their way into the box. Also, the bearing case jambed and the slave cylinder broke from excess force at the pedal.
Oh, and the MINI does NOT have a self-adjusting clutch like some BMW's.
As far as driving habits, I drive hard, and experience very long life out everything I have owned
Cheers,
--Dan

 

Just a thought. When sitting at a light with the transmission in neutral and the clutch out, gears in the transmission as well as the clutch friction disk are turning at engine speed. Immediately pressing the clutch and putting into 1st gear requires the syncro rings to stop all rotating components, causing wear. I don't how the long term effect, but I like to anticipate the light and press the clutch pedal a few seconds before (5-10) and let internal friction stop or slow the components before putting into 1st gear. Just a thought.