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A note on shimming the pivot ball when installing new clutch

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turboglenn

15+ Year Contributor
6,375
111
Nov 5, 2007
RIpley, West_Virginia
Well, as everyone probably knows i've been going through a lot with the trans and clutch. Well after it was all said and done i just ended up with a surfaced flywheel, same old ACT PP (glaze knocked off by sandblasting) and a cheap-o parts store duralast friction disk

Anyway! When i put the trans in and installed the clutch slave the pivot point was way past center to where you would normally want to shim it.. I thought this was odd since the PP and FW were the same and i'd replaced the disk with a semi-new one before from RPS when the ACT one went out... and was trying to decide on what had changed, I knew a LOT of material taken from the FW from many surfacings or one real major one if it were far out ofspec (which it wasn't) could cause this as well as having the friction disc be thicker moving the fingers further from the TOB..

SO, after not being able to catch my machinist in time to see how much was taken from my flytwheel when he surfaced it i pulled the trans and found a lock washer for a 12mm bolt that was .060" thick (1.5mm) and installed that under the ball. (because i didn't want to chance putting the entire car toghether and having to pull it apart for the 5th time in 2 weeks)

So anyway, I get it all together, adjust the clutch to where i was 1/2 turn from the master's return valve being blocked and started driving the car lightly around... within a days time i pull out on the road and the clutch slips a little when i gave it some gas in 2nd gear, I immediately pulled over at the next stop (about 1/2 mile of no slippin babying the car) and checked the clutch, well the "break-in" only being 50 miles in so far has already taken the 1" of pedal play out of the top and there was no play left at all.. I had a short wrench in the door just in case i needed to adjust it, and good thing i did, I got it back to about an inch of pedal free play and went back to driving..

When i got home more playt had been removed and needed adjusted again (i was about 20 miles from home when i slipped and fixed it). NOw what's happening is the disc (which is to ACT's spec of .330 thick compressed and .340 untouched ) is starting to get broken in and there's probably a few thousandths wearing into the flywheel and PP as well as it starting to "compress" from pressure on it.. and the clutch arm is moving well back into what would have been just fine without shimming the pivot by the time it's fully broken in (i'm sure of this with the amount it's moved already)

I"ll update and i hope i didn't over shim (why i went rather thin to start with was that i had an idea something like this would happen, but never recal dealing with it before)

So, in short, if you put in a new clutch and have your FW surfaced and the clutch arm is not in the area the DSM community describes where is should be or you need to shim it i wouldn't worry too much unless the arm is hitting the trans case when when or before the pedal is to the floor (this being you test it as soon as you get the trans and slave cyl mounted up but before putting EVERYTHING back together) You should be able to feel that "point" of the clutch going past the spot where you feel it normally go "ffree", if all that's good, it's not hitting and you're getting ddisengagement you probably shuoldn't shim it unless it's a clutch that the vendor or other people like twicks69 or any wiseman says is a clutch that will normally require shimming (and the ACT2600 is NOT one that shoudl need shimmed as i've never had to shim one out of all the ACT's i've installed or have friends with them installed)

And being at only 75 miles of a 500 mile break in, i've already gotten back enough to know that i don't need the shim in there that i put in, but anything on the web will tell you "shim it" but nothing on the web says "If your clutch is new, when it breaks in, the arm will move back towards where it should be" and that's what i'm trying to let some people know.... if it's only moved over "center" by the normal amount it is at to the other side of center i would say shimming is not needed (but the arm hitting the case would be my deciding factor bsed on what this has taught me, and this is my 5th clutch in this car over 12+ years, but i never hear about or worried about shimming any of the others that were installed, i just always would adjust my clutch to where i like it, which for me is something that changes every couple of months and something that on my bike i taylor during every ride since it's at my finger tips)

This is something you can figure out as soon as you get the trans onto the engine and install the slave to the setup, I would advise that if the clutch will disengage wihtoutnthe arm coming intoi contact or near contact with the bell housing then just run it and it will get back to where it should be when it breaks in..mine was only about as far to the passenger from center as it usually was to the proper side on the old clutch that was in great shape till it was coated in oil.. I know if i hadn't shimmed mine it will get aback to where it was, and now i have to be carefull of adjustment because the shimmed ball can cause over travel and destroy the clutch in the future, buyt since i keep strict tabs on the entire car i won't let that happen, but for the average person who's mechanic shims a clutch that don't really need it this could be a bad reality
 
The information you are sharing is not accurate and can give the average person, using the correct clutch parts, issues.

If you allow the arm to move to the point that it is not making contact with the case, yet it is very close to the case, you will have problems in the future.

Several factors are involved when you look at how a throw-out bearing fork sits in the assembly. Things like aftermarket flywheels, resurfaced flywheels, mismatched disks, different pressure plates, and wear on the fork pivot point can all move the position of the fingers which will make the fork sit in a different spot.

Also, shimming the pivot ball has nothing to do with throw. The system is self-adjusting at the master cylinder. If the fork is not hitting the housing, it will move the exact same distance if it's shimmed or not. What changes the throw is the adjustment at the master cylinder assembly. You can back the cruise control switch UP and this will give you more throw. If the clutch flywheel is machined correctly, and the pressure plate fingers point outward slightly when assembled, then you can have as much throw as you want and the PP fingers will never make contact with the disk. If it is not machined correctly, then the fingers can make contact and cause damage. If you are hearing noises when you push the pedal down too far, and your fork is not sitting correctly in the window, then you have something grossly off somewhere. I would say the combination of a step height which is too short and a cheap disk, which is thicker than usual, would cause many problems.

The common thought 'everything is new, so you don't need to worry about shimming the ball' is not correct. Many aftermarket clutch manufacturers have the pressure plate fingers sit too far inward and this causes many problems. If you don't want to shim your pivot ball, but the fork is very close to touching the case, there is a very simple solution- Widen your flywheel step height. This will move the fingers out more and give you the added room you need to shift the fork over enough to sit in the assembly correctly without the need for a shim.

I believe so many people need to shim their pivot ball due to aftermarket clutch manufacturers allowing the pressure plate fingers to sit inward too far. If they were all sticking out slightly, no one would ever have to shim a ball ever again. 90% of the time, when we install new clutches at my shop, we will machine the new flywheel with just slightly more step height to allow the pressure plate fingers to stick out to the correct point. By making fine adjustments to the step height, we can set the fingers up to sit in the spot where it is not necessary for a shim and all is in the spot where Mitsubishi originally designed it to be. Why aftermarket clutch manufacturers have the fingers sit so far inward is still not something that makes sense to me.

In 50 miles, there is no wear on the clutch unless you have been slipping and launching it light after light and not following the wear/burn-in procedure. The wear-in procedure for a disk is not to 'wear' it into the other parts it makes contact with, but to burn the disk in. Organic disks have a resin base with mineral wool and a chopped fiberglass mesh which needs to be burned-in slowly and carefully in order for the material to live. I have seen disks where people didn't follow the wear-in procedures and the disk material blew off and scattered all over the trans bell-housing (looks like someone tossed a sheep in there). When you have a brand new clutch disk, and immediately floor it everywhere and slip it all over the place, the disk is most likely ruined and could have had some material loss and/or damage. This can also change the position of the fork as the surface area has changed due to the damage.

The only time the fork should start moving closer to the case is when it is getting old and material is starting to wear to the point that the system needs to adjust. When the clutch loses material, the fork will move to a different position. From what I have seen of clutch wear, though, it is very uncommon to see a fork move as the clutch ages (which goes against what I just said). True, material is lost on the disk surface, but at the same time, the pressure plate will warp and they seem to cancel any movement out in most cases. With a high mileage clutch, I usually see the fork sitting in the correct spot even though the disk is worn to the rivets, but you must be sitting in the correct position to begin with. The material lost at the disk seems to almost equal the amount of warp found on the pressure plate. For the average person, clutch wear doesn't change much in how the fork moves or sits in the housing.

What we usually do when dealing with an aftermarket clutch is we will set it up on our little jig we made and put it together. We will then calculate how much we have to modify the flywheel step height in order to have the fork and pressure plate fingers sit in the correct position. We have never had an issue using mismatched parts as long as the fingers are in the correct spot. One thing we have learned is disks are not the same thickness and if your clutch was designed for a race disk, and you stick an OEM style disk in the assembly, things change a bunch. It has taken me years to find that perfect spot and to be able to calculate what needs to be done to the step height in order to achieve that perfect position. Many times, I can run the flywheel through the grinder with my first calculation and it's right on the money these days. It took a lot of practice to get to that point...
 
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I'm not writing this to argue with you, But when i was speaking with another highly respected trans builder in the DSM workd and called to ask if i should shim because i was sitting on the wrong side of center with a brand new disk and a surfaced flywheel i was under the car already shimming when the call came back not to do it, but it was too late.

Now, not bringing third parties into this out of respect, everything i've said can be found to be backed up by both clutch manufacturers and owners in the VW, Camaro, Corvette, MIata, and off road truck forums as well as some on a honda forum with people all experiencing the clutch moving drastically as it first started breaking in and allowing the diaphram fingers to move outwards again to a normal position and in the other cars cases they used everything from different model TOB arms, thicker TOB's and many other "fixes" only to find once broken in the "band aids" weren't needed.. And there's even ONE post in the DSM world (archives of this site about the same thing)

LIke i said, i am NOT saying there's NEVER a time to need a shim, but that probably more people that are less knowledgable or new to cars/dsms; may be shimming when not needed...

What i said about throw was adjuust for the most you can get at the master and check disengagement and that the arm won't hit the case before you decide to shim.. as commonly said on this and many other DSM sites, shimming is a "band aid" to a problem that really shouldn't be there but in the cases of some aftermarket clutches, especially older twin setups there are cases where special changes need to be made, but to say that it's a cut and dry issue that some one MUST shim if the arm is on the wrong side of the "centerline" of the hole is wrong, i'm now at 100 miles or a tad more and my arm is moved over so far to the correct side that i did not need a shim at all, i needed to seat thge clkutch.

Anyone can use google for a while about this topic, specifically clutch adjustment and freeplay during break in or google clutch maker names and break in procedure and precautions and find that verything i said can be backed up by those who make the clutches for many OEM applications as well as aftermarket replacement (even on centerforce university youtube videos)

I'm not sure if there's some hostility towardsme due to the fact that when i was in a rush need of trans parts I PM'ed you too much or something or that i went with the route of the person who'd actually email/PM/call me back with advise and info at times other than their strict business hours and even after i said i'm broke, fighting for my disability and need to get by as cheap as possible which helped me dramatically, when you wouldn't show me the same courtesy after the first return call when i said i needed by as cheap as possible and asked if there was anything i had that was worth anything as a core to help aid in paying for my bill... I'm not making this personal, but i just can't see how you can say i'm giving false info when there's .pdf and other types of documentation from both clutch makers and users that there is substantial wear in the first 100 miles, but not only that but that MILES DON"T COUNT, it's clutch use and heat cycles, and my first 50 miles were all spent drivign at night stopping and going upshifting and downshifting constantly (i'd say 250-300 shifts and at least 125 stop and goes) done late at night in my neighborhood and road i live off of. so if you want to say something wont happen in "X" amount of miles, is not accurate.. even clutch makers state this, it's all in the amount of stop and go driving and shifting you do..

ALso, it's not only wear but that organic discs "compress" a tad with the initial use and force of high pressure aftermarket pressure plates (meaning compress a few thousandths from the state they are in when new in box, which is why ACT specs the clutch disc thicknesses as "compressed thickness"

again, i'm not here to argue or make this personal, but much of what you say in your reply stating i'm giving inaccurate statements, doesn't relate to what i say properly, the main one about throw and adjustment, if you read i said to adjust for maxthrow and make sure there's not contact to bell housing from clutch arm, and that if you can feel the disengagement point before making a shimming decision, also i said that there's cases where it IS needed but consult a person selling/installing/building these clutches for caseswhere it's said to be needed from the get go.

When i installed the trans with surfaced flywheel, new disc that was to ACT spec, and the same ACT PP, i was well on the "wrong side of center" of the hole, so i shimmed even though i could feel disengagement and there w2as no arm/housing contact.. now that i'm a tad over 100 miles the arm is further to the drivers (correct) side than it was when my old clutch was in and doing fine with proper adjustment thta i learned and used based on your videos, so when i said that much info out there says to shim, it was not a personal attack, as iuse your vids as ways to teach or show people what and how to do things on their clutches all the time, But either way, even at the low amount of "miles" and tons of shifts i have on the car now as well as stop and go actions, i can with 100% certainty say that if i didn't shim my clutch i would've been just fine and within normal "arm placement" by now. It's a good thing that i used a shim that was only .060 thick and not an ARP head bolt washer as some say is good to use or i'd have to adjust out so much excess throw that there could be a chance of over throw on the clutch, which as you seem to say isn't possible, again google will show you cases of it happening as well as clutch manufacturers saying that in certain setups this is neeeded to be watched for just like the free play dissapearing in the initial break in which can cause slippage as the diaphram fingers move outwards as the disc seats..

also, clutch type is relevant here, organic is said by the makers to wear/change the most in initial break in with the other harder compounds experiencing much less of this, and that flywheel surfacing, as well as many other factors will play a large role in what happens with adjustment and free play during break in..

I didn't make this up all off the top od my head, I experienced it, consulted other trans builders to back up basic thoughts then googled for about 2.5 -3 hours on it reading to re-assure what i was going through and back up any statements i've made.. one thing is that DSM's are a car where "shimming" is a way of dealing with this arm placement issue but in other worlds (car types) they use different model arms, TOB's and much more band aid remedies to deal with this and in many cases also find after break in that the extra effort, time and special fixturing to compensate for low pedal height from low diaphram fingers on initial install was never needed to start with and they were also now positive that all they also needed wasproper breaking in and didn't have a problem that needed a "band aid" to start with

anyway, i said i don't want to argue and don't wantt o make it personal, jsut trying to figure how it can be said that i'm making false statements, I never post opinion unless i state it as such (with an IMO = in my opinion) and before i make technical posts like this i always research that i'm notthe only one who's come tothis conclusion be it in DSM's or any other car as mechanical operations and parts are in many cases different looking but the axact same concept no matter who makes the part, car or hop up parts for the car.

And if you re-read my original post you'll see i say that there's times when you should consult the vendors (such as yourself) for times when there's a known issue or design change that is known to need shimming or changes to the arm,ball or TOB when buying the specific clutch

BUt i'll say again, i've never seen in person a single time that an ACT 2600 needed shimmed, wether i installed it or some one else did it themselves or had a shop do it for them.. if it weren't for the posts on here i'd never even know about it..

and the ENTIRE reason i posted this to start with is that there's a LOT of new begginier or non-mechanical experienced people reading posts here and once shimming was known to fix an issue like this it became something that was passed around like it was commonly known to be a pre-requisite of installing an aftermarket clutch when it isn't, all i'm tryiung to do is educate people that they should indeed check their own results and conditions before just following the pied piper and tossing a shim in with a brand new clutch.. and also that they should make sure the clutch assembly (meaning pedal, master and slave cylinders) should all be confirmed to be in good working order before making decisions to shim... I was wanting to shim at one point, then before that i decided to remove the clutch pedal and found it was cracked and flexing causing my clutch throw issues... and i'd NEVER seen that in all my hours on this forum daily until i posted it and found that MANY others had the same problem, and some even had the pedal not only crack and flex but actaully just break off and fall into the floor leaving them stuck

Main point is there's too many variables to immediately say some one should shim the pivot ball, and all conditions need ot be checked, and that there is (and this is backed up agian by clutch makers) a possibility of damage from having excessive throw/movement in the TOB and diaphram fingers..but anyway, AGAIN NOTHING PERSONAL, and NOT ARGUING, but to say my statements are false, or to say that it's a cut and dry issue that a shim is a "MUST" when the arm sits on the wrong side of center on a new install that they should immediately shim the thing... I think that if you have a broken in clutch and it's wrong you probably have something worn out, or have that certain clutch that's made different for high HP apps or whatever and may be known to require a shim, but that most of the common clutches such as ACT 2600/2100, CFDF and Exedy, shuoldn't need a shim and that other problems should be looked for before adding what's known to be a "band aid" and not a TSB style update/modification or recall
 
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