Adjustable release bearing

What are the advantages of the adjustable TO bearing' aside from the adjustability?
I've read that they are terribly hard to get perfect and are not adjustable without removing the ZF.
Will

First,remove the bellhousing from the transaxle. Then,measure the distance from the face of the TOB (with it engauged into the fork and all of the way back towards the transaxle) to the mating surface where the bellhousing attaches to the transaxle case. Next,bolt the bellhousing to the engine .Then measure the distance from the mating surface of the bellhousing where the transaxle case attaches to the fingers on the Pressure Plate.
You want the measurements to be .150"-".200" different than each other .(with the first measurement being smaller). As the clutch wears,the fingers will move out towards the transaxle.
Hope this helps.

Ron

Thanks Ron - that's what I've been doing. Just needed to know how much clearence is needed.

Regarding the adjustability then yes, you have to remove/add shims to the bearing so the transaxle has to come off.
There are two .200" shims and thus 3 settings.
The bearing is (in my case) used when going from a original style 3-finger to a diaphragm-type clutch as the clutch fingers stick farther out on the diaphragm.

Kristian

4N, the advantages of a concentric throw-out are;
1)- all the friction-inducing linkage inside the bellhousing is eliminated; a stock clutch then becomes easy to push in using a stock clutch master cylinder.
2)- the throwout's travel from a concentric bearing is further for a given pedal movement, resulting in more clutch disengagement and resulting longer life for your expensive and difficult to replace ZF synchronizers. It acts like a long-throw slave cylinder.
3)- about 6 lbs of weight and complication is eliminated from the engine, and the need to lubricate the two needle bearings at both sides of the bellhousing on the ends of the cross-shaft is unnecessary (most have NEVER been lubed!) The assembly has a remote air bleed that exits the bellhousing thru the now-unused left side cross shaft hole, while the pressure line from the master cylinder enters the bellhousing thru the right side hole. No drilling needed.
The disadvantages are:
A)- you MUST follow the directions EXACTLY in adjusting the assembly, The quad-ring that keeps the hydraulic fluid inside is designed only for linear motion and will not tolerate any rotary motion. NOT setting the free play exatly per instructions means that when things heat up and expand, the throwout piston will bottom in the housing, and will begin spinning with the throwout bearing. 50 miles of this is enough to destroy the quad ring and the assembly will leak.
B)- the assemblies are expensive relative to a stock unit.
C)- being installed around the ZF input shaft just like a throwout bearing, to replace the assembly, the ZF must be removed (or at least slid back enough to access the clutch and throwout assembly). Rebuild parts are available quite reasonably priced but again, this is a precision assembly and needs care and cleanliness when working on it. A leaking assembly may also waste the clutch disc, so given the trouble and expense to redo things, it pays to follow directions!

4n, I should have mentioned also:
Quella's assembly is built similarly to mine which instead uses Tilton racing parts. Quella's unit adjusts for height via a tricky threaded adapter that slides over the stock ZF nose piece with a thin, large-diameter jam nut. RED LOCK-TITE THIS NUT ONCE ADJUSTMENT IS FINALIZED! These jam nuts have come loose so the adjustment shifts.
My Tilton assembly instead uses a custom threaded ZF nose-piece so the height adjustment is by rotating the whole concentric assembly up or down, which is then locked with an allen screw thru a protruding boss on the Tilton assembly. My assembly has been in our car for 14 years trouble free but I still carry a complete spare on long trips... parts are available but you won't find them at a rest-stop gas station!