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Kirkham Motorsports

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  • 1 Post By patrickt
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  #1 (permalink)  
Old 05-27-2018, 10:14 AM
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Default Throw out bearing free play on my ERA

My ERA uses their external slave cylinder set up and I have a pretty good sized return spring on it but apparently it's not enough.



Anyway I noticed this spring is not strong enough to fully retract the slave cylinder piston and pull the TO bearing off of the clutch fingers. I can put the palm of my hand on the outer end of the fork and press it forward and pull it off of the fingers but this spring isn't doing it.

I guess I just need to find a bigger spring but it's going to take a pretty stout one which is not going to make my already heavy clutch pedal any better. May have to be one of those infamous Gorilla springs so well know in Mopar and early C1 Corvettes. My question is if anyone with a similar set up has found a spring that works from Dorman or some place else?
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Old 05-27-2018, 05:07 PM
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Don't work yourself up on this. And don't put a spring on there that hurts your leg when you push the pedal either. The debate on "should the TOB touch the fingers" has been on the forums for years and is loaded with dis-information. When you start reading through them all, like this one: Throw out bearing always makes contact? remember that there is a difference between the TOB having a load on it and when it is just lighting riding on the PP. Your TOB will outlast you, unless it is installed ridiculously wrong, which it's not.
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Old 05-27-2018, 05:12 PM
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Thinking about it - the Tilton MC has a return spring in it and the BMW slave cylinder has a return spring in it. That's a lot of residual pressure working to hold the TO bearing against the clutch fingers. I guess I could try to add a spring to work on retracting the master cylinder piston in addition to the one working on the piston in the fork/slave cylinder. It's all connected by fluid pressure.

Or is everyone running with positive contact between the TO bearing and the clutch fingers and getting away with it? Hasn't seemed to hurt my TO bearing so far as it's been silent.
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Old 05-27-2018, 05:29 PM
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Quote:
Originally Posted by DanEC View Post
Or is everyone running with positive contact between the TO bearing and the clutch fingers and getting away with it? Hasn't seemed to hurt my TO bearing so far as it's been silent.
I have a FM #614038 on my Tremec with my Centerforce PP. I have zero clearance, very light load (how light? dunno). I run a return spring and there are some pics of my set up in that thread from 2010. I don't give it a second thought and it will, undoubtedly, outlast me.
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Old 05-27-2018, 05:42 PM
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All depends on what type of throwout bearing you have. Some were meant to have clearance, some weren’t. Helps to know which you have.
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Old 05-28-2018, 04:00 AM
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I'll have to look it up - can't recall if Keith Craft provided it with the clutch or if it came from Blykins. It does have a grease zerk on it which is unusual.
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Old 05-28-2018, 04:06 AM
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You need play, or very light pressure, to compensate for the wear of the friction disk.

I believe 3 mm is enough. Bear in mind that the ratio fingers to disk is 7:1 which allows for very little wear in thickness of the friction material until the clutch is worn out (and you're riding the rivets).

If your play is too small or the TO bearing won't allow the fingers to move sufficiently your clutch will slip prematurely.
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Old 05-28-2018, 06:29 AM
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I believe this is the TO bearing I have on my car - looks exactly like this and my clutch components are McLeod. It's rated for constant contact so I guess light contact is not going to hurt it - or at least that is what I make of the statement, "constant running".

https://www.jegs.com/i/McLeod/673/16031/10002/-1

It would take a really big, stiff spring to fully retract the master cylinder and slave cylinders against their internal springs. So I guess I'll just put the one I had on it back on to lighten the contact slightly and call it good.

I vaguely remembered a prior thread on this subject from way back and managed to find it if anyone is wanting to refresh old memories.

Throw out bearing always makes contact?
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Old 05-28-2018, 06:35 AM
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Quote:
Originally Posted by DanEC View Post
I vaguely remembered a prior thread on this subject from way back and managed to find it if anyone is wanting to refresh old memories.

Throw out bearing always makes contact?
That's the same thread I referenced in my first post. I've seen the McLeod TOBs with the zerk fitting. If you wanted to, could you grease it through the fork hole? I'm thinking if you had it in an off-road mud car of some sort.
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Old 05-28-2018, 09:11 AM
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I overlooked that link you posted - not real observant. The zerk fitting is facing the clutch of all things. I will probably pull it out and give it a shot before starting it back together again. Don't want it too full though to where it slings grease out.
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Old 05-28-2018, 09:19 AM
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Quote:
Originally Posted by DanEC View Post
I overlooked that link you posted - not real observant. The zerk fitting is facing the clutch of all things. I will probably pull it out and give it a shot before starting it back together again. Don't want it too full though to where it slings grease out.
Well, if you're going to pull it out... In that thread that we both reference, the single most important post is on the fourth page and it is by stallion112, who works in the TOB industry. He clearly explains the difference between "standard" and "self aligning" throw out bearings. The latter require just a bit of preload. My FM 614038 is clearly described as a "sealed and self aligning" TOB. I can not tell if your McLeod is self-aligning or not. I do not know why they even make "standard" TOBs anymore, but that choice, as opposed to "self aligning," is one of the filter choices on Summit Racing and other parts warehouses. Anyway, that's the Cliff Notes version of the difference.
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Old 05-28-2018, 10:14 AM
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And for our mechanical engineers out there that demand a detailed, and thorough, explanation of the Federal Mogul "self-aligning" mechanism, here it is: https://patents.google.com/patent/US4534458

Now, since FM holds that particular patent, obviously their TOBs use that particular method. And the fact that they are sealed makes it really easy to avoid overlubing the zerk (since there ain't one).

And I still can't tell you whether the McLeod TOB is self-aligning or not.
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Old 05-28-2018, 09:58 PM
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Since FM holds the patent, isn't it safe to say that others don't, and as such won't have the self-aligning version? :-)
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Last edited by Dominik; 05-28-2018 at 10:07 PM.. Reason: typo
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Old 05-29-2018, 09:23 AM
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Quote:
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Since FM holds the patent, isn't it safe to say that others don't, and as such won't have the self-aligning version? :-)
Not at all. There are several patents out there on "self-aligning TOBs" so it's not like FM has a lock on it all. Many of the TOBs that fit Dan's and my cars (small spline toploader and Tremec TKO) are self-aligning... but not all. A quick Google of SSTL/TKO TOBs shows that, in addition to my Federal Mogul Part #614038, which is sealed and self-aligning, other manufactures that provide a self-aligning type TOB include Hayes, Centerforce, Ford Performance, Howe, et. al. -- but I don't think the McLeod 16031 is self-aligning, at least none of the parts warehouses list it as such. Interestingly enough, Centerforce discusses their self-aligning TOBs in their "Clutch Diagnostic Guide" and goes to great lengths to encourage the use of self-aligning TOBs. https://www.carid.com/images/centerf...osticguide.pdf Now, I'm sure there's a reason why someone would want the old, standard thrust type TOB over that of a self-aligning type, but I can't tell you what that reason might be.
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Old 05-29-2018, 12:38 PM
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I am not using a return spring at all.
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Old 05-31-2018, 01:46 PM
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I don't use a return spring either. I tried one that was heavy enough to pull the bearing back off the clutch fingers, but it required so much leg pressure that I decided it wasn't worth it so I took it off. That was about 10 years ago and my throw out bearing is still just fine.
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