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Brand new throwout bearing and clutch smashedsad smiley

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lewmac Avatar
lewmac Silver Member Lew McAllan
Hawthorn Woods, Chicago, IL, USA   USA
1958 Austin-Healey 100-Six ~ For Sale ! ~
Well, the roller bearing from Colin Dodds has a teflon coating developed for F1 so likely has some longevity. It is not metal on metal" or at all off axis.

With regard to cost, what was it 450 miles for $25 plus say, 4 hours for engine in/out if you have it down to a fine art..... that's only $25/hour labor, to total $125.... plus repairs for any other damage.

So I guess it comes down to the value of the time spent on repairs and the hassle of pulling an engine every now and again ... or on the day of the next club event ..... or settling for a trouble free clutch for many years.

Invest $125.

Cheers
Lew

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refisk Avatar
refisk Rick Fisk
Frankenmuth, Michigan, USA   USA
Lew,

Every time you press the clutch pedal the throwout bearing will go off axis. The fork is mounted at a single point and every time it moves it will follow an arc causing the throwout bearing to move off axis. The throwout bearing can only be concentric with the pressure plate at a single point in the arc. sad smiley

In reply to # 3550794 by lewmac Well, the roller bearing from Colin Dodds has a teflon coating developed for F1 so likely has some longevity. It is not metal on metal" or at all off axis.

With regard to cost, what was it 450 miles for $25 plus say, 4 hours for engine in/out if you have it down to a fine art..... that's only $25/hour labor, to total $125.... plus repairs for any other damage.

So I guess it comes down to the value of the time spent on repairs and the hassle of pulling an engine every now and again ... or on the day of the next club event ..... or settling for a trouble free clutch for many years.

Invest $125.

Cheers
Lew

lewmac Avatar
lewmac Silver Member Lew McAllan
Hawthorn Woods, Chicago, IL, USA   USA
1958 Austin-Healey 100-Six ~ For Sale ! ~
Norm, just installed, not yet on road.... well I drove it down the street and back last weekend. You know Colin, ask him or see the link with some user reports.

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lewmac Avatar
lewmac Silver Member Lew McAllan
Hawthorn Woods, Chicago, IL, USA   USA
1958 Austin-Healey 100-Six ~ For Sale ! ~
Rick, perhaps off axis is the wrong description. The roller bearing will remain parallel to the clutch plate and will swivel in the fork, right ? There were several comments #12,13 and 14 regarding the metal on metal bearing setup not being ideal. As I discussed with Colin, his bearing uses the original carbon carrier, machined to accept the roller bearing and the teflon coating, so the geometry is unchanged.
Cheers
Lew

pixelsmithusa Avatar
Lew, what Rick is pointing out, is that clutch fork mechanisms that incorporate a roller bearing travel in a straight line, always parallel to the input shaft because there is a guide tube restraining the movement from going off axis. This is how it's done in the Datsun 5 speed. In the case to the Spridget fork movement, which pivots on a single point, even though the bearing remains parallel (under ideal conditions*), the bearing itself is only concentric at one point in the arc. Everywhere else, it's going to be making contact off-center. This works fine for the carbon bearing because it does not rotate and has a low friction mating surface. It's always stationary, so being off center is not an issue. With a roller bearing, it has to scrub the contact surface while rotating. I would think this is also apply different rotational forces on the bearing as it moves off center.

A better (and more costly) solution would be to install a concentric slave cylinder (also called hydraulic throwout bearing) inside the bell housing. This is what is sometimes used in racing applications. (see sample pic below) My vintage race Bugeye pictured in my profile was equipped that way in racing trim.

* I say ideal conditions because after a period of time, you can have the swings in the clutch weaken, and the maying surface on the pressure plate is no longer in a parallel place to the flywheel and release bearing. The release bearing pivots on one axis only, so this wobble is surely further detrimental to the carbon bearing.






Gerard

http://gerardsgarage.com/





Edited 5 time(s). Last edit at 2017-07-13 01:27 AM by pixelsmithusa.

Kerr Avatar
Kerr Platinum Member Norm Kerr
Ann Arbor, MI, USA   USA
By the way, I have a brand new Peter May roller bearing throw out bearing, never installed, that I am willing to sell.

I paid $77 + shipping from UK for it.


Anyone interested in taking it off my hands?



thx,
Norm

S1 Elan Kurt. Appley
Akron, Ia., USA   USA
Ideally, a quality carbon TO beating would be best. The original's gave acceptable life though never great life. They were deep black dense carbon, not the grey stuff we are getting now days. There would be a market for anyone that was able to source as good of carbon as original!eye rolling smiley Not just for Spridgets but many other Brit cars.


Kurt.

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ice Avatar
ice Gold Member Larry Ice
Lawrenceville, GA, USA   USA
Well, guys, I'm not an engineer but gotta go with what Gerard says is the problem with the non-carbon throwout bearings. I'm not sure the teflon coating is a. thick enough and b. the issue of the bearing not being centered in at least some of it's travel across the face of the pressure plate TOB surface. I'm not saying that it would not be an improvement but just think we should get some more comments here from users of the bearing systems. A part for $125 + shipping isn't going to ruin the bank but I'm looking for improved service life here as a reason for buying the part.
That Tilton part Gerard sent looks like the solution but again what's the cost and service life? Maybe a Oilite throw out bearing? It would seem like that would solve the problem of having to maintain the bearing being parallel and centered and it would function like the graphite does.
I can think of ways to use linkage to maintain the bearing parallel and centered at all times to the bearing surface on the PP but seems like it would be a weak point or would be more expensive to produce than the Tilton parts.
Hey, I know, put paddle shifter transmission on the car and have hydraulic clutches do the engaging!



Iceman

Atlanta GA

60 AH MK1
62 AH MKII
67 Midget
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PeterC Avatar
PeterC Platinum Member Peter Caldwell
Madison Wisconsin, USA   USA
Here are my thoughts, for what it's worth.

We have sold and i have installed many carbon bearings. The 3-piece KITS are packaged with the bearing loose inside the box, sometimes wrapped in bubbles, oft times not. Carbon does not "like" being dropped, hit, nicked or shocked.

I suggest buying the separate pieces and getting a bearing that is BOXED separately.

The only warranty we had on a bearing was from a kit.

Peter c


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dickmoritz Avatar
dickmoritz Gold Member Dick Moritz
Philly 'burbs, PA, USA   USA
I am no fan of the roller bearings. What I especially dislike about them is the fact that MGs and other British cars that originally came with the carbon bearing have no pull-back mechanism. Those folks that talk about all the 'murcan cars that have used roller bearings for decades seem to miss the fact that all of those vehicles had mechanical clutch linkages, not hydraulic, and all of those systems used a pull-back spring to pull the bearing away from the pressure plate during the 97 percent of the time that the clutch was not being disengaged.

Absent such a pull-back mechanism, a roller bearing in an MG will be in slight, but constant, contact with the pressure plate, so it is always spinning. All that spinning cannot be good for the bearing. There are a variety of cobbled-together pull-back mechanisms, but none of them are particularly well-engineered nor nicely compatible with the hydraulic release mechanisms in our cars.

The OE-style carbon bearings, while also in slight constant contact with the pressure plate, are self-lubricating, and the wear from such contact is minimal to zero, which is why the bearings tend to last as long as, or longer than, the friction material on the clutch disc itself. This action is similar to the lack of wear on disc brake pads, which constantly ride ever-so-slightly on rotors, but experience no measurable wear as a result.

Of course there's the occasional defective carbon bearing, as there occurs with most any type of part. But my preference is for the tried-and-true carbon bearing, which has served me and others quite well over the last half-century or so...

Dick



Errabundi Saepe, Semper Certi
(Often wrong, but always certain)

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Jan Kruber Avatar
Ballerup, Copenhagen, Denmark   DNK
It is very interesting to read the different elements of the theme.
Last winter, when I was doing the car, I was very inclined to replace the graphite bearing with a roller or ball bearing. I read a lot about it on the internet. There are some who are very pleased with the roller bearings, but it seems to me that the majority, at the time, just like now, prefer the graphite bearing. There are reports that the graphite bearing can last for as long as the clutch itselves, but of course, I do not know if it's fiction. I don't feel convinced yet, that's why I'm not ready for a roller bearing, I don't think I have seen enough evidence that it can give me value.
I will give the graphite device another try, I assume that there has been a defect in the delivered graphite bearing and will replace the defective parts with new including a new graphite bearing and hope for the best.
When it has worked for so many for so many decades, it may work for me too......



Mightymidget

CtMGDude John R
New Fairfield, Ct, USA   USA
I've read up a lot on this, and looked at a lot of pictures. There seems to be a more negative experience on the bearings when used on MGB's, as opposed to Midgets. Back to "Who the Hell knows?". I'd like to hear from Midget owners though. I have read people getting 40K miles out of these bearings, and though I have a quality Carbon T/O set up, I have been reading about a lot of the OEM style coming apart lately. I don't race my car, and to be honest, except for first gear, I often find shifting and proper use of the gas pedal involves shifting without using the clutch at all, much like on my motorcycle. I do use it downshifting, of course, and I don't ride the clutch on hills that have stop lights or signs, it is easy enough to use your foot to hold the car in place with the brake, and gear in neutral, while shifting and engaging in first takes but the smallest amount of time. After reading all this, I will stay stock, if I can get a quality OEM release bearing. It would be extremely easy to rig a return spring. Heavy Duty clutches do cause problems for bearings, from what I have read, but this seems to be more of an MGB issue. This is just from reading stuff from over the last 10 years. The concentric Hydraulic set up seems really sweet!! smiling smiley

Jan Kruber Avatar
Ballerup, Copenhagen, Denmark   DNK
I received an answer from the supplier. Han can't think of anything else, than there must be some constant pressure on the bearing from lack of clearance at the clucth peadlal. What do you think ofthat statement?
I have now reassembled the whole lot. Before fitting the clevis pin at the slave cylinder / release arm, I noticed, that the pushrod was in the outer position, but I could easily push it back in, but it goes out again slowly. So the kind supplier is right, there's some pressure on the bearing, but not much.
But isn't it normal, that there's a tiny pressure in the system, isn't it the plain nature of it?



Mightymidget

Speedracer Avatar
Speedracer Platinum Member Hap Waldrop
Greenville, SC, USA   USA
1967 MG MGB Racecar "The Biscuit"
FWIW, I have used roller bearings on both MGB and Spridget gearboxes for 4 decades, never had one fail. As Rick mentioned the arm moves in a arc, so it not always going to be centered in relationship to the input shaft , but for the most part it is centered on input shaft at the point of contact. I agree with John T. on most things, but this is not one of them.

Jan, you didn't show us any of the remains of the carbon material, was it big chunks, I am betting it just came unbonded, there was a rash of this a few years back with the MGB carbon T/O bearings.



Hap Waldrop
Acme Speed Shop
864-370-3000
Website: www.acmespeedshop.com
hapwaldrop@acmespeedshop.com



Edited 1 time(s). Last edit at 2017-07-17 05:19 AM by Speedracer.


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Jan Kruber Avatar
Ballerup, Copenhagen, Denmark   DNK
In reply to # 3553377 by Speedracer FWIW, I have used roller bearings on both MGB and Spridget gearboxes for 4 decades, never had one fail. As Rick mentioned the arm moves in a arc, so it not always going to be centered in relationship to the input shaft , but for the most part it is centered on input shaft at the point of contact. I agree with John T. on most things, but this is not one of them.

Jan, you didn't show us any of the remains of the carbon material, was it big chunks, I am betting it just came unbonded, there was a rash of this a few years back with the MGB carbon T/O bearings.

Hap,
Here's the shot you ask for, small fractions, especially in the release arm boot and in the "cup" at the end of the starter motor far left on the photo. You are right, the bearing was not packaged but lay unprotected in a plastic bag in the box along with the other clutch. parts.



Mightymidget


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