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MG Midget and Sprite Technical roller thrust bearing. BBS discussion at MG-Cars.net
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MG Midget and Sprite Technical - roller thrust bearing.
| Hello Gentlemen I am considering pulling my engine and replacing the carbon thrust bearing with a roller type. (I have heard many horror stories about the logevity and reliability of the Carbon types available today) I have been looking at a unit designed and made by one Alan Anstead which looks appropriate. I have also seen others, one a device made in Australia, and others which are home sprung. Any application advice or experience with any of these devices would be welcome. Thanks Bob |
| R C Skerritt |
| I looked at Alan's devices at the Restoration show, they look ideal to me I bought a similar device from a well known performance centre but it was unusually heavy and never worked very well with my 5 speed conversion and is mostly the reason I went with a concentric layout If you want to stay 'normally operated' I would not hesitate to say go for it Alan may come in shortly and tell you a bit more but I expect you have already done plenty of research :) |
| Bill sdgpM |
| I remember Alan's design. It was very close to Lawrence's home-brewed solution and very elegant. It's in the archive somewhere but I can't find it. FWIW if I were doing this on an A series I'd go with Alan's kit. I have a 1500 so I have no axe to grind but I'm sure some of the A series gurus will be along shortly to help. Good luck Bob. |
| Greybeard |
| The roller works fine on some types of cars and poorly on others. There are two reasons to retain the carbon thrust bearing: 1/ It is designed to wear, this is to compensate for the wear on the clutch linings. without this, the clearance would need adjusting more often. On modern cars there is some sort of automatic wear take out system on the pedal. 2/As the bearing moves in and out it traces an arc, this means that it is only centered in one position, this could cause failure on roller bearings, however the carbon can handle this misalignment. Again on modern cars the roller bearing is constrained to move in a straight line by a tube around the primary shaft. |
| J MacDonald |
| Some more info can be found at the following link http://tinyurl.com/l8km7ju |
| simon (1275 mk4 sprite) |
| Wear of a carbon thrust isn't needed to "compensate for wear in the clutch lining." It's an hydraulic system which is itself fully self adjusting. There is no means or need for manual adjustment. All that happens as the lining wears is that the slave piston gradually begins to operate over a slightly different section of the cylinder bore. It's correct that the release bearing movement is excentric as the arm sweeps through an arc, but this is very slight given that the tangential movement needed to release the clutch is barely 1/2". The problem is that with wear and slack in the pivot point of the arm the weight of a roller bearing can pull it down well and this is the main cause of the bearing being off centre. If the pivot bush is in good condition, and is assembled carefully with shims if necessary, then the heavier roller bearing is no problem and Alan's is a neater and better designed version than most other offerings. |
| GuyW |
| I've recently fitted one of Alan's roller thrust clutch bearings, and can confirm that it is an easy fit, and of excellent quality. Ensure the fork arm bushes and pivot bolt are either replaced or in good condition (I replaced mine). Overall highly recommended. John. |
| John Hutton |
| I'm still wondering what to fit when the time comes. The Frog will have a 1275 clutch (and engine) and the ribcase box I have rebuilt came with an as-new carbon release bearing (don't know the quality). So, whether to give it a go or not? I think it will be a year or so before I fit it, so plenty of time to think about it...... Bill |
| W Bretherton |
| Thanks for the endorsements. Lawrence Slater made a 1275 roller release cobbled together from a couple of bolts and laminated steel plate. I have the benefit of a small Myford lathe and thought that I could make a tidier looking version. Lawrence and I got together and found that our actual bearings were different. Lawrence suggested that my version was good enough to offer to others. Demand was such that I have made a welding jig and another tool to aid production. My lathe soon gave way to CNC machining of spigots and backplates. The roller release bearing sits on a backplate with two spigots. The actual bearing is a commercial make easily obtained. The distance from centre spigot of the assembly to the facing is the same as the carbon thrust. The complete unit is a direct swop for a stock carbon thrust. Nothing needs modification. The bearing is self centring. If the clutch yolk (fork) is undamaged and the spring clips good there is no droop. The design can be carried over to the 1098 engine but not 948. If used with older 'pigtail' spring clips shimming to stop sideways movement May be required. If fitting to a Type 9 conversion the tube covering the input shaft on the gearbox needs to be removed. A Quentin Hazel clutch cover used as it has a large centre hole to allow the input shaft through. A holed rather than slotted yolk (fork) pivot is preferred. For the 1098 and 948 I fit a deep groove ball bearing into the original cast body of a carbon release and then fit a steel facing. So for the 1098 there are the two options: as per 1275 or deep groove ball bearing. Not all original carbon release castings are suitable for conversion but for the 948 the thick (14mm) casting with the roll pin, that has a bad reputation for shedding it's carbon, is most suitable for conversion. Quality is so 'good' that some need boring to fit the bearing whilst others need shimming. I am about to do a run of 1275 units next week if anyone wants one. alan dot anstead at btopenworld dot com. A plug for Daniel Stapleton's new tuning book where my release can be found on P83. Alan |
| Alan Anstead |
| I have had Peter Mays Roller release bearing for about 10 years now, after a new carbon one disintegrated, its been now problem at all. The car only does about 1000 miles a year however. dave |
| Dave Barrow |
| Whatever you do, don't buy the Morris Minor roller release bearing. It fits, but it's too heavy for the Spridget hydraulics. I've still got mine somewhere, as a loser's trophy. |
| Nick and Cherry Scoop |
Picture of 1275 roller release mounted for display.
 |
| Alan Anstead |
| Would I be foolish to leave an as-new carbon release bearing in? Bill |
| W Bretherton |
| Hi Bill, As far as I recall the original carbon ones were fine for a reasonably high mileage. Problem arose with certain aftermarket replacements, and not all of them. There was a batch of them that were notorious for disintegrating fairly quickly. I remember the identifying feature was that they had a small hole in the carbon part. Something to do with a split pin that was used to retain the carbon maybe? I think there was a write up in Mascot some years ago. Alan Anstead would probably know as he compiles a technical index from time to time. Come to think of it, its fairly likely that Alan wrote the article that I am so vaguely recalling! |
| GuyW |
| Be aware that the hight of the bearing plays an important role in the way the clutch engages. as guy writes: It's correct that the release bearing movement is excentric as the arm sweeps through an arc. But what part of the arc is essential for a nice working clutch. In the photo you see my collection of different bearings. It took some time, 3 clutches and 3 times motor in and out til I found the right one.  |
| Flip Brühl |
| Thanks Guy, that's useful information. I'll try to identify what mine is. It's this general problem of many current aftermarket parts that seem to be sub-standard, which is quite depressing. |
| W Bretherton |
| The hole in the potentially rubish one I have was for a 'roll pin'. |
| richard b |
| Yes Guy I brought up eccentric (travels in an arc) in the 4th post. I stated 2 general arguments that can be used against the bearing over the carbon, for general information. Reason 1 does not apply to hydraulic actuation, but reason 2 might, depending on the throw or amount of are or eccentricity unique to a specific design. I am not aware of any other arguments against bearing over carbon. The more arc the more likely you will experience problems with the bearing, but even a broad arc in a low performance situation might work. On the other hand a small arc in a high performance situation might not work well. Therefore reports from people on how well this might work in their car should include what type of performance situation exists in the engine; for if we all have the same arc, that is all that matters, i.e. is it with a screamer or stock engine that you find the bearing working well? |
| J MacDonald |
| Good post Flip. |
| Greybeard |
| TBH there can't be much of an arc, due to the small movement at the slave cylinder and the pivot point of the arm, the bearing can't be moving much more than 1/4" |
| Dave O'Neill 2 |
| Gb, people only hear or read what they want to hear, not what's actually written. Dave that is true, the problem is when it comes in at a slight angle. Arc or eccentric is how far bearing/carbon is from pivot point. |
| J MacDonald |
| A picture of a 948 carbon release casting: the type fitted originally with the roll pin: fitted with a deep groove ball bearing and then a 'faceplate'. Alan  |
| Alan Anstead |
| 1. No matter how small the arc of fork operation, the axis of the thrust plate on the clutch cover will not be aligned with the axis of the release bearing - this is why commercial roller bearings are fitted with a teflon facing (unless it is an axial arrangement as per the Ford type 9 or the 1500 midget) - this misalignment will generate heat and lead to wear as there is otherwise no lubrication. 2. Unless there is a clutch cylinder pull off spring, the bearing will always be in light contact with the thrust plate - not a problem with the carbon bearing that is heat insensitive - but for the roller bearing the heat generated by the misalignment and the constant rotation will dry out the prelubricated bearing - this is why so many of them squeal. These things are of little consequence for low mileage use but for reliability I prefer to stick with the carbon bearings. In my experience the carbon bearing lasts as long as the clutch plate and cover springs so having to change the whole set is no problem - so what is the advantage of the roller bearing? I doubt whether you would actually recoup the cost of the bearing over the lifetime of your use of the car unless you do really high mileages. I reckon on a clutch change every 60,000 miles on average. |
| Chris at Octarine Services |
| This is my reason, Chris. I think the issue is just modern poor quality, otherwise I would use carbon.  |
| Nick and Cherry Scoop |
| That bearing has well and truly released Nick! |
| W Bretherton |
| Yes - but that level of wear suggests to me that the carbon had worn down to the cast iron casing quite some time ago - the cast iron, due to its high carbon content, will quite happily continue to function as a bearing until worn right through or the forks hit the cover fingers! I only ever fit Borg & Beck clutch units complete and have never had an issue with poor quality. If you really want to go roller bearing then convert to concentric slave cylinder. |
| Chris at Octarine Services |
| Yes - but that level of wear suggests to me that the carbon had worn down to the cast iron casing quite some time ago - the cast iron, due to its high carbon content, will quite happily continue to function as a bearing until worn right through or the forks hit the cover fingers! I only ever fit Borg & Beck clutch units complete and have never had an issue with poor quality. |
| Chris at Octarine Services |
| No, it was a new one, Chris. Just unlucky, I guess. The level of wear was due to the driver's attempts to use the clutch after it had broken (not I). I then tried a Morris roller, which was too heavy, then back to carbon, which was fine until I sold the car. Together with the fact that during the build I put the fork in the wrong way round, then damaged the gearbox tail seal swinging the engine/gearbox over the cross-member, that was engine in 5 times and out 4 times in the first year. Released is the right word, Bill. |
| Nick and Cherry Scoop |
| Nick I would not limit the quality problem to "new" parts. I recall getting these clutch parts as a "kit" from BMC in the '60's and having the carbon fall out when I picked it up. Always want to check all clutch parts well for problems before install. I always figured the roller bearing convert was for racers who take the engine and tranny apart every couple years. What keeps the roller bearing lubed in such an enviro for prolonged periods? |
| J MacDonald |
| The roller bearing I use / make for 1275's uses the bearing from a major motor manufacturer's diverse range of motor vehicles. Do they recall each year for a change of roller release? The deep groove roller bearing I use to convert the carbon cast bodies for 1098 / 948 is sealed. It's spec far exceeds that required for a Sprite or Midget. I don't take my engine out every year for to replace my roller release either. |
| Alan Anstead |
| Unless you are in the habit of "riding" the clutch then the amount of time the release bearing is actually spinning and under pressure isn't that much anyway. No reason why a sealed for life type bearing shouldn't last many years/ miles. |
| GuyW |
| Guy, There is a spring inside the slave cylinder that pushes the release bearing into contact with the cover thrust plate - therefore it is spinning all the time to some extent. |
| Chris at Octarine Services |
| Alan, yes I presumed it was a double rubber sealed bearing. You put on how many miles a year? Stock engine power or much more? I never said anyone would have to replace it every few years, just that I had always figured the convert was for mainly racers who did that anyways. And Guy I understand riding clutch causing troubles in either setup, but the location of where the carbon or bearing resides in is a fairly hot enviro, thus my curiosity about reliability of lube. The hot. Would it not be hotter there than where wheel bearings live? I think the thought of leaking grease from a hot bearing seal onto the friction material might cause pause for some. No doubt it seems to generally work fine for many people, I am more curious about the situations where it does not work well, and why. |
| J MacDonald |
| Chris, Maybe some or even many do. Mine didn't have an internal spring. But the piston only goes as far back as the "train" of components: clutch fingers, release bearing, clutch arm and pushrod will push it so in theory they should all still be making light contact with or without that internal spring. (Not quite relevant here as we are talking about Midgets, but at least some Morris Minors have the opposite - a spring attached to the end of the lever arm to pull it back clear.) These days I have a concentric slave system anyway, and that does run with the bearing (roller) in constant direct light contact as well. My point was that even if spinning, the bearing is only "spinning AND under pressure" for a relatively short percentage of the overall operating time. Continuous spinning with little load is probably a better thing than sudden furious acceleration from zero rpm up to 5,000 rpm every time you change gear! |
| GuyW |
| I think that the "Arc" argument is fairly insignificant. With a release bearing throw of around 1/2" the lateral movement as it travels through the arc is +/- 70 thou (0.070") Deduct a bit of clearance on the pivot and carrier and the bearing should pretty well self centre. I still believe that more significant is misalignment due to the clutch arm "drooping" under the weight of the release bearing accentuated by worn or slack pivot points. This is likely to be more than 70 thou off centre at the bearing position. Nick's photo demonstrates this perfectly. The bearing carrier is worn away entirely at the upper side as it has drooped down and off centre. The other factor not yet mentioned is that the clutch fork arms are fairly notorious for bending. Whilst this is generally in the for/aft plain I suspect that some may show a twist as well, pulling the bearing carrier off centre. Worth checking for when fitting either a carbon or a roller bearing. Try putting a close fitting rod through the pivot bush and check that it lies parallel to a bar laid through the bearing support forks. |
| GuyW |
| Hard to see where the bearing sits in 'relaxed' mode. But I would guess that anything heavier than the carbon bearing will begin to nod slightly with the turning of the clutch, and move off just a little. In the case of my huge Minor bearing it moved back a long way, and had to be pumped forward before the clutch could be used. But only after perhaps half an hour's driving. |
| Nick and Cherry Scoop |
With the "Arc" argument it is not the travel but the place the arc starts or ends that gives alignment or not. If not aligned the pressure group starts to wobble. That was the reason I had to change to an other bearing with different hight dimensions. Wobbling gives scars on flywheel and pressure plate. I have driven a Peter May roller bearing for years with no problems. But when I changed from a diaphragm to a conventional clutch the alignment was the problem.
 |
| Flip Brühl |
| Yes I do see that point as well Flip. For a lateral movement of only +/- 0.07" to be caused by the arc, it does assume that the bearing is correctly aligned at the mid point, half way along its travel. So it does need to be set up in the first place to achieve this, using the correct length of carrier and bearing. The problem is how to work out which one will get closest to achieving this with, as you say, a whole range of different options available as in your photo. My concentric slave where the bearing simply moves in a straight line doesn't suffer this problem! |
| GuyW |
| A batch of ten for 1275's. A couple are still available. Alan  |
| Alan Anstead |
| Alan Do you have any roller thrust bearings please in stock or due for production? I am looking for a 948 one (that would work on a 1098 too?) and perhaps a1295 one to go in the spares box for an engine upgrade later. Thanks Mike |
| M Wood |
| I welded together a carrier from laminated sheet and rod steel. The bearing is the Ford/Mazda one. One of the best mods I have done - over 10,000 miles and totally reliable. As others have found, I could not buy a carbon one that wasn't utter crap. This was not a problem in the old days, they were 'fit and forget'. The eccentricity is not a problem with the oil mist in my bell housing! Les |
| L B Rose |
| Mike I stopped making the 948's. The problem was sourcing suitable carbon bodies to modify. Not all can be modified then those that are are all over the place dimensionally - some needed a liner prior to boring. You can't use a 948 Crb on a 1098 as they have different offsets. The 948 from centre of spigot to carbon face is 1/2" whereas the 1098 is 3/4". I have some 1275 Carb's on the shelf. alan dot anstead at btopenworld.com. Both my 948 and 1275 are still rolling along on my CRB's. |
| Alan Anstead |
| John Twist says no: https://www.youtube.com/watch?v=4KIdkOWVcGg I have never heard of a roller bearing working out. But, I never got more than 25,000 miles out of a Ribcase clutch anyway. The Rivergate has been more reliable. |
| Glenn Mallory |
| Glenn.
I wonder what experience Mr Twist has and how many types he has actually used. He certainly has no experience of my one. Here in U.K. roller release bearings are well established. Each to their own experience and opinion. The carbon release has proven itself on many makes and marks over many years. That is until recently. Whilst I would be happy to fit NOS carbon release I would shy away from modern imports. As said above both of my Sprites run, all over Europe, happily on my homemade roller release bearings. Perhaps ' Don't knock it until you have tried it'. Alan |
| Alan Anstead |
| I agree Alan. The repro stuff is poor quality. I have a NOS one that has been in there for a few years now. I had a repro one that was incorrectly made and caused no end of problems. |
| Bob Beaumont |
| The reason why John Twist is wrong is in the mathematics. He is correct in that the release bearing moves in an arc so cannot stay truely concentric with the clutch. But firstly,from the point that the release bearing "engages" with the spinning clutch to full disengagement, is about 10mm of forward travel. The sideways displacement this creates as it moves through this small section of an arc works out as around 1.5mm or 0.75mm offset either side of the centre line. But more significant is that as the bearing and the clutch make contact and rotate there is sufficient slack in the assembly that they will pull themselves into a true concentric alignment and maintain that as the clutch is fully depressed. |
| GuyW |
| I have a roller bearing for the Ribcase in my stash, there with the removed Ribcase and associated parts. I didn't have a chance to try it once I installed the Datsun 5 Speed. I believe that it is encased in plastic.
The Rivergate conversion uses a roller release bearing that is also swung by an arm (not concentric). It has lasted reasonably well and is not grainy when properly adjusted. I would have tried the roller bearing had the 5 Speed not come along. I am the original owner of the car (1971) and in the first 200,000 miles of use, I experienced nothing but short life with the carbon release bearings, not to mention the time a total bearing disintegration at a stop light tried to strand me 1,200 miles from home. I drove it back without a clutch and the 1st gear in the Ribcase rattled badly after too many poorly synchronized pulls toward 2nd. |
| Glenn Mallory |
This thread was discussed between 28/04/2017 and 13/07/2020
MG Midget and Sprite Technical index
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