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I sketched a diagram (not to scale) trying to visualize the thrust control. I don't have the actual bearing kit in my hands so the drawing is solely based on my best guess from various photos and videos.
Basically the center stud, the inner sleeve, and the IMSB flange (i.e., all the green parts) form a single stationary piece that's bolted to the engine case.
The bearing has no inner race. The outer race is "glued" to the IMS using red loctite (all the orange parts rotate as one piece). The rollers (blue) are in between the orange and green parts to provide radial support and the rollers "float" horizontally.
When there's thrust, the orange and green parts try to move horizontally relative to each other but their positions are restrained by the center stud, the yellow washer, the outer race, and the flange with all the smooth surfaces rotating against each other in the presence of oil. They all shoulder the axial thrust load. Basically the outer race face surfaces are used as plain bearings
Oil is force fed from the other side of the IMS, or alternatively it can be splashed lubed on the bearing end.
If the above sketch by Ahsai is correct than I can see two issues:
1. The red locktite bond is not going to last long given axial thrust forces on IMS. Even thermal expansion. The shaft has to go somewhere and locktite is not going to take that load.
2. The force feed lubrication. The IMS will fill with pressurized oil but I can't see any passages to lubricate the bearing other than surface imperfections between the outer bearing race, Center stud and washer.
1. Agreed. I am surprised a circlip is not used too but there seems to be no space for it. Also their installation steps and the photos of the kit also do not mention any circlip.
2. The washer has grooves cut on it, similar to the crankshaft thrust bearings. The oil passes through the rollers then to the flange, which has a V groove for oil to escape. So I think oil can get to all those parts with no problems.
Hope Rod can clarify. Last thing I want is to spread false info.
Originally Posted by Luxter
If the above sketch by Ahsai is correct than I can see two issues:
1. The red locktite bond is not going to last long given axial thrust forces on IMS. Even thermal expansion. The shaft has to go somewhere and locktite is not going to take that load.
2. The force feed lubrication. The IMS will fill with pressurized oil but I can't see any passages to lubricate the bearing other than surface imperfections between the outer bearing race, Center stud and washer.
"Dr" haha, I wish If my thinking is right, the reason it can't use a circlip is because it needs the outer race to be able to slide on the flange as a plain bearing to support thrust. The circlip will be in the way.
I also wonder why a separate washer as opposed to enlarging the "base" of the stud. I figure maybe the internal profile of the IMS doesn't allow that.
Also note the roller cage is recessed and is not touching the washer or the flange so only the flat faces of the outer race bear act as a plain bearing to shoulder all the thrust load. That's quite an interesting design.
So when this pressurized oil fills the IMS tube, what kind of pressure is that putting on the bearing as it spins and acts as an accumulator? What about the pressure on the 4 piece press fit IMS tube assembly? The 4 piece IMS tube is merely press fit together with no glue or welding. Other solutions use a plug in the IMS tube to prevent the tube from filling with oil for this reason.
I see a lot of people talking about forces but I don't think anyone has measured these forces to determine how robust one of these need to be afaik.
What we know at this point is that Vertex IMS has been in use since 2012 and still going strong.
Maybe they can chime in on how many of these have been in circulation, under what types of environments/circumstances, and what types of testing was carried out.
I foresee a big initial hump to get over but after that it should be rewarding and hopefully they can set the cruise control.
So when this pressurized oil fills the IMS tube, what kind of pressure is that putting on the bearing as it spins and acts as an accumulator? What about the pressure on the 4 piece press fit IMS tube assembly? The 4 piece IMS tube is merely press fit together with no glue or welding. Other solutions use a plug in the IMS tube to prevent the tube from filling with oil for this reason.
My guess is the pressure is quite low as the hole they punch is 1-2mm in diameter.
I see a lot of people talking about forces but I don't think anyone has measured these forces to determine how robust one of these need to be afaik.
What we know at this point is that Vertex IMS has been in use since 2012 and still going strong.
Maybe they can chime in on how many of these have been in circulation, under what types of environments/circumstances, and what types of testing was carried out.
I foresee a big initial hump to get over but after that it should be rewarding and hopefully they can set the cruise control.
Wow, you're actually able to read every word in those long paragraphs. Kudos.
Still interested to see how many are still in "circulation". They mentioned 1,000 sold but wondering how many of those 1k are still around(no failure rates mentioned).
I can see this kind of product having more faulty installation possibilities and now can understand why Jake has improved on and developed his "faultless" tool to remove one more equation to bad publicity of a product although it may not actually have been the product to begin with.
One aspect I'm interested in is if they've tested this without any oil flow to the bearing and for how long. This will matter for track junkies that may encounter loss of oil pressure in certain racing conditions at near redline for example.
I would like to know if they've dissected one of these bearings on a high mileage used car and see if there were any wear patterns or markings anywhere on the bearings and associated parts as well.
Since I deal with studies and statistics all the time, here's my take on this:
According to the only statistics with a large enough sampling to be considered halfway reliable, the class-action-suit stats, even the OEM small single-row IMSB left untouched has only an 8% failure rate. That's the original, low-load-capacity sealed steel bearing where the seal gets breached, filled with dirty oil turning the grease into grinding paste. Only an 8% failure rate. 92% of cars with the weakest most ill-conceived IMSB fitment do not fail.
All a "solution" needs to do is reduce the probability of failure by a measely 8%.
Since I deal with studies and statistics all the time, here's my take on this[...]
All a "solution" needs to do is reduce the probability of failure by a measely 8%.
The underlying assumption you're making - in error - is that a fixed percentage of bearings will fail. Since it is now (commonly) considered a wear item, the number of original single-row bearings that fail will increase over time. Your 8%, or 10%, or whatever number - if it was EVER accurate, was accurate only for a moment in time.
Every M96 - assuming it's not in a museum - will eventually experience a failure. Since the single-row bearings are a known weak point in the engines so equipped, more single-row bearings will fail over time. Even some single-row retrofit bearings - though the cause is often attributed to improper installation or installation into a poor candidate, have failed. Claiming that there is a known - and fixed - percentage of bearings that will fail is a fallacy that continues to be tossed around here.
This reasoning is as sound as assuming that if, as of today, 42% of 996's have had to have windshield wiper blades replaced, we know with absolutely certainty that 58% of 996's will have perfect windshield wiper blades...forever.
To my understanding the statistic of 8% which was cited in the class action was actually 8% of the bearings failed within 100,000 miles. Without knowing the median value the statement is meaningless, a median value of 10,000 miles is vastly different from a median value of 90,000 miles. If the median value was 10,000 miles it would mean that here would be very little chance of the bearing failing after 100,000 miles. Without knowing that median value, we are essentially clueless.
Without knowing that median value, we are essentially clueless.
Yup. The numbers in the settlement info were a simplified estimate of a number at a point in time with no supporting data.
If the total number of failures was a known, static number, there would have been no need for the years-in-service limitations. So we're pretty much left holding puds and guessing, and the aftermarket supplier data (which consists of "my bearing is better than yours, and my d**k's bigger, too) doesn't really help us out much.
Guys, let's not veer off track too much from the original topic regardless if it's the RL way. I'm hoping Rod can chime in soon with more answers to our questions.
09-22-2015, 12:55 AM
