Duel Row Bearing Consensus ?

[manolo]

Originally Posted by Johnny Danger

I'm in similar situation wherein my vehicle only has 20k original miles.

As little as you drive that car, would you even notice if the IMSB failed?

[southernstar]

Dave S., that's an excellent price - one that is about $600.00 to $1100.00 less than I have been quoted. Did that include an LN bearing and a complete clutch kit? And JD, with about 2000 miles a year (and I am assuming annual oil changes before putting her back on the road in the spring), I suspect your IMS bearing is looking as good as the rest of the dangermobile!

Brad

[thom4782]

My 2 cents.

I believe that IMS bearings fail when lubrication becomes inadequate due to a leaking flywheel side seal. If my belief is correct, I can only guess that dual row bearings failed less often than single row bearings because the dual row seals were better due to either design, manufacturer or assembly.

In any event, perspective is important. With single row bearings, replacement is like buying insurance against a 1 in 10 possibility of a very costly failure. The so-called insurance premium is roughly $1700 to replace the IMSB. The risk is approximately $5000 to $10,000 to replace a failed engine. Seems like a high premium to me. The probability weighted risk drops to between $500 and $1000 (10% failure probability x $5000 to $10000 engine replacement costs. So in the sterile world of probabilities, its a $1700 premium to avoid a $500 to $1000 loss.

With a double row bearing, the odds of failure improve to 1 in 100. Given the difference in odds, a IMS dual row bearing replacement is an even higher premium to pay compared to the single row bearing situation. This is because the cost to replace the IMSB is the same, but the probability weighted risk drops to 1 % of $50 to $100. Like all cases with insurance, the probability weighted numbers mean little if your engine dies due to an IMSB failure.

So this brings me to my answer to JDs question. I might replace a single row bearing as a preventative maintenance measure. I would only replace a dual row bearing at the time of clutch replacement with one exception. I would replace dual row bearings in cars with low annual miles or infrequent oil changes. These latter conditions allow increase oil contamination and degrades the seals more quickly.

Hope this helps.

[southernstar]

Thom, there is no direct correlation between oil contamination and lower mileage, especially if the car is driven is for more extended runs, rather than the short, in-town, stop and go daliy trips that many higher mileage cars are regularaly subjected to (let face it, that does tend to contaminate the oil). For vehicles that are winter-stored (as Johnny's seems to be), it is of course important to change the oil each spring before putting the car on the road. My car is driven largely as described for about 4-5000 miles a year before winter storage, followed by an oil/filter change each spring when she is put back on the road. I have a magnetic drain plug and also cut open the filter to check for particulate matter. Simply put, the oil that is drained out each spring looks virtually indistinguishable from new.

My BMW X3 is driven year round and not only gets much higher annual mileage, but a higher percentage of its trips are of the stop and go variety. The factory recommends oil changes every 25,000 km (about 15,000 miles) and I can assure you, when it goes that long the oil looks quite dirty in comparison. I would far rather have a lower mileage car that has had its oil changed every 5000 miles at most, than a higher mileage daily driver that has had its oil changed according to Porsche's recommended schedule!

Brad

[southernstar]

Hey JD, I just noticed that you have entitled the thread 'duel', rather than dual. After reading the disparity in opinions (and considering the fact the dangerman no doubt regularly engages in duels), I am beginning to understand why!

Brad

[Johnny Danger]

Originally Posted by southernstar

Hey JD, I just noticed that you have entitled the thread 'duel', rather than dual. After reading the disparity in opinions (and considering the fact the dangerman no doubt regularly engages in duels), I am beginning to understand why!

Brad

Must have been a Freudian slip ?

[EssexPorsche]

Thom,
It's not about the money, it's not about the price tag( sorry got all a bit Jessie J there)
You can't price the pleasure these cars bring nor can you evaluate peaceful sleep.

People can post all the maths they like but if you are a risk averse guy and love your 986 ... It's irrelevant .

As I said before the whole subject is emotive and very much a personal perspective.
There is no right are wrong. There are informed opinions, there are no doubt biased opinions, there is for sure plenty of hear say. All anyone has to do is reconcile their own course of action with themselves. Whether that be the wife or the wallet who cares.

It's easy for me to say because I made my choices based on who I am and what my car means to me.

No wonder the prices of 986s is @rsing out if all people read is this stuff when looking to buy.

Come on guys, we all know what's what now. Make your choices, pony up or pipe down so we can get back to the fun stuff!

[Johnny Danger]

Originally Posted by manolo

As little as you drive that car, would you even notice if the IMSB failed?

The windows wouldn't go down right ?

[southernstar]

The windows will, but the hottie in your picture probably wouldn't when she finds herself stranded road-side in a car with a smoking pool of oil beneath it!

Brad