[MartinWake]

Hey guys I need rob bearings for my n55 2011 bmw coupe I just want to ask where I could get some not that expensive because its for the meantime until I get a engine swap. :/

[SnapCoupe]

Originally Posted by MartinWake

Hey guys I need rob bearings for my n55 2011 bmw coupe I just want to ask where I could get some not that expensive because its for the meantime until I get a engine swap. :/

Do you plan on replacing the rod bearings and then swapping a new engine in later on?

When my rod bearings spun I was told that the replacement of them, while possible and not too difficult by going through the oil pan, would be a roll of the dice. Theres a chance everything can run fine, but theres also a chance that the motor can seize up again a few miles down the road. Apparently when these motors spin a bearing the crank journal tends to warp.

Tread carefully if you go down this route.

[MartinWake]

Originally Posted by SnapCoupe

Do you plan on replacing the rod bearings and then swapping a new engine in later on?

When my rod bearings spun I was told that the replacement of them, while possible and not too difficult by going through the oil pan, would be a roll of the dice. Theres a chance everything can run fine, but theres also a chance that the motor can seize up again a few miles down the road. Apparently when these motors spin a bearing the crank journal tends to warp.

Tread carefully if you go down this route.

its my dads mechanic he will install the rod bearings for cheap so I can drive it to my house and then to another shop for the engine swap just so I dont have to pay so much towing do you have a site for these rod bearings?

[weehe126]

Replace rod bearing for less than a tow, good luck with that.

[MartinWake]

Originally Posted by weehe126

Replace rod bearing for less than a tow, good luck with that.

for more then 1 tow and if I fix this engine that I can use it as form of payment too so the new engine will be cheaper

[Sd335i2007]

What kind of engine are you gonna swap into it? Just curious

[MartinWake]

Originally Posted by Sd335i2007

What kind of engine are you gonna swap into it? Just curious

LS... jk imagine that lol, no just another n55 :P

[bbnks2]

Originally Posted by MartinWake

Hey guys I need rob bearings for my n55 2011 bmw coupe I just want to ask where I could get some not that expensive because its for the meantime until I get a engine swap. :/

Summit racing sells king rod bearings for $23.99. EBAY has the shells as well at marked up prices.

Take note that these are builder bearings. BMW uses custom bearing shell colors to get within .0001" of their target bearing clearance. The correct bearings for your motor are printed on the block and crank. Without using these custom shells, or cutting the crank for custom clearances, you may end up being .0001-.0003," or more, tight or loose on each journal when using the builder bearings. Meaning, one journal might measure out to .0012" and one might measure out to .0018." Your motor will still run just fine like this and people do it all the time, but, it's not ideal at all. BMW uses those custom shells to get dead on at around ~.0015" on all journals. Their machining and precision is very accurate despite people's claims.

The other issue is that once a bearing has begun to deteriorate there could have been irreparable damage done. The crank could be scored and flakes of metal will have made their way throughout the motor. Swapping bearings is usually only reserved for instances where you catch bearing wear before total failure occurs. However, that doesn't mean that it won't work either. Clearance is clearance. So long as your mechanic ensures the crank journal is still "good enough" the repair should be good for a while for a lightly driven car. The actual service limits for what is considered to be usable are pretty wide at .0007" to .002." The question is whether you distorted the rod bore, destroyed the crank journal, bent the crank, threw out the line bore, etc... Only a mechanics mic will tell you that.

[TheMidnightNarwhal]

But I don't understand. If your car will run fine with new rod bearings why put in a new engine.

[Pladi]

Originally Posted by TheMidnightNarwhal

But I don't understand. If your car will run fine with new rod bearings why put in a new engine.

Its all about that clearance that was mentioned. IT can run fine for a short period of time.

If you dont have those clearances good you can rebuild an engine with all new parts and a factory engine with 150k will last longer. Thats why i always tell people a used engine is a no brainer

[TheMidnightNarwhal]

Originally Posted by Pladi

Its all about that clearance that was mentioned. IT can run fine for a short period of time.

If you dont have those clearances good you can rebuild an engine with all new parts and a factory engine with 150k will last longer. Thats why i always tell people a used engine is a no brainer

Oh ok, I would've thought if something was out of spec even by a small amount the engine wouldn't run normally for even a minute before seizing again or failing.

As for fixing instead of replacing, I had you thought to but then I looked at parts for fun and like a new crankshaft is almost as much as a used engine, I think that's why people are not fixing it.

[Pladi]

Originally Posted by TheMidnightNarwhal

Oh ok, I would've thought if something was out of spec even by a small amount the engine wouldn't run normally for even a minute before seizing again or failing.

As for fixing instead of replacing, I had you thought to but then I looked at parts for fun and like a new crankshaft is almost as much as a used engine, I think that's why people are not fixing it.

yeah multiple factors.

[MartinWake]

Originally Posted by bbnks2

Summit racing sells king rod bearings for $23.99. EBAY has the shells as well at marked up prices.

Take note that these are builder bearings. BMW uses custom bearing shell colors to get within .0001" of their target bearing clearance. The correct bearings for your motor are printed on the block and crank. Without using these custom shells, or cutting the crank for custom clearances, you may end up being .0001-.0003," or more, tight or loose on each journal when using the builder bearings. Meaning, one journal might measure out to .0012" and one might measure out to .0018." Your motor will still run just fine like this and people do it all the time, but, it's not ideal at all. BMW uses those custom shells to get dead on at around ~.0015" on all journals. Their machining and precision is very accurate despite people's claims.

The other issue is that once a bearing has begun to deteriorate there could have been irreparable damage done. The crank could be scored and flakes of metal will have made their way throughout the motor. Swapping bearings is usually only reserved for instances where you catch bearing wear before total failure occurs. However, that doesn't mean that it won't work either. Clearance is clearance. So long as your mechanic ensures the crank journal is still "good enough" the repair should be good for a while for a lightly driven car. The actual service limits for what is considered to be usable are pretty wide at .0007" to .002." The question is whether you distorted the rod bore, destroyed the crank journal, bent the crank, threw out the line bore, etc... Only a mechanics mic will tell you that.

Yeah thats why I would only do this temporary the mechanic told me something similar and I thought of it too, rebuilding an engine wont be the same as having it all done super precise from factory and are these the ones you said ?

https://www.summitracing.com/parts/k...ions/year/2011

[bbnks2]

Originally Posted by MartinWake

Yeah thats why I would only do this temporary the mechanic told me something similar and I thought of it too, rebuilding an engine wont be the same as having it all done super precise from factory and are these the ones you said ?

https://www.summitracing.com/parts/k...ions/year/2011

Yes.

Looks like since they've been restocked a ton are up on Ebay now too. They were out of stock for a few months and prices really went up.

[bbnks2]

Originally Posted by TheMidnightNarwhal

Oh ok, I would've thought if something was out of spec even by a small amount the engine wouldn't run normally for even a minute before seizing again or failing.

As for fixing instead of replacing, I had you thought to but then I looked at parts for fun and like a new crankshaft is almost as much as a used engine, I think that's why people are not fixing it.

Cranks can usually be cut/polished back to "spec." You then run undersized bearings to get back to factory tolerances.

The issue with slapping new bearings into a car with rod knock is that the crank is not being taken out of the car to be cut, polished, checked for straightness, or magnafluxd to check for cracks. Just slapping in a new set of bearings also doesn't flush out loose bearing material... These can all cause instant failure. Bearings generally don't get destroyed without also causing damaged to the crank surface.

An engine with .001" of clearance on one rod and .002" of clearance on another rod isn't going to blow up, but it obviously is not going to have ideal harmonics either. You might be fine cruising on the highway but over time and high revs it might tear itself apart... I am no expert but there is a reason why BMW uses various shell sizes to get dead on clearances rather then leaving them off by a few thousandths...

People do rebuild engines. Like said above, cranks can usually be repaired. Ghassan rebuilds them all day. But yes, a damaged crank shaft is a killer to a rebuild budget. Ask me how I know. Mine came back CRACKED after I spun bearings. There is cost benefit to everything. Doing the work myself I spent a little more than what a used engine would've cost me. Except, now I have a brand new forged engine instead of someones old unknown used junk...

[feuer]

bbnks2 did Ghassan rebuild your engine? If yes, I'm not really surprised that crank returned "cracked". Never mind. I are-read. You DIY it. My man. I just had one done too. Bearing are all the same in size. The color scheme is difference in weight and to identify top from bottom. Is done for balancing, not clearance as they are all 56mm in size. New TIS says BMW stopped using violet-blue combination so only yellow-red now. You are correct: these are built very precisely, but they still fail. A lot of modern BMW engines experience bearing failures. So changing the rod bearings on an engine with rod knock that hasn't seized is just as optimistic as swapping used engine and expecting to last.