.25 oversize or undersize? Same thing?

[SnowBird]

Getting my crank micro polished, and figured Id put in new bearings, theyare .25 but I dont know if there is a difference in over or under. I see how they could call the crank undersized, but not the bearings. Im guessing I shold have the shop see what the mains are on the crank also since it didnt come with bearings. Thanks in advance.

 

[absolute_DSM]

What do you mean by they are .25?

Crank mains or rod journals made any way smaller use oversized bearings.

Just think of what it would take to make up for the lost material. More or less?

 

[SnowBird]

What do you mean by they are .25?

Crank mains or rod journals made any way smaller use oversized bearings.

Just think of what it would take to make up for the lost material. More or less?

They are .25 oversized, thats what they say. I know more would make up for the lost material, the question is why the hell are some undersized? I thought maybe if you had the rods ground down instead of the crank they would be called undersized for some reason because the bearing would have to be thicker on one side than the other. I dont really understand the whole undersized label, so thats why Im asking.

 

[jking29]

I believe you mean .025 instead of .25. And when a rod is resized, they take a slight amount of material from the mating surfaces of big end of the rod and then resize it to a stock bore size. If you had the crank polished and it has never been turned, the bearing size you need should be a .0025. If you would need .25 bearings, the crank is nothing more than a heavy paper weight.

 

[luvmygst]

I believe you mean .025 instead of .25. And when a rod is resized, they take a slight amount of material from the mating surfaces of big end of the rod and then resize it to a stock bore size. If you had the crank polished and it has never been turned, the bearing size you need should be a .0025. If you would need .25 bearings, the crank is nothing more than a heavy paper weight.

I know you meant .025 not .0025(if the crank was cut if just polished you might just need .001 or .002) but I wanted to poke fun at you. (J/K) Generally the only thing that you get oversized is like piston rings/pistons etc. When you have to add the whatever what you took out(material) THen you get over size things. When you turn a crank and take material away, you need under sized bearings., but if you took the block and had it line bored you would need over sized bearings.

I think I kept my head staight while typing that Im watchin the game at the same time ) Go BEARS

 

[jking29]

I know you meant .025 not .0025

Actually I did mean .0025 and not .025. As I said if the crank has not been turned and had a couple of scratches they may have had to polish it .0025 undersize. .025 is not a standard size bearing either. GO COLTS!!

 

[treebonker]

I'm sure they meant .25mm not inches. 0.25mm increment is usually the standard.

Undersize would be the correct term since it is used to identify the inner diameter of the bearings. The more you grind off the crank the smaller inner diameter bearing you need. People do mix use the term. You shouldnt need undersized bearings when micro-polishing though.

 

[BISHILVR]

They are known as undersize.

 

[SnowBird]

Ok. Ill lay it out here. I got a block from a guy who didnt know what the hell went on with it because his buddy built it. He said he thought the crank was turned once and the main and rod bearings were 10 over. Thats what he said. The main bearings were missing so I couldnt ID them, and the rod bearings say right on them next to the ACL logo 0.25, so like stated above its MM I guess. So Im guessing this isnt anything close to what the guy told me when he said the bearings were 10 over. So I was just gonna buy a new set of these and mains the same size and check for clearance, thats where the whole question about being over or undersized bearings came up. I guess Ill buy .25 undersized main and rod's and start from there?

I was just going to get the crank micropolished because the crank somehow got water down in it - it didnt do any damage- but it kind of made stains almost on the crank. Its nothing you can feel, but I didnt know when micropolished it actually changed the size, so this would result in different bearings again? I dont even know if it really needs to be polished.

 

[treebonker]

When people say 10 over it means ten-thousands of an inch( 0.010"). So thery're referring to 0.25mm.

 

[luvmygst]

Ok. Ill lay it out here. I got a block from a guy who didnt know what the hell went on with his block because his buddy built it. He said he thought the crank was turned once and the main and rod bearings were 10 over. Thats what he said. The main bearings were missing so I couldnt ID them, and the rod bearings say right on them next to the ACL logo 0.25, not .025, not .0025, but 0.25. So Im guessing this isnt anything close to what the guy told me when he said the bearings were 10 over. So I was just gonna buy a new set of these and mains the same size and check for clearance, thats where the whole question about being over or undersized bearings came up. So you guys are saying the .25 on the bearing is wierd?

The game is over now I can think now. The guy shoud have told you that the crank was cut down 10 under which =.010 or .25mm . You can never remove material and go .25 over. Those are the correct bearings if he told the truth. .25mm=.010 or 10 thousandths. You crank has probably been cut .010 mains and .010 rods. Thats the first standard size for undersize bearings. Mic the crank and check it against the factory spec to be sure. Good luck

 

[luvmygst]

Ok. Ill lay it out here. I got a block from a guy who didnt know what the hell went on with his block because his buddy built it. He said he thought the crank was turned once and the main and rod bearings were 10 over. Thats what he said. The main bearings were missing so I couldnt ID them, and the rod bearings say right on them next to the ACL logo 0.25, not .025, not .0025, but 0.25. So Im guessing this isnt anything close to what the guy told me when he said the bearings were 10 over. So I was just gonna buy a new set of these and mains the same size and check for clearance, thats where the whole question about being over or undersized bearings came up. So you guys are saying the .25 on the bearing is wierd?

The game is over now I can think now. The guy shoud have told you that the crank was cut down 10 under which =.010 or .25mm . You can never remove material and go .25 over. Those are the correct bearings if he told the truth. .25mm=.010 or 10 thousandths. You crank has probably been cut .010 mains and .010 rods. Thats the first standard size for undersize bearings. Mic the crank and check it against the factory spec to be sure. Good luck

 

[Defiant]

And after all that, throw away that crank and get a replacement. Mitsubishi says to not cut their cranks.

 

[BISHILVR]

I agree.