Leeroy_25

I want to change the stationary gear bearings front and rear on my engine as there is a little bit of copper coming through. I may as well do it while it is apart. I can only assume the shaft has not been ground and I need standard size ones what ever size/colour that is? Can anyone advise. I also want to double check if front and rear bearings are the same as 13B FD? I have been told by new place they are and then another they are not. I cannot get hold of Atkins and there shop does not list anything for 20B front and rear? Some help please guy's so I can get these ordered.

Also should the pilot bearing in the end of the E-shaft have a seal for 13B set-up. I see some available that come with a seal and some that don't?!

Thank you
Lee

Leeroy_25

Looks like I need a micrometer to measure this as I see the bearing size are like every 0.003mm!!
I measured shaft with a vernier at 42.87 small area and 42.90 large area. Anyone have any idea what shaft size equates to what bearing size so I can order the right thing or doe everyone just go with the first oversize (green I think)?

Cheers
Lee

hsmidy

You can use fd bearings front and rear but they are a different part number.
I would be surprised if the bearings size changed by 0.003mm as most micrometer's only go to 0.01mm.
What you are describing with regards to the copper is very common and was most likely a high spot in the bearing after install.
run the pilot bearing seal.

you will want to take at least 4 measurements of your bearing journal to get an idea of its dimensions before looking at new bearings and then you oil clearance will depend on what sort of rpm you will want to be seeing from your engine, this will also dictate length of engine run in time.

Leeroy_25

Leeroy_25

here is link with bearing sizes.

GENUINE MAZDA 13B ROTARY TURBO FD3S RX7 RX8 20B COSMO STATIONARY MAIN METAL BEARING OEM | JDM Planet

every 0.003mm!?

RotaryEvolution

iTrader: (30)

the painted bearings are for 2004 and later model engines. all 2002 and prior have a single size, with the exception of how many windows the bearings have. the FD has a 7 window bearing for better lubrication properties.

the renesis does actually chew through bearings so they offered oversized in case people reground shafts.

Leeroy_25

I have been advised I should probably get the green first over side to accommodate some shaft wear? Sound normal? Hence the size options are so close apparently. Shop seems to have good knowledge?

RotaryEvolution

iTrader: (30)

that will give you tighter tolerances, also longer break-in, as well i don't like the idea of running on the copper versus the babbett so i technically wouldn't advise it, no. it's rare an eccentric shaft is worn to the point of needing oversize bearings, but that is why you check the current tolerances and make that call yourself.

Leeroy_25

Banzai-Racing

iTrader: (11)

NF01-10-E050 Cosmo front and rear, which is the same as the FD green
NF01-10-E420 20b center

j9fd3s

iTrader: (3)

^ that.

i think for the FD its just a normal production tolerance, and then they grade them. if you're building an FD engine the E shaft is stamped with the bearing sizes, the last one i did was stamped YY which i assume means it had yellow/yellow bearings.

the side seal grooves are measured and stamped too, its the Kanji character, 1-5.

Leeroy_25

Thanks guys.. Perfect. So I will order green and I am good to go. I measured my journals anyway and got the following sizes.
Front
Narrow section: 42.915-42.920mm
wide section: 42.941- 42.945mm
Rear
Narrow section: 42.925-42.930mm
Wide section: 42.950-42.952mm
Not sure if anyone knows if that is good or bad. Doesn't look warn particularly to be fair.

What are side seals sizes stamped? They are just one size aren't they and length ground to suit?

j9fd3s

iTrader: (3)

the service replacements are one size, file to fit, but there is no way the factory built the engines that way, takes way too much time.

Leeroy_25

I see. Yes. Sized by length then. Makes sense.

Leeroy_25

I need help urgent please guys.. I ordered green FD bearings based on the post form Banzai that FD green is the same as a standard size 20B one? What has arrived is in fact yellow ones! Great! AS mentioned before the size difference is 1.980mm for yellow and 1.983mm for green I cannot see 0.003mm making a whole lot of difference? It won't effect clearance the manual shows as that is stated at 0.04-0.08mm (-.10.max) this is only to 2DP so I would need to be way off to go over that.
Just checking now the best I can with a vernier I am on the top of of book clearance. Best I can measure the bearings the worn and new ones come up the same circa 42.99-43.00. but again this in only to 2decimal places. when I micometered the shaft recently it was coming in the range 42.915 to 42.952. across the narrow and thick parts front to back.
So.. I also double checked with some feeler guages I have.. With the new and old bearings fitted over the shaft I can slide a 0.076mm feeler down the side. Next side up is 0.102mm that only goes part way about 10mm. but I noticed on the new bearing which is of course not contained in a gear yet that the feeler could slide in about 3-5mm further. i.e slightly more clearance. So it could be where it is not contained it can oval slightly allowing this or it could be the yellow size is 0.003mm up on stock for a 20B. but then the old bearings have copper showing so I would imagine more than 0.003mm has worn off of them.
So now I am in a dilema.
Do I run with these yellow ones I have assuming I am just in tolerance and that green won't actually make much difference? or do I order green in instead which will likely take a couple of weeks if they can inf act get them? I am pretty sure Atkins might only supply yellow and all the other ones I keep seeing as stock are yellow too.
Side note I had decided not to change the centre bearing as there are no real signs of wear. Same with rotor bearings. I am not being daft here am I? Just something someone said today got me thinking. Should I be changing at least the centre bearing as well even if it looks good? Just seems little point to put in a new bearing to have to break it in when the one in there is all nice and evenly broken in already?!

Thanks guys.

Leeroy_25

Just to add to the above post I spotted a couple of things. 20b centre bearing is yellow and 1.988mm thick. Compared to 1.980mm standard size for front and rear if getting yellow. Is that right are the front and rear clearanced differently from standard. I ask because I also. Prices there is a 1.988 oversize offered for front and rear that is also marked yellow. Part number E220? Should we in fact be using this?
The other point was the FD service manual does not make it clear if the clearance limits it states are an all around clearance.. I.e as measured by the radius or a total size difference for the two measured diameters. It says the word clearance which to me would actually mean a gap all around. So you take your shaft and bearing diameters. Subtract one from the other and then halve it. That gives you a 'clearance' In which case I am then on the lower limit of spec rather than upper. Can anyone confirm which is right?

Banzai-Racing

iTrader: (11)

Center bearing is E420, not E220

Leeroy_25

Yes I get it is physically different. Hence the E420. I just wondered if where this is sized at 1.988 should the front and rear in fact also be this size which is E220.
Main point is can I use the yellow E04 that I have? Going up a size isn't going to change the clearance significantly vs the numbers shown in the manual. And do we take the stated clearance value in the book as a clearance all around the shaft and bearing or as a total difference between the two measured diameters?
Cheers

TonyD89

iTrader: (10)

I figured out what .003 mm is in inches because it's what I use. It's a ten thousands of an inch, .0001". It is really almost nothing, I don't think you need to worry. The bearings crush down a bit when pressed in and I'm guessing that is why your book was focusing on bearing thickness. To get actual bearing clearance, measure the ID of the bearing after installation and compare to the shaft diameter. Or, measure ID of bearing bore, bearing thickness, and compare to the OD of the shaft. I'm a machinist, so that is my base of knowledge, not a 20b owner or mechanic.

Leeroy_25

My feelings exactly.. I had them fitted today and they do compress a bit too as expected. All appears rosey on the clearance front. Right.. lets get this thing back together!