Rebuilding a Shimano SM BB70

Disclaimer number 1

I am NOT a professional bicycle technician nor did I get any professional training to do any of this. I just go with my gut feelings. Especially when something has a clear warning NOT to do it, and I can see how it CAN be done. 

Disclaimer number 2

High end bottom brackets in South Africa is crazy expensive, so I wanted to try something with this one and see if I can save it, and save some money. 

So with that out of the way, let's get this thing going

The victim: SHIMANO SM BB70 bottom bracket 

Th reason:

I am building a 26" Kona Coiler that my BIL gave me in pieces. Among those pieces were some cranks, and no bottom bracket. So I went and bought a generic one from one our LBS, but now the cranks are hitting the chainstays. So either I buy other cranks, and risk the same thing happening, or I upgrade to higher quality components. The last seemed the best solution, so I searched for one off these, but with cranks included. 

Then I saw a post on a local bicycle forum, were the seller advertised the bottom bracket and cranks for a third what the individual components would cost when you buy them new and separate. 

After paying, and receiving, the set, I saw why he was replacing them. Slop, wear, gritty and blown bearing on the non drive side. So I thought of just cleaning and regreasing everything as per a 100 videos on the 'Tube. 

When I got it open, I saw a standard cartridge roller ball bearing. This might look removable and replacable. 

As can be seen in one of the above photo's, it explicitly states, "Do Not Dissamble". What ever...... 

So step one will be, depending on how you get your BB, is either to remove it or stare at it. Again, if you don't know how, best not to attempt this, as later on you are going to need a hammer and a light touch. 

Step two, get the BB into the service position that everybody shows on the 'Tube. 

Drive side stripped and ready for some cleaning. 

Non drive side stripped and ready for cleaning. Yap. Totally FUBARed. 

Step three, get those roller bearings out. BUT, before I did that, I took some very loose measurements and phoned a local bearing supplier with my measurements and they said, yap, 6805 looks almost the same. I send the cups with the money and got some bearings

Since was in a rush, I opted for what they had in stock and not waiting a week to get another one. Now, using the 6805JRLLU, double rubber lip seal, would make more sense as it is the water proof option, I don't ride in the rain, and I don't do river crossings, so if they fail, i will order 2 ZZ, steel seal high speed bearings, in advance in the future. But I doubt I will need to replace it again. Ever. As the original did not have any seals. At all. 

So onto step three then. Got drive side out first, as that one is a bit more open in the back, and the, very gently, but very destructively, got the non drive side out

Step four, here you can get what Freddy was thinking when he sang, "Under Pressure". 

Cleaned up al the small markings left by the vice and the screw driver and started pressing in the new bearings. (No photos of during, just text). Seated the bearings loosely in the cups, and sloooowly pressed them in with the vice till the were equal with the sides, then pressed it home with the better of the two old ones, to distribute the pressure equally, until it bottomed out. 

Step five, reassemble everything

So total out of pocket is a third of what the lower spectrum of the quality parts cost and a fourth of the higher spectrum

Nice job.  I love servicing non-servicable parts.

Well played! Have you installed it in the frame with the corresponding crank yet? 

APEowner said:

Nice job.  I love servicing non-servicable parts.

Thanks a lot for the comment. Either it's me, or it runs in the family, but I learned from my father that there is no such thing, as "I can't". It's more a thing of I don't feel like it.

So when ever he saw a sign like that, he will try to dissamble it and see how it works, and the try to fix it

bluej (Forum Supporter) said:

Well played! Have you installed it in the frame with the corresponding crank yet? 

Not yet. That is in the cards for this week sometime.

Definitely not Wednesday night, as that is the scheduled night for action cricket night, and our team is playing again

So di d the bottom bracket install a couple of weekends after the rebuild, but I need a spacer for the headset, and with al that being close to start of the cold season, I decided to take it to a LBS to have them do that, and an inspection on the front fork. 

Then this will be ready for when the warmer weather starts coming around

Great write up!

Ok, am I delusional or is there something wrong here? 

I see that some one posted, but when I came to look, there was nothing.... 

The connorbarren poster to this thread