RH Clark

Doing a BB service on a square taper BB. Cup races look good, but the axel is rough on both ends. Should I lightly sand the pitting with emery paper or leave it? Should I replace the ball bearings regardless? I didn't remove the fixed cup, but may later as I may not be totally happy until I replace with a sealed unit. Just wondering if a light sand will help or if it will just make the axel more out of spec.

grumpus

It wouldn't be a "light sand" - you'd have to remove the hardened surface layer to get it concentric again, and then you'd have a soft bearing surface that didn't fit the cups. Just fit a cheap cartridge bearing unit and be done with it.

RH Clark

Yes, I realize that. What I am asking is, is there any benefit to doing a light sand? I will eventually replace cup and cone with a sealed unit, but I am going to assemble now until I get the parts and tools necessary to get the fixed cup off. I just wondered if I could do it any good with a light sand. I know what it would take to completely remove any scaring, and it would be too much IMHO.

Barry2 

If you need to ride it while waiting on tools/parts, just throw it back together.
Where I am tools/parts takes 2-3 days. We don’t know where you are, YMMV.

Barry

kcjc

Not going to make any difference and is a complete waste of time

RH Clark

Well Barry, I'll buy the park fixed cup tool, but I have to learn what to order for the sealed unit. Nearest bike shop is an hour drive one way so I can't just run by and ask them. The axel says 68=W=116. If you can point out the unit, I need perhaps I can get everything together in about a week. If not then I need to post and learn I suppose.

Iride01 

You really only need to worry about pitting when the pits are in that very thin shiny line that goes around the race. That's where the ball bearings touch the race. And usually that is when it's time to toss the part for a new one. Change your lube more often if you are pitting. Don't confuse pitting with just minor etching that discolors the race in a blotchy way, but is probably a sign that pitting is about to happen if the lube isn't cleaned out and changed.

Barry2 

Sounds like you have the size nailed down.... Now you need to know the threading.
Posting the bike Manufacturer, Model and year will help someone identify it.

Barry

RH Clark

It's a 1986 Trek 560. USA made Reynolds 531 tubes CR-MO fork. Shimano 600 group. I did verify the date codes.

Barry2 

Apparently it's been asked before

Barry

RH Clark

Sorry, I didn't even know the right questions to search. Thanks for the link.

RH Clark

No rust but the axel is definitely pitted. Yes, it needed service sooner. Unfortunately, I just acquired it as a project bike. Only gave $100 for it. It's a good candidate for me to learn on.

RH Clark

I didn't know I needed a photo to ask the question. I know the races look rough on the axel. I'm not on my phone. I do have one. It stays beside my bed most of its life. I did take a picture of the axel for myself, but I would have to get my phone, log on this forum, and see if I could transfer my picture to this forum. I used to post internet pictures back when we loaded everything from photobucket. That's how anti tech I am. I don't like that a phone always with you is taking all your attention. My wife keeps one in her face all day and I hate it. It's like being plugged into the Matrix from the movies. A smart phone sucks all your life and feeds you a false reality. So, yea, I could figure out how to post a picture, but there's no concerted effort on my part to avoid it, I just didn't think it was necessary to go through the effort.

Sangetsu

Pitting (otherwise known as “galling”) is not repairable. You can clean, re-grease, and keep riding, but your bottom bracket won’t be as smooth as it should be. You can’t really sand off the galling, you would just make things worse. Bottom bracket axles are usually heat treated, case hardened, or hard chrome plated, in either case, sanding removes the hardened surface of the steel. Square taper bottom brackets aren’t especially expensive, and not that hard to install.

70sSanO

First step is to determine if the cups are pitted. If not, you could find a donor BB or BB spindle and replace the bearings and ride it for years without a care.

While cartridge BB are an easy fix, cup BB’s have endured for decades. A co-op or even eBay might be worth the effort.

The sanding might be moot, as you are not precision grinding it. If you use a lathe it might be better than trying something by hand, but I’d just put it back together and find a replacement.

John

SurferRosa

Instead of all this, you could have just posted a photo already.

Duragrouch

OP: The pitting you have described is not "galling" as some have mentioned, but "spalling". If you want to get the bike back together right away, you may be able to use it. Usually, spalling happens on part of the rounded portion, but not most of it, and that part will be when that part is facing DOWN, when you are applying pedal force on that side. To use axle for now, clean it well, do not sand, and then mark on the end of the axle with red nail polish or any paint or marker, the orientation of the spalled portion. Grease and reassemble bottom bracket, preferably with new bearing balls. When you put the crank arm back on, orient the spalled area to be facing UP when the crankarm is in the forward-most position, as that is when the axle experiences its greatest load on that side. If you have spalling on both ends of the axle, that will also reverse the spalled portion on the other side. Adjust the bearing tightness before putting the crank arms back on, so you can spin the axle with your fingers; You want no slack, and a bit of preload on the bearings; Tighten bearing cup until spinning the axle feels "notchy", then back off ever so slightly until that goes away; When you spin the axle, you should feel the engagement of all the balls, not quite as easy as with no preload, but not notchy. Replace with a bottom bracket cartridge when you are able.

FBinNY 

Ball bearings are self tending. The rolling balls circulate grease, crush or push to the side dirt, and maintain the ball track the same way trains keep rails polished and rust free.

Other than periodic cleaning and refreshing the lube they neither need nor want your help.

ScottCommutes

Not only this, but bearings fail very safely and very politely. A bike wheel with no ball bearings at all will continue to roll (poorly) and will not fall apart or off the bike. I've ridden a bike with a destroyed bottom bracket (the bearings crunched audibly and the cranks had obvious play in my hands) for miles to a repair shop.

Duragrouch

I mostly agree. However, the ball bearing wheels on my otherwise quality rollaboard luggage, had steel ball bearings with no grease, no dust shields, and grit just tore them up, the wobbling may have contributed to the urethane outer wheel separating from the plastic core. Luggage repair wanted $100+ to replace both wheels, but with same crappy OEM design. And the axle was riveted on. I replaced with same size inline skate wheels, excellent bearings, greased and sealed, and reattached with bolts, which the luggage guy said would come loose, but secured with nuts torqued against each other hard. So far great, if they come loose, I'll use thread adhesive.