uciflylow

I bought this bike a few years ago with intentions of making a fixie, or single speed, out of it. I read all the horror stories about the bottom brackets and decided to check mine out. It is a standard 68mm British thread. I was able to install an old cartrage BB in, and the fixed on the other side of the shell, but not at the same time. It seems the threads are not square with the hole in the bottom bracket shell.
Can the shell be faced and the threads chased, or do I need to just stick to cup and bearings?Christmas 07 036.jpg

unworthy1

Facing and chasing won't fix this if the threads themselves are misaligned. And using a loose-ball BB might "work" but if the threads are misaligned then it's putting stress on the bearings and spindle that will eventually lead to uneven wear...I'd be surprised if you don't get a little binding with the open BB when properly adjusted. You should make sure of what the problem is, the BB shell might be OK and that Shimano giga pipe might be dodgy in some way...take all of it to your trusty LBS for a check up.

nlerner

You probably tried this already, but it's possible that you threaded the BB in a bit off from the drive side (as shown in the pic). I'd try screwing it in again, but this time do both sides pretty much simultaneously, which should keep the spindle centered. If that doesn't work, you can stick to cups and bearings, and there's nothing wrong with that setup as long as the cups aren't pitted.

Neal

uciflylow

Yea, I did try threading both in at the same time, NO GO! By the time you are about 5 or 6 turns in, everything starts to realy bind. The cups are quite pitted, so if this can't be corrected I guess I will get more cups, a shorter axle, and a new crank set.
Heck, it may not be worth the trouble, and expense at all!

I was thrilled to find it had English ISO cups! It is an older Motobecane with 700c wheels, rides smooth as silk, and don't look half bad.

nlerner

Hmm, that's a bit mysterious. I'd really think that an older Moto would have French-threaded BB cups. Perhaps a previous owner had forced some English cups in there, screwing up the threading? I managed to force a English-threaded sealed BB unit into an early 80s Peugeot bottom bracket. Wasn't pretty but it did work.

Neal

unworthy1

Could be, but depends on how old "old" is: Moto did switch over to BSC (English/ISO) threading at some point, so that BB may be BSC. If you don't want to spend any money at an LBS (but I think you should) the cheap way to chase threads is to take an old set of cups (with the CORRECT threading) and cut grooves at right angle to the threads to make sharp edges...like a tap has(I use a Dremel). But what I really like to use is a fine wire wheel on a cordless drill, I have one that's a nice tight fit in a standard BB shell. I run it in CW and reverse it out (or CCW in the fixed side of a BSC shell, whatever's right). After a couple passes everything shines, and then you can really see if the threads are bunged-up or not.

nick burns

That'd be my guess. Old Motos also used Swiss threads in the bottom brackets, someone could have mistaken it for tight fitting English thread.

uciflylow

Maby it's not as old as "I" thought! The threads are in fine shape and the aluminium cartrage BB threads in too easy to have been forced at one time. Part of the sticker on the frame is missing, so I'm not even sure of the tubing. Looks to be Vitus 80? can't make out but half of the middle number and the last number is MIA. I also can't find a "name" on the bike, so it may have been an early asian knock off?? The frame is lugged, although fairly plane lugs, I just wanted to see if I could make a decent single speed out of it, but a lot hinges on the BB and how well I can make it work. Beleave it or not everything on the bike works well. The shifters, brakes, and head set where in very good shape.
I did take a small wire brush to the threads and lots of WD40 to flush out the crud before trying to thread in the bracket. I guess I'll take the tihing over to Steve "not so LBS" and see what he thinks about the whole process. Thanks for any and all advice!

If some one wanted to put it back togather and ride it as a 6 speed. What hub would you use to change out for that Malliard Helico thing??

repechage

I had a bike with a problem like this, I pulled the BB apart for service and noted that the bearing path traced in the cups was an ellipse, on both sides! The BB shell was not square and the threads were aligned to the off edges of the BB! Scary. And this was on a "custom" British Lightweight frame... An hour with a Campagnolo tool kit and some Sturmey Archer cog washers to take up the loss of BB material required to set things right solved the problem. Only other choice would be to use a Phil Wood cartridge BB, the threaded rings are short and can be misaligned to the cartridge a bit. Not a cheap fix, but we were not talking cost.

Or look for a Mavic cartridge BB, facing still required, but the lock rings seat into a chamfer that needs to be cut into the BB shell. A good choice for less than great quality frame work.

uciflylow

One other thing. The Left and Right threads are on OPPOSITE sides of the bracket from the Trek I took the cartrage bb from??

unworthy1

Hmmm, I'm getting confused, here. Which side (viewed from above) is the LH threading in the Moto's BB shell? Now which side (same view) is it on this Trek? I'm anticipating that you might have just turned the BB around, OR (shudder) you have one of those weird Shimano BBs that I've only seen on the cheapest Treks (but must have come on other cheepo bikes too) that are "reversed". I've only seen that freakish BB in a square-taper spindle, though. I know that I hate them...

ollo_ollo

" Part of the sticker on the frame is missing, so I'm not even sure of the tubing. Looks to be Vitus 80?"

My mid 80s Motobecane Grand Touring has Vitus 888 tubing, would guess that is what you have also. Don

uciflylow

The cartrage screws in from the Non-drive side on the Moto and from the drive side on the Trek. The Trek is a 2003 Trek 2000. The adjustable cup on the Moto is on the drive side behind the rings! I found a picture of an intact sticker like the partial sticker on my Moto, it probably is the 888. I deduced this by the colors of the numbers. I thikn the second number I can only see the top of is an 8 and not a 0.
I'm going to pick up some 1/4 inch lose bearings to replace the caged ones. Plenty of good grease and ride it as a 1/6 for a little while and just see what happens.

unworthy1

still clear as mud, but I think I understand that the Moto has it's adjustable cup on the "fixed" side...if it was correctly installed to begin with. So the threading on the non-drive side should be left-handed, if it is then the Moto has the dreaded "reversed" BB. Maybe they were taking a page from Trek's book back in the early '80s...

infinityeye

or it's just french threaded...

uciflylow

If I understand correctly. The cups will have a tendancy to unscrew opposite the direction of crank rotation? If so, they are indeed in "reverse", I didn't relize that Trek had made some like this in the past.
I just stripped everything but the front brake, shortened the chain, went with the 40 tooth crank, repacked the head set bearings (they look brand new), greesed and reinstalled the stem, and took it for a ride.
It seems to ride ok and I do need to tighten the BB up a little, but for right now it's a single speed. Actually it has enough room in the drop outs to do 2 gears by moving back and forward in the drops.
Thank's for the help all, it has been a learning experence to say the least!

unworthy1

The standard BSC BB threading is Right-hand on the Non-drive side and Left-hand on the Drive side. Trek didn't make the reversed BBs, Shimano did, Trek is just the only brand I ever saw them used on, but I'm sure others did use them, too. If you ever see one, it'll typically be a cheap steel cartridge unit and instead of UN-something it's labeled L-something. What Shimano was thinking I'll never know, I just hope they all end up composted, real soon...at least they're off the market now, AFAIK. If you want to learn right, start with Sheldon Brown's articles, then visit the Park Tool pages.