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07-27-05, 07:45 PM
Today I set out to replace the bottom bracket in my Maserati conversion with a square taper instead of cottered, so I could use the Sakae crankset I had found.
After making some measurements I had made the educated guess that I'd need a 107mm spindle, in a 70mm shell/Italian threaded bottom bracket. I ordered a Shimano UN-52 matching those specifications for 14.00$.
After it arrived today, I removed the cottered cranks, which is very easy, fortunately. (Actually, too easy, which is why I'm replacing them). The adjustable cup and spindle came out without trouble, but then I had to tackle the fixed cup.
Step one. Grab it with a lockring spanner. No dice, it can't get the right amount of purchase, and keep slipping off.
Step two. Grab it with a pipe wrench. No dice, it keeps stripping material off the cup, no matter how much 'dig' I get.
Step three. Verify that the threading IS Italian, and that it is right hand threaded. Yes, yes it is. Spray penentrating lubricant (PBlaster) liberally.
Step four. Put fixed cup in vice, and rotate frame above it to unscrew. Nope, it keeps slipping. Use a hammer to tighten the vice as hard as I can get it to go. Attempt to unscrew using entire frame as lever arm. End up shearing several of the teeth off the vice.
Step five. Apply heat from a MAPP torch. Light residual grease on fire.
Step six. Try the pipe wrench again. No dice.
Step seven. Try the vice again. No dice.
Step eight. Go to hardware store and buy 2" long 5/8" hex bolt, four lockwashers, a fender washer, and an appropriate nut, ala Sheldon Brown (http://www.sheldonbrown.com/tooltips/bbcups.html). Slip four lockwashers over bolt, and slide through bottom bracket shell, and through the cup. Put another washer over the bolt, and then the nut. Use a socket wrench on the inside, and a combination wrench on the other side to tighten the nut. I hold the combination wrench stable while tightening the socket wrench, with the hope that soon friction will take over, and allow me to unscrew the cup. No dice! Damn!
Step nine. Grab the 3' long cheater bar, and slip it over the socket wrench. Can't do it.
Step ten. Get out the seldom used air compressor, and the 250 ft/pound pneumatic impact wrench. The one I use for putting lug nuts on bus wheels. Attach the appropriate impact socket. Clamp the bike securely in a vice. Hold the combination wrench with one hand to help steady it, and then give the impact wrench a shot at its lowest torque setting. This tightens the nut down just a little further, but fails to release the cup. Jack up the torque setting. Nope, can't do it. Jack the torque setting up again. No, can't do it! Finally, at the highest possible torque setting and overpressured to 100psi, I just start wailing on it. I'm screaming as the impact wrench slams the bolt with all its might, for several seconds. I'm using the most destructively powerful tool I own, and damned if I'm going to let this fixed cup win!!! After nearly 20 seconds of impacting, I hear a loud squeal, and the fixed cup begins to move!!! It spins out quickly, and I shut down the impact wrench, marvelling at the sound of the now silent room.
I'm expecting the threads to be destroyed, but upon inspection, the threads are just fine! I run a quick rag over them to ensure their cleanliness, and proceed to install the new bottom bracket without incident.
But my troubles weren't over...
It turns out that 107mm wide spindles on 70mm wide bottom bracket shells is aggressively narrow. In fact, so narrow that my chainring hits the chainstay! Since my Sakae is a cheap no-spider variety, there is no way to move the chainring. In fact, to make matters worse, further measurements imply that 107mm is actually too narrow for my chainline! 111mm would have made more sense.
However, after what I've been through today, I was not about to end in defeat and order another bottom bracket. I grabbed my trusty ball peen hammer, and sat the frame down on my lap like an unruly child. After utilizing the hammer to carefully re-engineer the chainstay configuration (beat it into submission), I was finally able to clear the chainstay with my fabulous 52t chainring. Unfortunately, now the bottom of the crank was hitting the shell of the bottom bracket! A few quick wipes with a dremel shaved the top .5mm off the BB shell, and I was finally able to tighten the crank down without it dragging or hitting anything.
To rectify the chainline problem (my chainline is now about 38mm) on the hub side, I had to flip my Soma cog over on the nashbar hub. Don't worry, there is still a satisfactory 'flat spot' for the lockring to engage. After securing the cog, I delicately made sure that the chain wouldn't hit the spokes (ha, it doesn't!), and reassembled the bicycle. A final chainline measurement indicates that chainline is within .5mm! Hows THAT for a beater? ;)
To celebrate my success, I taped the flipped and chopped bars with double-discount clearance rack too-ugly-to-sell camo bartape. Oh yeah. Next steps will be a paint job once I decide on a color, and to shave off all the cable stops. Oh, and a longer seat post. ;)
Photo legend: A photo of the reengineered chainstay. I'll sand it smooth when I paint it, and no one will ever know. The clearance there is less than .5 mm at its smallest point. Amazingly tiny. There is also a photo of the shell clearance, also about .5mm. If you look close, you can even see a line cut into the chainring from when I first installed it and made a few test revolutions as I noticed that it was dragging against the shell. Then the whole bike, so you can marvel at its stereo-typical beater/conversion goodness.
I post this in hopes that someone with similar problems will be able to use my experiences to decide what NOT to do to their poor bike.
peace,
sam
P.S. with the straight chainline and the 'real' cranks, the bike rides like never before. Its a dream come true!
After making some measurements I had made the educated guess that I'd need a 107mm spindle, in a 70mm shell/Italian threaded bottom bracket. I ordered a Shimano UN-52 matching those specifications for 14.00$.
After it arrived today, I removed the cottered cranks, which is very easy, fortunately. (Actually, too easy, which is why I'm replacing them). The adjustable cup and spindle came out without trouble, but then I had to tackle the fixed cup.
Step one. Grab it with a lockring spanner. No dice, it can't get the right amount of purchase, and keep slipping off.
Step two. Grab it with a pipe wrench. No dice, it keeps stripping material off the cup, no matter how much 'dig' I get.
Step three. Verify that the threading IS Italian, and that it is right hand threaded. Yes, yes it is. Spray penentrating lubricant (PBlaster) liberally.
Step four. Put fixed cup in vice, and rotate frame above it to unscrew. Nope, it keeps slipping. Use a hammer to tighten the vice as hard as I can get it to go. Attempt to unscrew using entire frame as lever arm. End up shearing several of the teeth off the vice.
Step five. Apply heat from a MAPP torch. Light residual grease on fire.
Step six. Try the pipe wrench again. No dice.
Step seven. Try the vice again. No dice.
Step eight. Go to hardware store and buy 2" long 5/8" hex bolt, four lockwashers, a fender washer, and an appropriate nut, ala Sheldon Brown (http://www.sheldonbrown.com/tooltips/bbcups.html). Slip four lockwashers over bolt, and slide through bottom bracket shell, and through the cup. Put another washer over the bolt, and then the nut. Use a socket wrench on the inside, and a combination wrench on the other side to tighten the nut. I hold the combination wrench stable while tightening the socket wrench, with the hope that soon friction will take over, and allow me to unscrew the cup. No dice! Damn!
Step nine. Grab the 3' long cheater bar, and slip it over the socket wrench. Can't do it.
Step ten. Get out the seldom used air compressor, and the 250 ft/pound pneumatic impact wrench. The one I use for putting lug nuts on bus wheels. Attach the appropriate impact socket. Clamp the bike securely in a vice. Hold the combination wrench with one hand to help steady it, and then give the impact wrench a shot at its lowest torque setting. This tightens the nut down just a little further, but fails to release the cup. Jack up the torque setting. Nope, can't do it. Jack the torque setting up again. No, can't do it! Finally, at the highest possible torque setting and overpressured to 100psi, I just start wailing on it. I'm screaming as the impact wrench slams the bolt with all its might, for several seconds. I'm using the most destructively powerful tool I own, and damned if I'm going to let this fixed cup win!!! After nearly 20 seconds of impacting, I hear a loud squeal, and the fixed cup begins to move!!! It spins out quickly, and I shut down the impact wrench, marvelling at the sound of the now silent room.
I'm expecting the threads to be destroyed, but upon inspection, the threads are just fine! I run a quick rag over them to ensure their cleanliness, and proceed to install the new bottom bracket without incident.
But my troubles weren't over...
It turns out that 107mm wide spindles on 70mm wide bottom bracket shells is aggressively narrow. In fact, so narrow that my chainring hits the chainstay! Since my Sakae is a cheap no-spider variety, there is no way to move the chainring. In fact, to make matters worse, further measurements imply that 107mm is actually too narrow for my chainline! 111mm would have made more sense.
However, after what I've been through today, I was not about to end in defeat and order another bottom bracket. I grabbed my trusty ball peen hammer, and sat the frame down on my lap like an unruly child. After utilizing the hammer to carefully re-engineer the chainstay configuration (beat it into submission), I was finally able to clear the chainstay with my fabulous 52t chainring. Unfortunately, now the bottom of the crank was hitting the shell of the bottom bracket! A few quick wipes with a dremel shaved the top .5mm off the BB shell, and I was finally able to tighten the crank down without it dragging or hitting anything.
To rectify the chainline problem (my chainline is now about 38mm) on the hub side, I had to flip my Soma cog over on the nashbar hub. Don't worry, there is still a satisfactory 'flat spot' for the lockring to engage. After securing the cog, I delicately made sure that the chain wouldn't hit the spokes (ha, it doesn't!), and reassembled the bicycle. A final chainline measurement indicates that chainline is within .5mm! Hows THAT for a beater? ;)
To celebrate my success, I taped the flipped and chopped bars with double-discount clearance rack too-ugly-to-sell camo bartape. Oh yeah. Next steps will be a paint job once I decide on a color, and to shave off all the cable stops. Oh, and a longer seat post. ;)
Photo legend: A photo of the reengineered chainstay. I'll sand it smooth when I paint it, and no one will ever know. The clearance there is less than .5 mm at its smallest point. Amazingly tiny. There is also a photo of the shell clearance, also about .5mm. If you look close, you can even see a line cut into the chainring from when I first installed it and made a few test revolutions as I noticed that it was dragging against the shell. Then the whole bike, so you can marvel at its stereo-typical beater/conversion goodness.
I post this in hopes that someone with similar problems will be able to use my experiences to decide what NOT to do to their poor bike.
peace,
sam
P.S. with the straight chainline and the 'real' cranks, the bike rides like never before. Its a dream come true!