Mechanics 101

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Mechanics 101

I will try and add repair techniques from time to time. Come back and see if I can be of any help. If you have a repair problem please feel free to email me at and I will up load it here for anybody else that may need it too. If you need a little refreshing on the names of different bike parts open this window.

     I was asked to show how I make a conversion for older bikes to use the newer STI, ERGO or SRAM's double tap shifter systems. I figured I needed pictures so I made this page. Try it out and let me know if it worked for you. Just hit the LINK.

      Repacking the bottom bracket. There are pretty much two types of bottom brackets out there American and European. Most better bikes use the European style. The two can be distinguished by the fact that American style has the crank that is in one piece and snakes through the frame through a large bottom bracket shell. The European style is smaller and the arms are placed on to the spindle hence called a three piece crank.
      There is also a new American bottom bracked coming on a lot of kids bicycles coming out of Mega Mart stores. It is an American style but very small. Of course to make them cheaper but at a cost, I can not get parts for these. So if and when it has any problems you toss out the bike and get a new one.
      On the American style you first pull off the pedals. The left side as you would be sitting on it is left hand threads. After the pedals are off the need to remove the nut holding the arm in on the left hand side. This is also left hand thread. Then there is a tab washer to remove then the adjustable cone remember left hand treads. Pull it out and snake the crank out through the right hand side. If you need to remove the fixed cone that is right hand threads. Time to inspect all the parts for wear and replace what is needed. The cups in the frame are just pressed in. If they are worn bad or show cracks just punch them out with a punch.
      Putting the American crank back in is first put in new cups in the frame. I have a real nice tool made by Park but for years I used my vice and pressed them in or even a hammer to tap them back in. Just be careful not to miss and damage anything. Then grease the cup and cone put the bearings back on the cone, keep an eye on how they came out then go in only one way. Snake the crank back through the frame from the right side. Put grease in the cup then the bearings then the left side cone that is left hand treaded. Bring it all the way in then the tab washer then the lock nut. The adjustment is by setting it a little loose then tighten the lock nut down. and The play in the arms should just go away and if you spin the crank it will spin freely. This takes me two or more times to finf the sweet spot.

      The European style will need some specific tools to match the brand of BB and crank you have but the removal is always done from the left side first. Pull the cranks off with a crank puller that matches your crank. Then start on the adjustable side cup on the left side of the bike. All the adjustable cups are right hand threads on the left hand side. Got it? Pull it all out and then go to the right side. Depending on the treads it is either left or right threads. Italian and French will be right hand threaded and Swiss and British will be left hand threads. Sorry but I would need to see it to tell you for sure what it is. When you have it all cleaned just re-install it with lots of grease, how you took it apart. As for the finial adjust you need to get it so there is no play in it with the arms off and spins free. Then put just the right drive side arm on and check for play now. With the arm on you have greater leverage to feel for play. If there is a little play just tighten it up a bit.
      On both of these when you are done you can adjust it to a point were it has no play and spins very easily. Don't give up if it is too loose or too tight it will wear out very fast.

      Repacking the bottom bracket 2. Well it looks like a third one has showing up lately. The BB30 and PF30 bottom brackets have been coming on more and more upper end bikes lately. A quick evolution of BBs is the European style was used for close to 100 years. It worked great and if it was adjust right and redone every few years it would last forever. Then a few years ago Shimano came up with the external BBs. As with everything it was lighter and stiffer. But, I noticed it could not be adjusted. You put it in and BOOM done. The problem is since you can not adjust them any more they don’t last very long. But they are pretty cheap. Then came the BB30 and PF30. Same problem you put them in and BOOM you are done not adjustment at all. So the thing you will notice is they creak and they do it a lot. The fix is to put a lot of grease in there and that looks like it get the noise to go away.
      To repack the BB30 you will need an hex key to remove the left arm then just pull the right and left arm away. What is left is the sealed bearing in the frame. Check to see if there is a clip holding the bearings in and if not pop them out with a punch. I use a home made brass one but any one should work. To put it back in I have a press to get them in straight but if you can find a large socket you should be able to tap it back in. Cover everything with lots of grease and put all the wave washers and the like in were you found then and tighten it back up.
     First thing to do is remove the crank arms. Either you have to remove the dust covers to get to the nuts or bolts or some of the new ones have a puller mounted in to the crank arm. If the center of the crank arm has a large hex fitting 7mm or larger you have one of the ones that have a puller built in. With the built in one you just unthread the bolt and it takes the arm off with it. If you have a 5mm hex fitting you have a dust cap. So, remove the dust cap. After the dust cover is taken off you will have either a 14/15mm nut or bolt. A nut is a type 2 and a bolt is a type 1. Remember that so you can buy the right puller for your crank.
     Take your bolt or nut off and thread the puller all the way in to the arm. Now start to tighten the outer part of the puller in to the arm and that will push the arm off the spindle. If it is too hard to get off take it to a bike shop it is very easy to damage the arm at this point. With the arms off now with either the puller or the built in one. It is time to look at the bottom bracket now. There are just two types again. Sealed bearings and cup and cone. Most modern sealed bearings take a single special tool. Take your bike in and ask if they have that tool and yes get it from them. Then if you need help they might help you pull it off too. If it is the older cup and cone there are a few tools you need. I will go over that another time. Most of the time you will remove the non-drive side first. This is always a standard right hand thread. So counter clockwise is the way to go. It may be in tight so a long handle is required here. After that is out look at the drive side and start to remove that one. Most threads are Italian or British now. If the cup has any marking look at them. British is 1.37x24tpi. and Italian is 36x24tpi. The British will have left handed thread fixed cup and the Italian will have right handed thread fix cup. When you remove it take a good look at all the parts. If you need help here it is a good time to go back to the shop that sold you the tools and ask for their help with this one. Look in the shell too. It is a great time to put some frame saver spray in to the frame to protect it down the road.
     Now it is time to reinstall it. Always grease the threads in the frame and on the cup. Start with the fixed cup on the drive side and put it in really tight. Italian threads tend to creep out easy so make it very tight. After that is in move on to the other side and tighten in the other cup. If you have a spindle do not grease the flats just the oil from your hands is fine and install the arms with the greased crank bolts. Now check your work. And recheck the derailleurs and go ride your bike.

Replacing or installing a chain,
      There is a number of reasons to replace a chain. It could be rusty or it is damaged or it is worn out and last you found a cooler one that will make you go faster. If the chain is worn out you should look at replacing the freewheel or cassette too. They wear out about the same rate and if you try and cheapen out the worn freewheel or cassette will wear out your new chain very fast because the chain will try to fit the worn cogs.
      When you start shopping for your chain remember there are a large number of totally different sizes that are not interchangeable at all. Either bring your bike to the shop so they can get you the best fit or have all the information about it. There are two basic sizes one is ½ by 1/8” used on one speeds and most internal gear hubs and ½ by 3/32” used but most bikes with derailleurs. But the derailleur bikes are broken down in to the number of gears in the back. If you bike has 5-6-7-8 cogs in just the back use one chain then 9-10-11 speed all have their own chain size. You must know all this before you go buy your chain.
      The chain is a pretty important part please stick with a brand name chain. Those cheap no name chains sold a Mega Mart stores and just not worth it. When they break it can be a bad fall.
      Now if you bike came from a bike shop and you have not changed anything on it you have a pretty easy time now. Remove your old chain with a chain tool and stretch it out on the floor then put your new chain right next too it and mark the spot to cut it. Now the old chain might be a link or so longer then the new chain because if it is worn out it will have stretched out so match the inner and outer links. Other then that just run the chain through the rear derailleur at the smallest cog, you might have wanted to take a few pictures of how it ran through the derailleur first, then run it through the front derailleur cage , if you have one, then around the smallest chinring on the crank back to the rear derailleur.
      Okay you are almost done. Pull the chain together to the point were the rear derailleur just starts to pull on the chain. Now find the next link it will connect to and that is how long your chain should be. Now it should also be said this all works if your bike is pretty much stock and it is a bike shop bike. Bike shop bikes have a person that has the job of making sure all these parts fit and work together and from what I have seen Mega Mart bikes save money by not having this person. So be careful now because most modern derailleur bike chains can not be taken apart and put back together anymore so it is a one shot deal. If you chain is too long it will hang down but can be made shorter BUT if you make it too short it can break the derailleur and or your crank when you shift in to the largest cog in the back and the largest chainring in the front at the same time. So take your time here.
      A little product placement here I like the SRAM chains the best. They are all good with different price points and weights and most can come apart to clean it.
      When you have it all together find a way to pedal it through all the combinations by hand so if you find a problem you can do something about it before you break it.

     Derailleur adjustment. When I have got a problem with the derailleurs I always start by just looking at it, all over, from a lot of different angles. Even if you are not sure of what you are looking at just look it over. Are the cables rusted? Are the derailleur bent or broken? Is the chain or cassette bent or broken? These are all things that are hard to see until you look at it from different angles. If all that looks good lets go get a repair stand. An extra word here on Shimano STI shifting systems they are very prone to not shifting well when it gets cold. If it works when you take it in side to work on it that might be your problem and time to oil the shifting pods with a lighter oil.
     All derailleurs systems can be broken down into three parts. The shifters, the cables, and the derailleurs.
     First thing to do is separate them. So now we need the repair stand to hold the bike up to let you do some things. You can shift the rear derailleur with your thumb to see if any problem shows up. Just push it all the way in and let it go all the way back down. If you hit the spokes or do not come all the way back down it is most likely a bent rear derailleur hanger or a damage derailleur. If it is a bent hanger let the shop do it, the tool you need is more then the average homeowner needs. If it is the derailleur time to shop for a new one most are not rebuildable. On the front derailleur just pull on the cable that runs exposed down the down tube or the top tube on a mountain bike and see how the derailleur behaves. It is so nice to see it up close when you are shifting and so much easier to see problems then from the bike saddle. If the cage is not lining up with the chainring that can be a problem that is easy to fix. Just loosen the bolt the holds the derailleur on to the bike frame and move it until it lines up with the chainrings on the crankset.
The second part is to check the cables. Undo the pinch bolt the holds the cable on the derailleur and pull the cable back and forth. It should be perfect no hang-ups at all. Remember the spring in side the derailleurs are very small and do not have a lot of pull in them so if you are at all in doubt replace the cables. The cables are the number one problem with derailleurs not working right so this is the big one.
     The third thing to look at is the shifters. With out the cables pulling on them you still can feel the pull of the cable in you hand when you shift them. So shift them up and down and count the clicks. If it is the Shimano STI shifters you may have to spray a light oil in to the shifter pod to free up the little paws and springs in side them. Use an oil not a penetrating spray. Really flood them over some paper towels and keep trying to shift them up and down. If they do not come back it is time for new ones they are not rebuildable.
     So now it is time to put it all back together. Remember to tell the store what size and type of shifters you have because the cables are not all the same. And if you are getting new cable housing take the old ones in and let the shop cut them to size the cutter for the new index cable housing is a little pricey. Also use an pick to open up the end of the cable housing to cut down on friction in the system.

Installing and/or adjusting a front derailleur,
I figured the front derailleur is the hardest thing on a bike to set up and adjust so I will try and explain what I do to install and set up a front derailleur.
  1. when installing a new front derailleur just pick a spot that lets the cage not hit the chainrings grease the pinch bolt and install it but not too tight.
  2. Sometimes new derailleurs have a little plastic thing stuck in the derailleur to push the outer part of the cage so it sits out over the largest chainring. If it does not have this just pull the cage with your hand to where the outer cage is right on top of the outer chainring and it should be 2 mm above the outer chainring at the closest point.
  3. Now put your head up against the seat tube and look down. The outer part of the cage should be parallel with the chainrings.
  4. Now tighten the pinch bolt again.
  5. If you did that right the body of the front derailleur is set correctly now so it is now installed.
Adjusting the front derailleur
  1. Shift the rear derailleur into the lowest or largest cog in the back
  2. If it has the plastic thing in the front derailleur remove it. The cage should go to the lowest point and should stop when it hits the limit screw. They are mostly on the top and should have a very small marks of L and H to indicate High and Low
  3. If the cable is tight loosen the cable pinch bolt, grease it now, and turn the limit screw in or out until the chain is 1 mm away from the inside of the inner cage.
  4. As you turn the screw you should see the cage move in or out as you turn the screw.
  5. When the chain is 1 mm from the cage reinstall the cable pinch bolt and tighten it down.
  6. Now shifter the rear derailleur to the highest or smallest gear in the back
  7. Then shift the front derailleur to the outer most chainring.
  8. If it does not go all the way out try backing out the outer limit screw until it does.
  9. When done the outer part of the chain should be 1 mm away from the inside of the outer part of the cage.
  10. Now try and hit all three gears in all the different cogs in the back.
  11. Because of the way it works you may have noise in the extremes. The smallest front chainring should only be used with the inner largest 4 gears in the back, and the largest front chainring should be used with the outer 4 smallest gears in the back and the middle front chainring should be used with the middle set of cogs in the back.
  12. They should reach them all but the extremes can make noise.

Installing and/or adjusting a rear derailleur,
      I think the rear derailleur is easer to install and adjust then the front but maybe a few words here will help. The first thing and most common problem I see is the hanger, the part the derailleur mounts on to is bent. Even a little bent is not a good thing and it can be a very expensive repair if left unchecked. There is a few tools you will need like a Dropout Alignment Tool Set and a Hanger Alignment tool. Both are pretty expensive so you might want to let a shop check those for you. The first tool makes sure both drop outs are parallel to each other. The second one makes sure the hanger is aligned to the wheel.
      After that is done time to install the rear derailleur. First grease the threads on the upper pivot bolt, remember all threads get grease on them. On most derailleurs there is a stop some with a small screw some with out. That should hit the stop on the hanger. To do that you pull the derailleur back as you start screwing in the pivot bolt. There are lots of pictures on the internet go look for some and see what I mean. I will wait. Lol.
      Now install the chain through the jockey pullies. If your chain has a removable link do that if not remove one of the pullies and snake the chain through.
      Now the fun part. The set screws. Everybody loves to play with these. Somewhere on most derailleurs are two small screws most of the time marked with an “L” and an “H” that stand for low and high. Low is for the largest cog in the back and high is for the smallest cog in the back. Most derailleurs made today in the resting spot starts on the high cog. Go and get your eyes level with the derailleur and look to see if the chain goes straight down. If it is a little far out toward the drop out, screw the high one in until it is straight down. If it is away from the drop out screw it out until it lines up.
      Okay you are almost there. Put the cable in and make sure the barrel adjuster is most of the way in the derailleur and tighten it up. Now ever so slowly shift up to the lowest gear. If it does not go in try pushing it in a little with your thumb. If it moves more then you need to make your cable tighter if not you need to screw the low screw out a little until it does. Now if it shift all the way up on the first try push again with you thumb to see if it goes beyond that into the spokes of the wheel. If it does screw the low screw in until it doesn’t any more.
      Okay now try and hit every gear. With modern systems that are index you click it and with in one half turn of the crank it should be in. If not turn the barrel adjuster in or out to make it find the gear.
      You are pretty much done now and just a few things to remember righty tighty and lefty loosey on those screws and the cable will stretch in a very short time so you will need to use those barrel adjusters to tighten up the cable BUT you never have to mess with those high and low screws again. If you do something is BENT!