method of adjusting shimano rear derailer

Discussion in 'Bicycle Repair' started by craisin, Nov 21, 2009.

  1. craisin

    craisin Member

    Does anybody know the proceedure of adjusting the shimano rear derailer.
    So I bought a motor and I couldnt easily fit it to my frame so a friend had heaps of old racing style bike and he let me take 3 of them.
    2 of them were 12 speeds and the one I used had the cogs missing off the derailer
    In the end I put a more modern derailer and a twist grip 6 speed shifter off a smaller bike it works quite well but not consistantly well
    thanks in advance

  2. Pablo

    Pablo Motored Bikes Sponsor

  3. craisin

    craisin Member

    Thanks Pablo I can only only find 2 adjustment screws the B and the H.
    I think that other screw is in a different location
    I do have another parts bike that has that type of angled derailer but it would mean modifying the frame to mount that type derailer.
    Anyway its given me the basic understanding of it.
  4. craisin

    craisin Member

    I have to admit I followed your link to the forum and I just had to read the first answer to the clues so I counted the teeth on low gear and 28 total same as the wheel on the donor bike eg the bike I got the derailer and shifter off.
    My bike may be a part bin special from the early 70s it looks as it was painted in Commonwealth Games colours.
    I need to lose the steel Rims:rolleyes7:
    I have to keep an eye out for a wheel off a racebike with less than 28 on the big cog
  5. retromike3

    retromike3 Member

    rear derailleur

    There are usually more than two adjustments for a modern derailleur. First there are the ends for the top and bottom adjustment then there is a separate adjustment for cable tension. This is a ferrule usually at the shifter that helps you adjust weather the amount of upshift or down.

    If you go to a bike shop you can get a bolt on derailleur hanger from a less expensive bike that clamps to the place were the wheel bolts to the frame. this peace of steel will let you install a newer derailleur to an older frame.

    On the back of most derailleurs they have a set of numbers that say how many teeth they can handle very few can handle less than 28. There are usually three sizes of derailleurs, short ,mid and long. I had a mountain bike racer in my old bike shop that used a short cage derailleur for a 28 tooth cog set. what he did was shorten the chain until it pulled the rear upper pulley clear of the freewheel. This worked but you could not use the big chainring with the big cog in the back or it would jam.

    thanks -Mike Frye- the bike guy
  6. Nuttsy

    Nuttsy Member

    Also, make sure you're not using apples and oranges. On cheaper department store type bikes that utilize index shifting, if you have a Shimano shifter and say a Falcon freewheel set, you will probably get inconsistant shifting. It has to do with cog spacing and deraileur travel.
  7. craisin

    craisin Member

    good points mike and nuttsy
    Yes Mike its come to my attention that adaptor claw you speak of:rolleyes7:
    I have got rid of the front derailer and fitted the freewheel that goes with a jackshaft,and the original front big chainring was bigger the present one

    I plan to ride the bike without fitting the engine for a while to make sure things work together

    I want to upgrade to canterlever brakes before I put the engine on
  8. retromike3

    retromike3 Member

    cantilever brakes ?

    The next question is :is your bike already set up for cantilevers? Most bikes that have cantilevers are already set up with what's called a "derailleur hanger". If your not, then you will need to install cantilever studs. They are two brazed on cylinders per brake that the cantilevers rotate on and without them cantilevers are not feasible.

    I was thinking of making a plate that had cantilever studs built into it that you could mount on a standard front fork for a friend who has a racing wheel chair. He has problems with putting enough presser on his brake levers and I thought cantilevers with magura hydraulic brakes would stop his in no time.

    Mike Frye-the bike guy
  9. craisin

    craisin Member

    true mike
    I cut the cantilevers off a Bike called a Viva S but it had no derailer hanger like you suggest.
    I come from New Zealand.
    Anyway I cut off about 3inches of tube that have the cantilevers mounts then I split the tube in half and I intend to get a friend to mig weld the half tube and mount over the slightly smaller tube on the older bike [thats on the back]

    I tossing up weather to put shocks on the front depends if I can modify them to suit
  10. Mountainman

    Mountainman Active Member

    if you have a bike stand
    get that thing on the stand and work through those gears
    someone else can pedal with their hand so as to give you the whole picture
    you will easily see which screw stops are for low and high gear
    as you play with those things
    adjusting them up and down ((a little)) until you see exactly the change

    as mentioned above mix matching shifting levers to derailers may not be compatible

    MM - The Old Bike Shop Owner --
  11. craisin

    craisin Member

    well MM Im using the shifter that come off the same bike as the derailer.
  12. retromike3

    retromike3 Member

    cantilever part 2

    I hope you didn't cut up that frame quite yet. You can order canty studs and braze them on with silver solder and a propane torch. Its not that difficult. The hard part is making sure there at the right placement and parallel so your brakes are aligned correctly. There is a bit of adjustment in the brakes but its better to have them right to start with.

    Mike Frye- the bike guy
  13. craisin

    craisin Member

    its cut already Mike
    its cheaper for me to cut up old bikes than buy things.
    As I get old bike for nothing
    No classics though
  14. craisin

    craisin Member

    just like to add Mike
    the half rounds I ended up with I intend to attach them to the frame for the time being with hose clips so I can be certain they are in the right position before welding.
    Too easy:whistling: plus around the mounting point is beefed up
  15. ibdennyak

    ibdennyak Guest

    Pretty ingenious. I've done that on aluminum and *aluminum brazed* rather than welded. Haven't had anything break yet. Gotta learn to TIG :annoyed:
  16. craisin

    craisin Member

    well I would like to post some pics but I dont have bluetooth or infared to upload off my phone to my PC
  17. retromike3

    retromike3 Member

    getting hosed

    I am hoping that if your using hose clamps your just using them to "size things up" I can't be sure of the force needed to hold the brake in place while it is stopping you from 50 miles per hour.(downhill, tailwind ect.)

    Back when dinosaurs ruled the earth I had a recumbent frame made for me that had the seat held on by a pair of hose clamps. The bike was a single tube design, looked cool but it would not hold the seat on the tube, So I crashed the thing about six times on the way to work. since it was only eight inches off the ground I did not have far to fall, But I did look kind of silly.:rolleyes7:

    Man I would love to have a good TIG set up with a high frequency circuit. It would make my life a lot easier. TIG is fast and fast equals cheep. Some day when I am rich and famous.:devilish:

    Mike Frye-the bike guy
  18. craisin

    craisin Member

    yeah right Mike its just to line everything up.
    I could see a cantilever having spokes for lunch:rolleyes7:
    and me dining on gravel
    Yes I had a parachute accident 22 years ago and it like you it gives me insight into dangers.
    I like the idea of recumbants but unsure of the bail-out proceedure.
    Like harley riders with their feet out front must bad in a collision
    :whistling:have a nice day
  19. happycheapskate

    happycheapskate Active Member

    Falcon freewheel 5/6 will work fine with shimano 6 7 8 speed shifters

    If you have a proper derailleur hanger on the bike (welded or bolted on, not the type of derailleur that used the axle to mount and a little screw to keep from rotating), there is a tension screw that touches the dropout, with the screw head visible from the back of the bike. Tightening this screw moves the derailleur's top pulley away from the cogs, and may very well oversensitize it to cable movement. It should be adjusted so that the top pulley teeth do not strike the teeth of the cogs.
    If the shifter is 6/7/8 and the cog is 5 or 6, the shifter should be adjusted so that the lowest gear detent corresponds with the lowest (largest rear cog) on the freewheel.
    It helps if the axle stack (nuts cones etc) are placed so that the freewheel's highest gear is close as practically possible to the dropout. (this may require dishing of the wheel if large changes are made by moving nuts and washers i.e. literally moving the hub).

    Make sure you are using compressionless cable housings and plenty of lubrication. Don't skip out on using the proper ferrules.

  20. craisin

    craisin Member

    Merry christmas Happy
    Its all shimano