Forum home Mountain biking forum MTB workshop & tech

Front Mech Issues

gt-arrowheadgt-arrowhead Posts: 2,507
edited May 2013 in MTB workshop & tech
Hi, ive just changed the front mech on my bike, and im having issues with getting it to work properly.

At the moment, ive taken the chain out of the front mech as it only lets me use the granny ring, just until i can find a solution to the problem. Im just using the largest only at the moment.You can see what i mean in the pictures.

I have adjusted the front mech to go as far away from the frame as possible, but still no luck. I think i know what the problem is though. The BB looks to be making the cranks/axle be too far away from the frame.

Before i had the new front mech on there (The new one is a Shimano Nexave) i had an Altus with a sort of "plate" that sits inbetween the BB and the frame. The Altus mech was mounted to this plate via two screws. I also experienced the problem of it not changing to the largest ring, but it wasnt as bad as it is now. (The cranks have been changed, but the ratios are exactly the same) Eventually i had had enough and i ripped the outer guide of the mech off... I could have removed the mech from the plate but the plate would just shake around, so i ripped the outer guide off.

Pictures of the old plate and mech:

IMAG0179_zpsb2c99627.jpg

IMAG0180_zps985668e8.jpg

I now have a massive gap between the BB and the frame from where that plate used to sit, i think that this is causing my problem of the mech not having enough range to change to the larger chainrings. The BB wont screw into the frame anymore.

If i unscrew the non driveside part of the BB a bit, would it allow me to screw the BB in more from the driveside? Even still i dont think the mech would reach the largest ring...

Is it just that my BB axle is too long or something, and i need to get a new one?

Thanks alot for the help in advance.

Here are some pictures, you can see the gap clearly in the first picture:

IMAG0176_zps1fa66e96.jpg
IMAG0177_zps9678af8e.jpg
IMAG0178_zps901b0d36.jpg
This is far out as the mech comes when its shifted to the highest gear
IMAG0181_zpsa53434de.jpg
This is it on the lowest gear
IMAG0182_zpsd930b5c2.jpg

Posts

  • The RookieThe Rookie Posts: 27,803
    Loosen non drive side bearing cup and insert BB properly BEFORE you ride the bike......

    Thecable should pull the mech out, if it doesn't then back the high stop off.

    Nexave are usually for trecking gears (48T) is that what you have? If not, wrong mech.
    Current steed - Whyte T129, 2013 frame, mongrel Revelations, Giant dropper, Stans S1 wheelset. 12, Magura Trail Sport brakes, 1x11. 12.8Kg
  • nicklousenicklouse Posts: 50,675 Lives Here
    well first off your BB is not fitted correctly.

    fit it correctla and your problem might go.

    that is presuming that the BB is the correct one for the cranks and I have a feeling that it is not.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • gt-arrowheadgt-arrowhead Posts: 2,507
    The BB is as tight as it goes into the frame. Thats as far in as it goes.

    The BB is original, never been changed (still works fine, and i lube it regularly) It must be correct because the original cranks were square taper, and so are these ones. Are two different square taper cranks different? The old one was an Altus crank.

    I took the Nexave from a Ridgeback Velocity. should it not still work? I use a 42t largest ring.

    Ill unscrew the non drive side and screw the drive side in.

    Thanks for the replies.
  • nicklousenicklouse Posts: 50,675 Lives Here
    The BB is as tight as it goes into the frame. Thats as far in as it goes.


    sorry no it is not.

    fit it correctly.

    if you dont know how read parktools.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • *AJ**AJ* Posts: 1,080
    looks like a 73mm BB in a 68mm shell to me!
  • gt-arrowheadgt-arrowhead Posts: 2,507
    It probably is. What is the benefit of them fitting that sort of front mech in the factory anyway? (the one from the first 2 photos)

    Looks like ive gotta get myself a new BB...
  • Chunkers1980Chunkers1980 Posts: 8,035
    Probably cheap or clamp ons would not fit.
  • The RookieThe Rookie Posts: 27,803
    The problem is the non drive side cup was tightened upto the BB when the plate was in place, now the plate is out you need to back it out before you tighten the cartridge in from the drive side, right now the non drive side cup is stoping it,just like I said first time, NOW DO IT RIGHT.
    Current steed - Whyte T129, 2013 frame, mongrel Revelations, Giant dropper, Stans S1 wheelset. 12, Magura Trail Sport brakes, 1x11. 12.8Kg
  • anj132anj132 Posts: 299
    OT but that was a good job with a spray can ;)
  • gt-arrowheadgt-arrowhead Posts: 2,507
    Cheers anj132 :)

    I shall get it sorted this weekend. Wont be riding the bike between now and then anyway. Thanks for the help.
  • nicklousenicklouse Posts: 50,675 Lives Here
    Also as the BB is for an E type mech you need a spacer there now as you have removed the plate.

    So why did you change the front mech?
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • Kowalski675Kowalski675 Posts: 4,412
    I see what the problem is. Your camera's shite. :wink:
  • Chunkers1980Chunkers1980 Posts: 8,035
    Yes, would be obvious if your mum was in the background what the problem is too
  • gt-arrowheadgt-arrowhead Posts: 2,507
    When i first got the bike the front mech wouldnt shift to the largest chain ring no matter what i did with chain tension or limit screws. I didnt have a BB tool at the time so i couldnt remove it, so i just ripped the outer guide off of it (you can see it in the 2nd picture, its only got one guide, the outer is missing) It is a bodge job but there you go. Since i stripped the bike so i could spray it i took the opportunity to get rid of the crappy mech. As i said in my first post, i had an as new Altus one in the spares but that was a top pull mech and didnt work. So i had to settle for this. Im having a look at at a Deore LX front mech on eBay locally for £8 and im contemplating whether to go for it or not.

    I think i may aswell get a new BB instead since that is the only original part left on the bike (apart from the fork), and now is causing problems. Ill still have a go at unscrewing the non drive side cup out and screwing the drive side in so its flush with the frame.

    My phone is pretty bad yes.

    Chunkers, My mum said fk off. Hahaha :D (she was reading)
Sign In or Register to comment.