K2 / Proflex Riders Group

General => Tech Forum => Topic started by: junkster on April 20, 2005, 09:22:12 am

Title: Front Mech shifting prob down to bb axel too long?
Post by: junkster on April 20, 2005, 09:22:12 am

I am running a 110 or 113mm axel (can't remember(http://idriders.com/newforum/YaBBImages/rolleyes.gif)) bottom bracket at the moment and whatever I do to the front mech to get it to shift to the largest chainwheel, it can't manage it. Could this simply be down to the axel length putting it too far away from the mech reach if ya like(http://idriders.com/newforum/YaBBImages/huh.gif)

(http://idriders.com/proflex/galleries/junkster/bb_view_underside.JPG)

any ideas would be great as it is driving me nuts. (http://idriders.com/newforum/YaBBImages/angry.gif) I have a Shimano Deore Mega9 top swing link dpull 34.9mm front mech.

cheers Dan  [smiley=beer.gif]

Title: Re: Front Mech shifting prob down to bb axel too l
Post by: Simon on April 20, 2005, 09:53:51 am

I know I risk stating the obvious but have you tried adjusting the H stop adjuster all the way out,there should be plenty of f/mech throw even with a 113mm b/b,
Simon.

Title: Re: Front Mech shifting prob down to bb axel too l
Post by: junkster on April 20, 2005, 10:23:56 am

Hi Simon,
             heh, heh.... [smiley=laughing.gif] sure have - apart from the obvious adjuster screw 'limiters', and the cable tention, etc, etc...I have tried raising and lowering the postion of the mech clamp on the frame..it simply grinds against the 3rd chainring and never engages. The chain is a Mega 9 compatible one I think (HG50 or sumit like that).  [smiley=turtle.gif]
cheers Dan

Title: Re: Front Mech shifting prob down to bb axel too l
Post by: Kevins19 on April 20, 2005, 08:10:52 pm

Hmmm... I think the axle of the BB is too long as you suggested. The crank arm and drive side crank arm look too far from the BB shell. Are you sure thats the proper length axle on the BB? Because if the driveside crank arm is too far "out" then that could cause the front der. to physically not be able to reach or extend all the way out to the large chainring.

BTW - why I am thinking this is on my EVO the crank arms are a few milemeters closer to the frame.

Title: Re: Front Mech shifting prob down to bb axel too l
Post by: junkster on April 20, 2005, 09:42:27 pm

Hi Kevin,
           sure - the cranks are Shimano M440 Mega9 (something like that) and the BB is a UN72 (LX) from memory. [smiley=groucho.gif]

The pic is a bit misleading as they are the same distance appart each side of the axel.

I will prob get a shorter BB as all else has failed. What BB d'ya reckon? (what is the shortest?)

cheers,
Dan [smiley=beer.gif]

Title: Re: Front Mech shifting prob down to bb axel too l
Post by: Sprucey on April 21, 2005, 02:02:17 am

That BB seems way longer that 113mm to me.

The 2003/04 LX BB was 122.5mm and that would explain the problem - it was specific to the M570 c/set. If youn run it with other c.sets you would have just the problem you are experiencing.

Title: Re: Front Mech shifting prob down to bb axel too l
Post by: will on April 21, 2005, 08:35:51 am

Dan,

I have also struggled against chain alignment issues with my new BB.
If you manually put the chain up on the big ring, how does the alignment with the various sprockets in the back?

Just a guess from the picture, but I believe your chainrings are too far outboard by 10mm or so.

Will

Title: Re: Front Mech shifting prob down to bb axel too l
Post by: junkster on April 21, 2005, 07:26:57 pm

Hi peps,
         cheers for all your input - did think it was poss this but didn't think the bb was oversized. What length d'ya all reckon I need then (5000 98' frame)

cheers,

Dan [smiley=beer.gif]

Title: Re: Front Mech shifting prob down to bb axel too l
Post by: Simon on April 21, 2005, 11:03:07 pm

Should be the same as an Oz,73 shell 113 axle
Simon.

Title: Re: Front Mech shifting prob down to bb axel too l
Post by: junkster on April 25, 2005, 11:05:26 am

Hi Simon,
             think it is a 68mm shell. Will get a 113mm axel. cheers, Dan