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Rear derailleur advice

apple eaterapple eater Posts: 302
edited April 2012 in MTB workshop & tech
I bought a used carrera xc vulcan for my son and the derailleur and hanger arm are bent. The derailleur is an sram sx4 8 speed unit.

My question after successive failed searches is, what can i replace the unit with? Am i restricted by the hanger arm or make of bike? Are there specifically different gearing systems that i need to comply with for what has been fitted to the bike?

I had the same thing happen on my old halfords apollo iron horse a while ago and the derailleur that i was supplied with worked in reverse numbering to the gear numbers up at the handle bars, this was quite confusing even after i'd figured it out.
I don't know enough to make smart r's remarks about peoples choice of parts 'n' things, yet!

Posts

  • nicklousenicklouse Posts: 50,675 Lives Here
    The hanger is frame specific. Any SRAM numbers rear mech (not 10spd).
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • apple eaterapple eater Posts: 302
    thanks for the info.

    I see that there are specifics in the number of gears such as 7/8 or 9 or 10 speed. Is the construction of these units physically bigger to move the extra gearing?

    I also assume maybe i'm limited by the structure of the derailleur to fit the hanger?

    I just want to avoid the mess up that i previously experienced.
    I don't know enough to make smart r's remarks about peoples choice of parts 'n' things, yet!
  • Chunkers1980Chunkers1980 Posts: 8,035
    Any SRAM not 10 spd. Hangers have universal threads. Shifters Determine mech movement
  • cooldadcooldad Posts: 32,599
    The mech you bought was a rapid rise - works in the opposite direction to normal. Would have been Shimano, and they don't make them anymore.
    SRAM don't make rapid rise, so no need to worry.
    Hanger you should be able to get from Halfords, or if not try BETD.
    I don't do smileys.

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    Parktools
  • The RookieThe Rookie Posts: 27,802
    Halfords sell the hanger for £7.99 with mounting bolt, a good price and not worth chasing anything else.
    http://www.halfords.com/webapp/wcs/stor ... yId_210153

    Any Sram 8/9 speed rear mech will work fine, from X4 through to X9 or even X0, try and get a good condition used X7 for a worthwhile upgrade and it will last longer than a new X4 anyway!
    Current steed - Whyte T129, 2013 frame, mongrel Revelations, Giant dropper, Stans S1 wheelset. 12, Magura Trail Sport brakes, 1x11. 12.8Kg
  • apple eaterapple eater Posts: 302
    Thanks for the info.

    I went to halfords tonight to enquire about the derailleur and the guy said only and x4 would do. When asked about something a bit better he just said thewy were all the same quality and all prone to bending.

    So from what i can gather on here if i go for an sram x7 long cage it is an upgrade to the x4 long cage that is standard on there and the gearing will be the same as is now?
    I don't know enough to make smart r's remarks about peoples choice of parts 'n' things, yet!
  • Chunkers1980Chunkers1980 Posts: 8,035
    Yes
  • apple eaterapple eater Posts: 302
    Last question on this.

    What is the upgrade between the units?

    Better / stronger construction? better materials?
    I don't know enough to make smart r's remarks about peoples choice of parts 'n' things, yet!
  • Chunkers1980Chunkers1980 Posts: 8,035
    Not a lot. Small differences in the things you list
  • The RookieThe Rookie Posts: 27,802
    Small incremental improvements in quality of material and tolerancing (and reduced weight) as you go up the range, X7 is a worthwhile improvement, X5 not much, look for a good used one in the classifieds or on ebay! All will bend if hit hard enough, Is the rear mech actually bent and not just the hanger?
    Current steed - Whyte T129, 2013 frame, mongrel Revelations, Giant dropper, Stans S1 wheelset. 12, Magura Trail Sport brakes, 1x11. 12.8Kg
  • apple eaterapple eater Posts: 302
    update to finish this thread.

    I replaced the hanger and all seems well. The derailleur cage was not bent it was just the illusion given by the twisted hanger. It does sit very very close to the spokes in first gear. The unit is quite springy so i feel it's inevitable that soon enough it's going to get chewed up in the spokes.

    The joys of biking eh??
    I don't know enough to make smart r's remarks about peoples choice of parts 'n' things, yet!
  • The RookieThe Rookie Posts: 27,802
    If the high stop is set correctly (read parktools) the mech cage should never hit the spokes even if it's a bit springy....
    Current steed - Whyte T129, 2013 frame, mongrel Revelations, Giant dropper, Stans S1 wheelset. 12, Magura Trail Sport brakes, 1x11. 12.8Kg
  • mrmonkfingermrmonkfinger Posts: 1,452
    It does sit very very close to the spokes in first gear. The unit is quite springy so i feel it's inevitable that soon enough it's going to get chewed up in the spokes.

    There's a couple of adjustment screws on the derailleur that will stop this from happening :)

    http://www.pinkbike.com/news/tech-tuesd ... -2010.html
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