Cranky crankset. Double v triple?

Discussion in 'Cycling Equipment' started by gurchin, Jul 10, 2010.

  1. gurchin

    gurchin New Member

    Joined:
    Jul 10, 2010
    Messages:
    4
    Likes Received:
    0
    I have a one year old flat-bar hybrid bike that I use for commuting equipped with an FSA vero triple crankset, non series shimano front derailleur and shimano 105 rear derailleur.

    The problem is that the front derailleur seems quick to go out of whack - needing constant adjustment to keep the chain from rubbing or shifts from missing. For what it's worth I also think the rotation and shifting of the front crankset are less "smooth" than they used to be. There is some minor wear starting to be visible on the outer ring and a perhaps a bit more bearing noise, but other than that it is clean and functional. It has been ridden about 1500-2000mi.

    I looked into upgrading to a shimano 105 compact double but this seemed like an expensive proposition since it would also mean new rear derailleur, shifters, in addition to the crankset and front derailleur.

    Would anyone please weigh in with their thoughts/experiences on whether simply upgrading to a higher end triple crankset and front derailleur (eg shimano 105) would give more crisp shifting and require less fussing (than the current setup)? Or is this just an inherent property of any triple crankset setup?
     
    Tags:


  2. tafi

    tafi Member

    Joined:
    Jul 31, 2003
    Messages:
    1,038
    Likes Received:
    17
    I would always suspect FD setup first. This is by far the cheapest thing you can do (free) towards rectifying the problem, so if it doesn't work you haven't wasted any money.

    Ask yourself (or your derailleur) the folloing:
    -Is it set at the right height (no more than 2mm above the teeth of the largest chainring?
    -Is the inside plate of the cage parallel to the plane of the chainrings?
    -Are the limit screws set correctly?
    -Is the cable tension appropriate?
    -Is the cable clamped tightly enough and not allowed to slip?
    -Does the cable run correctly through the fixing bolt (if it loops around it that changes the leverage and the pull ratio)?
    -Are there any barrel adjusters on the FD cable which have broken or been screwed out of their threads?
    -Is the mounting bolt tight enough to prevent twisting of the derailleur under cable tension?

    All of these are possible causes (occasional FD slip especially). your problem should be traceable to this most likely. Wear of the chainrings shouldn't play into this too much but replacements aren't hard to source anyway.

    I personaly would avoid upgrading anything on a flat bar (it serves no other purpose apart from getting from A to B) unless a part was actually found to be broken and an equivalent at the same level wasn't available.
     
  3. PeterF

    PeterF New Member

    Joined:
    Sep 13, 2004
    Messages:
    983
    Likes Received:
    0
    Personally, I would always choose a double (compact)over a triple unless I absolutely needed the super low gearing a triple provides. Even on my MTB, I rarely use the small ring. BUT, it sounds like your FD needs adjusting as was just mentioned, so that would be my first action.
     
  4. gurchin

    gurchin New Member

    Joined:
    Jul 10, 2010
    Messages:
    4
    Likes Received:
    0
    Much thanks for the advice. I understand the preference for a compact crankset - I guess I'm trying to minimize unnecessary transfer of wealth to shimano. :)

    Right on about the FD. I have the height, limit and rotation pretty well dialed, though I find it settles a bit every 50-100 mi.

    Having said that I find even under the best of adjustment the front shifting is far less crisp than it used to be. The rear shifting is still perfect.

    Does the FD itself typically wear out?
     
  5. PeterF

    PeterF New Member

    Joined:
    Sep 13, 2004
    Messages:
    983
    Likes Received:
    0
    They last pretty long but they are magnets for dirt and grime. I have had friends ask me to service their bikes and the front d's were pretty much frozen due to lack of care. Also, the front d cable and housing should be cleaned and replaced as needed.
     
  6. gurchin

    gurchin New Member

    Joined:
    Jul 10, 2010
    Messages:
    4
    Likes Received:
    0

    Sure enough when I used the compressor I managed to dislodge some coarse grains of sand in the FD, but I guess they may be minor. I did get very good results out of taking up some cable slack... Shifting up is still a bit sluggish but definitely not bad, and the chain rub is gone (for now). Can't wait to adjust it next weekend!

    Also I brushed off the repair manual and checked out the wear on the largest chainring. A few teeth are getting a bit worn, but no chain slips yet and none are badly bent. A few are a bit short.

    However I did notice 2 things: the first is that I have a small/fair? amount of chain stretch (just under 1/8" between links 6" apart). The other is that there is a noticeable side-to side crank wobble. This is seen as movement of the chain side to side relative to the FD cage in rotation (a bit more than 1-8" L-R).

    I read that crank wobble is normal. Is there a measurable amount that is Ok?
     
  7. swampy1970

    swampy1970 Well-Known Member

    Joined:
    Feb 3, 2008
    Messages:
    10,057
    Likes Received:
    185
    Crank wobble?

    If you mean being able to grab both crank arms and yanking it side to side and feeling a slight 'clunk' - well, that aint normal. That's a sign of a worn/badly adjusted bottom bracket or cranks that are on the verge of being useless.

    If you mean that the chainrings, when viewed from above, don't track perfectly straight when you spin the cranks - that's not ideal but some of the cheaper cranks do this. So do some of the expensive ones after a crash...

    As for the shifting woes, replace both the inner and outer cables and degrease the front mech and the cable guides on the bottom bracket. Get in there with a stiff paintbrush (or similar) and some degreaser that's water soluble. Get it clean and then lube with oil.

    Ensure that the outer plate for the front mech is parallel with the chainrings and that you only have about 1 to 2mm between the top of the teeth and the chain guide on the front mech. If you have to adjust every couple of weeks then it may be that you're not tightening the cable clamp enough or there may be some grease or goop in there. Goto the shimano website, select cycling, select North America... Then goto the Tech Support - Tech Tips and Tech Docs section for help on how to properly set up your ride.

    The shimano North American website seems to have a few bits and pieces in the Tech Support section that aren't in other areas.

    Good luck.
     
  8. tafi

    tafi Member

    Joined:
    Jul 31, 2003
    Messages:
    1,038
    Likes Received:
    17
    Now we are getting to the bottom of the problems.

    A normal bike chain has half inch pitch and is generally specified for no more than 1% wear (increase in distance between every second pin). Six inches should be 6 full links (12 half links or pitches). The usual specified allowable wear should lead to no more than 1% increse in length. That means your measured length should be no more than 6.06".

    6.125" is more than double the specified wear, and replacing your chain at this spoint will also require replacement of at least the cassette.

    Short teeth on chainrings are not necessarily a problem, some of them are cut that way to aid shifiting. Wear will show up as a "shark fin" shape developing on each tooth.

    Secondly, a warp in the chainrings is not uncommon on lower spec cranks (even on some new bikes). I've never measured it on the bikes where I have noted it, but 1/8" sounds like quite a lot. It is far from desirable as it affects how the FD must be set (effectively 1/16 wider at each limit of motion than desired - for your case) and definitely affects FD operation. I'm not sure if this is a function of the chainrings alone or a result of a mis-shapen crank spider or both.
     
  9. gurchin

    gurchin New Member

    Joined:
    Jul 10, 2010
    Messages:
    4
    Likes Received:
    0
    Thanks again, you've given me some good ideas on things to check on. The "wobble" is indeed of the latter variety (i.e. the chain ring doesn't track straight).

    I'll investigate further and post back when I've made progress.... As an aside did get a lovely commute ride in today.
     
  10. TGIMerv

    TGIMerv New Member

    Joined:
    Sep 17, 2010
    Messages:
    4
    Likes Received:
    0
    Just wondering if anyone has tried to repair a rip in a cycling jacket.
    Couple weeks ago when the weather was starting to get cooler in the early mornings, I bought a Pearl Izumi Slice jacket.
    Went out on a cool ride in the morning, got about 10 miles in, not paying a lick of attention, ran off into the grass, tried to jump it back on the paved trail, MISSED, and down I go.
    Other that it knee scrap, put a 5 to 6 in rip in the left side back of the jacket.
     
    Anyone have any ideas on trying to fix? I know Duck Tape, thought about that, so that's one possiblity,
    Iron on patch? How would the heat work on that vinyl type material?
    Just wear it like I have been until it is unwearable?
     
    Thanks for any thought or info,
    Merv
     
  11. Aussie_Al

    Aussie_Al New Member

    Joined:
    Jul 24, 2010
    Messages:
    95
    Likes Received:
    1
    Most guys I know just turn it inside out and use a piece of duct tape to patch it up
     
    You could also use clear sealing and repair tape, this clear tape is non glossy and has a matte finish
     
     
  12. davereo

    davereo Well-Known Member

    Joined:
    Jun 17, 2010
    Messages:
    1,639
    Likes Received:
    70
    Welcome Merv to cycling forums. How about trying to find some reflective duct tape. Maybe you can use two strips one on the other side of the jacket to match the rip you are trying to repair. Luckily it was the jacket that got the worst of it./img/vbsmilies/smilies/rolleyes.gif
     
  13. 64Paramount

    64Paramount Active Member

    Joined:
    Jul 25, 2009
    Messages:
    1,640
    Likes Received:
    34
    Welcome aboard, Merv.
     
    You could also try some of the cloth tape used to mend book covers or some of that cloth tape used for hemming pants legs. I suspect you could find both types at Wal Mart, K Mart, Wal Greens, etc.
     
     
  14. TKOS

    TKOS New Member

    Joined:
    Oct 6, 2004
    Messages:
    387
    Likes Received:
    0
    You can buy a product called liquid stitch at many fabric stores. And camping stores often sell something similar called seam repair. It is a liquid rubber glue that you could use to essentially glue the pieces back totterer. I did it with my tent and it holds well, I would buy a piece of rip stop nylon or a tent patch and do the repair on the inside of the jacket.
     
  15. decca234uk

    decca234uk New Member

    Joined:
    Jan 18, 2010
    Messages:
    130
    Likes Received:
    2
    I'd go with the duct tape while looking for a new one on Ebay. i've had some real bargains with cycling clothes on ebay. I got a great jacket for 15 quid down from 91 because it had some slight imperfection in the side of the reflector on the back. I couldn't even see it, best jacket I've ever had.
     
Loading...
Loading...