105 Chainset problem. Now officially fed up

dragonontheedge
dragonontheedge Posts: 496
edited July 2011 in Workshop
I have a 2008 Allez 18 which I am upgrading.

I have a 9 speed 25/11 rear cassette and was, until today, running a Sora 50/34 compact up front with a 105 BR5600 front mech.

Today I fitted a 105BR 5600 compact with the same 50/34 ratios.

The chain is a 10 speed narrow.

To the problem. Whilst on the lower front 34 and on the rear 11 the chain keeps fetching up on the 4 pins to the back face of the 50 tooth front chain ring. The angle of the chain when running this ratio appears to be the problem.

THe chain rings on the 105 compact run a little closer together than they do on the Sora.

Any help in curing this would be greatly appreciated.

Thanks in advance

Al
Hey, maybe you haven't been keeping up on current events, but we just got our asses kicked, pal!

Comments

  • desweller
    desweller Posts: 5,175
    You shouldn't run such an extreme chainline. When you run small-small or big-big you are placing high side loads on the chain which will greatly accelerate wear and also lead to poor shifting performance.
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  • Nevertheless 34/11 should still function fine, sounds to me like you've got your chainline wrong, crankset too near the frame or an extra wide hub on the rear pushing the cassette outwards.
  • Bobbinogs
    Bobbinogs Posts: 4,841
    I think this is a bit like the Tommy Cooper sketch where he went to the doctor and said "it hurts when I do this", to which the doctor replied "well, don't do it". As Des states, crossing from 34 to 11 is frowned on for lots of reasons so if you only get a problem when in this combo then shift earlier/later to avoid it.

    You probably had good reasons to upgrade but I can't think that the current chainset (10 sp front end, 10 sp chain and 9 spd rear mech/cassette) will be that much better than the all sora kit.. Are you sure of the compatibility?
  • markos1963
    markos1963 Posts: 3,724
    Nevertheless 34/11 should still function fine, sounds to me like you've got your chainline wrong, crankset too near the frame or an extra wide hub on the rear pushing the cassette outwards.

    I haven't come across a compact set up that does run fine on this extreem, be it 9 or 10 speed. The inner ring is just too small to allow clearance for the chain not to hit the outer ring. Fitting a 36t inner can help.
  • rake
    rake Posts: 3,204
    why anyone would use this gear beats me. however turn the inner ring over can give a little more space between them on some shimano sets because the bolt hole tabs are slightly offset from centre.
  • flasher
    flasher Posts: 1,734
    So you're running a 10 speed chain on a 9 speed cassette, well that ain't going to work very well to start with.

    Your upgrade path should have been, 10 sp. shifters, chain, cassette, then RD, FD and lastly chainset