Question re 33T and 49T Chainrings

Barrington12
Barrington12 Posts: 358
edited February 2015 in Workshop
Looking for a bit of advice here...
I need new chainrings and a friend has brand new 33T and 49T rings which are unused and not needed by him, and which he is prepared to sell to me for a good price. I currently have 34T and 50T so hardly any different and with a couple of big trips planned this year in the mountains the very small difference it will make will be beneficial I guess.
Question is that on my bike I have a braze on front derailleur and it is currently positioned at the lowest point on the frame, so will the 49T ring be okay ? In other words, how much smaller in diameter is a 49T ring compared to a 50T ring? Will I be able to set it up okay or will the gear change on my front rings be compromised?
Hope this makes sense. Thanks.

Comments

  • keezx
    keezx Posts: 1,322
    Most likely won't be a problem.
    How much is the cage over the big ring now?
  • Barrington12
    Barrington12 Posts: 358
    It's approx 3mm at present.
  • imposter2.0
    imposter2.0 Posts: 12,028
    TBH, if you are looking for a lower gear range, then one tooth off each ring will make next to no difference. If it's climbing gears you need, then it makes more sense to switch the cassette, or buy a triple.
  • Barrington12
    Barrington12 Posts: 358
    TBH I'm not especially looking for more climbing gears, although any small benefit helps. And I realise that a bigger cassette would be easier (along with the usual 'lose a pound or two'), I was just asking about the size of the chainrings. Thanks.
  • mamba80
    mamba80 Posts: 5,032
    The difference in diameter is "about" 3mm, so the additional drop from your FD will be half that.
    I just measured them for you, its not exact as the shimano CR has profiled teeth and the TA chain ring doesn't.
    I do not think that having a 4 or 5mm gap will make any noticeable difference, also, we ve found no difference in gear shift using TA rings and shimano ones (I assume you are on shimano?)
  • Barrington12
    Barrington12 Posts: 358
    Excellent, thanks, that's good information. Current rings are SRAM.
  • keef66
    keef66 Posts: 13,123
    I just put a CX chainset on my winter bike so the big ring is a 46. I've dropped the front mech as far as I can; the lower bottle cage bolt is stopping me moving the band on clamp any lower. The mech cage is about 6mm above the big ring, but front shifting is excellent, so I don't think you'll have any problems.
  • 6wheels
    6wheels Posts: 411
    I've just swapped a 50t chainring for a 46t on my Synapse 6 which has a braze on front mech. The mech is more than 10mm above the big ring because of the lack of adjustment, and at the moment I'm not having any problems...to my surprise.
  • ugo.santalucia
    ugo.santalucia Posts: 28,312
    6wheels wrote:
    I've just swapped a 50t chainring for a 46t on my Synapse 6 which has a braze on front mech. The mech is more than 10mm above the big ring because of the lack of adjustment, and at the moment I'm not having any problems...to my surprise.

    That mirrors what I experienced when I swapped a compact for a CX chainset... I thought I had to lower the front mech, but as a matter of fact there is no need to
    left the forum March 2023

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