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Chain Rings - technical question

ZacniciZacnici Posts: 1,385
in General Chat
Saw a chap at a recent event who had the same bike as me - Focus Tria - and noticed he had a different chain ring. Said as he was ' a short legged runt' - just like me - he was having problems using much of the 53T ring and wanted to tackle hills better and so swapped the 53/42 for a 50/38 and reckoned it was the bees knees. Must say such a swap intrigues me as I do not manage to pull many gears on the big ring myself. I didn't see him again but he did say something about chain lengths and cross chaining I think and or something to do with chains and also about gear spread as I was having difficulty with his accent (sorry chum).



I just had a look at an online chain length calculator and figured out that with a chainstay length of 40cms the original 53T/28 combination chain length would be 137.16 cms or 54 links and that the new combo 50T/28 would have chain legth of 134.62 or 53 links - does that sound right? If so mightily pleased at my expanding knowledge.



Does anyone see any problems about swapping to a 50/38 combination?



Thanks as always for any suggestions etc.

Comments

  • transittransit Posts: 163
    That combination sounds ok to me, I know some standard compact chainsets are 50/34 so it's better than that. I don't know about the chain length calculations, is there not a recommended way of measuring it by wrapping the chain round the biggest ring and cog (not thro' the derraillieurs) and then using a certain length derraillieur dependent on smaller chain ring??? - hmm, more questions than answers, sorry!



  • learnerlearner Posts: 100
    i recently changed my 52/39 for a compact 50/34. What a difference. I am able to manage my heart rate and cadence a lot better without losing too much top end. One thin I found was i had to change my bottom bracket as the compact had an axel thingy so it used external bearing type as opposed to the origonal one.

    As for chain length, laymans point of view, is one link going to make that much difference? if you take it out and ever want to put the bike back to origonal it will mean a new chain.

    Can you try a shop bike or a friends with a compact before commiting?

  • ZacniciZacnici Posts: 1,385
    Had a look at a couple of chain length calaculators and they both came up with the same result which I can see if dropping a chain size. Also dug out my old bike with a 50/39/30 and yes there is definite difference in the cadence although the geometry, running gear etc was not as good so then hopped on a friends 50/34 which was very nice so a chainring change is defitinitley on the agenda.



    Thanks to all
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