@SatNavSaysStraightOn can I ask why the gearing suites you better these are the two tables for the gears in inches
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Dawes on the left and Triban 5 on the right, the three figures on the right of each table top the number of teeth the F.D. needs to cope with, the middle the number of teeth between max an min gears on the cassette.and the bottom the over all teeth the R.D. needs to be able to cope with, I belive the 2013 Sora can cope with at least a 27th rear cassette so if you need lower than 31.56" the 27th will give you 29.22" the
CS-HG50 12-13-14-15-17-19-21-24-27 ( £12 at chainreactions) though I did find the 21-24 a big jump yesterday, apart from that 1.21" on the the low, the Triban has better stepping and a greater range, and if its a standard 74B.C.D. you could opt for a 28th inner ring giving this
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A Stronglight 74BCD can be had for about a tenner, just my thoughts though.
So you could for about £25 extra have this gearing on the T5
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Sorry to hear the T3 died though.