Originally Posted by
KCT1986
If you go with a 50/34 crank, an 11-25 cassette will give you a reasonable low gear. Probably enough for non-mountainous riding. Or an 11-28 cassette if you stay away from small/smaller combos that require more chain take-up.
You can run the gear inch calculations and compare it to what you have on your other bikes.
I currently have a hybrid type bike with 48/38/x and 11-30. With the kid trailer I never go below 38-20, and alone it’s around 48-17…. It’s all flat around here. Thinking a 50/34 and 12-25 will do nicely. I’m leaning towards spending the extra $150 for all new 105 kit since the current shifters need covers, cassette needs a spacer, and probably will run into a few bucks here and there that will make me regret trying to salvage the current setup. I read the st-6700 is (was never) the greatest and even modern Tiagra is an upgrade.