tomtomtom123

I have a Shimano RD4700 rear derailleur with 12-34T custom 10 speed cassette that I mixed and matched myself. With a 44/24T front double crank. This gives me a 519% range = 44/24*34/12. The lowest gear gives me 24/34 = 0.706 ratio. The RD4700 is rated for up to 34T cassette and a 41T chain wrap, but I'm using 42T wrap and have tried up to 44T wrap, if the small-small combination has the pulleys dragging on the chain, but it doesn't matter since I am never on the small-small.

Your 11-32T with 50/34T is = 50/34*32/11 = 428% range. Your lowest gear gives you a 34/32 = 1.0625 ratio.

If you increase the rear cog to 36T, then you get at the lowest 34/36 = 0.944 ratio, or a 1.0625/0.944 = 12.5% drop, which feels like 1 gear lower. Also the range changes to 481%.

However, if you're really having trouble on the lowest gear, you might want at least a 30% drop, or a 0.81 gear ratio, which feels more like a 2 gear drop.

You currently have a 16T jump on your front chainring. I've done 20T jump without any problems, as long as you install a chain catcher and fiddle with the FD angles and cable. I was also able to do 22T jump but was more complicated to adjust. So if you want to keep a 50T then you could match it with 30T for a 20 jump. However, 110mm BCD will only allow you to go as low as 33T, which you can get from TA or spacycles. If you want to go lower than 33T, the FSA with 30T has 80mm BCD but I had asked before and they don't make any other sized chainrings for 80mm. The minimum teeth physically possible for 80mm BCD is 26T, so if you have a CNC machine, you could take a 26T with 74mm BCD and drill out new holes at 80mm. Otherwise, get a crank with 110/74mm and your minimum possible teeth drops to 24T.

If you drop your small chainring to 30T and keep your max 32T rear cog, you get a 0.9375 ratio. It's practically the same as changing to a 36T max rear cog. But the benefit of changing the front chainring instead is having closer cassette spacing. My custom mixed cassette has big spacing at the bottom and small spacing at the top. 34, 28, 24, 21, 19, 17, 15, 14, 13 ,12. Some of the Shimano cassettes don't mix well though. I have another thread explaining my experience attempting to mix 4 different sets of Shimano 10 speed cogs.

With an 18T jump in chainrings, if I increase the chainring spacings by inserting 0.1-0.2mm shim washers, I can go up to 8th gear on 10 speed while on the inner chainring before the chain starts to rub on the outer chainring. With a 20T jump, I can only go up to 7th gear. But 7th gear on the inner chainring for me is somewhere between 2nd and 3rd on the outer chainring. So there is only 2 usable gears overlapping. So I have 15 unique gears in a linear shift.

With the small-small combination with 24T chainring, the chain will start rubbing on the chainstay, but since I'm never on small-small because I can only get up to 7th gear on the small chainring, it isn't a problem for me. For quick estimate of chain clearance, you can take 1.0" x 25.4mm / 3.1415 = 8.09mm difference in chainring diameter for every 2 teeth, since 2 teeth is a change of 1.0" in circumference or chain length.