Change big chainring, cassette range, or?
 

I am a spinner, most comfortable pedaling around 95 rpm. I will sometimes drop to the mid-80s on a false flat, but it feels weird. Currently my road bike has Tiagra 4700 with a 50/34 front and 11-32t rear. I use the larger half of the 11-32 almost exclusively, so I'd like tighter gear spacing in what's currently the middle of my gear range because I find myself regularly jumping between 100 and 90 rpm while gear hunting. What would be better/easier/cheaper: getting a smaller big chainring for the front or getting a cassette with tighter spacing such as a 12-30t? Or is there a better option (other than getting used to pedaling slower-- tried that for a month of commutes, never got used to it).

I ran a half step with granny for a couple of decades. It was great as long as I was happy with the 42t middle limit (campy NR 41T rings are rare). But as I aged and wanted a more robust middle range that middle ring had to shrink. Now many of my bikes have a 26/36/46 (or close) and I really like it. As I am now fully indexed (and enjoying the wonders of Shiftmate conversions) my rear cogs have found the useless 11 and 12 tooth cogs. What one hand gives the other takes away. My kingdom for a 13/35 9 speed cassette:) Andy

The best solution depends very much on which ratios you use the most often and what total range of gears you require. However, just changing the chainrings, when you prefer a rather narrow range of cadence, will not solve the problem, because your wide range cassette will still have the same jumps between cogs. A half-step is not for everyone, and a more compact cassette alone may still not meet your needs. I would suggest you track where the holes are and then use a bike gear calculator (Google it) to see whet options will work best for you, of course factoring in the expense..

Unfortunately, the choice of manufacturers to make both an 11 tooth small cog and a 50 tooth larch chainring standard creates extra expense for those who want the maximum amount of useable closely spaced gear ratios on a stock bicycle. A 48 tooth chainring and a 12 tooth small cog would have both made much more sense. I'm with Andy on bemoaning the lack of stock cassettes that don't start with a downhill-only small cog.

I would just throw a tighter cassette on there. If you can give up your 30 tooth low gear, maybe a 12-28, those are easy to find. You didn't say how many cogs you're running, but it's basically a matter of figuring out your lowest usable low gear, and highest usable high gear, then let the chips fall where they may on the gears in the middle. The closer together those two numbers are, the tighter the middle gears will be, and that's what you want.

Or if you know the precise sprocket teeth you use the most, build your own cassette. I have one that's closely spaced on the middle gears up to a 24 teeth, then I stuck on a 32 tooth emergency bail-out gear for when I die on climbs. Manufacturers won't sell a cassette like this because it looks kinda funny, but I find it practical.

http://www.gear-calculator.com/

Plug in what you have now and play with options. Most people compare % step increases, but I prefer to compare km/h changes when shifting. Because at high speed a 10% jump is more significant than at low speed.
I never knew the half-step chainring. But I think with higher speed options (9, 10, 11..) this seems redundant nowadays?

I would suggest getting the 12-28 cassette.

Bicycle Gear Calculator

I'm currently running a 38/48 with a 12-27. I like it, most of my riding is fairly flat and I generally ride alone (no drafting). I may switch the big ring with a compact to have a 38/50 and a 34/48.

How difficult is it to acquire parts and build a custom cassette? I'd like to keep the 32t for steep hills, but I can basically forgo the 11 and even 12 if I could get smaller spacing between 18 to 25 since I like to cruise between 15-20 mph @ 95 rpm.

Playing around with the gear calculator, maybe I should just be in the small ring...

Generally, you should be able to put together a custom by buying two of the cheapest cassettes, as those are the ones most likely to have individual sprockets rather than clusters that are pinned together. But you will likely run into the lack of bigger 1st position cogs as those are a different internal shape than the rest of them.

However, Miche and Shimano offer cassettes for Junior race gearing, so there are modern cassettes out there that start on a 14 or 16.
https://www.bike-discount.de/en/buy/...CABEgJCJfD_BwE

13, 14 and 16 start cogs:
https://www.probikeshop.com/en/gb/mi...ano/71241.html

The cheap tiagra cassettes does not have loose cogs. They are all pinned together, except the two smallest cogs.

Are the pins structural, or just replacements for the screws Shimano used to use? Unless the cogs you want to swap out are on some sort of carrier, you can remove the pins.

It looks like 4700 cassettes are solid steel for 10-4, with a carrier unit for 3 to 1. That should work if it is the higher gears are the ones you want to exchange.

Or use Miche or SRAM cassettes instead.

Im not sure, but I think they are pinned. No loose cogs for sure. I think carriers are reserved for 105 and Ultegra level, to save weight.

like this:

And you can drill the heads of those pins out, and end up with this:

https://cimg8.ibsrv.net/gimg/bikefor...3070dbcd6e.jpg

I believe some versions of the 4700 cassette are built this way, with a carrier for the lowest 3 and loose cogs pinned together in the middle. But the pins aren't structural, and they used to be removable screws. You can use the cogs that don't come on alloy carriers individually to mix and match once the pins are out.

So I should be able to remove pins from my 4700 cassette (and whatever donor cassette(s) I scavenge cogs from),
then swap individual cogs,
then remount the cassette

?

Would I need to reattach the cogs or can they just be kept together by the pressure from the lock ring?

It seems that I'll have to do something about my cassette soon. I think one of my cogs is worn, because it's the only one that I experience chain jumping when I stand to pedal, and I don't think it's a chain issue because my original chain wasn't yet at 0.75 (after ~1,3000 miles) when I installed a brand new chain.

The junior racing cassette would be an interesting option, but I prefer to keep the largest cogs since I just started riding up the local mountains and I'll blow out my knees without them.

Those pins are just there to make it easier to mount the cassette. In the old days those pins were screws, and lots of people would simply leave the screws out as they made disassembly for cleaning harder.

But it shouldn't be hard to combine the low end of a wide range cassette with the high end of a junior cassette so you end up with closer ratio gears. And the cogs you take out may even make for a reasonable cassette that you could resell.

http://cycleseven.org/customising-sh...deore-cassette

seems like people love over complicating things. You want to ride in the tighter section of your cassette and want to keep that 32 in the back for hills right? Replace your 50 tooth chainring with a 46 tooth boom your done. Cheap and easy. Only thing you are giving up is being able to pedal at 35mph which nobody is doing much of anyway.

Seriously. Tons of quality 46t chainrings out there as it's a pretty standard CX gearing choice.

Hmm, but if I understand correctly, the TIagra 4700 is odd in that it's 4-arm 110mm BCD, and I'm having trouble figuring out what is compatible with it because most chainrings that I've seen are 5-arm except pricey 11-speed chainrings of the Ultegra/Dura-Ace level. Are there any decent, cheaper options?

If you want to get down into the middle of your cassette, then I would do what Canker above recommended - just get a smaller larger chainring. I like a close ratio cassette, and I used to use a Campag 13-26 (13-14-15-16-17-18-19-21-23-26) with a standard 53/39 crankset. However, for normal flat/rolling terrain, I found that I was spending most of my time in the larger end of the cassette, and not getting the benefit of all those nice consecutive smaller cogs. I swapped the 53T for a TA Zephyr 50T large ring, which dropped me right into the center of the 13-19 "corncob", leaving the large cogs for climbing. Later, having moved to a less hilly region, I swapped the cassette for a 12-23 (12-13-14-15-16-17-18-19-21-23), gaining a 12 for better top end, and losing the 26 which didn't get used anyway. With the now 50/39 crankset, this is an ideal combination for me.

That link doesn't work. Does TA make Shimano compatible uneven spaced chainrings?