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As mentioned above...I'm running a 50/34 10 speed with 11-32 cassette but would like to change to a configuration that would make climbing hill easier.

I live in a hilly area so every time I cycle, I can't avoid hills almost immediately, averaging 5-11%. So for a recovery cycle, I still can't avoid pushing high watts. I'd sacrifice top end speed and even tolerate gaps in the gear ratios elsewhere (which I know would make my cadence uneven here and there) to make the hills easier to climb. I enjoy high cadence so spinning going up a climb is my preference. I don't race so basically challenge myself at times and then need recovery rides.

Is it an option to go for a 11-34 or 11-36 even with current config of 54/30 10-speed or maybe shoot for an 11-speed 11-32 or would retaining my 10-speed 11-32 and instead opt for changing the 54/30 compact to something else? My preference would be to make the changes on the cassette end if possible. I have a new 105 long mech so that should not need to be changed at least, so possibly only the cassette.

Looking forward to hearing your thoughts/suggestions

  • How much do you weigh, and what do you consider "high watts"? You may need to put up "high watts" just to go fast enough to stay upright on an 11% grade, and no amount of low gearing will help that. For example, it'd take 270W or so to climb an 11% grade at 5 mph/8 kph if the total rider + bike weight is 100 kg. – Andrew Henle Aug 1 '19 at 9:14
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    Welcome to the site. If you have a 10 speed 105 5700 GS rear mech, their specification is up to 28t max cog. You're running a 32, so pushing the envelope already. be prepared to experiment through your wallet, to swap the rear derailleur out for a 9 speed mtb one, or to consider changing the front chainset. How much lower are you able to place the front derailleur? is it band on or clamp on? consider adding a photo – Swifty Aug 1 '19 at 12:15
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    Thank you - I'm 56kg ( around the 9st mark) just took up cycling a year or so ago after hanging up the distance running shoes, so a real beginner. with an ftp of 145w I'm under pressure on a hill of about 8% at 200w which is manageable for a few miles but for a recovery cycle I'm already working hard, I'd prefer to spin higher and cover less ground just to get over the hill – Pat T Aug 1 '19 at 18:23
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You are already pretty close to the limit of what can be achieved easily. You could certainly stick a 34t cassette on there, but it's not going to make any appreciable difference over a 32t.

The next step is a 36t cassette, which is likely to need a MTB rear mech (9 speed XT mech works well with 10s road shifters).

Another thing you can consider is a subcompact 46/30 chainset. Making both changes would give you a 30/36 gear ratio, which is extremely low for a road bike.

If you know your target power (z1 for a recovery ride) you can use the following websites to calculate the gear ratio you need.

http://bikecalculator.com/ https://www.bikecalc.com/speed_at_cadence

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The largest specified cassette sprocket size for the 10 speed Shimano 105 5700 series derailleur is 28 teeth, for both SS and GS versions (see here), so you are already pushing the limits of the derailleur.

The max cassette sprockets on new 11 speed Shimano derailleurs are only 30 or 32 (although the Ultegra RX800 will take a 34).

A sub-compact 48-32 or 46-30 crank will get you low ratios but you will of course lose your high ratios.

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  • The 105 5700A GS is specfied for 30 teeth. See here – Ross Millikan Aug 1 '19 at 21:30
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Wolftooth makes the roadlink that allows you to shift larger cassettes with standard road derailleurs. You should easily be able to go to an 11-36 cluster with the roadlink and a 105 rear triple.

The difference between an 32 and a 34 or 36 with a 34 in front is significant. While the difference in gear inches/ratio isn't that big in absolute numbers, the relative changes do make a difference.

34/32 = 1.06

34/34 = 1.00

34/36 = 0.94

While those numbers look very close, 34/34 is 6% fewer watts, 34/36 is roughly 12% fewer watts. That can be the difference between redline and just cruising along.

However, if your budget allows, my preferred solution would be to switch to the newer 46/30 "gravel" cranksets with an 11/32 rear cluster. Unless you are riding in a pack at lot at speeds above 40 kph, a 46/11 is plenty high enough for most riding. The problem with 50/34 is that for me at least there is an awkward speed on rolling terrain where I'm fiddling between big/big and small/small. Compact cranks work best IMHO when you can do most of your riding in the big ring and keep the small ring for climbing. I've been riding a 46/30 11-32 for a couple years now on my road bike and for me it's a great replacement for the typical road triple setup.

The problem with 46/30 is that your front derailleur might have problems shifting a 46/30 if you have a frame mount derailleur. Since you are pushing the curvature limits of the derailleur with a 46t, it's important that you be able to get it within the standard 3mm limit. Often frame mounts don't allow you to move the derailleur low enough.

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  • Thanks for all the details and options .... I'm thinking that the 46/30 is the way to go, seems the most appreciable gain, so I Just need to see if front derailleur will be problem-free. Your suggestion is similar to Argenti Apparatus too and I'm fairly close to the limit on my current cassette now anyway...what would be the typical top end loss I'd have with the 40/30 ? just mean higher cadence than I currently do ? I never really exceed 35km/h on a steady flat cycle or 50km/h on a long downhill so I push really low watts – Pat T Aug 1 '19 at 19:02
  • @PatT There is a great set of gear ratio calculator tools here bikecalc.com that you can use – Argenti Apparatus Aug 1 '19 at 21:01
  • Great stuff, let me check bikecalc out next, cheers – Pat T Aug 4 '19 at 0:05
  • It is really strange how the consensus can differ on two similar topics under two questions on this site. bicycles.stackexchange.com/questions/38302/… Here they mostly say that 34/30 is too spinny and one should be fine or better-off with 34/28 for road riding. Personally, I would have welcomed a sub-compact on my bike, but the upgrade does not make sense financially. – Vladimir F Aug 9 at 15:08

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