Just switched from an 11-28 cassette with a 50/34 chainring on my tri bike to a 11-34 cassette to a 48/32 chainring.
I swapped out my cassette from an 11-28 to an 11-34 for climbing, but my bike shop blindsided me and switched my chainrings from a 50/34 to a 48/32 without telling me.
What benefits are there to switching?
I had been running a 52/36 on my 650C bike for many years. I’ve had no problems with gearing for the speeds I ride.
It’s like running a 48/33 on a 700C.
Just go here and plug in the numbers for both chainrings/cassettes
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What is the terrain like where you train and race? 48x11 will get you ~31mph at 90 rpm vs 33mph with a 50x11. If you have the power to hold that speed on the flats, or have a course with a long gentle downhill, that could make a huge difference. If you are riding steep grades, having the 32x34 granny gear might be more beneficial because on the downs you’ll be coasting at 40mph+ and gearing won’t matter.
Personally, I think going past 1:1 in gear ratio is overkill for the road, but if I lived in the Alps or somewhere with long sustained climbs >10% I’d probably feel differently! We’re only talking ~5% difference in gear-inches between the two, so I’d probably just ride it and see how it works for you.
What is your crank length?
That’s gravel gearing.
It’s not ideal for TT’s, triathlon or road racing, but you could get away with.
I’d go minimum 50/11 for TT, triathlon or road racing, but more likely 52/11.
Unless you’re racing Embrunman or Alpe d’Huez triathlon, why would you want a 32-34 as easiest gear? Regarding the top end, ~45 km/h should be plenty for most (unless it’s a gentle downhill as mentioned before), but that’s on an inefficient gear. For the Taupo course I’ve gone the other way and mounted a 56-42 with an 11-30 (11 speed) at the back, just to be in a more efficient gear most of the time (~41-42 km/h on the flats).
The gearing was good enough for me to do 60 min 40K’s and 2:25 HIM rides.
The only time I needed to go bigger was at Triple T where there were extended downhills
What is your crank length?
155 mm
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The gearing was good enough for me to do 60 min 40K’s and 2:25 HIM rides.
The only time I needed to go bigger was at Triple T where there were extended downhills
Most of the trend to bigger chain rings is not being faster down hill, but being able to ride in the middle of the cassette most of the time on flats.
Being in the 11 or 12 on the cassette is not very efficient as the chain is out of alignment.
Did you ask the shop why? I hope they didn’t charge you for this swap. Unless you were having serious difficulty climbing before, I’d definitely be asking them to switch it back.
52/14 on a 650C bike is 24.5 mph at 90 rpm. That’s not far away from the center.
Nearly the same as a 48/14 on a 700c bike. Just above the center of the cassette.
Using a 50 gives you 1 mph in the same gear or gives you .5 tooth in the rear. Not really a change that will move you to the center of the cassette.
Going to a 53 only gets you 1 more gear closer to the center over a 50. If you are a 75 rpm person you’re going to be in a 53/13 and towards to the small end.
You’d have to go to a 60 tooth chainring at 75 rpm to get near the center of the cassette and that’s not reasonable.
I guess it depends on your leg strength and weight, and of course the severity/length of your climbs.
As I was spinning away at IM CDA in my 34/34 while others were grinding away in other ratios, I was thinking I may have made the right choice.
For many of us having a gear we can spin comfortably for as long as it takes to crest the hill far outweighs the efficiency gains of being in the middle of the block.
I am really surprised that your bike shop would just change your chainrings without asking you. Did you ask them why?
Personally, I use 53x39 chainrings, 11-28 cassette, and 155mm crank arms.
That’s why I called it gravel gearing.
Sounds like you made the right choice.
Much like I feel I made the right choice using gearing that is very similar to a 48/32
Most of the trend to bigger chain rings is not being faster down hill, but being able to ride in the middle of the cassette most of the time on flats.
Being in the 11 or 12 on the cassette is not very efficient as the chain is out of alignment.The benefit is not avoiding a slightly skewed chainline (those losses are overmatched by sprocket size gains). Efficiency is higher in a larger sprocket for a given gear length.
56-14 (108") is more efficient than 52-13 for example.
Also means a rider should stay in the large ring for as long as possible.
Hey
Can you explain to me how can i male my gearing
Shimano 105 2x11
50/34 and 11-32 to
48/32 and 11-32
Which crank set or which chainrings do i need to buy?
I only find absolutenlack but they are expensive.
Can i have 50/32 and just buy 32 chainring?
I read it that cannot 
I am old and need spinnig 
48/32amd 11-32 is more that enough for my ironman 28kmh average
Please help
It would be easier to get an 11-34 cassette.
Or even an 11-36. I’ve done that many times.