It might not shift from a 34 up to a 53.

You would want 53x39 chainrings.

Depends on the crank, but you should be able to find a 52 or 53 for the 110 bcd. You will likely need a longer chain. You may also find that from shifting is not optimal. I see cases where it works fine and others where the shift to the big ring is slow and requires more force than usual. I've also seen shift to the small ring where the chain seems to ride on top of the teeth before settling in.

Unless you have fairly low cadence, I would think that a 50x11 would be enough. It's a bigger gear than the traditional 53x12.

If a 52x36 would work for you, I love Praxis rings.

I have a 52/34 on my road bike and have no shifting issues. The only reason I don't have a 53 is because I couldn't find a good one when I was putting it together.

jaretj

if you have a compact crankset and chainrings then you're more than likely in a 110bcd and there's not many 110bcd 53T... i have read that while it'll shift from a 53/34 chainrings set up the performance of the shifts will be tremendously dimished! the only 53T in 110bcd i know of is the Rotor QXL and you could likely use a 36t which wont be a big deal in pedaling performance... i went from a rotor compact to QXL just fine been climbing on 53/29 with a 12-29 cassette without issues and not even using the 29 most of times FYI.

make the change, you'll only get stronger and smarter when it comes climbing anyways i promise you that! besides if a can do that and i used to be 225LBS+ then im sure you can do it too

---

Speed kills unless you have speed skills!!!

Why exactly are you looking to change chainrings? I personally never spin out the 50x11 on most of my bikes.

Also what range cassette do you currently use? You may be able to move to larger chain rings and a wider range cassette to keep a low climbing gear.

I have a 11-25 cassette on now. I want to change because I do find myself spinning out or spinning too high (105+ish) on some down hills.

Personally I don't consider 105 that high of a cadence but you probably prefer a slower cadence than I do.

Unless you want to swap out the entire crank maybe look at going to a 52/36 mid compact crank. If you swap out the cassette to a 11-28 you end up with lower gear than your current 34x25. As long as you don't mind the larger gaps between gears compared to your 11-25 it might suit your needs.

 
I know a pro road cyclist who runs a 52/34. It is "outside the norm" but it works fine for him and fast shifting is much more important in road racing than tri. I am in the same boat, my TT bike has a 50/34 and I need more top end. There is a specific segment of a 200 mile relay I ride every year where I need more gear to push the descent harder. I may just go with a 52 big ring and keep the 34. I also want to change my arm length though so more likely a new crank is in my future and as it is my TT and I don't do real steep climbs on it I may just go 53/39.

You want 53/39 with 11-28 cassette.
Same top end, and almost the same granny gear as your current setup.
Your front chain rings will shift well too.

52/36 is with 11/28 will give you a little more granny gear, but not quite the high end you want.
On a TT bike I would never go smaller than a 53, but that's me...